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JavaCard Virtual Machine Specification, Version 3.0

1. TABLE 3 1 Type Support in the Java Card Virtual Machine Instruction Set Continued jopcode yte short int reference Tstore sstore istore astore Tinc sinc iinc Taload aload saload iaload aaload Tastore astore sastore iastore aastore Tadd sadd iadd Tsub ssub isub Tmul smul imul Tdiv sdiv idiv Trem srem irem Tneg sneg ineg Tshl sshl ishl Tshr sshr ishr Tushr sushr iushr Tand sand iand Tor sor ior Txor Sxor ixor s2T 2b Is2i i2T i2b i2s Tcmp icmp if_TcmpOP if_scmpOP if_acmpOP Tlookupswitch slookupswitch ilookupswitch Ttableswitch stableswitch itableswitch Treturn sreturn ireturn areturn getstatic_T etstatic_b jgetstatic_s getstatic_i Igetstatic_ la lpputstatic_T utstatic_b jpputstatic_s joutstatic_i lpputstatic_ a getfield_T etfield_b getfield_s getfield_i Igetfield_a lpputfield_T utfield_b putfield_s putfield_i putfield_a Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The mapping between Java storage types and Java Card virtual machine computational types is summarized in TABLE 3 2 TABLE 3 2 Storage Types and Computational Types Nava Storage Type Size in Bits Computational Type byte 8 short short 16 short int 32 int Chapter 7 describes the Java Card virtual machine instruction set in detail Chapter 3 Structure of the Java Card Virtual Machine 3 7 3 8 Vi
2. astore_ lt n gt Forms astore_0 43 0x2b astore_1 44 0x2c astore_2 45 Ox2d astore_3 46 0x2e Stack objectref gt Description The lt n gt must be a valid index into the local variables of the current frame Section 3 5 Frames on page 3 3 The objectref on the top of the operand stack must be of type returnAddress or of type reference It is popped from the operand stack and the value of the local variable at lt n gt is set to objectref Notes An astore_ lt n gt instruction is used with an objectref of type returnAddress when implementing Java s finally keyword An aload_ lt n gt instruction cannot be used to load a value of type returnAddress from a local variable onto the operand stack This asymmetry with the corresponding astore_ lt n gt instruction is intentional Each of the astore_ lt n gt instructions is the same as astore with an index of lt n gt except that the operand lt n gt is implicit athrow Throw exception or error Format athrow Forms athrow 147 0x93 Stack Chapter 7 Java Card Virtual Machine Instruction Set 7 13 Dae det objectref gt objectref Description The objectref must be of type reference and must refer to an object that is an instance of class Throwable or of a subclass of Throwable It is popped from the operand stack The objectref is then thrown by searching the current frame Section 3 5 Frames on page
3. idiv 7 34 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 0 00 Forms idiv 72 0x48 Stack valuel word1 valuel word2 value2 word1 value2 word2 gt result word1 result word2 Description Both valuel and value2 must be of type int The values are popped from the operand stack The int result is the value of the Java expression valuel value2 The result is pushed onto the operand stack An int division rounds towards 0 that is the quotient produced for int values in n d is an int value q whose magnitude is as large as possible while satisfying d q lt n Moreover q is a positive when n gt d and n and d have the same sign but q is negative when n gt d and n and d have opposite signs There is one special case that does not satisfy this rule if the dividend is the negative integer of the largest possible magnitude for the int type and the divisor is 1 then overflow occurs and the result is equal to the dividend Despite the overflow no exception is thrown in this case Runtime Exception If the value of the divisor in an int division is 0 idiv throws an ArithmeticException Notes If a virtual machine does not support the int data type the idiv instruction will not be available 1f_acmp lt cond gt Branch if reference comparison succeeds Format if_acmp lt cond gt branch Forms if_acmpeq 104 0x68
4. 7 5 56 at index must be of type CONSTANT_StaticMethodref Section 6 7 3 CONSTANT_StaticFieldref and CONSTANT_StaticMethodref on page 6 20 a reference to a statically linked instance method If the invoked method is a superclass method the constant pool item at index must be of type CONSTANT_SuperMethodref Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT_VirtualMethodref and CONSTANT_SuperMethodref on page 6 18 a reference to an instance method of a specified class The reference is resolved The resolved method must not be lt clinit gt a class or interface initialization method If the method is lt init gt an instance initialization method then the method must only be invoked once on an uninitialized object and before the first backward branch following the execution of the new instruction that allocated the object Finally if the resolved method is protected and it is a member of a superclass of the current class and the method is not declared in the same package as the current class then the class of objectref must be either the current class or a subclass of the current class The resolved method includes the code for the method an unsigned byte nargs that must not be zero and the method s modifier information The objectref must be of type reference and must be followed on the operand stack by nargs 1 words of arguments where the number of words of arguments and the type and order of the values the
5. Virtual Methods on page 4 9 of the implementations of the interface methods The virtual method token values are defined within the scope of the hierarchy of this class remote_interface_info If the value of the ACC_REMOTE flag is zero this structure is defined as remote_interface_info If the value of the ACC_REMOTE flag is one this structure is defined as remote_interface_info ul remote_methods_count remote_method_info remote_methods remote_methods_count ul hash_modifier_length ul hash_modifier hash_modifier_length ul class_name_length ul class_name class_name_length ul remote_interfaces_count class_ref remote_interfaces remote_interfaces_count The remote_interface_info structure is defined as remote_methods_count The remote_methods_count item indicates the number of entries in the remote_methods array remote_methods The remote_methods item of the class_info structure is an array of remote_method_info structures that maps each remote method available in the class to its hash code and its type definition in the signature_pool The methods are listed in numerically ascending order of hash values The remote_method_info structure is defined as follows 6 34 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 remote_method_info u2 remote_method_hash u2 signature_offset ul virtual_method_token The items in the remote_method_info structure a
6. result word1 result word2 The Virtual Machine Specification does not mandate how the two words are used to represent the 32 bit int value it only requires that a particular implementation be internally consistent aaload Load reference from array Format aaload Forms aaload 36 0x24 Stack arrayref index gt value Chapter 7 Java Card Virtual Machine Instruction Set 7 5 7 Oe 7 6 Description The arrayref must be of type reference and must refer to an array whose components are of type reference The index must be of type short Both arrayref and index are popped from the operand stack The reference value in the component of the array at index is retrieved and pushed onto the top of the operand stack Runtime Exceptions If arrayref is null aaload throws a NullPointerException Otherwise if index is not within the bounds of the array referenced by arrayref the aaload instruction throws an ArrayIndexOutOfBoundsException Notes In some circumstances the aaload instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the array referenced by arrayref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 aastore Store into reference array Format aastore
7. will not be called automatically by the Java Card virtual machine Threads The Java Card virtual machine does not support multiple threads of control Programs for the Java Card platform Java Card programs cannot use class Thread or any of the thread related keywords in the Java programming language Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Cloning The Java Card platform does not support cloning of objects Java Card API class Object does not implement a clone method and there is no Cloneabl1e interface provided Access Control in Java Packages The Java Card platform language subset supports the package access control defined in the Java language However the cases that are not supported are as follows a Ifa class implements a method with package access visibility a subclass cannot override the method and change the access visibility of the method to protected or public a A public class cannot contain a public or protected field of type reference to a package visible class a A public class cannot contain a public or protected method with a return type of type reference to a package visible class a A public or protected method in a public class cannot contain a formal parameter of type reference to a package visible class a A package visible class that is extended by a public class cannot define any public or protected methods or fields m A package visible interfa
8. Sun is not responsible for the availability of third party web sites mentioned in this document Sun does not endorse and is not responsible or liable for any content advertising products or other materials that are available on or through such sites or resources Sun will not be responsible or liable for any actual or alleged damage or loss caused by or in connection with the use of or reliance on any such content goods or services that are available on or through such sites or resources xxii Sun Welcomes Your Comments Sun Microsystems is interested in improving its documentation and welcomes your comments and suggestions You can submit your comments to jc bandol spec feedback sun com Please include the title of your document with your feedback Virtual Machine Specification Java Card Platform v3 0 Classic Edition Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 CHAPTER 1 Introduction This book is targeted for the Classic Edition The Java Card Platform Version 3 0 consists of two editions m The Classic Edition is based on an evolution of the Java Card Platform Version 2 2 2 and is backward compatible with it targeting resource constrained devices that solely support applet based applications You may disregard the specifications for the Connected Edition if you are interested in the functionality found only in the Classic Edition m The Connected Edition features a s
9. This section describes the optional features of the Java Card platform An optional feature is not required to be supported in a Java Card platform compatible implementation However if an implementation does include support for an optional feature it must be supported fully and exactly as specified in this document Integer Data Type The int keyword and 32 bit integer data type need not be supported in a Java Card implementation A Java Card virtual machine that does not support the int data type will reject programs which use the int data type or 32 bit intermediate values The result of an arithmetic expression produced by a Java Card virtual machine must be equal to the result produced by a Java virtual machine regardless of the input values A Java Card virtual machine that does not support the int data type must reject expressions that could produce a different result Object Deletion Mechanism Java Card technology version 3 0 offers an optional object deletion mechanism Applications designed to run on these implementations can use the facility by invoking the appropriate API See Application Programming Interface Java Card Platform Version 3 0 But the facility is best suited for updating large objects such as certificates and keys atomically Therefore application programmers should conserve on the allocation of objects Limitations of the Java Card Virtual Machine The limitations of resource constrained hardware preven
10. invokespecial invokestatic invokevirtual ior 7 58 irem 7 58 ireturn 7 59 ishl 7 60 7 61 7 61 ishr istore istore_ lt n gt 7 62 isub 7 63 itableswitch 7 63 x Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 67 7 5 68 7 5 69 7 5 70 7 9 71 7 5 72 7 5 73 7 5 74 7 5 79 7 5 76 Vow 7 5 78 7 5 79 7 5 80 7 5 81 7 5 82 7 5 83 7 5 84 7 5 85 7 5 86 7 5 87 7 5 88 7 5 89 7 5 90 7 5 91 7 5 92 7 5 93 7 5 94 iushr 7 65 ixor 7 65 jsr 7 66 new 7 67 newarray 7 68 nop 7 69 pop 7 69 pop2 7 70 putfield_ lt t gt 7 70 putfield_ lt t gt _this 7 72 putfield_ lt t gt _w 7 74 putstatic_ lt t gt 7 75 ret 7 77 return 7 78 s2b 7 78 s2i 7 79 sadd 7 79 saload 7 80 sand 7 81 sastore 7 81 sconst_ lt s gt 7 82 sdiv 7 83 sinc 7 83 sinc_w 7 84 sipush 7 85 load 7 85 n load_ lt n gt 7 86 n lookupswitch 7 87 n Contents xi 7 5 95 7 5 96 7 5 97 7 5 98 7 5 99 7 5 100 7 5 101 7 5 102 7 5 103 7 5 104 7 5 105 7 5 106 7 5 107 7 5 108 7 5 109 8 Tables of Instructions smul 7 88 sneg 7 88 sor 7 89 srem 7 90 sreturn 7 90 sshl 7 91 sshr 7 92 sspush 7 93 sstore 7 93 sstore_ lt n gt 7 94 ssub 7 94 stableswitch 7 95 sushr 7 96 swap_x 7 97 sxor 7 98 8 1 Glossary Glossary 1 Index Index 1 xii Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 FIGURE 1 1 FIGURE
11. Format ifnull branch Forms ifnull 102 0x66 Stack Value gt Description 7 42 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 44 7 5 45 The value must be of type reference It is popped from the operand stack If the value is null branch is used as signed 8 bit offset and execution proceeds at that offset from the address of the opcode of this ifnull instruction The target address must be that of an opcode of an instruction within the method that contains this ifnull instruction Otherwise execution proceeds at the address of the instruction following this ifnull instruction ifnull_w Branch if reference is null wide index Format ifnull_w branchbyte1 branchbyte2 Forms ifnull_w 158 0x9e Stack Value gt Description The value must be of type reference It is popped from the operand stack If the value is null the unsigned bytes branchbytel and branchbyte2 are used to construct a signed 16 bit branchoffset where branchoffset is branchbytel lt lt 8 branchbyte2 Execution proceeds at that offset from the address of the opcode of this ifnull_w instruction The target address must be that of an opcode of an instruction within the method that contains this ifnull_w instruction Otherwise execution proceeds at the address of the instruction following this ifnull_w instruction iiinc Increment local int variab
12. Forms goto_w 168 0xa8 Stack No change Description The unsigned bytes branchbyte1 and branchbyte2 are used to construct a signed 16 bit branchoffset where branchoffset is branchbyte1 lt lt 8 branchbyte2 Execution proceeds at that offset from the address of the opcode of this goto instruction The target address must be that of an opcode of an instruction within the method that contains this goto instruction 7 28 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 26 i2b Convert int to byte Format i2b Forms i2b 93 0x5d Stack value word1 value word2 gt result Description The value on top of the operand stack must be of type int It is popped from the operand stack and converted to a byte result by taking the low order 16 bits of the int value and discarding the high order 16 bits The low order word is truncated to a byte then sign extended to a short result The result is pushed onto the operand stack Notes The i2b instruction performs a narrowing primitive conversion It may lose information about the overall magnitude of value The result may also not have the same sign as value If a virtual machine does not support the int data type the i2b instruction will not be available Teco 128 Convert int to short Format 12s Forms i2s 94 0x5e Stack Chapter 7 Java Card Virtual Machine Instruction Set 7 29 va
13. Forms aastore 55 0x37 Stack arrayref index value gt Description The arrayref must be of type reference and must refer to an array whose components are of type reference The index must be of type short and the value must be of type reference The arrayref index and value are popped from the operand stack The reference value is stored as the component of the array at index Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 At runtime the type of value must be confirmed to be assignment compatible with the type of the components of the array referenced by arrayref Assignment of a value of reference type S source to a variable of reference type T target is allowed only when the type S supports all of the operations defined on type T The detailed rules follow m IfS isa class type then a If Tis a class type then S must be the same class as T or S must be a subclass of T a If Tis an interface type then S must implement interface T m If Sis an interface type then a If T is a class type then T must be Object Section 2 2 2 4 Classes on page 2 7 a If Tis an interface type T must be the same interface as S or a superinterface of S m IfSis an array type namely the type SC that is an array of components of type SC then a If Tis a class type then T must be Object a If Tis an array type namely the type TC an array of components of type TC th
14. Type checking and the instanceof operator also work correctly with interfaces Exceptions Java Card programs may define throw and catch exceptions as in Java programs Class Throwable and its relevant subclasses are supported Some Exception and Error subclasses are omitted since those exceptions cannot occur in the Java Card platform See Section 2 3 3 Exceptions on page 2 19 for specification of errors and exceptions Generics This Java language facility allows a type or method to operate on objects of various types while providing compile time type safety It adds compile time type safety and eliminates the need for casting Static Import This Java language facility lets you avoid importing an entire class simply to access its static members or qualifying static members with class names each time it is used Runtime Invisible Metadata Annotations This language feature lets you avoid writing boilerplate code under many circumstances by enabling tools to generate it from annotations in the source code The Java Card platform language subset supports the use of annotations which are not visible at runtime These annotations do not themselves use the runtime visible meta data annotation Retention RetentionPolicy RUNTIME 2 6 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 2 2 2 2 222 0 2 2 2 4 Keywords The following keywords are supported Their use is the same as in the
15. imul fdiv drem lshl lor i2d 2i d2f fcmpg freturn multianewarray iconst_ lt i gt ldc_w aload_ lt n gt saload astore_ lt n gt sastore ldc2_w2 lload_ lt n gt faload fstore dstore_ lt n gt castore lsub fmul ddiv ineg lshr lxor 121 2d i2c dcmp1 dreturn goto_w bipush iload iaload istore iastore pop Chapter 2 A Subset of the Java Virtual Machine 2 17 TABLE 2 6 Supported Bytecodes Continued pop2 dup dup_x1 dup_x2 dup2 dup2_x1 dup2_x2 swap iadd isub imul idiv irem ineg ior ishl ishr iushr iand ixor iinc i2b i2s if lt cond gt ificmp_ lt cond gt ifacmp_ lt cond gt goto jsr ret tableswitch lookupswitch ireturn areturn return getstatic putstatic getfield putfield invokevirtual invokespecial invokestatic invokeinterface new newarray anewarray arraylength athrow checkcast instanceof wide ifnull ifnonnull 2 9 2 9 Static Restrictions on Bytecodes A class file must conform to the following restrictions on the static form of bytecodes Idc Idc_w The 1dc and 1dc_w bytecodes can only be used to load integer constants The constant pool entry at index must be a CONSTANT_Integer entry If a program contains an 1dc or 1dc_w instruction that is used to load an integer value less than 32768 or greater than 32767 that program will require the optional int instructions Section 2 2 3 1 Integer Data Type on page 2 8 lookupswitch The value of the npairs operan
16. protected and package visible instance methods Private instance methods and all constructors are not virtual methods but instead are resolved statically during compilation Chapter 4 Binary Representation 4 9 4 3 7 7 4 10 All virtual methods defined in a package are assigned either public or private virtual method tokens Virtual method token values must be in the range from 0 to 127 inclusive Public and private tokens for virtual methods are assigned from different namespaces The high bit of the byte containing a virtual method token is set to one if the token is a private token Public tokens for the externally visible public or protected introduced virtual methods in a class are numbered consecutively starting at one greater than the highest numbered public virtual method token of the class s superclass If a method overrides a method implemented in the class s superclass that method is assigned the same token number as the method in the superclass The high bit of the byte containing a public virtual method token is always set to zero to indicate it is a public token The ordering of public virtual method tokens in a class is not specified Private virtual method tokens are assigned to package visible virtual methods They are assigned differently from public virtual method tokens If a class and its superclass are defined in the same package the tokens for the package visible introduced virtual methods in that class are nu
17. system 1 2 technology 1 1 Virtual Machine 1 2 errors 7 2 instruction set 7 1 7 3 limitations 2 8 Java programming language 2 1 unsupported features 2 2 Java Virtual Machine 2 1 2 13 javacard framework Shareable 1 5 jsr 7 66 K keywords 2 7 supported 2 7 unsupported 2 4 L ldc 2 18 ldc_w 2 18 library package 1 4 Glossary 6 LinkageError 2 21 linking 4 5 4 13 local variable Glossary 6 logical channel Glossary 6 long 2 4 lookupswitch 2 18 M MAC Glossary 6 mask production Glossary 6 masking Glossary 6 memory non volatile in smart cards 2 1 Message Authentication Code Glossary 6 method Glossary 6 method component of a CAP file 6 36 method descriptors 2 15 method_debug_info 6 65 method_descriptor_info 6 56 method_info 6 40 methods 2 10 2 14 2 16 static 2 10 virtual 2 6 4 9 mnemonic 7 4 multiselectable applets 2 12 Glossary 7 multiselected applet Glossary 7 must or must not the meaning of 7 1 N namespace Glossary 7 naming 4 3 native 2 4 native method 3 2 Glossary 7 NegativeArraySizeException 2 21 new 2 7 7 67 newarray 7 68 nibble Glossary 7 NoClassDefFoundError 2 22 nop 7 69 NoSuchFieldError 2 22 NoSuchFieldException 2 20 NoSuchMethodError 2 22 NoSuchMethodException 2 20 NullPointerException 2 21 NumberFormatException 2 21 numeric types 3 1 O object 2 7 object owner Glossary 7 object oriented Glos
18. there is an opportunity for better support for smaller data types Lack of support for large numeric data types frees up space in the instruction set This extra instruction space has been used to directly support arithmetic operations on the short data type Some of the extra instruction space has also been used to optimize common operations Type information is directly encoded in field access instructions rather than being obtained from an entry in the constant pool TABLE 3 1 summarizes the type support in the instruction set of the Java Card virtual machine Only instructions that exist for multiple types are listed Wide and composite forms of instructions are not listed either A specific instruction with type information is built by replacing the T in the instruction template in the opcode column by the letter representing the type in the type column If the type column for some instruction is blank then no instruction exists supporting that operation on that type For instance there is a load instruction for type short sload but there is no load instruction for type byte TABLE 3 1 Type Support in the Java Card Virtual Machine Instruction Set jopcode yte short int reference Tspush spush sspush Tipush ipush sipush iipush ITceonst Isconst iconst aconst Tload sload iload laload Chapter 3 Structure of the Java Card Virtual Machine 3 5 3 6
19. 1 to represent true and 0 to represent false Reference Location Component The Reference Location Component represents lists of offsets into the info item of the Method Component Section 6 9 Method Component on page 6 36 to items that contain indices into the constant_pool array of the Constant Pool Component Section 6 7 Constant Pool Component on page 6 14 This includes all constant pool index operands of instructions and all non zero catch_type_index items of the exception_handlers array The catch_type_index items that have the value of 0 are not included since they represent finally blocks instead of particular exception classes Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Some of the constant pool indices are represented in one byte values while others are represented in two byte values Operands of getfield_T and putfield_T instructions are one byte constant pool indices All other indices in a Method Component are two byte values The Reference Location Component is not referenced by any other component in this CAP file The Reference Location Component structure is defined as reference_location_component ul tag u2 size u2 byte_index_count ul offsets_to_byte_indices byte_index_count u2 byte2_index_count ul offsets_to_byte2_indices byte2_index_count The items of the reference_location_component structure are as follows tag The tag item has t
20. 12 aconst_null 7 8 active applet instance Glossary 1 AID Glossary 1 aload 7 8 aload_ lt n gt 7 9 anewarray 7 10 Answer to Reset Glossary 2 APDU Glossary 1 instructions 8 1 API Glossary 1 applet Preface xvii 1 1 1 3 Glossary 1 currently selected Glossary 3 default Glossary 3 developer Glossary 1 execution context Glossary 1 firewal Glossary 1 mulitselectable 2 12 multiselected Glossary 7 package Glossary 1 applet component of a CAP file 6 12 applet firewall 1 5 applets multiselectable Glossary 7 application identifier Glossary 1 application identifier AID 4 3 Application Programming Interface Glossary 1 areturn 7 10 ArithmeticException 2 21 ArrayIndexOutOfBoundsException 2 21 arraylength 7 11 arrays 2 7 2 10 5 1 arrays in CAP files 6 1 ArrayStoreException 2 21 assigned logical channel Glossary 1 astore 7 12 astore_ lt n gt 7 12 athrow 7 13 atomic operation Glossary 2 atomicity Glossary 2 ATR Glossary 2 attributes 2 16 ConstantValue 5 16 B baload 7 14 basic logical channel Glossary 2 bastore 7 15 big endian 3 4 Glossary 2 binary compatibility 4 11 Glossary 2 binary file formats 3 4 binary portability 1 2 Index 1 binary representation of Java Card programs 4 1 bipush 7 16 bitfield structures in CAP files 6 1 boolean 2 7 boolean types 3 1 break 2 7 bspush 7 16 byte 2 7 3 1 bytecode 2 16 Glossary 2
21. 3 3 for the most recent catch clause that catches the class of objectref or one of its superclasses If a catch clause is found it contains the location of the code intended to handle this exception The pc register is reset to that location the operand stack of the current frame is cleared objectref is pushed back onto the operand stack and execution continues If no appropriate clause is found in the current frame that frame is popped the frame of its invoker is reinstated and the objectref is rethrown If no catch clause is found that handles this exception the virtual machine exits Runtime Exception If objectref is null athrow throws a NullPointerException instead of objectref Notes In some circumstances the athrow instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 baload Load byte or boolean from array Format baload Forms baload 37 0x25 Stack arrayref index gt Value 7 14 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 013 Description The arrayref must be of type reference and must refer to an array whose components are of
22. 9C 157 9D 158 9E 159 9F 160 AO 161 A1 162 A2 163 A3 164 A4 165 A5 166 A6 167 AT 168 A8 169 Ag 170 AA 171 AB Instructions by Opcode Value Continued mnemonic invokeinterface new newarray anewarray arraylength athrow checkcast instanceof sinc_w iinc_w ifeq_w ifne_w iflt_w ifge_w ifgt_w ifle_w ifnull_w ifnonnull_w if_acmpeq_w if_acmpne_w if_scmpeq_w if_scmpne_w if_scmplt_w if_scmpge_w if_scmpgt_w if_scmple_w goto_w getfield_a_w getfield_b_w getfield_s_w Chapter 8 Tables of Instructions 8 3 TABLE 8 1 Instructions by Opcode Value Continued dec hex mnemonic dec hex mnemonic 125 JD getstatic_s 172 AC getfield_i_w 126 TE getstatic_i 173 AD getfield_a_this 127 7F putstatic_a 174 AE getfield_b_this 128 80 putstatic_b 175 AF getfield_s_ this 129 81 putstatic_s 176 BO getfield_i_this 130 82 putstatic_i 177 B1 putfield_a_w 131 83 getfield_a 178 B2 putfield_b_w 132 84 getfield_b 179 B3 putfield_s_w 133 85 getfield_s 180 B4 putfield_i_w 134 86 getfield_i 181 B5 putfield_a_this 135 87 putfield_a 182 B6 putfield_b_this 136 88 putfield_b 183 B7 putfield_s_this 137 89 putfield_s 184 B8 putfield_i_this 138 8A putfield_i 139 8B invokevirtual 254 FE impdep1 140 8C invokespecial 255 FF impdep2 TABLE 8 2 Instructions by Opcode Mnemonic mnemonic dec hex mnemonic dec hex aaload 36 24 iand 84 54 aastore 55 37 iastore 58 3A aconst_null 1 01 icmp 95 5F aload 21 15 iconst_0
23. A7 108 6C 164 A4 107 6B 163 A3 96 60 152 98 99 63 155 9B 100 64 156 9C 101 65 157 9D 98 62 154 9A 97 61 153 99 103 67 Chapter 8 Tables of Instructions 8 5 TABLE 8 2 Instructions by Opcode Mnemonic Continued mnemonic dec hex mnemonic dec hex getstatic_s 125 7D ifnonnull_w 159 OF goto 112 70 ifnull 102 66 goto_w 168 A8 ifnull_w 158 9E i2b 93 5D iinc 90 5A i2s 94 5E iinc_w 151 97 iadd 66 42 iipush 20 14 iaload 39 27 iload 23 17 iload_0 32 20 putstatic_s 129 81 iload_1 33 21 ret 114 72 iload_2 34 22 return 122 7A iload_3 35 23 s2b 91 5B ilookupswitch 118 76 s2i 92 5G imul 70 46 sadd 65 41 ineg 76 AC saload 38 26 instanceof 149 95 sand 83 53 invokeinterface 142 8E sastore 57 39 invokespecial 140 8C sconst_0 3 03 invokestatic 141 8D sconst_1 4 04 invokevirtual 139 8B sconst_2 5 05 ior 86 56 sconst_3 6 06 irem 74 4A sconst_4 7 07 ireturn 121 79 sconst_5 8 08 ishl 78 4E sconst_m1 2 02 ishr 80 50 sdiv 71 47 istore 42 2A sinc 89 59 istore_0 51 33 sinc_w 150 96 istore_1 52 34 sipush 19 13 istore_2 53 35 sload 22 16 istore_3 54 36 sload_0 28 1c isub 68 44 sload_1 29 1D 8 6 Virtual Machine Specification Java Card Platform v3 0 Classic Edition March 2008 TABLE 8 2 mnemonic itableswitch iushr ixor jsr new newarray nop pop pop2 pu pu pu pu tfield_a tfield_a_this tfield_a_w tfield_b tfield_b_this tfield_b_w tfield_i tfield_i_this tfield_i_w tfield_s tf
24. Card Platform v3 0 Classic Edition e March 2008 2 2 4 5 2 2 4 6 A method can have at most 32767 Java Card virtual machine bytecodes The number of Java Card technology based bytecodes Java Card bytecodes may differ from the number of Java bytecodes in the Java virtual machine implementation of that method The maximum depth of an operand stack associated with a method is 255 16 bit cells Switch Statements The format of the Java Card virtual machine switch instructions limits switch statements to a maximum of 65536 cases This limit is far greater than the limit imposed by the maximum size of methods Section 2 2 4 4 Methods on page 2 10 Class Initialization The Java Card virtual machine contains limited support for class initialization because there is no general mechanism for executing lt clinit gt methods Support for lt clinit gt methods is limited to the initialization of static field values with the following constraints m Static fields of applet packages may only be initialized to primitive compile time constant values or arrays of primitive compile time constants m Static fields of user libraries may only be initialized to primitive compile time constant values m Only static fields declared in the current class may be initialized in the lt clinit gt method Primitive constant data types include boolean byte short and int Given Java technology source files that adhere to these language l
25. It is popped from the operand stack and sign extended to an int result The result is pushed onto the operand stack Notes The s2i instruction performs a widening primitive conversion Because all values of type short are exactly representable by type int the conversion is exact If a virtual machine does not support the int data type the s2i instruction will not be available sadd Add short Format sadd Forms sadd 65 0x41 Chapter 7 Java Card Virtual Machine Instruction Set 7 79 Stack value1 value2 gt result Description Both valuel and value2 must be of type short The values are popped from the operand stack The short result is valuel value2 The result is pushed onto the operand stack If a sadd instruction overflows then the result is the low order bits of the true mathematical result in a sufficiently wide two s complement format If overflow occurs then the sign of the result may not be the same as the sign of the mathematical sum of the two values 7 5 84 saload Load short from array Format saload Forms saload 38 0x46 Stack arrayref index gt Value Description The arrayref must be of type reference and must refer to an array whose components are of type short The index must be of type short Both arrayref and index are popped from the operand stack The short value in the component of the array at index is retrieved and pushed ont
26. Java programming language TABLE 2 2 Supported Keyword abstract default TE private this boolean do implements protected throw break else import public throws byte extends instanceof return try case final int short void catch finally interface static while class for new super continue goto package switch Types Java programming language types boolean byte short and int are supported Objects class instances and single dimensional arrays are also supported Arrays can contain the supported primitive data types objects and other arrays Some Java Card implementations might not support use of the int data type Refer to Section 2 2 3 1 Integer Data Type on page 2 8 Classes Most of the classes in the java lang package are not supported on the Java Card platform The following classes from java lang are supported on the card in a limited form Object Java Card API classes descend from java lang Object just as in the Java programming language Most of the methods of Object are not available in the Java Card API but the class itself exists to provide a root for the class hierarchy Chapter 2 A Subset of the Java Virtual Machine 2 7 2 29 2 2 3 2 2 3 2 2 2 4 2 8 Throwable Class Throwable and its subclasses are supported Most of the methods of Throwable are not available in the Java Card API but the class itself exists to provide a common ancestor for all exceptions Optionally Supported Items
27. Java Card technology enabled device See Section 6 2 Installation on page 6 5 for more information The name of a JAR file containing CAP file components is not defined as part of this specification The naming convention used by the Sun Microsystems Inc Java Card Converter Tool is to append cap to the simple meaning not fully qualified package name For example the CAP file produced for the package com sun javacard JavaLoyalty would be named JavaLoyalty cap Defining New Components Java Card CAP files are permitted to contain new or custom components All new components not defined as part of this specification must not affect the semantics of the specified components and Java Card virtual machines must be able to accept CAP files that do not contain new components Java Card virtual machine implementations are required to silently ignore components they do not recognize New components are identified in two ways they are assigned both an ISO 7816 5 AID Section 4 2 AID based Naming on page 4 3 and a tag value Valid tag values are between 128 and 255 inclusive Both of these identifiers are recorded in the custom_component item of the Directory Component Section 6 4 Directory Component on page 6 9 The new component must conform to the general component format defined in this chapter with a tag value a size value indicating the number of bytes in the component excluding the tag and size items and an in
28. address of the opcode of this if_scmp lt cond gt instruction The target address must be that of an opcode of an instruction within the method that contains this if_scmp lt cond gt instruction Otherwise execution proceeds at the address of the instruction following this if_scmp lt cond gt instruction 7 5 38 if_scmp lt cond gt _w Branch if short comparison succeeds wide index Format if_scmp lt cond gt _w branchbyte1 branchbyte2 Forms if_scmpeq_w 162 0xa2 if_scmpne_w 163 0xa3 if_scmplt_w 164 Oxa4 if_scmpge_w 165 0xa5 if_scmpgt_w 166 0xa6 if_scmple_w 167 0xa7 Stack value1 value2 gt Description Both valuel and value2 must be of type short They are both popped from the operand stack and compared All comparisons are signed The results of the comparisons are as follows m eq succeeds if and only if valuel value2 m ne succeeds if and only if valuel 1 4 value2 m It succeeds if and only if valuel lt value2 m le succeeds if and only if valuel value2 m gt succeeds if and only if valuel gt value2 m ge succeeds if and only if valuel value2 7 38 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 715 09 If the comparison succeeds the unsigned bytes branchbytel and branchbyte2 are used to construct a signed 16 bit branchoffset where branchoffset is branchbytel lt lt 8 branchbyte2 Execution proceeds at that off
29. amp SUN microsystems Virtual Machine Specification Java Card Platform Version 3 0 Classic Edition Sun Microsystems Inc www sun com March 2008 Copyright 2008 Sun Microsystems Inc 4150 Network Circle Santa Clara California 95054 U S A All rights reserved Sun Microsystems Inc has intellectual property rights relating to technology embodied in the product that is described in this document In particular and without limitation these intellectual property rights may include one or more of the U S patents listed at ttp www sun com patents and one or more additional patents or pending patent applications in the U S and in other countries U S Government Rights Commercial software Government users are subject to the Sun Microsystems Inc standard license agreement and applicable provisions of the FAR and its supplements Use is subject to license terms This distribution may include materials developed by third parties Parts of the product may be derived from Berkeley BSD systems licensed from the University of California Sun Sun Microsystems the Sun logo Solaris Java Java Card JDK Servlet and JVM are trademarks or registered trademarks of Sun Microsystems Inc in the U S and other countries UNIX is a registered trademark in the U S and other countries exclusively licensed through X Open Company Ltd The Adobe logo is a registered trademark of Adobe Systems Incorporated Products co
30. and the high bit of the structure is zero If the class or interface is defined in another package the structure represents an external_class_ref and the high bit of the structure is one internal_class_ref The internal_class_ref structure represents a 16 bit offset into the info item of the Class Component Section 6 8 Class Component on page 6 22 to an interface_info or class_info structure The interface_info or class_info structure must represent the referenced class or interface The value of the internal_class_ref item must be between 0 and 32767 inclusive making the high bit equal to zero external_class_ref Chapter6 The CAP File Format 6 17 The external_class_ref structure represents a reference to a class or interface defined in an imported package The high bit of this structure is one package_token The package_token item represents a package token Section 4 3 7 1 Package on page 4 8 defined in the Import Component Section 6 6 Import Component on page 6 13 of this CAP file The value of this token must be a valid index into the packages table item of the import_component structure The package represented at that index must be the imported package The value of the package token must be between 0 and 127 inclusive The high bit of the package_token item is equal to one class_token The class_token item represents the token of the class or interface Section 4 3 7 2 Classes and Int
31. can occur in any order export_fields_count The value of the export_fields_count item gives the number of entries in the fields table Chapter5 The Export File Format 5 11 fields Each value in the fields table is a variable length field_info Section 5 8 Fields on page 5 12 structure The ield_info contains an entry for each publicly accessible field both class variables and instance variables declared by this class or interface It does not include items representing fields that are inherited from superclasses or superinterfaces export_methods_count The value of the export_methods_count item gives the number of entries in the methods table methods Each value in the methods table is a method_info Section 5 9 Methods on page 5 14 structure The method_info structure contains an entry for each publicly accessible class static or constructor method defined by this class and each publicly accessible instance method defined by this class or its superclasses or defined by this interface or its super interfaces 5 8 Fields Each field is described by a variable length ield_info structure The format of this structure is field_info ul token u2 access_flags u2 name_index u2 descriptor_index u2 attributes_count attribute_info attributes attributes_count The items of the field_info structure are as follows token The token item is the token assigned to this field There a
32. from the operand stack The short result is the value of the Java expression valuel value2 The result is pushed onto the operand stack A short division rounds towards 0 that is the quotient produced for short values in n d is a short value q whose magnitude is as large as possible while satisfying d q lt n Moreover q is a positive when n gt d and n and d have the same sign but q is negative when n gt d and n and d have opposite signs There is one special case that does not satisfy this rule if the dividend is the negative integer of the largest possible magnitude for the short type and the divisor is 1 then overflow occurs and the result is equal to the dividend Despite the overflow no exception is thrown in this case Runtime Exception If the value of the divisor in a short division is 0 sdiv throws an ArithmeticException sinc Increment local short variable by constant Chapter 7 Java Card Virtual Machine Instruction Set 7 83 Format sinc index const Forms sinc 89 0x59 Stack No change Description The index is an unsigned byte that must be a valid index into the local variable of the current frame Section 3 5 Frames on page 3 3 The const is an immediate signed byte The local variable at index must contain a short The value const is first sign extended to a short then the local variable at index is incremented by that amount 7 5 90 si
33. functionality Keywords The following keywords indicate unsupported options related to native methods threads floating point memory management and debugging TABLE 2 1 Unsupported Keywords native synchronized transient volatile strictfp enum assert Unsupported Types The Java Card platform does not support types char double float and long It also does not support arrays of more than one dimension Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 2 2 1 4 2d 2 2 2 1 Classes In general none of the Java programming language core API classes are supported in the Java Card platform Some classes from the java lang package are supported see Section 2 2 2 4 Classes on page 2 7 but none of the rest are For example classes that are not supported are String Thread and all thread related classes wrapper classes such as Boolean and Integer and class Class System Class java lang System is not supported Java Card technology supplies a class javacard framework JCSystem which provides an interface to system behavior Supported Items If a language feature is not explicitly described as unsupported it is part of the supported subset Notable supported features are described in this section Features Packages Software written for the Java Card platform follows the standard rules for the Java platform packages Java Card API classes are written as Java source f
34. if_acmpne 105 0x69 Chapter 7 Java Card Virtual Machine Instruction Set 7 35 Stack valuel value2 gt Description Both valuel and value2 must be of type reference They are both popped from the operand stack and compared The results of the comparisons are as follows m eq succeeds if and only if valuel value2 m ne succeeds if and only if valuel 1 4 value2 If the comparison succeeds branch is used as signed 8 bit offset and execution proceeds at that offset from the address of the opcode of this if_acmp lt cond gt instruction The target address must be that of an opcode of an instruction within the method that contains this if_acmp lt cond gt instruction Otherwise execution proceeds at the address of the instruction following this if_acmp lt cond gt instruction 7 5 36 if _acmp lt cond gt _w Branch if reference comparison succeeds wide index Format if_acmp lt cond gt _w branchbyte1 branchbyte2 Forms if_acmpeq_w 160 Oxa0 if_acmpne_w 161 0xa1 Stack valuel value2 gt Description Both valuel and value2 must be of type reference They are both popped from the operand stack and compared The results of the comparisons are as follows m eq succeeds if and only if valuel value2 m ne succeeds if and only if valuel 1 4 value2 7 36 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 3 07 If the comparison succeeds
35. ignoring the type of data it contains 7 5 75 putfield_ lt t gt Set field in object 7 70 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Format putfield_ lt t gt index Forms putfield_a 135 0x87 putfield_b 136 0x88 putfield_s 137 0x89 putfield_i 138 0x8a Stack objectref value gt OR objectref value word1 value word2 gt Description The unsigned index is used as an index into the constant pool of the current package Section 3 5 Frames on page 3 3 The constant pool item at the index must be of type CONSTANT_InstanceFieldref Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT_VirtualMethodref and CONSTANT_SuperMethodre on page 6 18 a reference to a class and a field token The class of objectref must not be an array If the field is protected and it is a member of a superclass of the current class and the field is not declared in the same package as the current class then the class of objectref must be either the current class or a subclass of the current class If the field is final it must be declared in the current class The item must resolve to a field with a type that matches t as follows m a field must be of type reference a b field must be of type byte or type boolean m s field must be of type short m i field must be of type int value must be of a type that is assignment compatible with the fiel
36. in the applet_component structure excluding the tag and size items The value of the size item must be greater than zero count The count item indicates the number of applets defined in this package The value of the count item must be greater than zero 2 Restrictions placed on an applet definition are imposed by the Runtime Environment Specification Java Card Platform Version 3 0 6 12 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 applets The applets item represents a table of variable length structures each describing an applet defined in this package The items in each entry of the applets table are defined as follows AID_length The AID_length item represents the number of bytes in the AID item Valid values are between 5 and 16 inclusive AID The AID item represents the Java Card platform name of the applet Each applet is assigned an AID conforming to the ISO 7816 5 standard Section 4 2 AID based Naming on page 4 3 The RID first 5 bytes of all of the applet AIDs must have the same value In addition the RID of each applet AIDs must have the same value as the RID of the package defined in this CAP file install_method_offset The value of the install_method_offset item must be a 16 bit offset into the info item of the Method Component Section 6 9 Method Component on page 6 36 The item at that offset must be a method_info structure that represen
37. instance method The local variable at index 0 must contain a reference objectref to the currently executing method s this parameter The unsigned index is used as an index into the constant pool of the current package Section 3 5 Frames on page 3 3 The constant pool item at the index must be of type CONSTANT_InstanceFieldref Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT_VirtualMethodref and CONSTANT_SuperMethodref on page 6 18 a reference to a class and a field token The class of objectref must not be an array If the field is protected and it is a member of a superclass of the current class and the field is not declared in the same package as the current class then the class of objectref must be either the current class or a subclass of the current class The item must resolve to a field with a type that matches t as follows m a field must be of type reference a b field must be of type byte or type boolean s field must be of type short a i field must be of type int The width of a field in a class instance is determined by the field type specified in the instruction The item is resolved determining the field offset The value at that offset into the class instance referenced by objectref is fetched If the value is of type byte or type boolean it is sign extended to a short The value is pushed onto the operand stack Runtime Exception If objectref is null the getfield_ lt t gt _this instruction thr
