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