blob: 86600b72fc3f67f31fa415d9489cda66803bdbaf [file] [log] [blame]
/* vi: set sw=4 ts=4: */
* Mini watchdog implementation for busybox
* Copyright (C) 2003 Paul Mundt <>
* Copyright (C) 2006 Bernhard Reutner-Fischer <>
* Copyright (C) 2008 Darius Augulis <>
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
//config:config WATCHDOG
//config: bool "watchdog (5.3 kb)"
//config: default y
//config: select PLATFORM_LINUX
//config: help
//config: The watchdog utility is used with hardware or software watchdog
//config: device drivers. It opens the specified watchdog device special file
//config: and periodically writes a magic character to the device. If the
//config: watchdog applet ever fails to write the magic character within a
//config: certain amount of time, the watchdog device assumes the system has
//config: hung, and will cause the hardware to reboot.
//kbuild:lib-$(CONFIG_WATCHDOG) += watchdog.o
//usage:#define watchdog_trivial_usage
//usage: "[-t N[ms]] [-T N[ms]] [-F] DEV"
//usage:#define watchdog_full_usage "\n\n"
//usage: "Periodically write to watchdog device DEV\n"
//usage: "\n -T N Reboot after N seconds if not reset (default 60)"
//usage: "\n -t N Reset every N seconds (default 30)"
//usage: "\n -F Run in foreground"
//usage: "\n"
//usage: "\nUse 500ms to specify period in milliseconds"
#include "libbb.h"
#include <linux/types.h> /* for __u32 */
#include <linux/watchdog.h>
# define WDIOC_SETOPTIONS 0x5704
# define WDIOC_SETTIMEOUT 0x5706
# define WDIOC_GETTIMEOUT 0x5707
#define OPT_FOREGROUND (1 << 0)
#define OPT_STIMER (1 << 1)
#define OPT_HTIMER (1 << 2)
static void shutdown_watchdog(void)
static const char V = 'V';
write(3, &V, 1); /* Magic, see watchdog-api.txt in kernel */
static void shutdown_on_signal(int sig UNUSED_PARAM)
static void watchdog_open(const char* device)
/* Use known fd # - avoid needing global 'int fd' */
xmove_fd(xopen(device, O_WRONLY), 3);
/* If the watchdog driver can do something other than cause a reboot
* on a timeout, then it's possible this program may be starting from
* a state when the watchdog hadn't been previously stopped with
* the magic write followed by a close. In this case the driver may
* not start properly, so always do the proper stop first just in case.
xmove_fd(xopen(device, O_WRONLY), 3);
int watchdog_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int watchdog_main(int argc UNUSED_PARAM, char **argv)
static const int enable = WDIOS_ENABLECARD;
static const struct suffix_mult suffixes[] = {
{ "ms", 1 },
{ "", 1000 },
{ "", 0 }
unsigned opts;
unsigned stimer_duration; /* how often to restart */
unsigned htimer_duration = 60000; /* reboots after N ms if not restarted */
char *st_arg;
char *ht_arg;
opts = getopt32(argv, "^" "Ft:T:" "\0" "=1"/*must have exactly 1 arg*/,
&st_arg, &ht_arg
/* We need to daemonize *before* opening the watchdog as many drivers
* will only allow one process at a time to do so. Since daemonizing
* is not perfect (child may run before parent finishes exiting), we
* can't rely on parent exiting before us (let alone *cleanly* releasing
* the watchdog fd -- something else that may not even be allowed).
if (!(opts & OPT_FOREGROUND))
bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
/* maybe bb_logenv_override(); here for LOGGING=syslog to work? */
if (opts & OPT_HTIMER)
htimer_duration = xatou_sfx(ht_arg, suffixes);
stimer_duration = htimer_duration / 2;
if (opts & OPT_STIMER)
stimer_duration = xatou_sfx(st_arg, suffixes);
bb_signals(BB_FATAL_SIGS, shutdown_on_signal);
/* WDIOC_SETTIMEOUT takes seconds, not milliseconds */
htimer_duration = htimer_duration / 1000;
ioctl_or_warn(3, WDIOC_SETOPTIONS, (void*) &enable);
ioctl_or_warn(3, WDIOC_SETTIMEOUT, &htimer_duration);
#if 0
ioctl_or_warn(3, WDIOC_GETTIMEOUT, &htimer_duration);
printf("watchdog: SW timer is %dms, HW timer is %ds\n",
stimer_duration, htimer_duration * 1000);
while (1) {
* Make sure we clear the counter before sleeping,
* as the counter value is undefined at this point -- PFM
write(3, "", 1); /* write zero byte */
usleep(stimer_duration * 1000L);
return EXIT_SUCCESS; /* - not reached, but gcc 4.2.1 is too dumb! */