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