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 #include <linux/module.h>
  40 #include <linux/moduleparam.h>
  41 #include <linux/types.h>
  42 #include <linux/timer.h>
  43 #include <linux/miscdevice.h>
  44 #include <linux/watchdog.h>
  45 #include <linux/fs.h>
  46 #include <linux/notifier.h>
  47 #include <linux/reboot.h>
  48 #include <linux/init.h>
  49 #include <linux/jiffies.h>
  50 #include <linux/uaccess.h>
  51
  52 #define PFX "SoftDog: "
  53
  54 #define TIMER_MARGIN    60              /* Default is 60 seconds */
  55 static int soft_margin = TIMER_MARGIN;  /* in seconds */
  56 module_param(soft_margin, int, 0);
  57 MODULE_PARM_DESC(soft_margin,
  58         "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
  59                                         __MODULE_STRING(TIMER_MARGIN) ")");
  60
  61 static int nowayout = WATCHDOG_NOWAYOUT;
  62 module_param(nowayout, int, 0);
  63 MODULE_PARM_DESC(nowayout,
  64                 "Watchdog cannot be stopped once started (default="
  65                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  66
  67 #ifdef ONLY_TESTING
  68 static int soft_noboot = 1;
  69 #else
  70 static int soft_noboot = 0;
  71 #endif  /* ONLY_TESTING */
  72
  73 module_param(soft_noboot, int, 0);
  74 MODULE_PARM_DESC(soft_noboot,
  75         "Softdog action, set to 1 to ignore reboots, 0 to reboot "
  76                                         "(default depends on ONLY_TESTING)");
  77
  78 /*
  79  *      Our timer
  80  */
  81
  82 static void watchdog_fire(unsigned long);
  83
  84 static struct timer_list watchdog_ticktock =
  85                 TIMER_INITIALIZER(watchdog_fire, 0, 0);
  86 static unsigned long driver_open, orphan_timer;
  87 static char expect_close;
  88
  89
  90 /*
  91  *      If the timer expires..
  92  */
  93
  94 static void watchdog_fire(unsigned long data)
  95 {
  96         if (test_and_clear_bit(0, &orphan_timer))
  97                 module_put(THIS_MODULE);
  98
  99         if (soft_noboot)
 100                 printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
 101         else {
 102                 printk(KERN_CRIT PFX "Initiating system reboot.\n");
 103                 emergency_restart();
 104                 printk(KERN_CRIT PFX "Reboot didn't ?????\n");
 105         }
 106 }
 107
 108 /*
 109  *      Softdog operations
 110  */
 111
 112 static int softdog_keepalive(void)
 113 {
 114         mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
 115         return 0;
 116 }
 117
 118 static int softdog_stop(void)
 119 {
 120         del_timer(&watchdog_ticktock);
 121         return 0;
 122 }
 123
 124 static int softdog_set_heartbeat(int t)
 125 {
 126         if ((t < 0x0001) || (t > 0xFFFF))
 127                 return -EINVAL;
 128
 129         soft_margin = t;
 130         return 0;
 131 }
 132
 133 /*
 134  *      /dev/watchdog handling
 135  */
 136
 137 static int softdog_open(struct inode *inode, struct file *file)
 138 {
 139         if (test_and_set_bit(0, &driver_open))
 140                 return -EBUSY;
 141         if (!test_and_clear_bit(0, &orphan_timer))
 142                 __module_get(THIS_MODULE);
 143         /*
 144          *      Activate timer
 145          */
 146         softdog_keepalive();
 147         return nonseekable_open(inode, file);
 148 }
 149
 150 static int softdog_release(struct inode *inode, struct file *file)
 151 {
 152         /*
 153          *      Shut off the timer.
 154          *      Lock it in if it's a module and we set nowayout
 155          */
 156         if (expect_close == 42) {
 157                 softdog_stop();
 158                 module_put(THIS_MODULE);
 159         } else {
 160                 printk(KERN_CRIT PFX
 161                         "Unexpected close, not stopping watchdog!\n");
 162                 set_bit(0, &orphan_timer);
 163                 softdog_keepalive();
 164         }
 165         clear_bit(0, &driver_open);
 166         expect_close = 0;
 167         return 0;
 168 }
 169
 170 static ssize_t softdog_write(struct file *file, const char __user *data,
 171                                                 size_t len, loff_t *ppos)
 172 {
 173         /*
 174          *      Refresh the timer.