38. length representation of the anti collision string in UTF 8 format class_name_length The class_name_length item is the number of bytes used in the class_name item Chapter6 The CAP File Format 6 35 class_name The class_name item is a variable length representation of the name of this class in UTF 8 format remote_interfaces_count The remote_interfaces_count item is the number of interfaces listed in the following remote_interfaces item remote_interfaces The remote_interfaces item is a variable length array of class_ref items It represents the remote interfaces implemented by this class The remote interfaces listed in this array together with their superinterfaces must be the complete set of remote interfaces implemented by this class and all its superclasses Each entry has the form of a class_ref structure Each class_ref structure must reference an interface_info structure representing a remote interface implemented by this class The entries in the remote_interfaces array must be ordered such that all remote interfaces from the same package are listed consecutively 6 9 Method Component The Method Component describes each of the methods declared in this package excluding lt clinit gt methods and interface method declarations Abstract methods defined by classes not interfaces are included The exception handlers associated with each method are also described The Method Component does not c
39. offsets into the static field image not the Static Field Component Final static fields of primitive types are not represented in the static field image Instead these compile time constants must be placed in line in Java Card technology based instructions Java Card instructions 6 42 6 Unlike in Java Card cap files in Java class files the max_locals item includes both the local variables declared by the method and the parameters passed to the method Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The Static Field Component includes all information required to initialize classes In the Java virtual machine a class is initialized by executing its lt clinit gt method In the Java Card virtual machine the functionality of lt clinit gt methods is represented in the Static Field Component as array initialization data and non default values of primitive types data Section 2 2 4 6 Class Initialization on page 2 11 contains a description of the subset of lt clinit gt functionality supported in the Java Card virtual machine The Static Field Component does not reference any other component in this CAP file The Constant Pool Component Section 6 7 Constant Pool Component on page 6 14 Export Component Section 6 12 Export Component on page 6 49 Descriptor Component Section 6 13 Descriptor Component on page 6 51 and Debug Component Section 6 14 Debug C
40. on page 4 8 to describe references to classes methods and fields defined in imported packages Entries in the Constant Pool Component do not reference other entries internal to itself The Constant Pool Component is described by the following structure constant_pool_component ul tag u2 size u2 count cp_info constant_pool count The items in the constant_pool_component structure are as follows tag The tag item has the value COMPONENT_ConstantPool 5 size The size item indicates the number of bytes in the constant_pool_component structure excluding the tag and size items The value of the size item must be greater than zero count The count item represents the number entries in the constant_pool array Valid values are between 0 and 65535 inclusive constant_pool The constant_pool item represents an array of cp_info structures cp_info ul tag ul info 3 Chapter6 The CAP File Format 6 15 Each item in the constant_pool array is a 4 byte structure Each structure must begin with a 1 byte tag indicating the kind of cp_info entry The content and format of the 3 byte info array varies with the value of the tag The valid tags and their values are listed in the following table TABLE 6 5 CAP File Constant Pool Tags Constant Type Tag CONSTANT_Classref 1 ICONSTANT_InstanceFieldref 2 CONSTANT_VirtualMethodref 3 CONSTANT_SuperMethodref 4 CONST
41. or card removal an acronym for Answer to Reset An ATR is a string of bytes sent by the Java Card platform after a reset condition logical channel 0 the only channel that is active at card reset This channel is permanent and can never be closed a technique of storing multibyte data where the high order bytes come first For example given an 8 bit data item stored in big endian order the first bit read is considered the high bit in a Java Card system a change in a Java programming language package results in a new CAP file A new CAP file is binary compatible with equivalently does not break compatibility with a preexisting CAP file if another CAP file converted using the export file of the preexisting CAP file can link with the new CAP file without errors machine independent code generated by the compiler and executed by the Java virtual machine an acronym for Card Acceptance Device The CAD is the device in which the card is inserted the CAP file is produced by the Converter and is the standard file format for the binary compatibility of the Java Card platform A CAP file contains an executable binary representation of the classes of a Java programming language package The CAP file also contains the CAP file components see also CAP file component The CAP files produced by the converter are contained in Java Archive JAR files a Java Card platform CAP file consists of a set of components which represent a Java p
42. page 6 42 It is the total number of bytes in all of the arrays initialized in all of the lt clinit gt methods in this package 6 10 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 import_count The import_count item indicates the number of packages imported by classes and interfaces in this package This item has the same value as the count item in the Import Component Section 6 6 Import Component on page 6 13 applet_count The applet_count item indicates the number of applets defined in this package If an Applet Component Section 6 5 Applet Component on page 6 12 is not included in this CAP file the value of the applet_count item is zero Otherwise the value of the applet_count item is the same as the value of the count item in the Applet Component Section 6 5 Applet Component on page 6 12 custom_count The custom_count item indicates the number of entries in the custom_components table Valid values are between 0 and 127 inclusive custom_components The custom_components item is a table of variable length custom_component_info structures Each new component defined in this CAP file must be represented in the table These components are not defined in this standard The custom_component_info structure is defined as custom_component_info ul component_tag u2 size ul AID_length ul AID AID_length The items in entries of the custom_component_info
43. qualified name of the method for example LookupAID descriptor_index Contains an index into the strings_table item of the debug_component structure The strings_table entry at the indexed location must be the argument and return types of the method meaning the signature without the method name Class types are fully qualified for example BSB Ljavacard framework AID access flags A two byte mask of modifiers that apply to this method TABLE 6 24 Method Modifier Flags Modifier Value IAACC_PUBLIC Ox0001 IACC_PRIVATE 0x0002 ACC_PROTECTED 0x0004 ACC_STATIC 0x0008 ACC_FINAL 0x0010 ACC_NATIVE 0x0100 ACC_ABSTRACT 0x0400 The ACC_NATIVE flag is only valid for methods of a package located in the card mask It cannot be used for methods contained in a CAP file All other method access and modifier flags are defined in the same way and with the same restrictions as described in The Java Virtual Machine Specification location A byte offset of the method_info structure for this method into the info item of the Method Component Section 6 9 Method Component on page 6 36 Abstract methods have a location of zero header_size The size in bytes of the header of the method Abstract methods have a header_size of zero body_size 6 66 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The size in bytes of the body of
44. scope of a set of instance field tokens is limited to the class that declares the instance fields not including the fields declared by superclasses of that class Instance field token values must be in the range from 0 to 255 inclusive Public and private tokens for instance fields are assigned from the same namespace The tokens for all the instance fields in a class are numbered consecutively starting at zero except that the token after an int field is skipped and the token for the following field is numbered two greater than the token of the int field Within a class tokens for externally visible fields must be numbered less than the tokens for package and private fields For public tokens the tokens for reference type fields must be numbered greater than the tokens for primitive type fields For private tokens the tokens for reference type fields must be numbered less than the tokens for primitive type fields Beyond that the ordering of instance field tokens in a class is not specified TABLE 4 3 Tokens For Instance Fields Visibility Category Type Token Value primitive boolean 0 public and b A protected fields yte public tokens short 2 reference lbyte 3 Applet 4 reference short 5 package and 7 z A Object 6 private fields private tokens primitive int 7 short 9 Virtual Methods Virtual methods are instance methods that are resolved dynamically The set includes all public
45. structure are component_tag The component_tag item represents the tag of the component Valid values are between 128 and 255 inclusive size The size item represents the number of bytes in the component excluding the tag and size items AID_length The AID_length item represents the number of bytes in the AID item Valid values are between 5 and 16 inclusive AID Chapter6 The CAP File Format 6 11 The AID item represents the Java Card platform name of the component See ISO 7816 5 for the definition of an AID Section 4 1 Java Card Platform File Formats on page 4 1 Each component is assigned an AID conforming to the ISO 7816 5 standard Beyond that there are no constraints on the value of an AID of a custom component 6 5 Applet Component The Applet Component contains an entry for each of the applets defined in this package Applets are defined by implementing a non abstract subclass direct or indirect of the javacard framework Applet class If no applets are defined this component must not be present in this CAP file The Applet Component is described by the following variable length structure applet_component ul tag u2 size ul count ul AID_length ul AID AID_length u2 install_method_offset applets count The items in the applet_component structure are as follows tag The tag item has the value COMPONENT_Applet 3 size The size item indicates the number of bytes
46. switch Afterwards the invoked method s context becomes the current context When the invoked method returns the current context is switched back to the previous context 3 5 Frames Java Card virtual machine frames are very similar to those defined for the Java virtual machine Each frame has a set of local variables and an operand stack Frames also contain a reference to a constant pool but since all constant pools for all classes in a package are merged the reference is to the constant pool for the current class package Each frame also includes a reference to the context in which the current method is executing 3 6 Representation of Objects The Java Card virtual machine does not mandate a particular internal structure for objects or a particular layout of their contents However the core components in a CAP file are defined assuming a default structure for certain runtime structures such as descriptions of classes and a default layout for the contents of dynamically allocated objects Information from the descriptor component of the CAP file can be used to format objects in whatever way an implementation requires a7 Special Initialization Methods The Java Card virtual machine supports instance initialization methods exactly as does the Java virtual machine Chapter 3 Structure of the Java Card Virtual Machine 3 3 The Java Card virtual machine includes only limited support for class or interface initi
47. the AID data format used in Java Card technology For complete details refer to ISO 7816 5 AID Registration Category D format The AID format used by the Java Card platform is an array of bytes that can be interpreted as two distinct pieces as shown in TABLE 4 1 The first piece is a 5 byte value known as a RID resource identifier The second piece is a variable length value known as a PIX proprietary identifier extension A PIX can be from 0 to 11 bytes in length Thus an AID can be from 5 to 16 bytes in total length Chapter 4 Binary Representation 4 3 4 2 2 4 4 TABLE 4 1 AID Format RID 5 bytes PIX 0 11 bytes ISO controls the assignment of RIDs to companies with each company obtaining its own unique RID from the ISO Companies manage assignment of PIXs for AIDs using their own RIDs AID Usage In the Java platform packages are uniquely identified using Unicode strings and a naming scheme based on internet domain names In the Java Card platform packages and applets are identified using AIDs Any package that is represented in an export file must be assigned a unique AID The AID for a package is constructed from the concatenation of the company s RID and a PIX for that package This AID corresponds to the string name for the package as shown in FIGURE 4 1 FIGURE 4 1 Mapping Package Identifiers To AIDs package card test Sun s RID com sun card test PIX Each applet
48. the Java Card RE makes this applet the currently selected applet The Java Card RE sends all APDU commands to the currently selected applet a new component added to the CAP file The new component must conform to the general component format It is silently ignored by a Java Card virtual machine that does not recognize the component The identifiers associated with the new component are recorded in the custom_component item of the CAP file s Directory component an applet that is selected by default on a logical channel when it is opened If an applet is designated the default applet on a particular logical channel on the Java Card platform it becomes the active applet by default when that logical channel is opened using the basic channel an acronym for Electrically Erasable Programmable Read Only Memory Glossary 3 entry point objects export file externally visible finalization firewall flash memory framework garbage collection Glossary 4 heap installer see Java Card RE entry point objects a file produced by the Converter that represents the fields and methods of a package that can be imported by classes in other packages in the Java Card platform any classes interfaces their constructors methods and fields that can be accessed from another package according to the Java programming language semantics as defined by the Java Language Specification and Java Card API package access control restricti
49. the fact that overflow has occurred no exception is thrown For all int values x x equals x 1 Notes If a virtual machine does not support the int data type the ineg instruction will not be available 7 5 53 instanceof 7 50 Determine if object is of given type Format instanceof atype indexbyte1 indexbyte2 Forms instanceof 149 0x95 Stack objectref gt result Description Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The unsigned byte atype is a code that indicates if the type against which the object is being checked is an array type or a class type It must take one of the following values or zero TABLE7 3 Array Values Array Type atype T_BOOLEAN 10 T_BYTE TI T_SHORT 12 T_INT T3 T_REFERENCE 14 If the value of atype is 10 11 12 or 13 the values of the indexbyte1 and indexbyte2 must be zero and the value of atype indicates the array type against which to check the object Otherwise the unsigned indexbyte1 and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbyte1 lt lt 8 indexbyte2 The item at that index in the constant pool must be of type CONSTANT_Classref Section 6 7 1 CONSTANT_Classref on page 6 17 a reference to a class or interface type The reference is resolv
50. the method not including the method header Abstract methods have a body_size of zero variable count The number of variable_info entries in the variable_table item Abstract methods have a variable_count of zero line _count The number of line_info entries in the line_table item Abstract methods have a line_count of zero variable _table Contains the variable_info structures for all variables in this method The variable_info structure describes a single local variable of a method It indicates the index into the local variables of the current frame at which the local variable can be found as well as the name and type of the variable It also indicates the range of bytecodes within which the variable has a value variable_info ul index u2 name_index u2 descriptor_index u2 start_pc u2 length The items in the variable_info structure are defined as follows index The index of the variable in the local stack frame as used in load and store bytecodes If the variable at index is of type int it occupies both index and index 1 name_index Contains an index into the strings_table item of the debug_component structure The strings_table entry at the indexed location must be the name of the local variable for example applets descriptor_index Contains an index into the strings_table item of the debug_component structure The strings_table entry at the indexed location must be the typ
51. the token item must be 0xFF access flags The access_flags item is a mask of modifiers used to describe the access permission to and properties of this method The access_flags modifiers for methods are shown in the following table TABLE 6 21 CAP File Method Descriptor Flags Name Value IACC_PUBLIC 0x01 ACC_PRIVATE 0x02 ACC_PROTECTED 0x04 ACC_STATIC 0x08 ACC_FINAL 0x10 ACC_ABSTRACT 0x40 ACC_INIT 0x80 The method access and modifier flags defined in the table above except the ACC_INIT flag are a subset of those defined for methods in a Java class file They have the same meaning and are set under the same conditions as the corresponding flags in a Java class file The ACC_INIT flag is set if the method descriptor identifies a constructor methods In Java a constructor method is recognized by its name lt init gt but in Java Card systems the name is replaced by a token As in the Java verifier these methods require special checks by the verifier for the Java Card platform Java Card verifier All other flag values are reserved Their values must be zero method_offset If the class_descriptor_info structure that contains this method_descriptor_info structure represents a class the method_offset item represents a byte offset into the info item of the Method Component Chapter6 The CAP File Format 6 57 Section 6 9 Method Component on page 6 36 The element at th
52. the unsigned bytes branchbyte1 and branchbyte2 are used to construct a signed 16 bit branchoffset where branchoffset is branchbytel lt lt 8 branchbyte2 Execution proceeds at that offset from the address of the opcode of this if_acmp lt cond gt _w instruction The target address must be that of an opcode of an instruction within the method that contains this if_acmp lt cond gt _w instruction Otherwise execution proceeds at the address of the instruction following this if_acmp lt cond gt _w instruction 1f_scmp lt cond gt Branch if short comparison succeeds Format if_scmp lt cond gt branch Forms if_scmpeq 106 Ox6a if_scmpne 107 Ox6b if_scmplt 108 Ox6c if_scmpge 109 0x6d if_scmpgt 110 0x6e if_scmple 111 Ox6f Stack valuel1 value2 gt Description Both valuel and value2 must be of type short They are both popped from the operand stack and compared All comparisons are signed The results of the comparisons are as follows m eq succeeds if and only if valuel value2 m ne succeeds if and only if valuel 1 4 value2 m lt succeeds if and only if valuel lt value2 m le succeeds if and only if valuel value2 m gt succeeds if and only if valuel gt value2 m ge succeeds if and only if valuel value2 Chapter 7 Java Card Virtual Machine Instruction Set 7 37 If the comparison succeeds branch is used as signed 8 bit offset and execution proceeds at that offset from the
53. to describe the type encoded in the type array typel 6 24 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The type array contains an encoded description of the type composed of individual nibbles If the nibble_count item is an odd number the last nibble in the type array must be 0x0 The values of the type descriptor nibbles are defined in the following table TABLE6 6 Type Descriptor Values Type Value void 0x1 boolean 0x2 byte 0x3 short 0x4 int 0x5 reference 0x6 array of boolean OxA array of byte OxB array of short Oxc array of int OxD array of reference OxE Class reference types are described using the reference nibble 0x6 followed by a 2 byte 4 nibble class_ref structure The class_ref structure is defined as part of the CONSTANT_Classref_info structure Section 6 7 1 CONSTANT_Classref on page 6 17 For example a field of type reference to p1 c1 ina CAP file defining package p0 is described as TABLE6 7 Encoded Reference Type p1 c1 Nibble Value Description 0 0x6 reference 1 lt p1 gt package token b high bit on 3 lt c1 gt class token 4 5 0x0 padding Chapter6 The CAP File Format 6 25 The following are examples of the array types TABLE 6 8 Encoded Byte Array Type Nibble Value Description 0 0xB array of byte 1 0x0 padding TABLE 6 9 Enc
54. unit of program execution A process can have several threads running concurrently each performing a different job such as waiting for events or performing a time consuming job that the program doesn t need to complete before going on When a thread has finished its job it is suspended or destroyed The Java Card virtual machine can support only a single thread of execution Java Card technology programs cannot use class Thread or any of the thread related keywords in the Java programming language an atomic operation in which the developer defines the extent of the operation by indicating in the program code the beginning and end of the transaction the state of transient objects do not persist from one CAD session to the next and are reset to a default state at specified intervals Updates to the values of transient objects are not atomic and are not affected by transactions a process performed on a CAP file that ensures that the binary representation of the package is structurally correct an abstract storage unit A word is large enough to hold a value of type byte short reference or returnAddress Two words are large enough to hold a value of integer type Glossary 9 Glossary 10 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Index Symbols cap file extension 6 4 A aaload 7 5 aastore 7 6 abstract 2 7 AbstractMethodError 2 21 access control 2 3 remote interfaces 2
55. v3 0 Classic Edition e March 2008 7 5 51 imul Multiply int Format imul Forms imul 70 0x46 Stack valuel word1 value1 word2 value2 word1 value2 word2 gt result word1 result word2 Description Both valuel and value2 must be of type int The values are popped from the operand stack The int result is valuel value2 The result is pushed onto the operand stack If an imul instruction overflows then the result is the low order bits of the mathematical product as an int If overflow occurs then the sign of the result may not be the same as the sign of the mathematical product of the two values Notes If a virtual machine does not support the int data type the imul instruction will not be available 7 5 52 ineg Negate int Format ineg Forms ineg 76 0x4c Stack value word1 value word2 gt result word1 result word2 Chapter 7 Java Card Virtual Machine Instruction Set 7 49 Description The value must be of type int It is popped from the operand stack The int result is the arithmetic negation of value value The result is pushed onto the operand stack For int values negation is the same as subtraction from zero Because the Java Card virtual machine uses two s complement representation for integers and the range of two s complement values is not symmetric the negation of the maximum negative int results in that same maximum negative number Despite
56. value1 word2 value2 word1 value2 word2 gt result word1 result word2 Description Both valuel and value2 must be of type int The values are popped from the operand stack An int result is calculated by shifting the result right by s bit positions with zero extension where s is the value of the low five bits of value2 The result is pushed onto the operand stack Notes If valuel is positive and s is value2 amp Ox1f the result is the same as that of valuel gt gt s if valuel is negative the result is equal to the value of the expression valuel gt gt s 2 lt lt s The addition of the 2 lt lt s term cancels out the propagated sign bit The shift distance actually used is always in the range 0 to 31 inclusive as if value2 were subjected to a bitwise logical AND with the mask value 0x1f If a virtual machine does not support the int data type the iushr instruction will not be available 7 5 68 ixor Boolean XOR int Chapter 7 Java Card Virtual Machine Instruction Set 7 65 Format ixor Forms ixor 88 0x58 Stack valuel word1 valuel word2 value2 word1 value2 word2 gt result word1 result word2 Description Both valuel and value2 must be of type int The values are popped from the operand stack An int result is calculated by taking the bitwise exclusive OR of valuel and value2 The result is pushed onto the operand stack Notes If a virtual machine does not suppo
57. various documents or products are made in this document You should have the following documents available m Application Programming Interface for the Java Card Platform Version 3 0 Classic Edition a Runtime Environment Specification Java Card Platform Version 3 0 Classic Edition m The Java Language Specification by James Gosling Bill Joy and Guy L Steele Addison Wesley 1996 m The Java Virtual Machine Specification Second Edition by Tim Lindholm and Frank Yellin Addison Wesley 1999 m The Java Class Libraries An Annotated Reference Second Edition Java Series by Patrick Chan Rosanna Lee and Doug Kramer Addison Wesley 1999 m The Java Remote Method Invocation Specification Revision 1 7 Sun Microsystems Inc m ISO 7816 International Standard First Edition 1987 07 01 http www iso org Acknowledgements Java Card technology is based on Java technology This specification could not exist without all the hard work that went into the development of the Java platform specifications In particular this specification is based significantly on Java Virtual Machine Specification In order to maintain consistency with that specification as well Preface xxi as to make differences easier to notice we have where possible used the words the style and even the visual design of that book Many thanks to Tim Lindholm and Frank Yellin for providing a solid foundation for our work Third Party Web Sites
58. virtual machine s instruction fetch decode execute loop is the same Multi byte operand data is also encoded in big endian order Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 3 10 1 There are a number of ways in which the Java Card virtual machine instruction set diverges from that of the Java virtual machine Most of the differences are due to the Java Card virtual machine s more limited support for data types Another source of divergence is that the Java Card virtual machine is intended to run on 8 bit and 16 bit architectures whereas the Java virtual machine was designed for a 32 bit architecture The rest of the differences are all oriented in one way or another toward optimizing the size or performance of either the Java Card virtual machine or Java Card programs These changes include inlining constant pool data directly in instruction opcodes or operands adding multiple versions of a particular instruction to deal with different datatypes and creating composite instructions for operations on the current object Types and the Java Card Virtual Machine The Java Card virtual machine supports only a subset of the types supported by the Java virtual machine This subset is described in Chapter 2 Type support is reflected in the instruction set as instructions encode the data types on which they operate Given that the Java Card virtual machine supports fewer types than the Java virtual machine
59. with those of the selected instance method The nargs 1 words of arguments and objectref are popped from the operand stack A new stack frame is created for the method being invoked and objectref and the arguments are made the values of its first nargs words of local variables with objectref in local variable 0 arg1 in local variable 1 and so on The new stack frame is then made current and the Java Card virtual machine pc is set to the opcode of the first instruction of the method to be invoked Execution continues with the first instruction of the method Runtime Exception If objectref is null the invokevirtual instruction throws a NullPointerException In some circumstances the invokevirtual instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If the current Chapter 7 Java Card Virtual Machine Instruction Set 7 57 context is not the object s context and the Java Card RE permits invocation of the method the invokevirtual instruction will cause a context switch Section 3 4 Contexts on page 3 2 to the object s context before invoking the method and will cause a return context switch to the previous context when t
60. zero The remote_interfaces item is defined by a remote_interface_info structure 6 8 2 4 implemented_interface_info The implemented_interface_info structure is defined as follows implemented_interface_info class_ref interface ul count ul index count The items in the implemented_interface_info structure are defined as follows interface The interface item has the form of a class_ref structure The class_ref structure is defined as part of the CONSTANT_Classref_info structure Section 6 7 1 CONSTANT_Classref on page 6 17 The interface_info structure referenced by the interface item represents an interface implemented by this class count The count item indicates the number of entries in the index array index The index item is an array that maps declarations of interface methods to implementations of those methods in this class It is a representation of the set of methods declared by the interface and its superinterfaces Chapter6 The CAP File Format 6 33 O28e2e0 Entries in the index array must be ordered such that the interface method token value Section 4 3 7 7 Interface Methods on page 4 10 of the interface method is equal to the index into the array The interface method token value is assigned to the method within the scope of the interface definition not within the scope of this class The values in the index array represent the virtual method tokens Section 4 3 7 6
61. 1 2 FIGURE 4 1 FIGURE 4 2 Figures Java Card API Package Conversion 1 3 Java Card API Package Installation 1 3 Mapping Package Identifiers To AIDs 4 4 Binary Compatibility Example 4 11 xiii xiv Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 TABLE 2 1 TABLE 2 2 TABLE 2 3 TABLE 2 4 TABLE 2 5 TABLE 2 6 TABLE 2 7 TABLE 2 8 TABLE 2 9 TABLE 3 1 TABLE 3 2 TABLE 4 1 TABLE 4 2 TABLE 4 3 TABLE 5 1 TABLE 5 2 TABLE 5 3 TABLE 5 4 TABLE 5 5 TABLE 6 1 Tables Unsupported Keywords 2 4 Supported Keyword 2 7 Unsupported Java Constant Pool Tags 2 14 Supported Java Constant Pool Tags 2 15 Unsupported Bytecode 2 17 Supported Bytecodes 2 17 Support of Java Checked Exceptions 2 20 Support of Java Runtime Exceptions 2 21 Support of Java Errors 2 21 Type Support in the Java Card Virtual Machine Instruction Set 3 5 Storage Types and Computational Types 3 7 AID Format 4 4 Token Range Type and Scope 4 7 Tokens For Instance Fields 4 9 Export File Constant Pool Tags 5 5 Export File Package Flags 5 6 Export File Class Access and Modifier Flags 5 10 Export File Field Access and Modifier Flags 5 13 Export File Method Access and Modifier Flags 5 15 CAP File Component Tags 6 2 xv TABLE 6 2 TABLE 6 3 TABLE 6 4 TABLE 6 5 TABLE 6 6 TABLE 6 7 TABLE 6 8 TABLE 6 9 TABLE 6 10 TABLE 6 11 TABLE 6 12 TABLE 6 13 TABLE 6 14 TABLE 6 15 TABLE 6 16 TABLE 6 17 TABLE 6 18 TABLE 6 19 TAB
62. 10 OA aload_0O 24 18 iconst_1 11 0B aload_1 25 19 iconst_2 12 oc aload_2 26 1A iconst_3 13 0D aload_3 27 1B iconst_4 14 OE anewarray 145 91 iconst_5 15 OF areturn 119 77 iconst_m1 9 09 8 4 Virtual Machine Specification Java Card Platform v3 0 Classic Edition March 2008 TABLE 8 2 mnemonic arraylength as as as as as at ba ba tore tore_0O tore_1 tore_2 tore_3 hrow load store bipush bspush checkcast dup dup_x dup2 ge ge ge ge ge ge ge ge ge ge ge ge ge ge ge tfield_a tfield_a_this tfield_a_w tfield_b tfield_b_this tfield_b_w tfield_i tfield_i_this tfield_i_w tfield_s tfield_s_ this tfield_s_w tstatic_a tstatic_b tstatic_i dec hex 146 92 40 28 43 2B 44 2C 45 2D 46 2E 147 93 37 25 56 38 18 12 16 10 148 94 61 3D 63 3F 62 3E 131 83 173 AD 169 A9 132 84 174 AE 170 AA 134 86 176 BO 172 AC 133 85 175 AF 171 AB 123 7B 124 7C 126 7E mnemonic idiv if_acmpeq if_acmpeq_w if_acmpne if_acmpne_w if_scmpeq if_scmpeq_w if_scmpge if_scmpge_w if_scmpgt if_scmpgt_w if_scmple if_scmple_w if_scmplt if_scmplt_w if_scmpne if_scmpne_w ifeq ifeq w ifge ifge_w ifgt ifgt_w ifle ifle_w iflt iflt_w ifne ifne_w ifnonnull Instructions by Opcode Mnemonic Continued dec hex 72 48 104 68 160 AO 105 69 161 A1 106 6A 162 A2 109 6D 165 A5 110 6E 166 A6 111 6F 167
63. 2 8 2 2 4 1 Packages 2 9 2 2 4 2 Classes 2 9 2 2 4 3 Objects 2 10 2 2 4 4 Methods 2 10 2 2 4 5 Switch Statements 2 11 2 2 4 6 Class Initialization 2 11 2 2 5 Multiselectable Applets Restrictions 2 12 2 2 6 Java Card Platform Remote Method Invocation RMI Restrictions 2 12 2 2 6 1 Remote Classes and Remote Interfaces 2 12 2 2 6 2 Access Control of Remote Interfaces 2 12 2 2 6 3 Parameters and Return Values 2 13 2 3 Java Card VM Subset 2 13 2 3 1 Class File Subset 2 13 2 3 1 1 Not Supported in Class Files 2 14 2 3 1 2 Supported in Class Files 2 15 2 3 2 Bytecode Subset 2 16 2 3 2 1 Unsupported Bytecodes 2 17 2 3 2 2 Supported Bytecodes 2 17 2 3 2 3 Static Restrictions on Bytecodes 2 18 2 3 3 Exceptions 2 19 2 3 3 1 Uncaught and Uncatchable Exceptions 2 19 2 3 3 2 Checked Exceptions 2 20 2 3 3 3 Runtime Exceptions 2 21 iv Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 2 3 3 4 Errors 2 21 Structure of the Java Card Virtual Machine 3 1 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9 3 10 Data Types and Values 3 1 Words 3 2 Runtime Data Areas 3 2 Contexts 3 2 Frames 3 3 Representation of Objects 3 3 Special Initialization Methods 3 3 Exceptions 3 4 Binary File Formats 3 4 Instruction Set Summary 3 4 3 10 1 Types and the Java Card Virtual Machine 3 5 Binary Representation 4 1 4 1 4 2 4 3 Java Card Platform File Formats 4 1 4 1 1 Export File Format 4 2 4 1 2 CAP Fil
64. 3 0 If a virtual machine does not support the int data type the value of atype may not be 13 array type T_INT 7 5 54 invokeinterface Invoke interface method Format invokeinterface nargs 9 This version of the Java Card virtual machine specification does not support multi dimensional arrays Therefore neither SC or TC can be an array type 7 52 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 indexbyte1 indexbyte2 method Forms invokeinterface 142 0x8e Stack objectref arg1 arg2 gt Description The unsigned indexbytel and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbytel lt lt 8 indexbyte2 The constant pool item at that index must be of type CONSTANT_Classref Section 6 7 1 CONSTANT_Classref on page 6 17 a reference to an interface class The specified interface is resolved The nargs operand is an unsigned byte that must not be zero The method operand is an unsigned byte that is the interface method token for the method to be invoked The interface method must not be lt init gt or an instance initialization method The objectref must be of type reference and must be followed on the operand stack by nargs 1 words of arguments The number of words of arguments and the type and order
65. 3 istore Store int into local variable Format istore index Forms istore 42 Ox2a Chapter 7 Java Card Virtual Machine Instruction Set 7 61 Stack value word1 value word2 gt Description The index is an unsigned byte Both index and index 1 must be a valid index into the local variables of the current frame Section 3 5 Frames on page 3 3 The value on top of the operand stack must be of type int It is popped from the operand stack and the local variables at index and index 1 are set to value Notes If a virtual machine does not support the int data type the istore instruction will not be available 7 5 64 istore_ lt n gt Store int into local variable Format istore_ lt n gt Forms istore_O 51 0x33 istore_1 52 0x34 istore_2 53 0x35 istore_3 54 0x36 Stack value word1 value word2 gt Description Both lt n gt and lt n gt 1 must be a valid indices into the local variables of the current frame Section 3 5 Frames on page 3 3 The value on top of the operand stack must be of type int It is popped from the operand stack and the local variables at index and index 1 are set to value Notes If a virtual machine does not support the int data type the istore_ lt n gt instruction will not be available 7 62 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 65 7 5 66 isub Sub
66. 4 0x40 Stack WOrdM4N wordM 1 wordM word gt wordM word1 wordM 4N wordM 1 Description The unsigned byte mn is used to construct two parameter values The high nibble mn amp Oxf0 gt gt 4 is used as the value m The low nibble mn amp Oxf is used as the value n Permissible values for both m and n are 1 and 2 The top m words on the operand stack are swapped with the n words immediately below The swap_x instruction must not be used unless the ranges of words 1 through m and words m 1 through n each contain either a 16 bit data type two 16 bit data types a 32 bit data type a 16 bit data type and a 32 bit data type in either order or two 32 bit data types 13 Sign extension to 32 bits ensures that the result computed by this instruction will be exactly equal to that computed by the Java iushr instruction regardless of the input values In a Java Card virtual machine the expression Oxffff gt gt gt 0x01 yields Oxffff where gt gt gt is performed by the sushr instruction The same result is rendered by a Java virtual machine Chapter 7 Java Card Virtual Machine Instruction Set 7 97 Notes Except for restrictions preserving the integrity of 32 bit data types the swap_x instruction operates on untyped words ignoring the types of data they contain If a virtual machine does not support the int data type the only permissible value for both m and n is 1 7
67. 5 109 sxor Boolean XOR short Format Sxor Forms sxor 87 0x57 Stack value1 value2 gt result Description Both valuel and value2 must be of type short The values are popped from the operand stack A short result is calculated by taking the bitwise exclusive OR of valuel and value2 The result is pushed onto the operand stack 7 98 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 CHAPTER Tables of Instructions The following pages contain lists of the APDU instructions recognized by the Java Card platform organized by opcode value TABLE 8 1 and by opcode mnemonic TABLE 8 2 TABLE 8 1 Instructions by Opcode Value dec hex mnemonic dec hex mnemonic 0 00 nop 47 2F sstore_0 1 01 aconst_null 48 30 sstore_1 2 02 sconst_m1 49 31 sstore_2 3 03 sconst_0 50 32 sstore_3 4 04 sconst_1 51 33 istore_0 5 05 sconst_2 52 34 istore_1 6 06 sconst_3 53 35 istore_2 7 07 sconst_4 54 36 istore_3 8 08 sconst_5 55 37 aastore 9 09 iconst_m1l 56 38 bastore 10 OA iconst_0 57 39 sastore TI 0B iconst_1 58 3A iastore 12 oc iconst_2 59 3B pop 13 OD iconst_3 60 3C pop2 14 OE iconst_4 61 3D dup 15 OF iconst_5 62 3E dup2 16 10 bspush 63 3F dup_x 17 Lt sspush 64 40 swap_x 8 1 TABLE 8 1 Instructions by Opcode Value Continued dec hex mnemonic dec hex mnemonic 18 12 bipush 65 41 sada 19 13 sipush 66 42 iadd 20 14 iipush 67 43 ssub 21 15
68. 5 18 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 CHAPTER The CAP File Format This chapter describes the Java Card converted applet CAP file format Each CAP file contains all of the classes and interfaces defined in one Java package Java Card Converters must be capable of producing CAP files that conform to the specification provided in this chapter A CAP file consists of a stream of 8 bit bytes All 16 bit and 32 bit quantities are constructed by reading in two and four consecutive 8 bit bytes respectively Multibyte data items are always stored in big endian order where the high order bytes come first The first bit read of an 8 bit quantity is considered the high bit This chapter defines its own set of data types representing Java Card CAP file data the types u1 and u2 represent an unsigned one and two byte quantities respectively Some u1 types are represented as bitfield structures consisting of arrays of bits The zeroeth bit in each bit array represents the most significant bit or high bit The Java Card CAP file format is presented using pseudo structures written in a C like structure notation To avoid confusion with the fields of Java Card virtual machine classes and class instances the contents of the structures describing the Java Card CAP file format are referred to as items Unlike the fields of a C structure successive items are stored in the Java Card platform f
69. 755 aloa d si gt 79 7 5 6 anewarray 7 10 7 5 7 areturn 7 10 7 5 8 arraylength 7 11 7 5 9 astore 7 12 7 5 10 astore_ lt n gt 7 12 viii Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 11 7 5 12 7 5 13 7 5 14 7 5 15 7 5 16 7 5 17 7 5 18 7 5 19 7 5 20 7 9 21 7 9 22 7 5 23 7 5 24 7 5 29 7 5 26 7 9 27 7 5 28 7 5 29 7 5 30 7 9 31 7 9 32 7 5 33 7 5 34 7 5 35 7 5 36 7 9 37 7 5 38 athrow 7 13 baload 7 14 bastore 7 15 bipush 7 16 bspush 7 16 checkcast 7 17 dup 7 19 dup_x 7 20 dup2 7 21 getfield_ lt t gt 7 22 getfield_ lt t gt _this 7 23 getfield_ lt t gt _w 7 25 getstatic_ lt t gt 7 26 goto 7 27 goto_w 7 28 i2b 7 29 i2s 7 29 iadd 7 30 iaload 7 31 iand 7 32 iastore 7 32 icmp 7 33 iconst_ lt i gt 7 34 idiv 7 34 if_acmp lt cond gt 7 35 if_acmp lt cond gt _w 7 36 if_semp lt cond gt 7 37 if_scmp lt cond gt _w 7 38 Contents 7 5 39 7 5 40 7 5 41 7 5 42 7 5 43 7 5 44 7 5 45 7 5 46 7 5 47 7 5 48 7 5 49 7 5 50 7 9 01 7 9 92 7 5 53 7 5 54 7 5 99 7 5 56 7 5 57 7 5 58 7 5 99 7 5 60 7 5 61 7 5 62 7 5 63 7 5 64 7 5 65 7 5 66 if lt cond gt 7 39 if lt cond gt _w 7 40 ifnonnull 7 41 ifnonnull_w 7 41 ifnull 7 42 ifnull_w 7 43 iinc 7 43 iinc_w 7 44 iipush 7 45 load 7 46 H 7 46 iload_ lt n gt ilookupswitch 7 47 imul 7 49 ineg 7 49 instanceof 7 50 invokeinterface 7 52 7 54 7 55 7 56
70. 8 ACC_FINAL 0x10 The field access and modifier flags defined in the table above are a subset of those defined for fields in a Java class file They have the same meaning and are set under the same conditions as the corresponding flags in a Java class file All other flag values are reserved Their values must be zero field_ref The field_ref item represents a reference to this field If the ACC_STATIC flag is equal to 1 this item represents a static_field_ref as defined in the CONSTANT_StaticFieldref structure Section 6 7 3 CONSTANT_StaticFieldref and CONSTANT_StaticMethodref on page 6 20 If the ACC_STATIC flag is equal to 0 this item represents a reference to an instance field It contains a class_ref item and an instance field token item These items are defined in the same manner as in the CONSTANT_InstanceFieldref structure Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT_VirtualMethodref and CONSTANT_SuperMethodref on page 6 18 Chapter6 The CAP File Format 6 55 type The type item indicates the type of this field directly or indirectly If this field is a primitive type boolean byte short or int the high bit of this item is equal to 1 otherwise the high bit of this item is equal to 0 primitive_type The primitive_type item represents the type of this field using the values in the table below As noted above the high bit of the primitive_type item is equal to 1 TABLE 6 20 Primi
71. ANT_StaticFieldref 5 CONSTANT_StaticMethodref 6 Java Card platform constant types Java Card constant types are more specific than those in Java class files The categories indicate not only the type of the item referenced but also the manner in which it is referenced For example in the Java constant pool there is one constant type for method references while in the Java Card platform constant pool Java Card constant pool there are three constant types for method references one for virtual method invocations using the invokevirtual bytecode one for super method invocations using the invokespecial bytecode and one for static method invocations using either the invokestatic or invokespecial bytecode 4 The additional information provided by a constant type in Java Card technologies simplifies resolution of references There are no ordering constraints on constant pool entries It is recommended however that CONSTANT_InstanceFieldref Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT_VirtualMethodref and CONSTANT_SuperMethodre on page 6 18 constants occur early in the array to permit using getfield_T and putfield_T bytecodes instead of getfield_T_w and putfield_T_w bytecodes The former have 1 byte constant pool index parameters while the latter have 2 byte constant pool index parameters 4 The constant pool index parameter of an invokespecial bytecode is to a CONSTANT_StaticMethodref when the method re
72. All 16 bit and 32 bit quantities are constructed by reading in two and four consecutive 8 bit bytes respectively Multibyte data items are always stored in big endian order where the high order bytes come first This chapter defines its own set of data types representing Java Card export file data the types u1 u2 and u4 represent an unsigned one two and four byte quantities respectively The Java Card export file format is presented using pseudo structures written in a C like structure notation To avoid confusion with the fields of Java Card virtual machine classes and class instances the contents of the structures describing the Java Card export file format are referred to as items Unlike the fields of a C structure successive items are stored in the Java Card platform file sequentially without padding or alignment Variable sized tables consisting of variable sized items are used in several export file structures Although we will use C like array syntax to refer to table items the fact that tables are streams of varying sized structures means that it is not possible to directly translate a table index into a byte offset into the table In a data structure that is referred to as an array the elements are equal in size 5 1 Export File Name As described in Section 4 1 1 Export File Format on page 4 2 the name of a export file must be the last portion of the package specification followed by the extension e
73. Cc CAD Glossary 2 CAP file 1 3 4 1 4 2 6 13 Glossary 2 applet component 6 12 class component 6 22 component Glossary 2 component file names 6 3 component installation 6 5 constant pool component 6 14 custom component Glossary 3 debug component 6 59 defining components 6 4 descriptor component 6 51 directory component 6 9 directory_component structure 6 9 export component 6 49 format 1 2 3 4 6 1 header component 6 6 import_component structure 6 13 method component 6 36 naming 6 4 reference location component 6 46 static field component 6 42 verificatioion 1 4 Card Acceptance Device Glossary 2 card applet 1 1 card session Glossary 2 case 2 7 cast Glossary 3 catch 2 7 char 2 4 checkcast 7 17 class 2 7 in a package 2 9 initialization 2 11 initialization methods 3 4 instances 2 10 object 2 7 remote 2 12 throwable 2 8 unsupported 2 5 class 2 7 class component 6 20 class component of a CAP file 6 22 class file verifier 1 4 lass file 2 13 4 1 lass_debug_info 6 61 lass_descriptor_info 6 52 lass_info structure 6 27 lassCastException 2 21 lassCirculatoryError 2 21 lassFile 2 15 lassFormatError 2 21 CO OQ OO OO Oe lassNotFoundException 2 20 classsystem 2 5 CloneNotSupportedException 2 20 cloning 2 3 compatibility 4 11 component model 6 2 components class 6 20 in CAP files 6 2 constant pool 2 14 2 15 5 5 Glossar
