I handle SIGSEGV by code:
int C()
{
int *i = NULL;
*i = 10; // Crash there
}
int B()
{
return C();
}
int A()
{
return B();
}
int main(void)
{
struct sigaction handler;
memset(&handler,0,sizeof(handler));
handler.sa_sigaction = handler_func;
handler.sa_flags = SA_SIGINFO;
sigaction(SIGSEGV,&handler,NULL);
return(C());
}
Where handler code are:
static int handler_func(int signal, siginfo_t info, void* rserved)
{
const void* stack[MAX_DEPTH];
StackCrowlState state;
state.addr = stack;
state.count = MAX_DEPTH;
_Unwind_Reason_Code code = _Unwind_Backtrace(trace_func,&state);
printf("Stack trace count: %d, code: %d\n",MAX_DEPTH - state.count, code);
kill(getpid(),SIGKILL);
}
static _Unwind_Reason_Code trace_func(void* context, void* arg)
{
StackCrowlState *state = (StackCrowlState *)arg;
if(state->count>0)
{
void *ip = (void *)_Unwind_GetIP(context);
if(ip)
{
state->addr[0] = ip;
state->count--;
state->addr++;
}
}
return(_URC_NO_REASON);
}
But trace_func where called only once, and shows only on _Unwind_Backtrace calls. Is it possible to get stacktrace of code which cause SIGSEGV signal using _Unwind_Backtrace?
thnx
You want to backtrace from the signal triggering function, but you backtrace from the signal handler function. That's two different stacks. (Note, the SA_ONSTACK flag in sigaction is irrelevant to your question.)
To find the stack pointer of the of the triggering function, use the third parameter of the handler, i.e. void *rserved. You can reference to the answer in this question: Getting the saved instruction pointer address from a signal handler