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 <asm/uaccess.h>
  48 #include "mconsole.h"
  49
  50 MODULE_LICENSE("GPL");
  51
  52 /* Locked by the BKL in harddog_open and harddog_release */
  53 static int timer_alive;
  54 static int harddog_in_fd = -1;
  55 static int harddog_out_fd = -1;
  56
  57 /*
  58  *      Allow only one person to hold it open
  59  */
  60
  61 extern int start_watchdog(int *in_fd_ret, int *out_fd_ret, char *sock);
  62
  63 static int harddog_open(struct inode *inode, struct file *file)
  64 {
  65         int err;
  66         char *sock = NULL;
  67
  68         lock_kernel();
  69         if(timer_alive)
  70                 return -EBUSY;
  71 #ifdef CONFIG_HARDDOG_NOWAYOUT
  72         __module_get(THIS_MODULE);
  73 #endif
  74
  75 #ifdef CONFIG_MCONSOLE
  76         sock = mconsole_notify_socket();
  77 #endif
  78         err = start_watchdog(&harddog_in_fd, &harddog_out_fd, sock);
  79         if(err) return(err);
  80
  81         timer_alive = 1;
  82         unlock_kernel();
  83         return nonseekable_open(inode, file);
  84 }
  85
  86 extern void stop_watchdog(int in_fd, int out_fd);
  87
  88 static int harddog_release(struct inode *inode, struct file *file)
  89 {
  90         /*
  91          *      Shut off the timer.
  92          */
  93         lock_kernel();
  94
  95         stop_watchdog(harddog_in_fd, harddog_out_fd);
  96         harddog_in_fd = -1;
  97         harddog_out_fd = -1;
  98
  99         timer_alive=0;
 100         unlock_kernel();
 101         return 0;
 102 }
 103
 104 extern int ping_watchdog(int fd);
 105
 106 static ssize_t harddog_write(struct file *file, const char __user *data, size_t len,
 107                              loff_t *ppos)
 108 {
 109         /*
 110          *      Refresh the timer.
 111          */
 112         if(len)
 113                 return(ping_watchdog(harddog_out_fd));
 114         return 0;
 115 }
 116
 117 static int harddog_ioctl(struct inode *inode, struct file *file,
 118                          unsigned int cmd, unsigned long arg)
 119 {
 120         void __user *argp= (void __user *)arg;
 121         static struct watchdog_info ident = {
 122                 WDIOC_SETTIMEOUT,
 123                 0,
 124                 "UML Hardware Watchdog"
 125         };
 126         switch (cmd) {
 127                 default:
 128                         return -ENOTTY;
 129                 case WDIOC_GETSUPPORT:
 130                         if(copy_to_user(argp, &ident, sizeof(ident)))
 131                                 return -EFAULT;
 132                         return 0;
 133                 case WDIOC_GETSTATUS:
 134                 case WDIOC_GETBOOTSTATUS:
 135                         return put_user(0,(int __user *)argp);
 136                 case WDIOC_KEEPALIVE:
 137                         return(ping_watchdog(harddog_out_fd));
 138         }
 139 }
 140
 141 static struct file_operations harddog_fops = {
 142         .owner          = THIS_MODULE,
 143         .write          = harddog_write,
 144         .ioctl          = harddog_ioctl,
 145         .open           = harddog_open,
 146         .release        = harddog_release,
 147 };
 148
 149 static struct miscdevice harddog_miscdev = {
 150         .minor          = WATCHDOG_MINOR,
 151         .name           = "watchdog",
 152         .fops           = &harddog_fops,
 153 };
 154
 155 static char banner[] __initdata = KERN_INFO "UML Watchdog Timer\n";
 156
 157 static int __init harddog_init(void)
 158 {
 159         int ret;
 160
 161         ret = misc_register(&harddog_miscdev);
 162
 163         if (ret)
 164                 return ret;
 165
 166         printk(banner);
 167
 168         return(0);
 169 }
 170
 171 static void __exit harddog_exit(void)
 172 {
 173         misc_deregister(&harddog_miscdev);
 174 }
 175
 176 module_init(harddog_init);
 177 module_exit(harddog_exit);
 178
 179 /*
 180  * Overrides for Emacs so that we follow Linus's tabbing style.
 181  * Emacs will notice this stuff at the end of the file and automatically
 182  * adjust the settings for this buffer only.  This must remain at the end
 183  * of the file.
 184  * ---------------------------------------------------------------------------
 185  * Local variables:
 186  * c-file-style: "linux"
 187  * End:
 188  */