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GNATforLEON / ORK+ User Manual - dit/UPM

1. 2 Software overview 9 21 The ORK kernel 9 2 2 Architecture of ORK 10 2 3 Interface for 12 2 4 Interface for C programs o o tie Ze aom redes rns T PE N dete d 12 2 5 Hardware and software environment 12 2 5 1 Development platform 12 2 5 2 Execution platform 13 3 How to use GNATforLEON 15 3 1 Software development 2 22 ae Sak yug 15 3 2 Writing Ada programs 15 3 2 1 Ravenscar profile 15 3 2 2 The GNAT configuration 17 3 2 3 A first examples e aci e BE ee E AUG gie RUE S 18 3 9 Compiling and linking Ada programs 21 3 4 Debugging Ada programs 22 3 5 Executing programs on the target platform 23 3 5 1 Floating point considerations 3 5 2 Making boot PROMS 3 5 3 Using GDB with GRMON and the remote target monitor 3 6 Interrupt 3 6 1 Protected procedure handlers 3 6 2 An example with interrupts 3 7 Working with C programs sap AINT EL a tee y rear RUP dires 3 7 2 ORK amp CIL limitations 3 7 3 A
2. CHAPTER 3 HOW TO USE GNATFORLEON Restricted GNARL and ORK ALI Restricted GNARL ORK Application Ada Library Information files and other library files compilation units ali E ads Application ALI Ada adb Library Information ELF 32 SPARC gnat adc Era Application objects RU ads Restricted GNARL and ORK specifications Figure 3 1 Compilation flow for GNATforLEON ORK applications Task types and object declarations other than at the library level Dynamic allocation and unchecked deallocation of protected and task objects Requeue statement ATC asynchronous transfer of control via the asynchronous select state ment Abort statements including Abort Task in package Ada Task Identification Task entries Dynamic priorities Ada Calendar package Relative delays Execution time timers and group budgets Non local timing events Protected types and object declarations other than at the library level Protected types with more than one entry Protected entries with barriers other than a single boolean variable declared within the same protected type Entry calls to a protected entry with a call already queued Asynchronous task control All forms of select statements 2As an exception to the Ravenscar profile ORK supports one execution time timer per task and group b
3. 11 BB Parameters lt lt component gt gt Bare Board Kernel Kernel Protection I 1 O BB Protection I Thread Management T e BB Threads BB CPU_Primitives Synchronization Scheduling O BB Threads Queues Interrupt Handling I 1 BB Interrupts I I BB Time Time Services BB Peripherals BB Time Execution Time Serial Output BB Peripherals Registers e BB Serial Output Figure 2 2 Architecture Figure 2 1 Architecture of ORK 1 1 Ada Application 1 1 Application GNULL Hardware GDB DDD of the GNAT GCC run time system based on ORK4 12 CHAPTER 2 SOFTWARE OVERVIEW 2 3 Interface for Ada programs Ada tasking is implemented in GNAT by means of the run time library called GNARL Giering and Baker 1994 The parts of GNARL which are dependent on a particular machine and operating system are known as GNULL and its in terface to the platform independent part of the GNARL is called GNULLI The GNATforLEON instance of GNULL is built on top of the bare board kernel i e ORK which provides all the low level tasking support functionality required by the Ravenscar profile subset of Ada taski
4. Interrupt constant System BB Parameters Interrupt Levels The interrupts are distinguished by its interrupt level subtype Interrupt ID is Natural range 0 Max Interrupt Interrupt identifier No_Interrupt constant Interrupt_ID 0 Special value indicating no interrupt type Interrupt Handler is access procedure ld Interrupt ID 42 KERNEL INTERFACE 43 Prototype of procedures used as low level handlers procedure Initialize Interrupts Initialize table containing the pointers to the different interrupt stacks Should be called before any other subprograms in this package procedure Attach Handler Handler Interrupt Handler Id Interrupt ID pragma Inline Attach Handler pragma Export C Attach Handler system bb attach interrupt handler Attach the procedure Handler as handler of the interrupt ld function Priority Of Interrupt Id Interrupt ID return System Any Priority renames System BB Peripherals Priority Of Interrupt This function returns the software priority associated to the interrupt given as argument function Current Interrupt return Interrupt ID pragma Inline Current Interrupt Function that returns the hardware interrupt currently being handled if any In case no hardware interrupt is being handled the returned value is No Interrupt function Within Interrupt Stack Stack Address System Address return Bo
5. 4 2 2 Threads and synchronization The operations related with the initialization of the kernel thread management synchronization and scheduling are implemented in the package System BB Threads Listing 4 1 Specification of System BB T hreads Package that implements basic tasking functionalities pragma Restrictions No Elaboration Code with System Used for Address gt Null_Address Any Priority with System Parameters Used for Size Type with System BB CPU Primitives Used for Context Buffer 42 KERNEL INTERFACE 35 with System BB Time Used for Time with System BB Interrupts Used for Interrupt Set Empty Interrupt Set package System BB Threads is pragma Preelaborate type Thread Descriptor This type contains the information about a thread type Thread ld is access all Thread Descriptor Type used as thread identifier Null Thread ld constant Thread ld null pragma Export C Null_Thread_Id system bb null thread id Identifier used to define an invalid value for a thread identifier type Thread States is Runnable Suspended Delayed These are the three possible states for a thread under the Ravenscar profile restrictions Runnable not blocked and it may also be executing Suspended waiting on an entry call and Delayed waiting on a delay until statement type Exec Handler is access procedure Inte
6. upper 40 bits representing the number of clock periods MSP and the lower 24 bits containing the number of hardware clock ticks LSP type Time Span is range 2 xx 63 2 xx 63 1 for Time Span Size use 64 Time_Span represents the length of time intervals and it is defined as a 64 bit signed integer Tick constant 1 A clock tick is a real time interval during which the clock value as observed by calling the Clock function remains constant Tick is the average length of such intervals Ticks Per Second constant System BB Peripherals Timer Freq Hz Number of ticks or clock interrupts per second procedure Initialize_Timers 42 KERNEL INTERFACE 41 Initialize this package clock and alarm handlers Must be called before any other functions function Number Of Ticks Per Second return Time pragma Export C Number Of Per Second system bb ticks per second Get the number of ticks or clock interrupts per second function Clock return Time pragma Export C Clock system bb clock Get the number of ticks elapsed since startup procedure Delay Until T Time pragma Export C Delay Until system bb delay until Suspend the calling thread until the absolute time specified by function Left Time Right Time Span return Time function Get Pending Alarm return Boolean Returns Pendin
7. Thus it is not the intent of this section to claim rights or contest your rights to work written entirely by you rather the intent is to exercise the right to control the distribution of derivative or collective works based on the Program In addition mere aggregation of another work not based on the Program with the Program or with a work based on the Program on a volume of a storage or distribution medium does not bring the other work under the scope of this License 3 You may copy and distribute the Program or a work based on it under Section 2 in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following a Accompany it with the complete corresponding machine readable source code which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange or b Accompany it with a written offer valid for at least three years to give any third party for a charge no more than your cost of physically per forming source distribution a complete machine readable copy of the corresponding source code to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange or c Accompany it with the information you received as to the offer to dis tribute corresponding source code This alternative is allowed only for noncommercial distribution and only if you received the p
8. POLIT CNICA GNATforLEON ORK4 User Manual Version 1 3 30 July 2009 For GNATFORLEON 2 1 0 ORK UNIVERSIDAD POLIT CNICA DE MADRID GRUPO DE SISTEMAS DE TIEMPO REAL Y ARQUITECTURA DE SERVICIOS TELEM TICOS 2008 2009 Universidad Polit cnica de Madrid UPM Published by Departamento de Ingenier a de Sistemas Telem ticos Universidad Polit cnica de Madrid ETSI Telecomunicaci n Ciudad Universitaria E 28040 Madrid SPAIN Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission noice are preserved on all copies Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying provided also that the sections entitled Copying and GNU General Public License see appendix D are included exactly as in the original and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one Permission is granted to copy and distribute translations of this manual into another language under the above conditions for modified versions except that this permission notice may be stated in a translation approved by the Free Software Foundation This manual has been adapted to GNATforLEON from the Operation Manual for the Open Raven scar Real Time Kernel ORK The original software and its associated documentation were de veloped at UPM under ESA contra
9. other private operations and data end Interrupt Notice that you should assign a ceiling priority to the protected object with a pragma Interrupt Priority You should use a priority level equal or greater than the hardware priority of the interrupt source Notice that the corresponding hardware priority levels have also been declared in the package Ada Interrupt Names Warning 3 3 You should only use priorities in the Interrupt Priority range for protected objects that contain interrupt handlers ALRM C 3 1 3 6 2 An example with interrupts Appendix B describes an example application with interrupt handlers 3 7 Working with C programs 3 7 1 The C interface ORK can be used from C programs through the CIL C Interface Layer see figure 2 2 on page 11 The CIL consists of some header files that contain the appropriate types and function definitions which are needed to interface with the ORK kernel These files are e gnatforleon h e system bb interrupts h e system bb serial output h e system bb threads h 26 CHAPTER 3 HOW TO USE GNATFORLEON e system bb time h e types h 3 7 2 ORK amp CIL limitations A C program for the ORK kernel can be divided into any number of c and h files just like any ordinary C program However the following issues should be taken into account e The Ravenscar profile restrictions cannot be enforced at compilation time by any means so the assurance of conformance of the ap
10. Any other configuration pragma can be included here A copy of this file is included in the examples directory for your convenience Of course you should add any additional restrictions you would like to enforce on your program Notice that the maximum number of application tasks is bounded by a kernel configuration parameter see section 4 5 for the details 3GNATforLEON ORK allows priorities to be shared as long as it is compatible with the ceiling locking policy but this is not a commendable practice unless the task and protected object population exceeds the allowable range of priorities See section 4 5 on how to configure the range of priorities and the maximum number of tasks The directory examples is located directly under the directory where you have installed the gnatforleon distribution usr local gnatforleon in a standard installation 18 CHAPTER 3 HOW TO USE GNATFORLEON environment Background Periodic Sporadic priority 0 priority 1 priority 2 Signal Event ceiling priority 2 Figure 3 2 Task structure of the hello program see 3 2 3 Parallelograms repre sent tasks and rounded rectangles represent protected objects The arrows denote procedure or entry calls 3 2 3 A first example Let us now see a simple Ravenscar compliant Ada program The program consists of two compilation units the main procedure file hello adb and a package with all the application
11. Sparc elf gnatxref Ada utility to generating a full report of all cross references sparc elf 1d linker sparc elf nm utility to print symbol table sparc elf objcopy utility to convert between binary formats sparc elf objdump utility to dump various parts of executables sparc elf ranlib library sorter sparc elf size utility to display segment sizes sparc elf strings utility to dump strings from executables sparc elf strip utility to remove symbol table 34 CHAPTER 4 GNATFORLEON ORK REFERENCE 4 1 6 Documentation Extensive documentation for all the tools can be found in the the usr local gnatforleon info and usr local gnatforleon man directories Documentation for the LEON2 processor can be found at the Aeroflex Gaisler site located at http www gaisler com 4 2 Kernel interface 4 2 1 Introduction The ORK kernel provides all the required functionality to support real time pro gramming on top of the LEON2 hardware architecture The kernel functions are grouped as follows 1 Task management including task creation synchronization and scheduling 2 Time services including absolute delays and real time clock 3 Interrupt handling All these functions are described in the following subsections The kernel is normally used as a low level layer providing the basic functionality to the upper GNAT run time system However it can be used directly from an application program written in either Ada or C
12. be calculated The minimum inter arrival time will be used as the period in order to calculate the worst case response time for the low priority task Following common practice an initial value w equal to the sum of the WCET of higher priority task plus the WCET of the task itself is used w 34 6 9 9 1 wi 6 6 5 15 Diy koa Jane 3 18 wi 14 x 18 3 1 6 6 ES 8 17 17 1 gt faro w 8 Fa x3 E x 6 20 20 20 2 far 8 x3 x6 20 Figure B 2 shows the schedule of the tasks starting at time zero for 60 time units of 100ms each Up arrows denote activation time and down arrows denote deadlines Filled boxes denote sections executed at ceiling priority 56 APPENDIX B EXAMPLE PROGRAM i Task A Y Y Task B 1 Y Y 2 A E 0 5 10 15 20 25 30 35 40 45 50 55 60 time units Figure B 2 Schedule of tasks B 4 Example program output The output of the example program shows the start and termination time of each task cycle You can use TSIM for executing it the options freq 41 fast uart can be used to set the clock frequency defined in System BB Parameters and to set infinite speed in the UART channel With a time unit of 100ms the actual output is tsim leon freq 41 fast uart demo TSIM LEON SPARC simula
13. clocked by the internal processor clock and they use a two stage counter In order to provide a high resolution clock the least significant part of the clock is held in the Real Time Clock hardware register and the Real Time Clock is programmed to interrupt periodically updating the most significant part of the clock As a result the clock tick is equal to the period of the input signal of the downcounter divided by the prescaler That is the processor clock period divided by 4 in the current implementation The underlying implementation is described in depth in Zamorano et al 2001 ALRM D 8 35 Synchronization with external sources The implementation shall document whether or not there is any synchronization with external time references and if such synchronization exists the sources of syn chronization information the frequency of synchronization and the synchronization method applied The system does not synchronize with any external source ALRM D 8 36 Interference from the external environment The implementation shall document any aspects of the external environment that could interfere with the clock behavior as defined in this clause The clock value is a count of ticks since the clock was started therefore its behavior only is affected by the manufacturing drift of the hardware clock C 1 ADA LRM ANNEX C AND D METRICS 67 ALRM D 8 39 45 Real time clock metrics For the purpose of the metrics defined in t
