drivers/char/watchdog/softdog.c

/*
 *	SoftDog	0.07:	A Software Watchdog Device
 *
 *	(c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
 *				http://www.redhat.com
 *
 *	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 <alan@lxorguk.ukuu.org.uk>
 *
 *	Software only watchdog driver. Unlike its big brother the WDT501P
 *	driver this won't always recover a failed machine.
 *
 *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
 *	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 (jlbec@evilplan.org>
 *	Added soft_noboot; Allows testing the softdog trigger without
 *	requiring a recompile.
 *	Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
 *
 *  20020530 Joel Becker <joel.becker@oracle.com>
 *  	Added Matt Domsch's nowayout module option.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/config.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <asm/uaccess.h>

#define PFX "SoftDog: "

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

#ifdef CONFIG_WATCHDOG_NOWAYOUT
static int nowayout = 1;
#else
static int nowayout = 0;
#endif

module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");

#ifdef ONLY_TESTING
static int soft_noboot = 1;
#else
static int soft_noboot = 0;
#endif  /* ONLY_TESTING */

module_param(soft_noboot, int, 0);
MODULE_PARM_DESC(soft_noboot, "Softdog action, set to 1 to ignore reboots, 0 to reboot (default depends on ONLY_TESTING)");

/*
 *	Our timer
 */

static void watchdog_fire(unsigned long);

static struct timer_list watchdog_ticktock =
		TIMER_INITIALIZER(watchdog_fire, 0, 0);
static unsigned long timer_alive;
static char expect_close;


/*
 *	If the timer expires..
 */

static void watchdog_fire(unsigned long data)
{
	if (soft_noboot)
		printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
	else
	{
		printk(KERN_CRIT PFX "Initiating system reboot.\n");
		emergency_restart();
		printk(KERN_CRIT PFX "Reboot didn't ?????\n");
	}
}

/*
 *	Softdog operations
 */

static int softdog_keepalive(void)
{
	mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
	return 0;
}

static int softdog_stop(void)
{
	del_timer(&watchdog_ticktock);
	return 0;
}

static int softdog_set_heartbeat(int t)
{
	if ((t < 0x0001) || (t > 0xFFFF))
		return -EINVAL;

	soft_margin = t;
	return 0;
}

/*
 *	/dev/watchdog handling
 */

static int softdog_open(struct inode *inode, struct file *file)
{
	if(test_and_set_bit(0, &timer_alive))
		return -EBUSY;
	if (nowayout)
		__module_get(THIS_MODULE);
	/*
	 *	Activate timer
	 */
	softdog_keepalive();
	return nonseekable_open(inode, file);
}

static int softdog_release(struct inode *inode, struct file *file)
{
	/*
	 *	Shut off the timer.
	 * 	Lock it in if it's a module and we set nowayout
	 */
	if (expect_close == 42) {
		softdog_stop();
	} else {
		printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
		softdog_keepalive();
	}
	clear_bit(0, &timer_alive);
	expect_close = 0;
	return 0;
}

static ssize_t softdog_write(struct file *file, const char __user *data, size_t len, loff_t *ppos)
{
	/*
	 *	Refresh the timer.
	 */
	if(len) {
		if (!nowayout) {
			size_t i;

			/* In case it was set long ago */
			expect_close = 0;

			for (i = 0; i != len; i++) {
				char c;

				if (get_user(c, data + i))
					return -EFAULT;
				if (c == 'V')
					expect_close = 42;
			}
		}
		softdog_keepalive();
	}
	return len;
}

static int softdog_ioctl(struct inode *inode, struct file *file,
	unsigned int cmd, unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	int new_margin;
	static struct watchdog_info ident = {
		.options =		WDIOF_SETTIMEOUT |
					WDIOF_KEEPALIVEPING |
					WDIOF_MAGICCLOSE,
		.firmware_version =	0,
		.identity =		"Software Watchdog",
	};
	switch (cmd) {
		default:
			return -ENOIOCTLCMD;
		case WDIOC_GETSUPPORT:
			return copy_to_user(argp, &ident,
				sizeof(ident)) ? -EFAULT : 0;
		case WDIOC_GETSTATUS:
		case WDIOC_GETBOOTSTATUS:
			return put_user(0, p);
		case WDIOC_KEEPALIVE:
			softdog_keepalive();
			return 0;
		case WDIOC_SETTIMEOUT:
			if (get_user(new_margin, p))
				return -EFAULT;
			if (softdog_set_heartbeat(new_margin))
				return -EINVAL;
			softdog_keepalive();
			/* Fall */
		case WDIOC_GETTIMEOUT:
			return put_user(soft_margin, p);
	}
}

/*
 *	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();
	}
	return NOTIFY_DONE;
}

/*
 *	Kernel Interfaces
 */

static struct file_operations softdog_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.write		= softdog_write,
	.ioctl		= softdog_ioctl,
	.open		= softdog_open,
	.release	= softdog_release,
};

static struct miscdevice softdog_miscdev = {
	.minor		= WATCHDOG_MINOR,
	.name		= "watchdog",
	.fops		= &softdog_fops,
};

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

static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n";

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 (softdog_set_heartbeat(soft_margin)) {
		softdog_set_heartbeat(TIMER_MARGIN);
		printk(KERN_INFO PFX "soft_margin value must be 0<soft_margin<65536, using %d\n",
			TIMER_MARGIN);
	}

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

	ret = misc_register(&softdog_miscdev);
	if (ret) {
		printk (KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",
			WATCHDOG_MINOR, ret);
		unregister_reboot_notifier(&softdog_notifier);
		return ret;
	}

	printk(banner, soft_noboot, soft_margin, nowayout);

	return 0;
}

static void __exit watchdog_exit(void)
{
	misc_deregister(&softdog_miscdev);
	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);