74. Component on page 6 36 to the method_info structure representing the method Entries for methods that are declared abstract not including those defined by interfaces are represented in the package_virtual_method_table array in the same way as non abstract methods interfaces The interfaces item of the class_info structure represents a table of variable length implemented_interface_info structures The table must contain an entry for each of the directly implemented interfaces indicated in the declaration of this class and each of the interfaces in the hierarchies of those interfaces Interfaces that occur more than once are represented by a single entry Given the declarations below the number of entries for class c0 is 1 and the entry in the interfaces array is i0 The number of entries for class c1 is 3 and the entries in the interfaces array are i1 i2 and i3 The entries for class c1 must not include interface i0 which is implemented only by the superclass of c1 6 32 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 interface i0 interface il interface i2 extends il interface i3 class c0 implements i0 class cl extends c0 implements i2 i3 remote_interfaces The remote_interfaces item represents information required if this class or any of its super classes implements a remote interface This item must be omitted if the ACC_REMOTE flag has a value of
75. Component on page 6 42 No components in the CAP file reference the Descriptor Component The Descriptor Component is represented by the following structure descriptor_component ul tag u2 size ul class_count Chapter6 The CAP File Format 6 51 class_descriptor_info classes class_count type_descriptor_info types The items of the descriptor_component structure are as follows tag The tag item has the value COMPONENT_Descriptor 11 size The size item indicates the number of bytes in the descriptor_component structure excluding the tag and size items The value of the size item must be greater than zero class_count The class_count item represents the number of entries in the classes table classes The classes item represents a table of variable length class_descriptor_info structures Each class and interface defined in this package is represented in the table types The types item represents a type_descriptor_info structure This structure lists the set of field types and method signatures of the fields and methods defined or referenced in this package Those referenced are enumerated in the Constant Pool Component class _descriptor_info The class_descriptor_info structure is used to describe a class or interface defined in this package class_descriptor_info ul token ul access_flags class_ref this_class_ref ul interface_count u2 field_count u2 method_count class_ref i
76. ExportFile export_class_count The value of the export_class_count item gives the number of elements in the classes table classes Each value of the classes table is a variable length class_info structure Section 5 7 Classes and Interfaces on page 5 9 giving the description of a publicly accessible class or interface declared in this package If the ACC_LIBRARY flag item in the CONSTANT_Package_info Section 5 6 1 CONSTANT_Package on page 5 5 structure indicated by the this_package item is set the classes table has an entry for each public class and interface declared in this package If the ACC_LIBRARY flag item is not set the classes table has an entry for each public shareable interface declared in this package 1 This restriction of exporting only shareable interfaces in non library packages is imposed by the firewall defined in the Runtime Environment Specification Java Card Platform Version 3 0 5 4 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 5 6 5 6 1 Constant Pool All constant_pool table entries have the following general format cp_info ul tag ul info Each item in the constant_pool must begin with a 1 byte tag indicating the kind of cp_info entry The content of the info array varies with the value of tag The valid tags and their values are listed in TABLE 5 1 Each tag byte must be followed by two or more bytes giving information abou
77. FieldError IX NoSuchMethodError NoClassDefFoundError UnsatisfiedLinkError VerifyError XIXI XTX ThreadDeath VirtualMachineError InternalError OutOfMemoryError StackOverflowError UnknownError UnsupportedClassVersionError XIXI KT KL X X Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 CHAPTER O Structure of the Java Card Virtual Machine The specification of the Java Card virtual machine is in many ways quite similar to that of the Java virtual machine This similarity is of course intentional as the design of the Java Card virtual machine was based on that of the Java virtual machine Rather than reiterate all the details of this specification which are shared with that of the Java virtual machine this chapter will mainly refer to its counterpart in The Java Virtual Machine Specification 2nd Edition providing new information only where the Java Card virtual machine differs 3 1 Data Types and Values The Java Card virtual machine supports the same two kinds of data types as the Java virtual machine primitive types and reference types Likewise the same two kinds of values are used primitive values and reference values The primitive data types supported by the Java Card virtual machine are the numeric types the boolean type and the returnAddress type The numeric types consist only of these ty
78. Format ifnonnull branch Forms ifnonnull 103 0x67 Stack Value gt Description The value must be of type reference It is popped from the operand stack If the value is not null branch is used as signed 8 bit offset and execution proceeds at that offset from the address of the opcode of this ifnonnull instruction The target address must be that of an opcode of an instruction within the method that contains this ifnonnull instruction Otherwise execution proceeds at the address of the instruction following this ifnonnull instruction ifnonnull _w Branch if reference not null wide index Chapter 7 Java Card Virtual Machine Instruction Set 7 41 Format ifnonnull_w branchbyte1 branchbyte2 Forms ifnonnull_w 159 0x9f Stack Value gt Description The value must be of type reference It is popped from the operand stack If the value is not null the unsigned bytes branchbytel and branchbyte2 are used to construct a signed 16 bit branchoffset where branchoffset is branchbytel lt lt 8 branchbyte2 Execution proceeds at that offset from the address of the opcode of this ifnonnull_w instruction The target address must be that of an opcode of an instruction within the method that contains this ifnonnull_w instruction Otherwise execution proceeds at the address of the instruction following this ifnonnull_w instruction 7 5 43 ifnull Branch if reference is null
79. Interfaces on page 2 12 All other class access and modifier flags are defined in the same way and with the same restrictions as described in The Java Virtual Machine Specification Since all classes and interfaces represented in an export file are public the ACC_PUBLIC flag must always be set All other flag values are reserved Their values must be zero name_index 3 The ACC_SHAREABLE flag is defined to enable Java Card virtual machines to implement the firewall restrictions defined by the Runtime Environment Specification Java Card Platform Version 3 0 5 10 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The value of the name_index item must be a valid index into the constant_pool table The constant_pool entry at that index must be a CONSTANT_Classref_info Section 5 6 2 CONSTANT_Classref on page 5 7 structure representing a valid fully qualified Java class or interface name export_supers_count The value of the export_supers_count item indicates the number of entries in the supers array supers The supers array contains an entry for each public superclass of this class or interface It does not include package visible superclasses For a class each value in the supers array must be a valid index into the constant_pool table The constant_pool entry at each value must be a CONSTANT_Classref_info structure Section 5 6 2 CONSTANT_Classref on page 5 7 rep
80. LE 6 20 TABLE 6 21 TABLE 6 22 TABLE 6 23 TABLE 6 24 TABLE 7 1 TABLE 7 2 TABLE 7 3 TABLE 7 4 TABLE 8 1 TABLE 8 2 CAP File Component File Names 6 3 Reference Component Install Order 6 5 CAP File Package Flags 6 7 CAP File Constant Pool Tags 6 16 Type Descriptor Values 6 25 Encoded Reference Type p1 c1 6 25 Encoded Byte Array Type 6 26 Encoded Reference Array Type p1 c1 6 26 Encoded Method Signature V 6 26 Encoded Method Signature Lp1 ci S 6 26 CAP File Interface and Class Flags 6 28 CAP File Method Flags 6 41 Segments of a Static Field Image 6 43 Static Field Sizes 6 43 Array Types 6 45 One byte Reference Location Example 6 48 CAP File Class Descriptor Flags 6 53 CAP File Field Descriptor Flags 6 55 Primitive Type Descriptor Values 6 56 CAP File Method Descriptor Flags 6 57 Class Access and Modifier Flags 6 61 Field Access and Modifier Flags 6 64 Method Modifier Flags 6 66 Example Instruction Page 7 4 Array Values 7 18 Array Values 7 51 Array Values 7 68 Instructions by Opcode Value 8 1 Instructions by Opcode Mnemonic 8 4 xvi Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Preface Java Card technology combines a subset of the Java programming language with a runtime environment optimized for smart cards and similar small memory embedded devices The goal of Java Card technology is to bring many of the benefits of Java software programming to the res
81. The external_ref item represents a reference to a static field or method defined in an imported package The items in the structure are package_token The package_token item represents a package token Section 4 3 7 1 Package on page 4 8 defined in the Import Component Section 6 6 Import Component on page 6 13 of this CAP file The value of this token must be a valid index into the packages table item of the import_component structure The package represented at that index must be the imported package The value of the package token must be between 0 and 127 inclusive Chapter6 The CAP File Format 6 21 The high bit of the package_token item is equal to one class_token The class_token item represents the token Section 4 3 7 2 Classes and Interfaces on page 4 8 of the class of the referenced class It has the value of the class token of the class as defined in the Export file of the imported package The class indicated by the class_token item must define the referenced field or method token The token item of a CONSTANT_StaticFieldref_info structure represents a static field token Section 4 3 7 3 Static Fields on page 4 8 as defined in the Export file of the imported package It has the value of the token of the referenced field The token item of a CONSTANT_StaticMethodref_info structure represents a static method token Section 4 3 7 4 Static Methods and Constructors on page 4 8 as def
82. The value is popped from the operand stack If the field is of type byte or type boolean the value is truncated to a byte The field is set to the value 7 76 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 79 Notes In some circumstances the putstatic_a instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object being stored in the field The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If a virtual machine does not support the int data type the putstatic_i instruction will not be available ret Return from subroutine Format ret index Forms ret 114 0x72 Stack No change Description The index is an unsigned byte that must be a valid index into the local variables of the current frame Section 3 5 Frames on page 3 3 The local variable at index must contain a value of type returnAddress The contents of the local variable are written into the Java Card virtual machine s pc register and execution continues there Notes The ret instruction is used with the jsr instruction in the implementation of the finally keyword of the Java language Note that jsr pushes the address onto the stack and ret gets it out of a local va
83. ack must be of type short It is popped from the operand stack and the value of the local variable at index is set to value 7 5 104 Ssstore lt n gt Store short into local variable Format sstore_ lt n gt Forms sstore_0 47 0x2f sstore_1 48 0x30 sstore_2 49 0x31 sstore_3 50 0x32 Stack Value gt Description The lt n gt must be a valid index into the local variables of the current frame Section 3 5 Frames on page 3 3 The value on top of the operand stack must be of type short It is popped from the operand stack and the value of the local variable at lt n gt is set to value 7 5 105 ssub Subtract short Format ssub Forms ssub 67 0x43 Stack 7 94 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 valuel1 value2 gt result Description Both valuel and value2 must be of type short The values are popped from the operand stack The short result is valuel value2 The result is pushed onto the operand stack For short subtraction a b produces the same result as a b For short values subtraction from zeros is the same as negation Despite the fact that overflow or underflow may occur in which case the result may have a different sign than the true mathematical result execution of a ssub instruction never throws a runtime exception 7 5 106 stableswitch Access jump table by short index and j
84. al Machine Instruction Set 7 51 a If T is a class type then T must be Object Section 2 2 2 4 Classes on page 2 7 a If Tis an interface type T must be the same interface as S or a superinterface of S m If Sis an array type namely the type SC that is an array of components of type SC then a If T isa class type then T must be Object a If Tis an array type namely the type TC an array of components of type TC then one of the following must be true TC and SC are the same primitive type Section 3 1 Data Types and Values on page 3 1 TC and SC are reference types Section 3 1 Data Types and Values on page 3 1 with type SC assignable to TC by these rules a If Tis an interface type T must be one of the interfaces implemented by arrays Notes The instanceof instruction is fundamentally very similar to the checkcast instruction It differs in its treatment of null its behavior when its test fails checkcast throws an exception instanceof pushes a result code and its effect on the operand stack In some circumstances the instanceof instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version
85. al variables at index and index 1 is incremented by const Notes If a virtual machine does not support the int data type the iinc_w instruction will not be available 7 5 47 iipush Push int Format iipush byte1 byte2 byte3 byte4 Forms iipush 20 0x14 Stack gt valuel word1 valuel word2 Description The immediate unsigned bytel byte2 byte3 and byte4 values are assembled into a signed int where the value of the int is bytel lt lt 24 byte2 lt lt 16 byte3 lt lt 8 byte4 The resulting value is pushed onto the operand stack Notes Chapter 7 Java Card Virtual Machine Instruction Set 7 45 If a virtual machine does not support the int data type the iipush instruction will not be available 7 5 48 iload Load int from local variable Format iload index Forms iload 23 0x17 Stack o gt valuel word1 valuel word2 Description The index is an unsigned byte Both index and index 1 must be valid indices into the local variables of the current frame Section 3 5 Frames on page 3 3 The local variables at index and index 1 together must contain an int The value of the local variables at index and index 1 is pushed onto the operand stack Notes If a virtual machine does not support the int data type the iload instruction will not be available 7 5 49 iload lt n gt Load int from local variable Format
86. alization methods There is no general mechanism for executing lt clinit gt methods on a Java Card virtual machine Instead a CAP file includes information for initializing class data as defined in Section 2 2 4 6 Class Initialization on page 2 11 3 8 Exceptions Exception support in the Java Card virtual machine is identical to support for exceptions in the Java virtual machine 3 9 Binary File Formats This specification defines two binary file formats which enable platform independent development distribution and execution of Java Card programs The CAP file format describes files that contain executable code and can be downloaded and installed onto a Java Card technology enabled device A CAP file is produced by a Java Card platform Converter tool and contains a converted form of an entire package of Java classes This file format s relationship to the Java Card virtual machine is analogous to the relationship of the class file format to the Java virtual machine The export file format describes files that contain the public linking information of Java Card API packages A package s export file is used when converting client packages of that package 3 10 3 4 Instruction Set Summary The Java Card virtual machine instruction set is quite similar to the Java virtual machine instruction set Individual instructions consist of a one byte opcode and zero or more operands The pseudo code for the Java Card
87. aload Load int from array Format iaload Forms iaload 39 0x27 Stack arrayref index gt value word1 value word2 Description The arrayref must be of type reference and must refer to an array whose components are of type int The index must be of type short Both arrayref and index are popped from the operand stack The int value in the component of the array at index is retrieved and pushed onto the top of the operand stack Runtime Exceptions If arrayref is null iaload throws a NullPointerException Otherwise if index is not within the bounds of the array referenced by arrayref the iaload instruction throws an ArrayIndexOutOfBoundsException Notes In some circumstances the iaload instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the array referenced by arrayref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If a virtual machine does not support the int data type the iaload instruction will not be available Chapter 7 Java Card Virtual Machine Instruction Set 7 31 7 5 30 and Boolean AND int Format iand Forms iand 84 0x54 Stack valuel word1 valuel word2 value2 word1 value2 word2 gt result word1 result word2 Descri
88. aload 7 80 sand 7 81 sastore 7 81 sconst_ lt s gt 7 82 sdiv 7 83 security 1 4 1 5 exceptions 7 3 manager 2 2 SecurityException 2 21 Shareable interface 1 5 shareable interface objects 1 5 short 2 7 3 1 sinc 7 83 sinc_w 7 84 sipush 7 85 sload 7 85 sload_ lt n gt 7 86 slookupswitch 7 87 smart cards 1 1 smul 7 88 sneg 7 88 sor 7 89 srem 7 90 sreturn 7 90 sshl 7 91 sshr 7 92 Index 6 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 sspush 7 93 sstore 7 93 sstore_ lt n gt 7 94 ssub 7 94 stableswitch 7 95 StackOverflowError 2 22 static 2 7 static field component of a CAP file 6 42 static field image 6 42 static fields 2 10 static methods 2 10 strictfp 2 4 StringIndexOutOfBoundsException 2 21 super 2 7 sushr 7 96 swap_x 7 97 switch 2 7 switch statements 2 11 sxor 7 98 synchronized 2 4 system 2 5 T tables in CAP files 6 1 in export files 5 1 tableswitch 2 19 this 2 7 ThreadDeath 2 22 threads 2 2 3 2 throw 2 7 throwable 2 8 throws 2 7 token based linking 4 5 tokens assignment 4 7 class 4 8 instance field 4 9 interface methods 4 10 linking 4 7 package 4 8 private 4 5 public 4 5 range type scope 4 7 static field 4 8 static method 4 8 virtual method 4 10 transient 2 4 try 2 7 type_descriptor structure 6 24 type_descriptor_info 6 58 types 2 7
89. aload 68 44 isub 22 16 sload 69 45 smul 23 17 iload 70 46 imul 24 18 aload_0O 71 47 sdiv 25 19 aload_1 72 48 idiv 26 1A aload_2 73 49 srem 27 1B aload_3 74 4A irem 28 1c sload_0 75 4B sneg 29 1D sload_1 76 4c ineg 30 1E sload_2 77 4D sshl 31 1F sload_3 78 4E ishl 32 20 iload_0 79 4F sshr 33 21 iload_1 80 50 ishr 34 22 iload_2 81 51 sushr 35 23 iload_3 82 52 iushr 36 24 aaload 83 53 sand 37 25 baload 84 54 iand 38 26 saload 85 55 sor 39 27 iaload 86 56 ior 40 28 astore 87 57 sxor 41 29 sstore 88 58 ixor 42 2A istore 89 59 sinc 43 2B astore_0 90 5A linc 44 2C astore_1 91 5B s2b 45 2D astore_2 92 5C s2i 46 2E astore_3 93 5D i2b 94 5E i2s 141 8D invokestatic 8 2 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 TABLE 8 1 dec hex 95 5F 96 60 97 61 98 62 99 63 100 64 101 65 102 66 103 67 104 68 105 69 106 6A 107 6B 108 6C 109 6D 110 6E 111 6F 112 70 113 71 114 72 115 73 116 74 117 75 118 76 119 77 120 78 121 79 122 7A 123 7B 124 7C mnemonic icmp ifeq ifne iflt ifge ifgt ifle ifnull ifnonnull if_acmpeq if_acmpne if_scmpeq if_scmpne if_scmplt if_scmpge if_scmpgt if_scmple goto jsr ret stableswitch itableswitch slookupswitch ilookupswitch areturn sreturn ireturn return getstatic_a getstatic_b dec hex 142 8E 143 8F 144 90 145 91 146 92 147 93 148 94 L49 95 L50 96 151 97 L52 98 t537 99 L154 9A 155 9B 156
90. alue of the low five bits of value2 The result is pushed onto the operand stack Notes The resulting value is value1 2s where s is value2 amp Ox1f For nonnegative valuel this is equivalent even if overflow occurs to truncating short division by 2 to the power s The shift distance actually used is always in the range 0 to 31 inclusive as if value2 were subjected to a bitwise logical AND with the mask value Ox1f The mask value of 0x1f allows shifting beyond the range of a 16 bit short value It is used by this instruction however to ensure results equal to those generated by the Java instruction ishr 7 92 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 102 sspush Push short Format sspush byte1 byte2 Forms sspush 17 0x11 Stack a gt value Description The immediate unsigned byte1 and byte2 values are assembled into a signed short where the value of the short is byte1 lt lt 8 byte2 The resulting value is pushed onto the operand stack 7 5 103 sstore Store short into local variable Format sstore index Forms sstore 41 0x29 Stack Value gt Description Chapter 7 Java Card Virtual Machine Instruction Set 7 93 The index is an unsigned byte that must be a valid index into the local variables of the current frame Section 3 5 Frames on page 3 3 The value on top of the operand st
91. ands and procedures such as shutting down the system booting the system and configuring devices Refer to the following for this information a Software documentation that you received with your system m Solaris Operating System documentation which is at http docs sun com Preface xix Shell Prompts Shell Prompt C shell C shell superuser Bourne shell and Korn shell Bourne shell and Korn shell superuser machine name amp machine name Typographic Conventions Typeface Meaning Examples AaBbCc123 The names of commands files Edit your Login file and directories on screen Use 1s a to list all files computer output You have mail AaBbCc123 What you type when contrasted su with on screen computer output password AaBbCc123 Book titles new words or terms Read Chapter 6 in the User s Guide words to be emphasized Replace command line variables with real names or values These are called class options You must be superuser to do this To delete a file type rm filename The settings on your browser might differ from these settings XX Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Documentation Support and Training Sun Function URL Documentation http www sun com documentation Support http www sun com support Training http www sun com training Related Documentation References to
92. applet on that logical channel For more information see the ISO IEC 7816 Specification Part 4 http www iso org MAC _ an acronym for Message Authentication Code MAC is an encryption of data for security purposes mask production masking refers to embedding the Java Card virtual machine runtime environment and applets in the read only memory of a smart card during manufacture method a procedure or routine associated with one or more classes in object oriented languages Glossary 6 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 multiselectable applets multiselected applet namespace native method nibble object oriented object owner objects origin logical channel owning context package PCD persistent object PIX implements the javacard framework MultiSelectable interface Multiselectable applets can be selected on multiple logical channels at the same time They can also accept other applets belonging to the same package being selected simultaneously an applet instance that is selected and therefore active on more than one logical channel simultaneously a set of names in which all names are unique a method that is not implemented in the Java programming language but in another language The CAP file format does not support native methods four bits a programming methodology based on the concept of an object which is a data structure e
93. ars in the instruction format diagram and a separate forms line lists 7 4 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 700 all member mnemonics and opcodes For example the forms line for the sconst_ lt s gt family of instructions giving mnemonic and opcode information for the two instructions in that family sconst_0 and sconst_1 is Forms sconst_0 3 0x3 sconst_1 4 0x4 In the description of the Java Card virtual machine instructions the effect of an instruction s execution on the operand stack Section 3 5 Frames on page 3 3 of the current frame Section 3 5 Frames on page 3 3 is represented textually with the stack growing from left to right and each word represented separately Thus Stack value1 value2 gt result shows an operation that begins by having a one word value2 on top of the operand stack with a one word valuel just beneath it As a result of the execution of the instruction valuel and value2 are popped from the operand stack and replaced by a one word result which has been calculated by the instruction The remainder of the operand stack represented by an ellipsis is unaffected by the instruction s execution The type int takes two words on the operand stack In the operand stack representation each word is represented separately using a dot notation Stack valuel word1 valuel word2 value2 word1 value2 word2 gt
94. at offset must be the beginning of a method_info structure The method_info structure must represent this method If the class_descriptor_info structure that contains this method_descriptor_info structure represents an interface the value of the method_offset item must be zero type_offset The type_offset item must be a valid offset into the type_descriptor_info structure The type described at that offset represents the signature of this method bytecode_count The bytecode_count item represents the number of bytecodes in this method The value is equal to the length of the bytecodes array item in the method_info structure in the method component Section 6 9 Method Component on page 6 36 of this method exception_handler_count The exception_handler_count item represents the number of exception handlers implemented by this method exception_handler_index The exception_handler_index item represents the index to the first exception_handlers table entry in the method component Section 6 9 Method Component on page 6 36 implemented by this method Succeeding exception_handlers table entries up to the value of the exception_handler_count item are also exception handlers implemented by this method The value of the exception_handler_index item is 0 if the value of the exception_handler_count item is 0 6 13 4 type_descriptor_info The type_descriptor_info structure represents the types of fields and signatures
95. at type of length count is allocated from the heap and a reference arrayref to this new array object is pushed onto the operand stack All components of the new array are initialized to null the default value for reference types Runtime Exception If count is less than zero the anewarray instruction throws a NegativeArraySizeException areturn Return reference from method Format areturn Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 8 Forms areturn 119 0x77 Stack objectref gt empty Description The objectref must be of type reference The objectref is popped from the operand stack of the current frame Section 3 5 Frames on page 3 3 and pushed onto the operand stack of the frame of the invoker Any other values on the operand stack of the current method are discarded The virtual machine then reinstates the frame of the invoker and returns control to the invoker arraylength Get length of array Format arraylength Forms arraylength 146 0x92 Stack arrayref gt length Description The arrayref must be of type reference and must refer to an array It is popped from the operand stack The length of the array it references is determined That length is pushed onto the top of the operand stack as a short Runtime Exception If arrayref is null the arraylength instruction throws a NullPointerException Not
96. ava Card RE detects and restricts attempts to store references to these objects as part of the firewall functionality to prevent unauthorized reuse Examples of these objects are APDU objects and all Java Card RE owned exception objects permanent references to permanent Java Card RE entry point objects can be stored and freely reused Examples of these objects are Java Card RE owned AID instances JDK software an acronym for Java Development Kit The JDK software is a Sun Microsystems Inc product that provides the environment required for software development in the Java programming language The JDK software is available for a variety of operating systems for example Sun Microsystems Solaris OS and Microsoft Windows library package a Java programming language package that does not contain any non abstract classes that extend the class javacard framework Applet An applet package contains one or more non abstract classes that extend the javacard framework Applet class local variable a data item known within a block but inaccessible to code outside the block For example any variable defined within a method is a local variable and cannot be used outside the method logical channel as seen at the card edge works as a logical link to an application on the card A logical channel establishes a communications session between a card applet and the terminal Commands issued on a specific logical channel are forwarded to the active
97. ava program a developer writes one or more Java classes and compiles the source code with a Java compiler producing one or more class files The applet is run tested and debugged on a workstation using simulation tools to emulate the device environment Then when an applet is ready to be downloaded to a device the class files comprising the applet are converted to a CAP converted applet file using a Java Card Converter Chapter 1 Introduction 1 3 The Java Card Converter takes as input all of the class files which make up a Java package A package that contains one or more non abstract subclasses direct or indirect of the javacard framework Applet class is referred to as an applet package Otherwise the package is referred to as a library package The Java Card Converter also takes as input one or more export files An export file contains name and link information for the contents of other packages that are imported by the classes being converted When an applet or library package is converted the converter can also produce an export file for that package After conversion the CAP file is copied to a card terminal such as a desktop computer with a card reader peripheral Then an installation tool on the terminal loads the CAP file and transmits it to the Java Card technology enabled device An installation program on the device receives the contents of the CAP file and prepares the applet to be run by the Java Card virtual machine The vi
98. be positive only if the dividend is positive Moreover the magnitude of the result is always less than the magnitude of the divisor Runtime Exception If the value of the divisor for a short remainder operator is 0 irem throws an ArithmeticException Notes If a virtual machine does not support the int data type the irem instruction will not be available ireturn Return int from method Format ireturn Forms ireturn 121 0x79 Stack value word1 value word2 gt empty Description Chapter 7 Java Card Virtual Machine Instruction Set 7 59 7 9 61 7 60 The value must be of type int It is popped from the operand stack of the current frame Section 3 5 Frames on page 3 3 and pushed onto the operand stack of the frame of the invoker Any other values on the operand stack of the current method are discarded The virtual machine then reinstates the frame of the invoker and returns control to the invoker Notes If a virtual machine does not support the int data type the ireturn instruction will not be available ishl Shift left int Format ishl Forms ishl 78 0x4e Stack valuel word1 value1 word2 value2 word1 value2 word2 gt result word1 result word2 Description Both valuel and value2 must be of type int The values are popped from the operand stack An int result is calculated by shifting value1 left by s bit positions where s is the value of th
99. be used The two reserved opcodes numbers 254 Oxfe and 255 Oxff have the mnemonics impdep1 and impdep2 respectively These instructions are intended to provide back doors or traps to implementation specific functionality implemented in software and hardware respectively Although these opcodes have been reserved they may only be used inside a Java Card virtual machine implementation They cannot appear in valid CAP files 7 3 Virtual Machine Errors A Java Card virtual machine may encounter internal errors or resource limitations that prevent it from executing correctly written Java programs While The Java Virtual Machine Specification allows reporting and handling of virtual machine errors it also states that they cannot ordinarily be handled by application code This Virtual Machine Specification is more restrictive in that it does not allow for any reporting or handling of unrecoverable virtual machine errors at the application code level A virtual machine error is considered unrecoverable if further execution could compromise the security or correct operation of the virtual machine or underlying system software When an unrecoverable error occurs the virtual machine will halt bytecode execution Responses beyond halting the virtual machine are implementation specific policies and are not mandated in this specification In the case where the virtual machine encounters a recoverable error such as insufficient memory to all
100. ber of bytes required to represent the static field type TABLE 6 15 indicated by the type item values The values item represents a byte array containing the initial values of the static field array The number of entries in the values array is equal to the size in bytes of the type indicated by the type item The size in bytes of each type is shown in TABLE 6 15 default_value_count The default_value_count item indicates the number of bytes required to initialize the set of static fields represented in segment 3 of the static field image as described in TABLE 6 14 These static fields are primitive types initialized to default values The number of bytes required to initialize each static field type is equal to the size in bytes of the type as shown in TABLE 6 15 non_default_value_count The non_default_value_count item represents the number bytes in the non_default_values array This value is equal to the number of bytes in segment 4 of the static field image as described in TABLE 6 14 These static fields are primitive types initialized to non default values non_default_values The non_default_values item represents an array of bytes of non default initial values This is the exact image of segment 4 of the static field image as described in TABLE 6 14 The number of entries in the non_default_values array for each static field type is equal to the size in bytes of the type as shown in TABLE 6 15 The value of a boolean type is
101. boolean 3 1 numeric 3 1 primitive 3 1 reference 3 1 reference 3 1 returnAddress 3 1 supported 3 5 unsupported 2 4 U union notation in CAP files 6 1 UnknownError 2 22 unrecoverable virtual machine errors 7 2 UnsatisfiedLinkError 2 22 V values reference 3 1 verification file 1 4 VerifyError 2 22 virtual machine 1 2 virtual machine errors 7 2 virtual methods 2 6 4 9 VirtualMachineError 2 22 void 2 7 volatile 2 4 WwW while 2 7 wide 2 19 word abstract storage unit 3 2 Index 7 Index 8 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008
102. by adding the field token value to the size of an instance of the immediate superclass However this method is not required by this specification A Java Card virtual machine may define any mapping from token value to offset into an instance 7 72 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 value word1 value word2 gt Description The currently executing method must be an instance method that was invoked using the invokevirtual invokeinterface or invokespecial instruction The local variable at index 0 must contain a reference objectref to the currently executing method s this parameter The unsigned index is used as an index into the constant pool of the current package Section 3 5 Frames on page 3 3 The constant pool item at the index must be of type CONSTANT_InstanceFieldref Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT_VirtualMethodref and CONSTANT_SuperMethodref on page 6 18 a reference to a class and a field token The class of objectref must not be an array If the field is protected and it is a member of a superclass of the current class and the field is not declared in the same package as the current class then the class of objectref must be either the current class or a subclass of the current class If the field is final it must be declared in the current class The item must resolve to a field with a type that matches t as follows m a field must be
103. by the execution of an instruction that instruction must not throw any runtime exceptions except for instances of System Exception Notes Comments not strictly part of the specification of an instruction are set aside as notes at the end of the description Each cell in the instruction format diagram represents a single 8 bit byte The instruction s mnemonic is its name Its opcode is its numeric representation and is given in both decimal and hexadecimal forms Only the numeric representation is actually present in the Java Card virtual machine code in a CAP file Keep in mind that there are operands generated at compile time and embedded within Java Card virtual machine instructions as well as operands calculated at run time and supplied on the operand stack Although they are supplied from several different areas all these operands represent the same thing values to be operated upon by the Java Card virtual machine instruction being executed By implicitly taking many of its operands from its operand stack rather than representing them explicitly in its compiled code as additional operand bytes register numbers etc the Java Card virtual machine s code stays compact Some instructions are presented as members of a family of related instructions sharing a single description format and operand stack diagram As such a family of instructions includes several opcodes and opcode mnemonics only the family mnemonic appe
104. byte2 Forms checkcast 148 0x94 Stack objectref gt objectref Description Chapter 7 Java Card Virtual Machine Instruction Set 7 17 The unsigned byte atype is a code that indicates if the type against which the object is being checked is an array type or a class type It must take one of the following values or zero TABLE 7 2 Array Values Array Type atype l _BOOLEAN 10 TT_BYTE Ti IT_SHORT 12 IT_INT 13 T_REFERENCE 14 If the value of atype is 10 11 12 or 13 the values of the indexbyte1 and indexbyte2 must be zero and the value of atype indicates the array type against which to check the object Otherwise the unsigned indexbyte1 and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbyte1 lt lt 8 indexbyte2 The item at that index in the constant pool must be of type CONSTANT _Classref Section 6 7 1 CONSTANT_Classref on page 6 17 a reference to a class or interface type The reference is resolved If the value of atype is 14 the object is checked against an array type that is an array of object references of the type of the resolved class If the value of atype is zero the object is checked against a class or interface type that is the resolved class The objectref must be of type reference If objectref is null or can be cast to the specifie
105. cates the beginning of the active range while the active_length item indicates the number of bytes contained in the active range end_offset is defined as start_offset plus active_length The start_offset item and end_offset are byte offsets into the info item of the Method Component The value of the start_offset must be a valid offset into a bytecodes array of a method_info structure to an opcode of an instruction The value of the end_offset either must be a valid offset into a bytecodes array of the same method_info structure to an opcode of an instruction or must be equal to the method s bytecode count the length of the bytecodes array of the method_info structure The value of the start_offset must be less than the value of the end_offset The start_offset is inclusive and the end_offset is exclusive that is the exception handler must be active while the execution address is within the interval start_offset end_offset stop_bit The stop_bit item indicates whether the active range try block of this exception handler is contained within or is equal to the active range of any succeeding exception_handler_info structures in this exception_handlers array At the Java source level this indicates whether an active range is nested within another or has at least one succeeding exception handler associated with the same range The latter occurs when there is at least one succeeding catch block or a finally block The stop_bit item i
106. ce that is implemented by a public class cannot define any fields m A package visible interface cannot be extended by an interface with public access visibility Typesafe Enums The Java Card platform language subset does not support the enumerated type facility and the keyword enum Enhanced for Loop The Java Card platform language subset does not support the enhanced for loop language construct Support for the enhanced for loop construct requires support for array indexing using the integer data type The Java Card platform only supports array indexing using the short data type Chapter 2 A Subset of the Java Virtual Machine 2 3 22 12 2 2 1 3 2 4 Varargs The Java Card platform language subset does not support variable length argument lists The variable length argument construct requires the compiler to generate code that creates a new array object each time a variable length argument array method is invoked thereby causing implicit memory allocations in Java Card runtime memory heap Runtime Visible Metadata Annotations The Java Card platform does not support this language feature which lets you introduce meta data information into the runtime environment to be accessed reflectively The Java Card platform does not support reflection Assertions The Java Card runtime does not provide runtime support for statements in the Java programming language called assertions that are used to test assumptions about program
107. ception 2 21 llegalThreadStateException 2 21 load 7 46 load_ lt n gt 7 46 lookupswitch 7 47 H H Be H HHHH implements 2 7 import 2 7 import component 6 13 import component of a CAP file 6 13 import_component structure of a CAP file 6 13 imul 7 49 IncompatibleClassChangeError 2 21 IndexOutOfBoundsException 2 21 ineg 7 49 initialization 3 3 class 2 11 instance initialization methods 3 3 instanceof 2 7 7 50 instances 2 10 InstantiationError 2 21 InstantiationException 2 20 instruction set 3 4 7 1 7 3 instructions 1 4 by opcode mnemonic 8 4 by opcode value 8 1 int 2 7 3 1 integer data type 2 8 interface 2 7 interface initialization methods 3 4 interface_info structure 6 27 interfaces 2 9 remote 2 12 InternalError 2 22 InterruptedException 2 20 invokeinterface 7 52 invokespecial 7 54 invokestatic 7 55 invokevirtual 7 56 ior 7 58 irem 7 58 ireturn 7 59 ishl 7 60 ishr 7 61 istore 7 61 istore_ lt n gt 7 62 isub 7 63 itableswitch 7 63 items 5 1 items in CAP files 6 1 iushr 7 65 ixor 7 65 J JAR files 5 2 as CAP file container 4 2 6 3 Java Card API classes 1 5 applet 1 3 file formats 4 1 Index 4 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 RE 1 5 RE context 3 3 Remote Method Invocation RMI 2 12 RMI 2 12 parameters 2 13 return values 2 13 Runtime Environment 1 5
108. ch package In addition a unique AID is assigned for each applet in the package The package AID and the default AID for each applet defined in the package are specified in the CAP file They are supplied to the converter when the CAP file is generated an acronym for Application Protocol Data Unit as defined in ISO 7816 4 an acronym for Application Programming Interface The API defines calling conventions by which an application program accesses the operating system and other services within the context of this document a Java Card applet which is the basic unit of selection context functionality and security in Java Card technology a person creating an applet using Java Card technology P 8 PP 8 8y context of a package that contains currently active applet the mechanism that prevents unauthorized accesses to objects in contexts other than currently active context see library package the logical channel on which the applet instance is either the active applet instance or will become the active applet instance Glossary 1 atomic operation atomicity ATR basic logical channel big endian binary compatibility bytecode CAD CAP file CAP file component card session an operation that either completes in its entirety or no part of the operation completes at all state in which a particular operation is atomic Atomicity of data updates guarantee that data are not corrupted in case of power loss
109. ched If the value is of type byte or type boolean it is sign extended to a short The value is pushed onto the operand stack Runtime Exception If objectref is null the getfield_ lt t gt instruction throws a NullPointerException Notes In some circumstances the getfield_ lt t gt instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If a virtual machine does not support the int data type the getfield_i instruction will not be available getfield_ lt t gt _this Fetch field from current object Format getfield_ lt t gt _this index Forms getfield_a_this 173 Oxad getfield_b_this 174 Oxae getfield_s_this 175 Oxaf getfield_i_this 176 Oxb0 Stack 5 The offset may be computed by adding the field token value to the size of an instance of the immediate superclass However this method is not required by this specification A Java Card virtual machine may define any mapping from token value to offset into an instance Chapter 7 Java Card Virtual Machine Instruction Set 7 23 Value OR o gt value word1 value word2 Description The currently executing method must be an
110. chine Instruction Set A Java Card virtual machine instruction consists of an opcode specifying the operation to be performed followed by zero or more operands embodying values to be operated upon This chapter gives details about the format of each Java Card virtual machine instruction and the operation it performs 7 1 Assumptions The Meaning of Must The description of each instruction is always given in the context of Java Card virtual machine code that satisfies the static and structural constraints of Chapter 6 The CAP File Format In the description of individual Java Card virtual machine instructions we frequently state that some situation must or must not be the case The value2 must be of type int The constraints of Chapter 6 The CAP File Format guarantee that all such expectations will in fact be met If some constraint a must or must not in an instruction description is not satisfied at run time the behavior of the Java Card virtual machine is undefined 7 1 7 2 Reserved Opcodes In addition to the opcodes of the instructions specified later this chapter which are used in Java Card CAP files see Chapter 6 The CAP File Format two opcodes are reserved for internal use by a Java Card virtual machine implementation If Sun Microsystems Inc extends the instruction set of the Java Card virtual machine in the future these reserved opcodes are guaranteed not to
111. ck The dup_x instruction must not be used unless the ranges of words 1 through m and words m 1 through n each contain either a 16 bit data type two 16 bit data types a 32 bit data type a 16 bit data type and a 32 bit data type in either order or two 32 bit data types Notes Except for restrictions preserving the integrity of 32 bit data types the dup_x instruction operates on untyped words ignoring the types of data they contain If a virtual machine does not support the int data type the permissible values for m are 1 or 2 and permissible values for n are 0 and m through m 2 dup2 Duplicate top two operand stack words Format dup2 Forms dup2 62 0x3e Stack word2 word1 gt word2 word1 word2 word1 Description The top two words on the operand stack are duplicated and pushed onto the operand stack in the original order The dup2 instruction must not be used unless each of word1 and word2 is a word that contains a 16 bit data type or both together are the two words of a single 32 bit datum Chapter 7 Java Card Virtual Machine Instruction Set 7 21 7 9 20 7 22 Notes Except for restrictions preserving the integrity of 32 bit data types the dup2 instruction operates on untyped words ignoring the types of data they contain getfield_ lt t gt Fetch field from object Format getfield_ lt t gt index Forms getfield_a 131 0x83 getfield_b 132 0x84 g