14. e Interrupt Stack Size Size of the interrupt stack e Clock Frequency Frequency of the LEON2 processor It is also possible to configure the priority ranges by modifying the file system xi sparc full ads and then rebuilding the cross compilation system The configurable parameter which defines the memory space available in the board is included in the linker script file sparcleon sc which can be found in the usr local gnatforleon src binutils 2 16 1 1d scripttempl directory You can edit that file and change the RAM SIZE value There is no need to rebuild the GNATforLEON cross compilation system when this parameter is changed The maximum number of tasks is not configurable The number of tasks is limited by the task stack size and the amount of storage available As the storage space needed for tasks is allocated at compilation time if there is not enough memory a linker error message will be output 4 5 2 Interrupt names The interrupt names have been defined in ORK as close as possible to the names given in the Rad Hard 32 bit SPARC V8 Proccesor AT697E DataSheet ATMEL 2005 For example the ORK name Timer_2 denotes the Timer 2 time out in terrupt The ORK interrupt names are defined in System BB Peripherals These names are available to GNARL by appropriate renames in the GNULL package System OS Interface As a result the standard Ada package Ada Interrupts Names contains the following interrupt names e Timer_1 This i
15. internal execution time of task C and cz to the execution time of task C inside resource Monitor Finally b corresponds to the whole execution of task B By extension the same set of symbols denote the WCET of the corresponding block of activity Table B 2 shows the priorities assigned to the tasks Task A has the highest priority task C has the lowest priority task B has a medium priority Schedulability analysis The Ravenscar profile includes pragma Task Dispatching Policy FIFO Within Priorities and pragma Locking Policy Ceiling Locking see appendix A B 3 SCHEDULABILITY ANALYSIS 55 Task block Priority WCET Resource A a1 Priority Last 1 None Priority Last 2 Monitor B bi Priority Last 1 6 None C e Priority Last 2 2 None C Priority Last 6 Monitor Table B 2 Priority assignment and Worst Case Execution Time of activities Therefore the maximum response time of every task can be evaluated using equa tion B 1 R jehp i J Which is solved using a recurrence relation v GAB M ES x jehp i J As immediate ceiling locking is used the maximum blocking time can be evalu ated for every task Task A can suffer a blocking time equal to WCET of activity ca i e 6 Task B can suffer a blocking time equal to WCET of activity ca i e B 6 Task C is the lowest priority task and so can not suffer blocking i e 0 The maximum response time of every task can now
16. is possible to selectively rebuild only the GNATforLEON adalib However GNATforLEON must have been previously compiled in order to do this If the GNATforLEON cross compilation system has been built previously the subdirectories called tmp gcc 4 1 3 build must already exist in usr local gnatforleon src It is then possible to rebuild only the GNATforLEON adalib by typing make adalib in the usr local gnatforleon src directory Warning 4 1 You will need a native GNAT GPL 2008 distribution installed on your computer in order to rebuild or adapt GNATforLEON 2 1 0 Appendix A The Ravenscar profile A 1 Introduction The Ravenscar Profile is the best known result of the 8th International Real Time Ada Workshop IRTAW 8 which was held in April 1997 in Ravenscar Yorkshire Baker and Vardanega 1997 Burns and Wellings 1997 Burns et al 1998 The purpose of the profile is to identify a subset of the tasking features of Ada which can be implemented using a small reliable kernel The expected benefits of this approach are e Improved memory and execution time efficiency by removing features with a high overhead e Improved reliability by removing non deterministic and non analysable fea tures e Improved timing analysis by removing non deterministic and non analysable features The profile was revised at subsequent meetings including IRTAW 9 Asplund et al 1999 IRTAW 10 Wellings 2001 IRTAW 11 Burns and Brosgo
17. licenses terminated so long as such parties remain in full compliance You are not required to accept this License since you have not signed it How ever nothing else grants you permission to modify or distribute the Program or its derivative works These actions are prohibited by law if you do not ac cept this License Therefore by modifying or distributing the Program or any work based on the Program you indicate your acceptance of this License to do so and all its terms and conditions for copying distributing or modifying the Program or works based on it Each time you redistribute the Program or any work based on the Program the recipient automatically receives a license from the original licensor to copy distribute or modify the Program subject to these terms and conditions You may not impose any further restrictions on the recipients exercise of the rights granted herein You are not responsible for enforcing compliance by third parties to this License If as a consequence of a court judgment or allegation of patent infringement or for any other reason not limited to patent issues conditions are imposed on you whether by court order agreement or otherwise that contradict the conditions of this License they do not excuse you from the conditions of this License If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations then as a consequen
18. most significant part of the clock The current value of the real time clock can be obtained calling function Clock This function returns the number of ticks elapsed since system startup providing a time zone independent monotonically increasing absolute time value The number of ticks or clock interrupts per second can be read from the con stant called Ticks_Per_Second When a thread needs to be suspended until an absolute time the procedure Delay_Until is called The effect of this call is the suspension of the calling thread until the value of the clock is equal to or greater than the specified time If the alarm time is not in the future the ownership of the processor is transferred to the next ready thread with the currently active priority The reader should notice that this arrangement also provides support for execution time clocks and timers group budgets and timing events Urue a et al 2007 4 2 4 Interrupt handling Interrupt names and operations are declared in the package System BB Interrupts Listing 4 3 Specification of System BB Interrupts Package in charge of implementing the basic routines for interrupt management pragma Restrictions No Elaboration Code with System Used for Any Priority with System BB Parameters Used for Interrupt Levels with System BB Peripherals Used for Priority Of Interrupt package System BB Interrupts is pragma Preelaborate
19. of the calling thread procedure Set Priority Priority System Any Priority pragma Inline Set Priority pragma Export C Set Priority system bb set priority Set the active priority of the executing thread to the given value function Get Priority ld Thread Id return System Any Priority pragma Inline Get Priority pragma Export C Get Priority system bb get priority Get the current active priority of any thread procedure Sleep pragma Export C Sleep system bb sleep The calling thread is unconditionally suspended procedure Wakeup ld Thread 14 pragma Export C Wakeup system bb wakeup Thread ld becomes ready the thread must be previously suspended procedure Set ATCB ATCB System Address pragma Inline Set ATCB This procedure sets the ATCB passed as argument for the currently running thread function Get AT CB return System Address pragma Inline Get AT CB Returns the ATCB of the currently executing thread Execution Time functions type Handler is access protected procedure Integer Global TM Pointer Integer 1 Global GB Pointer Integer 1 Budget Array array 1 255 of System BB Time Time Span 42 KERNEL INTERFACE 39 function Get Timer ld return Integer function Get GB ld return Integer Global TE Pointer Integer 1 function Get Id return Integer type Alarm Q
20. previous priority system bb get priority amp periodic task pthread mutez Lock system bb set priority mutex priority It is needed to know what is the awaiting task pthread condition signal mutex barrier true system bb wakeup amp sporadic task pthread mutex unlock system bb set priority previous priority CHAPTER 3 HOW TO USE GNATFORLEON c 7 10 next next period int sporadic void int previous priority 0 while 1 1 pthread mutex lock previous priority system bb get priority amp sporadic task system bb set priority mutex priority pthread condition wait if mutex barrier false system bb sleepO mutex barrier false printf Hello sporadicXn pthread mutex unlock system bb set priority previous priority 5 int main void int count 0 system_bb_prio_t p_periodic system bb prio t p sporadic int stacksize 20480 system bb addr t stackaddress 0 400296 0 system bb addr t stackaddress2 stackaddress stacksize 600 system_bb_addr_t stackaddress3 stackaddress2 stacksize 600 system_bb_addr_t stackaddress stackaddress3 stacksize 600 adainit system_bb_initialize p_periodic 199 p_sporadic 200 mutex priority 200 mutex barrier false system bb thread create amp periodic task periodic 0 p periodic stackaddress stacksize system bb thread create amp sporadic task
21. simple examples a o os sr dr cer atm Be 3 7 4 Compiling a C program GNATforLEON ORK reference 4 1 Installation and directory structure 4 1 1 Getting GNATforLEON and ORK 112 Installing GNATforLEON 4 1 3 Installing the GNATforLEON 4 1 4 Directory structure Ad e di d ias oda ce We ad AAG Documentation s v A A A AA red gene 4 2 Were interlace 2 2 eem eu etus A SAA 4 2 1 1 4 2 3 Threads and synchronization 4 2 3 Time management o a A AL ae Bale 4 2 4 Interrupt handling a AA NG A A II T V qd di AD 6 4 4 Run time considerations 4 5 Tailoring the 4 5 1 Configurable parameters 27325 ey y ea rr Tes 4 5 3 Compiling the The Ravenscar profile Ail dec uo ata ma at wr a we dudes KA Soin Status ed A 2 1 Forbidden features A 2 2 Supported features A 2 3 Dynamic semantics uuo RS oe AA A 3 Denoting the restrictions 0 Na e a AA Extended Example program BA Des
22. us Other Optimizations and determinism rules ALRM D 12 7 11 Metrics The implementation shall document the following metric e The overhead associated with obtaining a mutual exclusive access to an entry less protected object This shall be measured in the following way For a protected object of the form protected Lock is procedure Set function Read return Boolean private Flag Boolean False end Lock protected body Lock is procedure Set is begin Flag True end Set function Read return Boolean Begin return Flag end Read end Lock The execution time in processor clock cycles of a call to Set This shall be measured between the point just before issuing the call and the point just after the call completes The function Read shall be called later to verify that Set was indeed called and mot optimized away The calling task shall have sufficiently high priority as to not be preempted during the measurement period 70 APPENDIX C METRICS The protected object shall have sufficiently high ceiling priority to allow the task to call Set The number of processor clock cycles used by a call to the protected procedure Set is 1214 C 1 5 Execution Time Clocks and Timers D 14 23 27 Metrics The implementation shall document the following metrics e An upper bound on the execution time duration of a clock tick This is a value D such that if t1 and t2 are any execution times o
23. your freedom to share and change free software to make sure the software is free for all its users This General Public License applies to most of the Free Software Foundation s software and to any other program whose authors commit to using it Some other Free Software Foundation software is covered by the GNU Library General Public License instead You can apply it to your programs too When we speak of free software we are referring to freedom not price Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software and charge for this service if you wish that you receive source code or can get it if you want it that you can change the software or use pieces of it in new free programs and that you know you can do these things To protect your rights we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights These restrictions translate to certain responsibilities for you if you distribute copies of the software or if you modify it For example if you distribute copies of such a program whether gratis or for a fee you must give the recipients all the rights that you have You must make sure that they too receive or can get the source code And you must show them these terms so they know their rights We protect your rights with two steps 1 copyright the software and 2 offer you this license which gives you legal permissio
24. 2 The SPARC architecture manual Version 8 Prentice Hall Inc Upper Saddle River NJ USA Stallman R M and Pessch R H 2007 Debugging with GDB Free Software Foundation 9th edition For GDB version 6 6 for GNAT GPL 2007 Urue a S Pulido J A Redondo J and Zamorano J 2007 Implement ing the new Ada 2005 real time features on a bare board kernel Ada Letters XXVII 2 61 66 Proceedings of the 13th International Real Time Ada Work shop IRTAW 2007 Wellings A 2001 10th International Real Time Ada Workshop Session sum mary Status and future of the Ravenscar profile Ada Letters XXI 1 Zamorano J Ruiz J F and de la Puente J A 2001 Implementing Ada Real Time Clock and absolute delays in real time kernels In Strohmeier A and Craeynest D editors Reliable Software Technologies Ada Europe 2001 number 2043 in LNCS pages 317 327 Springer Verlag
25. 2 Supported features The above restrictions still support a wide range of tasking features such as RP23 Task objects restricted as above RP24 Protected objects restricted as above RP25 Atomic and Volatile pragmas RP26 Delay until statements RP27 Ceiling Locking policy and FIFO_within_priorities dispatching RP28 Count attribute but not within entry barriers RP29 Task identifiers e g T Identity E Caller RP30 Synchronous task control RP31 Task discriminants RP32 Ada Real Time package RP33 Protected procedures as statically bound interrupt handlers RP34 Execution time clocks declared at library level RP35 A global fall back handler 50 APPENDIX A THE RAVENSCAR PROFILE A 2 3 Dynamic semantics Some aspects of the profile require their dynamic semantics to be defined RP36 If an entry call is made on an entry that already has a queued call i e the queue length would become 2 then Program Error is raised RP37 It is implementation defined what happens if a task attempts to terminate global fall back handler ISO IEC see 2007 C 7 3 can be set for the environment task The handler is called whenever a task attempts to terminate RP38 If a task executes a potentially blocking operation from within a protected object then Program Error must be raised A 3 Denoting the restrictions The run time profile Ravenscar can be enforced with the following pragma pragma Profile Ravenscar which is equivalen
