softdog.c

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/*
 *  SoftDog:    A Software Watchdog Device
 *
 *  (c) Copyright 1996 Alan Cox <[email protected]>,
 *                          All Rights Reserved.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 *  Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
 *  warranty for any of this software. This material is provided
 *  "AS-IS" and at no charge.
 *
 *  (c) Copyright 1995    Alan Cox <[email protected]>
 *
 *  Software only watchdog driver. Unlike its big brother the WDT501P
 *  driver this won't always recover a failed machine.
 *
 *  03/96: Angelo Haritsis <[email protected]> :
 *  Modularised.
 *  Added soft_margin; use upon insmod to change the timer delay.
 *  NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
 *      minors.
 *
 *  19980911 Alan Cox
 *  Made SMP safe for 2.3.x
 *
 *  20011127 Joel Becker ([email protected]>
 *  Added soft_noboot; Allows testing the softdog trigger without
 *  requiring a recompile.
 *  Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
 *
 *  20020530 Joel Becker <[email protected]>
 *  Added Matt Domsch's nowayout module option.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>

#define TIMER_MARGIN    60      /* Default is 60 seconds */
static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
module_param(soft_margin, uint, 0);
MODULE_PARM_DESC(soft_margin,
    "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
                    __MODULE_STRING(TIMER_MARGIN) ")");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
        "Watchdog cannot be stopped once started (default="
                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

static int soft_noboot = 0;
module_param(soft_noboot, int, 0);
MODULE_PARM_DESC(soft_noboot,
    "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");

static int soft_panic;
module_param(soft_panic, int, 0);
MODULE_PARM_DESC(soft_panic,
    "Softdog action, set to 1 to panic, 0 to reboot (default=0)");

/*
 *  Our timer
 */

static void watchdog_fire(unsigned long);

static struct timer_list watchdog_ticktock =
        TIMER_INITIALIZER(watchdog_fire, 0, 0);

/*
 *  If the timer expires..
 */

static void watchdog_fire(unsigned long data)
{
    if (soft_noboot)
        pr_crit("Triggered - Reboot ignored\n");
    else if (soft_panic) {
        pr_crit("Initiating panic\n");
        panic("Software Watchdog Timer expired");
    } else {
        pr_crit("Initiating system reboot\n");
        emergency_restart();
        pr_crit("Reboot didn't ?????\n");
    }
}

/*
 *  Softdog operations
 */

static int softdog_ping(struct watchdog_device *w)
{
    mod_timer(&watchdog_ticktock, jiffies+(w->timeout*HZ));
    return 0;
}

static int softdog_stop(struct watchdog_device *w)
{
    del_timer(&watchdog_ticktock);
    return 0;
}

static int softdog_set_timeout(struct watchdog_device *w, unsigned int t)
{
    w->timeout = t;
    return 0;
}

/*
 *  Notifier for system down
 */

static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
    void *unused)
{
    if (code == SYS_DOWN || code == SYS_HALT)
        /* Turn the WDT off */
        softdog_stop(NULL);
    return NOTIFY_DONE;
}

/*
 *  Kernel Interfaces
 */

static struct notifier_block softdog_notifier = {
    .notifier_call  = softdog_notify_sys,
};

static struct watchdog_info softdog_info = {
    .identity = "Software Watchdog",
    .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
};

static struct watchdog_ops softdog_ops = {
    .owner = THIS_MODULE,
    .start = softdog_ping,
    .stop = softdog_stop,
    .ping = softdog_ping,
    .set_timeout = softdog_set_timeout,
};

static struct watchdog_device softdog_dev = {
    .info = &softdog_info,
    .ops = &softdog_ops,
    .min_timeout = 1,
    .max_timeout = 0xFFFF
};

static int __init watchdog_init(void)
{
    int ret;

    /* Check that the soft_margin value is within it's range;
       if not reset to the default */
    if (soft_margin < 1 || soft_margin > 65535) {
        pr_info("soft_margin must be 0 < soft_margin < 65536, using %d\n",
            TIMER_MARGIN);
        return -EINVAL;
    }
    softdog_dev.timeout = soft_margin;

    watchdog_set_nowayout(&softdog_dev, nowayout);

    ret = register_reboot_notifier(&softdog_notifier);
    if (ret) {
        pr_err("cannot register reboot notifier (err=%d)\n", ret);
        return ret;
    }

    ret = watchdog_register_device(&softdog_dev);
    if (ret) {
        unregister_reboot_notifier(&softdog_notifier);
        return ret;
    }

    pr_info("Software Watchdog Timer: 0.08 initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
        soft_noboot, soft_margin, soft_panic, nowayout);

    return 0;
}

static void __exit watchdog_exit(void)
{
    watchdog_unregister_device(&softdog_dev);
    unregister_reboot_notifier(&softdog_notifier);
}

module_init(watchdog_init);
module_exit(watchdog_exit);

MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("Software Watchdog Device Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);