Custom trap functions

[Alexanderv66]

I need to create my own exception handling functions. In Erika, exceptions calls a trap function, such as osEE_tc_trap_bus, osEE_tc_trap_context and others. How to add custom function call into trap handler's?

[e.guidieri]

Unfortunately,

the support for custom exception handler's is not finished: the code would support it, but the generator does not support it yet.

But, since all erika's files are contained in a library, you could always override a symbols providing the implementation in a file in the application.

I suggest you to copy ee_tc_trapvec.c in your project and customize it in the way you want, the only thing that needs to be preserved is the header for the exception vector (line: 1272), if your are using Hightec.

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__asm__ ("                                  \n\
  .section .traptab_cpu0, \"ax\", @progbits \n\
  .align 8                                  \n\
  .globl _exit                              \n\
  .globl __TRAPTAB                          \n\
__TRAPTAB:                                  \n\
");

Kind Regards,
Errico

[Alexanderv66]

I was modified the ee_tc_trapvec.c starting on line 1298 with that:

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...
#if (defined(OSEE_MEMORY_PROTECTION))
OSEE_TC_TRAP_DEFINITION(osEE_tc_trap_protection, osEE_tc_protection_handler)
#elif (defined(OSEE_TC_TRAP_PROT_TRAP))
OSEE_TC_TRAP_DEFINITION(osEE_tc_trap_protection, OSEE_TC_TRAP_PROT_TRAP)
#elif (defined(OSEE_TIMING_PROTECTION))
OSEE_TC_TRAP_DEFINITION_WITH_CALL(osEE_tc_trap_protection,
  osEE_tc_default_trap_handler)
#else
//OSEE_TC_TRAP_DEFAULT(osEE_tc_trap_protection)
  __asm__ (".globl " "osEE_tc_trap_protection");  \
    __asm__ ("osEE_tc_trap_protection" ":");        \   
    __asm__ ("j " "user_tc_trap_protection");       \ <- jump to users trap processing function
    __asm__ (".align 5");
#endif /* OSEE_TC_TRAP_PROT_TRAP */
...

And added user code for this trap in main.c:

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void user_tc_trap_protection()
{
	logger->addMessage("protection trap occurred");
}

And user_tc_trap_protection() was successfully called when i artificially inject error as this:

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char* exc_pointer = NULL;
*exc_pointer = 100;

thank you

[e.guidieri]

Hi,

Remember to save a lower context before calling C code, restore it after the call and return from the exception with rfe.

This would be a right wrapper to your user_tc_trap_protection

Code: Select all

  __asm__ (".globl " "osEE_tc_trap_protection");  \
  __asm__ ("osEE_tc_trap_protection" ":");	\
  __asm__ ("svlcx");              \
  __asm__ ("call user_tc_trap_protection"); 
  __asm__ ("rslcx");              \
  __asm__ ("rfe");                \
  __asm__ (".align 5");

Regard

[Alexanderv66]

I missed the context save/restore operation and call instruction. And this omission led to context underrun trap. Thanks for useful clarification