signalstack.c

sigaltstack.c (text/plain), 2.24 KB, created by Alon Bar-Lev (RETIRED) on 2014-10-26 08:13:09 UTC

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <signal.h>
#include <unistd.h>
#define HAVE_STACK_T 1
union alltypes {
    long   l;
    double d;
    void  *vp;
    void (*fp)(void);
    char  *cp;
};
static volatile char *handler_addr = (char *)0xDEAD;
static volatile int handler_done = 0;
void handler(int sig)
{
    char garbage[1024];
    int i;
    auto int dummy;
    for (i = 0; i < 1024; i++)
        garbage[i] = 'X';
    handler_addr = (char *)&dummy;
    handler_done = 1;
    return;
}
int main(int argc, char *argv[])
{
    FILE *f;
    char *skaddr;
    char *skbuf;
    int sksize;
    char result[1024];
    int i;
    sksize = 32768;
    skbuf = (char *)malloc(sksize*2+2*sizeof(union alltypes));
    if (skbuf == NULL)
        exit(1);
    for (i = 0; i < sksize*2+2*sizeof(union alltypes); i++)
        skbuf[i] = 'A';
    skaddr = skbuf+sizeof(union alltypes);
    {
        struct sigaction sa;
#if defined(HAVE_STACK_T)
        stack_t ss;
#else
        struct sigaltstack ss;
#endif
        ss.ss_sp    = (void *)(skaddr + sksize);
        ss.ss_size  = sksize;
        ss.ss_flags = 0;
        if (sigaltstack(&ss, NULL) < 0)
            exit(1);
        memset((void *)&sa, 0, sizeof(struct sigaction));
        sa.sa_handler = handler;
        sa.sa_flags = SA_ONSTACK;
        sigemptyset(&sa.sa_mask);
        sigaction(SIGUSR1, &sa, NULL);
        kill(getpid(), SIGUSR1);
        while (!handler_done)
            /*nop*/;
    }
    if (handler_addr == (char *)0xDEAD)
        exit(1);
    if (handler_addr < skaddr+sksize) {
        /* stack was placed into lower area */
        if (*(skaddr+sksize) != 'A')
             sprintf(result, "(skaddr)+(sksize)-%d,(sksize)-%d",
                     sizeof(union alltypes), sizeof(union alltypes));
        else
             strcpy(result, "(skaddr)+(sksize),(sksize)");
    }
    else {
        /* stack was placed into higher area */
        if (*(skaddr+sksize*2) != 'A')
            sprintf(result, "(skaddr),(sksize)-%d", sizeof(union alltypes));
        else
            strcpy(result, "(skaddr),(sksize)");
    }
/*
    if ((f = fopen("conftestval", "w")) == NULL)
        exit(1);
*/
f = stdout;
    fprintf(f, "%s\n", result);
/*    fclose(f); */
    exit(0);
}