harddog_kern.c

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/* UML hardware watchdog, shamelessly stolen from:
 *
 *  SoftDog 0.05:   A Software Watchdog Device
 *
 *  (c) Copyright 1996 Alan Cox <[email protected]>, 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 <[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.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/reboot.h>
#include <linux/mutex.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include "mconsole.h"

MODULE_LICENSE("GPL");

static DEFINE_MUTEX(harddog_mutex);
static DEFINE_SPINLOCK(lock);
static int timer_alive;
static int harddog_in_fd = -1;
static int harddog_out_fd = -1;

/*
 *  Allow only one person to hold it open
 */

extern int start_watchdog(int *in_fd_ret, int *out_fd_ret, char *sock);

static int harddog_open(struct inode *inode, struct file *file)
{
    int err = -EBUSY;
    char *sock = NULL;

    mutex_lock(&harddog_mutex);
    spin_lock(&lock);
    if(timer_alive)
        goto err;
#ifdef CONFIG_WATCHDOG_NOWAYOUT
    __module_get(THIS_MODULE);
#endif

#ifdef CONFIG_MCONSOLE
    sock = mconsole_notify_socket();
#endif
    err = start_watchdog(&harddog_in_fd, &harddog_out_fd, sock);
    if(err)
        goto err;

    timer_alive = 1;
    spin_unlock(&lock);
    mutex_unlock(&harddog_mutex);
    return nonseekable_open(inode, file);
err:
    spin_unlock(&lock);
    mutex_unlock(&harddog_mutex);
    return err;
}

extern void stop_watchdog(int in_fd, int out_fd);

static int harddog_release(struct inode *inode, struct file *file)
{
    /*
     *  Shut off the timer.
     */

    spin_lock(&lock);

    stop_watchdog(harddog_in_fd, harddog_out_fd);
    harddog_in_fd = -1;
    harddog_out_fd = -1;

    timer_alive=0;
    spin_unlock(&lock);

    return 0;
}

extern int ping_watchdog(int fd);

static ssize_t harddog_write(struct file *file, const char __user *data, size_t len,
                 loff_t *ppos)
{
    /*
     *  Refresh the timer.
     */
    if(len)
        return ping_watchdog(harddog_out_fd);
    return 0;
}

static int harddog_ioctl_unlocked(struct file *file,
                  unsigned int cmd, unsigned long arg)
{
    void __user *argp= (void __user *)arg;
    static struct watchdog_info ident = {
        WDIOC_SETTIMEOUT,
        0,
        "UML Hardware Watchdog"
    };
    switch (cmd) {
        default:
            return -ENOTTY;
        case WDIOC_GETSUPPORT:
            if(copy_to_user(argp, &ident, sizeof(ident)))
                return -EFAULT;
            return 0;
        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
            return put_user(0,(int __user *)argp);
        case WDIOC_KEEPALIVE:
            return ping_watchdog(harddog_out_fd);
    }
}

static long harddog_ioctl(struct file *file,
              unsigned int cmd, unsigned long arg)
{
    long ret;

    mutex_lock(&harddog_mutex);
    ret = harddog_ioctl_unlocked(file, cmd, arg);
    mutex_unlock(&harddog_mutex);

    return ret;
}

static const struct file_operations harddog_fops = {
    .owner      = THIS_MODULE,
    .write      = harddog_write,
    .unlocked_ioctl = harddog_ioctl,
    .open       = harddog_open,
    .release    = harddog_release,
    .llseek     = no_llseek,
};

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

static char banner[] __initdata = KERN_INFO "UML Watchdog Timer\n";

static int __init harddog_init(void)
{
    int ret;

    ret = misc_register(&harddog_miscdev);

    if (ret)
        return ret;

    printk(banner);

    return 0;
}

static void __exit harddog_exit(void)
{
    misc_deregister(&harddog_miscdev);
}

module_init(harddog_init);
module_exit(harddog_exit);