26. ANTY for details type show w This is free software and you are welcome to redistribute it under certain conditions type show c for details The hypothetical commands show w and show c should show the appropri ate parts of the General Public License Of course the commands you use may be called something other than show w and show c they could even be mouse clicks or menu items whatever suits your program You should also get your employer if you work as a programmer or your school if any to sign a copyright disclaimer for the program if necessary Here is a sample alter the names Yoyodyne Inc hereby disclaims all copyright interest in the program Gnomovision which makes passes at compilers written by James Hacker signature of Ty Coon 1 April 1989 Ty Coon President of Vice This General Public License does not permit incorporating your program into proprietary programs If your program is a subroutine library you may consider it more useful to permit linking proprietary applications with the library If this is what you want to do use the GNU Library General Public License instead of this License 80 APPENDIX D GNU GENERAL PUBLIC LICENSE Bibliography Ada Core 2007 Using the GNAT Programming Studio Version 4 2 1 Ada Core 2008a GNAT GPL User s Guide Ada Core 2008b GNAT Reference Manual Asplund L Johnson B and Lundqvist K 1999 Session summary The Raven sc
27. Ada Ravenscar Profile in high integrity systems ISO IEC 2005 5 C Programming Language ISO IEC 1999 6 POSIX Standards ISO IEC 2003 6 CHAPTER 1 INTRODUCTION 1 9 2 Reference documents 1 LEON2 Manuals Gaisler Research 2005 2 GRMON User s Manual Gaisler Research 2007 3 Sparc 8 Architecture Manual SPARC International 1992 4 Ada 2005 Rationale Barnes 2008 5 Ada 95 Quality and Style Ausnit Hood et al 1995 6 GNAT Manuals Ada Core 2008a b 7 Debugging with GDB Stallman and Pessch 2007 Additional details and references can be found in the bibliography at the end of this volume 1 10 History ORK the first version of the Open Ravenscar real time Kernel was developed under ESA ESTEC Contract No 13863 99 NL MV in the period 1999 2000 with subse quent updates up to 2003 It was targeted to ECR32 computers based on a SPARC 7 architecture and was integrated with a custom crafted version of GNAT 3 13p In the period 2003 2005 a commercially supported version of the kernel was de veloped by and AdaCore under ESA ESTEC Contract No 17360 03 NL JA This version was integrated in the GNAT Pro for ERC32 product which is com mercialized by AdaCore The current version of the kernel now called ORK was developed in the frame work of the ASSERT project It is targeted to LEON computers and has been extended to support the current Ada 2005 standard see section 1 4 above ORK is t
28. ER 4 GNATFORLEON ORK REFERENCE After the cross compilation system is installed the directory desired location gnatforleon 2 1 elf bin bin must be added to the search path usually envi ronment variable PATH in your shell 4 1 3 Installing the GNATforLEON sources In the following the installation directory for source files is assumed to be usr local gnatforleon src although they can be installed at any other location as well After obtaining the gzipped tarfile gnatforleon 2 1 0 src tar gz which contains the sources of the GNATforLEON cross compilation system uncompress and untar it to usr local gnatforleon src The GNATforLEON distribution can be installed with the following commands assuming the gzipped tar file is in tmp gnatforleon 2 1 0 src tar gz cd usr local tar zxvf tmp gnatforleon 2 1 0 src tar gz The sources have been adapted using AdaCore patches LEON Bare C Cross Compilation System BCC patches and specific GNATforLEON patches These sources are ready to build GNATforLEON CCS The source distribution contains procedures Makefile for building the whole GNATforLEON CCS and the GNAT forLEON adalib see sections 4 5 and 4 5 3 4 1 4 Directory structure Contents of usr local gnatforleon bin executables include include files for the C interface info gcc documentation in info format lib gcc libraries which include GNATforLEON adalib for LEON target libexec gcc libraries man ma
29. MS 27 e ORK needs to be initialized before functions exported to C can be used This means that the function system bb initialize must be called after adainit e No dynamic memory can be used which means that no malloc calls can be made All variables must be declared statically and references must be used instead of pointers 3 7 3 simple example The example that follows is a C implementation of the Ada program from sec tion 3 2 3 If a POSIX interface were used the start event of the sporadic task would be implemented by means of a condition variable corresponding to the pro tected entry in the Ada version However ORK does not support POSIX like con dition variables but a lower level synchronization mechanism unconditional sleep and wakeup is provided instead The example shows how to use this mechanism to implement sporadic activation according to the Ravenscar Computational Model The expected output is the same as in section 3 4 Listing 3 8 Hello program in C include gnatforleon h System bb thread t periodic task system bb thread t sporadic task volatile system bb mutex t mutex int periodic void 4 int c 3 int previous_priority 0 system_bb_time_t ticks_ps system_bb_ticks_per_second system_bb_time_t period 0 5 ticks_ps 500ms system_bb_time_t next system_bb_clock while 1 1 system bb delay until next printf Hello if 0
30. Potentially blocking operations Pragma Profile Ravenscar includes the pragma Detect Blocking Therefore the ex ception Program Error will be raised whenever this kind of bounded error is detected Potentially blocking operations are ALRM 9 5 1 e Protected entry calls e delay until e Ada Synchronous Task Control Suspend Until True ALRM D 10 An external call on a protected subprogram with the same target object as that of the protected action or a call on a subprogram whose body contains a potentially blocking operation is also a blocking operation ALRM 9 5 1 4 5 TAILORING THE KERNEL 45 4 5 Tailoring the kernel ORK can be tailored to different applications by means of configuration parame ters Paarmeters are declared in System BB Parameters file s bb para ads This file as well as other ORK files can be found in the gcc 4 1 3 gcc ada directory You can modify this file and rebuild the whole cross compilation system in order to build GNATforLEON kernel that satisfies your requirements It is recommended that the file s bbx para ads be previously compiled with the same flags which will be later used to compile the whole run time library sparc elf gcc c gnatpg s bb para ads After updating s bbpara ads the GNATforLEON cross compilation system can be rebuilt from the sources see section 4 5 3 4 5 1 Configurable parameters The configurable parameters included in the System BB Parameters package are
31. T port of the host This can be overridden by specifying an alternative device Device names depend on the host operating system On Unix systems serial devices are named as dev ttyXX Use the baud option if you need to use a different baud rate for the DSU serial link than the default 115200 baud The example below shows how to execute programs with GRMON using an usual list of start up switches grmon dsu uart dev ttySO baud 115200 Once you get the GRMON console use the 1oad command to download the application and then go to start it The output from the application appears on the normal LEON UARTs and thus cannot be seen on the GRMON console unless the program is started with the u switch You can use terminal emulators such as tip minicom or kermit to display the output Warning 3 2 When an application terminates it must be reloaded on the target before it can be re executed in order to re initialise the data segment data For a complete description of the GRMON debug monitor see the GRMON User s Manual Gaisler Research 2007 3 5 1 Floating point considerations If the targeted LEON processor has no floating point hardware then all applications must be compiled and linked with the msoft float option in order to enable floating point emulation When running the program on the TSIM simulator the simulator should be started with the nfp option no floating point in order to disable the FPU 5GRMON is no
32. Unit European Space Agency European Space Research and Technology Center Floating Point Unit Free Software Foundation Z E J Debugger NU New York University Ada Translator NU Ada Run Time Library NU Ada Run Time Library Interface NAT No Run Time Z U is Not Unix Z U Low Level Library NU Low Level Library Interface ep an O GA A 022 O X NU Public License 1 9 REFERENCES 5 GPS GUI HIS IRTAW ISO LGPL ORK OS PC PROM GNAT Programming Studio Graphic User Interface High Integrity System International Real Time Ada Workshop International Standards Organization Lesser GNU Public License formerly Library GPL Open Real Time Ravenscar Kernel Operating System IBM Personal Computer architecture Programmable Read Only Memory RAVENSCAR Reliable Ada Verifiable Executive Needed for Scheduling Critical RP RP program RTOS UPM URL Applications in Real Time Ravenscar Profile An Ada program that complies with the Ravenscar profile Real Time Operating System Universidad Polit cnica de Madrid Technical University of Madrid Uniform Resource Locator 1 9 References 1 9 1 Applicable documents 1 ECCS E40B Space Engineering Software ECSS 2003 2 Ada Reference Manual ISO IEC 2007 3 Guidance for the Use of the Ada Programming Language in High Integrity Systems ISO IEC 2000 4 Guide for the use of the
33. ackage empty interface e System BB Threads Thread management including synchronization and schedul ing control functions e System BB Threads Queues Different kernel queues such as alarm queue and ready queue e System BB Time Clock and delay services including support for timing events e System BB Time Execution Time Support Execution time clocks and timers as well as group budgets support e System BB Interrupts Interrupt handling e System BB Parameters Configuration parameters e System BB CPU Primitives Processor dependent definitions and operations e System BB Peripherals Support for peripherals in the target board e System BB Peripherals Registers Definitions related to input output registers of the peripheral devices e System BB Serial Output Support for serial output to a console The kernel is not intended to be directly used from Ada programs Instead an interface to the GNU Ada Runtime Library GNARL is used so that Ada tasking constructs can be directly used by the real time application programmer This interface is described in the next section 1 stands for bare board kernel 2 24 ARCHITECTURE OF ORK
34. and GCC programming environments Ada Core 2008a the GDB debugger Stall man and Pessch 2007 and the fundamentals of real time programming and the Ravenscar profile ISO IEC 2005 1 2 Purpose The purpose of this document is to describe how to use install and configure GNATforLEON for LEON2 based computers GNATforLEON is an integrated package combining an instance of the GNAT compiler for the SPARC v8 architecture with ORK an open source real time kernel of reduced size and complexity for which users can seek certification for mission critical space applications The kernel supports both Ada 2005 and C applications on a LEON2 based computer GNATforLEON is fully integrated with other GN AT based tools and with GDB the GNU debugger 1 3 Applicability statement This manual applies to the following versions of software e GNATforLEON 2 1 0 ORK 2 1 0 e GNAT GPL 2008 e GCC 4 1 3 GDB 6 3 2 CHAPTER 1 INTRODUCTION 1 4 Compliance to standards ORK supports the tasking model defined in the Ada 2005 standard ISO IEC 8652 1995 Amd 1 2007 including appendices C and D except for the following 1 The tasking model is restricted as specified by the Ravenscar profile Ada Reference Manual D13 1 Consequently e Pragma Priority Specific Dispatching is not supported e Only the FIFO Within Priorities dispatching policy with the Ceiling Locking policy is supported 2 The following exceptions to the Ravenscar prof
35. ar profile and implementation issues Ada Letters XIX 25 12 14 Proceedings of the 9th International Real Time Ada Workshop ATMEL 2005 32 bit SPARC V8 Proccesor AT697E DataSheet Ausnit Hood C Johnson K A IV R G P and Opdahl S B editors 1995 Ada 95 Quality and Style Number 1344 in Lecture Notes in Computer Science Springer Verlag Baker T and Vardanega T 1997 Session summary Tasking profiles Ada Letters XVI1 5 5 7 Proceedings of the 8th International Ada Real Time Work shop Barnes J 2008 Ada 2005 Rationale Number 5020 in Lecture Notes in Computer Science Springer Verlag Burns A 1994 Preemptive priority based scheduling An appropriate engineering approach In Son S H editor Advances in Real Time Systems Prentice Hall Burns A and Brosgol B 2002 Session summary Future of the Ada language and language changes such as the Ravenscar profile Ada Letters XXII 4 Proceedings of the 11th International Real Time Ada Workshop Burns A Dobbing B and Romanski G 1998 The Ravenscar tasking profile for high integrity real time programs In Asplund L editor Reliable Software Technologies Ada Europe 98 number 1411 in LNCS pages 263 275 Springer Verlag Burns A and Wellings A J 1997 Restricted tasking models In Proceedings of the 8th International Ada Real Time Workshop pages 27 32 Ada Letters Burns and Wellings A J 2001 Real Time Sys
36. as validated by Jes s Borruel and Juan Carlos Morcuende from Construcciones Aeron uticas CASA Space Division We also relied very much on Andy Wellings and Alan Burns of the University of York UK for reviewing and discussions about the Ravenscar profile and its implementation ORK was developed under contract with ESA Jorge Amador Tullio Vardanega and Jean Loup Terraillon provided many positive criticism and contributed the user s view during the development The project was carried out from September 1999 to June 2000 1 11 2 Contributors to ORK ORK the real time kernel used in GNATforLEON was developed by a team of the Department of Telematics Engineering Universidad Polit cnica de Madrid DIT UPM lead by Juan Antonio de la Puente The other members of the team were Juan Zamorano Jos Pulido Santiago Urue a Jorge L pez and Jos Redondo The same team worked in collaboration with AdaCore to port GNAT to LEON2 and to develop the adapted runtime packages that enable to work with ORK GNATforLEON was developed in the framework of the ASSERT and THREAD projects It is based on AdaCore GNAT Pro ERC32 product which in turn was based on ORK 1 12 Document overview The rest of this document is organised as follows e Chapter 2 describes the general structure of the GNATforLEON software and the Ravenscar profile restrictions e Chapter 3 contains instructions for writing compiling linking executing and de
37. at you saw do not assume that we can guess what you saw or duplicate the behaviour you encountered All sources must be sent in plain ASCII or ISO 8859 1 format e Please include a complete identification of the version of the system you are running i e development and target environments as well as versions of GNATforLEON and all other software you are using e Please try to reduce your example to a simple one If you think that you have found a bug in GNAT GCC or GDB rather than GNATforLEON or the ORK4 kernel please send the bug report to the appropriate address e GNAT report gnat com e GCC bug gcc gnu org e GDB bug gdb gnu org 4 CHAPTER 1 INTRODUCTION 1 8 Glossary 1 8 1 Definitions Development platform The computer system hardware and software which is used to write compile and debug embedded software Execution platform The computer hardware and possibly basic ROM resident software such as a bootstrap loader where the embedded software is executed Target platform The same as the execution platform RP program A program that complies with the Ravenscar profile restrictions 1 8 2 Acronyms ALRM API ATCB BCC CCS CIL DSU ESA ESTEC FPU FSF GDB GNAT GNARL GNARLI GNORT GNU GNULL GNULLI GPL Ada Language Reference Manual Application Program Interface Ada Task Control Block Bare C Cross Compilation System Cross Compilation System C Interface Library Debug Support