112. contains an entry for each public class and public interface defined in this package Furthermore for each public class there is an entry for each public or protected static field defined in that class for each public or protected static method defined in that class and for each public or protected constructor defined in that class Final static fields of primitive types compile time constants are not included If this CAP file includes an Applet Component Section 6 5 Applet Component on page 6 12 the Export Component includes entries only for all public interfaces that are shareable An interface is shareable if and only if it is the javacard framework Shareable interface or implements directly or indirectly that interface Elements in the Export Component reference elements in the Class Component Section 6 8 Class Component on page 6 22 Method Component Section 6 9 Method Component on page 6 36 and Static Field Component Section 6 10 Static Field Component on page 6 42 No other component in this CAP file references the Export Component The Export Component is represented by the following structure export_component ul tag u2 size ul class_count class_export_info u2 class_offset ul static_field_count ul static_method_count u2 static_field_offsets static_field_count u2 static_method_offsets static_method_count class_exports class_count The items of the export_compo
113. d array type or the resolved class or interface type the operand stack is unchanged otherwise the checkcast instruction throws a ClassCastException The following rules are used to determine whether an objectref that is not null can be cast to the resolved type if S is the class of the object referred to by objectref and T is the resolved class array or interface type checkcast determines whether objectref can be cast to type T as follows m If S is a class type then a If T is a class type then S must be the same class as T or S must be a subclass of T a If T is an interface type then S must implement interface T m If S is an interface type then 3 When both S and T are arrays of reference types this algorithm is applied recursively using the types of the arrays namely SC and TC In the recursive call S which was SC in the original call may be an interface type This rule can only be reached in this manner Similarly in the recursive call T which was TC in the original call may be an interface type 7 18 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 007 a If Tis a class type then T must be Object Section 2 2 2 4 Classes on page 2 7 a If Tis an interface type T must be the same interface as S or a superinterface of S m If Sis an array type namely the type SC that is an array of components of type SC then a If Tis a class type then T must be Obj
114. d descriptor t type Chapter 7 Java Card Virtual Machine Instruction Set 7 71 7 5 76 The width of a field in a class instance is determined by the field type specified in the instruction The item is resolved determining the field offset The objectref which must be of type reference and the value are popped from the operand stack If the field is of type byte or type boolean the value is truncated to a byte The field at the offset from the start of the object referenced by objectref is set to the value Runtime Exception If objectref is null the putfield_ lt t gt instruction throws a NullPointerException Notes In some circumstances the putfield_ lt t gt instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If a virtual machine does not support the int data type the putfield_i instruction will not be available putfield_ lt t gt _this Set field in current object Format putfield_ lt t gt _this index Forms putfield_a_this 181 Oxb5 putfield_b_this 182 Oxb6 putfield_s_this 183 Oxb7 putfield_i_this 184 Oxb8 Stack Value gt OR 10 The offset may be computed
115. d exclusion d exportation americaines y compris mais de maniere non exclusive la liste de personnes qui font objet d un ane de ne pas participer d une facon directe ou indirecte aux exportations des produits ou des services qui sont regi par la legislation americaine en matiere de controle des exportations et la liste de ressortissants specifiquement designes sont rigoureusement interdites LA DOCUMENTATION EST FOURNIE EN L ETAT ET TOUTES AUTRES CONDITIONS DECLARATIONS ET GARANTIES EXPRESSES OU TACITES SONT FORMELLEMENT EXCLUES DANS LA MESURE AUTORISEE PAR LA LOI APPLICABLE Y COMPRIS NOTAMMENT TOUTE GARANTIE IMPLICITE RELATIVE A LA QUALITE MARCHANDE A L APTITUDE A UNE UTILISATION PARTICULIERE OU A L ABSENCE DE CONTREFACON 4 Adobe PostScript Contents Preface xvii Introduction 1 1 1 1 Motivation 1 1 1 2 The Java Card Virtual Machine 1 2 1 3 Java Language Security 1 4 1 4 Java Card Runtime Environment Security 1 5 A Subset of the Java Virtual Machine 2 1 2 1 Why a Subset is Needed 2 1 2 2 Java Card Platform Language Subset 2 1 2 2 1 Unsupported Items 2 2 2 2 1 1 Unsupported Features 2 2 2 2 1 2 Keywords 2 4 2 2 1 3 Unsupported Types 2 4 2 2 1 4 Classes 2 5 2 2 2 Supported Items 2 5 2 2 2 1 Features 2 5 2 2 2 2 Keywords 2 7 2 2 2 3 Types 2 7 2 2 2 4 Classes 2 7 2 2 3 Optionally Supported Items 2 8 2 2 3 1 Integer Data Type 2 8 2 2 3 2 Object Deletion Mechanism 2 8 2 2 4 Limitations of the Java Card Virtual Machine
116. d must be less than 65536 This limit is far greater than the limit imposed by the maximum size of methods Section 2 2 4 4 Methods on page 2 10 If a program contains a lookupswitch instruction that uses keys of type int that program will require the optional int instructions Section 2 2 3 1 Integer Data Type on page 2 8 Otherwise key values must be in the range 32768 to 32767 2 18 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 2 3 0 2 3 3 1 tableswitch The bytecode can contain at most 65536 cases This limit is far greater than the limit imposed by the maximum size of methods Section 2 2 4 4 Methods on page 2 10 If a program does not use the optional int instructions Section 2 2 3 1 Integer Data Type on page 2 8 the values of the high and low operands must both be at least 32768 and at most 32767 wide The wide bytecode can only be used with an iinc instruction Exceptions The Java Card platform provides full support for the Java platform s exception mechanism Users can define throw and catch exceptions just as in the Java platform The Java Card platform also makes use of the exceptions and errors defined in The Java Language Specification An updated list of the Java platform s exceptions is provided in the JDK software documentation Not all of the Java platform s exceptions are supported in the Java Card platform Exceptions related t
117. d then high low 1 further signed 16 bit offsets The value low must be less than or equal to high The high low 1 signed 16 bit offsets are treated as a 0 based jump table Each of the signed 16 bit values is constructed from two unsigned bytes as bytel lt lt 8 byte2 Each of the signed 32 bit values is constructed from four unsigned bytes as bytel lt lt 24 byte2 lt lt 16 byte3 lt lt 8 byte4 The index must be of type int and is popped from the stack If index is less than low or index is greater than high then a target address is calculated by adding default to the address of the opcode of this itableswitch instruction Otherwise the offset at position index low of the jump table is extracted The target address is calculated by adding that offset to the address of the opcode of this itableswitch instruction Execution then continues at the target address The target addresses that can be calculated from each jump table offset as well as the one calculated from default must be the address of an opcode of an instruction within the method that contains this itableswitch instruction Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Notes If a virtual machine does not support the int data type the itableswitch instruction will not be available 7 5 67 iushr Logical shift right int Format iushr Forms iushr 82 0x52 Stack valuel word1
118. dex is indexbyte1 lt lt 8 indexbyte2 The constant pool item at that index must be of type CONSTANT_VirtualMethodref Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT _VirtualMethodref and CONSTANT_SuperMethodref on page 6 18 a reference to a class and a virtual method token The specified method is resolved The method must not be lt init gt an instance initialization method or lt clinit gt a class or interface initialization method Finally if the resolved method is protected and it is a member of a superclass of the current class and the method is not declared in the same package as the current class then the class of objectref must be either the current class or a subclass of the current class The resolved method reference includes an unsigned index into the method table of the resolved class and an unsigned byte nargs that must not be zero The objectref must be of type reference The index is an unsigned byte that is used as an index into the method table of the class of the type of objectref If the objectref is an array type then the method table of class Object Section 2 2 2 4 Classes on page 2 7 is used The table entry at that index includes a direct reference to the method s code and modifier information The objectref must be followed on the operand stack by nargs 1 words of arguments where the number of words of arguments and the type and order of the values they represent must be consistent
119. e 2 15 Methods In method_info structures the supported access flags are ACC_PUBLIC ACC_PRIVATE ACC_PROTECTED ACC_STATIC ACC_FINAL and ACC_ABSTRACT The remaining components of method_info structures are fully supported Attributes The attribute_info structure is supported The Code ConstantValue Exceptions LocalVariableTable Synthetic InnerClasses RuntimeInvisibleAnnotations RuntimeInvisibleParameterAnnotations and Deprecated attributes are supported 2 9 2 Bytecode Subset The following sections detail the bytecodes that are either supported or unsupported in the Java Card platform For more details refer to Chapter 7 Java Card Virtual Machine Instruction Set 2 16 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 2 3 2 1 2 3 2 2 Unsupported Bytecodes TABLE 2 5 lconst_ lt 1 gt lload fload_ lt n gt daload dstore lastore ladd fsub dmul lrem fneg lushr i21 12f d2i lcomp dcmpg monitorenter jsr_w Unsupported Bytecode fconst_ lt f gt fload dload_ lt n gt caload lstore_ lt n gt fastore fadd dsub ldiv frem dneg land i2f 12d d21 fcmpl lreturn monitorexit Supported Bytecodes TABLE 2 6 nop sipush aload aaload astore aastore Supported Bytecodes aconst_null ldc iload_ lt n gt baload istore_ lt n gt bastore dconst_ lt d gt dload laload lstore fstore_ lt n gt dastore dadd
120. e Throughout this document these additional features are designated as Java Card RE specific The basic runtime security feature imposed by the Java Card RE enforces isolation of applets using what is called an applet firewall The applet firewall prevents the objects that were created by one applet from being used by another applet This prevents unauthorized access to both the fields and methods of class instances as well as the length and contents of arrays Isolation of applets is an important security feature but it requires a mechanism to allow applets to share objects in situations where there is a need to interoperate The Java Card RE allows such sharing using the concept of shareable interface objects These objects provide the only way an applet can make its objects available for use by other applets For more information about using shareable interface objects see the description of the interface javacard framework Shareable in the Application Programming Interface Java Card Platform Version 3 0 specification Some descriptions of firewall related features make reference to the Shareable interface The applet firewall also protects from unauthorized use the objects owned by the Java Card RE itself The Java Card RE can use mechanisms not reflected in the Java Card API to make its objects available for use by applets A full description of the Java Card RE related isolation and sharing features can be found in the Runtime Environme
121. e operand stack If a smul instruction overflows then the result is the low order bits of the mathematical product as a short If overflow occurs then the sign of the result may not be the same as the sign of the mathematical product of the two values 7 5 96 sneg Negate short 7 88 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Format sneg Forms sneg 72 0x4b Stack Value gt result Description The value must be of type short It is popped from the operand stack The short result is the arithmetic negation of value value The result is pushed onto the operand stack For short values negation is the same as subtraction from zero Because the Java Card virtual machine uses two s complement representation for integers and the range of two s complement values is not symmetric the negation of the maximum negative short results in that same maximum negative number Despite the fact that overflow has occurred no exception is thrown For all short values x x equals x 1 7 5 97 sor Boolean OR short Format sor Forms sor 85 0x55 Stack value1 value2 gt result Description Chapter 7 Java Card Virtual Machine Instruction Set 7 89 Both valuel and value2 must be of type short The values are popped from the operand stack A short result is calculated by taking the bitwise inclusive OR of valuel and value2 The resu
122. e Format 4 2 4 1 3 JAR File Container 4 2 AID based Naming 4 3 4 2 1 The AID Format 4 3 4 2 2 AID Usage 44 Token based Linking 4 5 4 3 1 Externally Visible Items 4 5 4 3 2 Private Tokens 4 5 4 3 3 The Export File and Conversion 4 6 4 3 4 References External and Internal 4 6 4 3 5 Installation and Linking 4 7 Contents v 4 4 4 5 4 3 6 Token Assignment 4 7 4 3 7 Token Details 4 7 4 3 7 1 Package 4 8 4 3 7 2 Classes and Interfaces 4 8 4 3 7 3 Static Fields 4 8 4 3 7 4 Static Methods and Constructors 4 8 4 3 7 5 Instance Fields 4 9 4 3 7 6 Virtual Methods 4 9 4 3 7 7 Interface Methods 4 10 Binary Compatibility 4 11 Package Versions 4 13 4 5 1 Assigning 4 13 4 5 2 Linking 4 13 5 The Export File Format 5 1 5 1 5 2 5 3 5 4 5 5 5 6 5 7 5 8 5 9 5 10 Export File Name 5 2 Containment in a JAR File 5 2 Ownership 5 2 Hierarchies Represented 5 3 Export File 5 3 Constant Pool 5 5 5 6 1 CONSTANT Package 5 5 5 6 2 CONSTANT _Classref 5 7 5 6 3 CONSTANT_Integer 5 7 5 64 CONSTANT _Utf 8 5 8 Classes and Interfaces 5 9 Fields 5 12 Methods 5 14 Attributes 5 16 vi Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 5 10 1 ConstantValue Attribute 5 16 The CAP File Format 6 1 6 1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9 Component Model 6 2 6 1 1 Containment in a JAR File 6 3 6 1 2 Defining New Components 6 4 Installation 6 5 Header Compon
123. e Reference Location Component Section 6 11 Reference Location Component on page 6 46 references all constant pool indices contained in the Method Component No other CAP file components reference the Method Component The Method Component is represented by the following structure method_component ul tag u2 size ul handler_count exception_handler_info exception_handlers handler_count method_info methods The items in the method_component structure are as follows tag The tag item has the value COMPONENT_Method 7 size The size item indicates the number of bytes in the method_component structure excluding the tag and size items The value of the size item must be greater than zero handler_count The handler_count item represents the number of entries in the exception_handlers array Valid values are between 0 and 255 inclusive exception_handlers The exception_handlers item represents an array of 8 byte exception_handler_info structures Each exception_handler_info structure represents a catch or finally block defined in a method of this package Entries in the exception_handlers array are sorted in ascending order by the the offset to the handler of the exception handler Smaller offset values occur first in the array This ordering constraint ensures that the first match found when searching for an exception handler is the correct match Chapter6 The CAP File Format 6 37 6 9 1 6 38 Th
124. e current frame Section 3 5 Frames on page 3 3 The local variable at index must contain a short The value in the local variable at index is pushed onto the operand stack 7 5 93 sload_ lt n gt Load short from local variable Format sload_ lt n gt Forms sload_0 28 0x1c sload_1 29 0x1d sload_2 30 0x1e sload_3 31 0x1f Stack a gt Value Description The lt n gt must be a valid index into the local variables of the current frame Section 3 5 Frames on page 3 3 The local variable at lt n gt must contain a short The value in the local variable at lt n gt is pushed onto the operand stack Notes Each of the sload_ lt n gt instructions is the same as sload with an index of lt n gt except that the operand lt n gt is implicit 7 86 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 94 slookupswitch Access jump table by key match and jump Format slookupswitch defaultbyte1 defaultbyte2 npairs1 npairs2 match offset pairs Pair Format matchbyte1 matchbyte2 offsetbyte1 offsetbyte2 Forms slookupswitch 117 0x75 Stack iey Key gt Description A slookupswitch instruction is a variable length instruction Immediately after the slookupswitch opcode follow a signed 16 bit value default an unsigned 16 bit value npairs and then npairs pairs Each pair consi
125. e low five bits of value2 The result is pushed onto the operand stack Notes This is equivalent even if overflow occurs to multiplication by 2 to the power s The shift distance actually used is always in the range 0 to 31 inclusive as if value2 were subjected to a bitwise logical AND with the mask value 0x1f If a virtual machine does not support the int data type the ishl instruction will not be available Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 62 ishr Arithmetic shift right int Format ishr Forms ishr 80 0x50 Stack valuel word1 value1 word2 value2 word1 value2 word2 gt result word1 result word2 Description Both valuel and value2 must be of type int The values are popped from the operand stack An int result is calculated by shifting valuel right by s bit positions with sign extension where s is the value of the low five bits of value2 The result is pushed onto the operand stack Notes The resulting value is value1 2s where s is value2 amp Ox1f For nonnegative valuel this is equivalent even if overflow occurs to truncating int division by 2 to the power s The shift distance actually used is always in the range 0 to 31 inclusive as if value2 were subjected to a bitwise logical AND with the mask value 0x1f If a virtual machine does not support the int data type the ishr instruction will not be available 7 5 6
126. e of the local variable Class types are fully qualified for example Ljavacard framework Applet start_pc Chapter6 The CAP File Format 6 67 The index of the first bytecode in which the variable is in scope and valid length Number of bytecodes in which the variable is in scope and valid The value of start_pc length will be either the index of the next bytecode after the valid range or the first index beyond the end of the bytecode array line_table Contains the 1ine_info structures that map bytecode instructions of this method to lines in the class s source file Each line_info item represents a mapping of a range of bytecode instructions to a particular line in the source file that contains the method The range of instructions is from start_pc to end_pc inclusive start_pc and end_pc represent a zero based byte offset within the method The source_line is the one based line number in the source file The structure is defined as follows line_info u2 start_pc u2 end_pc u2 source_line The items in the line_info structure are defined as follows start_pc The byte offset of the first bytecode in the range of instructions end_pc The byte offset of the last operand of the last bytecode in the range of instructions source_line Line number in the source file 6 68 Virtual Machine Specification Java Card Platform v3 0 Classic Edition March 2008 CHAPTER 7 Java Card Virtual Ma
127. e to an opcode of an instruction and must be less than the value of the method s bytecode count catch_type_index If the value of the catch_type_index item is non zero it must be a valid index into the constant_pool array of the Constant Pool Component Section 6 7 Constant Pool Component on page 6 14 The constant_pool entry at that index must be a CONSTANT_Classref_info structure representing the class of the exception caught by this exception_handlers array entry If the exception_handlers table entry represents a finally block the value of the catch_type_index item is zero In this case the exception handler is called for all exceptions that are thrown within the start_offset and end_offset range The order of constants in the constant pool is constrained such that all entries referenced by catch_type_index items that represent catch block not finally blocks are located at non zero entries 6 9 2 method_info The method_info structure is defined as follows method_info method_header_info method_header ul bytecodes The items in the method_info structure are as follows method_header The method_header item represents either a method_header_info or an extended_method_header_info structure method_header_info ul bitfield bit 4 flags 6 40 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 bit 4 max_stack ul bitfield bit 4 nar
128. e_desc The type_desc item represents a table of variable length type_descriptor structures These descriptors represent the types of fields and signatures of methods For a description of the type_descriptor structure see Section 6 8 1 type_descriptor on page 6 24 6 14 Debug Component This section specifies the format for the Debug Component The Debug Component contains all the metadata necessary for debugging a package on a suitably instrumented Java Card virtual machine It is not required for executing Java Card programs in a non debug environment The Debug Component references the Class Component Section 6 8 Class Component on page 6 22 Method Component Section 6 9 Method Component on page 6 36 and Static Field Component Section 6 10 Static Field Component on page 6 42 No components reference the Debug Component The Debug Component is represented by the following structure Chapter6 The CAP File Format 6 59 debug_component ul tag u2 size u2 string_count utf8_info strings_table string_count u2 package_name_index u2 class_count class_debug_info classes class_count The items in the debug_component structure are defined as follows tag The tag item has the value COMPONENT_Debug 12 size The number of bytes in the component excluding the tag and size items The value of size must be greater than zero string_count The number of strings in the strings_table tab
129. ect If Tis an array type namely the type TC an array of components of type TC then one of the following must be true TC and SC are the same primitive type Section 3 1 Data Types and Values on page 3 1 TC and SC are reference types Section 3 1 Data Types and Values on page 3 1 with type SC assignable to TC by these rules a If Tis an interface type T must be one of the interfaces implemented by arrays Runtime Exception If objectref cannot be cast to the resolved class array or interface type the checkcast instruction throws a ClassCastException Notes The checkcast instruction is fundamentally very similar to the instanceof instruction It differs in its treatment of null its behavior when its test fails checkcast throws an exception instanceof pushes a result code and its effect on the operand stack In some circumstances the checkcast instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If a virtual machine does not support the int data type the value of atype may not be 13 array type T_INT dup Duplicate top operand stack word 4 This version of the Java Card vir
130. ed If the value of atype is 14 the object is checked against an array type that is an array of object references of the type of the resolved class If the value of atype is zero the object is checked against a class or interface type that is the resolved class The objectref must be of type reference It is popped from the operand stack If objectref is not null and is an instance of the resolved class array or interface the instanceof instruction pushes a short result of 1 on the operand stack Otherwise it pushes a short result of 0 The following rules are used to determine whether an objectref that is not null is an instance of the resolved type if S is the class of the object referred to by objectref and T is the resolved class array or interface type instanceof determines whether objectref is an instance of T as follows m IfS is a class type then a If Tis a class type then S must be the same class as T or S must be a subclass of T a If Tis an interface type then S must implement interface T m If S is an interface type then 8 When both S and T are arrays of reference types this algorithm is applied recursively using the types of the arrays namely SC and TC In the recursive call S which was SC in the original call may be an interface type This rule can only be reached in this manner Similarly in the recursive call T which was TC in the original call may be an interface type Chapter 7 Java Card Virtu
131. em of a CONSTANT_StaticFieldref_info structure has the value CONSTANT_StaticFieldref 5 The tag item of a CONSTANT_StaticMethodref_info structure has the value CONSTANT_StaticMethodref 6 static_field_ref and static_method_ref The static_field_ref and static_method_ref item represents a reference to a static field or static method respectively Static method references include references to static methods constructors and private virtual methods If the referenced item is defined in this package the structure represents an internal_ref and the high bit of the structure is zero If the referenced item is defined in another package the structure represents an external_ref and the high bit of the structure is one internal_ref The internal_ref item represents a reference to a static field or method defined in this package The items in the structure are padding The padding item is equal to 0 offset The offset item of a CONSTANT_StaticFieldref_info structure represents a 16 bit offset into the Static Field Image defined by the Static Field component Section 6 10 Static Field Component on page 6 42 to this static field The offset item of a CONSTANT_StaticMethodref_info structure represents a 16 bit offset into the info item of the Method Component Section 6 9 Method Component on page 6 36 to a method_info structure The method_info structure must represent the referenced method external_ref
132. en one of the following must be true TC and SC are the same primitive type Section 3 1 Data Types and Values on page 3 1 TC and SC are reference types Section 3 1 Data Types and Values on page 3 1 with type SC assignable to TC by these rules a If T is an interface type T must be one of the interfaces implemented by arrays Runtime Exceptions If arrayref is null aastore throws a NullPointerException Otherwise if index is not within the bounds of the array referenced by arrayref the aastore instruction throws an ArrayIndexOutOfBoundsException Otherwise if arrayref is not null and the actual type of value is not assignment compatible with the actual type of the component of the array aastore throws an ArrayStoreException Notes 1 When both S and T are arrays of reference types this algorithm is applied recursively using the types of the arrays namely SC and TC In the recursive call S which was SC in the original call may be an interface type This rule can only be reached in this manner Similarly in the recursive call T which was TC in the original call may be an interface type 2 This version of the Java Card virtual machine does not support multi dimensional arrays Therefore neither SC or TC can be an array type Chapter 7 Java Card Virtual Machine Instruction Set 7 7 In some circumstances the aastore instruction may throw a SecurityException if the current context Section 3 4 Co
133. ent 6 6 Directory Component 6 9 Applet Component 6 12 Import Component 6 13 Constant Pool Component 6 14 6 7 1 CONSTANT_Classref 6 17 6 7 2 CONSTANT_InstanceFieldref CONSTANT_VirtualMethodref and CONSTANT_SuperMethodref 6 18 6 7 3 CONSTANT_StaticFieldref and CONSTANT_StaticMethodref 6 20 Class Component 6 22 6 8 1 type_descriptor 6 24 6 8 2 interface_info and class_info 6 27 6 8 2 1 interface_info and class_info Shared Items 6 28 6 8 2 2 interface_info Items 6 29 6 8 2 3 class_info Items 6 29 6 8 2 4 implemented_interface_info 6 33 6 8 2 5 remote_interface_info 6 34 Method Component 6 36 6 9 1 exception_handler_info 6 38 6 9 2 method_info 6 40 Contents vii 6 10 6 11 6 12 6 13 6 14 Static Field Component 6 42 Reference Location Component 6 46 Export Component 6 49 Descriptor Component 6 51 6 13 1 class_descriptor_info 6 52 6 13 2 field_descriptor_info 6 54 6 13 3 method_descriptor_info 6 56 6 13 4 type_descriptor_info 6 58 Debug Component 6 59 6 14 1 The class_debug_info Structure 6 61 6 14 1 1 The field_debug_info Structure 6 63 6 14 1 2 Themethod_debug_info Structure 6 65 7 Java Card Virtual Machine Instruction Set 7 1 7 1 Assumptions The Meaning of Must 7 1 7 2 Reserved Opcodes 7 2 7 3 Virtual Machine Errors 7 2 7 4 Security Exceptions 7 3 7 5 The Java Card Virtual Machine Instruction Set 7 3 7 5 1 aaload 7 5 7 5 2 aastore 7 6 7 5 3 aconst_null 7 8 7 5 4 aload 7 8 Z
134. ent true and 0 to represent false 5 6 4 CONSTANT_Utf 8 The CONSTANT_Utf 8_info structure is used to represent constant string values UTF 8 strings are encoded in the same way as described in The Java Virtual Machine Specification 4 4 7 The CONSTANT_Utf 8_info structure is CONSTANT _Utf8_info ul tag u2 length ul bytes length The items of the CONSTANT_Utf 8_info structure are the following tag The tag item has the value of CONSTANT_Utf 8 1 length The value of the Length item gives the number of bytes in the bytes array not the length of the resulting string The strings in the CONSTANT_Utf 8_info structure are not null terminated 5 8 Virtual Machine Specification Java Card Platform v3 0 Classic Edition March 2008 bytes The bytes array contains the bytes of the string No byte may have the value byte 0 or byte 0xF0 byte OxFF 5 7 Classes and Interfaces Each class and interface is described by a variable length class_info structure The format of this structure is class_info ul token u2 access_flags u2 name_index u2 export_supers_count u2 supers export_supers_count ul export_interfaces_count u2 interfaces export_interfaces_count u2 export_fields_count field_info fields export_fields_count u2 export_methods_count method_info methods export_methods_count The items of the class_info structure are as follows token The value of the token
135. er than that of the invoker memory used for storing the fixed program of the card A smart card s ROM contains operating system routines as well as permanent data and user applications No power is needed to hold data in this kind of memory ROM cannot be written to after the card is manufactured Writing a binary image to the ROM is called masking and occurs during the chip manufacturing process see Java Card Runtime Environment Java Card RE an interface that defines a set of shared methods These interface methods can be invoked from an applet in one context when the object implementing them is owned by an applet in another context Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 shareable interface object SIO smart card terminal thread transaction transient object verification word an object that implements the shareable interface a card that stores and processes information through the electronic circuits embedded in silicon in the substrate of its body Unlike magnetic stripe cards smart cards carry both processing power and information They do not require access to remote databases at the time of a transaction a Card Acceptance Device that is typically a computer in its own right and can integrate a card reader as one of its components In addition to being a smart card reader a terminal can process data exchanged between itself and the smart card the basic
136. ere are two consequences of this ordering constraint First a handler that is nested with the active range try block of another handler occurs first in the array Second when multiple handlers are associated with the same active range they are ordered as they occur in a method This is consistent with the ordering constraints defined for Java class files An example is shown below CODE EXAMPLE 6 1 Exception Handler Example try try Satch NullPointerException e first catch ception e second finally third try catch Barr cares ead e fourth methods The methods item represents a table of variable length method_info structures Each entry represents a method declared in a class of this package lt clinit gt methods and interface method declaration are not included all other methods including non interface abstract methods are exception_handler_info The exception_handler_info structure is defined as follows exception_handler_info u2 start_offset u2 bitfield bit 1 stop_bit bit 15 active_length u2 handler_offset u2 catch_type_index Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The items in the exception_handler_info structure are as follows start_offset active_length The start_offset and active_length pair indicate the active range try block an exception handler The start_offset item indi
137. erfaces on page 4 8 of the referenced class or interface It has the value of the class token of the class as defined in the Export file of the imported package padding The padding item has the value zero It is present to make the size of a CONSTANT_Classref_info structure the same as all other constants in the constant_pool array 6 7 2 CONSTANT InstanceFieldref CONSTANT _VirtualMethodref and CONSTANT _SuperMethodref References to instance fields and virtual methods are represented by similar structures CONSTANT _InstanceFieldref_info ul tag class_ref class ul token CONSTANT _VirtualMethodref_info ul tag class_ref class ul token 6 18 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 CONSTANT _SuperMethodref_info ul tag class_ref class ul token The items in these structures are as follows tag The tag item of a CONSTANT_InstanceFieldref_info structure has the value CONSTANT_InstanceFieldref 2 The tag item of a CONSTANT_VirtualMethodref_info structure has the value CONSTANT_VirtualMethodref 3 The tag item of a CONSTANT_SuperMethodref_info structure has the value CONSTANT_SuperMethodref 4 class The class item represents the class associated with the referenced instance field virtual method or super method invocation It is a class_ref structure Section 6 7 1 CONSTANT_Classref on page 6 17 If the refe
138. ermine the version of the CAP file format If a CAP file has the major version number of M and minor version number of m the version of the CAP file s format is M m A change in the major version number indicates a major incompatibility change one that requires a fundamentally different Java Card virtual machine A Java Card virtual machine is not required to support CAP files with different major version numbers A Java Card virtual machine is required to support CAP files having a given major version number and all valid minor version numbers in the 6 6 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 range 0 through some particular minor_version where a valid minor version number is a minor version number that has been defined in a version of the Java Card virtual machine specification In this specification the major version of the CAP file format has the value 2 and the minor version has the value 2 Only Sun Microsystems Inc may define the meaning and values of new CAP file format versions flags The flags item is a mask of modifiers that apply to this package The flags modifiers are shown in the following table TABLE 6 4 CAP File Package Flags Flags Value ACC_INT 0x01 ACC_EXPORT 0x02 ACC_APPLET 0x04 The ACC_INT flag has the value of one if the Java int type is used in this package The int type is used if one or more of the following is present m A param
139. es Chapter 7 Java Card Virtual Machine Instruction Set 7 11 In some circumstances the arraylength instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the array referenced by arrayref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 7 5 9 astore Store reference into local variable Format astore index Forms astore 40 0x28 Stack objectref gt Description The index is an unsigned byte that must be a valid index into the local variables of the current frame Section 3 5 Frames on page 3 3 The objectref on the top of the operand stack must be of type returnAddress or of type reference The objectref is popped from the operand stack and the value of the local variable at index is set to objectref Notes The astore instruction is used with an objectref of type returnAddress when implementing Java s finally keyword The aload instruction cannot be used to load a value of type returnAddress from a local variable onto the operand stack This asymmetry with the astore instruction is intentional 7 5 10 astore lt n gt Store reference into local variable 7 12 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 911 Format
140. es and interfaces are not assigned tokens Static Fields All externally visible static fields in a package are assigned public static field tokens The tokens for all externally visible static fields in a class are numbered consecutively starting at zero Static fields token values must be in the range from 0 to 255 inclusive The ordering of static field tokens is not specified Package visible and private static fields are not assigned tokens In addition no tokens are assigned for final static fields that are initialized to primitive compile time constants as these fields are never represented as fields in CAP files Static Methods and Constructors All externally visible static methods and constructors in a package are assigned public static method tokens Constructors are included in this category because they are statically bound Static method token values must be in the range from 0 to 255 inclusive The tokens for all the externally visible static methods and constructors in a class are numbered consecutively starting at zero The ordering of static method tokens is not specified Package visible and private static methods as well as package visible and private constructors are not assigned tokens Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 4 3 7 5 4 3 7 6 Instance Fields All instance fields defined in a package are assigned either public or private instance field tokens The
141. esented as a single file The component file names are enumerated in TABLE 6 2 These names are not case sensitive TABLE 6 2 CAP File Component File Names Component Type File Name COMPONENT_Header Header cap COMPONENT_Directory IDirectory cap COMPONENT_Applet Applet cap ICOMPONENT_Import Import cap COMPONENT_ConstantPool CConstantPool cap COMPONENT_Class Class cap COMPONENT_Method Method cap COMPONENT_StaticField StaticField cap COMPONENT_ReferenceLocation RefLocation cap ICOMPONENT_Export Export cap ICOMPONENT_Descriptor Descriptor cap ICOMPONENT_Debug Debug cap All CAP file components are stored in a JAR file As described in Section 4 1 3 JAR File Container on page 4 2 the path to the CAP file component files in a JAR file consists of a directory called javacard that is in a subdirectory representing the package s directory For example the CAP file component files of the package Chapter6 The CAP File Format 6 3 6 1 2 6 4 javacard framework are located in the subdirectory javacard framework javacard Other files including other CAP files may also reside in a JAR file that contains CAP file component files The JAR file format provides a vehicle suitable for the distribution of CAP file components It is not intended or required that the JAR file format be used as the load file format for loading CAP file components onto a
142. est is to verify the contents of a CAP file on the device as it is downloaded or after it is downloaded This option might only be feasible in the largest of devices However some subset of verification might be possible even on smaller devices Other options rely on some combination of one or more of physical security of the installation terminal a cryptographically enforced chain of trust from the source of the CAP file and pre download verification of the contents of a CAP file Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The Java Card platform standards say as little as possible about CAP file installation and security policies Since smart cards must serve as secure processors in many different systems with different security requirements it is necessary to allow a great deal of flexibility to meet the needs of smart card issuers and users 1 4 Java Card Runtime Environment Security The standard runtime environment for the Java Card platform is the Java Card Runtime Environment Java Card RE The Java Card RE consists of an implementation of the Java Card virtual machine along with the Java Card API classes While the Java Card virtual machine has responsibility for ensuring Java language level security the Java Card RE imposes additional runtime security requirements on devices that implement the Java Card RE which results in a need for additional features on the Java Card virtual machin
143. et 7 15 If arrayref is null bastore throws a NullPointerException Otherwise if index is not within the bounds of the array referenced by arrayref the bastore instruction throws an ArrayIndexOutOfBoundsException Notes In some circumstances the bastore instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the array referenced by arrayref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 7 5 14 bipush Push byte Format bipush byte Forms bipush 18 0x12 Stack o gt value word1 value word2 Description The immediate byte is sign extended to an int and the resulting value is pushed onto the operand stack Note If a virtual machine does not support the int data type the bipush instruction will not be available 7 5 15 bspush Push byte 7 16 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Format bspush byte Forms bspush 16 0x10 Stack o gt value Description The immediate byte is sign extended to a short and the resulting value is pushed onto the operand stack 7 5 16 checkcast Check whether object is of given type Format checkcast atype indexbyte1 index
144. eter to a method of type int A parameter to a method of type int array a A local variable of type int a A local variable of type int array a A field of type int A field of type int array a An instruction of type int or a An instruction of type int array Otherwise the ACC_INT flag has the value of 0 The ACC_EXPORT flag has the value of one if an Export Component Section 6 12 Export Component on page 6 49 is included in this CAP file Otherwise it has the value of 0 The ACC_APPLET flag has the value of one if an Applet Component Section 6 5 Applet Component on page 6 12 is included in this CAP file Otherwise it has the value of 0 All other bits in the flags item not defined in TABLE 6 4 are reserved for future use Their values must be zero package Chapter 6 The CAP File Format 6 7 The package item describes the package defined in this CAP file It is represented as a package_info structure package_info ul minor_version ul major_version ul AID_length ul AID AID_length The items in the package_info structure are as follows minor_version major_version The minor_version and major_version items are the minor and major version numbers of this package These values uniquely identify the particular implementation of this package and indicate the binary compatibility between packages See Section 4 5 Package Versions on page 4 13 for a description of assigning and using pac
145. etfield_s 133 0x85 getfield_i 134 0x86 Stack objectref gt Value OR objectref gt value word1 value word2 Description The objectref which must be of type reference is popped from the operand stack The unsigned index is used as an index into the constant pool of the current package Section 3 5 Frames on page 3 3 The constant pool item at the index must be of type CONSTANT _InstanceFieldref Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT_VirtualMethodref and CONSTANT_SuperMethodref on page 6 18 a reference to a class and a field token The class of objectref must not be an array If the field is protected and it is a member of a superclass of the current class and the field is not declared in the same package as the current class then the class of objectref must be either the current class or a subclass of the current class The item must resolve to a field with a type that matches t as follows m a field must be of type reference Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 0 21 m b field must be of type byte or type boolean m s field must be of type short m i field must be of type int The width of a field in a class instance is determined by the field type specified in the instruction The item is resolved determining the field offset The value at that offset into the class instance referenced by objectref is fet
146. evel constraints on static field initialization it is expected that reasonable Java compilers will m Inline constants in the bytecodes that reference static final primitive fields that are initialized in the declaration statement m Produce only the following bytecodes a load a value on the stack iconst_ m1 0 5 b s lipush ldc ldc_w aconst_null a create an array newarray byte short boolean int a duplicate items on the stack dup a store values in arrays or static fields b i slastore putstatic a return from method return Chapter 2 A Subset of the Java Virtual Machine 2 11 22 95 2 2 6 2 2 6 1 2 2 6 2 2 12 Multiselectable Applets Restrictions Applets that implement the javacard framework Multiselectable interface are called multiselectable applets For more details on multiselection please see the Runtime Environment Specification Java Card Platform Version 3 0 All applets within a package shall be multiselectable or none shall be Java Card Platform Remote Method Invocation RMI Restrictions This section defines the subset of the RMI system that is supported by Java Card platform RMI Java Card RMI Remote Classes and Remote Interfaces A class is remote if it or any of its superclasses implements a remote interface A remote interface is an interface which satisfies the following requirements m The interface name is java rmi Remote or the interface extends directly or indirectl
147. evious implementation The minor version assigned to the new implementation must be greater than the minor version of the previous implementation Linking Both an export file and a CAP file contain the major and minor version numbers of the package described When a CAP file is installed on a Java Card technology enabled device a resident image of the package is created and the major and minor version numbers are recorded as part of that image When an export file is used during preparation of a CAP file the version numbers indicated in the export file are recorded in the CAP file During installation references from the package of the CAP file being installed to an imported package can be resolved only when the version numbers indicated in the export file used during preparation of the CAP file are compatible with the version numbers of the resident image They are compatible when the major version numbers are equal and the minor version of the export file is less than or equal to the minor version of the resident image Chapter 4 Binary Representation 4 13 4 14 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 CHAPTER 9 The Export File Format This chapter describes the export file format Compliant Java Card Converters must be capable of producing and consuming all export files that conform to the specification provided in this chapter An export file consists of a stream of 8 bit bytes
148. f structure is defined as part of the CONSTANT_Classref_info structure Section 6 7 1 CONSTANT_Classref on page 6 17 interface_count The interface_count item represents the number of entries in the interfaces array For an interface interface_count is always set to zero field_count The ield_count item represents the number of entries in the fields array If this class_descriptor_info structure represents an interface the value of the field_count item is equal to zero Chapter6 The CAP File Format 6 53 6 13 2 6 54 Static final fields of primitive types are not represented as fields in a CAP file but instead these compile time constants are placed inline in bytecode sequences The field_count item does not include static final field of primitive types defined by this class method_count The method_count item represents the number of entries in the methods array interfaces The interfaces item represents an array of interfaces implemented by this class The elements in the array are class_ref structures indicating the location of the interface_info structure in the Class Component Section 6 8 Class Component on page 6 22 The class_ref structure is defined as part of the CONSTANT_Classref_info structure Section 6 7 1 CONSTANT_Classref on page 6 17 fields The fields item represents an array of field_descriptor_info structures Each field declared by this class is represented in the arra
