signalstack.c

#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>

static void sigseg_handler(int sig)
{
	int x;
	printf ("Caught signal %d (%s)\n", sig, strsignal(sig));
	printf ("Top of handler stack near %10p\n", (void *)&x);
	fflush(NULL);

	_exit(EXIT_FAILURE);
}

static void overflow_stack(int call_num)
{
	char a[1000000]; //The larger the a[] stack used, the faster it caused stack overflow 

	printf ("Call %4d - top of stack near %10p\n", call_num, &a[0]);

	overflow_stack(call_num + 1);
}

int main(int argc, char *argv[])
{
	stack_t sigstack;
	struct sigaction sa;
	int j;

	printf ("Top of standard stack is near %10p\n", (void *)&j);

	sigstack.ss_sp = malloc(SIGSTKSZ);
	if (sigstack.ss_sp == NULL) {
		perror ("malloc");
		exit (EXIT_FAILURE);
	}
	sigstack.ss_size = SIGSTKSZ;
	sigstack.ss_flags = 0;
	if (sigaltstack(&sigstack, NULL) == -1) {
		perror ("sigaltstack");
		exit (EXIT_FAILURE);
	}
	printf ("Alternate stack is at    %10p-%p\n", sigstack.ss_sp, (char *)sbrk(0) - 1);

	sa.sa_handler = sigseg_handler;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_ONSTACK;
	if (sigaction(SIGSEGV, &sa, NULL) == -1) {
		perror("sigaction");
		exit(EXIT_FAILURE);
	}

	overflow_stack(1);
}