38. ate GDB communica tions start the monitor with the gdb switch grmon dsu uart dev ttyS0 baud 115200 gdb Now the debugging session can be started using the extended remote protocol By default GRMON listens on port 2222 for the GDB connection sparc elf gdb hello gdb target extended remote localhost 2222 gdb load gdb continue While attached normal GRMON commands can be executed using the gdb monitor command Output from the GRMON commands such as the trace buffer history is then displayed on the GDB console 3 6 Interrupt handlers 3 6 1 Protected procedure handlers The Ravenscar profile allows the use of protected procedures as interrupt handlers Interrupt handlers are declared as parameterless protected procedures attached to 3 7 WORKING WITH C PROGRAMS 25 an interrupt source Interrupt sources are identified in the Ada Interrupts Names package This package contains the identifiers of all the LEON interrupts A general template is shown in listing 3 5 Listing 3 5 Template for interrupt handlers with Ada Interrupt Names use Ada Interrupt Names used for External Interrupt 0 External Interrupt O Priority protected Interrupt is public protected operations private the handler need not be visible outside the protected object pragma Interrupt Priority External Interrupt O Priority procedure Handler pragma Attach Handler Handler External Interrupt O
39. bugging programs with the GNATforLEON software e Chapter 4 describes in detail the functions of GNATforLEON and the way it is linked with Ada and C programs e Appendix A describes the Ravenscar profile in detail e Appendix B contains a comprehensive example of a Ravenscar compliant pro gram and its compilation with GNATforLEON e Appendix D contains a copy of the GNU General Public License GPL Currently integrated into EADS Astrium CHAPTER 1 INTRODUCTION Chapter 2 Software overview 2 1 The ORK kernel ORK Open Ravenscar Real Time Kernel is a small high performance real time kernel that provides restricted tasking support for Ada programs The kernel is also usable from C programs The kernel is intended to support mission critical real time software systems In order to ensure that the software is highly reliable that if required may even be subject to a certification process program constructs which are not verifiable should not be used The exact set of language features to be avoided depends on the degree of integrity that is desired for the software and the verification methods that are to be used A detailed account of the Ada language issues in high integrity systems can be found in the ISO technical report Guide for the use of the Ada Programming Language in High Integrity Systems ISO IEC 2000 Based on these considera tions language subsets for building software with different levels of integrity ca
40. ce you may not distribute the Program at all For example if a patent license would not permit royalty free redistribution of the Program by all those who receive copies directly or indirectly through you then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program If any portion of this section is held invalid or unenforceable under any par ticular circumstance the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances 10 11 TT It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims this section has the sole purpose of protecting the integrity of the free software distribution system which is implemented by public license practices Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system it is up to the author donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License If the distribution and or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces the original copyright holder who pla
41. ces the Program under this License may add an explicit geographical distribution limitation excluding those countries so that distribution is per mitted only in or among countries not thus excluded In such case this License incorporates the limitation as if written in the body of this License The Free Software Foundation may publish revised and or new versions of the General Public License from time to time Such new versions will be similar in spirit to the present version but may differ in detail to address new problems or concerns Each version is given a distinguishing version number If the Program specifies a version number of this License which applies to it and any later version you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation If the Program does not specify a version number of this License you may choose any version ever published by the Free Software Foundation If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different write to the author to ask for permission For software which is copyrighted by the Free Software Foundation write to the Free Software Foundation we sometimes make exceptions for this Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software ge
42. code including two tasks a protected object and a background procedure files tasking ads and tasking adb Notice that GNAT requires that each compilation unit is in a separate file with the same name as the unit see the GNAT User s Guide Ada Core 2008a for the details Figure 3 2 shows the task structure of the program The main procedure code is provided in listing 3 2 Listing 3 2 Main procedure of the hello program hello adb Main procedure for the hello example with Tasking used for Background procedure Hello is pragma Priority 0 begin do some background work must not terminate Tasking Background end Hello Notice that the main procedure does nothing but start a background procedure The Priority pragma specifies the lowest possible priority for the environment task i e the initial task that does all initialization and then calls the main procedure In this way we ensure that the background procedure is only executed when there are no other executable tasks The environment task is not allowed to terminate in GNAT when the pragma Profile Ravenscar is in place In order to prevent this to happen the background 3 2 WRITING ADA PROGRAMS 19 procedure must never return This is checked at compile time by writing a No_Return pragma near the procedure specification in file tasking ads see listing 3 3 Listing 3 3 Specification of the Tasking package tasking ads applicati
43. cription ipe On A 8 B 2 Temporal requirements of the tasks B 3 Schedulability analysis 4 Example program amp Bo Example todos iu u dad ee 31 31 31 31 32 32 33 34 34 34 34 40 42 44 44 45 45 45 46 AT 47 48 48 49 50 50 51 C Metrics C 1 Ada LRM Annex C and D Metrics C 1 1 Protected Procedure Handlers C 1 2 Monotonic Time Delay as dct d C 1 4 Other Optimizations and determinism rules C 1 5 Execution Time Clocks and Timers eub mins BYOBUSU acum Ere tnt AU C 2 Other useful metrics C 2 1 Context Switch Cod Interr pt D GNU General Public License Bibliography 111 65 65 65 66 68 69 70 70 1 ral 71 73 81 lv Chapter 1 Introduction 1 1 Intended readership This manual contains instructions for the use of the Open Ravenscar real time Kernel ORK and the GNATforLEON compilation toolchain with the LEON2 computer It should be read by application programmers and system administrators of software projects using ORK and GNATforLEON Prior knowledge of the Ada ISO IEC 2007 and C ISO IEC 1999 program ming languages is assumed The reader should also be familiar with the GNAT
44. ct No 13863 99 NL MV Status Final Authors Juan A de la Puente Juan Zamorano Jorge L pez The original Operation Manual for ORK was written by Juan A de la Puente Juan Zamorano Jos F Ruiz Ram n Fern ndez Marina and Miguel Angel Ajo History Version Date Comments 1 0 2007 07 18 First public release 1 1 2008 11 18 Revised version for GNATforLEON 2 0 1 1 2 2009 03 30 Revised version with some fixes 1 3 2009 07 30 New version for GNATforLEON 2 1 0 Contents 1 Introduction 1 1 1 Intended readership o Meca ias ARRE AA 1 E A E EN 1 1 3 Applicability statement o uou vow PA wa ERI a eS 1 14 Compliance to standards 2 Ts Free software mta eiu ep Qr qun due 2 20 qu eMe 2 1 6 Related documents 3 1 7 Problem reporting instructions dnd ee ee 3 1582 dort aX te a D de Ba KANG NG 4 LET Definitions ed dI ee uy ee uui us uen 4 115 2 A ped e 4 LO References di eo eat 5 1 9 1 Applicable documents 5 1 9 2 Reference documents 6 CAOS 5 o a BO eae a As 6 ILI C OntbULOLSs lr Bis ke Dt I eR D NG ESCAS 6 1 11 1 Contributors to 6 1 11 2 Contributors to 1 12 Document overview gt
45. ct priorities for threads and interrupt handlers otherwise tasks could delay the interrupt handling The implication of this correct and important recommen dation is that the user should not assign priorities in the Interrupt Priority range to software tasks 4 3 Errors Errors in the kernel are signalled to the application program by means of the Ada exception mechanism 4 4 Run time considerations Storage allocation Dynamic storage should only be allocated from a preallocated pool during the initialization of the kernel as a result of task creation ATCBs stacks If the preallocated pool is completely full any request for new space raises Tasking Error Interrupt priorities When attaching protected procedures to interrupts the ceiling priority of the pro tected object should be carefully chosen The compiler checks that the ceiling prior ity of the protected object is in the range of System Interrupt Priority This range of priorities is mapped to the 15 distinct interrupt levels provided by the SPARC architecture Therefore when assigning priorities to protected objects which con tains protected procedure handlers the priority value must be at least equal to the priority of the hardware interrupt Otherwise the execution of the program is er roneous ALRM C 3 1 The kernel cannot automatically detect this wrong priority assignment and therefore care must be taken by the user not to incur this kind of error
46. de enough information on the behaviour of the program You can have a better view of the program execution by using the GDB debugger connected to the TSIM LEON simulator In this case TSIM must be started with the gdb option so that it waits for a connection from GDB tsim gdb gdb interface using port 1234 After that GDB can be started in the usual way for instance in another win dow Before loading the program to debug GDB must be connected to the simu lator using the extended remote target sparc elf gdb hello gdb target extended remote 127 0 0 1 1234 gdb load gdb cont gdb detach 5TSIM is not free software and it is not part of GNATforLEON See http www gaisler com for futher details 3 5 EXECUTING PROGRAMS ON THE TARGET PLATFORM 23 For a complete description of GDB commands see the document Debugging with GDB Stallman and Pessch 2007 You can have a better view with the graphical source level front end to GDB of the GNAT Programming Studio GPS 3 5 Executing and debugging Ada programs on the target platform The simplest way you can test your program on the target platform is by using the GRMON debug monitor for LEON processors GRMON comunicates with the LEON debug support unit DSU and enables non intrusive debugging of the complete target system It is started by entering the grmon command in a terminal window By default GRMON communicates with the target using the first UAR
47. evelopment In order to develop programs based on GNATforLEON ORK you should perform the following activities 1 Write the source code for the program 2 Compile and link the program 3 Debug the program on the development platform 4 Debug the program on the target platform Two kinds of programs are supported by GNATforLEON and e Ada programs restricted as defined by the Ravenscar profile e C programs directly using kernel threads Figure 3 1 describes the data flow for the GNATforLEON compilation system Notice that purely sequential Ada or C programs do not require ORK support and can be compiled using a bare board version of GNAT or GCC 3 2 Writing Ada programs The first step in compiling an Ada application is to write the source code for the program units that make up the application You can use your favourite text editor for this purpose or use an IDE such as GPS the GNAT Programming Studio 3 2 1 Ravenscar profile restrictions When writing your Ada application code you should bear in mind that only the Ada subset defined by the Ravenscar profile can be used This means that you should not use any of the following features see appendix A for a full description of the Ravenscar profile For details about the different version of contact Ada Core at http www adacore com 15 16 files executable GNAT b xxx ads GNAT GNAT ali binder linker AY configuration fi b xxx adb
48. f a given task such that tl lt 2 and Clock Clock then 12 11 lt D The maximum value of a clock tick is 1 x P processor cycles where P is the setting of the prescaler register 4 for the current default ORK4 configura tion An upper bound on the size of a clock jump A clock jump is the difference between two successive distinct values of an execution time clock as observed by calling the Clock function with the same Task 1 The maximum value of a clock jump is 110 x P processor cycles where P is the setting of the prescaler register 4 for the current default ORK4 configuration An upper bound on the execution time of a call to the Clock function in pro cessor clock cycles The execution time of a call to the Clock function is 439 clock cycles Upper bounds on the execution times of the operators of the type CPU Time in processor clock cycles The results of the test give the following values Operator Cycles CPU Time Time Span 58 Time Span CPU Time 58 CPU Time Time Span 58 CPU Time CPU Time 58 CPU Time CPU Time 65 CPU Time lt CPU Time 77 CPU_Time gt CPU_Time 73 CPU_Time gt CPU_Time 61 Split CPU_Time Seconds Count Time_Span 1142 Time_Of Seconds_Count Time_Span 80 C 1 6 Timing Events D 15 23 24 Metrics The implementation shall document the following metric C 2 OTHER USEFUL METRICS 1 e An upper bound on the lateness of the execution of a handler That
49. fter translation is included without limitation in the term modification Each licensee is addressed as you Activities other than copying distribution and modification are not covered by this License they are outside its scope The act of running the Program is not restricted and the output from the Program is covered only if its contents constitute a work based on the Program independent of having been made by running the Program Whether that is true depends on what the Program does 1 You may copy and distribute verbatim copies of the Program s source code as you receive it in any medium provided that you conspicuously and appro priately publish on each copy an appropriate copyright notice and disclaimer of warranty keep intact all the notices that refer to this License and to the absence of any warranty and give any other recipients of the Program a copy of this License along with the Program You may charge a fee for the physical act of transferring a copy and you may at your option offer warranty protection in exchange for a fee 2 You may modify your copy or copies of the Program or any portion of it thus forming a work based on the Program and copy and distribute such modifications or work under the terms of Section 1 above provided that you also meet all of these conditions a You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change b You mu
