When working on Cortex-M4 platform, an exception which has not been expected (an interrupt without ISR, an access to an illegal address, etc).
The code below shows how to implement it.
static void expt_frm_dump(pointer ext_frm_ptr)
{
static char *expt_name[] = {
"None",
"Reset",
"NMI",
"HardFault",
"MemManage",
"BusFault",
"UsageFault",
"Rsvd",
"Rsvd",
"Rsvd",
"SVCall",
"Debug Monitor",
"Rsvd",
"PendSV",
"SysTick"
};
uint_32 excpt_num = __get_PSR() & 0x1FF;
printf("Opps, bad thing happened.\n");
if(excpt_num < 16){
printf("The exception [%s] invoked in TASK 0x%x\n",
expt_name[excpt_num] , _task_get_id());
printf("Dump the exception frame as :\n");
printf("R0:\t0x%08x\n", *((uint_32 *)ext_frm_ptr));
printf("R1:\t0x%08x\n", *((uint_32 *)ext_frm_ptr + 1));
printf("R2:\t0x%08x\n", *((uint_32 *)ext_frm_ptr + 2));
printf("R3:\t0x%08x\n", *((uint_32 *)ext_frm_ptr + 3));
printf("R12:\t0x%08x\n", *((uint_32 *)ext_frm_ptr + 4));
printf("LR:\t0x%08x\n", *((uint_32 *)ext_frm_ptr + 5));
printf("PC:\t0x%08x\n", *((uint_32 *)ext_frm_ptr + 6));
printf("PSR:\t0x%08x\n", *((uint_32 *)ext_frm_ptr + 7));
}else{
printf("The external interrupt %d occured while no handler to serve it.\n");
}
}
void task_exception_handler(_mqx_uint para, pointer stack_ptr)
{
pointer expt_frm_ptr = (pointer)__get_PSP();
expt_frm_dump(expt_frm_ptr);
}
void test_task(unsigned long para)
{
unsigned int *p_bad = (unsigned int *)0;
printf("Install the _int_exception_isr to replace the _int_default_isr\n");
_int_install_exception_isr();
/* Set the exception handler of the task */
_task_set_exception_handler(_task_get_id(), task_exception_handler);
*p_bad = 0; // an access to address 0
_task_block();
}