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 (5.3 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
shutdown_watchdog(void)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
shutdown_on_signal(int sig UNUSED_PARAM)75 static void shutdown_on_signal(int sig UNUSED_PARAM)
76 {
77 remove_pidfile_std_path_and_ext("watchdog");
78 shutdown_watchdog();
79 _exit(EXIT_SUCCESS);
80 }
81
watchdog_open(const char * device)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;
watchdog_main(int argc UNUSED_PARAM,char ** argv)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 }
166