Hardfault CortexM re-handled irq

Kernel
1

I’m try to re direct interrupts, but find that in certain situations I’m getting hard faults. I’ve essentially done the following:

#define VECTOR_MBR 0x20000000
#define VECTOR_OFFSET 16
uint32_t volatile __attribute__((section(".vector_mbr"))) vectorAddr = 0;
typedef void (*p_function)(void);
static void jump_to(int32_t irqn) {
  uint32_t *index = (uint32_t *)vectorAddr + VECTOR_OFFSET;
  p_function jumpFunc = (p_function)index[irqn];
  jumpFunc();
}
#if configUSE_MBR_FUNCTIONS == 1 /* vPortSVCHandler */
void SVC_Handler(void) {
  if (vectorAddr == 0) {
    SVC_Handler_MBR();
  } else {
    jump_to(SVCall_IRQn);
  }
}
#endif

#if configUSE_MBR_FUNCTIONS == 1 /* xPortPendSVHandler */
void PendSV_Handler(void) {
  if (vectorAddr == 0) {
    PendSV_Handler_MBR();
  } else {
    jump_to(PendSV_IRQn);
  }
}

void SysTick_Handler(void) { /* xPortSysTickHandler */
  if (vectorAddr == 0) {
    SysTick_Handler_MBR();
  } else {
    jump_to(SysTick_IRQn);
  }
}
#endif

and in FreeRTOS config

    #if configUSE_MBR_FUNCTIONS == 1
    void SysTick_Handler(void);
    #define xPortSysTickHandler     SysTick_Handler_MBR
    #else
    #define xPortSysTickHandler     SysTick_Handler
    #endif

#if configUSE_MBR_FUNCTIONS == 1
#define xPortPendSVHandler PendSV_Handler_MBR
#define vPortSVCHandler SVC_Handler_MBR
#define xPortSysTickHandler SysTick_Handler_MBR
#else
#define xPortPendSVHandler PendSV_Handler
#define vPortSVCHandler SVC_Handler
#define xPortSysTickHandler SysTick_Handler
#endif

Is there an obvious reason this would cause a hard fault, or do I need to look elsewhere?

In testing here, vectorAddr == 0 and I know its calling the _MBR functions.

2

FreeRTOSConfig.h (8.6 KB)

Attached my config. configASSERT is defined, etc.

3

One big issue is that when you enter your PendSV_Handler function, the complier is going to save some registers on the stack and thus not match the expected state of the handler.

You might be able to write a handler in assembly that uses just the pre-saved registers (or saves and restores registers needed) and makes the decision and JUMPS to the FreeRTOS handler, so it is entered as if the vector just went to it.

4

Agree with Richard. For at least PendSV you’ll want to write the re-vectoring in assembly language and use only R0 - R3. Otherwise you can get context corruption.