50. g Alarm variable procedure Turn True Pending Alarm Turns Pending Alarm variable to true procedure Cancel Alarm Cancel any alarm set in hardware until next clock timer expires procedure Inmediate Alarm Now in out System BB Time Time end System BB T ime Time is represented in the ORK4 kernel as a 64 bit integer number of ticks A tick is a real time interval during which the clock value as observed by calling the System BB Clock function remains constant The kernel provides a high resolution clock with a low overhead for timer han dling the combination of a timestamp counter and a high resolution timer con tributes to improve the performance and granularity of the time management The LEON2 hardware provides two timers apart from the special Watchdog timer which can be programmed to be either of single shot type or periodic type ATMEL 2005 We use one of them the Real Time Clock as a timestamp counter and the other called General Purpose Timer as a high resolution timer Therefore the first one provides the basis for a high resolution clock while the second offers the required support for precise alarm handling The Real Time Clock is programmed by ORK to interrupt periodically by updating the most significant part of the clock register The less significant part of 42 CHAPTER 4 GNATFORLEON ORK REFERENCE the clock is held in the hardware clock register A software register is used to store the
51. g GNATforLEON and ORK GNATforLEON ORK 4 is distributed via http www dit upm es ork The sources used to build the GNATforLEON cross compilation system can be also found at the same location The GNATforLEON distribution includes gnatforleon 2 1 0 1686 pc linux gnu bin tar gz gzipped tarfile which con tains the binary distribution for GNU Linux The current distribution has been built on Ubuntu 6 0 6 using glibc2 libraries However it runs on most modern Linux distributions In order to avoid problems with different versions of libc all binaries are statically linked gnatforleon 2 1 0 src tar gz gzipped tarfile which contains the sources as well as the procedures for building the GNATforLEON examples 2 1 0 tgz gzipped tarfile which contains some examples of the GNAT forLEON functionality The Ada and C version of the example described in section 3 2 3 as well as the demo application described in appendix B are also included 4 1 2 Installing GNATforLEON The GNAT directory tree has been compiled to reside in any directory After ob taining the gzipped tarfile gnatforleon 2 1 0 i686 pc linux gnu bin tar gz which includes the binary distribution uncompress and untar it in the desired loca tion The GNATforLEON distribution can be installed with the following commands assuming the gzipped tar file is in directory tmp tar zxvf gnatforleon 2 1 0 i686 pc linux gnu bin tar gz C NN desired location 3l 32 CHAPT
52. ger type Thread Descriptor is record Context aliased System BB CPU Primitives Context Buffer Location where the hardware registers stack pointer program counter are stored This field supports context switches among threads ATCB System Address Address of the Ada Task Control Block corresponding to the Ada task that executes on this thread Base Priority System Any Priority Base priority of the thread Active Priority System Any Priority pragma Volatile Active Priority Active priority that differs from the base priority due to dynamic 36 CHAPTER 4 GNATFORLEON ORK REFERENCE priority changes required by the Ceiling Priority Protocol This field is marked as Volatile for a fast implementation of Get Priority Top Of Stack System Address Address of the top of the stack that is used by the thread Bottom Of Stack System Address Address of the bottom of the stack that is used by the thread Next Thread ld Points to the ready thread that is in the next position for execution Alarm Time System BB Time Time Time absolute when the alarm for this thread expires Next Alarm Thread ld Next thread in the alarm queue The queue is ordered by expiration times The first place is occupied by the thread which must be first awaken State Thread States Encodes some basic information about the state of a thread Wa
53. h are due to 1 Kernel overhead 2 The code of the tasks includes calls to the Whetstone benchmark with an actual parameter which suits the WCET defined in table B 2 As a result the execution time of protected operations delay settings clock readings and other operations increases the WCET defined in table B 2 B 5 Example code Listing B 1 Demo main procedure with Tasks with System procedure Demo is pragma Priority System PriorityFirst begin Tasks Background end Demo Listing B 2 Tasks spec ification package Tasks is procedure Background end Tasks 58 APPENDIX B EXAMPLE PROGRAM Listing B 3 Tasks body with Kernel Peripherals with System lO with Ada Interrupts Names with Ada Real Time use type Ada Real Time Time Span with System with Workload with Force External Interrupt 2 package body Tasks is Time Unit constant Ada Real Time Time Span Ada Real Time Milliseconds 100 This constant was meausured with tsim freq 41 A program for measuring this constant can be built with make f Makefile measure Time per Kwhetstones constant Ada Real Time Time Span Ada Real_Time Nanoseconds 170 540 tsim leon O2 procedure Execution Time Time Ada Real Time Time Span is begin Workload Small Whetstone Time Time per Kwhetstones end Execution Time 500 Milliseconds is the ini
54. he public the best way to achieve this is to make it free software which everyone can redistribute and change under these terms To do so attach the following notices to the program It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty and each file should have at least the copyright line and a pointer to where the full notice is found one line to give the program s name and an idea of what it does Copyright yyyy name of author This program is free software you can redistribute it and or modify it under the terms of the GNU General Public License as published by the Free Software Foundation either version 2 of the License or at your option any later version This program is distributed in the hope that it will be useful but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE See the GNU General Public License for more details You should have received a copy of the GNU General Public License along with this program if not write to the Free Software Foundation Inc 59 Temple Place Suite 330 Boston MA 02111 1307 USA Also add information on how to contact you by electronic and paper mail If the program is interactive make it output a short notice like this when it starts in an interactive mode Gnomovision version 69 Copyright C year name of author Gnomovision comes with ABSOLUTELY NO WARR
55. he real time kernel used in the ASSERT Virtual Machine a specialized run time platform that guarantees the specified real time behaviour of Ravenscar programs 1 11 Contributors 1 11 1 Contributors to ORK ORK was developed by a team of the Department of Telematics Engineering Uni versidad Polit cnica de Madrid DIT UPM led by Juan Antonio de la Puente The other members of the team were Juan Zamorano Jos F Ruiz Ram n Fern ndez and Rodrigo Garc a Alejandro Alonso and ngel lvarez acted as document and code reviewers and contributed to the technical discussions with many fruitful com ments and suggestions The same team developed the adapted packages that enable GNAT to work with ORK Universidad Polit cnica de Madrid Technical University of Madrid 2ASSERT Automated proof based System and Software Engineering for Real Time systems is an Integrated Project partially funded by the European Commission within the Information Society Technologies priority of the 6th Framework Programme in the area embedded systems UPM s work in the project was also supported by the Spanish National R amp D Plan 1 12 DOCUMENT OVERVIEW 7 GDB was adapted to ORK by Jes s Gonz lez Barahona Vicente Matell n Andr s Arias and Juan Manuel Dodero Jos Centeno and Pedro de las Heras acted as reviewers for this part of the work All of them work at the Department of Engineering Universidad Rey Juan Carlos Madrid The ORK software w
56. he task end record for Thread Descriptor use record Context at 0 range 0 System BB CPU Primitives Context Buffer Size 1 end record It is important that the Context field is placed at the beginning of the record because this assumption is using for implementing context switching procedure Initialize Environment Thread Thread Id Main Priority System Any Priority Procedure to initialize the board and the data structures related to the low level tasking system This procedure must be called before any other tasking operation procedure Thread Create Id Thread 14 Code System Address Arg System Address Priority System Any Priority Stack_Address System Address Stack_Size System Parameters Size Type pragma Export C Thread Create system bb thread create Create a new thread The new thread executes the code at address Code and using Args as argument Priority is the base priority of the new thread The new thread is provided with a stack of size Stack Size that has been preallocated at Stack Address A procedure to destroy threads is not available because that is not allowed by the Ravenscar profile function Thread Self return Thread 14 pragma Inline Thread Self 38 CHAPTER 4 GNATFORLEON ORK REFERENCE pragma Export C Thread_Self system_bb_thread_self Return the thread identifier
57. his clause real time is defined to be the International Atomic Time TAI The implementation shall document the following metrics e An upper bound on the real time duration of a clock tick This is a value D such that if t1 and t2 are any real times such that t1 lt t2 and Clock Clock a then t2 t1 D The tick of the clock is equal to the period of the processor input signal and the clock is incremented by the hardware every tick As a result the tick has always the same value e An upper bound on the size of a clock jump The clock is a count of ticks and is not synchronized with external sources As a result the clock does not jump e An upper bound on the drift rate of Clock with respect to real time This is a real number D such that E 1 D lt Clock E Clock lt E 1 D provided that Clock E 1 D lt Time Last This test is yet to be performed on the GR XC35 1500 or GR CPCI AT697 boards e where Clock is the value of Clock at time t and E is a real time duration not less than 24 hours The value of E used for this metric shall be reported To be completed when the previous test is performed e An upper bound on the execution time of a call to the Clock function in pro cessor clock cycles The following source code line was tested T Clock The measured value is D8 44 clock _call total processor cycles used by a Clock cal
58. ignal once every 10s end if Cycle Cycle 1 Next Next Period end loop end Periodic task body Sporadic is Cycle Cycle_Count begin loop Event Wait Cycle Put Line Hello sporadic end loop end Sporadic protected body Event is procedure Signal C Cycle Count is begin Occurred True Cycle i end Signal 3 83 COMPILING AND LINKING ADA PROGRAMS 21 entry Wait C out Cycle_Count when Occurred is begin Occurred False C Cycle end Wait end Event end Tasking Notice that the background procedure actually does nothing but increment a count in an endless loop In real applications it might include some useful work to be executed at the lowest priority The Tasking package contains two tasks a periodic task and a sporadic task The latter is activated by the periodic task by means of a synchronization protected object Event This is a common way to implement software activated sporadic tasks Burns and Wellings 2001 The periodic task activates the sporadic task once every ten cycles Each task writes a string to the serial output every time it is activated There is a copy of the above files in the examples hello distribution directory In order to compile and link the example files you should copy them to a working directory and follow the steps that are described in the next section 3 3 Compiling and linking Ada programs You can compile and link your program with g
59. ile are supported e At most one statically declared execution time timer per task is allowed e Statically declared group budgets are allowed The ORK C interface provides a simplified thread interface which implements the Ravenscar computational model RCM It is not compliant with the POSIX 1 standard IEEE Std1003 1 2004 Edition but the provided functionality is similar to the POSIX subset needed to implement the RCM 1 5 Free software GNATforLEON ORK is free software This means that everyone is free to use it and free to redistribute it on a free basis This applies to the source code and documentation as well GNATforLEON ORK 4 is not in the public domain It is copyrighted and there are restrictions on its distribution but these restrictions are designed to permit everything that a good cooperating citizen would want to do What is not allowed is to try to prevent others from further sharing any version of GNATforLEON or ORK that they might get from you The precise conditions are found in the GNU General Public Licence GPL that comes with GNATforLEON and ORK See appendix D for details The easiest way to get a copy of GNATforLEON ORK4 is from someone else who has it The GPL gives you the freedom to copy or adapt a licensed program but every person getting a copy also gets with it the freedom to modify that copy which means that they must get to source code and the freedom to distribute further copies You can als
60. is the maz imum time between when a handler is actually executed and the time specified when the event was set The measured value for this metric is 4756 processor clock cycles C 2 Other useful metrics C 2 1 Context Switch The context switch time is measured between two tasks with the same priority The worst case measured value is 1027 processor clock cycles C 2 2 Interrupt Latency This tests measures the interrupt latency This test uses a special register of LEON2 which permits interrupts to be enforced The external interrupt 2 is forced by this means and the time until the first statement of the protected interrupt handler is reached can be considered as the interrupt latency The measured value of interrupt latency is 1747 processor clock cycles This elapsed time has been measured with the TSIM simulator Otherwise spe cial test instrument should be used The example program detailed in appendix B has been used for the test 72 APPENDIX C METRICS Appendix D GNU General Public License Version 2 June 1991 Copyright c 1989 1991 Free Software Foundation Inc 59 Temple Place Suite 330 Boston MA 02111 1307 USA Everyone is permitted to copy and distribute verbatim copies of this license docu ment but changing it is not allowed Preamble The licenses for most software are designed to take away your freedom to share and change it By contrast the GNU General Public License is intended to guarantee
61. isters to get definitions of MEC registers such as Test_Control Interrupt Mask Interrupt_Force procedure Force External Interrupt 2 is package SPR renames System BB Peripherals Registers The MEC registers must be accesses as a whole The workaround used to force GNAT to generate proper instructions is Registers type definition are cualified with pragma Atomic and auxiliary objects are used to write the MEC registers Interrupt Mask Auxiliary SPR Interrupt Mask Register SPR Interrupt Mask Interrupt Force Auxiliary SPR Interrupt Register SPR Interrupt Force B 5 EXAMPLE CODE 63 Interrupt Clear Auxiliary SPR Interrupt Register SPR Interrupt Clear begin Interrupt Clear Auxiliary External Interrupt 2 True Interrupt Mask Auxiliary External Interrupt 2 True Interrupt Force Auxiliary External Interrupt 2 True SPR Interrupt Clear Interrupt Clear Auxiliary SPR Interrupt Mask Interrupt Mask Auxiliary SPR Interrupt Force Interrupt Force Auxiliary end Force External Interrupt 2 Listing B 5 Configuration file gnat adc minimum configuration file template for the Ravenscar profile pragma Profile Ravenscar Any other configuration pragma can be included here 64 APPENDIX B EXAMPLE PROGRAM Appendix C Metrics C 1 Ada LRM Annex C and D Metrics This appendix lists the additional characteristics of
