drivers/watchdog/softdog.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  *      SoftDog:        A Software Watchdog Device
   4  *
   5  *      (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   6  *                                                      All Rights Reserved.
   7  *
   8  *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
   9  *      warranty for any of this software. This material is provided
  10  *      "AS-IS" and at no charge.
  11  *
  12  *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
  13  *
  14  *      Software only watchdog driver. Unlike its big brother the WDT501P
  15  *      driver this won't always recover a failed machine.
  16  */
  17
  18 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  19
  20 #include <linux/hrtimer.h>
  21 #include <linux/init.h>
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/moduleparam.h>
  25 #include <linux/reboot.h>
  26 #include <linux/types.h>
  27 #include <linux/watchdog.h>
  28
  29 #define TIMER_MARGIN    60              /* Default is 60 seconds */
  30 static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
  31 module_param(soft_margin, uint, 0);
  32 MODULE_PARM_DESC(soft_margin,
  33         "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
  34                                         __MODULE_STRING(TIMER_MARGIN) ")");
  35
  36 static bool nowayout = WATCHDOG_NOWAYOUT;
  37 module_param(nowayout, bool, 0);
  38 MODULE_PARM_DESC(nowayout,
  39                 "Watchdog cannot be stopped once started (default="
  40                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  41
  42 static int soft_noboot;
  43 module_param(soft_noboot, int, 0);
  44 MODULE_PARM_DESC(soft_noboot,
  45         "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");
  46
  47 static int soft_panic;
  48 module_param(soft_panic, int, 0);
  49 MODULE_PARM_DESC(soft_panic,
  50         "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
  51
  52 static struct hrtimer softdog_ticktock;
  53 static struct hrtimer softdog_preticktock;
  54
  55 static enum hrtimer_restart softdog_fire(struct hrtimer *timer)
  56 {
  57         module_put(THIS_MODULE);
  58         if (soft_noboot) {
  59                 pr_crit("Triggered - Reboot ignored\n");
  60         } else if (soft_panic) {
  61                 pr_crit("Initiating panic\n");
  62                 panic("Software Watchdog Timer expired");
  63         } else {
  64                 pr_crit("Initiating system reboot\n");
  65                 emergency_restart();
  66                 pr_crit("Reboot didn't ?????\n");
  67         }
  68
  69         return HRTIMER_NORESTART;
  70 }
  71
  72 static struct watchdog_device softdog_dev;
  73
  74 static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer)
  75 {
  76         watchdog_notify_pretimeout(&softdog_dev);
  77
  78         return HRTIMER_NORESTART;
  79 }
  80
  81 static int softdog_ping(struct watchdog_device *w)
  82 {
  83         if (!hrtimer_active(&softdog_ticktock))
  84                 __module_get(THIS_MODULE);
  85         hrtimer_start(&softdog_ticktock, ktime_set(w->timeout, 0),
  86                       HRTIMER_MODE_REL);
  87
  88         if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
  89                 if (w->pretimeout)
  90                         hrtimer_start(&softdog_preticktock,
  91                                       ktime_set(w->timeout - w->pretimeout, 0),
  92                                       HRTIMER_MODE_REL);
  93                 else
  94                         hrtimer_cancel(&softdog_preticktock);
  95         }
  96
  97         return 0;
  98 }
  99
 100 static int softdog_stop(struct watchdog_device *w)
 101 {
 102         if (hrtimer_cancel(&softdog_ticktock))
 103                 module_put(THIS_MODULE);
 104
 105         if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT))
 106                 hrtimer_cancel(&softdog_preticktock);
 107
 108         return 0;
 109 }
 110
 111 static struct watchdog_info softdog_info = {
 112         .identity = "Software Watchdog",
 113         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 114 };
 115
 116 static const struct watchdog_ops softdog_ops = {
 117         .owner = THIS_MODULE,
 118         .start = softdog_ping,
 119         .stop = softdog_stop,
 120 };
 121
 122 static struct watchdog_device softdog_dev = {
 123         .info = &softdog_info,
 124         .ops = &softdog_ops,
 125         .min_timeout = 1,
 126         .max_timeout = 65535,
 127         .timeout = TIMER_MARGIN,
 128 };
 129
 130 static int __init softdog_init(void)
 131 {
 132         int ret;
 133
 134         watchdog_init_timeout(&softdog_dev, soft_margin, NULL);
 135         watchdog_set_nowayout(&softdog_dev, nowayout);
 136         watchdog_stop_on_reboot(&softdog_dev);
 137
 138         hrtimer_init(&softdog_ticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 139         softdog_ticktock.function = softdog_fire;
 140
 141         if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
 142                 softdog_info.options |= WDIOF_PRETIMEOUT;
 143                 hrtimer_init(&softdog_preticktock, CLOCK_MONOTONIC,
 144                              HRTIMER_MODE_REL);
 145                 softdog_preticktock.function = softdog_pretimeout;
 146         }
 147
 148         ret = watchdog_register_device(&softdog_dev);
 149         if (ret)
 150                 return ret;
 151
 152         pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
 153                 soft_noboot, softdog_dev.timeout, soft_panic, nowayout);
 154
 155         return 0;
 156 }
 157 module_init(softdog_init);
 158
 159 static void __exit softdog_exit(void)
 160 {
 161         watchdog_unregister_device(&softdog_dev);
 162 }
 163 module_exit(softdog_exit);
 164
 165 MODULE_AUTHOR("Alan Cox");
 166 MODULE_DESCRIPTION("Software Watchdog Device Driver");
 167 MODULE_LICENSE("GPL");