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harddog_kern.c

/* UML hardware watchdog, shamelessly stolen from:
 *
 *    SoftDog     0.05: 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.
 */

#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/smp_lock.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include "mconsole.h"

MODULE_LICENSE("GPL");

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;

      lock_kernel();
      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);
      unlock_kernel();
      return nonseekable_open(inode, file);
err:
      spin_unlock(&lock);
      unlock_kernel();
      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(struct inode *inode, 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 const struct file_operations harddog_fops = {
      .owner            = THIS_MODULE,
      .write            = harddog_write,
      .ioctl            = harddog_ioctl,
      .open       = harddog_open,
      .release    = harddog_release,
};

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);

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