linux/drivers/watchdog/softdog.c
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   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 */
  54static int soft_margin = TIMER_MARGIN;  /* in seconds */
  55module_param(soft_margin, int, 0);
  56MODULE_PARM_DESC(soft_margin,
  57        "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
  58                                        __MODULE_STRING(TIMER_MARGIN) ")");
  59
  60static int nowayout = WATCHDOG_NOWAYOUT;
  61module_param(nowayout, int, 0);
  62MODULE_PARM_DESC(nowayout,
  63                "Watchdog cannot be stopped once started (default="
  64                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  65
  66#ifdef ONLY_TESTING
  67static int soft_noboot = 1;
  68#else
  69static int soft_noboot = 0;
  70#endif  /* ONLY_TESTING */
  71
  72module_param(soft_noboot, int, 0);
  73MODULE_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
  79static void watchdog_fire(unsigned long);
  80
  81static struct timer_list watchdog_ticktock =
  82                TIMER_INITIALIZER(watchdog_fire, 0, 0);
  83static unsigned long driver_open, orphan_timer;
  84static char expect_close;
  85
  86
  87/*
  88 *      If the timer expires..
  89 */
  90
  91static 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
 109static int softdog_keepalive(void)
 110{
 111        mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
 112        return 0;
 113}
 114
 115static int softdog_stop(void)
 116{
 117        del_timer(&watchdog_ticktock);
 118        return 0;
 119}
 120
 121static 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
 134static 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
 147static 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
 167static 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
 194static 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
 234static 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
 247static 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
 256static struct miscdevice softdog_miscdev = {
 257        .minor          = WATCHDOG_MINOR,
 258        .name           = "watchdog",
 259        .fops           = &softdog_fops,
 260};
 261
 262static struct notifier_block softdog_notifier = {
 263        .notifier_call  = softdog_notify_sys,
 264};
 265
 266static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n";
 267
 268static 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
 302static void __exit watchdog_exit(void)
 303{
 304        misc_deregister(&softdog_miscdev);
 305        unregister_reboot_notifier(&softdog_notifier);
 306}
 307
 308module_init(watchdog_init);
 309module_exit(watchdog_exit);
 310
 311MODULE_AUTHOR("Alan Cox");
 312MODULE_DESCRIPTION("Software Watchdog Device Driver");
 313MODULE_LICENSE("GPL");
 314MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 315