linux-bk/drivers/char/watchdog/softdog.c
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   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 */
  55static int soft_margin = TIMER_MARGIN;  /* in seconds */
  56module_param(soft_margin, int, 0);
  57MODULE_PARM_DESC(soft_margin, "Watchdog soft_margin in seconds. (0<soft_margin<65536, default=" __MODULE_STRING(TIMER_MARGIN) ")");
  58
  59#ifdef CONFIG_WATCHDOG_NOWAYOUT
  60static int nowayout = 1;
  61#else
  62static int nowayout = 0;
  63#endif
  64
  65module_param(nowayout, int, 0);
  66MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");
  67
  68#ifdef ONLY_TESTING
  69static int soft_noboot = 1;
  70#else
  71static int soft_noboot = 0;
  72#endif  /* ONLY_TESTING */
  73
  74module_param(soft_noboot, int, 0);
  75MODULE_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
  81static void watchdog_fire(unsigned long);
  82
  83static struct timer_list watchdog_ticktock =
  84                TIMER_INITIALIZER(watchdog_fire, 0, 0);
  85static unsigned long timer_alive;
  86static char expect_close;
  87
  88
  89/*
  90 *      If the timer expires..
  91 */
  92
  93static 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
 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, &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
 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        } 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
 164static 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
 190static 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
 231static 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
 245static 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
 254static struct miscdevice softdog_miscdev = {
 255        .minor          = WATCHDOG_MINOR,
 256        .name           = "watchdog",
 257        .fops           = &softdog_fops,
 258};
 259
 260static struct notifier_block softdog_notifier = {
 261        .notifier_call  = softdog_notify_sys,
 262};
 263
 264static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n";
 265
 266static 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
 297static void __exit watchdog_exit(void)
 298{
 299        misc_deregister(&softdog_miscdev);
 300        unregister_reboot_notifier(&softdog_notifier);
 301}
 302
 303module_init(watchdog_init);
 304module_exit(watchdog_exit);
 305
 306MODULE_AUTHOR("Alan Cox");
 307MODULE_DESCRIPTION("Software Watchdog Device Driver");
 308MODULE_LICENSE("GPL");
 309MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 310
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