drivers/watchdog/softdog.c

   1 /*
   2  *      SoftDog 0.07:   A Software Watchdog Device
   3  *
   4  *      (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   5  *                                                      All Rights Reserved.
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  *
  12  *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
  13  *      warranty for any of this software. This material is provided
  14  *      "AS-IS" and at no charge.
  15  *
  16  *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
  17  *
  18  *      Software only watchdog driver. Unlike its big brother the WDT501P
  19  *      driver this won't always recover a failed machine.
  20  *
  21  *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
  22  *      Modularised.
  23  *      Added soft_margin; use upon insmod to change the timer delay.
  24  *      NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
  25  *          minors.
  26  *
  27  *  19980911 Alan Cox
  28  *      Made SMP safe for 2.3.x
  29  *
  30  *  20011127 Joel Becker (jlbec@evilplan.org>
  31  *      Added soft_noboot; Allows testing the softdog trigger without
  32  *      requiring a recompile.
  33  *      Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
  34  *
  35  *  20020530 Joel Becker <joel.becker@oracle.com>
  36  *      Added Matt Domsch's nowayout module option.
  37  */
  38
  39 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  40
  41 #include <linux/module.h>
  42 #include <linux/moduleparam.h>
  43 #include <linux/types.h>
  44 #include <linux/timer.h>
  45 #include <linux/miscdevice.h>
  46 #include <linux/watchdog.h>
  47 #include <linux/fs.h>
  48 #include <linux/notifier.h>
  49 #include <linux/reboot.h>
  50 #include <linux/init.h>
  51 #include <linux/jiffies.h>
  52 #include <linux/uaccess.h>
  53 #include <linux/kernel.h>
  54
  55 #define TIMER_MARGIN    60              /* Default is 60 seconds */
  56 static int soft_margin = TIMER_MARGIN;  /* in seconds */
  57 module_param(soft_margin, int, 0);
  58 MODULE_PARM_DESC(soft_margin,
  59         "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
  60                                         __MODULE_STRING(TIMER_MARGIN) ")");
  61
  62 static bool nowayout = WATCHDOG_NOWAYOUT;
  63 module_param(nowayout, bool, 0);
  64 MODULE_PARM_DESC(nowayout,
  65                 "Watchdog cannot be stopped once started (default="
  66                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  67
  68 #ifdef ONLY_TESTING
  69 static int soft_noboot = 1;
  70 #else
  71 static int soft_noboot = 0;
  72 #endif  /* ONLY_TESTING */
  73
  74 module_param(soft_noboot, int, 0);
  75 MODULE_PARM_DESC(soft_noboot,
  76         "Softdog action, set to 1 to ignore reboots, 0 to reboot "
  77                                         "(default depends on ONLY_TESTING)");
  78
  79 static int soft_panic;
  80 module_param(soft_panic, int, 0);
  81 MODULE_PARM_DESC(soft_panic,
  82         "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
  83
  84 /*
  85  *      Our timer
  86  */
  87
  88 static void watchdog_fire(unsigned long);
  89
  90 static struct timer_list watchdog_ticktock =
  91                 TIMER_INITIALIZER(watchdog_fire, 0, 0);
  92 static unsigned long driver_open, orphan_timer;
  93 static char expect_close;
  94
  95
  96 /*
  97  *      If the timer expires..
  98  */
  99
 100 static void watchdog_fire(unsigned long data)
 101 {
 102         if (test_and_clear_bit(0, &orphan_timer))
 103                 module_put(THIS_MODULE);
 104
 105         if (soft_noboot)
 106                 pr_crit("Triggered - Reboot ignored\n");
 107         else if (soft_panic) {
 108                 pr_crit("Initiating panic\n");
 109                 panic("Software Watchdog Timer expired");
 110         } else {
 111                 pr_crit("Initiating system reboot\n");
 112                 emergency_restart();
 113                 pr_crit("Reboot didn't ?????\n");
 114         }
 115 }
 116
 117 /*
 118  *      Softdog operations
 119  */
 120
 121 static int softdog_keepalive(void)
 122 {
 123         mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
 124         return 0;
 125 }
 126
 127 static int softdog_stop(void)
 128 {
 129         del_timer(&watchdog_ticktock);
 130         return 0;
 131 }
 132
 133 static int softdog_set_heartbeat(int t)
 134 {
 135         if ((t < 0x0001) || (t > 0xFFFF))
 136                 return -EINVAL;
 137
 138         soft_margin = t;
 139         return 0;
 140 }
 141
 142 /*
 143  *      /dev/watchdog handling
 144  */
 145
 146 static int softdog_open(struct inode *inode, struct file *file)
 147 {
 148         if (test_and_set_bit(0, &driver_open))
 149                 return -EBUSY;
 150         if (!test_and_clear_bit(0, &orphan_timer))
 151                 __module_get(THIS_MODULE);
 152         /*
 153          *      Activate timer
 154          */
 155         softdog_keepalive();
 156         return nonseekable_open(inode, file);
 157 }
 158
 159 static int softdog_release(struct inode *inode, struct file *file)
 160 {
 161         /*
 162          *      Shut off the timer.
