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/smp_lock.h>
  46 #include <linux/init.h>
  47 #include <linux/spinlock.h>
  48 #include <asm/uaccess.h>
  49 #include "mconsole.h"
  50
  51 MODULE_LICENSE("GPL");
  52
  53 static DEFINE_SPINLOCK(lock);
  54 static int timer_alive;
  55 static int harddog_in_fd = -1;
  56 static int harddog_out_fd = -1;
  57
  58 /*
  59  *      Allow only one person to hold it open
  60  */
  61
  62 extern int start_watchdog(int *in_fd_ret, int *out_fd_ret, char *sock);
  63
  64 static int harddog_open(struct inode *inode, struct file *file)
  65 {
  66         int err = -EBUSY;
  67         char *sock = NULL;
  68
  69         lock_kernel();
  70         spin_lock(&lock);
  71         if(timer_alive)
  72                 goto err;
  73 #ifdef CONFIG_WATCHDOG_NOWAYOUT
  74         __module_get(THIS_MODULE);
  75 #endif
  76
  77 #ifdef CONFIG_MCONSOLE
  78         sock = mconsole_notify_socket();
  79 #endif
  80         err = start_watchdog(&harddog_in_fd, &harddog_out_fd, sock);
  81         if(err)
  82                 goto err;
  83
  84         timer_alive = 1;
  85         spin_unlock(&lock);
  86         unlock_kernel();
  87         return nonseekable_open(inode, file);
  88 err:
  89         spin_unlock(&lock);
  90         unlock_kernel();
  91         return err;
  92 }
  93
  94 extern void stop_watchdog(int in_fd, int out_fd);
  95
  96 static int harddog_release(struct inode *inode, struct file *file)
  97 {
  98         /*
  99          *      Shut off the timer.
 100          */
 101
 102         spin_lock(&lock);
 103
 104         stop_watchdog(harddog_in_fd, harddog_out_fd);
 105         harddog_in_fd = -1;
 106         harddog_out_fd = -1;
 107
 108         timer_alive=0;
 109         spin_unlock(&lock);
 110
 111         return 0;
 112 }
 113
 114 extern int ping_watchdog(int fd);
 115
 116 static ssize_t harddog_write(struct file *file, const char __user *data, size_t len,
 117                              loff_t *ppos)
 118 {
 119         /*
 120          *      Refresh the timer.
 121          */
 122         if(len)
 123                 return ping_watchdog(harddog_out_fd);
 124         return 0;
 125 }
 126
 127 static int harddog_ioctl(struct inode *inode, struct file *file,
 128                          unsigned int cmd, unsigned long arg)
 129 {
 130         void __user *argp= (void __user *)arg;
 131         static struct watchdog_info ident = {
 132                 WDIOC_SETTIMEOUT,
 133                 0,
 134                 "UML Hardware Watchdog"
 135         };
 136         switch (cmd) {
 137                 default:
 138                         return -ENOTTY;
 139                 case WDIOC_GETSUPPORT:
 140                         if(copy_to_user(argp, &ident, sizeof(ident)))
 141                                 return -EFAULT;
 142                         return 0;
 143                 case WDIOC_GETSTATUS:
 144                 case WDIOC_GETBOOTSTATUS:
 145                         return put_user(0,(int __user *)argp);
 146                 case WDIOC_KEEPALIVE:
 147                         return ping_watchdog(harddog_out_fd);
 148         }
 149 }
 150
 151 static const struct file_operations harddog_fops = {
 152         .owner          = THIS_MODULE,
 153         .write          = harddog_write,
 154         .ioctl          = harddog_ioctl,
 155         .open           = harddog_open,
 156         .release        = harddog_release,
 157 };
 158
 159 static struct miscdevice harddog_miscdev = {
 160         .minor          = WATCHDOG_MINOR,
 161         .name           = "watchdog",
 162         .fops           = &harddog_fops,
 163 };
 164
 165 static char banner[] __initdata = KERN_INFO "UML Watchdog Timer\n";
 166
 167 static int __init harddog_init(void)
 168 {
 169         int ret;
 170
 171         ret = misc_register(&harddog_miscdev);
 172
 173         if (ret)
 174                 return ret;
 175
 176         printk(banner);
 177
 178         return 0;
 179 }
 180
 181 static void __exit harddog_exit(void)
 182 {
 183         misc_deregister(&harddog_miscdev);
 184 }
 185
 186 module_init(harddog_init);
 187 module_exit(harddog_exit);