drivers/char/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/config.h>
  42 #include <linux/types.h>
  43 #include <linux/timer.h>
  44 #include <linux/miscdevice.h>
  45 #include <linux/watchdog.h>
  46 #include <linux/fs.h>
  47 #include <linux/notifier.h>
  48 #include <linux/reboot.h>
  49 #include <linux/init.h>
  50 #include <asm/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, "Watchdog soft_margin in seconds. (0<soft_margin<65536, default=" __MODULE_STRING(TIMER_MARGIN) ")");
  58
  59 #ifdef CONFIG_WATCHDOG_NOWAYOUT
  60 static int nowayout = 1;
  61 #else
  62 static int nowayout = 0;
  63 #endif
  64
  65 module_param(nowayout, int, 0);
  66 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_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, "Softdog action, set to 1 to ignore reboots, 0 to reboot (default depends on ONLY_TESTING)");
  76
  77 /*
  78  *      Our timer
  79  */
  80
  81 static void watchdog_fire(unsigned long);
  82
  83 static struct timer_list watchdog_ticktock =
  84                 TIMER_INITIALIZER(watchdog_fire, 0, 0);
  85 static unsigned long timer_alive;
  86 static char expect_close;
  87
  88
  89 /*
  90  *      If the timer expires..
  91  */
  92
  93 static void watchdog_fire(unsigned long data)
  94 {
  95         if (soft_noboot)
  96                 printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
  97         else
  98         {
  99                 printk(KERN_CRIT PFX "Initiating system reboot.\n");
 100                 machine_restart(NULL);
 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, &timer_alive))
 137                 return -EBUSY;
 138         if (nowayout)
 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         } else {
 156                 printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
 157                 softdog_keepalive();
 158         }
 159         clear_bit(0, &timer_alive);
 160         expect_close = 0;
 161         return 0;
 162 }
 163
 164 static ssize_t softdog_write(struct file *file, const char __user *data, size_t len, loff_t *ppos)
 165 {
 166         /*
 167          *      Refresh the timer.
 168          */
 169         if(len) {
 170                 if (!nowayout) {
 171                         size_t i;
 172
 173                         /* In case it was set long ago */
 174                         expect_close = 0;
 175
 176                         for (i = 0; i != len; i++) {
 177                                 char c;
 178
 179                                 if (get_user(c, data + i))
 180                                         return -EFAULT;
 181                                 if (c == 'V')
 182                                         expect_close = 42;
 183                         }
 184                 }
 185                 softdog_keepalive();
 186         }
 187         return len;
 188 }
 189
 190 static int softdog_ioctl(struct inode *inode, struct file *file,
 191         unsigned int cmd, unsigned long arg)
 192 {
 193         void __user *argp = (void __user *)arg;
 194         int __user *p = argp;
 195         int new_margin;
 196         static struct watchdog_info ident = {
 197                 .options =              WDIOF_SETTIMEOUT |
 198                                         WDIOF_KEEPALIVEPING |
 199                                         WDIOF_MAGICCLOSE,
 200                 .firmware_version =     0,
 201                 .identity =             "Software Watchdog",
 202         };
 203         switch (cmd) {
 204                 default:
 205                         return -ENOIOCTLCMD;
 206                 case WDIOC_GETSUPPORT:
 207                         return copy_to_user(argp, &ident,
 208                                 sizeof(ident)) ? -EFAULT : 0;
 209                 case WDIOC_GETSTATUS:
 210                 case WDIOC_GETBOOTSTATUS:
 211                         return put_user(0, p);
 212                 case WDIOC_KEEPALIVE:
 213                         softdog_keepalive();
 214                         return 0;
 215                 case WDIOC_SETTIMEOUT:
 216                         if (get_user(new_margin, p))
 217                                 return -EFAULT;
 218                         if (softdog_set_heartbeat(new_margin))
 219                                 return -EINVAL;
 220                         softdog_keepalive();
 221                         /* Fall */
 222                 case WDIOC_GETTIMEOUT:
 223                         return put_user(soft_margin, p);
 224         }
 225 }
 226
 227 /*
 228  *      Notifier for system down
 229  */
 230
 231 static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
 232         void *unused)
 233 {
 234         if(code==SYS_DOWN || code==SYS_HALT) {
 235                 /* Turn the WDT off */
 236                 softdog_stop();
 237         }
 238         return NOTIFY_DONE;
 239 }
 240
 241 /*
 242  *      Kernel Interfaces
 243  */
 244
 245 static struct file_operations softdog_fops = {
 246         .owner          = THIS_MODULE,
 247         .llseek         = no_llseek,
 248         .write          = softdog_write,
 249         .ioctl          = softdog_ioctl,
 250         .open           = softdog_open,
 251         .release        = softdog_release,
 252 };
 253
 254 static struct miscdevice softdog_miscdev = {
 255         .minor          = WATCHDOG_MINOR,
 256         .name           = "watchdog",
 257         .fops           = &softdog_fops,
 258 };
 259
 260 static struct notifier_block softdog_notifier = {
 261         .notifier_call  = softdog_notify_sys,
 262 };
 263
 264 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n";
 265
 266 static int __init watchdog_init(void)
 267 {
 268         int ret;
 269
 270         /* Check that the soft_margin value is within it's range ; if not reset to the default */
 271         if (softdog_set_heartbeat(soft_margin)) {
 272                 softdog_set_heartbeat(TIMER_MARGIN);
 273                 printk(KERN_INFO PFX "soft_margin value must be 0<soft_margin<65536, using %d\n",
 274                         TIMER_MARGIN);
 275         }
 276
 277         ret = register_reboot_notifier(&softdog_notifier);
 278         if (ret) {
 279                 printk (KERN_ERR PFX "cannot register reboot notifier (err=%d)\n",
 280                         ret);
 281                 return ret;
 282         }
 283
 284         ret = misc_register(&softdog_miscdev);
 285         if (ret) {
 286                 printk (KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",
 287                         WATCHDOG_MINOR, ret);
 288                 unregister_reboot_notifier(&softdog_notifier);
 289                 return ret;
 290         }
 291
 292         printk(banner, soft_noboot, soft_margin, nowayout);
 293
 294         return 0;
 295 }
 296
 297 static void __exit watchdog_exit(void)
 298 {
 299         misc_deregister(&softdog_miscdev);
 300         unregister_reboot_notifier(&softdog_notifier);
 301 }
 302
 303 module_init(watchdog_init);
 304 module_exit(watchdog_exit);
 305
 306 MODULE_AUTHOR("Alan Cox");
 307 MODULE_DESCRIPTION("Software Watchdog Device Driver");
 308 MODULE_LICENSE("GPL");
 309 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);