 175          */
 176         if (len) {
 177                 if (!nowayout) {
 178                         size_t i;
 179
 180                         /* In case it was set long ago */
 181                         expect_close = 0;
 182
 183                         for (i = 0; i != len; i++) {
 184                                 char c;
 185
 186                                 if (get_user(c, data + i))
 187                                         return -EFAULT;
 188                                 if (c == 'V')
 189                                         expect_close = 42;
 190                         }
 191                 }
 192                 softdog_keepalive();
 193         }
 194         return len;
 195 }
 196
 197 static long softdog_ioctl(struct file *file, unsigned int cmd,
 198                                                         unsigned long arg)
 199 {
 200         void __user *argp = (void __user *)arg;
 201         int __user *p = argp;
 202         int new_margin;
 203         static const struct watchdog_info ident = {
 204                 .options =              WDIOF_SETTIMEOUT |
 205                                         WDIOF_KEEPALIVEPING |
 206                                         WDIOF_MAGICCLOSE,
 207                 .firmware_version =     0,
 208                 .identity =             "Software Watchdog",
 209         };
 210         switch (cmd) {
 211         case WDIOC_GETSUPPORT:
 212                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 213         case WDIOC_GETSTATUS:
 214         case WDIOC_GETBOOTSTATUS:
 215                 return put_user(0, p);
 216         case WDIOC_KEEPALIVE:
 217                 softdog_keepalive();
 218                 return 0;
 219         case WDIOC_SETTIMEOUT:
 220                 if (get_user(new_margin, p))
 221                         return -EFAULT;
 222                 if (softdog_set_heartbeat(new_margin))
 223                         return -EINVAL;
 224                 softdog_keepalive();
 225                 /* Fall */
 226         case WDIOC_GETTIMEOUT:
 227                 return put_user(soft_margin, p);
 228         default:
 229                 return -ENOTTY;
 230         }
 231 }
 232
 233 /*
 234  *      Notifier for system down
 235  */
 236
 237 static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
 238         void *unused)
 239 {
 240         if (code == SYS_DOWN || code == SYS_HALT)
 241                 /* Turn the WDT off */
 242                 softdog_stop();
 243         return NOTIFY_DONE;
 244 }
 245
 246 /*
 247  *      Kernel Interfaces
 248  */
 249
 250 static const struct file_operations softdog_fops = {
 251         .owner          = THIS_MODULE,
 252         .llseek         = no_llseek,
 253         .write          = softdog_write,
 254         .unlocked_ioctl = softdog_ioctl,
 255         .open           = softdog_open,
 256         .release        = softdog_release,
 257 };
 258
 259 static struct miscdevice softdog_miscdev = {
 260         .minor          = WATCHDOG_MINOR,
 261         .name           = "watchdog",
 262         .fops           = &softdog_fops,
 263 };
 264
 265 static struct notifier_block softdog_notifier = {
 266         .notifier_call  = softdog_notify_sys,
 267 };
 268
 269 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 "
 270         "initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n";
 271
 272 static int __init watchdog_init(void)
 273 {
 274         int ret;
 275
 276         /* Check that the soft_margin value is within it's range;
 277            if not reset to the default */
 278         if (softdog_set_heartbeat(soft_margin)) {
 279                 softdog_set_heartbeat(TIMER_MARGIN);
 280                 printk(KERN_INFO PFX
 281                     "soft_margin must be 0 < soft_margin < 65536, using %d\n",
 282                         TIMER_MARGIN);
 283         }
 284
 285         ret = register_reboot_notifier(&softdog_notifier);
 286         if (ret) {
 287                 printk(KERN_ERR PFX
 288                         "cannot register reboot notifier (err=%d)\n", ret);
 289                 return ret;
 290         }
 291
 292         ret = misc_register(&softdog_miscdev);
 293         if (ret) {
 294                 printk(KERN_ERR PFX
 295                         "cannot register miscdev on minor=%d (err=%d)\n",
 296                                                 WATCHDOG_MINOR, ret);
 297                 unregister_reboot_notifier(&softdog_notifier);
 298                 return ret;
 299         }
 300
 301         printk(banner, soft_noboot, soft_margin, nowayout);
 302
 303         return 0;
 304 }
 305
 306 static void __exit watchdog_exit(void)
 307 {
 308         misc_deregister(&softdog_miscdev);
 309         unregister_reboot_notifier(&softdog_notifier);
 310 }
 311
 312 module_init(watchdog_init);
 313 module_exit(watchdog_exit);
 314
 315 MODULE_AUTHOR("Alan Cox");
 316 MODULE_DESCRIPTION("Software Watchdog Device Driver");
 317 MODULE_LICENSE("GPL");
 318 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);