arch/um/drivers/harddog_kern.c

   1 /* UML hardware watchdog, shamelessly stolen from:
   2  *
   3  *      SoftDog 0.05:   A Software Watchdog Device
   4  *
   5  *      (c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
   6  *                              http://www.redhat.com
   7  *
   8  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  *
  13  *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
  14  *      warranty for any of this software. This material is provided
  15  *      "AS-IS" and at no charge.
  16  *
  17  *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
  18  *
  19  *      Software only watchdog driver. Unlike its big brother the WDT501P
  20  *      driver this won't always recover a failed machine.
  21  *
  22  *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
  23  *      Modularised.
  24  *      Added soft_margin; use upon insmod to change the timer delay.
  25  *      NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
  26  *          minors.
  27  *
  28  *  19980911 Alan Cox
  29  *      Made SMP safe for 2.3.x
  30  *
  31  *  20011127 Joel Becker (jlbec@evilplan.org>
  32  *      Added soft_noboot; Allows testing the softdog trigger without
  33  *      requiring a recompile.
  34  *      Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
  35  */
  36
  37 #include <linux/module.h>
  38 #include <linux/types.h>
  39 #include <linux/kernel.h>
  40 #include <linux/fs.h>
  41 #include <linux/mm.h>
  42 #include <linux/miscdevice.h>
  43 #include <linux/watchdog.h>
  44 #include <linux/reboot.h>
  45 #include <linux/mutex.h>
  46 #include <linux/init.h>
  47 #include <linux/spinlock.h>
  48 #include <linux/uaccess.h>
  49 #include "mconsole.h"
  50
  51 MODULE_LICENSE("GPL");
  52
  53 static DEFINE_MUTEX(harddog_mutex);
  54 static DEFINE_SPINLOCK(lock);
  55 static int timer_alive;
  56 static int harddog_in_fd = -1;
  57 static int harddog_out_fd = -1;
  58
  59 /*
  60  *      Allow only one person to hold it open
  61  */
  62
  63 extern int start_watchdog(int *in_fd_ret, int *out_fd_ret, char *sock);
  64
  65 static int harddog_open(struct inode *inode, struct file *file)
  66 {
  67         int err = -EBUSY;
  68         char *sock = NULL;
  69
  70         mutex_lock(&harddog_mutex);
  71         spin_lock(&lock);
  72         if(timer_alive)
  73                 goto err;
  74 #ifdef CONFIG_WATCHDOG_NOWAYOUT
  75         __module_get(THIS_MODULE);
  76 #endif
  77
  78 #ifdef CONFIG_MCONSOLE
  79         sock = mconsole_notify_socket();
  80 #endif
  81         err = start_watchdog(&harddog_in_fd, &harddog_out_fd, sock);
  82         if(err)
  83                 goto err;
  84
  85         timer_alive = 1;
  86         spin_unlock(&lock);
  87         mutex_unlock(&harddog_mutex);
  88         return nonseekable_open(inode, file);
  89 err:
  90         spin_unlock(&lock);
  91         mutex_unlock(&harddog_mutex);
  92         return err;
  93 }
  94
  95 extern void stop_watchdog(int in_fd, int out_fd);
  96
  97 static int harddog_release(struct inode *inode, struct file *file)
  98 {
  99         /*
 100          *      Shut off the timer.
 101          */
 102
 103         spin_lock(&lock);
 104
 105         stop_watchdog(harddog_in_fd, harddog_out_fd);
 106         harddog_in_fd = -1;
 107         harddog_out_fd = -1;
 108
 109         timer_alive=0;
 110         spin_unlock(&lock);
 111
 112         return 0;
 113 }
 114
 115 extern int ping_watchdog(int fd);
 116
 117 static ssize_t harddog_write(struct file *file, const char __user *data, size_t len,
 118                              loff_t *ppos)
 119 {
 120         /*
 121          *      Refresh the timer.
 122          */
 123         if(len)
 124                 return ping_watchdog(harddog_out_fd);
 125         return 0;
 126 }
 127
 128 static int harddog_ioctl_unlocked(struct file *file,
 129                                   unsigned int cmd, unsigned long arg)
 130 {
 131         void __user *argp= (void __user *)arg;
 132         static struct watchdog_info ident = {
 133                 WDIOC_SETTIMEOUT,
 134                 0,
 135                 "UML Hardware Watchdog"
 136         };
 137         switch (cmd) {
 138                 default:
 139                         return -ENOTTY;
 140                 case WDIOC_GETSUPPORT:
 141                         if(copy_to_user(argp, &ident, sizeof(ident)))
 142                                 return -EFAULT;
 143                         return 0;
 144                 case WDIOC_GETSTATUS:
 145                 case WDIOC_GETBOOTSTATUS:
 146                         return put_user(0,(int __user *)argp);
 147                 case WDIOC_KEEPALIVE:
 148                         return ping_watchdog(harddog_out_fd);
 149         }
 150 }
 151
 152 static long harddog_ioctl(struct file *file,
 153                           unsigned int cmd, unsigned long arg)
 154 {
 155         long ret;
 156
 157         mutex_lock(&harddog_mutex);
 158         ret = harddog_ioctl_unlocked(file, cmd, arg);
 159         mutex_unlock(&harddog_mutex);
 160
 161         return ret;
 162 }
 163
 164 static const struct file_operations harddog_fops = {
 165         .owner          = THIS_MODULE,
 166         .write          = harddog_write,
 167         .unlocked_ioctl = harddog_ioctl,
 168         .open           = harddog_open,
 169         .release        = harddog_release,
 170         .llseek         = no_llseek,
 171 };
 172
 173 static struct miscdevice harddog_miscdev = {
 174         .minor          = WATCHDOG_MINOR,
 175         .name           = "watchdog",
 176         .fops           = &harddog_fops,
 177 };
 178 module_misc_device(harddog_miscdev);