root/misc/stack.c

/**
 * Example of code to catch SIGSEGV exception on
 * stack overflow. Allow to execute code whereas
 * the stack is full.
 *
 * Author: Victor Stinner
 * Creation date: 2007-04-23
 */

#include <setjmp.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>        /* printf() */
#include <sys/ucontext.h> /* ucontext_t */

jmp_buf env;                      /* try/except */
char alternate_stack[10*4096];    /* signal handler stack content */

/* SIGSEGV signal handler */
void handler(int signum)
{
    longjmp(env, 1);
}

/* create stack overflow */
void overflow(int i) {
    int r[256];
    if (i % 8 == 0) {
        printf("%p ", &r);
        if (i % 64 == 0) {
            printf("\n");
        }
        fflush(stdout);
    }
    overflow(i+1);
}

/* setup our signal stack */
void init_signal_stack()
{
  stack_t ss ;     /* signal handler stack */
  ss.ss_sp    = alternate_stack;
  ss.ss_size  = sizeof(alternate_stack);
  ss.ss_flags = 0;
  if( sigaltstack(&ss, NULL)) {
    /* error */
    fprintf(stderr, "Failed sigaltstack\n" );
    exit(1);
  }
}

/* setup our signal handler (for SIGSEGV) */
void init_signal_handler()
{
    struct sigaction newAct;
    sigemptyset(&newAct.sa_mask);
    sigaddset(&newAct.sa_mask, SIGSEGV);
    newAct.sa_handler = handler;
    newAct.sa_flags     = SA_RESETHAND | SA_RESTART | SA_ONSTACK;
    if( sigaction( SIGSEGV, &newAct, NULL ) == -1 ){
        /* error */
        fprintf(stderr, "Failed to set my signal handler.\n" );
        exit(1);
    }
}

void code()
{
    if (!setjmp(env)) {
        overflow(1);
    } else {
        /* SIGSEGV catched */
        printf("sigsegv\n");
    }
    printf("continue execution!\n");
}

int main()
{
    init_signal_stack();
    init_signal_handler();
    code();
    exit(0);
}