149. f the invoker Any other values on the operand stack of the current method are discarded The virtual machine then reinstates the frame of the invoker and returns control to the invoker 7 5 100 sshl Shift left short Format sshl Forms sshl 77 0x4d Stack valuel1 value2 gt result Description Both valuel and value2 must be of type short The values are popped from the operand stack A short result is calculated by shifting value1 left by s bit positions where s is the value of the low five bits of value2 The result is pushed onto the operand stack Notes Chapter 7 Java Card Virtual Machine Instruction Set 7 91 7 5 101 This is equivalent even if overflow occurs to multiplication by 2 to the power s The shift distance actually used is always in the range 0 to 31 inclusive as if value2 were subjected to a bitwise logical AND with the mask value 0x1f The mask value of 0x1f allows shifting beyond the range of a 16 bit short value It is used by this instruction however to ensure results equal to those generated by the Java instruction ishl sshr Arithmetic shift right short Format sshr Forms sshr 79 0x4f Stack valuel value2 gt result Description Both valuel and value2 must be of type short The values are popped from the operand stack A short result is calculated by shifting valuel right by s bit positions with sign extension where s is the v
150. faces implemented by superclasses An interface can inherit from at most 14 superinterfaces Chapter 2 A Subset of the Java Virtual Machine 2 9 2 2 4 3 2 2 4 4 2 10 Static Fields A class in an applet package can have at most 256 public or protected static non final fields A class in a library package can have at most 255 public or protected static non final fields There is no limit on the number of static final fields constants declared in a class Static Methods A class in an applet package can have at most 256 public or protected static methods A class in a library package can have at most 255 public or protected static methods Objects Methods A class can implement a maximum of 128 public or protected instance methods and a maximum of 128 instance methods with package visibility These limits include inherited methods Class Instances Class instances can contain a maximum of 255 fields where an int data type is counted as occupying two fields These limits include inherited fields Arrays Arrays can hold a maximum of 32767 components Methods The maximum number of variables that can be used in a method is 255 This limit includes local variables method parameters and in the case of an instance method invocation a reference to the object on which the instance method is being invoked meaning this An int data type is counted as occupying two local variables Virtual Machine Specification Java
151. ferenced is a constructor or a private instance method In these cases the method invoked is fully known when the cap file is created In the cases of virtual method and super method references the method invoked is dependent upon an instance of a class and its hierarchy both of which may be partially unknown when the car file is created 6 16 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 6 7 1 The first entry in the constant pool can not be an exception handler class that is referenced by a catch_type_index of an exception_handler_info structure In such a case the value of the catch_type_index would be equal to 0 but the value of 0 ina catch_type_index is reserved to indicate an exception_handler_info structure that describes a finally block CONSTANT Classref The CONSTANT_Classref_info structure is used to represent a reference to a class or an interface The class or interface may be defined in this package or in an imported package CONSTANT _Classref_info ul tag union u2 internal_class_ref ul package_token ul class_token external_class_ref class_ref ul padding The items in the CONSTANT_Classref_info structure are the following tag The tag item has the value CONSTANT_Classref 1 class_ref The class_ref item represents a reference to a class or interface If the class or interface is defined in this package the structure represents an internal_class_ref
152. fferent major version numbers A Java Card virtual machine is required to support export files having a given major version number and all valid minor version numbers in the Chapter 5 The Export File Format 5 3 range 0 through some particular minor_version where a valid minor version number is a minor version number that has been defined in a version of the Java Card virtual machine specification In this specification the major version of the export file format has the value 2 and the minor version has the value 2 Only Sun Microsystems Inc may define the meaning and values of new export file format versions constant_pool_count The constant_pool_count item is a non zero positive value that indicates the number of constants in the constant pool constant_pool The constant_pool is a table of variable length structures representing various string constants class names field names and other constants referred to within the ExportFile structure Each of the constant_pool table entries including entry zero is a variable length structure whose format is indicated by its first tag byte There are no ordering constrains on entries in the constant_pool table this package The value of this_package must be a valid index into the constant_pool table The constant_pool entry at that index must be a CONSTANT_Package_info Section 5 6 1 CONSTANT_Package on page 5 5 structure representing the package defined by this
153. fo ul tag u2 name_index The items of the CONSTANT_Classref_info structure are the following tag The tag item has the value of CONSTANT_Classref 7 name_index The value of the name_index item must be a valid index into the constant_pool table The constant_pool entry at that index must be a CONSTANT_Utf 8_info Section 5 6 4 CONSTANT_Ut f8 on page 5 8 structure representing a valid fully qualified Java class or interface name This name is fully qualified since it may represent a class or interface defined in a package other than the one described in the export file As in Java class files ASCII periods that normally separate the identifiers in a class or interface name are replaced by ASCII forward slashes For example the interface name javacard framework Shareable is represented in a CONSTANT_Utf 8_info structure as javacard framework Shareable CONSTANT_Integer The CONSTANT_Integer_info structure is used to represent four byte numeric int constants Chapter 5 The Export File Format 5 7 CONSTANT _Integer_info ul tag u4 bytes The items of the CONSTANT_Integer_info structure are the following tag The tag item has the value of CONSTANT_Integer 3 bytes The bytes item of the CONSTANT_Integer_info structure contains the value of the int constant The bytes of the value are stored in big endian high byte first order The value of a boolean type is 1 to repres
154. fo item containing the content of the new component A new component file is stored in a JAR file following the same restrictions as those specified in Section 4 1 3 JAR File Container on page 4 2 That is the file containing the new component must be located in the lt package_directory gt javacard subdirectory of the JAR file and must have the extension cap Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 6 2 Installation Installing a CAP file components onto a Java Card technology enabled device entails communication between a Java Card technology enabled terminal and that device While it is beyond the scope of this specification to define a load file format or installation protocol between a terminal and a device the CAP file component order shown in TABLE 6 3 is a reference load order suitable for an implementation with a simple memory management model on a limited memory device TABLE6 3 Reference Component Install Order Component Type COMPONENT_Header COMPONI a NT_Directory COMPONI NT_Import COMPONI Ka NT_Applet COMPONI NT_Class COMPONI fsa Z T_Method COMPONI ea Z T_StaticField COMPON I 2 l z _Export COMPONI Ka NT_ConstantPool COMPONI By NT_ReferenceLocation COMPONENT_Descriptor optional The componen
155. format class_info Items super_class_ref The super_class_ref item of the class_info structure is a class_ref structure representing the superclass of this class The class_ref structure is defined as part of the CONSTANT_Classref_info structure Section 6 7 1 CONSTANT_Classref on page 6 17 Chapter6 The CAP File Format 6 29 The super_class_ref item has the value of OxFFFF only if this class does not have a superclass Otherwise the value of the super_class_ref item is limited only by the constraints of the class_ref structure declared_instance_size The declared_instance_size item of the class_info structure represents the number of 16 bit cells required to represent the instance fields declared by this class It does not include instance fields declared by superclasses of this class Instance fields of type int are represented in two 16 bit cells while all other field types are represented in one 16 bit cell first_reference_token The first_reference_token item of the class_info structure represents the instance field token Section 4 3 7 5 Instance Fields on page 4 9 value of the first reference type instance field defined by this class It does not include instance fields defined by superclasses of this class If this class does not define any reference type instance fields the value of the first_reference_token is 0xFF Otherwise the value of the first_reference_token item must be within the range of the set
156. fter initialization Field access and modifier flags are defined in the same way and with the same restrictions as described in The Java Virtual Machine Specification Since all fields represented in an export file are either public or protected exactly one of the ACC_PUBLIC or ACC_PROTECTED flag must be set The Java Card virtual machine reserves all other flag values Their values must be Zero 4 Although Java compilers ordinarily replace references to final static fields of primitive types with primitive constants this functionality is not required Chapter5 The Export File Format 5 13 5 9 5 14 name_index The value of the name_index item must be a valid index into the constant_pool table The constant_pool entry at that index must be a CONSTANT_Utf 8_info Section 5 6 4 CONSTANT_Ut f8 on page 5 8 structure representing a valid Java field name stored as a simple not fully qualified name that is as a Java identifier descriptor_index The value of the descriptor_index item must be a valid index into the constant_pool table The constant_pool entry at that index must be a CONSTANT_Ut 8_info Section 5 6 4 CONSTANT_Ut 8 on page 5 8 structure representing a valid Java field descriptor Representation of a field descriptor in an export file is the same as in a Java class file See the specification described in The Java Virtual Machine Specification 4 3 2 If this field is a
157. ge Chapter6 The CAP File Format 6 19 The token item of the CONSTANT_SuperMethodref_info structure represents the virtual method token Section 4 3 7 6 Virtual Methods on page 4 9 of the referenced method Unlike in the CONSTANT_VirtualMethodref_info structure the virtual method token is defined within the scope of the hierarchy of the superclass of the class indicated by the class item If the referenced method is public or protected the high bit of the token item is zero If the referenced method is package visible the high bit of the token item is one In the latter case the class item must represent a reference to a class defined in this package and at least one superclass of the class that contains a definition of the virtual method must also be defined in this package 6 7 3 CONSTANT StaticFieldref and CONSTANT StaticMethodref References to static fields and methods are represented by similar structures CONSTANT _StaticFieldref_info ul tag union ul padding u2 offset internal_ref ul package_token ul class_token ul token external_ref static_field_ref aw CONSTANT_StaticMethodref_info ul tag union ul padding u2 offset internal_ref ul package_token ul class_token ul token external_ref static_method_ref The items in these structures are as follows tag 6 20 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The tag it
158. gs Constant Type Value CONSTANT_String 8 CONSTANT_Float 4 CONSTANT_Long 5 CONSTANT_Double 6 Fields In field_info structures the access flags ACC_VOLATILE ACC_TRANSIENT and ACC_ENUM are not supported Methods In method_info structures the access flags ACC_SYNCHRONIZED ACC_STRICT ACC_NATIVE and ACC_VARARGS are not supported 2 14 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 2 3 1 2 Supported in Class Files ClassFile All items in the ClassFile structure are supported Field Descriptors Field descriptors may contain BaseType characters B I S and Z as well as any ObjectType ArrayType descriptors for arrays of a single dimension may also be used Method Descriptors All forms of method descriptors are supported Constant Pool Constant pool table entry with the following tag values are supported TABLE 2 4 Supported Java Constant Pool Tags Constant Type Value ICONSTANT_Class 7 CONSTANT_Fieldref 9 ICONSTANT_Methodref 10 CONSTANT_InterfaceMethodref 11 CONSTANT_Integer 3 ICONSTANT_NameAndType 12 ICONSTANT_Utf8 1 Fields In field_info structures the supported access flags are ACC_PUBLIC ACC_PRIVATE ACC_PROTECTE D ACC_STATIC and ACC_FINAL The remaining components of field_info structures are fully supported Chapter 2 A Subset of the Java Virtual Machin
159. gs bit 4 max_ locals extended_method_header_info ul bitfield bit 4 flags bit 4 padding ul max_stack ul nargs ul max_locals The items of the method_header_info and extended_method_header_info structures are as follows flags The flags item is a mask of modifiers defined for this method Valid flag values are shown in the following table TABLE 6 13 CAP File Method Flags Flags Values ACC_EXTENDED 0x8 ACC_ABSTRACT 0x4 The value of the ACC_EXTENDED flag must be one if the method_header is represented by an extended_method_header_info structure Otherwise the value must be zero The value of the ACC_ABSTRACT flag must be one if this method is defined as abstract In this case the bytecodes array must be empty If this method is not abstract the value of the ACC_ABSTRACT flag must be zero All other flag values are reserved Their values must be zero padding The padding item has the value of zero This item is only defined for the extended_method_header_info structure max_stack Chapter6 The CAP File Format 6 41 6 10 The max_stack item indicates the maximum number of words required on the operand stack during execution of this method Stack entries of type int are represented in two words while all others are represented in one word See Section 3 2 Words on page 3 2 nargs The nargs item indicates the number of words required to re
160. he invoked method returns 7 5 58 ior Boolean OR int Format ior Forms ior 86 0x56 Stack value1 word1 value1 word2 value2 word1 value2 word2 gt result word1 result word2 Description Both value1 and value2 must be of type int The values are popped from the operand stack An int result is calculated by taking the bitwise inclusive OR of valuel and value2 The result is pushed onto the operand stack Notes If a virtual machine does not support the int data type the ior instruction will not be available 7 5 59 irem Remainder int Format irem Forms irem 74 Ox4a 7 58 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 60 Stack valuel word1 value1 word2 value2 word1 value2 word2 gt result word1 result word2 Description Both value1 and value2 must be of type int The values are popped from the operand stack The int result is the value of the Java expression valuel value1 value2 value2 The result is pushed onto the operand stack The result of the irem instruction is such that a b b a b is equal to a This identity holds even in the special case that the dividend is the negative int of largest possible magnitude for its type and the divisor is 1 the remainder is 0 It follows from this rule that the result of the remainder operation can be negative only if the dividend is negative and can
161. he value COMPONENT_ReferenceLocation 9 size The size item indicates the number of bytes in the reference_location_component structure excluding the tag and size items The value of the size item must be greater than zero byte_index_count The byte_index_count item represents the number of elements in the offsets_to_byte_indices array offsets_to_byte_indices The of fsets_to_byte_indices item represents an array of 1 byte jump offsets into the info item of the Method Component to each 1 byte constant_pool array index Each entry represents the number of bytes or distance between the current index to the next If the distance is greater than or equal to 255 then there are n entries equal to 255 in the array where n is equal to the distance divided by 255 The nth entry of 255 is followed by an entry containing the value of the distance modulo 255 Chapter6 The CAP File Format 6 47 An example of the jump offsets in an of fsets_to_byte_indices array is shown in the following table TABLE 6 17 One byte Reference Location Example Instruction Offset to Operand Jump Offset lgetfield_a 0 10 10 putfield_b 2 65 55 255 255 getfield_s 1 580 5 255 putfield_a 0 835 0 getfield_i 3 843 8 All 1 byte constant_pool array indices in the Method Component must be represented in of fsets_to_byte_indices array byte2_index_count The byte2_index_count item represents the number of elements
162. hecked 2 20 uncatchable 2 19 uncaught 2 19 export component of a CAP file 6 49 export file 1 4 4 1 Glossary 4 attributes in 5 16 classes in 5 9 constant pool tags 5 5 conversion 4 6 fields in 5 12 format 3 4 4 2 5 1 interfaces in 5 9 methods in 5 14 name 5 2 ownership 5 2 structure elements 5 3 extends 2 7 externally visible items 4 5 F field_debug_info 6 63 field_descriptor_info 6 54 fields 2 14 2 15 descriptors 2 14 2 15 static 2 10 file formats Java Card platform 4 1 file verification 1 4 final 2 7 finalization 2 2 finally 2 7 float 2 4 for 2 7 frames 3 3 G garbage collection 3 2 getfield_ lt t gt 7 22 getfield_ lt t gt _this 7 23 getfield_ lt t gt _w 7 25 getstatic_ lt t gt 7 26 goto 2 7 7 27 goto_w 7 28 H header component of CAP file 6 6 header_component structure 6 6 heap 3 2 high bit in CAP files 6 1 Index 3 l i2b 7 29 i2s 7 29 iadd 7 30 iaload 7 31 iand 7 32 iastore 7 32 icmp 7 33 iconst_ lt i gt 7 34 idiv 7 34 if 2 7 if lt cond gt 7 39 if lt cond gt _w 7 40 if_acmp 7 35 if_acmp lt cond gt _w 7 36 if_scmp lt cond gt 7 37 if_scmp lt cond gt _w 7 38 ifnonnull 7 41 ifnonnull_w 7 41 ifnull 7 42 ifnull_w 7 43 iinc 7 43 iinc_w 7 44 iipush 7 45 IllegalAccessError 2 21 llegalAccessException 2 20 llegalArgumentException 2 21 llegalMonitorStateException 2 21 llegalStateEx
163. hod_table_base item is zero package_method_table_count The package_method_table_count item of the class_info structure indicates the number of entries in the package_virtual_method_table array If this class does not define any override methods the minimum valid value of package_method_table_count item is the number of package visible virtual methods declared by this class If this class defines one or more package visible override methods the minimum valid value of package_method_table_count item is the value of the largest package visible virtual method token minus the value of the smallest package visible virtual override method token plus one The maximum valid value of the package_method_table_count item is the value of the largest package visible method token plus one Any value for the package_method_table_count item between the minimum and maximum specified here are valid However the value must correspond to the number of entries in the package_virtual_method_table public_virtual_method_table The public_virtual_method_table item of the class_info structure represents an array of public and protected virtual methods These methods can be invoked on an instance of this class The public_virtual_method_table Chapter6 The CAP File Format 6 31 array includes methods declared or defined by this class It may also include methods declared or defined by any or all of its superclasses The value of an index into thi
164. hods The high bit of the byte containing an interface method token is always set to zero to indicate it is a public token The ordering of interface method tokens is not specified Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 4 4 Binary Compatibility In the Java programming language the granularity of binary compatibility can be between classes since binaries are stored in individual class files In Java Card systems Java packages are processed as a single unit and therefore the granularity of binary compatibility is between packages In Java Card systems the binary of a package is represented in a CAP file and the API of a package is represented in an export file In a Java Card system a change to a type in a Java package results in a new CAP file A new CAP file is binary compatible with equivalently does not break compatibility with a preexisting CAP file if another CAP file converted using the export file of the preexisting CAP file can link with the new CAP file without errors FIGURE 4 2 shows an example of binary compatible CAP files p1 and p1 The preconditions for the example are the package p1 is converted to create the p1 CAP file and p1 export file and package p1 is modified and converted to create the p1 CAP file Package p2 imports package p1 and therefore when the p2 CAP file is created the export file of p1 is used In the example p2 is converted using the original
165. hrows a NullPointerException Notes In some circumstances the getfield_ lt t gt _w instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If a virtual machine does not support the int data type the getfield_i_w instruction will not be available 7 5 23 getstatic_ lt t gt Get static field from class Format getstatic_ lt t gt indexbyte1 indexbyte2 7 The offset may be computed by adding the field token value to the size of an instance of the immediate superclass However this method is not required by this specification A Java Card virtual machine may define any mapping from token value to offset into an instance 7 26 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 24 Forms getstatic_a 123 0x7b getstatic_b 124 0x7c getstatic_s 125 0x7d getstatic_i 126 Ox7e Stack o gt value OR o gt value word1 value word2 Description The unsigned indexbytel and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is inde
166. ield_s_this tfield_s_w tstatic_a tstatic_b tstatic_i dec hex 116 74 82 52 88 58 TL39 371 143 8F 144 90 0 00 59 3B 60 3C 135 87 181 B5 177 BE 136 88 182 B6 178 B2 138 8A 184 B8 180 B4 137 89 183 B7 179 B3 127 7F 128 80 130 82 mnemonic sload_2 sload_3 slookupswitch smul sneg sor srem sreturn sshl sshr sspush sstore sstore_0 sstore_1 sstore_2 sstore_3 ssub stableswitch sushr swap_x SxOr Instructions by Opcode Mnemonic Continued dec hex 30 ST 117 69 75 85 73 120 77 79 17 41 47 48 49 50 67 115 81 64 87 29 2F 30 31 32 43 73 51 40 57 Chapter 8 Tables of Instructions 8 7 8 8 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Glossary active applet instance AID application identifier APDU API applet applet developer applet execution context applet firewall applet package assigned logical channel an applet instance that is selected on at least one of the logical channels defined by ISO 7816 a string used to uniquely identify card applications and certain types of files in card file systems An AID consists of two distinct pieces a 5 byte RID resource identifier and a 0 to 11 byte PIX proprietary identifier extension The RID is a resource identifier assigned to companies by ISO The PIX identifiers are assigned by companies A unique AID is assigned for ea
167. if and only if the interface is javacard framework Shareable interface or extends that interface directly or indirectly The ACC_SHAREABLE flag in a class_info structure indicates whether this class is shareable gt The value of this flag must be one if and only if this class or any of its superclasses implements an interface that is shareable The ACC_REMOTE flag indicates whether this class or interface is remote The value of this flag must be one if and only if the class or interface satisfies the requirements defined in Section 2 2 6 1 Remote Classes and Remote Interfaces on page 2 12 All other flag values are reserved Their values must be zero interface_count The interface_count item of the interface_info structure indicates the number of entries in the superinterfaces table item The value represents the number of direct and indirect superinterfaces of this interface Indirect superinterfaces are the set of superinterfaces of the direct superinterfaces Valid values are between 0 and 14 inclusive The interface_count item of the class_info structure indicates the number of entries in the interfaces table item The value represents the number of interfaces implemented by this class including superinterfaces of those interfaces and potentially interfaces implemented by superclasses of this class Valid values are between 0 and 15 inclusive 6 28 5 A Java Card virtual machine uses the ACC_SHAREABLE flag to im
168. ignificantly enhanced runtime environment and a new virtual machine It includes new network oriented features such as support for web applications including the Java Servlet APIs and also support for applets with extended and advanced capabilities An application written for or an implementation of the Connected Edition may use features found in the Classic Edition Therefore you will need to use the specifications for both the Classic Edition and the Connected Edition 1 1 Motivation Java Card technology enables programs written in the Java programming language to be run on smart cards and other small resource constrained devices Developers can build and test programs using standard software development tools and environments then convert them into a form that can be installed onto a Java Card technology enabled device Application software for the Java Card platform is called an applet or more specifically a Java Card applet or card applet to distinguish it from browser applets While Java Card technology enables programs written in the Java programming language to run on smart cards such small devices are far too under powered to support the full functionality of the Java platform Therefore the Java Card platform supports only a carefully chosen customized subset of the features of the Java platform This subset provides features that are well suited for writing programs for small devices and preserves the object oriented ca
169. ile including symbolic references used to dynamically link to the API class at runtime Java Card technology uses a different strategy for binary representation of programs Executable binaries and interface binaries are represented in two separate files These files are respectively called CAP files for converted applet and export files 4 1 4 1 1 4 1 2 4 1 3 4 2 Export File Format Export files are not used directly on a device that implements a Java Card virtual machine However the information in an export file is critical to the operation of the virtual machine on a device An export file can be produced by a Java Card converter when a package is converted This package s export file can be used later to convert another package that imports classes from the first package Information in the export file is included in the CAP file of the second package then is used on the device to link the contents of the second package to items imported from the first package A Java Card technology based export file Java Card export file contains the public interface information for an entire package of classes This means that an export file only contains information about the public API of a package and does not include information used to link classes within a package The name of an export file is the last portion of the package specification followed by the extension exp For example the name of the export file of
170. ile sequentially without padding or alignment Variable sized tables consisting of variable sized items are used in several CAP file data structures Although we will use C like array syntax to refer to table items the fact that tables are streams of variable sized structures means that it is not possible to directly translate a table index into a byte offset into the table A data structure referred to as an array consists of items equal in size Some items in the structures of the CAP file format are describe using a C like union notation The bytes contained in a union structure have one of the two formats Selection of the two formats is based on the value of the high bit of the structure 6 1 6 1 6 2 Component Model A Java Card CAP file consists of a set of components Each component describes a set of elements in the Java package defined or an aspect of the CAP file A complete CAP file must contain all of the required components specified in this chapter Three components are optional the Applet Component Section 6 5 Applet Component on page 6 12 Export Component Section 6 12 Export Component on page 6 49 and Debug Component Section 6 14 Debug Component on page 6 59 The Applet Component is included only if one or more Applets are defined in the package The Export Component is included only if classes in other packages may import elements in the package defined The Debug Component contains al
171. iles which include package designations Package mechanisms are used to identify and control access to classes static fields and static methods Except as noted in Access Control in Java Packages Section 2 2 1 1 Unsupported Features on page 2 2 packages in the Java Card platform are used exactly the way they are in the Java platform Dynamic Object Creation The Java Card platform programs supports dynamically created objects both class instances and arrays This is done as usual by using the new operator Objects are allocated out of the heap A Java Card virtual machine will not necessarily garbage collect objects Any object allocated by a virtual machine may continue to exist and consume resources even after it becomes unreachable See Section 2 2 3 2 Object Deletion Mechanism on page 2 8 for more information regarding support for an optional object deletion mechanism Chapter 2 A Subset of the Java Virtual Machine 2 5 Virtual Methods Since Java Card technology based objects Java Card objects are Java programming language objects invoking virtual methods on objects in a program written for the Java Card platform is exactly the same as in a program written for the Java platform Inheritance is supported including the use of the super keyword Interfaces Java Card API classes may define or implement interfaces as in the Java programming language Invoking methods on interface types works as expected
172. iload_ lt n gt Forms 7 46 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 50 iload_0 32 0x20 iload_1 33 0x21 iload_2 34 0x22 iload_3 35 0x23 Stack a gt valuel word1 value1 word2 Description Both lt n gt and lt n gt 1 must be a valid indices into the local variables of the current frame Section 3 5 Frames on page 3 3 The local variables at lt n gt and lt n gt 1 together must contain an int The value of the local variables at lt n gt and lt n gt 1 is pushed onto the operand stack Notes Each of the iload_ lt n gt instructions is the same as iload with an index of lt n gt except that the operand lt n gt is implicit If a virtual machine does not support the int data type the iload_ lt n gt instruction will not be available i1lookupswitch Access jump table by key match and jump Format ilookupswitch defaultbyte1 defaultbyte2 npairs1 npairs2 match offset pairs Pair Format matchbyte1 matchbyte2 matchbyte3 Chapter 7 Java Card Virtual Machine Instruction Set 7 47 matchbyte4 offsetbyte1 offsetbyte2 Forms ilookupswitch 118 0x76 Stack key word1 key word2 gt Description An ilookupswitch instruction is a variable length instruction Immediately after the ilookupswitch opcode follow a signed 16 bit value default an unsig
173. in the offsets_to_byte2_indices array offsets_to_byte2_indices The of fsets_to_byte2_indices item represents an array of 1 byte jump offsets into the info item of the Method Component to each 2 byte constant_pool array index Each entry represents the number of bytes or distance between the current index to the next If the distance is greater than or equal to 255 then there are n entries equal to 255 in the array where n is equal to the distance divided by 255 The nth entry of 255 is followed by an entry containing the value of the distance modulo 255 An example of the jump offsets in an of fsets_to_byte_indices array is shown in TABLE 6 17 The same example applies to the offsets_to_byte2_indices array if the instructions are changed to those with 2 byte constant_pool array indices All 2 byte constant_pool array indices in the Method Component must be represented in of fsets_to_byte2_indices array including those represented in catch_type_index items of the exception_handler_info array 6 48 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 6 12 Export Component The Export Component lists all static elements in this package that may be imported by classes in other packages Instance fields and virtual methods are not represented in the Export Component If this CAP file does not include an Applet Component Section 6 5 Applet Component on page 6 12 the Export Component
174. ined in the Export file of the imported package It has the value of the token of the referenced method 6 8 Class Component The Class Component describes each of the classes and interfaces defined in this package It does not contain complete access information and content details for each class and interface Instead the information included is limited to that required to execute operations associated with a particular class or interface without performing verification Complete details regarding the classes and interfaces defined in this package are included in the Descriptor Component Section 6 13 Descriptor Component on page 6 51 The information included in the Class Component for each interface is sufficient to uniquely identify the interface and to test whether or not a cast to that interface is valid The information included in the Class Component for each class is sufficient to resolve operations associated with instances of a class The operations include creating an instance testing whether or not a cast of the instance is valid dispatching virtual method invocations and dispatching interface method invocations Also included is sufficient information to locate instance fields of type reference including arrays 6 22 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The classes represented in the Class Component reference other entries in the Class Component in the form of supe
175. installed on a Java Card technology enabled device must also have a unique AID This AID is constructed similarly to a package AID It is a concatenation of the applet provider s RID and PIX for that applet An applet AID must not have the same value as the AID of any package or the AID of any other applet The RID of each applet in a package must be the same as the RID of the package Custom components defined in a CAP file are also identified using AIDs Like AIDs for applets and packages component AIDs are formed by concatenating a RID and a PIX Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 4 3 4 3 1 4 3 2 Token based Linking This section describes a scheme that allows downloaded software to be linked against APIs on a Java Card technology enabled device The scheme represents referenced items as opaque tokens instead of Unicode strings as are used in Java class files The two basic requirements of this linking scheme are that it allows linking on the device and that it does not require internal implementation details of APIs to be revealed to clients of those APIs Secondary requirements are that the scheme be efficient in terms of resource use on the device and have acceptable performance for linking And of course it must preserve the semantics of the Java language Externally Visible Items Classes including Interfaces in Java packages may be declared with public or package v
176. ion 6 12 Export Component on page 6 49 or Debug Component Section 6 14 Debug Component on page 6 59 it is represented in the Directory Component with size equal to zero The Directory Component also includes entries for new or custom components The Directory Component is described by the following variable length structure directory_component ul tag u2 size u2 component_sizes 12 static_field_size_info static_field_size ul import_count ul applet_count ul custom_count custom_component_info custom components custom_count The items in the directory_component structure are as follows tag The tag item has the value COMPONENT_Directory 2 size The size item indicates the number of bytes in the directory_component structure excluding the tag and size items The value of the size item must be greater than zero component_sizes Chapter6 The CAP File Format 6 9 The component_sizes item is an array representing the number of bytes in each of the components in this CAP file All of the 12 components defined in this chapter are represented in the component_sizes array The value of an index into the array is equal to the value of the tag of the component represented at that entry minus 1 The value in each entry in the component_sizes array is the same as the size item in the corresponding component It represents the number of bytes in the component excluding the tag and size items The val
177. ion for the computer to perform and any data to be used in performing the operation An instruction can be in machine language or a programming language items that are not externally visible These items are not described in a package s export file but some such items use private tokens to represent internal references See also externally visible an acronym for Java Archive file which is a file format used for aggregating many files into one a subset of the Java Platform Remote Method Invocation RMI system It provides a mechanism for a client application running on the CAD platform to invoke a method on a remote object on the card consists of the Java Card virtual machine the framework and the associated native methods a subset of the Java virtual machine which is designed to be run on smart cards and other resource constrained devices The Java Card VM acts an engine that loads Java class files and executes them with a particular set of semantics Glossary 5 Java Card RE entry point objects objects owned by the Java Card RE context that contain entry point methods These methods can be invoked from any context and allow non privileged users applets to request privileged Java Card RE system services Java Card RE entry point objects can be either temporary or permanent temporary references to temporary Java Card RE entry point objects cannot be stored in class variables instance variables or array components The J
178. isibility A class s methods and fields may be declared with public protected package or private visibility For purposes of this document we define public classes public or protected fields and public or protected methods to be externally visible from the package Each externally visible item must have a token associated with it to enable references from other packages to the item to be resolved on a device There are six kinds of items in a package that require external identification m Classes including Interfaces m Static Fields m Static Methods m Instance Fields m Virtual Methods m Interface Methods Private Tokens Items that are not externally visible are internally visible Internally visible items are not described in a package s export file but some such items use private tokens to represent internal references External references are represented by public tokens There are three kinds of items that can be assigned private tokens m Instance Fields m Virtual Methods Chapter 4 Binary Representation 4 5 4 3 3 4 3 4 4 6 m Packages The Export File and Conversion An export file contains entries for externally visible items in the package Each entry holds the item s name and its token Some entries may include additional information as well For detailed information on the export file format see Chapter 5 The Export File Format The export file is used to map names for imported items to to
179. item is the class token Section 4 3 7 2 Classes and Interfaces on page 4 8 assigned to this class or interface access flags Chapter 5 The Export File Format 5 9 The value of the access_flags item is a mask of modifiers used with class and interface declarations The access_flags modifiers are shown in the following table TABLE 5 3 Export File Class Access and Modifier Flags Name Value Meaning Used By IACC_ PUBLIC 0x0001 Is public may be Class interface accessed from outside its package IAACC_FINAL 0x0010 Is final no subclasses Class allowed IAACC_INTERFACE 0x0200 Is an interface Interface IAACC_ABSTRACT 0x0400 Is abstract may not be Class interface instantiated ACC_SHAREABLE 0x0800 Is shareable may be Class interface shared between Java Card applets ACC_REMOTE 0x1000 Is remote may be Class accessed by Java Card interface RMI The ACC_SHAREABLE flag indicates whether this class or interface is shareable A class is shareable if it implements directly or indirectly the javacard framework Shareable interface An interface is shareable if it is or extends directly or indirectly the javacard framework Shareable interface The ACC_REMOTE flag indicates whether this class or interface is remote The value of this flag must be one if and only if the class or interface satisfies the requirements defined in Section 2 2 6 1 Remote Classes and Remote
180. itive type supported by Java Card technology boolean byte short int m Any single dimension array type of an primitive type supported by Java Card technology boolean byte short int a Any remote interface type m Type void 23 Dodd Java Card VM Subset Java Card technology uses a subset of the Java virtual machine and familiarity with the Java platform is required to understand the Java Card virtual machine The items discussed in this section are not described to the level of a virtual machine specification For complete documentation on the Java virtual machine refer to the The Java Virtual Machine Specification Class File Subset The operation of the Java Card virtual machine can be defined in terms of standard Java platform class files Since the Java Card virtual machine supports only a subset of the behavior of the Java virtual machine it also supports only a subset of the standard class file format Chapter 2 A Subset of the Java Virtual Machine 2 13 2 3 1 1 Not Supported in Class Files Class Access Flags In class_info and interface_info structures the access flag ACC_ENUM is not supported Field Descriptors Field descriptors may not contain BaseType characters C D F or J ArrayType descriptors for arrays of more than one dimension may not be used Constant Pool Constant pool table entries with the following tag values are not supported TABLE 2 3 Unsupported Java Constant Pool Ta
181. k All of the elements of the new array are initialized to the default initial value for its type Runtime Exception 7 68 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 If count is less than zero the newarray instruction throws a NegativeArraySizeException Notes If a virtual machine does not support the int data type the value of atype may not be 13 array type T_INT 7 5 72 nop Do nothing Format nop Forms nop 0 0x0 Stack No change Description Do nothing 7 5 73 pop Pop top operand stack word Format pop Forms pop 59 0x3b Stack Word gt Description Chapter 7 Java Card Virtual Machine Instruction Set 7 69 The top word is popped from the operand stack The pop instruction must not be used unless the word contains a 16 bit data type Notes The pop instruction operates on an untyped word ignoring the type of data it contains 7 5 74 pop2 Pop top two operand stack words Format pop2 Forms pop2 60 0x3c Stack word2 word gt Description The top two words are popped from the operand stack The pop2 instruction must not be used unless each of word1 and word2 is a word that contains a 16 bit data type or both together are the two words of a single 32 bit datum Notes Except for restrictions preserving the integrity of 32 bit data types the pop2 instruction operates on an untyped word
182. kage version numbers AID_length The AID_length item represents the number of bytes in the AID item Valid values are between 5 and 16 inclusive AID The AID item represents the Java Card platform name of the package See ISO 7816 5 for the definition of an AID Section 4 2 AID based Naming on page 4 3 package_name The package_name item describes the name of the package defined in this CAP file It is represented as a package_name_info structure package_name_info ul name_length ul name name_length The items in the package_name_info structure are as follows name_length The name_length item is the number of bytes used in the name item to represent the name of this package in UTF 8 format The value of this item may be zero if and only if the package does not define any remote interfaces or remote classes 6 8 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 name The name item is a variable length representation of the fully qualified name of this package in UTF 8 format The fully qualified name is represented in internal form as described in Java Virtual Machine Specification Section 4 2 Directory Component The Directory Component lists the size of each of the components defined in this CAP file When an optional component is not included such as the Applet Component Section 6 5 Applet Component on page 6 12 Export Component Sect
183. kens during package conversion The Java Card converter uses these tokens to represent references to items in an imported package For example during the conversion of the class files of applet A the export file of javacard framework is used to find tokens for items in the API that are used by the applet Applet A creates a new instance of framework class OwnerPIN The framework export file contains an entry for javacard framework OwnerPIN that holds the token for this class The converter places this token in the CAP file s constant pool to represent an unresolved reference to the class The token value is later used to resolve the reference on a device References External and Internal In the context of a CAP file references to items are made indirectly through a package s constant pool References to items in other packages are called external and are represented in terms of tokens References to items in the same CAP file are called internal and are represented either in terms of tokens or in a different internal format An external reference to a class is composed of a package token and a class token Together those tokens specify a certain class in a certain package An internal reference to a class is a 15 bit value that is a pointer to the class structure s location within the CAP file An external reference to a static class member either a field or method consists of a package token a class token and a token for
184. l of the data necessary for debugging a package The content of each component defined in a CAP file must conform to the corresponding format specified in this chapter All components have the following general format component ul tag u2 size ul info Each component begins with a 1 byte tag indicating the kind of component Valid tags and their values are listed in TABLE 6 1 The size item indicates the number of bytes in the info array of the component not including the tag and size items The content and format of the info array varies with the type of component TABLE 6 1 CAP File Component Tags Component Type Value ICOMPONENT_Header 1 ICOMPONENT_Directory 2 ICOMPONENT_Applet 3 COMPONENT_Import 4 COMPONENT_ConstantPool 5 COMPONENT_Class 6 COMPONENT_Method 7 COMPONENT_StaticField 8 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 6 1 1 TABLE 6 1 CAP File Component Tags Continued Component Type Value COMPONENT_ReferenceLocation 9 COMPONENT_Export 10 ICOMPONENT_Descriptor TI ICOMPONENT_Debug 12 Sun Microsystems Inc may define additional components in future versions of this Java Card virtual machine specification It is guaranteed that additional components will have tag values between 13 and 127 inclusive Containment in a JAR File Each CAP file component is repr
185. lassNotFoundException CloneNotSupportedException TllegalAccessException TnstantiationException TnterruptedException INoSuchFieldException xl KT XL KL RK LK TX INoSuchMethodException 2 20 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 2 39 39 3 Runtime Exceptions TABLE 2 8 Support of Java Runtime Exceptions Runtime Exception Supported Not Supported ArithmeticException X ArrayStoreException X ClassCastException X IllegalArgumentException IllegalThreadStateException NumberFormatException IllegalMonitorStateException xX X X XX IllegalStateException TndexOutOfBoundsException ArrayIndexOutOfBoundsException X StringIndexOutOfBoundsException X NegativeArraySizeException NullPointerException SecurityException 2 3 3 4 Errors TABLE 2 9 Support of Java Errors Error Supported Not Supported AssertionError X LinkageError ClassCircularityError ClassFormatError ExceptionInInitializerError IncompatibleClassChangeError AbstractMethodError IllegalAccessError x KTR TK LK LK LK TX TnstantiationError Chapter 2 A Subset of the Java Virtual Machine 2 21 2 22 TABLE 2 9 Support of Java Errors Continued Error Supported Not Supported NoSuch