62. keup Signaled Boolean Variable which reflects whether another thread has performed a Wakeup operation on the thread Time Init Execution System BB Time Time Time when task has received the CPU Execution Time System BB T ime Time Execution Time of the task Time Remaining System BB T ime Time Time remaining of timer associated to the task Is Timer Alarm Boolean Flag that indicates if it has been put an alarm associated to the timer associated to the task Is GB Alarm Boolean Flag that indicates if it has been put an alarm associated to the timer associated to the group of the task Integer Integer Index to the array with the handlers associated to the timers Time Diff System BB Time Time Difference of time between time of the init of the execution of the task and the asignation of the timer to the task Time Diff GB System BB Time Time Difference of time between time of the init of the execution of the 42 KERNEL INTERFACE 37 task and the asignation of the timer to the group of the task Handler Exec Handler Handler associated to the Execution Time Timer of the task GB Id Integer Identifier associated to the Group Budget of the task GB Index Integer Place of the array associated to the Group Budget where the task data is stored Handler GB Exec Handler Handler associated to the Group Budget of t
63. l 2002 and IRTAW 12 Dobbing and de la Puente 2003 It is included in the ISO report Guide for the use of the Ada Programming Language in High Integrity Systems HIS ISO IEC 2000 and in the current Ada standard ISO IEC 2007 The summary presented here is based on the G uide for the use of the Ada Ravenscar Profile in High Integrity Systems ISO IEC 2005 with a few changes to adapt it to the Ada 2005 standard The definition of the Ravenscar profile is based on Ada including the Systems Programming and Real Time annexes ISO IEC 2007 annexes C amp D It only addresses tasking constructs as the reliability aspects of the sequential part of Ada are covered in other sections of the HIS report ISO IEC 2000 The profile is based on a computation model with the following features e A single processor e A fixed number of tasks 47 48 APPENDIX A THE RAVENSCAR PROFILE e A single invocation event for each task The invocation event may be generated by the passing of time for time triggered tasks or by a signal from either another task or the environment for sporadic tasks e Task interaction only by means of shared data with mutually exclusive access This set of features effectively supports building systems with the following kinds of components e Periodic tasks e Program driven sporadic tasks Interrupt driven sporadic tasks Protected objects implementing shared data typically with no entries P
64. l 522 e Upper bounds om the execution times of the operators of the types Time and Time Span in processor clock cycles The results of the test give the following WCET in cycles for each operation 68 APPENDIX C METRICS Operator Cycles Time Time_Span 58 Time Span Time 58 Time Time Span 58 Time Time 58 Time lt Time 44 Time lt Time 72 Time gt Time 62 Time gt Time 34 Time_Span Time_Span 58 Time_Span Time_Span 58 Time Span 47 Time Span x Integer 92 Integer x Time Span 99 Time_Span Time Span 1098 Time Span Integer 1092 abs Time Span 44 Time Span lt Span 98 Time Span lt Time Span 90 Time Span gt T me Span 100 Time Span gt Time Span 100 To Duration Time_Span 1139 Time Span Duration 129 Split Time Seconds Count Time Span 1142 Time Of Seconds Count Span 96 Nanoseconds Integer 1096 Microseconds Integer 1096 Milliseconds Integer 55 C 1 3 Delay Accuracy ALRM D 9 9 13 Metrics The implementation shall document the following metrics only those metrics that are significant in the context of the Ravenscar profile are cited e An upper bound on the execution time in processor clock cycles of a delay until statement whose requested value of the delay expression is less than or equal to the value of Real_Time Clock at the time of executing the statement The measured value is equal to 740 processor clock cycles e An upper bound
65. lays and the monotonic clock of the Real Time package are used In order to avoid undesirable interactions between input output and task scheduling the special Put operation of the System IO pack age is used The example program is designed to cover all the features which are needed in space embedded applications In particular the example includes e Task management Task synchronization e Time keeping and absolute delays e Ada interrupt management Floating point calculations 93 54 APPENDIX B EXAMPLE PROGRAM B 2 Temporal requirements of the tasks Figure B 1 shows the structure of the task set The task set will be analysed for the temporal requirements of the tasks as shown in table B 1 The period for task A is interpreted as a minimum inter arrival time demo HRT El ASER BY IT External_Interrupt BY IT External Interrupi WCET C2 A WCET_A2 E Real Time Py Monitor Exclusive E Text IO E Workload Figure B 1 Example task set Task Period Activities A 14 d1 B 20 by C 36 C1 C2 Table B 1 Temporal requirements of the example tasks Tasks A and C contain two logical blocks of activities while task B has only one Activity a4 corresponds to internal computation of task A and az to the execution time of task A inside resource Monitor Similarly corresponds to the
66. n be defined In the case of Ada there is a standard mechanism to enforce that only the required subset of the language is used by means of the pragma Restrictions and the restriction identifiers that are defined in the Ada Safety and Security annex ISO IEC 2007 Annex H Tasking has often been considered not safe for high integrity systems mainly due to the difficulty of analysing and verifying tasking programs However results in response time analysis for fixed priority preemptive scheduling Burns 1994 enable limited tasking mechanisms to be used even in this kind of systems One of the goals of the 8th International Real Time Ada Workshop IRTAW 8 which was held in 1997 in Ravenscar Yorkshire England was to define a safe tasking model for Ada The outcome of this work is known as the Ravenscar profile Baker and Vardanega 1997 The profile was slightly modified in the following IRTAW meetings after some experience was gained on its implementation and use It was later included in the Ada High Integrity Systems report ISO IEC 2000 and it finally made its way into the current Ada 2005 standard ISO IEC 2007 Annex D The profile defines a subset of Ada tasking that includes static tasks with no entries and protected objects with at most one entry a real time clock and delay until statements as well as protected interrupt handler procedures and other tasking related features A detailed description can be found in a
67. n pages sparc elf newlib libc library for SPARC family Contents of usr local gnatforleon src binutils 2 16 1 Adapted sources of binutils for GNATforLEON newlib 1 14 0 Adapted sources of newlib for GNATforLEON gcc 4 1 3 Adapted sources of gcc for GNATforLEON gcc 4 1 3 gcc ada Adapted sources of GNAT GPL 2007 for GNATfor LEON including GNATforLEON itself gdb 6 3 Adapted sources of gdb for GNATforLEON c interface include files for the C interface 4 1 INSTALLATION AND DIRECTORY STRUCTURE 33 4 1 5 Tools GNATforLEON includes the following tools in the usr local gnatforleon bin directory sparc elf addr2line utility to translate program addresses into file names and line numbers sparc elf ar library archiver sparc elf as cross assembler sparc elf c filt utility to demangle C symbols sparc elf gcc C cross compiler sparc elf gccbug a tool for reporting GCC Bugs sparc elf gcov coverage testing tool sparc elf gdb the GNU Debugger sparc elf gnat utility to list GNAT commands qualifiers and options Sparc elf gnatbind Ada binder Sparc elf gnatchop Ada source code splitter Sparc elf gnatfind Ada utility for locating definitions and or references to a specified entity or entities sparc elf gnatkr Ada file name kruncher Sparc elf gnatlink Ada linker sparc elf gnatls Ada library lister Sparc elf gnatmake Ada make utility Sparc elf gnatprep Ada pre processor
68. n to copy distribute and or modify the software Also for each author s protection and ours we want to make certain that every one understands that there is no warranty for this free software If the software is modified by someone else and passed on we want its recipients to know that what 73 74 APPENDIX D GNU GENERAL PUBLIC LICENSE they have is not the original so that any problems introduced by others will not reflect on the original authors reputations Finally any free program is threatened constantly by software patents We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses in effect making the program proprietary To prevent this we have made it clear that any patent must be licensed for everyone s free use or not licensed at all The precise terms and conditions for copying distribution and modification fol low Terms and conditions for copying distribution and modification 0 This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License The Program below refers to any such pro gram or work and a work based on the Program means either the Program or any derivative work under copyright law that is to say a work containing the Program or a portion of it either verbatim or with modifications and or translated into another language Hereina
69. natmake For instance sparc elf gnatmake hello The command line switches are described in the GNAT User s Guide Ada Core 2008a You can also compile bind and link separately sparc elf gcc c hello adb sparc elf gcc c tasking adb sparc elf gnatbind x hello ali sparc elf gnatlink hello ali See Ada Core 2008a for details on the switches and library files A link diagnostic information file with the symbols which are mapped by the linker together with information on global common storage allocation can be ob tained by using the following switch for gnatlink sparc elf gnatmake g hello largs Wl Map hello map As a result a link diagnostic file called hello map is created This kind of map files tend to be useful in embedded software development After all these compilation steps an ELF 32 SPARC executable called hello is obtained 22 CHAPTER 3 HOW TO USE GNATFORLEON 3 4 Debugging Ada programs on the development platform The simplest way you can test your program is by using a LEON2 simulator on your development platform If you have the TSIM simulator you can do tsim leon hello And typing go from the command prompt you will get the following output Hello periodic Hello periodic Hello periodic Hello periodic Hello periodic Hello periodic Hello periodic Hello periodic Hello periodic Hello periodic Hello sporadic Hello periodic Running the program on TSIM by itself does not provi
70. nerally NO WARRANTY BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE THERE IS NO WARRANTY FOR THE PROGRAM TO THE EXTENT PERMIT TED BY APPLICABLE LAW EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND OR OTHER PARTIES PROVIDE THE PROGRAM AS IS WITHOUT WARRANTY OF ANY KIND EITHER EXPRESSED OR IMPLIED INCLUDING BUT NOT LIM ITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH 78 12 APPENDIX D GNU GENERAL PUBLIC LICENSE YOU SHOULD THE PROGRAM PROVE DEFECTIVE YOU ASSUME THE COST OF ALL NECESSARY SERVICING REPAIR OR CORREC TION IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER OR ANY OTHER PARTY WHO MAY MODIFY AND OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE BE LIABLE TO YOU FOR DAMAGES IN CLUDING ANY GENERAL SPECIAL INCIDENTAL OR CONSEQUEN TIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES End of terms and conditions 79 How to Apply These Terms to Your New Programs If you develop a new program and you want it to be of the greatest possible use to t
71. ng figure 2 2 Ravenscar compliance of Ada programs is enforced by means of the configuration pragma Profile Ravenscar GNATforLEON uses a restricted version of GNARL with reduced size and complexity which was developed by AdaCore with certification in mind and just to support the Ravenscar profile A special version of GNULL is also used which interfaces directly with the kernel All this complexity is hidden to the programmer who only needs to insert the pragma Profile Ravenscar in the GNAT configuration file usually named gnat adc 2 4 Interface for C programs The kernel can also be used with programs written in C see section 3 7 Since C has no tasking constructs the kernel functions for creating and handling threads have to be explicitly called from C A C API see figure 2 2 is provided for this purpose The C interface is implemented in a C interface layer CIL which is integrated with the GCC compilation system 2 5 Hardware and software environment The GNATforLEON kernel is intended to be used with a GNAT or GCC compilation system targeted to a LEON2 computer In order to use it effectively the following components are required 2 5 1 Development platform Real time software based on ORK can be developed on a PC compatible sys tem with a GNU Linux operating system The software has been tested with the Ubuntu 6 0 6 distribution of GNU Linux The cross development system consists of the following packages targeted
72. nterrupt is issued by the real time clock timer tick e Timer 2 This interrupt is issued by the general purpose timer 46 CHAPTER 4 GNATFORLEON ORK REFERENCE e UART 1 RX TX This interrupt is generated by the UART channel 1 each time a data word has been correctly received and each time a data word has been sent e UART 2 RX TX This interrupt is generated by the UART channel 2 each time a data word has been correctly received and each time a data word has been sent e External Interrupt 3 2 1 0 The sources of these interrupts are located out side the LEON2 processor Consequently these interrupts are input to the processor through pins ErtINT 3 2 1 0 e DSU DSU trace buffer interrupt e PCI PCI interrupt e Correctable Error In Memory EDAC interrupt 4 5 3 Compiling the kernel Procedures for rebuilding the whole GNATforLEON cross compilation system and adapting GNATforLEON are the in usr 1ocal gnatforleon src directory In order to rebuild the whole GNATforLEON cross compilation system you need to do the following 1 Edit the file Makefile in order to change GNATforLEON default installa tion directory usr local gnatforleon and set the GNATBOOT path to a valid native GNAT GPL 2008 distribution 2 Type make The procedure will take about 10 15 minutes on a modern computer On suc cessful execution the GNATforLEON cross compilation system will be installed Since this procedure takes a long time it
73. o download the latest version of GNATforLEON ORK 4 from the ORK web site http www dit upm es ork 1 6 RELATED DOCUMENTS 3 1 6 Related documents The following documents contain additional information about software tools that can be used to develop real time software with GNATforLEON 1 Ada 2005 Reference Manual ISO IEC 2007 2 Ada 2005 Rationale Barnes 2008 User s Guide Ada Core 20082 4 GNAT Reference Manual Ada Core 2008b 5 GNAT Programming Studio User Guide Ada Core 2007 6 Debugging with GDB Stallman and Pessch 2007 1 7 Problem reporting instructions If you obtained GNATforLEON from a support organization we recommend you contact that organization first You can find contact information for support orga nizations on the ORK web site http www dit upm es ork In any event we also recommend that you send bug reports for GNATforLEON to ork dit upm es We welcome bug reports as they are a vital part of the process of the continuing improvement of You will help us and make it more likely that we will look at your report in a timely manner if you follow these guidelines e Please report each bug in a separate message and add a short but specific subject e Please include full sources We can t duplicate errors without the full sources Include all sources in the single email message with appropriate indications in the multiple file cases see below Also say exactly wh
