miscutils/watchdog.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Mini watchdog implementation for busybox
   4  *
   5  * Copyright (C) 2003  Paul Mundt <lethal@linux-sh.org>
   6  * Copyright (C) 2006  Bernhard Reutner-Fischer <busybox@busybox.net>
   7  * Copyright (C) 2008  Darius Augulis <augulis.darius@gmail.com>
   8  *
   9  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  10  */
  11 //config:config WATCHDOG
  12 //config:       bool "watchdog (5.7 kb)"
  13 //config:       default y
  14 //config:       help
  15 //config:       The watchdog utility is used with hardware or software watchdog
  16 //config:       device drivers. It opens the specified watchdog device special file
  17 //config:       and periodically writes a magic character to the device. If the
  18 //config:       watchdog applet ever fails to write the magic character within a
  19 //config:       certain amount of time, the watchdog device assumes the system has
  20 //config:       hung, and will cause the hardware to reboot.
  21 //config:
  22 //config:config FEATURE_WATCHDOG_OPEN_TWICE
  23 //config:       bool "Open watchdog device twice, closing it gracefully in between"
  24 //config:       depends on WATCHDOG
  25 //config:       default n   # this behavior was essentially a hack for a broken driver
  26 //config:       help
  27 //config:       When enabled, the watchdog device is opened and then immediately
  28 //config:       magic-closed, before being opened a second time. This may be necessary
  29 //config:       for some watchdog devices, but can cause spurious warnings in the
  30 //config:       kernel log if the nowayout feature is enabled. If this workaround
  31 //config:       is really needed for you machine to work properly, consider whether
  32 //config:       it should be fixed in the kernel driver instead. Even when disabled,
  33 //config:       the behaviour is easily emulated with a "printf 'V' > /dev/watchdog"
  34 //config:       immediately before starting the busybox watchdog daemon. Say n unless
  35 //config:       you know that you absolutely need this.
  36
  37 //applet:IF_WATCHDOG(APPLET(watchdog, BB_DIR_SBIN, BB_SUID_DROP))
  38
  39 //kbuild:lib-$(CONFIG_WATCHDOG) += watchdog.o
  40
  41 //usage:#define watchdog_trivial_usage
  42 //usage:       "[-t N[ms]] [-T N[ms]] [-F] DEV"
  43 //usage:#define watchdog_full_usage "\n\n"
  44 //usage:       "Periodically write to watchdog device DEV\n"
  45 //usage:     "\n        -T N    Reboot after N seconds if not reset (default 60)"
  46 //usage:     "\n        -t N    Reset every N seconds (default 30)"
  47 //usage:     "\n        -F      Run in foreground"
  48 //usage:     "\n"
  49 //usage:     "\nUse 500ms to specify period in milliseconds"
  50
  51 #include "libbb.h"
  52 #include <linux/types.h> /* for __u32 */
  53 #include <linux/watchdog.h>
  54
  55 #ifndef WDIOC_SETOPTIONS
  56 # define WDIOC_SETOPTIONS 0x5704
  57 #endif
  58 #ifndef WDIOC_SETTIMEOUT
  59 # define WDIOC_SETTIMEOUT 0x5706
  60 #endif
  61 #ifndef WDIOC_GETTIMEOUT
  62 # define WDIOC_GETTIMEOUT 0x5707
  63 #endif
  64 #ifndef WDIOS_ENABLECARD
  65 # define WDIOS_ENABLECARD 2
  66 #endif
  67
  68 static void shutdown_watchdog(void)
  69 {
  70         static const char V = 'V';
  71         write(3, &V, 1);  /* Magic, see watchdog-api.txt in kernel */
  72         close(3);
  73 }
  74
  75 static void shutdown_on_signal(int sig UNUSED_PARAM)
  76 {
  77         remove_pidfile_std_path_and_ext("watchdog");
  78         shutdown_watchdog();
  79         _exit_SUCCESS();
  80 }
  81
  82 static void watchdog_open(const char* device)
  83 {
  84         /* Use known fd # - avoid needing global 'int fd' */
  85         xmove_fd(xopen(device, O_WRONLY), 3);
  86
  87 #if ENABLE_FEATURE_WATCHDOG_OPEN_TWICE
  88         /* If the watchdog driver can do something other than cause a reboot
  89          * on a timeout, then it's possible this program may be starting from
  90          * a state when the watchdog hadn't been previously stopped with
  91          * the magic write followed by a close.  In this case the driver may
  92          * not start properly, so always do the proper stop first just in case.
  93          */
  94         shutdown_watchdog();
  95
  96         xmove_fd(xopen(device, O_WRONLY), 3);
  97 #endif
  98 }
  99
 100 int watchdog_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 101 int watchdog_main(int argc UNUSED_PARAM, char **argv)
 102 {
 103         static const int enable = WDIOS_ENABLECARD;
 104         static const struct suffix_mult suffixes[] ALIGN_SUFFIX = {
 105                 { "ms", 1 },
 106                 { "", 1000 },
 107                 { "", 0 }
 108         };
 109
 110         unsigned opts;
 111         unsigned stimer_duration; /* how often to restart */
 112         unsigned htimer_duration = 60000; /* reboots after N ms if not restarted */
 113         char *st_arg;
 114         char *ht_arg;
 115
 116 #define OPT_FOREGROUND  (1 << 0)
 117 #define OPT_STIMER      (1 << 1)
 118 #define OPT_HTIMER      (1 << 2)
 119         opts = getopt32(argv, "^" "Ft:T:" "\0" "=1"/*must have exactly 1 arg*/,
 120                                 &st_arg, &ht_arg
 121         );
 122
 123         /* We need to daemonize *before* opening the watchdog as many drivers
 124          * will only allow one process at a time to do so.  Since daemonizing
 125          * is not perfect (child may run before parent finishes exiting), we
 126          * can't rely on parent exiting before us (let alone *cleanly* releasing
 127          * the watchdog fd -- something else that may not even be allowed).
 128          */
 129         if (!(opts & OPT_FOREGROUND))
 130                 bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
 131
 132         /* maybe bb_logenv_override(); here for LOGGING=syslog to work? */
 133
 134         if (opts & OPT_HTIMER)
 135                 htimer_duration = xatou_sfx(ht_arg, suffixes);
 136         stimer_duration = htimer_duration / 2;
 137         if (opts & OPT_STIMER)
 138                 stimer_duration = xatou_sfx(st_arg, suffixes);
 139
 140         bb_signals(BB_FATAL_SIGS, shutdown_on_signal);
 141
 142         watchdog_open(argv[optind]);
 143
 144         /* WDIOC_SETTIMEOUT takes seconds, not milliseconds */
 145         htimer_duration = htimer_duration / 1000;
 146         ioctl_or_warn(3, WDIOC_SETOPTIONS, (void*) &enable);
 147         ioctl_or_warn(3, WDIOC_SETTIMEOUT, &htimer_duration);
 148 #if 0
 149         ioctl_or_warn(3, WDIOC_GETTIMEOUT, &htimer_duration);
 150         printf("watchdog: SW timer is %dms, HW timer is %ds\n",
 151                 stimer_duration, htimer_duration);
 152 #endif
 153
 154         write_pidfile_std_path_and_ext("watchdog");
 155
 156         while (1) {
 157                 /*
 158                  * Make sure we clear the counter before sleeping,
 159                  * as the counter value is undefined at this point -- PFM
 160                  */
 161                 write(3, "", 1); /* write zero byte */
 162                 msleep(stimer_duration);
 163         }
 164         return EXIT_SUCCESS; /* - not reached, but gcc 4.2.1 is too dumb! */
 165 }