/*      $OpenBSD: sigaltstack_fork.c,v 1.2 2011/11/26 04:11:34 guenther Exp $   */

/*
 * Public domain.  2011, Joshua Elsasser
 *
 * Test if child processes inherit an alternate signal stack.
 */

#include <sys/types.h>
#include <sys/wait.h>

#include <err.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

void
check_stack(void *buf, const char *label)
{
        struct sigaltstack ss;

        bzero(&ss, sizeof(ss));
        if (sigaltstack(NULL, &ss) != 0)
                err(1, "failed to get sigaltstack in %s", label);
        if (ss.ss_sp != buf ||
            ss.ss_size != SIGSTKSZ ||
            ss.ss_flags != 0)
                errx(1, "bad sigaltstack value in %s: "
                    "buf=%p ss_sp=%p ss_size=%zu ss_flags=0x%x",
                    label, buf, ss.ss_sp, ss.ss_size, ss.ss_flags);
}

int
main(int argc, char *argv[])
{
        struct sigaltstack ss;
        int status;
        pid_t kid;
        void *buf;

        if ((buf = malloc(SIGSTKSZ)) == NULL)
                err(1, "malloc failed");

        bzero(&ss, sizeof(ss));
        ss.ss_sp = buf;
        ss.ss_size = SIGSTKSZ;
        if (sigaltstack(&ss, NULL) != 0)
                err(1, "failed to set sigaltstack");

        check_stack(buf, "parent");

        if ((kid = fork()) == -1)
                err(1, "fork failed");

        if (kid == 0) {
                check_stack(buf, "child");
                _exit(0);
        }

        if (waitpid(kid, &status, 0) != kid)
                err(1, "waitpid failed");
        if (!WIFEXITED(status))
                errx(1, "child did not exit normally");

        return (WEXITSTATUS(status));
}