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