drivers/watchdog/softdog.c

   1 /*
   2  *      SoftDog 0.07:   A Software Watchdog Device
   3  *
   4  *      (c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
   5  *                              http://www.redhat.com
   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
  51 #include <asm/uaccess.h>
  52
  53 #define PFX "SoftDog: "
  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, "Watchdog soft_margin in seconds. (0<soft_margin<65536, default=" __MODULE_STRING(TIMER_MARGIN) ")");
  59
  60 static int nowayout = WATCHDOG_NOWAYOUT;
  61 module_param(nowayout, int, 0);
  62 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  63
  64 #ifdef ONLY_TESTING
  65 static int soft_noboot = 1;
  66 #else
  67 static int soft_noboot = 0;
  68 #endif  /* ONLY_TESTING */
  69
  70 module_param(soft_noboot, int, 0);
  71 MODULE_PARM_DESC(soft_noboot, "Softdog action, set to 1 to ignore reboots, 0 to reboot (default depends on ONLY_TESTING)");
  72
  73 /*
  74  *      Our timer
  75  */
  76
  77 static void watchdog_fire(unsigned long);
  78
  79 static struct timer_list watchdog_ticktock =
  80                 TIMER_INITIALIZER(watchdog_fire, 0, 0);
  81 static unsigned long driver_open, orphan_timer;
  82 static char expect_close;
  83
  84
  85 /*
  86  *      If the timer expires..
  87  */
  88
  89 static void watchdog_fire(unsigned long data)
  90 {
  91         if (test_and_clear_bit(0, &orphan_timer))
  92                 module_put(THIS_MODULE);
  93
  94         if (soft_noboot)
  95                 printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
  96         else
  97         {
  98                 printk(KERN_CRIT PFX "Initiating system reboot.\n");
  99                 emergency_restart();
 100                 printk(KERN_CRIT PFX "Reboot didn't ?????\n");
 101         }
 102 }
 103
 104 /*
 105  *      Softdog operations
 106  */
 107
 108 static int softdog_keepalive(void)
 109 {
 110         mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
 111         return 0;
 112 }
 113
 114 static int softdog_stop(void)
 115 {
 116         del_timer(&watchdog_ticktock);
 117         return 0;
 118 }
 119
 120 static int softdog_set_heartbeat(int t)
 121 {
 122         if ((t < 0x0001) || (t > 0xFFFF))
 123                 return -EINVAL;
 124
 125         soft_margin = t;
 126         return 0;
 127 }
 128
 129 /*
 130  *      /dev/watchdog handling
 131  */
 132
 133 static int softdog_open(struct inode *inode, struct file *file)
 134 {
 135         if (test_and_set_bit(0, &driver_open))
 136                 return -EBUSY;
 137         if (!test_and_clear_bit(0, &orphan_timer))
 138                 __module_get(THIS_MODULE);
 139         /*
 140          *      Activate timer
 141          */
 142         softdog_keepalive();
 143         return nonseekable_open(inode, file);
 144 }
 145
 146 static int softdog_release(struct inode *inode, struct file *file)
 147 {
 148         /*
 149          *      Shut off the timer.
 150          *      Lock it in if it's a module and we set nowayout
 151          */
 152         if (expect_close == 42) {
 153                 softdog_stop();
 154                 module_put(THIS_MODULE);
 155         } else {
 156                 printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
 157                 set_bit(0, &orphan_timer);
 158                 softdog_keepalive();
 159         }
 160         clear_bit(0, &driver_open);
 161         expect_close = 0;
 162         return 0;
 163 }
 164
 165 static ssize_t softdog_write(struct file *file, const char __user *data, size_t len, loff_t *ppos)
 166 {
 167         /*
 168          *      Refresh the timer.
