busybox/miscutils/watchdog.c

/* vi: set sw=4 ts=4: */
/*
 * Mini watchdog implementation for busybox
 *
 * Copyright (C) 2003  Paul Mundt <lethal@linux-sh.org>
 * Copyright (C) 2006  Bernhard Fischer <busybox@busybox.net>
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */

#include "busybox.h"

#define OPT_FOREGROUND 0x01
#define OPT_TIMER      0x02

static void watchdog_shutdown(int ATTRIBUTE_UNUSED sig) ATTRIBUTE_NORETURN;
static void watchdog_shutdown(int ATTRIBUTE_UNUSED sig)
{
	write(3, "V", 1);	/* Magic, see watchdog-api.txt in kernel */
	if (ENABLE_FEATURE_CLEAN_UP)
		close(3);
	exit(0);
}

int watchdog_main(int argc, char **argv);
int watchdog_main(int argc, char **argv)
{
	unsigned opts;
	unsigned timer_duration = 30; /* Userspace timer duration, in seconds */
	char *t_arg;

	opts = getopt32(argc, argv, "Ft:", &t_arg);

	if (opts & OPT_TIMER)
		timer_duration = xatou(t_arg);

	/* We're only interested in the watchdog device .. */
	if (optind < argc - 1 || argc == 1)
		bb_show_usage();

	if (!(opts & OPT_FOREGROUND)) {
#ifdef BB_NOMMU
		if (!re_execed)
			vfork_daemon_rexec(0, 1, argv);
#else
		xdaemon(0, 1);
#endif
	}

	signal(SIGHUP, watchdog_shutdown);
	signal(SIGINT, watchdog_shutdown);

	/* Use known fd # - avoid needing global 'int fd' */
	dup2(xopen(argv[argc - 1], O_WRONLY), 3);

	while (1) {
		/*
		 * Make sure we clear the counter before sleeping, as the counter value
		 * is undefined at this point -- PFM
		 */
		write(3, "", 1);
		sleep(timer_duration);
	}

	watchdog_shutdown(0);

	/* return EXIT_SUCCESS; */
}