186. le strings_table A table of all the strings used in this component Various items that occur through this component represent unsigned two byte indices into this table Each entry in the table is a ut 8_info structure A ut 8_info structure is represented by the following structure utf8_info u2 length ul bytes length The items in the ut 8_info structure are defined as follows length The number of bytes in the string bytes The bytes of the string in UTF 8 format package_name_index 6 60 Virtual Machine Specification Java Card Platform v3 0 Classic Edition March 2008 Contains an index into the strings_table item The strings_table item entry referenced by this index must contain the fully qualified name of the package in this CAP file class_count The number of classes in the classes table classes Contains a single class_debug_info structure for each class in this package 6 14 1 The class _debug_info Structure The class_debug_info structure contains all of the debugging information for a class or interface It also contains tables of debugging information for all its classes fields and methods u2 u2 u2 u2 u2 ul u2 u2 u2 class_debug_info name_index access_flags location superclass_name_index source_file_index interface_count field_count method_count interface_names_indexes interface_count field_debug_info fields field_count
187. le by constant Chapter 7 Java Card Virtual Machine Instruction Set 7 43 Format iinc index const Forms iinc 90 0x5a Stack No change Description The index is an unsigned byte Both index and index 1 must be valid indices into the local variables of the current frame Section 3 5 Frames on page 3 3 The local variables at index and index 1 together must contain an int The const is an immediate signed byte The value const is first sign extended to an int then the int contained in the local variables at index and index 1 is incremented by that amount Notes If a virtual machine does not support the int data type the iinc instruction will not be available 7 5 46 1ine w Increment local int variable by constant Format linc_w index byte1 byte2 Forms iinc_w 151 0x97 Stack 7 44 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 No change Description The index is an unsigned byte Both index and index 1 must be valid indices into the local variables of the current frame Section 3 5 Frames on page 3 3 The local variables at index and index 1 together must contain an int The immediate unsigned bytel and byte2 values are assembled into an intermediate short where the value of the short is bytel lt lt 8 byte2 The intermediate value is then sign extended to an int const The int contained in the loc
188. lt is pushed onto the operand stack 7 5 98 srem Remainder short Format srem Forms srem 73 0x49 Stack valuel value2 gt result Description Both valuel and value2 must be of type short The values are popped from the operand stack The short result is the value of the Java expression valuel valuel value2 value2 The result is pushed onto the operand stack The result of the srem instruction is such that a b b a b is equal to a This identity holds even in the special case that the dividend is the negative short of largest possible magnitude for its type and the divisor is 1 the remainder is 0 It follows from this rule that the result of the remainder operation can be negative only if the dividend is negative and can be positive only if the dividend is positive Moreover the magnitude of the result is always less than the magnitude of the divisor Runtime Exception If the value of the divisor for a short remainder operator is 0 srem throws an ArithmeticException 7 5 99 sreturn Return short from method 7 90 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Format sreturn Forms sreturn 120 0x78 Stack Value gt empty Description The value must be of type short It is popped from the operand stack of the current frame Section 3 5 Frames on page 3 3 and pushed onto the operand stack of the frame o
189. lue word1 value word2 gt result Description The value on top of the operand stack must be of type int It is popped from the operand stack and converted to a short result by taking the low order 16 bits of the int value and discarding the high order 16 bits The result is pushed onto the operand stack Notes The i2s instruction performs a narrowing primitive conversion It may lose information about the overall magnitude of value The result may also not have the same sign as value If a virtual machine does not support the int data type the i2s instruction will not be available 7 9 28 iadd Add int Format iadd Forms iadd 66 0x42 Stack valuel word1 valuel word2 value2 word1 value2 word2 gt result word1 result word2 Description Both valuel and value2 must be of type int The values are popped from the operand stack The int result is valuel value2 The result is pushed onto the operand stack If an iadd instruction overflows then the result is the low order bits of the true mathematical result in a sufficiently wide two s complement format If overflow occurs then the sign of the result may not be the same as the sign of the mathematical sum of the two values Notes 7 30 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 29 If a virtual machine does not support the int data type the iadd instruction will not be available i
190. mbered consecutively starting at one greater than the highest numbered private virtual method token of the class s superclass If the class and its superclass are defined in different packages the tokens for the package visible introduced virtual methods in that class are numbered consecutively starting at zero If a method overrides a method implemented in the class s superclass that method uses the same token number as the method in the superclass The definition of the Java programming language specifies that overriding a package visible virtual method is only possible if both the class and its superclass are defined in the same package The high bit of the byte containing a virtual method token is always set to one to indicate it is a private token The ordering of private virtual method tokens in a class is not specified Interface Methods All interface methods defined in a package are assigned public interface method tokens as interface methods are always public Interface method token values must be in the range from 0 to 127 inclusive The tokens for all the interface methods defined in or inherited by an interface are numbered consecutively starting at zero The token value for an interface method in a given interface is unrelated to the token values of that same method in any of the interface s superinterfaces Each interface includes its own token values for all the methods inherited from super interfaces as well as its defined met
191. method_debug_info methods method_count The items in the class_debug_info structure are defined as follows name_index Contains an index into the strings_table item of the debug_component structure The strings_table entry at the indexed location must be the fully qualified name of this class access flags Chapter6 The CAP File Format 6 61 A two byte mask of modifiers that apply to this class The modifiers are TABLE 6 22 Class Access and Modifier Flags Modifier Value IACC_PUBLIC Ox0001 IAACC_FINAL 0x0010 ACC_REMOTE 0x0020 ACC_INTERFACE 0x0200 ACC_ABSTRACT 0x0400 ACC_SHAREABLE 0x0800 The ACC_SHAREABLE flag indicates whether this class or interface is shareable 8 A class is shareable if it implements directly or indirectly the javacard framework Shareable interface An interface is shareable if it is or extends directly or indirectly the javacard framework Shareable interface The ACC_REMOTE flag indicates whether this class or interface is remote The value of this flag must be one if and only if the class or interface satisfies the requirements defined in Section 2 2 6 1 Remote Classes and Remote Interfaces on page 2 12 All other class access and modifier flags are defined in the same way and with the same restrictions as described in The Java Virtual Machine Specification location The byte offset of the class_info or interface_info record for this class o
192. n Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If a virtual machine does not support the int data type the iastore instruction will not be available icmp Compare int Format icmp Forms icmp 95 0x5f Stack valuel word1 valuel word2 value2 word1 value2 word2 gt result Description Both valuel and value2 must be of type int They are both popped from the operand stack and a signed integer comparison is performed If valuel is greater than value2 the short value 1 is pushed onto the operand stack If value1 is equal to value2 the short value 0 is pushed onto the operand stack If valuel is less than value2 the short value 1 is pushed onto the operand stack Chapter 7 Java Card Virtual Machine Instruction Set 7 33 Notes If a virtual machine does not support the int data type the icmp instruction will not be available 7 5 33 iconst_ lt i gt Push int constant Format iconst_ lt i gt Forms iconst_m1 10 0x09 iconst_0 11 Oxa iconst_1 12 Oxb iconst_2 13 Oxc iconst_3 14 Oxd iconst_4 15 Oxe iconst_5 16 Oxf Stack o gt lt i gt word1 lt i gt word2 Description Push the int constant lt i gt 1 0 1 2 3 4 or 5 onto the operand stack Notes If a virtual machine does not support the int data type the iconst_ lt i gt instruction will not be available 7 5 34 idiv Divide int Format
193. n the static_field_component structure are as follows tag The tag item has the value COMPONENT_StaticField 8 size The size item indicates the number of bytes in the static_field_component structure excluding the tag and size items The value of the size item must be greater than zero image_size The image_size item indicates the number of bytes required to represent the static fields defined in this package excluding final static fields of primitive types This value is the number of bytes in the static field image The number of bytes required to represent each field type is shown in TABLE 6 15 The value of the image_size item does not include the number of bytes require to represent the initial values of array instances enumerated in the Static Field Component The value of the image_size is defined as image_size reference_count 2 default_value_count non_default_value_count reference_count The reference_count item indicates the number of reference type static fields defined in this package This is the number of fields represented in segments 1 and 2 of the static field image as described in TABLE 6 14 6 44 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The value of the reference_count item may be 0 if no reference type fields are defined in this package Otherwise it must be equal to the number of reference type fields defined array_init_count The ar
194. nc w Increment local short variable by constant Format sinc_w index byte1 byte2 Forms sinc_w 150 0x96 Stack No change Description 7 84 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 91 7 5 92 The index is an unsigned byte that must be a valid index into the local variable of the current frame Section 3 5 Frames on page 3 3 The immediate unsigned byte1 and byte2 values are assembled into a short const where the value of const is byte1 lt lt 8 byte2 The local variable at index which must contain a short is incremented by const sipush Push short Format sipush byte1 byte2 Forms sipush 19 0x13 Stack o gt valuel word1 valuel word2 Description The immediate unsigned bytel and byte2 values are assembled into a signed short where the value of the short is bytel lt lt 8 byte2 The intermediate value is then sign extended to an int and the resulting value is pushed onto the operand stack Notes If a virtual machine does not support the int data type the sipush instruction will not be available sload Load short from local variable Format sload index Chapter 7 Java Card Virtual Machine Instruction Set 7 85 Forms sload 22 0x16 Stack o gt Value Description The index is an unsigned byte that must be a valid index into the local variables of th
195. ncapsulated with a set of routines called methods which operate on the data the applet instance within the currently active context when the object is instantiated An object can be owned by an applet instance or by the Java Card RE in object oriented programming unique instances of a data structure defined according to the template provided by its class Each object has its own values for the variables belonging to its class and can respond to the messages methods defined by its class the logical channel on which an APDU command is issued the context in which an object is instantiated or created a namespace within the Java programming language that can have classes and interfaces an acronym for Proximity Coupling Device The PCD is a contactless card reader device persistent objects and their values persist from one CAD session to the next indefinitely Objects are persistent by default Persistent object values are updated atomically using transactions The term persistent does not mean there is an object oriented database on the card or that objects are serialized and deserialized just that the objects are not lost when the card loses power see AID application identifier Glossary 7 RAM random access memory reference implementation remote interface remote methods remote object RFU RID RMI ROM read only memory runtime environment shareable interface Glossary 8 temporary w
196. ncluding interfaces implemented by superclasses of this class and superinterfaces of the implemented interfaces If ACC_INTERFACE is set the strings_table entry at each indexed location must be the name of a super interface directly or indirectly extended by this interface There must be an index value present for every super interface directly or indirectly extended by this interface fields Contains ield_debug_info structures for all the fields declared by this class including static final fields of primitive types Inherited fields are not included in this array methods Contains method_debug_info structures for all the methods declared or defined in this class Inherited methods are not included in this array The field_debug_info Structure The field_debug_info structure describes a field in a class It can describe either an instance field a static field or a constant primitive final static field The contents union will have the form of a token_var if the field is an instance field a location_var if it is a static field or a const_value if it is a constant The field_debug_info structure is defined as follows field_debug_info u2 name_index u2 descriptor_index u2 access_flags union ul padl Chapter6 The CAP File Format 6 63 ul pad2 ul pad3 ul token token var u2 pad u2 location location_var u4 const_value contents The items in the field_debug_info
197. nd gt instruction 7 5 40 if lt cond gt _w Branch if short comparison with zero succeeds wide index Format if lt cond gt _w branchbyte1 branchbyte2 Forms ifeq_w 152 0x98 ifne_w 153 0x99 iflt_w 154 0x9a ifge_w 155 0x9b ifgt_w 156 0x9c ifle _w 157 0x9d Stack Value gt Description The value must be of type short It is popped from the operand stack and compared against zero All comparisons are signed The results of the comparisons are as follows m eq succeeds if and only if value 0 m ne succeeds if and only if value 1 4 0 m It succeeds if and only if value lt 0 m le succeeds if and only if value 0 m gt succeeds if and only if value gt 0 m ge succeeds if and only if value 0 7 40 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 9 41 7 5 42 If the comparison succeeds the unsigned bytes branchbyte1 and branchbyte2 are used to construct a signed 16 bit branchoffset where branchoffset is branchbyte1 lt lt 8 branchbyte2 Execution proceeds at that offset from the address of the opcode of this if lt cond gt _w instruction The target address must be that of an opcode of an instruction within the method that contains this if lt cond gt _w instruction Otherwise execution proceeds at the address of the instruction following this if lt cond gt _w instruction ifnonnull Branch if reference not null
198. ndex into the local variables of the current frame Section 3 5 Frames on page 3 3 The local variable at lt n gt must contain a reference The objectref in the local variable at lt n gt is pushed onto the operand stack Notes An aload_ lt n gt instruction cannot be used to load a value of type returnAddress from a local variable onto the operand stack This asymmetry with the corresponding astore_ lt n gt instruction is intentional Each of the aload_ lt n gt instructions is the same as aload with an index of lt n gt except that the operand lt n gt is implicit Chapter 7 Java Card Virtual Machine Instruction Set 7 9 7 5 6 Ni 7 10 anewarray Create new array of reference Format anewarray indexbyte1 indexbyte2 Forms anewarray 145 0x91 Stack count gt arrayref Description The count must be of type short It is popped off the operand stack The count represents the number of components of the array to be created The unsigned indexbyte1 and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbyte1 lt lt 8 indexbyte2 The item at that index in the constant pool must be of type CONSTANT_Classref Section 6 7 1 CONSTANT_Classref on page 6 17 a reference to a class or interface type The reference is resolved A new array with components of th
199. ned 16 bit value npairs and then npairs pairs Each pair consists of an int match and a signed 16 bit offset Each match is constructed from four unsigned bytes as matchbytel lt lt 24 matchbyte2 lt lt 16 matchbyte3 lt lt 8 matchbyte4 Each offset is constructed from two unsigned bytes as offsetbytel lt lt 8 offsetbyte2 The table match offset pairs of the ilookupswitch instruction must be sorted in increasing numerical order by match The key must be of type int and is popped from the operand stack and compared against the match values If it is equal to one of them then a target address is calculated by adding the corresponding offset to the address of the opcode of this ilookupswitch instruction If the key does not match any of the match values the target address is calculated by adding default to the address of the opcode of this ilookupswitch instruction Execution then continues at the target address The target address that can be calculated from the offset of each match offset pair as well as the one calculated from default must be the address of an opcode of an instruction within the method that contains this ilookupswitch instruction Notes The match offset pairs are sorted to support lookup routines that are quicker than linear search If a virtual machine does not support the int data type the ilookupswitch instruction will not be available 7 48 Virtual Machine Specification Java Card Platform
200. nent structure are as follows 7 The restriction on shareable functionality is imposed by the firewall as defined in the Runtime Environment Specification Java Card Platform Version 3 0 Chapter6 The CAP File Format 6 49 6 50 tag The tag item has the value COMPONENT_Export 10 size The size item indicates the number of bytes in the export_component structure excluding the tag and size items The value of the size item must be greater than zero class_count The class_count item represents the number of entries in the class_exports table The value of the class_count item must be greater than zero class_exports The class_exports item represents a variable length table of class_export_info structures If this package is a library package the table contains an entry for each of the public classes and public interfaces defined in this package If this package is an applet package the table contains an entry for each of the public shareable interfaces defined in this package An index into the table to a particular class or interface is equal to the token value of that class or interface Section 4 3 7 2 Classes and Interfaces on page 4 8 The token value is published in the Export file Section 5 7 Classes and Interfaces on page 5 9 of this package The items in the class_export_info structure are class_offset The class_offset item represents a byte offset into the info item of the Class Componen
201. ngth attribute used in the attributes table of the field_info structures A ConstantValue attribute represents the value of a final static field compile time constant that is both the ACC_STATIC and ACC_FINAL bits in the flags item of the field_info structure must be set There can be no more than one ConstantValue attribute in the attributes table of a given field_info structure The ConstantValue attribute has the format 5 16 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 ConstantValue_attribute u2 attribute_name_index u4 attribute_length u2 constantvalue_index The items of the ConstantValue_attribute structure are as follows attribute_name_index The value of the attribute_name_index item must be a valid index into the constant_pool table The constant_pool entry at that index must be a CONSTANT_Ut 8_info Section 5 6 4 CONSTANT_Ut 8 on page 5 8 structure representing the string ConstantValue attribute_length The value of the attribute_length item of a ConstantValue_attribute structure must be 2 constantvalue_index The value of the constantvalue_index item must be a valid index into the constant_pool table The constant_pool entry at that index must give the constant value represented by this attribute The constant_pool entry must be of a type CONSTANT_Integer Section 5 6 3 CONSTANT_Integer on page 5 7 Chapter5 The Export File Format 5 17
202. nk with the new version of I because this would result in the class C containing an abstract method without the class C being abstract The fact that C can not link with I means that I and I are not binary compatible 4 12 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 4 5 4 5 1 4 5 2 Package Versions Each implementation of a package in a Java Card system is assigned a pair of major and minor version numbers These version numbers are used to indicate binary compatibility or incompatibility between successive implementations of a package Assigning The major and minor versions of a package are assigned by the package provider It is recommended that the initial implementation of a package be assigned a major version of 1 and a minor version of 0 However any values may be chosen It is also recommended that when either a major or a minor version is incremented it is incremented exactly by 1 A major version must be changed when a new implementation of a package is not binary compatible with the previous implementation The value of the new major version must be greater than the major version of the previous implementation When a major version is changed the associated minor version must be assigned the value of 0 When a new implementation of a package is binary compatible with the previous implementation it must be assigned a major version equal to the major version of the pr
203. nstance of the immediate superclass However this method is not required by this specification A Java Card virtual machine may define any mapping from token value to offset into an instance Chapter 7 Java Card Virtual Machine Instruction Set 7 75 Format putstatic_ lt t gt indexbyte1 indexbyte2 Forms putstatic_a 127 0x7f putstatic_b 128 0x80 putstatic_s 129 0x81 putstatic_i 130 0x82 Stack Value gt OR value word1 value word2 gt Description The unsigned indexbytel and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbytel lt lt 8 indexbyte2 The constant pool item at the index must be of type CONSTANT_StaticFieldref Section 6 7 3 CONSTANT_StaticFieldref and CONSTANT_StaticMethodref on page 6 20 a reference to a static field If the field is final it must be declared in the current class The item must resolve to a field with a type that matches t as follows m a field must be of type reference a b field must be of type byte or type boolean s field must be of type short a i field must be of type int value must be of a type that is assignment compatible with the field descriptor t type The width of a class field is determined by the field type specified in the instruction The item is resolved determining the class field
204. nt Specification Java Card Platform Version 3 0 Chapter 1 Introduction 1 5 1 6 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 CHAPTER 2 A Subset of the Java Virtual Machine This chapter describes the subset of the Java virtual machine and language that is supported in the Java Card platform Version 3 0 2 1 Why a Subset is Needed It would be ideal if programs for smart cards could be written using all of the Java programming language but a full implementation of the Java virtual machine is far too large to fit on even the most advanced resource constrained devices available today A typical resource constrained device has on the order of 1 2K of RAM 16K of non volatile memory EEPROM or flash and 32K 48K of ROM The code for implementing string manipulation single and double precision floating point arithmetic and thread management would be larger than the ROM space on such a device Even if it could be made to fit there would be no space left over for class libraries or application code RAM resources are also very limited The only workable option is to implement Java Card technology as a subset of the Java platform 22 Java Card Platform Language Subset Applets written for the Java Card platform are written in the Java programming language They are compiled using Java compilers Java Card technology uses a subset of the Java language and familiarity with the Ja
205. nterfaces interface_count field_descriptor_info fields field_count method_descriptor_info methods method_count Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The items of the class_descriptor_info structure are as follows token The token item represents the class token Section 4 3 7 2 Classes and Interfaces on page 4 8 of this class or interface If this class or interface is package visible it does not have a token assigned In this case the value of the token item must be OxFF access flags The access_flags item is a mask of modifiers used to describe the access permission to and properties of this class or interface The access_flags modifiers for classes and interfaces are shown in the following table TABLE 6 18 CAP File Class Descriptor Flags Name Value ACC_PUBLIC 0x01 ACC_FINAL 0x10 ACC_INTERFACE 0x40 ACC_ABSTRACT 0x80 The class access and modifier flags defined in the table above are a subset of those defined for classes and interfaces in a Java class file They have the same meaning and are set under the same conditions as the corresponding flags in a Java class file All other flag values are reserved Their values must be zero this_class_ref The this_class_ref item is a class_ref structure indicating the location of the class_info structure in the Class Component Section 6 8 Class Component on page 6 22 The class_re
206. ntexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the array referenced by arrayref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 7 5 3 aconst null Push null Format aconst_null Forms aconst_null 1 0x1 Stack a gt null Description Push the null object reference onto the operand stack 7 5 4 aload Load reference from local variable Format aload index Forms aload 21 0x15 Stack gt objectref 7 8 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 5 Description The index is an unsigned byte that must be a valid index into the local variables of the current frame Section 3 5 Frames on page 3 3 The local variable at index must contain a reference The objectref in the local variable at index is pushed onto the operand stack Notes The aload instruction cannot be used to load a value of type returnAddress from a local variable onto the operand stack This asymmetry with the astore instruction is intentional aload_ lt n gt Load reference from local variable Format aload_ lt n gt Forms aload_0 24 0x18 aload_1 25 0x19 aload_2 26 0x1a aload_3 27 0x1b Stack gt objectref Description The lt n gt must be a valid i
207. nts of the package com sun framework are located in the directory com sun framework javacard An export file may also be contained in a JAR file whether that JAR file contains CAP file components or not If an export file is included it must be located in the same directory as the components for that package would be The name of a JAR file containing CAP file components is not defined as part of this specification Other files including CAP file components for another package may also reside in a JAR file that contains CAP file components 4 2 4 2 1 AID based Naming This section describes the mechanism used for naming applets and packages in Java Card CAP files and export files and custom components in Java Card CAP files Java class files use Unicode strings to name Java packages As the Java Card platform does not include support for strings an alternative mechanism for naming is provided ISO 7816 is a multipart standard that describes a broad range of technology for building smart card systems ISO 7816 5 defines the AID application identifier data format to be used for unique identification of card applications and certain kinds of files in card file systems The Java Card platform uses the AID data format to identify applets and packages AIDs are administered by the International Standards Organization ISO so they can be used as unique identifiers The AID Format This section presents a minimal description of
208. nvokeinterface instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If the current context is not the object s context and the Java Card RE permits invocation of the method the invokeinterface instruction will cause a context switch Section 3 4 Contexts on page 3 2 to the object s context before invoking the method and will cause a return context switch to the previous context when the invoked method returns 7 5 55 invokespecial Invoke instance method special handling for superclass private and instance initialization method invocations Format invokespecial indexbyte1 indexbyte2 Forms invokespecial 140 0x8c Stack objectref arg1 arg2 gt Description The unsigned indexbytel and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbytel lt lt 8 indexbyte2 If the invoked method is a private instance method or an instance initialization method the constant pool item 7 54 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008
209. o static_field_offsets The static_field_offsets item represents an array of 2 byte offsets into the static field image defined by the Static Field Component Section 6 10 Static Field Component on page 6 42 Each offset must be to the beginning of the representation of the exported static field An index into the static_field_offsets array must be equal to the token value of the field represented by that entry The token value is published in the Export file Section 5 9 Methods on page 5 14 of this package static_method_offsets The static_method_offsets item represents a table of 2 byte offsets into the info item of the Method Component Section 6 9 Method Component on page 6 36 Each offset must be to the beginning of a method_info structure The method_info structure must represent the exported static method or constructor An index into the static_method_offsets array must be equal to the token value of the method represented by that entry 6 13 Descriptor Component The Descriptor Component provides sufficient information to parse and verify all elements of the CAP file It references and therefore describes elements in the Constant Pool Component Section 6 7 Constant Pool Component on page 6 14 Class Component Section 6 8 Class Component on page 6 22 Method Component Section 6 9 Method Component on page 6 36 and Static Field Component Section 6 10 Static Field
210. o the top of the operand stack Runtime Exceptions If arrayref is null saload throws a NullPointerException Otherwise if index is not within the bounds of the array referenced by arrayref the saload instruction throws an ArrayIndexOutOfBoundsException Notes 7 80 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 In some circumstances the saload instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the array referenced by arrayref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 7 5 85 sand Boolean AND short Format sand Forms sand 83 0x53 Stack value1 value2 gt result Description Both value1 and value2 are popped from the operand stack A short result is calculated by taking the bitwise AND conjunction of value1 and value2 The result is pushed onto the operand stack 7 5 86 sastore Store into short array Format sastore Forms sastore 57 0x39 Stack arrayref index value gt Chapter 7 Java Card Virtual Machine Instruction Set 7 81 Description The arrayref must be of type reference and must refer to an array whose components are of type short The index and value must both be of type sh
211. o unsupported features are naturally not supported Class loader exceptions the bulk of the checked exceptions are not supported Note that some exceptions may be supported to the extent that their error conditions are detected correctly but classes for those exceptions will not necessarily be present in the API The supported subset is described in the tables below Uncaught and Uncatchable Exceptions In the Java platform uncaught exceptions and errors will cause the virtual machine s current thread to exit As the Java Card virtual machine is single threaded uncaught exceptions or errors will cause the virtual machine to halt Further response to uncaught exceptions or errors after halting the virtual machine is an implementation specific policy and is not mandated in this document Some error conditions are known to be unrecoverable at the time they are thrown Throwing a runtime exception or error that cannot be caught will also cause the virtual machine to halt As with uncaught exceptions implementations may take further responses after halting the virtual machine Uncatchable exceptions and Chapter 2 A Subset of the Java Virtual Machine 2 19 errors which are supported by the Java Card platform may not be reflected in the Java Card API though the Java Card platform will correctly detect the error condition 2 3 3 2 Checked Exceptions TABLE 2 7 Support of Java Checked Exceptions Exception Supported Not Supported C
212. ocate a new object it will throw a SystemException with an error code describing the error condition The Virtual Machine Specification cannot predict where resource limitations or internal errors may be encountered and does not mandate precisely when they can be reported Thus a SystemException may be thrown at any time during the operation of the Java Card virtual machine 7 2 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 4 Security Exceptions Instructions of the Java Card virtual machine throw an instance of the class SecurityException when a security violation has been detected The Java Card virtual machine does not mandate the complete set of security violations that can or will result in an exception being thrown However there is a minimum set that must be supported In the general case any instruction that de references an object reference must throw a SecurityException if the context Section 3 4 Contexts on page 3 2 in which the instruction is executing is different than the owning context Section 3 4 Contexts on page 3 2 of the referenced object The list of instructions includes the instance field get and put instructions the array load and store instructions as well as the arraylength invokeinterface invokespecial invokevirtual checkcast instanceof and athrowinstructions There are several exceptions to this general rule that allow cross context use of objec
213. oded Reference Array Type p1 c1 Nibble Value Description 0 OxE array of reference 1 Kp1 gt package token booo high bit on 3 lt c1 gt class token 4 5 0x0 padding Method signatures are encoded in the same way with the return type of the method encoded at the end of the sequence of nibbles The return type is encoded in as many nibbles as required to represent it For example TABLE 6 10 Encoded Method Signature V Nibble Nalue Description 0 0x1 void 1 0x0 padding TABLE 6 11 Encoded Method Signature Lp1 ci S Nibble Value Description 0 0x6 reference 1 lt p1 gt package token b high bit on 6 26 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 6 8 2 TABLE 6 11 Encoded Method Signature Lp1 ci S Nibble Value Description 3 lt c1 gt lass token 4 5 0x4 short interface_info and class_info The interface_info and class_info structures represent interfaces and classes respectively The two are differentiated by the value of the high bit in the structures They are defined as follows interface_info ul bitfield bit 4 flags bit 4 interface_count class_ref superinterfaces interface_count interface_name_info interface_name class_info ul bitfield bit 4 flags bit 4 interface_count class_ref super_class_ref ul declared_instance_size ul fi
214. oes is to compare it to its counterpart in the Java platform The Java virtual machine specification defines a Java virtual machine as an engine that loads Java class files and executes them with a particular set of semantics The class file is a central piece of the Java architecture and it is the standard for the binary compatibility of the Java platform The Virtual Machine Specification Java Card Platform Version 3 0 Classic Edition also defines a file format that is the standard for binary compatibility for the Java Card platform the CAP file format is the form in which software is loaded onto devices which implement a Java Card virtual machine 1 2 The Java Card Virtual Machine The role of the Java Card virtual machine is best understood in the context of the process for production and deployment of software for the Java Card platform There are several components that make up a Java Card system including the Java Card virtual machine the Converter for the Java Card platform Java Card Converter a terminal installation tool and an installation program that runs on the device as shown in FIGURE 1 1 and FIGURE 1 2 1 2 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 FIGURE 1 1 Java Card API Package Conversion Development System CAP File FIGURE 1 2 Java Card API Package Installation Terminal Device CAP File Development of a Java Card applet begins as with any other J
215. of instance field tokens of this class reference_count The reference_count item of the class_info structure represents the number of reference type instance field defined by this class It does not include reference type instance fields defined by superclasses of this class Valid values of the reference_count item are between 0 and the maximum number of instance fields defined by this class public_method_table_base The public_method_table_base item of the class_info structure is equal to the virtual method token value Section 4 3 7 6 Virtual Methods on page 4 9 of the first method in the public_virtual_method_table array If the public_virtual_method_table array is empty the value of the public_method_table_base item is equal to the public_method_table_base item of the class_info structure of this class superclass plus the public_method_table_count item of the class_info structure of this class superclass If this class has no superclass and the public_virtual_method_table array is empty the value of the public_method_table_base item is zero public_method_table_count The public_method_table_count item of the class_info structure indicates the number of entries in the public_virtual_method_table array 6 30 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 If this class does not define any public or protected override methods the minimum valid value of public_me
216. of methods defined in this package type_descriptor_info u2 constant_pool_count u2 constant_pool_types constant_pool_count type_descriptor type_desc 6 58 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The type_descriptor_info structure contains the following elements constant_pool_count The constant_pool_count item represents the number of entries in the constant_pool_types array This value is equal to the number of entries in the constant_pool array of the Constant Pool Component Section 6 7 Constant Pool Component on page 6 14 constant_pool_types The constant_pool_types item is an array that describes the types of the fields and methods referenced in the Constant Pool Component This item has the same number of entries as the constant_pool array of the Constant Pool Component and each entry describes the type of the corresponding entry in the constant_pooll array If the corresponding constant_pool array entry represents a class or interface reference it does not have an associated type In this case the value of the entry in the constant_pool_types array item is OxFFFF If the corresponding constant_pool array entry represents a field or method the value of the entry in the constant_pool_types array is an offset into the type_descriptor_info structure The element at that offset must describe the type of the field or the signature of the method typ
217. of the values they represent must be consistent with those of the selected interface method The interface table of the class of the type of objectref is determined If objectref is an array type then the interface table of class Object Section 2 2 2 4 Classes on page 2 7 is used The interface table is searched for the resolved interface The result of the search is a table that is used to map the method token to a index The index is an unsigned byte that is used as an index into the method table of the class of the type of objectref If the objectref is an array type then the method table of class Object is used The table entry at that index includes a direct reference to the method s code and modifier information The nargs 1 words of arguments and objectref are popped from the operand stack A new stack frame is created for the method being invoked and objectref and the arguments are made the values of its first nargs words of local variables with objectref in local variable 0 arg1 in local variable 1 and so on The new stack frame Chapter 7 Java Card Virtual Machine Instruction Set 7 53 is then made current and the Java Card virtual machine pc is set to the opcode of the first instruction of the method to be invoked Execution continues with the first instruction of the method Runtime Exception If objectref is null the invokeinterface instruction throws a NullPointerException Notes In some circumstances the i
218. of type reference a b field must be of type byte or type boolean m s field must be of type short m i field must be of type int value must be of a type that is assignment compatible with the field descriptor t type The width of a field in a class instance is determined by the field type specified in the instruction The item is resolved determining the field offset The value is popped from the operand stack If the field is of type byte or type boolean the value is truncated to a byte The field at the offset from the start of the object referenced by objectref is set to the value Runtime Exception If objectref is null the putfield_ lt t gt _this instruction throws a NullPointerException Notes 11 The offset may be computed by adding the field token value to the size of an instance of the immediate superclass However this method is not required by this specification A Java Card virtual machine may define any mapping from token value to offset into an instance Chapter 7 Java Card Virtual Machine Instruction Set 7 73 In some circumstances the putfield_ lt t gt _this instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Ver
219. ogram A part of the computer s memory used for dynamic memory allocation in which blocks of memory are used in an arbitrary order The Java Card virtual machine s heap is not required to be garbage collected Objects allocated from the heap are not necessarily reclaimed the on card mechanism to download and install CAP files The installer receives executable binary from the off card installation program writes the binary into the smart card memory links it with the other classes on the card and creates and initializes any data structures used internally by the Java Card Runtime Environment Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 installation program instance variables instantiation instruction internally visible JAR file Java Card Platform Remote Method Invocation Java Card Runtime Environment Java Card RE Java Card Virtual Machine Java Card VM the off card mechanism that employs a card acceptance device CAD to transmit the executable binary in a CAP file to the installer running on the card also known as non static fields in object oriented programming to produce a particular object from its class template This involves allocation of a data structure with the types specified by the template and initialization of instance variables with either default values or those provided by the class s constructor function a statement that indicates an operat
220. omponent on page 6 59 reference fields in the static field image defined by the Static Field Component The ordering constraints or segments associated with a static field image are shown in TABLE 6 14 Reference types occur first in the image Arrays initialized through Java lt clinit gt methods occur first within the set of reference types Primitive types occur last in the image and primitive types initialized to non default values occur last within the set of primitive types TABLE 6 14 Segments of a Static Field Image category segment content reference ji arrays of primitive types initialized by lt clinit gt types Imethods 2 reference types initialized to null including arrays primitive B primitive types initialized to default values ypes 4 primitive types initialized to non default values The number of bytes used to represent each field type in the static field image is shown in the following table TABLE 6 15 Static Field Sizes Type Bytes boolean 1 byte 1 short 2 int 4 reference including arrays 2 The static_field_component structure is defined as Chapter 6 The CAP File Format 6 43 static_field_component ul tag u2 size u2 image_size u2 reference_count u2 array_init_count array_init_info array_init array_init_count u2 default_value_count u2 non_default_value_count ul non_default_values non_default_values_count The items i
221. ons see Java Language Specification section 2 2 1 1 Externally visible items may be represented in an export file For a library package all externally visible items are represented in an export file For an applet package only those externally visible items that are part of a shareable interface are represented in an export file the process by which a Java virtual machine VM allows an unreferenced object instance to release non memory resources for example close and open files prior to reclaiming the object s memory Finalization is only performed on an object when that object is ready to be garbage collected meaning there are no references to the object Finalization is not supported by the Java Card virtual machine The method finalize is not called automatically by the Java Card virtual machine see applet firewall a type of persistent mutable memory It is more efficient in space and power than EPROM Flash memory can be read bit by bit but can be updated only as a block Thus flash memory is typically used for storing additional programs or large chunks of data that are updated as a whole the set of classes that implement the API This includes core and extension packages Responsibilities include applet selection sending APDU bytes and managing atomicity the process by which dynamically allocated storage is automatically reclaimed during the execution of a program a common pool of free memory usable by a pr
222. onstant_pool table The constant_pool entry at that index must be a CONSTANT_Utf 8_info Section 5 6 4 CONSTANT_Ut 8 on page 5 8 structure representing a valid Java package name As in Java class files ASCII periods that normally separate the identifiers in a package name are replaced by ASCII forward slashes For example the package name javacard framework is represented in a CONSTANT_Ut 8_info structure as javacard framework minor_version major_version The minor_version and major_version items are the minor and major version numbers of this package These values uniquely identify the particular implementation of this package and indicate the binary compatibility between packages See Section 4 5 Package Versions on page 4 13 for a description of assigning and using package version numbers 2 This restriction is imposed by the firewall defined in the Runtime Environment Specification Java Card Platform Version 3 0 5 6 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 5 6 2 5 6 3 aid_length The value of the aid_length item gives the number of bytes in the aid array Valid values are between 5 and 16 inclusive aid The aid array contains the ISO AID of this package Section 4 2 AID based Naming on page 4 3 CONSTANT Classref The CONSTANT_Classref_info structure is used to represent a class or interface CONSTANT Classref_in