 169          */
 170         if(len) {
 171                 if (!nowayout) {
 172                         size_t i;
 173
 174                         /* In case it was set long ago */
 175                         expect_close = 0;
 176
 177                         for (i = 0; i != len; i++) {
 178                                 char c;
 179
 180                                 if (get_user(c, data + i))
 181                                         return -EFAULT;
 182                                 if (c == 'V')
 183                                         expect_close = 42;
 184                         }
 185                 }
 186                 softdog_keepalive();
 187         }
 188         return len;
 189 }
 190
 191 static int softdog_ioctl(struct inode *inode, struct file *file,
 192         unsigned int cmd, unsigned long arg)
 193 {
 194         void __user *argp = (void __user *)arg;
 195         int __user *p = argp;
 196         int new_margin;
 197         static struct watchdog_info ident = {
 198                 .options =              WDIOF_SETTIMEOUT |
 199                                         WDIOF_KEEPALIVEPING |
 200                                         WDIOF_MAGICCLOSE,
 201                 .firmware_version =     0,
 202                 .identity =             "Software Watchdog",
 203         };
 204         switch (cmd) {
 205                 default:
 206                         return -ENOTTY;
 207                 case WDIOC_GETSUPPORT:
 208                         return copy_to_user(argp, &ident,
 209                                 sizeof(ident)) ? -EFAULT : 0;
 210                 case WDIOC_GETSTATUS:
 211                 case WDIOC_GETBOOTSTATUS:
 212                         return put_user(0, p);
 213                 case WDIOC_KEEPALIVE:
 214                         softdog_keepalive();
 215                         return 0;
 216                 case WDIOC_SETTIMEOUT:
 217                         if (get_user(new_margin, p))
 218                                 return -EFAULT;
 219                         if (softdog_set_heartbeat(new_margin))
 220                                 return -EINVAL;
 221                         softdog_keepalive();
 222                         /* Fall */
 223                 case WDIOC_GETTIMEOUT:
 224                         return put_user(soft_margin, p);
 225         }
 226 }
 227
 228 /*
 229  *      Notifier for system down
 230  */
 231
 232 static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
 233         void *unused)
 234 {
 235         if(code==SYS_DOWN || code==SYS_HALT) {
 236                 /* Turn the WDT off */
 237                 softdog_stop();
 238         }
 239         return NOTIFY_DONE;
 240 }
 241
 242 /*
 243  *      Kernel Interfaces
 244  */
 245
 246 static const struct file_operations softdog_fops = {
 247         .owner          = THIS_MODULE,
 248         .llseek         = no_llseek,
 249         .write          = softdog_write,
 250         .ioctl          = softdog_ioctl,
 251         .open           = softdog_open,
 252         .release        = softdog_release,
 253 };
 254
 255 static struct miscdevice softdog_miscdev = {
 256         .minor          = WATCHDOG_MINOR,
 257         .name           = "watchdog",
 258         .fops           = &softdog_fops,
 259 };
 260
 261 static struct notifier_block softdog_notifier = {
 262         .notifier_call  = softdog_notify_sys,
 263 };
 264
 265 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n";
 266
 267 static int __init watchdog_init(void)
 268 {
 269         int ret;
 270
 271         /* Check that the soft_margin value is within it's range ; if not reset to the default */
 272         if (softdog_set_heartbeat(soft_margin)) {
 273                 softdog_set_heartbeat(TIMER_MARGIN);
 274                 printk(KERN_INFO PFX "soft_margin value must be 0<soft_margin<65536, using %d\n",
 275                         TIMER_MARGIN);
 276         }
 277
 278         ret = register_reboot_notifier(&softdog_notifier);
 279         if (ret) {
 280                 printk (KERN_ERR PFX "cannot register reboot notifier (err=%d)\n",
 281                         ret);
 282                 return ret;
 283         }
 284
 285         ret = misc_register(&softdog_miscdev);
 286         if (ret) {
 287                 printk (KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",
 288                         WATCHDOG_MINOR, ret);
 289                 unregister_reboot_notifier(&softdog_notifier);
 290                 return ret;
 291         }
 292
 293         printk(banner, soft_noboot, soft_margin, nowayout);
 294
 295         return 0;
 296 }
 297
 298 static void __exit watchdog_exit(void)
 299 {
 300         misc_deregister(&softdog_miscdev);
 301         unregister_reboot_notifier(&softdog_notifier);
 302 }
 303
 304 module_init(watchdog_init);
 305 module_exit(watchdog_exit);
 306
 307 MODULE_AUTHOR("Alan Cox");
 308 MODULE_DESCRIPTION("Software Watchdog Device Driver");
 309 MODULE_LICENSE("GPL");
 310 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);