74. olean pragma Inline Within Interrupt Stack Function that tells whether the Address passed as argument belongs to the interrupt stack that is currently being used if any It returns True if Stack Address is within the range of the interrupt stack being used In case Stack Address is not within the interrupt stack or no interrupt is being handled end System BB Interrupts Interrupt handlers are always executed using an interrupt stack The size of the interrupt stack can be modified by the user changing the value of System BB Parameters Interrupt_Stack_Size Interrupt handlers are called directly from the hardware and are executed as if they were directly invoked by the interrupted thread but using the interrupt stack The procedure Attach Handler must be called to attach a handler to an interrupt The required arguments for this procedure are e Handler The address of the procedure used as interrupt handler e Id The interrupt identifier 44 CHAPTER 4 GNATFORLEON ORK REFERENCE If the active priority of a running thread is equal to or greater than the one of an interrupt the interrupt will not be recognized by the processor However the inter rupt will remain pending until the active priority of the running task becomes lower than the priority of the interrupt and only then will the interrupt be recognized An important implication of this interrupt model is that users should always use distin
75. on tasks for the hello example package Tasking is procedure Background pragma No_Return Background background activity does not terminate end Tasking The Tasking package specification contains no other declarations All the appli cation activities are included in the package body listing 3 4 Listing 3 4 Body of the Tasking package tasking adb application tasks for the hello example with Ada Real Time used for Clock Time Span Milliseconds with System BB Serial Output use System BB Serial Output used for Put Line package body Tasking is use Ada Real Time Task and protected object declarations type Cycle Count is mod 10 task Periodic is pragma Priority 1 end Periodic task Sporadic is pragma Priority 2 end Sporadic protected Event is pragma Priority 2 procedure Signal C Cycle Count entry Wait out Cycle Count private Occurred Boolean False Cycle Cycle Count 0 end Event 20 CHAPTER 3 HOW TO USE GNATFORLEON Background procedure procedure Background is C Cycle Count 0 begin loop C i C l end loop end Background Task and protected object bodies task body Periodic is Period Time Span Milliseconds 1 000 15 Next Time Clock Cycle Cycle Count 1 begin loop delay until Next Put Line Hello periodic if Cycle 0 then Event Signal Cycle s
76. on the lateness of a delay until statement in a situation where the value of the requested expiration time is after the time the task begins executing the statement the task has sufficient priority to preempt the processor as soon as it becomes ready and it does not need to wait for any other execution resources The upper bound is expressed as a function of the difference between the requested expiration time and the clock value at the time the statement begins execution The lateness of a delay until statement is obtained by subtracting the requested expiration time from the real time that the task resumes execution following this statement C 1 ADA LRM ANNEX C AND D METRICS 69 The following measurements have been performed C 1 4 One task background task The delay until lateness upper bound for a call to a delay until statement is 8051 clock cycles 161 js using a 50 MHz system clock This lateness occurs when the time of the delay until coincides with a second boundary It must be noted that the clock interrupt occurs every second in the kernel tested If the time of the delay until statement does not coincide with a clock interrupt the lateness upper bound for the execution of a delay until statement is 7061 clock cycles 141 2 N tasks background task The lateness of delay until for tasks is 294825 84 7 x N us when the time of the delay until coincides with a clock interrupt Otherwise it is 201 8 4 7x N
77. pan 36 Time Unit Priority of the interrupt used Priority External Interrupt 2 constant System Interrupt Priority System Interrupt Priority First 5 procedure Background is begin loop null end loop end Background task A is pragma Priority System Priority Last end A task B is pragma Priority System Priority Last 1 end B 60 APPENDIX B EXAMPLE PROGRAM task C is pragma Priority System Priority Last 2 end C protected Monitor is pragma Priority System Priority Last procedure Exclusive Time Ada Real_Time Time_Span Running_Task Tasks end Monitor This task forces a interrupt every Period task Interrupt is pragma Priority System Priority Last end Interrupt protected Interrupt Semaphore is pragma Priority Priority Of External Interrupt 2 entry Wait procedure Signal pragma Attach Handler Signal Ada Interrupts Names External Interrupt 2 private Signaled Boolean False end Interrupt Semaphore protected body Interrupt Semaphore is entry Wait when Signaled is begin Signaled False end Wait procedure Signal is begin Signaled True end Signal end Interrupt Semaphore B 5 EXAMPLE CODE 61 task body Interrupt is Next_Time Ada Real_Time Time Time_Zero begin loop delay until Next_Time Force External Interrupt 2 Next Time Next Time Period A end loop end Interr
78. plication with the Raven scar profile is left as a responsibility to the programmer e Concurrency is handled by the kernel No processes can be created only threads and only through the CIL capabilities Moreover the main function must not terminate as the Ravenscar profile states clearly As a result the main program has the following general structure Listing 3 6 Structure of a main C program void main void 1 C variable declaration Ada packages elaboration GNATforLEON kernel initialization C variable initialization Tasks creation statements Environment Task s infinite loop Notice that the main function never terminates This is due to the GNAT requirement that the environment task never ends under the Ravenscar profile the same happens with the Ada example in section 3 4 Tasks must not terminate either as required by the Ravenscar profile There fore the structure of task bodies will be as follows Listing 3 7 Structure of C thread code void task body void 1 Task s local variable declaration and initialization while 1 4 task code 3 e Ada packages must be elaborated before functions exported to C can be used This means that the function adainit must be called as soon as possible from the C program Although the program must not terminate a call to adafinal at the end would be desirable just in case 3 7 WORKING WITH C PROGRA
79. ppendix A The restrictions in Ada tasking defined in the Ravenscar profile enable tasking to 9 10 CHAPTER 2 SOFTWARE OVERVIEW be supported by a small reliable kernel instead of a full operating systems ORK is one such kernel which enables critical real time systems to be executed on a bare processor with no underlying operating system The kernel is integrated with the GNAT compilation system A special cross compilation version of GNAT is included in the GNATforLEON distribution Real time programs are written in a subset of Ada which is consistent with the Ravenscar profile and with other non tasking restrictions as desired according to the degree of integrity that is required for the program The restrictions can be enforced at compilation time by means of appropriate restriction pragmas The code generated by GNATforLEON can be loaded on the target hardware by means of appropriate bootstrap loaders It can also be executed on a target simulator for testing purposes Debugging support is available with the GDB version that comes with the GNATforLEON distribution GNATforLEON can be used from the GNAT Programming Studio GPS The kernel has been designed for efficient support of Ada tasking constructs but can also be used with C programs A C interface package is provided for this purpose see section 3 7 on page 25 2 2 Architecture of ORK The kernel consists of the following Ada packages figure 2 1 e System BB Root p
80. rictions listed in A 3 above except for the two restrictions on Ada Execution Time Group Budget and Ada Execution Time Timers 92 APPENDIX A THE RAVENSCAR PROFILE Appendix B Example program B 1 Description The goal of this example is to show the functionality of GNATforLEON The example program has three tasks which spend their computation time call ing the Whetstone benchmark This benchmark performs floating point operations developed for the Performance Issues Working Group PIWG test suite In order to exercise communication among tasks two of the three tasks interact through a protected object One task is sporadic and the other is periodic The third task is an independent periodic task The sporadic task is activated by a hardware interrupt for which it waits on an protected entry with a simple boolean barrier A protected procedure is used to handle the interrupt in accordance with the GNATforLEON interrupt model The protected procedure opens the barrier and then the sporadic task becomes runnable After the task executes its code the barrier is closed again A periodic task activates the hardware interrupt LEON2 has special registers which allows the user to force hardware interrupts by software Such registers are used by the periodic task to activate the hardware interrupt at regular intervals All the tasks print the value of Real Time Clock whenever they start and fin ish executing their body Only absolute de
81. rogram in ob ject code or executable form with such an offer in accord with Subsection b above The source code for a work means the preferred form of the work for making modifications to it For an executable work complete source code means 76 APPENDIX D GNU GENERAL PUBLIC LICENSE all the source code for all modules it contains plus any associated interface definition files plus the scripts used to control compilation and installation of the executable However as a special exception the source code distributed need not include anything that is normally distributed in either source or binary form with the major components compiler kernel and so on of the operating system on which the executable runs unless that component itself accompanies the executable If distribution of executable or object code is made by offering access to copy from a designated place then offering equivalent access to copy the source code from the same place counts as distribution of the source code even though third parties are not compelled to copy the source along with the object code You may not copy modify sublicense or distribute the Program except as expressly provided under this License Any attempt otherwise to copy modify sublicense or distribute the Program is void and will automatically terminate your rights under this License However parties who have received copies or rights from you under this License will not have their
82. rotected objects for event synchronization with at most one entry called by a single signalling task These components are considered to be expressive enough for implementing high integrity systems for space applications on a single processor A 2 Definition The Ravenscar profile is defined by the following restrictions ISO IEC 2005 A 2 1 Forbidden features RP1 Task types and object declarations other than at the library level Thus there is no hierarchy of tasks RP2 Dynamic allocation and unchecked deallocation of protected and task objects RP3 Requeue RP4 ATC asynchronous transfer of control via the asynchronous select statement RP5 Abort statements including Abort Task in package Ada Task Identification RP6 Task entries RP7 Dynamic priorities RP48 Ada Calendar package RP9 Relative delays RP10 Protected types and object declarations other than at the library level RP11 Protected types with more than one entry RP12 Protected entries with barriers other than a single boolean variable declared within the same protected type A 2 DEFINITION 49 RP13 An entry call to a protected entry with a call already queued RP14 Asynchronous task control RP15 All forms of select statements RP16 User defined task attributes RP17 Dynamic interrupt handler attachments RP18 Task termination RP19 Specific termination handlers RP20 Local timing events RP21 Execution time timers RP22 Group budgets A 2
83. sporadic 0 p sporadic stackaddress2 stacksize while 1 1 if count gt 1000 count 0 system bb delay until system bb clock 41000000000 adafinalO 3 7 WORKING WITH C PROGRAMS 29 As it follows from the example a single header file must be included gnatforleon h which includes the other CIL header files required by the program 3 7 4 Compiling a C program The compiler has to know which Ada packages have to be elaborated As such information cannot be provided in the C program nor in the Makefile a dummy Ada procedure that uses the GNATforLEON packages has to be added to the program The code of this procedure is shown on listing 3 9 Listing 3 9 Specification of the stub procedure for C programs with System BB Threads with System BB Time with System BB Interrupts with System BB Serial Output procedure Stub is begin null end Stub The steps that have to be followed to produce an GNATforLEON based appli cation written in C are 1 Compile your C code sparc elf gcc I usr local gnatforleon include g c c program c 2 Compile the Ada code sparc elf cc c stub adb 3 Bind the Ada program sparc elf gnatbind n t Mmain stub ali 4 Link everything together sparc elf gnatlink stub ali c program o lgnarl o c program 30 CHAPTER 3 HOW TO USE GNATFORLEON Chapter 4 GNATforLEON ORK 4 reference 4 1 Installation and directory structure 4 1 1 Gettin
84. st cause any work that you distribute or publish that in whole or in part contains or is derived from the Program or any part thereof to be licensed as a whole at no charge to all third parties under the terms of this License 75 c If the modified program normally reads commands interactively when run you must cause it when started running for such interactive use in the most ordinary way to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty or else saying that you provide a warranty and that users may redistribute the program under these conditions and telling the user how to view a copy of this License Exception if the Program itself is interactive but does not normally print such an an nouncement your work based on the Program is not required to print an announcement These requirements apply to the modified work as a whole If identifiable sections of that work are not derived from the Program and can be reasonably considered independent and separate works in themselves then this License and its terms do not apply to those sections when you distribute them as separate works But when you distribute the same sections as part of a whole which is a work based on the Program the distribution of the whole must be on the terms of this License whose permissions for other licensees extend to the entire whole and thus to each and every part regardless of who wrote it