223. ontain complete access information and descriptive details for each method Instead the information is optimized for size and therefore limited to that required to execute each method without performing verification Complete details regarding the methods defined in this package are included in the Descriptor Component Section 6 13 Descriptor Component on page 6 51 Among other information the Descriptor Component contains the location and number of bytecodes for each method in the Method Component This information can be used to parse the methods in the Method Component Instructions and exception handler catch types in the Method Component reference entries in the Constant Pool Component Section 6 7 Constant Pool Component on page 6 14 No other CAP file components including the Method Component are referenced by the elements in the Method Component 6 36 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The Applet Component Section 6 5 Applet Component on page 6 12 Constant Pool Component Section 6 7 Constant Pool Component on page 6 14 Class Component Section 6 8 Class Component on page 6 22 Export Component Section 6 12 Export Component on page 6 49 Descriptor Component Section 6 13 Descriptor Component on page 6 51 and Debug Component Section 6 14 Debug Component on page 6 59 reference methods defined in the Method Component Th
224. orking space for storing and modifying data RAM is non persistent memory that is the information content is not preserved when power is removed from the memory cell RAM can be accessed an unlimited number of times and none of the restrictions of EEPROM apply a fully functional and compatible implementation of a given technology It enables developers to build prototypes of applications based on the technology an interface which extends directly or indirectly the interface java rmi Remote Each method declaration in the remote interface or its super interfaces includes the exception java rmi RemoteException or one of its superclasses in its throws clause In a remote method declaration if a remote object is declared as a return type it is declared as the remote interface not the implementation class of that interface In addition Java Card RMI imposes additional constraints on the definition of remote methods These constraints are as a result of the Java Card platform language subset and other feature limitations the methods of a remote interface an object whose remote methods can be invoked remotely from the CAD client A remote object is described by one or more remote interfaces acronym for Reserved for Future Use see AID application identifier an acronym for Remote Method Invocation RMI is a mechanism for invoking instance methods on objects located on remote virtual machines meaning a virtual machine oth
225. ort The arrayref index and value are popped from the operand stack The short value is stored as the component of the array indexed by index Runtime Exception If arrayref is null sastore throws a NullPointerException Otherwise if index is not within the bounds of the array referenced by arrayref the sastore instruction throws an ArrayIndexOutOfBoundsException Notes In some circumstances the sastore instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the array referenced by arrayref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 7 5 87 sconst_ lt s gt Push short constant Format sconst_ lt s gt Forms sconst_m1 2 0x2 sconst_0 3 0x3 sconst_1 4 0x4 sconst_2 5 0x5 sconst_3 6 0x6 sconst_4 7 0x7 sconst_5 8 0x8 Stack gt a a lt S gt Description Push the short constant lt s gt 1 0 1 2 3 4 or 5 onto the operand stack 7 82 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 88 Ppa Diso sdiv Divide short Format sdiv Forms sdiv 71 0x47 Stack valuel1 value2 gt result Description Both valuel and value2 must be of type short The values are popped
226. ource constrained world of devices such as smart cards The Classic Edition of the Java Card platform is defined by three specifications this Virtual Machine Specification Java Card Platform Version 3 0 Classic Edition the Application Programming Interface for the Java Card Platform Version 3 0 Classic Edition and the Runtime Environment Specification Java Card Platform Version 3 0 Classic Edition This specification describes the required behavior of the Classic Edition s virtual machine VM for the Java Card platform Java Card virtual machine or Java Card VM version 3 0 that developers should adhere to when creating an implementation An implementation within the context of this document refers to a licensee s implementation of the Java Card virtual machine Application Programming Interface API Converter or other component based on the Java Card technology specifications A reference implementation is an implementation produced by Sun Microsystems Inc Application software written for the Java Card platform is referred to as a Java Card technology based applet Java Card applet or card applet Who Should Use This Specification This document is for licensees of the Java Card technology to assist them in creating an implementation developing a specification to extend the Java Card technology specifications or in creating an extension to the Classic Edition runtime environment xvii fo
227. ows a NullPointerException Notes 6 The offset may be computed by adding the field token value to the size of an instance of the immediate superclass However this method is not required by this specification A Java Card virtual machine may define any mapping from token value to offset into an instance 7 24 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 70 22 In some circumstances the getfield_ lt t gt _this instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If a virtual machine does not support the int data type the getfield_i_this instruction will not be available getfield_ lt t gt _w Fetch field from object wide index Format getfield_ lt t gt _w indexbyte1 indexbyte2 Forms getfield_a_w 169 0xa9 getfield_b_w 170 Oxaa getfield_s_w 171 Oxab getfield_i_w 172 Oxac Stack objectref gt value OR objectref gt value word1 value word2 Description The objectref which must be of type reference is popped from the operand stack The unsigned indexbytel and indexbyte2 are used to construct an index in
228. p1 export file Because p1 is binary compatible with p1 p2 may be linked with either the p1 CAP file or the p1 CAP file FIGURE 4 2 Binary Compatibility Example Convert with P2 CAP File Link with either P1 Export File P1 P1 CAP File CAP File Compatible Binaries Any modification that causes binary incompatibility in the Java programming language also causes binary incompatibility in Java Card systems These modifications are described as causing a potential error in The Java Language Chapter 4 Binary Representation 4 11 Specification Any modification that does not cause binary incompatibility in the Java programming language does not cause binary incompatibility in a Java Card system except under the following conditions m The value of a token assigned to an element in the API of a package is changed m The value of an externally visible final static field compile time constant is changed m An externally visible virtual method that does not override a preexisting method is added to a non final public class m An externally visible interface method that does not override a preexisting method is added to a public interface Tokens are used to resolve references to imported elements of a package If a token value is modified a linker on a device is unable to associate the new token value with the previous token value of the element and therefore is unable to resolve the reference co
229. pabilities of the Java programming language A simple approach to specifying a Java Card virtual machine would be to describe the subset of the features of the Java virtual machine that must be supported to allow for portability of source code across all Java Card technology enabled devices Combining that subset specification and the information in Java Virtual Machine Specification smart card manufacturers could construct their own Java Card technology based implementations Java Card implementations While that approach is feasible it has a serious drawback The resultant platform would be missing the important feature of binary portability of Java Card applets The standards that define the Java platform allow for binary portability of Java programs across all Java platform implementations This write once run anywhere quality of Java programs is perhaps the most significant feature of the platform Part of the motivation for the creation of the Java Card platform was to bring just this kind of binary portability to the smart card industry In a world with hundreds of millions or perhaps even billions of smart cards with varying processors and configurations the costs of supporting multiple binary formats for software distribution could be overwhelming This Virtual Machine Specification Java Card Platform Version 3 0 Classic Edition is the key to providing binary portability One way of understanding what this specification d
230. pes m byte whose values are 8 bit signed two s complement integers a short whose values are 16 bit signed two s complement integers Some Java Card virtual machine implementations may also support an additional integral type m int whose values are 32 bit signed two s complement integers Support for the boolean type is identical to that in the Java virtual machine The value 1 is used to represent true and the value of 0 is used to represent false Support for reference types is identical to that in the Java virtual machine 3 1 32 Words The Java Card virtual machine is defined in terms of an abstract storage unit called a word This specification does not mandate the actual size in bits of a word on a specific platform A word is large enough to hold a value of type byte short reference or returnAddress Two words are large enough to hold a value of type int The actual storage used for values in an implementation is platform specific There is enough information present in the descriptor component of a CAP file to allow an implementation to optimize the storage used for values in variables and on the stack 3 3 Runtime Data Areas The Java Card virtual machine can support only a single thread of execution Any runtime data area in the Java virtual machine which is duplicated on a per thread basis will have only one global copy in the Java Card virtual machine The Java Card virtual machine s heap is no
231. plement the firewall restrictions defined by the Runtime Environment Specification Java Card Platform Version 3 0 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 6 8 2 2 6 8 2 3 interface_info Items superinterfaces The superinterfaces item of the interface_info structure is an array of class_ref structures representing the superinterfaces of this interface The class_ref structure is defined as part of the CONSTANT_Classref_info structure Section 6 7 1 CONSTANT_Classref on page 6 17 This array is empty if this interface has no superinterfaces Both direct and indirect superinterfaces are represented in the array Class Object is not included interface_name The interface_name item represents interface name information required if the interface is remote The interface_name item is defined by a interface_name_info structure If the value of the ACC_REMOTE flag is zero the structure is defined as interface_name_info If the value of the ACC_REMOTE flag is one the structure is defined as interface _name_info ul interface_name_length ul interface_name interface_name_length The values in the interface_name_info structure are defined as follows interface_name_length The interface_name_length item is the number of bytes in interface_name item interface_name The item is a variable length representation of the name of this interface in UTF 8
232. present the parameters passed to this method including the this pointer if this method is a virtual method Parameters of type int are represented in two words while all others are represented in one word See Section 3 2 Words on page 3 2 max_locals The max_locals item indicates the number of words required to represent the local variables declared by this method not including the parameters passed to this method on invocation Local variables of type int are represented in two words while all others are represented in one word Section 3 2 Words on page 3 2 If an entry in the local variables array of the stack frame is reused to store more than one local variable for example local variables from separate scopes the number of words required for storage is two if one or more of the local variables is of type int bytecodes The bytecodes item represents an array of Java Card bytecodes that implement this method Valid instructions are defined in Chapter 7 Java Card Virtual Machine Instruction Set The impdep1 and impdep2 bytecodes cannot be present in the bytecodes array item If this method is abstract the bytecodes item must contain zero elements Static Field Component The Static Field Component contains all of the information required to create and initialize an image of all of the static fields defined in this package referred to as the static field image Offsets to particular static fields are
233. ption Both valuel and value2 must be of type int They are popped from the operand stack An int result is calculated by taking the bitwise AND conjunction of value1 and value2 The result is pushed onto the operand stack Notes If a virtual machine does not support the int data type the iand instruction will not be available 7 5 31 iastore Store into int array Format iastore Forms iastore 58 0x3a Stack arrayref index value word1 value word2 gt Description 7 32 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 70 002 The arrayref must be of type reference and must refer to an array whose components are of type int The index must be of type short and value must be of type int The arrayref index and value are popped from the operand stack The int value is stored as the component of the array indexed by index Runtime Exception If arrayref is null iastore throws a NullPointerException Otherwise if index is not within the bounds of the array referenced by arrayref the iastore instruction throws an ArrayIndexOutOfBoundsException Notes In some circumstances the iastore instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the array referenced by arrayref The exact circumstances when the exception will be thrown are specified i
234. r interface into the info item of the Class Component Section 6 8 Class Component on page 6 22 superclass _name_index Contains an index into the strings_table item of the debug_component structure The strings_table entry at the indexed location must be the fully qualified name of the superclass of this class or the string null if the class has no superclass source_file_index Contains the index into the strings_table item of the debug_component structure The strings_table entry at the indexed location must be the name of the source file in which this class is defined interface_count 8 The ACC_SHAREABLE flag is defined to enable Java Card virtual machines to implement the firewall restrictions defined by the Runtime Environment Specification Java Card Platform Version 3 0 6 62 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 6 14 1 1 The number of indexes in the interface_names_indexes table field_count The number of field_debug_info structures in the fields table method_count The number of method_debug_info structures in the methods table interface_names_indexes Contains the indexes into the strings_table item of the debug_component structure The strings_table entry at each indexed location must be the name of an interface implemented by this class There must be an index value present for every interface implemented by this class i
235. r lt clinit gt a class or interface initialization method It must be static and therefore cannot be abstract The resolved method includes the code for the method an unsigned byte nargs that may be zero and the method s modifier information The operand stack must contain nargs words of arguments where the number of words of arguments and the type and order of the values they represent must be consistent with those of the resolved method The nargs words of arguments are popped from the operand stack A new stack frame is created for the method being invoked and the words of arguments are made the values of its first nargs words of local variables with arg1 in local variable 0 arg2 in local variable 1 and so on The new stack frame is then made current and the Java Card virtual machine pc is set to the opcode of the first instruction of the method to be invoked Execution continues with the first instruction of the method 7 5 57 anvokevirtial Invoke instance method dispatch based on class Format invokevirtual indexbyte1 indexbyte2 Forms invokevirtual 139 Ox8b 7 56 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Stack objectref arg1 arg2 gt Description The unsigned indexbytel and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the in
236. r the Java Card platform Java Card Runtime Environment or Java Card RE This document is also intended for Java Card applet developers who want a more detailed understanding of the Java Card technology specifications Before You Read This Specification Before reading this document you should be familiar with the Java programming language the Java Card technology specifications and smart card technology A good resource for becoming familiar with Java technology and Java Card technology is the Sun Microsystems Inc web site located at http java sun com This specification is not intended to stand on its own rather it relies heavily on existing documentation of the Java platform In particular two books are required for the reader to understand the material presented here The Java Language Specification by James Gosling Bill Joy and Guy L Steele Addison Wesley 1996 ISBN 0 201 31008 2 contains the definitive definition of the Java programming language The Java Card platform version 3 0 language subset defined here is based on the language specified in this book The Java Virtual Machine Specification Second Edition by Tim Lindholm and Frank Yellin Addison Wesley 1999 ISBN 0 201 43294 3 defines the standard operation of the Java Virtual Machine JVM software The Java Card virtual machine presented here is based on the definition specified in this book How This Specification Is Organized Chap
237. rarchies Represented Classes and interfaces represented in an export file include public elements defined within their respective hierarchies For example instead of indicating the immediate superclass or superinterface all public superclasses or superinterfaces are listed This design concept is applied not only to superclasses or superinterfaces but also to virtual methods and implemented interfaces 5 5 Export File An export file is defined by the following structure ExportFile u4 magic ul minor _ version ul major_version u2 constant_pool_count cp_info constant_pool constant_pool_count u2 this_package ul export_class_count class_info classes export_class_count The items in the ExportFile structure are as follows magic The magic item contains the magic number identifying the ExportFile format it has the value 0x00FACADE minor_version major_version The minor_version and major_version items are the minor and major version numbers of this export file Together a major and a minor version number determine the version of the export file format If an export file has the major version number of M and minor version number of m the version of the export file s format is M m A change in the major version number indicates a major incompatibility change one that requires a fundamentally different Java Card virtual machine A Java Card virtual machine is not required to support export files with di
238. ray_init_count item indicates the number of elements in the array_init array This is the number of fields represented in segment 1 of the static field image as described in TABLE 6 14 It represents the number of arrays initialized in all of the lt clinit gt methods in this package If this CAP file defines a library package the value of array_init_count must be zero array_init The array_init item represents an array of array_init_info structures that specify the initial array values of static fields of arrays of primitive types These initial values are indicated in Java lt clinit gt methods The array_init_info structure is defined as array_init_info ul type u2 count ul values count The items in the array_init_info structure are defined as follows type The type item indicates the type of the primitive array Valid values are shown in the following table TABLE 6 16 Array Types Type Value lboolean 2 byte 3 short 4 int 5 count The count item indicates the number of bytes in the values array It does not represent the number of elements in the static field array referred to as length in the Java programming language since the values array is an array of bytes and the static field array may be a non byte type The Java programming Chapter 6 The CAP File Format 6 45 6 11 6 46 language length of the static field array is equal to the count item divided by the num
239. rclass superinterface and implemented interface references When a superclass superinterface or implemented interface is defined in an imported package the Import Component is used in the representation of the reference The classes represented in the Class Component also contain references to virtual methods defined in the Method Component Section 6 9 Method Component on page 6 36 of this CAP file References to virtual methods defined in imported packages are not explicitly described Instead such methods are located through a superclass within the hierarchy of the class where the superclass is defined in the same imported package as the virtual method The Constant Pool Component Section 6 7 Constant Pool Component on page 6 14 Export Component Section 6 12 Export Component on page 6 49 Descriptor Component Section 6 13 Descriptor Component on page 6 51 and Debug Component Section 6 14 Debug Component on page 6 59 reference classes and interfaces defined in the Class Component No other CAP file components reference the Class Component The Class Component is represented by the following structure class_component ul tag u2 size u2 signature_pool_length type_descriptor signature_pool interface_info interfaces The items in the class_component structure are as follows tag The tag item has the value COMPONENT_Class 6 size The size item indicates the number of bytes in
240. re defined as follows remote_method_hash The remote_method_hash item contains a two byte hash value for the method The hash value is computed from the simple not fully qualified name of the method concatenated with its method descriptor The representation of the method descriptor is the same as in a Java class file See the specification described in Java Virtual Machine Specification 4 3 3 The hash value uniquely identifies the method within the class The hash code is defined as the first two bytes of the SHA 1 message digest function performed on the hash_modifier item described below followed by the name of the method followed by the method descriptor representation in UTF 8 format Rare hash collisions are averted automatically during package conversion by adjusting the anti collision string signature_offset The signature_offset item contains an offset from the signature_pool item of the info item of the Class Component to the variable length type descriptor structure inside the signature_pool item This structure represents the signature of the remote method virtual_method_token The virtual_method_token item is the virtual method token of the remote method in this class hash_modifier_length The hash_modifier_length item is the number of bytes in the following hash_modifier item The value of this item must be zero if an anti collision string is not required hash_modifier The hash_modifier item is a variable
241. re three scopes for field tokens final static fields of primitive types compile time constants all other static fields and instance fields 5 12 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 If this field is a compile time constant the value of the token item is OxFF Compile time constants are represented in export files but are not assigned token values suitable for late binding Instead Java Card Converters must replace bytecodes that reference final static fields with bytecodes that load the constant value of the field 4 If this field is static but is not a compile time constant the token item represents a static field token Section 4 3 7 3 Static Fields on page 4 8 If this field is an instance field the token item represents an instance field token Section 4 3 7 5 Instance Fields on page 4 9 access flags The value of the access_ flags item is a mask of modifiers used with fields The access_flags modifiers are shown in the following table TABLE 5 4 Export File Field Access and Modifier Flags Name Value Meaning Used By I ACC_PUBLIC 0x0001 Is public may be accessed Any field from outside its package JACC_PROTECTED 0x0004 Ils protected may be Class field accessed within Instance field subclasses IACC_STATIC 0x0008 Ils static Class field Interface field ACC_FINAL 0x0010 Is final no further Any field overriding or assignment a
242. reference type the class referenced must be a public class attributes_count The value of the attributes_count item indicates the number of additional attributes of this field The only ield_info attribute currently defined is the ConstantValue attribute Section 5 10 1 ConstantValue Attribute on page 5 16 For static final fields of primitive types the value must be 1 that is when both the ACC_STATIC and ACC_FINAL bits in the flags item are set an attribute must be present For all other fields the value of the attributes_count item must be 0 attributes The only attribute defined for the attributes table of a field_info structure by this specification is the ConstantValue attribute Section 5 10 1 ConstantValue Attribute on page 5 16 This must be defined for static final fields of primitive types boolean byte short and int Methods Each method is described by a variable length method_info structure The format of this structure is method_info ul token u2 access_flags Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 u2 name_index u2 descriptor_index The items of the method_info structure are as follows token The token item is the token assigned to this method If this method is a static method or constructor the token item represents a static method token Section 4 3 7 4 Static Methods and Constructors on page 4 8 If
243. renced class is defined in this package the high bit is equal to zero If the reference class is defined in an imported package the high bit of this structure is equal to one The class referenced in the CONSTANT_InstanceField_info structure must be the class that contains the declaration of the instance field The class referenced in the CONSTANT_VirtualMethodref_info structure must be a class that contains a declaration or definition of the virtual method The class referenced in the CONSTANT_SuperMethodref_info structure must be the class that defines the method that contains the Java language level super invocation token The token item in the CONSTANT_InstanceFieldref_info structure represents an instance field token Section 4 3 7 5 Instance Fields on page 4 9 of the referenced field The value of the instance field token is defined within the scope of the class indicated by the class item The token item of the CONSTANT_VirtualMethodref_info structure represents the virtual method token Section 4 3 7 6 Virtual Methods on page 4 9 of the referenced method The virtual method token is defined within the scope of the hierarchy of the class indicated by the class item If the referenced method is public or protected the high bit of the token item is zero If the referenced method is package visible the high bit of the token item is one In this case the class item must represent a reference to a class defined in this packa
244. resenting a valid fully qualified Java class name Entries in the supers array can occur in any order For an interface the supers array contains a single value representing a valid index into the constant_pool table The constant_pool entry must be a CONSTANT_Classref_info structure Section 5 6 2 CONSTANT_Classref on page 5 7 representing the fully qualified name of the java lang Object class export_interfaces_count The value of the export_interfaces_count item indicates the number of entries in the interfaces array interfaces If this class_info structure describes a class the interfaces array contains an entry for each public interface implemented by this class It does not include package visible interfaces It does include all public superinterfaces in the hierarchies of public interfaces implemented by this class If this class_info structure describes an interface the interfaces array contains an entry for each public interface extended by this interface It does not include package visible interfaces It does include all public superinterfaces in the hierarchies of public interfaces extended by this interface Each value in the interfaces array must be a valid index into the constant_pool table The constant_pool entry at each value must be a CONSTANT_Classref_info structure Section 5 6 2 CONSTANT_Classref on page 5 7 representing a valid fully qualified Java interface name Entries in the interfaces array
245. riable This asymmetry is intentional The ret instruction should not be confused with the return instruction A return instruction returns control from a Java method to its invoker without passing any value back to the invoker Chapter 7 Java Card Virtual Machine Instruction Set 7 77 7 5 80 return Return void from method Format return Forms return 122 0x7a Stack a gt empty Description Any values on the operand stack of the current method are discarded The virtual machine then reinstates the frame of the invoker and returns control to the invoker 7 5 81 s2 Convert short to byte Format s2b Forms s2b 91 0x5b Stack value gt result Description The value on top of the operand stack must be of type short It is popped from the top of the operand stack truncated to a byte result then sign extended to a short result The result is pushed onto the operand stack Notes 7 78 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 82 7 5 83 The s2b instruction performs a narrowing primitive conversion It may lose information about the overall magnitude of value The result may also not have the same sign as value s2i Convert short to int Format s2i Forms s2i 92 0x5c Stack Value gt result word1 result word2 Description The value on top of the operand stack must be of type short
246. rogramming language package Each component describes a set of elements in the Java programming language package or an aspect of the CAP file A complete CAP file must contain all of the required components Header Directory Import Constant Pool Method Static Field and Reference Location The following components are optional the Applet Export and Debug The Applet component is included only if one or more Applets are defined in the package The Export component is included only if classes in other packages may import elements in the package defined The Debug component is optional It contains all of the data necessary for debugging a package a card session begins with the insertion of the card into the CAD The card is then able to exchange streams of APDUs with the CAD The card session ends when the card is removed from the CAD Glossary 2 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 cast constant pool context context switch Converter currently active context currently selected applet custom CAP file component default applet EEPROM the explicit conversion from one data type to another the constant pool contains variable length structures representing various string constants class names field names and other constants referred to within the CAP file and the Export File structure Each of the constant pool entries including entry zero is a variable length
247. rrectly Compile time constants are not stored as fields in CAP files Instead their values are recorded in export files and placed inline in the bytecodes in CAP files These values are said to be pre linked in a CAP file of a package that imports those constants During execution information is not available to determine whether the value of an inlined constant is the same as the value defined by the binary of the imported package As described above tokens assigned to public and protected virtual methods are scoped to the hierarchy of a class Tokens assigned to public and protected virtual methods introduced in a subclass have values starting at one greater than the maximum token value assigned in a superclass If a new non override public or protected virtual method is introduced in a superclass it is assigned a token value that would otherwise have been assigned in a subclass Therefore two unique virtual methods could be assigned the same token value within the same class hierarchy making resolution of a reference to one of the methods ambiguous The addition of an externally visible non override method to a public interface is a binary incompatible change It allows classes which are not themselves abstract to contain an abstract method For example consider the case of an interface I implemented by a class C that is not abstract where I and C reside in different packages If a new method is added to I creating I then C cannot li
248. rst_reference_token ul reference_count ul public_method_table_base ul public_method_table_count ul package_method_table_base ul package_method_table_count u2 public_virtual_method_table public_method_table_count u2 package_virtual_method_table package_method_table_count implemented_interface_info interfaces interface_count remote_interface_info remote_interfaces The interface_name item is required if the value of ACC_REMOTE is one This item must be omitted otherwise See the description of this field for more information The remote_inter faces item is required if the value of ACC_REMOTE is one This item must be omitted otherwise See the description of this field for more information Chapter6 The CAP File Format 6 27 6 8 2 1 interface_info and class_info Shared Items flags The flags item is a mask of modifiers used to describe this interface or class Valid values are shown in the following table TABLE 6 12 CAP File Interface and Class Flags Name Value IAACC_INTERFACE 0x8 ACC_SHAREABLE 0x4 ACC_REMOTE 0x2 The ACC_INTERFACE flag indicates whether this interface_info or class_info structure represents an interface or a class The value must be one if it represents an interface_info structure and zero if a class_info structure The ACC_SHAREABLE flag in an interface_info structure indicates whether this interface is shareable The value of this flag must be one
249. rt the int data type the ixor instruction will not be available 7 5 69 jsr Jump subroutine Format jsr branchbyte1 branchbyte2 Forms jsr 113 0x71 Stack o gt address Description 7 66 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 70 The address of the opcode of the instruction immediately following this jsr instruction is pushed onto the operand stack as a value of type returnAddress The unsigned branchbyte1 and branchbyte2 are used to construct a signed 16 bit offset where the offset is branchbyte1 lt lt 8 branchbyte2 Execution proceeds at that offset from the address of this jsr instruction The target address must be that of an opcode of an instruction within the method that contains this jsr instruction Notes The jsr instruction is used with the ret instruction in the implementation of the finally clause of the Java language Note that jsr pushes the address onto the stack and ret gets it out of a local variable This asymmetry is intentional new Create new object Format new indexbyte1 indexbyte2 Forms new 143 0x8f Stack gt objectref Description The unsigned indexbytel and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbytel1 lt lt 8 indexbyte2 The item at that inde
250. rtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 CHAPTER 4 Binary Representation This chapter presents information about the binary representation of Java Card programs Java Card technology based binaries Java Card binaries are usually contained in files therefore this chapter addresses binary representation in terms of this common case Several topics relating to binary representation are covered The first section describes the basic organization of program representation in export and CAP files as well as the use of the Java Archive JAR file containers The second section covers how Java Card applets and packages are named using unique identifiers The third section presents the scheme used for naming and linking items within Java Card API packages The fourth and fifth sections describe the constraints for upward compatibility between different versions of a Java Card technology based binary Java Card binary program file and versions assigned based upon that compatibility 4 1 Java Card Platform File Formats Java programs are represented in compiled binary form as class files Java class files are used not only to execute programs on a Java virtual machine but also to provide type and name information to a Java compiler In the latter role a class file is essentially used to document the API of its class to client code That client code is compiled into its own class f
251. rtual machine itself need not load or manipulate CAP files it need only execute the applet code found in the CAP file that was loaded onto the device by the installation program The division of functionality between the Java Card virtual machine and the installation program keeps both the virtual machine and the installation program small The installation program may be implemented as a Java program and executed on top of the Java Card virtual machine Since instructions for the Java Card platform Java Card instructions are denser than typical machine code this may reduce the size of the installer The modularity may enable different installers to be used with a single Java Card virtual machine implementation 13 1 4 Java Language Security One of the fundamental features of the Java virtual machine is the strong security provided in part by the class file verifier Many devices that implement the Java Card platform may be too small to support verification of CAP files on the device itself This consideration led to a design that enables verification on a device but does not rely on it The data in a CAP file that is needed only for verification is packaged separately from the data needed for the actual execution of its applet This allows for flexibility in how security is managed in an implementation There are several options for providing language level security on a Java Card technology enabled device The conceptually simpl
252. ruction within the method that contains this stableswitch instruction 7 5 107 sushr Logical shift right short Format sushr Forms sushr 81 0x51 Stack value1 value2 gt result Description Both valuel and value2 must be of type short The values are popped from the operand stack A short result is calculated by sign extending value1 to 32 bits and shifting the result right by s bit positions with zero extension where s is the value of the low five bits of value2 The resulting value is then truncated to a 16 bit result The result is pushed onto the operand stack 7 96 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 TxD LOG Notes If valuel is positive and s is value2 amp Ox1f the result is the same as that of valuel gt gt s if valuel is negative the result is equal to the value of the expression valuel gt gt s 2 lt lt s The addition of the 2 lt lt s term cancels out the propagated sign bit The shift distance actually used is always in the range 0 to 31 inclusive as if value2 were subjected to a bitwise logical AND with the mask value 0x1f The mask value of 0x1f allows shifting beyond the range of a 16 bit short value It is used by this instruction however to ensure results equal to those generated by the Java instruction iushr swap_x Swap top two operand stack words Format swap_x mn Forms swap_x 6
253. s The Java Card virtual machine reserves all other flag values Their values must be zero name_index Chapter 5 The Export File Format 5 15 The value of the name_index item must be a valid index into the constant_pool table The constant_pool entry at that index must be a CONSTANT_Ut 8_info Section 5 6 4 CONSTANT_Ut 8 on page 5 8 structure representing either the special internal method name for constructors lt init gt or a valid Java method name stored as a simple not fully qualified name descriptor_index The value of the descriptor_index item must be a valid index into the constant_pool table The constant_pool entry at that index must be a CONSTANT_Utf 8_info Section 5 6 4 CONSTANT_Ut f8 on page 5 8 structure representing a valid Java method descriptor Representation of a method descriptor in an export file is the same as in a Java class file See the specification described in The Java Virtual Machine Specification Section 4 3 3 The Export File and Conversion on page 4 6 All classes referenced in a descriptor must be public classes 5 10 Attributes Attributes are used in the field_info Section 5 8 Fields on page 5 12 structure of the export file format All attributes have the following general format attribute_info u2 attribute_name_index u4 attribute_length ul info attribute_length 5 10 1 ConstantValue Attribute The ConstantValue attribute is a fixed le
254. s Etats Unis logiciel commercial Les droits des utilisateur du gouvernement des Etats Unis sont soumis aux termes de la licence standard Sun Microsystems et aux conditions appliqu es de la FAR et de ces compl ments L utilisation est soumise aux termes de la Licence Cette distribution peut comprendre des composants d velopp s par des tierces parties Des parties de ce produit pourront tre d riv es des syst mes Berkeley BSD licenci s par l Universit de Californie Sun Sun Microsystems le logo Sun Solaris Java Java Card JDK Servlet et JVM sont des marques de fabrique ou des marques d pos es de Sun Microsystems Inc aux Etats Unis et dans d autres pays UNIX est une marque d pos e aux Etats Unis et dans d autres pays et licenci e exlusivement par X Open Company Ltd Le logo Adobe est une marque d pos e de Adobe Systems Incorporated Les produits qui font l objet de ce manuel d entretien et les informations qu il contient sont regis par la legislation americaine en matiere de controle des exportations et peuvent etre soumis au droit d autres pays dans le domaine des exportations et importations Les utilisations finales ou utilisateurs finaux pour des armes nucleaires des missiles des armes biologiques et chimiques ou du nucleaire maritime directement ou indirectement sont strictement interdites Les exportations ou reexportations vers des pays sous embargo des Etats Unis ou vers des entites figurant sur les listes
255. s equal to 1 if the active range does not intersect with a succeeding exception handler s active range and this exception handler is the last handler applicable to the active range It is equal to 0 if the active range is contained within the active range of another exception handler or there is at least one succeeding handler applicable to the same active range The stop_bit provides an optimization to be used during the interpretation of the athrow bytecode As the interpreter searches for an appropriate exception handler it may terminate the search of the exception handlers in this Method Component under the following conditions a the location of the current program counter is less than the end_offset of this exception handler and a the stop_bit of this exception handler is equal to 1 When these conditions are satisfied it is guaranteed that none of the succeeding exception handlers in this Method Component will contain an active range appropriate for the current exception Chapter6 The CAP File Format 6 39 In CODE EXAMPLE 6 1 the stop_bit item is set for both the third and fourth handlers handler_offset The handler_offset item represents a byte offset into the info item of the Method Component It indicates the start of the exception handler At the Java source level this is equivalent to the beginning of a catch or finally block The value of the item must be a valid offset into a bytecodes array of a method_info structur
256. s t as follows m a field must be of type reference m b field must be of type byte or type boolean m s field must be of type short m i field must be of type int value must be of a type that is assignment compatible with the field descriptor t type The width of a field in a class instance is determined by the field type specified in the instruction The item is resolved determining the field offset The objectref which must be of type reference and the value are popped from the operand stack If the field is of type byte or type boolean the value is truncated to a byte The field at the offset from the start of the object referenced by objectref is set to the value Runtime Exception If objectref is null the putfield_ lt t gt _w instruction throws a NullPointerException Notes In some circumstances the putfield_ lt t gt _w instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the object referenced by objectref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 If a virtual machine does not support the int data type the putfield_i_w instruction will not be available putstatic_ lt t gt Set static field in class 12 The offset may be computed by adding the field token value to the size of an i
257. s table must be equal to the value of the virtual method token of the indicated method minus the value of the public_method_table_base item Entries in the public_virtual_method_table array that represent methods defined or declared in this package contain offsets into the info item of the Method Component Section 6 9 Method Component on page 6 36 to the method_info structure representing the method Entries that represent methods defined or declared in an imported package contain the value 0xFFFF Entries for methods that are declared abstract are represented in the public_virtual_method_table array in the same way as non abstract methods package_virtual_method_table The package_virtual_method_table item of the class_info structure represents an array of package visible virtual methods These methods can be invoked on an instance of this class The package_virtual_method_table array includes methods declared or defined by this class It may also include methods declared or defined by any or all of its superclasses that are defined in this package The value of an index into this table must be equal to the value of the virtual method token of the indicated method amp 0x7F minus the value of the package_method_table_base item All entries in the package_virtual_method_table array represent methods defined or declared in this package They contain offsets into the info item of the Method Component Section 6 9 Method
258. sary 7 objects 2 7 2 10 Glossary 7 deletion mechanism 2 8 dynamic creation 2 5 representation of 3 3 opcode mnemonic 8 4 opcode value 8 1 opcodes 3 4 reserved 7 2 operands 3 4 origin logical channel Glossary 7 OutOfMemoryError 2 22 Index 5 owning context 3 3 Glossary 7 P package 2 5 Glossary 7 applet 1 4 classes 2 9 library 1 4 name 2 9 references 2 9 versions 4 13 package 2 7 parameters 2 13 PCD Glossary 7 persistent object Glossary 7 PIX 4 3 Glossary 7 pop 7 69 pop2 7 70 primitive types 3 1 primitive values values primitive 3 1 private 2 7 proprietary identifier extension Glossary 1 proprietary identifier extension PIX 4 3 protected 2 7 Proximity Coupling Device Glossary 7 public 2 7 putfield_ lt t gt 7 70 putfield_ lt t gt _this 7 72 putfield_ lt t gt _w 7 74 putstatic_ lt t gt 7 75 R RAM resources 2 1 reference implementation Preface xvii reference location component of a CAP file 6 46 reference types 3 1 reference types 3 1 reference values 3 1 references external 4 6 internal 4 6 remote classes 2 12 remote interfaces 2 12 access control 2 12 reserved opcodes 7 2 resident image 4 13 resource identifier RID 4 3 ret 7 77 return 2 7 7 78 return values 2 13 returnAddress types 3 1 RID 4 3 RMI 2 12 runtime data areas 3 2 runtime exceptions exceptions runtime 2 21 S s2b 7 78 s2i 7 79 sadd 7 79 s
259. set from the address of the opcode of this if_scmp lt cond gt _w instruction The target address must be that of an opcode of an instruction within the method that contains this if_scmp lt cond gt _w instruction Otherwise execution proceeds at the address of the instruction following this if_scmp lt cond gt _w instruction 1 lt cond gt Branch if short comparison with zero succeeds Format if lt cond gt branch Forms ifeq 96 0x60 ifne 97 0x61 iflt 98 0x62 ifge 99 0x63 ifgt 100 0x64 ifle 101 0x65 Stack Value gt Description The value must be of type short It is popped from the operand stack and compared against zero All comparisons are signed The results of the comparisons are as follows m eq succeeds if and only if value 0 m ne succeeds if and only if value 1 4 0 m lt succeeds if and only if value lt 0 m le succeeds if and only if value 0 m gt succeeds if and only if value gt 0 m ge succeeds if and only if value 0 Chapter 7 Java Card Virtual Machine Instruction Set 7 39 If the comparison succeeds branch is used as signed 8 bit offset and execution proceeds at that offset from the address of the opcode of this if lt cond gt instruction The target address must be that of an opcode of an instruction within the method that contains this if lt cond gt instruction Otherwise execution proceeds at the address of the instruction following this if lt co
