Enables OS X's hardware watchdog.

watchdog.c

#include <CoreFoundation/CoreFoundation.h>
#include <IOKit/IOKitLib.h>
#include <dispatch/dispatch.h>

// 5 minutes
#define TIMEOUT (5*60)

bool reset_watchdog (int timeout) {
    io_service_t service = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("IOWatchDogTimer"));
    if (service == IO_OBJECT_NULL) {
        fprintf(stderr, "Watching service not found\n");
        return false;
    }

    CFNumberRef number = CFNumberCreate(NULL, kCFNumberIntType, &timeout);
    kern_return_t ret;

    if ((ret = IORegistryEntrySetCFProperties(service, number)) != KERN_SUCCESS) {
        fprintf(stderr, "Failed to enable watchdog: %u\n", ret);
        IOObjectRelease(service);
        return false;
    }

    IOObjectRelease(service);
    return true;
}

void invoke_timer (void *ctx) {
    if (!reset_watchdog(TIMEOUT))
        fprintf(stderr, "Failed to reset watchdog!");
}

void handle_signal (void *ctx) {
    fprintf(stderr, "Got signal, cleaning up ...\n");
    fflush(stderr);
    if (!reset_watchdog(0)) {
        fprintf(stderr, "Failed to reset watchdog, can't exit!\n");
        return;
    }
    exit(0);
}

int main (int argc, char *argv[]) {
    /* Set up the keep-alive timer */
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());
    dispatch_source_set_timer(timer, 0, (TIMEOUT/2)*NSEC_PER_SEC, 0);
    dispatch_source_set_event_handler_f(timer, invoke_timer);
    dispatch_resume(timer);

    /* Set up the signal handlers */
    int signos[] = { SIGHUP, SIGINT, SIGQUIT, SIGILL, SIGTRAP, SIGABRT, SIGEMT, SIGFPE, SIGBUS, SIGSEGV, SIGSYS, SIGPIPE, SIGALRM, SIGTERM, SIGUSR1, SIGUSR2 };
    for (int i = 0; i < sizeof(signos) / sizeof(signos[0]); i++) {
        signal(signos[i], SIG_IGN);
        dispatch_source_t source = dispatch_source_create(DISPATCH_SOURCE_TYPE_SIGNAL, signos[i], 0, dispatch_get_main_queue());
        dispatch_source_set_event_handler_f(source, handle_signal);
        dispatch_resume(source);
    }

    dispatch_main();
    return 0;
}