85. t free software and it is not part of GNATforLEON See http www gaisler com for futher details 24 CHAPTER 3 HOW TO USE GNATFORLEON 3 5 2 Making boot PROMS GNATforLEON applications are linked to run from the beginning of the RAM area at address 0x40000000 To make a boot PROM that can run on a standalone target use the mkprom utility This will create a compressed boot image that will load the application to the beginning of RAM initiate various LEON registers and finally start the application mkprom will set all target dependent parameters such as memory sizes number of memory banks waitstates baudrate and system clock The applications do not set these parameters themselves and thus do not need to be re linked for different board architectures The example below creates a boot PROM for a system with 1 Mbyte RAM one waitstate during write 3 waitstates for ROM access and a 41 MHz system clock For more details see the mkprom manual mkprom ramsz 1024 ramwws 1 romws 3 hello freq 41 hello To create a Motorola S record file for PROM programmer use objcopy sparc elf objcopy 0 srec hello hello srec A file called hello srec is created It is possible to use the TSIM simulator to load and test the resulting file 3 5 3 Using GDB with GRMON and the remote target mon itor It is possible to use GRMON as the remote target and connect it with sparc elf gdb enabling symbolic debugging of target applications To initi
86. t to the following set of pragmas pragma Task Dispatching Policy FIFO_Within_Priorities pragma Locking Policy Ceiling Locking pragma Detect Blocking pragma Restrictions Abort Statements No Dynamic Attachment No Dynamic Priorities No Implicit Heap Allocations No Local Protected Objects No Local Timing Events Protected Type Allocators No Relative Delay Requeue Statements No Select Statements No Specific Termination Handlers No Task Allocators No Task Hierarchy No Task Termination Simple Barriers Max Entry Queue Length gt 1 A 4 EXTENDED PROFILE 51 Max Protected Entries gt 1 Max Task Entries gt 0 No_Dependence gt Ada Asynchronous Task Control No_Dependence gt Ada Calendar No Dependence gt Ada Execution Time Group Budget No Dependence gt Ada Execution_Time Timers No_Dependence gt Ada Task_Attributes A 4 Extended profile ORK supports the following features which are not allowed in the Ravenscar pro file XP01 One execution time timer per task declared at the library level XP02 Group budgets Task groups must be static and declared at the library level Notice that using pragma Profile Ravenscar in your program will make the com piler report the use of execution time timers and group budgets as incorrect If you need to use the extended features you should provide the full set of pragmas and rest
87. tems and Programming Lan guages Addison Wesley 3 edition Dobbing B and de la Puente J A 2003 Session report Status and future of the Ravenscar profile Ada Letters XXIII 4 55 57 Proceedings of the 12th International Real Time Ada Workshop IRTAW 12 8l 82 BIBLIOGRAPHY ECSS 2003 ECSS E 40 Part 1B Space engineering Software Part 1 Prin ciples and requirements Available from ESA Gaisler Research 2005 LEON2 Processor User s Manual Gaisler Research 2007 GRMON User s Manual Available at http www gaisler com doc grmon pdf Giering E W and Baker T P 1994 The GNU Ada Runtime Library GNARL Design and implementation In WADAS 94 Proceedings of the eleventh annual Washington Ada symposium amp summer ACM SIGAda meeting on Ada pages 97 107 New York NY USA ACM Press ISO IEC 1999 Std 9899 1999 Programming Languages C ISO IEC 2000 TR 15942 2000 Guide for the use of the Ada programming language in high integrity systems ISO IEC 2003 Std 9945 1 2003 Portable Operating System Interface POSIX ISO IEC 2005 TR 24718 2005 Guide for the use of the Ada Ravenscar Profile in high integrity systems Based on the University of York Technical Report Y CS 2003 348 2003 ISO IEC 2007 Std 8652 1995 Amd 1 2007 Ada 2005 Reference Manual Lan guage and Standard Libraries Published by Springer Verlag ISBN 978 3 540 69335 2 SPARC International 199
88. the ORK 2 1 0which are spec ified in Annex C and D of the Ada Language Reference Manual and are allowed by the Ravenscar profile The metrics are expressed in processor cycles To relate them to time figures in seconds they should be divided by the processor clock frequency C 1 1 Protected Procedure Handlers ALRM C3 1 15 Overhead of interrupt handlers The following metric shall be documented by the implementation e The worst case overhead for an interrupt handler that is a parameterless pro tected procedure in clock cycles This is the execution time not directly at tributable to the handler procedure or the interrupted execution It is estimated as C A B where is how long it takes to complete a given sequence of instructions without any interrupt B is how long it takes to complete a normal call to a given protected procedure and C is how long it takes to complete the same sequence of instructions when it is interrupted by one execution of the same procedure called via an interrupt The measured values are interrupt overhead test Cycles 1969334 Cycles 1970270 cycles A B 4930583 cycles C 4931993 cycles C A B 1410 The average overhead of a protected procedure as interrupt handler is 1410 processor cycles 65 66 APPENDIX C METRICS This metric has been measured with the TSIM 2 0 6 simulator Otherwise spe cial hardware such as signal generators and logic analy
89. tial offset for the tasks It is enough time to elaborate the program Offset constant Ada Real Time Time Span Ada Real Time Milliseconds 500 Time Zero constant Ada Real Time Time Ada Real Time Time of 0 Ada Real Time Time Span Zero Offset This procedure prints Real Time Clock Time Zero procedure Print RT Clok is Seconds Count From Time Zero Ada Real Time Seconds Count Time Span From Time Zero Ada Real Time Time Span Duration From Time Zero Duration B 5 EXAMPLE CODE 59 begin Ada Real_Time Split Ada Real Time Clock Offset Seconds Count From Time Zero Time Span From Time Zero Duration From Time Zero Duration Seconds Count From Time Zero Ada Real Time To Duration Time Span From Time Zero System IO Put System IO Put Duration Image duration_From_Time_Zero end Print_RTClok Temporal parameters of Tasks subtype Tasks is character range A C WCET 1 constant Ada Real Time Time Span 1 Time Unit WCET 2 constant Ada Real Time Time Span 2 Time Unit Period A constant Ada Real Time Time Span 14 Time Unit WCET constant Ada Real Time Time Span 6 Time Unit Period B constant Ada Real Time Time Span 20 Time Unit WCET C1 constant Ada Real Time Time Span 2 Time Unit WCET C2 constant Ada Real Time Time Span 6 Time Unit Period C constant Ada Real Time Time S
90. to ELF 32 LEON2 e GNAT GPL 2008 GNU Ada 2005 compilation system e GCC 4 1 3 GNU C compiler GDB 6 3 GNU debugger newlib 1 14 Cygnus C library binutils 2 16 1 GNU binary utilities 2 5 HARDWARE AND SOFTWARE ENVIRONMENT 13 e ORK 2 1 0 ORK kernel with C Interface Library and GNAT patches You can download all the above mentioned packages from http www dit upm es ork Section 4 1 shows how to install GNATforLEON compilation system from both the binary and source distributions You also may find it useful to have the GNAT Programming Studio GPS https libre adacore com gps for developing applications with GNATfor LEON 2 5 2 Execution platform The execution platform for GNATforLEON based programs is a LEON2 computer with at least 500 KB memory Programs can be loaded into an LEON2 based computer memory by means of appropriate tools e g GRMON or mkprom Once loaded the software can be debugged by running GDB on the development com puter which communicates with the target computer by means of a communication line e g serial line or Ethernet Programs can also be tested and debugged on the development platform using the TSIM simulator which can be connected to GDB using a socket connection TSIM is not free software and it is not part of GNATforLEON See http www gaisler com for further details 14 CHAPTER 2 SOFTWARE OVERVIEW Chapter 3 How to use GNATforLEON 3 1 Software d
91. tor version 2 0 6 professional version Copyright C 2001 Gaisler Research all rights reserved For latest updates go to http www gaisler com Comments or bug reports to tsim gaisler com serial port A on stdin stdout allocated 4096 K RAM memory in 1 bank s allocated 2048 K ROM memory icache 1 4 kbytes 16 bytes line 4 kbytes total dcache 1 4 kbytes 16 bytes line 4 kbytes total section text addr 0x40000000 size 105152 bytes section data addr 0 40019 0 size 8060 bytes read 476 symbols tsim gt g resuming at 0x40000000 Task A running RT Clock 0 00 Task A finishing RT Clock 0 30 Task B running RT Clock 0 30 Task B finishing RT Clock 0 92 Task C running RT Clock 0 92 Task C finishing RT Clock 1 74 A A B B Task A running RT Clock 1 74 Task A finishing RT Clock 2 06 Task B running RT Clock 2 06 Task B finishing RT Clock 2 68 The start and termination time of each task cycle can vary depending of the GNATforLEON version B 5 EXAMPLE CODE Task Task Task Task Task Task Task Task Task Task gt gt gt running RT Clock finishing RT Clock running RT Clock finishing RT Clock running RT Clock finishing RT Clock running RT Clock finishing RT Clock running RT Clock finishing RT Clock 2 80 3 10 3 60 4 42 4 42 4 72 4 72 b 34 5 60 5 90 57 There are small variations with respect to the timetable of figure B 2 whic
92. udgets 3 2 WRITING ADA PROGRAMS 17 e User defined task attributes e Dynamically attached interrupt handlers e Task termination If your program has strong integrity requirements you may also wish to restrict some of the sequential constructs of Ada as well see the ALRM ISO IEC 2000 for guidelines on the Ada features you may wish to limit GNATforLEON assumes that the following restrictions are also applicable to your program e No allocators this means that there are no new statements This is required as GNATforLEON supports only static storage e No Ada Text IO package This is required as ORK does not directly sup port any input output device but a serial output line which is not accessible through Ada Text IO Notice that the above restrictions are common in embedded systems and do not impose any additional limitation on what could be considered as common practice Warning 3 1 GNATforLEON ORK users are recommended to assign distinct priorities to all tasks and protected objects 3 2 2 The GNAT configuration file Configuration pragmas are put in a special source file called gnat adc see Ada Core 2008a You can have GNAT check all the above restrictions for you by compiling the program with a Ravenscar configuration pragma as shown in the following template Listing 3 1 Sample gnat adc file gnat adc minimum configuration file template for the Ravenscar profile pragma Profile Ravenscar
93. ueue This type contains the time of alarms relative of Timing Events the next alarm type TE Alarm Queue ld is access all TE Alarm Queue Type used as TE Alarm Queue identifier Null TE Alarm Queue ld constant TE Alarm Queue ld null type TE Alarm Queue is record Previous Alarm TE Alarm Queue ld Null TE Alarm Queue ld Alarm Time System BB Time Time System BB Time Time Last TE Id Integer 0 Next Alarm TE Alarm Queue ld Null TE Alarm Queue 19 end record end System BB Threads Before calling any kernel operation the initialization routine Initialize must be explicitly invoked Its purpose is to initialize the ready queue as well as the descriptors of the environment thread which executes the main procedure and the dummy thread which is executed when there is no ready thread in the system Once the kernel has been initialized threads can be created invoking the pro cedure Thread Create This procedure needs to know the pointer to the function to execute and its argument its priority and its required stack size With this information a new thread is created Both the thread descriptor and the new stack for the thread are obtained from a preallocated pool so that no dynamic memory allocation is needed The function Thread Self is used to obtain the identity of the currently running thread The base priority of the thread which is the priority of the thread witho
94. upt protected body Monitor is procedure Exclusive Time Ada Real Time Time Span Running Task Tasks is begin Execution Time Time System IO Put Task System IO Put Running Task System IO Put finishing Print RTClok System lO New Line end Exclusive end Monitor task body A is begin loop Interrupt Semaphore Wait System IO Put Task A running Print RTClok System lO New Line Execution Time WCET 1 Monitor Exclusive WCET_A2 A end loop end A task body B is Next Time Ada Real Time Time Time Zero begin loop delay until Next Time System IO Put Task B running Print RTClok System lO New Line Execution Time WCET B 62 APPENDIX B EXAMPLE PROGRAM Next_Time Next_Time Period_B System lO Put Task B finishing Print RTClok System lO New Line end loop end B task body C is Next Time Ada Real Time Time Time Zero begin loop delay until Next Time System IO Put Task C running Print RTClok System lO New Line Execution Time WCET_C1 Monitor Exclusive WCET_C2 C Next Time Next Time Period C end loop end C begin Kernel Peripherals Init Channel gt 1 BaudRate gt 115200 Parity gt Kernel Peripherals None FlowControl gt Kernel Peripherals Off end Tasks Listing B 4 Force External Interrupt 2 with System BB Peripherals Reg
95. ut taking into account the dynamic priority changes which may be caused by the Ceiling Locking policy can be changed by calling the procedure Set Priority The current base priority of a thread can be obtained calling the procedure Get Priority The synchronization of threads is usually achieved using condition variables However the Ravenscar Profile disallows complex synchronization patterns and two simple procedures are enough for supporting that simpler synchronization pattern The procedure Sleep unconditionally suspends the current thread As a result the currently executing thread will leave the CPU The procedure Wakeup makes a 40 CHAPTER 4 GNATFORLEON ORK REFERENCE previously suspended thread become ready The thread will be inserted at the tail of its active priority so that the thread will resume execution Scheduling of threads is performed according to the FIFO Within Priorities and Ceiling Locking policies see ALRM D 2 3 4 2 8 Time management The operations related with time are implemented in package System BB Time Listing 4 2 Specification of System BB Time Package in charge of implementing clock and timer functionalities pragma Restrictions Elaboration Code with System BB Peripherals Used for Clock Freq Hz package System BB T ime is pragma Preelaborate type Time is mod 2 xx 64 for Time Size use 64 Time is represented at this level as a 64 bit natural number The
96. zers should be used to mea sure this overhead on real target Other metrics have been measured on the same simulator as well as on real hardware and the differences were insignificant C 1 2 Monotonic Time ALRM D 8 33 Definition of type Time The implementation shall document the values of Time First Time Last Time Span Last Time Span Unit and Tick These metrics are under development ALRM D 8 34 Time base and underlying hardware The implementation shall document the properties of the underlying time base used for the clock and for type Time such as the range of values supported and any relevant aspects of the underlying hardware or operating system facilities Time is represented internally as a 64 bit integer number of ticks The tick is currently 4 times the period of the processor clock Therefore the interval of time values that can be represented in this way is approximately 23360 4 23360 years for a 50 Mhz processor Time is a count of ticks since the clock was started The LEON2 hardware provides two timers apart from the special Watchdog timer which can be programmed to be either of single shot type or of periodic type One of them the Real Time Clock is used as a timestamp counter and the other called General Purpose Timer as a high resolution timer The former timer provides the basis for a high resolution clock while the latter offers the required support for precise alarm handling Both timers are

GNATforLEON / ORK+ User Manual - dit/UPM

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