260. sion 3 0 If a virtual machine does not support the int data type the putfield_i_this instruction will not be available 7 5 77 putfield_ lt t gt _w Set field in object wide index Format putfield lt t gt _w indexbyte1 indexbyte2 Forms putfield_a_w 177 Oxb1 putfield_b_w 178 0xb2 putfield_s_w 179 Oxb3 putfield_i_w 180 Oxb4 Stack objectref value gt OR objectref value word1 value word2 gt Description The unsigned indexbytel and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbytel lt lt 8 indexbyte2 The constant pool item at the index must be of type CONSTANT_InstanceFieldref Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT_VirtualMethodref and CONSTANT_SuperMethodref on page 6 18 a reference to a class and a field token 7 74 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 5 78 The class of objectref must not be an array If the field is protected and it is a member of a superclass of the current class and the field is not declared in the same package as the current class then the class of objectref must be either the current class or a subclass of the current class If the field is final it must be declared in the current class The item must resolve to a field with a type that matche
261. ss flags token_var If the field is an instance field this value is the instance field token of the field The pad1 pad2 and pad3 items are padding only their values should be ignored location_var If the field is a non final static field or a final static field with an array type a constant array this value is the byte offset of the location for this field in the static field image defined by the Static Field Component Section 6 10 Static Field Component on page 6 42 The pad item is padding only its value should be ignored const_value If the field is a final static field of type byte boolean short or int this value is interpreted as a signed 32 bit constant The method_debug_info Structure The method_debug_info structure describes a method of a class It can describe methods that are either virtual or non virtual static or initialization methods The structure is defined as follows method_debug_info u2 name_index u2 descriptor_index u2 access_flags u2 location ul header_size u2 body_size u2 variable_count u2 line_count variable_info variable_table variable_count line_info line _table line_count The items in the method_debug_info structure are defined as follows name_index Chapter6 The CAP File Format 6 65 Contains an index into the strings_table item of the debug_component structure The strings_table entry at the indexed location must be the simple meaning not fully
262. stance s fields In such cases the token value is distinct from and unrelated to the value of the resolved index Token Details Each kind of item in a package has its own independent scope for tokens of that kind The token range and assignment rules for each kind are listed in TABLE 4 2 TABLE 4 2 Token Range Type and Scope Token Type Range ype Scope Package 0 127 Private Package Class 0 254 Public Package Static Field o 255 Public Class Static Method 0 255 Public Class Instance Field 0 255 Public or Private Class Virtual Method 0 127 Public or Private Class Hierarchy Interface Method 0 127 Public Class Chapter 4 Binary Representation 4 7 4 3 7 1 4 3 7 2 4 3 7 3 4 3 7 4 4 8 Package All package references from within a CAP file are assigned private package tokens Package token values must be in the range from 0 to 127 inclusive The tokens for all the packages referenced from classes in a CAP file are numbered consecutively starting at zero The ordering of package tokens is not specified Classes and Interfaces All externally visible classes and interfaces in a package are assigned public class tokens Class token values must be in the range from 0 to 254 inclusive The tokens for all the public classes and interfaces in a package are numbered consecutively starting at zero The ordering of class tokens is not specified Package visible class
263. structure are defined as follows name_index Contains an index into the strings_table item of the debug_component structure The strings_table entry at the indexed location must be the simple meaning not fully qualified name of the field for example applets descriptor_index Contains an index into the strings_table item of the debug_component structure The strings_table entry at the indexed location must be the type of the field Class types are fully qualified for example TLjavacard framework Applet access flags A two byte mask of modifiers that apply to this field TABLE 6 23 Field Access and Modifier Flags Modifier Value IAACC_PUBLIC 0x0001 ACC_PRIVATE 0x0002 ACC_PROTECTED 0x0004 ACC_STATIC 0x0008 ACC_FINAL 0x0010 The above field access and modifier flags are defined in the same way and with the same restrictions as described in the Java Virtual Machine Specification contents 6 64 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 6 14 1 2 A field_debug_info structure can describe an instance field a static field or a static final field a constant Constants can be either primitive data or arrays of primitive data Depending on the kind of field described the contents item is interpreted in different ways The kind and type of the field can be determined by examining the field s descriptor and acce
264. structure whose format is indicated by its first tag byte There are no ordering constraints on entries in the constant pool entries One constant pool is associated with each package There are differences between the Java platform constant pool and the Java Card technology based constant pool For example in the Java platform constant pool there is one constant type for method references while in the Java Card constant pool there are three constant types for method references The additional information provided by a constant type in Java Card technologies simplifies resolution of references protected object space associated with each applet package and Java Card RE All objects owned by an applet belong to context of the applet s package a change from one currently active context to another For example a context switch is caused by an attempt to access an object that belongs to an applet instance that resides in a different package The result of a context switch is a new currently active context a piece of software that preprocesses all of the Java programming language class files that make up a package and converts the package to a CAP file The Converter also produces an export file when an object instance method is invoked an owning context of this object becomes the currently active context the Java Card RE keeps track of the currently selected Java Card applet Upon receiving a SELECT FILE command with this applet s AID
265. sts of a short match and a signed 16 bit offset Each of the signed 16 bit values is constructed from two unsigned bytes as bytel lt lt 8 byte2 The table match offset pairs of the slookupswitch instruction must be sorted in increasing numerical order by match The key must be of type short and is popped from the operand stack and compared against the match values If it is equal to one of them then a target address is calculated by adding the corresponding offset to the address of the opcode of this Chapter 7 Java Card Virtual Machine Instruction Set 7 87 slookupswitch instruction If the key does not match any of the match values the target address is calculated by adding default to the address of the opcode of this slookupswitch instruction Execution then continues at the target address The target address that can be calculated from the offset of each match offset pair as well as the one calculated from default must be the address of an opcode of an instruction within the method that contains this slookupswitch instruction Notes The match offset pairs are sorted to support lookup routines that are quicker than linear search 7 5 95 smul Multiply short Format smul Forms smul 69 0x45 Stack value1 value2 gt result Description Both value1 and value2 must be of type short The values are popped from the operand stack The short result is value1 value2 The result is pushed onto th
266. t Section 6 8 Class Component on page 6 22 If this package defines a library package the item at that offset must be either an interface_info or a class_info structure The interface_info or class_info structure at that offset must represent the exported class or interface If this package defines an applet package the item at the class_offset in the info item of the Class Component must be an interface_info structure The interface_info structure at that offset must represent the exported shareable interface In particular the ACC_SHAREABLE flag of the interface_info structure must be equal to 1 static_field_count The static_field_count item represents the number of elements in the static_field_offsets array This value indicates the number of public and protected static fields defined in this class excluding final static fields of primitive types If the class_offset item represents an offset to an interface_info structure the value of the static_field_count item must be zero Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 static_method_count The static_method_count item represents the number of elements in the static_method_offsets array This value indicates the number of public and protected static methods and constructors defined in this class If the class_offset item represents an offset to an interface_info structure the value of the static_method_count item must be zer
267. t Java Card virtual machines from supporting the full range of functionality of certain Java platform features The features in question are supported but a particular virtual machine may limit the range of operation to less than that of the Java platform Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 2 2 4 1 2 2 4 2 To ensure a level of portability for application code this section establishes a minimum required level for partial support of these language features The limitations here are listed as maximums from the application programmer s perspective Java packages that do not violate these maximum values can be converted into Java Card technology based CAP files Java Card CAP files and will be portable across all Java Card implementations From the Java Card virtual machine implementer s perspective each maximum listed indicates a minimum level of support that will allow portability of applets Packages Package References A package can reference at most 128 other packages Package Name The fully qualified name of a package may contain a maximum of 255 characters The package name size is further limited if it contains one or more characters which when represented in UTF 8 format requires multiple bytes Classes Classes in a Package A package can contain at most 255 classes and interfaces Interfaces A class can implement at most 15 interfaces including inter
268. t required to be garbage collected Objects allocated from the heap will not necessarily be reclaimed This specification does not include support for native methods so there are no native method stacks Otherwise the runtime data areas are as documented for the Java virtual machine 3 4 3 2 Contexts Each applet running on a Java Card virtual machine is associated with an execution context The Java Card virtual machine uses the context of the current frame to enforce security policies for inter applet operations There is a one to one mapping between contexts and packages in which applets are defined An easy way to think of a context is as the runtime equivalent of a package since Java packages are compile time constructs and have no direct representation at runtime As a consequence all applet instances from the same package will share the same context Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 The Java Card Runtime Environment also has its own context Framework objects execute in this Java Card RE context The context of the currently executing method is known as the current context Every object in a Java Card virtual machine is owned by a particular context The owning context is the context that was current when the object was created When a method in one context successfully invokes a method on an object in another context the Java Card virtual machine performs a context
269. t the specific constant The format of the additional information varies with the tag value TABLE 5 1 Export File Constant Pool Tags Constant Type Value CONSTANT_Package 13 CONSTANT_Classref 7 CONSTANT_Integer 3 ICONSTANT_Utf8 1 CONSTANT_Package The CONSTANT_Package_info structure is used to represent a package CONSTANT _Package_info ul tag ul flags u2 name_index ul minor_version ul major_version ul aid_length ul aid aid_length Chapter 5 The Export File Format 5 5 The items of the CONSTANT_Package_info structure are the following tag The tag item has the value of CONSTANT_Package 13 flags The flags item is a mask of modifiers that apply to this package The flags modifiers are shown in the following table TABLE 5 2 Export File Package Flags Flags Value ACC_LIBRARY 0x01 The ACC_LIBRARY flag has the value of one if this package does not define and declare any applets In this case it is called a library package Otherwise ACC_LIBRARY has the value of zero If the package is not a library package this export file can only contain shareable interfaces 2 A shareable interface is either the javacard framework Shareable interface or an interface that extends the javacard framework Shareable interface All other flag values are reserved Their values must be zero name_index The value of the name_index item must be a valid index into the c
270. t type COMPONENT_Debug is not intended for download to the device It is intended to be used off card in conjunction with a suitably instrumented Java Card virtual machine 1 Both the Java Card Forum and Global Platform specification have adopted this component load order as a standard to enhance interoperability In both cases loading the Descriptor Component is optional Furthermore the Global Platform specification defines the format of packets APDUs used during installation Chapter6 The CAP File Format 6 5 6 3 Header Component The Header Component contains general information about this CAP file and the package it defines It is described by the following variable length structure header_component ul tag u2 size u4 magic ul minor_version ul major_version ul flags package_info package package_name_info package_name The items in the header_component structure are as follows tag The tag item has the value COMPONENT_Header 1 size The size item indicates the number of bytes in the header_component structure excluding the tag and size items The value of the size item must be greater than zero magic The magic item supplies the magic number identifying the Java Card CAP file format it has the value 0xDECAFFED minor_version major_version The minor_version and major_version items are the minor and major version numbers of this CAP file Together a major and a minor version number det
271. ter 1 Introduction provides an overview of the Java Card virtual machine architecture Chapter 2 A Subset of the Java Virtual Machine describes the subset of the Java programming language and Java Virtual Machine that is supported by the Java Card specification Chapter 3 Structure of the Java Card Virtual Machine describes the differences between the Java virtual machine and the Java Card virtual machine 1 The terms Java Virtual Machine and JVM mean a Virtual Machine for the Java TM platform xviii Virtual Machine Specification Java Card Platform v3 0 Classic Edition March 2008 Chapter 4 Binary Representation provides information about how programs written for the Java Card platform are represented in binary form Chapter 5 The Export File Format describes the export file used to link code against another package Chapter 6 The CAP File Format describes the format of the CAP file Chapter 7 Java Card Virtual Machine Instruction Set describes the bytecodes opcodes that comprise the Java Card virtual machine instruction set Chapter 8 Tables of Instructions summarizes the Java Card virtual machine instructions in two different tables one sorted by Opcode Value and the other sorted by Mnemonic Glossary provides definitions of selected terms in the entire Classic Edition Using UNIX Commands This document might not contain information about basic UNIX comm
272. the javacard framework package must be framework exp Operating systems that impose limitations on file name lengths may transform an export file s name according to their own conventions For a complete description of the Java Card export file format see Chapter 5 The Export File Format CAP File Format A Java Card CAP file contains a binary representation of a package of classes that can be installed on a device and used to execute the package s classes on a Java Card virtual machine A CAP file is produced by a Java Card converter when a package of classes is converted A CAP file consists of a set of components each of which describes a different aspect of the contents The set of components in a CAP file can vary depending on whether the file contains a library or applet definition s For a complete description of the Java Card CAP file format see Chapter 6 The CAP File Format JAR File Container The JAR file format is used as the container format for CAP files What this specification calls a CAP file is just a JAR file that contains the required set of CAP components see Chapter 6 The CAP File Format Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 CAP file components are stored as files in a JAR file Each CAP file component is located in a subdirectory called javacard that is in a directory representing the package For example the CAP file compone
273. the class_component structure excluding the tag and size items The value of the size item must be greater than zero signature_pool_length The signature_pool_length item indicates the number of bytes in the signature_pool item The value of the signature_pool_length item must be zero if the package does not define any remote interfaces or remote classes signature_pool Chapter6 The CAP File Format 6 23 The signature_pool item represents a list of variable length type_descriptor structures These descriptors represent the signatures of the remote methods interfaces The interfaces item represents an array of interface_info structures Each interface defined in this package is represented in the array The entries are ordered based on hierarchy such that a superinterface has a lower index than any of its subinterfaces classes The classes item represents a table of variable length class_info structures Each class defined in this package is represented in the array The entries are ordered based on hierarchy such that a superclass has a lower index than any of its subclasses 6 8 1 type_descriptor The type_descriptor structure represents the type of a field or the signature of a method type_descriptor ul nibble_count ul type nibble_count 1 2 The type_descriptor structure contains the following elements nibble_count The nibble_count value represents the number of nibbles required
274. the static field or static method An internal reference to a static class member is a 16 bit value that is a pointer to the item s location in the CAP file References to instance fields virtual methods and interface methods consist of a class reference and a token of the appropriate type The class reference determines whether the reference is external or internal Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 4 3 5 4 3 6 4 3 7 Installation and Linking External references in a CAP file can be resolved on a device from token form into the internal representation used by the virtual machine A token can only be resolved in the context of the package that defines it Just as the export file maps from a package s externally visible names to tokens there is a set of link information for each package on the device that maps from tokens to resolved references Token Assignment Tokens for an API are assigned by the API s owner and published in the package export file s for that API Since the name to token mappings are published an API owner may choose any order for tokens subject to the constraints listed below A particular device platform can resolve tokens into whatever internal representation is most useful for that implementation of a Java Card virtual machine Some tokens may be resolved to indices For example an instance field token may be resolved to an index into a class in
275. this method is a virtual method the token item represents a virtual method token Section 4 3 7 6 Virtual Methods on page 4 9 If this method is an interface method the token item represents an interface method token Section 4 3 7 7 Interface Methods on page 4 10 access _flags The value of the access_flags item is a mask of modifiers used with methods The access_flags modifiers are shown in the following table TABLE 5 5 Export File Method Access and Modifier Flags Name Value Meaning Used By ACC_PUBLIC 0x0001 Is public may be accessed Any method from outside its package IACC_PROTECTED 0x0004 Is protected may be Class instance accessed within subclasses Imethod ACC_STATIC 0x0008 Is static Class instance method ACC_FINAL 0x0010 Is final no further Class instance overriding or assignment method after initialization ACC_ABSTRACT 0x0400 Is abstract no Any method implementation is provided Method access and modifier flags are defined in the same way and with the same restrictions as described in The Java Virtual Machine Specification Since all methods represented in an export file are either public or protected exactly one of the ACC_PUBLIC or ACC_PROTECTED flag must be set Unlike in Java class files the ACC_NATIVE flag is not supported in export files Whether a method is native is an implementation detail that is not relevant to importing package
276. thod_table_count item is the number of public and protected virtual methods declared by this class If this class defines one or more public or protected override methods the minimum valid value of public_method_table_count item is the value of the largest public or protected virtual method token minus the value of the smallest public or protected virtual override method token plus one The maximum valid value of the public_method_table_count item is the value of the largest public or protected virtual method token plus one Any value for the public_method_table_count item between the minimum and maximum specified here is valid However the value must correspond to the number of entries in the public_virtual_method_table array package_method_table_base The package_method_table_base item of the class_info structure is equal to the virtual method token value Section 4 3 7 6 Virtual Methods on page 4 9 of the first entry in the package_virtual_method_table array If the package_virtual_method_table array is empty the value of the package_method_table_base item is equal to the package_method_table_base item of the class_info structure of this class superclass plus the package_method_table_count item of the class_info structure of this class superclass If this class has no superclass or inherits from a class defined in another package and the package_virtual_method_table array is empty the value of the package_met
277. tive Type Descriptor Values Data Type Value lboolean 0x0002 byte 0x0003 short 0x0004 int 0x0005 reference_type The reference_type item represents a 15 bit offset into the type_descriptor_info structure The item at the offset must represent the reference type of this field As noted above the high bit of the reference_type item is equal to 0 6 13 3 method_descriptor_info The method_descriptor_info structure is used to describe a method defined in this package This structure contains sufficient information to locate and parse the methods in the Method Component while the Method Component does not method_descriptor_info ul token ul access_flags u2 method_offset u2 type_offset u2 bytecode_count u2 exception_handler_count u2 exception_handler_index The items of the method_descriptor_info structure are as follows 6 56 Virtual Machine Specification Java Card Platform v3 0 Classic Edition March 2008 token The token item represents the static method token Section 4 3 7 4 Static Methods and Constructors on page 4 8 or virtual method token Section 4 3 7 6 Virtual Methods on page 4 9 or interface method token Section 4 3 7 7 Interface Methods on page 4 10 of this method If this method is a private or package visible static method a private or package visible constructor or a private virtual method it does not have a token assigned In this case the value of
278. to the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbytel lt lt 8 indexbyte2 The constant pool item at the index must be of type CONSTANT_InstanceFieldref Section 6 7 2 CONSTANT_InstanceFieldref CONSTANT _VirtualMethodref and CONSTANT_SuperMethodref on page 6 18 a reference to a class and a field token The item must resolve to a field of type reference Chapter 7 Java Card Virtual Machine Instruction Set 7 25 The class of objectref must not be an array If the field is protected and it is a member of a superclass of the current class and the field is not declared in the same package as the current class then the class of objectref must be either the current class or a subclass of the current class The item must resolve to a field with a type that matches t as follows m a field must be of type reference a b field must be of type byte or type boolean s field must be of type short m i field must be of type int The width of a field in a class instance is determined by the field type specified in the instruction The item is resolved determining the field offset The value at that offset into the class instance referenced by objectref is fetched If the value is of type byte or type boolean it is sign extended to a short The value is pushed onto the operand stack Runtime Exception If objectref is null the getfield_ lt t gt _w instruction t
279. tract int Format isub Forms isub 68 0x44 Stack valuel word1 value1 word2 value2 word1 value2 word2 gt result word1 result word2 Description Both valuel and value2 must be of type int The values are popped from the operand stack The int result is valuel value2 The result is pushed onto the operand stack For int subtraction a b produces the same result as a b For int values subtraction from zeros is the same as negation Despite the fact that overflow or underflow may occur in which case the result may have a different sign than the true mathematical result execution of an isub instruction never throws a runtime exception Notes If a virtual machine does not support the int data type the isub instruction will not be available itableswitch Access jump table by int index and jump Format itableswitch defaultbyte1 defaultbyte2 lowbyte1 Chapter 7 Java Card Virtual Machine Instruction Set 7 63 7 64 lowbyte2 lowbyte3 lowbyte4 highbyte1 highbyte2 highbyte3 highbyte4 jump offsets Offset Format offsetbyte1 offsetbyte2 Forms itableswitch 116 0x74 Stack index gt Description An itableswitch instruction is a variable length instruction Immediately after the itableswitch opcode follow a signed 16 bit value default a signed 32 bit value low a signed 32 bit value high an
280. ts or arrays These exceptions are detailed in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 Classic Edition An important detail to note is that any cross context method invocation will result in a context switch Section 3 4 Contexts on page 3 2 The Java Card virtual machine may also throw a SecurityException if an instruction violates any of the static constraints of Chapter 6 The CAP File Format The Virtual Machine Specification Java Card Platform Version 3 0 Classic Edition does not mandate which instructions must implement these additional security checks or to what level Therefore a SecurityException may be thrown at any time during the operation of the Java Card virtual machine 79 The Java Card Virtual Machine Instruction Set Java virtual machine instructions are represented in this chapter by entries of the form shown in TABLE 7 1 an example instruction page in alphabetical order Chapter 7 Java Card Virtual Machine Instruction Set 7 3 TABLE 7 1 Example Instruction Page mnemonic Short description of the instruction Format mnemonic operand1 operand2 Forms mnemonic opcode Stack valuel value2 gt value3 Description A longer description detailing constraints on operand stack contents or constant pool entries the operation performed the type of the results and so on Runtime Exception If any runtime exceptions can be thrown
281. ts the static install byte short byte method of the applet The install byte short byte method must be defined in a class that extends the javacard framework applet class directly or indirectly The install byte short byte method is called to initialize the applet 6 6 Import Component The Import Component lists the set of packages imported by the classes in this package It does not include an entry for the package defined in this CAP file The Import Component is represented by the following structure import_component ul tag u2 size ul count package_info packages count 3 Restrictions placed on the install byte short byte method of an applet are imposed by the Runtime Environment Specification Java Card Platform Version 3 0 Chapter6 The CAP File Format 6 13 The items in the import_component structure are as follows tag The tag item has the value COMPONENT_Import 4 size The size item indicates the number of bytes in the import_component structure excluding the tag and size items The value of the size item must be greater than zero count The count item indicates the number of items in the packages table The value of the count item must be between 0 and 128 inclusive packages The packages item represents a table of variable length package_info structures as defined for package under Section 6 3 Header Component on page 6 6 The table contains an entr
282. tual machine specification does not support multi dimensional arrays Therefore neither SC or TC can be an array type Chapter 7 Java Card Virtual Machine Instruction Set 7 19 Format dup Forms dup 61 0x3d Stack word gt word word Description The top word on the operand stack is duplicated and pushed onto the operand stack The dup instruction must not be used unless word contains a 16 bit data type Notes Except for restrictions preserving the integrity of 32 bit data types the dup instruction operates on an untyped word ignoring the type of data it contains 7 5 18 dup_x Duplicate top operand stack words and insert below Format dup_x mn Forms dup_x 63 0x3f Stack WordN wordM word1 gt wordM word1 wordN wordM word1 Description 7 20 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 7 9 19 The unsigned byte mn is used to construct two parameter values The high nibble mn amp Oxf0 gt gt 4 is used as the value m The low nibble mn amp Oxf is used as the value n Permissible values for m are 1 through 4 Permissible values for n are 0 and m through m 4 For positive values of n the top m words on the operand stack are duplicated and the copied words are inserted n words down in the operand stack When n equals 0 the top m words are copied and placed on top of the sta
283. type byte or of type boolean The index must be of type short Both arrayref and index are popped from the operand stack The byte value in the component of the array at index is retrieved sign extended to a short value and pushed onto the top of the operand stack Runtime Exceptions If arrayref is null baload throws a NullPointerException Otherwise if index is not within the bounds of the array referenced by arrayref the baload instruction throws an ArrayIndexOutOfBoundsException Notes In some circumstances the baload instruction may throw a SecurityException if the current context Section 3 4 Contexts on page 3 2 is not the owning context Section 3 4 Contexts on page 3 2 of the array referenced by arrayref The exact circumstances when the exception will be thrown are specified in Chapter 6 of the Runtime Environment Specification Java Card Platform Version 3 0 bastore Store into byte or boolean array Format bastore Forms bastore 56 0x38 Stack arrayref index value gt Description The arrayref must be of type reference and must refer to an array whose components are of type byte or of type boolean The index and value must both be of type short The arrayref index and value are popped from the operand stack The short value is truncated to a byte and stored as the component of the array indexed by index Runtime Exceptions Chapter 7 Java Card Virtual Machine Instruction S
284. ue of an entry in the component_sizes array is zero for components not included in this CAP file Components that may not be included are the Applet Component Section 6 5 Applet Component on page 6 12 the Export Component Section 6 12 Export Component on page 6 49 and the Debug Component Section 6 14 Debug Component on page 6 59 For all other components the value is greater than zero static_field_size The static_field_size item is a static_field_size_info structure The structure is defined as static_field_size_info u2 image_size u2 array_init_count u2 array_init_size The items in the static_field_size_info structure are the following image_size The image_size item has the same value as the image_size item in the Static Field Component Section 6 10 Static Field Component on page 6 42 It represents the total number of bytes in the static fields defined in this package excluding final static fields of primitive types array_init_count The array_init_count item has the same value as the array_init_count item in the Static Field Component Section 6 10 Static Field Component on page 6 42 It represents the number of arrays initialized in all of the lt clinit gt methods in this package array_init_size The array_init_size item represents the sum of the count items in the array_init table item of the Static Field Component Section 6 10 Static Field Component on
285. ump Format stableswitch defaultbyte1 defaultbyte2 lowbyte1 lowbyte2 highbyte1 highbyte2 jump offsets Offset Format offsetbyte1 offsetbyte2 Forms stableswitch 115 0x73 Stack Chapter 7 Java Card Virtual Machine Instruction Set 7 95 index gt Description A stableswitch instruction is a variable length instruction Immediately after the stableswitch opcode follow a signed 16 bit value default a signed 16 bit value low a signed 16 bit value high and then high low 1 further signed 16 bit offsets The value low must be less than or equal to high The high low 1 signed 16 bit offsets are treated as a 0 based jump table Each of the signed 16 bit values is constructed from two unsigned bytes as bytel lt lt 8 byte2 The index must be of type short and is popped from the stack If index is less than low or index is greater than high than a target address is calculated by adding default to the address of the opcode of this stableswitch instruction Otherwise the offset at position index low of the jump table is extracted The target address is calculated by adding that offset to the address of the opcode of this stableswitch instruction Execution then continues at the target address The target addresses that can be calculated from each jump table offset as well as the one calculated from default must be the address of an opcode of an inst
286. va platform is required to understand the Java Card platform 2 1 22l 2 2 1 1 2 2 The items discussed in this section are not described to the level of a language specification For complete documentation on the Java programming language see The Java Language Specification Unsupported Items The items listed in this section are elements of the Java programming language and platform that are not supported by the Java Card platform Unsupported Features Dynamic Class Loading Dynamic class loading is not supported in the Java Card platform An implementation of the Java Card platform is not able to load classes dynamically Classes are either masked into the card during manufacturing or downloaded through an installation process after the card has been issued Programs executing on the card may only refer to classes that already exist on the card since there is no way to download classes during the normal execution of application code Security Manager Security management in the Java Card platform differs significantly from that of the Java platform In the Java platform there is a Security Manager class java lang SecurityManager responsible for implementing security features In the Java Card platform language security policies are implemented by the virtual machine There is no Security Manager class that makes policy decisions on whether to allow operations Finalization Finalization is also not supported finalize
287. vered by and information contained in this service manual are controlled by U S Export Control laws and may be subject to the export or import laws in other countries Nuclear missile chemical biological weapons or nuclear maritime end uses or end users whether direct or indirect are strictly prohibited Export or reexport to countries subject to U S embargo or to entities identified on U S export exclusion lists including but not limited to the denied persons and specially designated nationals lists is strictly prohibited DOCUMENTATION IS PROVIDED AS IS AND ALL EXPRESS OR IMPLIED CONDITIONS REPRESENTATIONS AND WARRANTIES INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE OR NON INFRINGEMENT ARE DISCLAIMED EXCEPT TO THE EXTENT THAT SUCH DISCLAIMERS ARE HELD TO BE LEGALLY INVALID Copyright 2008 Sun Microsystems Inc 4150 Network Circle Santa Clara California 95054 Etats Unis Tous droits r serv s Sun Microsystems Inc d tient les droits de propri t intellectuelle relatifs la technologie incorpor e dans le produit qui est d crit dans ce document En particulier et ce sans limitation ces droits de propri t intellectuelle peuvent inclure un ou plusieurs des brevets am ricains list s a l adresse http www sun com patents et un ou plusieurs des brevets suppl mentaires ou des applications de brevet en attente aux Etats Unis et dans les autres pays Droits de gouvernement de
288. x in the constant pool must be of type CONSTANT_Classref Section 6 7 1 CONSTANT_Classref on page 6 17 a reference to a class or interface type The reference is resolved and must result in a class type it must not result in an interface type Memory for a new instance of that class is allocated from the heap and the instance variables of the new object are initialized to their default initial values The objectref a reference to the instance is pushed onto the operand stack Notes Chapter 7 Java Card Virtual Machine Instruction Set 7 67 The new instruction does not completely create a new instance instance creation is not completed until an instance initialization method has been invoked on the uninitialized instance 7 5 71 newarray Create new array Format newarray atype Forms newarray 144 0x90 Stack count gt arrayref Description The count must be of type short It is popped off the operand stack The count represents the number of elements in the array to be created The unsigned byte atype is a code that indicates the type of array to create It must take one of the following values TABLE 7 4 Array Values Array Type atype _BOOLEAN 10 T_BYTE 11 IT_SHORT 12 ITT_INT 13 A new array whose components are of type atype of length count is allocated from the heap A reference arrayref to this new array object is pushed onto the operand stac
289. xbytel lt lt 8 indexbyte2 The constant pool item at the index must be of type CONSTANT_StaticFieldref Section 6 7 3 CONSTANT_StaticFieldref and CONSTANT_StaticMethodref on page 6 20 a reference to a static field The item must resolve to a field with a type that matches t as follows m a field must be of type reference a b field must be of type byte or type boolean a s field must be of type short a i field must be of type int The width of a class field is determined by the field type specified in the instruction The item is resolved determining the field offset The item is resolved determining the class field The value of the class field is fetched If the value is of type byte or boolean it is sign extended to a short The value is pushed onto the operand stack Notes If a virtual machine does not support the int data type the getstatic_i instruction will not be available goto Branch always Chapter 7 Java Card Virtual Machine Instruction Set 7 27 Format goto branch Forms goto 112 0x70 Stack No change Description The value branch is used as a signed 8 bit offset Execution proceeds at that offset from the address of the opcode of this goto instruction The target address must be that of an opcode of an instruction within the method that contains this goto instruction 7 5 25 goto_w Branch always wide index Format goto_w branchbyte1 branchbyte2
290. xp For example the name of the export file of the javacard framework package must be framework exp Operating systems that impose limitations on file name lengths may transform an export file s name according to its conventions 32 Containment in a JAR File As described in Section 4 1 3 JAR File Container on page 4 2 Java Card CAP files are contained in a JAR file If an export file is also stored in a JAR file it must also be located in a directory called javacard that is a subdirectory of the package s directory For example the framework exp file would be located in the subdirectory javacard framework javacard 5 3 5 2 Ownership An export file is owned by the entity that owns the package it represents The owner of a package defines the API of that package and may or may not provide all implementations of that package All implementations however must conform to the definition provided in the export file provided by the owner A particular example of export file ownership is the Java Card API packages Sun Microsystems Inc defines these packages Sun Microsystems Inc also provides the export files for these packages All implementations of the Java Card API packages must conform to the definitions provided by Sun Microsystems Inc and comply with the token assignments provided in these export files Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 5 4 Hie
291. y except static final fields of primitive types Inherited fields are not included in the array methods The methods item represents an array of method_descriptor_info structures Each method declared or defined by this class or interface is represented in the array For a class inherited methods are not included in the array For an interface inherited methods are included in the array field_descriptor_info The field_descriptor_info structure is used to describe a field defined in this package field_descriptor_info ul token ul access_flags union static_field_ref static_field class_ref class ul token instance_field field_ref union u2 primitive_type Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 u2 reference_type type The items of the field_descriptor_info structure are as follows token The token item represents the token of this field If this field is private or package visible static field it does not have a token assigned In this case the value of the token item must be OxFF access flags The access_flags item is a mask of modifiers used to describe the access permission to and properties of this field The access_flags modifiers for fields are shown in the following table TABLE 6 19 CAP File Field Descriptor Flags Name Value ACC_PUBLIC 0x01 ACC_PRIVATE 0x02 ACC_PROTECTED 0x04 ACC_STATIC 0x0
292. y the interface java rmi Remote a Each method declaration in the remote interface or its super interfaces includes the exception java rmi RemoteException or one of its superclasses in its throws clause a Ina remote method declaration if a remote object is declared as a return type it is declared as the remote interface not the implementation class of that interface In addition Java Card RMI imposes additional constraints on the definition of remote methods These constraints are as a result of the Java Card platform language subset and other feature limitations For more information see Section 2 2 6 2 Access Control of Remote Interfaces on page 2 12 and Section 2 2 6 3 Parameters and Return Values on page 2 13 Access Control of Remote Interfaces The Java RMI system supports the package access control defined in the Java language However Java Card RMI does not support package visible remote interfaces Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 2 2 6 3 Parameters and Return Values The parameters of a remote method must only include parameters of the following types m Any primitive type supported by Java Card technology boolean byte short int m Any single dimension array type of an primitive type supported by Java Card technology boolean byte short int The return type of a remote method must only be one of the following types m Any prim
293. y 3 constant pool component of a CAP file 6 14 constant types 6 16 CONSTANT_Classref 5 7 6 17 CONSTANT_InstanceFieldref 6 18 CONSTANT_Integer 5 7 CONSTANT _Package 5 5 constant_pool 5 5 CONSTANT _StaticFieldref 6 20 CONSTANT_StaticMethodref 6 20 CONSTANT_SuperMethodref 6 18 CONSTANT_Ut 8 structure 5 8 CONSTANT_VirtualMethodref 6 18 ConstantValue attribute 5 16 context 3 2 Glossary 3 current 3 3 owning 3 3 Index 2 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 context switch 3 3 Glossary 3 continue 2 7 converted applet CAP file 1 3 4 1 Converter 1 2 Glossary 3 Converter tool 3 4 current context 3 3 currently active context Glossary 3 currently selected applet Glossary 3 custom CAP file component Glossary 3 D data type 3 1 integer 2 8 debug component of a CAP file 6 59 default 2 7 default applet Glossary 3 deletion 2 8 descriptor component of a CAP file 6 51 directory component of a CAP file 6 9 directory_component structure of a CAP file 6 9 do 2 7 double 2 4 dup 7 19 dup_x 7 20 dup2 7 21 dynamic class loading 2 2 dynamic object creation 2 5 E EEPROM Glossary 3 Electrically Erasable Programmable Read Only Memory Glossary 3 else 2 7 entry point objects Glossary 4 errors 2 21 7 2 exception_handler_info 6 38 ExceptionIninitializerError 2 21 exceptions 2 6 2 19 3 4 7 3 c
294. y for each of the packages referenced in the CAP file not including the package defined The major and minor version numbers specified in the package_info structure are equal to the major and minor versions specified in the imported package s export file See Section 4 5 Package Versions on page 4 13 for a description of assigning and using package version numbers Components of this CAP file refer to an imported package by using a index in this packages table The index is called a package token Section 4 3 7 1 Package on page 4 8 6 7 Constant Pool Component The Constant Pool Component contains an entry for each of the classes methods and fields referenced by elements in the Method Component Section 6 9 Method Component on page 6 36 of this CAP file The referencing elements in the Method Component may be instructions in the methods or exception handler catch types in the exception handler table Entries in the Constant Pool Component reference elements in the Class Component Section 6 8 Class Component on page 6 22 Method Component Section 6 9 Method Component on page 6 36 and Static Field Component Section 6 10 Static Field Component on page 6 42 The Import Component Section 6 6 Import Component on page 6 13 is also accessed using a package token 6 14 Virtual Machine Specification Java Card Platform v3 0 Classic Edition e March 2008 Section 4 3 7 1 Package
295. y represent must be consistent with those of the selected instance method The nargs 1 words of arguments and objectref are popped from the operand stack A new stack frame is created for the method being invoked and objectref and the arguments are made the values of its first nargs words of local variables with objectref in local variable 0 arg1 in local variable 1 and so on The new stack frame is then made current and the Java Card virtual machine pc is set to the opcode of the first instruction of the method to be invoked Execution continues with the first instruction of the method Runtime Exception If objectref is null the invokespecial instruction throws a NullPointerException invokestatic Invoke a class static method Format invokestatic indexbytel1 indexbyte2 Chapter 7 Java Card Virtual Machine Instruction Set 7 55 Forms invokestatic 141 0x8d Stack arg arg2 gt Description The unsigned indexbytel and indexbyte2 are used to construct an index into the constant pool of the current package Section 3 5 Frames on page 3 3 where the value of the index is indexbytel lt lt 8 indexbyte2 The constant pool item at that index must be of type CONSTANT_StaticMethodref Section 6 7 3 CONSTANT_StaticFieldref and CONSTANT_StaticMethodref on page 6 20 a reference to a static method The method must not be lt init gt an instance initialization method o

JavaCard Virtual Machine Specification, Version 3.0

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