fault.c

/*
 * Fault handlers, stolen from FreeRTOS web (www.FreeRTOS.org)
 *
 * 2009-2010 Michal Demin
 *
 */

#ifdef USE_HF_DEBUG
void HardFault_Handler(void) __attribute__ ((naked));

struct stack_t {
  unsigned long r0;
  unsigned long r1;
  unsigned long r2;
  unsigned long r3;
  unsigned long r12;
  unsigned long lr;
  unsigned long pc;
  unsigned long psr;
};

#define assert_break() do { __asm volatile("bkpt 0"); while(1); } while (0)

void assert_failed(unsigned char *function, unsigned int line)
{
  (void)function;
  (void)line;
  assert_break();
}

static void fault_halt(unsigned long *hardfault_args)
{
  //(void)stack;

  volatile unsigned long stacked_r0;
  volatile unsigned long stacked_r1;
  volatile unsigned long stacked_r2;
  volatile unsigned long stacked_r3;
  volatile unsigned long stacked_r12;
  volatile unsigned long stacked_lr;
  volatile unsigned long stacked_pc;
  volatile unsigned long stacked_psr;
  volatile unsigned long _CFSR;
  volatile unsigned long _HFSR;
  volatile unsigned long _DFSR;
  volatile unsigned long _AFSR;
  volatile unsigned long _BFAR;
  volatile unsigned long _MMAR;

  stacked_r0 = ((unsigned long)hardfault_args[0]);
  stacked_r1 = ((unsigned long)hardfault_args[1]);
  stacked_r2 = ((unsigned long)hardfault_args[2]);
  stacked_r3 = ((unsigned long)hardfault_args[3]);
  stacked_r12 = ((unsigned long)hardfault_args[4]);
  stacked_lr = ((unsigned long)hardfault_args[5]);
  stacked_pc = ((unsigned long)hardfault_args[6]);
  stacked_psr = ((unsigned long)hardfault_args[7]);

  /* Configurable Fault Status Register */
  /* Consists of MMSR, BFSR and UFSR */
  _CFSR = (*((volatile unsigned long *)(0xE000ED28)));

  /* Hard Fault Status Register */
  _HFSR = (*((volatile unsigned long *)(0xE000ED2C)));

  /* Debug Fault Status Register */
  _DFSR = (*((volatile unsigned long *)(0xE000ED30)));

  /* Auxiliary Fault Status Register */
  _AFSR = (*((volatile unsigned long *)(0xE000ED3C)));

  /* Read the Fault Address Registers. These may not contain valid values.
   * Check BFARVALID/MMARVALID to see if they are valid values
   * MemManage Fault Address Register
   */
  _MMAR = (*((volatile unsigned long *)(0xE000ED34)));
  /* Bus Fault Address Register */
  _BFAR = (*((volatile unsigned long *)(0xE000ED38)));

  /* suppress warnings about unused variables */
  (void)stacked_r0;
  (void)stacked_r1;
  (void)stacked_r2;
  (void)stacked_r3;
  (void)stacked_r12;
  (void)stacked_lr;
  (void)stacked_pc;
  (void)stacked_psr;
  (void)_CFSR;
  (void)_HFSR;
  (void)_DFSR;
  (void)_AFSR;
  (void)_BFAR;
  (void)_MMAR;

  /* Inspect stack->pc to locate the offending instruction. */
  assert_break();
}

void HardFault_Handler(void)
{
  register unsigned long *stack_pointer asm("r0");

  __asm volatile (
    " movs r0,#4      \n"  /* load bit mask into R0 */
    " movs r1, lr     \n"  /* load link register into R1 */
    " tst r0, r1      \n"  /* compare with bitmask */
    " beq _MSP        \n"  /* if bitmask is set: stack pointer is in PSP. Otherwise in MSP */
    " mrs r0, psp     \n"  /* otherwise: stack pointer is in PSP */
    " b _GetPC        \n"  /* go to part which loads the PC */
    "_MSP:            \n"  /* stack pointer is in MSP register */
    " mrs r0, msp     \n"  /* load stack pointer into R0 */
    "_GetPC:          \n"  /* find out where the hard fault happened */
    " ldr r1,[r0,#20] \n"  /* load program counter into R1. R1 contains address of the next instruction where the hard fault happened */
  );
  fault_halt(stack_pointer);
  assert_break();
}
#endif

Fault handling for Cortex-M0. Removed the branch to fault_halt inside the inline asm (and created an proper function call) so that GCC's linker won't complain. Without this, the compiler isn't smart enough when link time optimization (-flto) is enabled and compiling anything greater than -O0.