 163          *      Lock it in if it's a module and we set nowayout
 164          */
 165         if (expect_close == 42) {
 166                 softdog_stop();
 167                 module_put(THIS_MODULE);
 168         } else {
 169                 pr_crit("Unexpected close, not stopping watchdog!\n");
 170                 set_bit(0, &orphan_timer);
 171                 softdog_keepalive();
 172         }
 173         clear_bit(0, &driver_open);
 174         expect_close = 0;
 175         return 0;
 176 }
 177
 178 static ssize_t softdog_write(struct file *file, const char __user *data,
 179                                                 size_t len, loff_t *ppos)
 180 {
 181         /*
 182          *      Refresh the timer.
 183          */
 184         if (len) {
 185                 if (!nowayout) {
 186                         size_t i;
 187
 188                         /* In case it was set long ago */
 189                         expect_close = 0;
 190
 191                         for (i = 0; i != len; i++) {
 192                                 char c;
 193
 194                                 if (get_user(c, data + i))
 195                                         return -EFAULT;
 196                                 if (c == 'V')
 197                                         expect_close = 42;
 198                         }
 199                 }
 200                 softdog_keepalive();
 201         }
 202         return len;
 203 }
 204
 205 static long softdog_ioctl(struct file *file, unsigned int cmd,
 206                                                         unsigned long arg)
 207 {
 208         void __user *argp = (void __user *)arg;
 209         int __user *p = argp;
 210         int new_margin;
 211         static const struct watchdog_info ident = {
 212                 .options =              WDIOF_SETTIMEOUT |
 213                                         WDIOF_KEEPALIVEPING |
 214                                         WDIOF_MAGICCLOSE,
 215                 .firmware_version =     0,
 216                 .identity =             "Software Watchdog",
 217         };
 218         switch (cmd) {
 219         case WDIOC_GETSUPPORT:
 220                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 221         case WDIOC_GETSTATUS:
 222         case WDIOC_GETBOOTSTATUS:
 223                 return put_user(0, p);
 224         case WDIOC_KEEPALIVE:
 225                 softdog_keepalive();
 226                 return 0;
 227         case WDIOC_SETTIMEOUT:
 228                 if (get_user(new_margin, p))
 229                         return -EFAULT;
 230                 if (softdog_set_heartbeat(new_margin))
 231                         return -EINVAL;
 232                 softdog_keepalive();
 233                 /* Fall */
 234         case WDIOC_GETTIMEOUT:
 235                 return put_user(soft_margin, p);
 236         default:
 237                 return -ENOTTY;
 238         }
 239 }
 240
 241 /*
 242  *      Notifier for system down
 243  */
 244
 245 static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
 246         void *unused)
 247 {
 248         if (code == SYS_DOWN || code == SYS_HALT)
 249                 /* Turn the WDT off */
 250                 softdog_stop();
 251         return NOTIFY_DONE;
 252 }
 253
 254 /*
 255  *      Kernel Interfaces
 256  */
 257
 258 static const struct file_operations softdog_fops = {
 259         .owner          = THIS_MODULE,
 260         .llseek         = no_llseek,
 261         .write          = softdog_write,
 262         .unlocked_ioctl = softdog_ioctl,
 263         .open           = softdog_open,
 264         .release        = softdog_release,
 265 };
 266
 267 static struct miscdevice softdog_miscdev = {
 268         .minor          = WATCHDOG_MINOR,
 269         .name           = "watchdog",
 270         .fops           = &softdog_fops,
 271 };
 272
 273 static struct notifier_block softdog_notifier = {
 274         .notifier_call  = softdog_notify_sys,
 275 };
 276
 277 static int __init watchdog_init(void)
 278 {
 279         int ret;
 280
 281         /* Check that the soft_margin value is within it's range;
 282            if not reset to the default */
 283         if (softdog_set_heartbeat(soft_margin)) {
 284                 softdog_set_heartbeat(TIMER_MARGIN);
 285                 pr_info("soft_margin must be 0 < soft_margin < 65536, using %d\n",
 286                         TIMER_MARGIN);
 287         }
 288
 289         ret = register_reboot_notifier(&softdog_notifier);
 290         if (ret) {
 291                 pr_err("cannot register reboot notifier (err=%d)\n", ret);
 292                 return ret;
 293         }
 294
 295         ret = misc_register(&softdog_miscdev);
 296         if (ret) {
 297                 pr_err("cannot register miscdev on minor=%d (err=%d)\n",
 298                        WATCHDOG_MINOR, ret);
 299                 unregister_reboot_notifier(&softdog_notifier);
 300                 return ret;
 301         }
 302
 303         pr_info("Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout= %d)\n",
 304                 soft_noboot, soft_margin, soft_panic, nowayout);
 305
 306         return 0;
 307 }
 308
 309 static void __exit watchdog_exit(void)
 310 {
 311         misc_deregister(&softdog_miscdev);
 312         unregister_reboot_notifier(&softdog_notifier);
 313 }
 314
 315 module_init(watchdog_init);
 316 module_exit(watchdog_exit);
 317
 318 MODULE_AUTHOR("Alan Cox");
 319 MODULE_DESCRIPTION("Software Watchdog Device Driver");
 320 MODULE_LICENSE("GPL");
 321 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);