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#include "harddog.h"
51
52MODULE_DESCRIPTION("UML hardware watchdog");
53MODULE_LICENSE("GPL");
54
55static DEFINE_MUTEX(harddog_mutex);
56static DEFINE_SPINLOCK(lock);
57static int timer_alive;
58static int harddog_in_fd = -1;
59static int harddog_out_fd = -1;
60
61/*
62 * Allow only one person to hold it open
63 */
64
65static 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: &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(in_fd_ret: &harddog_in_fd, out_fd_ret: &harddog_out_fd, sock);
82 if(err)
83 goto err;
84
85 timer_alive = 1;
86 spin_unlock(lock: &lock);
87 mutex_unlock(lock: &harddog_mutex);
88 return stream_open(inode, filp: file);
89err:
90 spin_unlock(lock: &lock);
91 mutex_unlock(lock: &harddog_mutex);
92 return err;
93}
94
95static int harddog_release(struct inode *inode, struct file *file)
96{
97 /*
98 * Shut off the timer.
99 */
100
101 spin_lock(lock: &lock);
102
103 stop_watchdog(in_fd: harddog_in_fd, out_fd: harddog_out_fd);
104 harddog_in_fd = -1;
105 harddog_out_fd = -1;
106
107 timer_alive=0;
108 spin_unlock(lock: &lock);
109
110 return 0;
111}
112
113static 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(fd: harddog_out_fd);
121 return 0;
122}
123
124static int harddog_ioctl_unlocked(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(to: argp, from: &ident, n: 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(fd: harddog_out_fd);
145 }
146}
147
148static long harddog_ioctl(struct file *file,
149 unsigned int cmd, unsigned long arg)
150{
151 long ret;
152
153 mutex_lock(&harddog_mutex);
154 ret = harddog_ioctl_unlocked(file, cmd, arg);
155 mutex_unlock(lock: &harddog_mutex);
156
157 return ret;
158}
159
160static const struct file_operations harddog_fops = {
161 .owner = THIS_MODULE,
162 .write = harddog_write,
163 .unlocked_ioctl = harddog_ioctl,
164 .compat_ioctl = compat_ptr_ioctl,
165 .open = harddog_open,
166 .release = harddog_release,
167};
168
169static struct miscdevice harddog_miscdev = {
170 .minor = WATCHDOG_MINOR,
171 .name = "watchdog",
172 .fops = &harddog_fops,
173};
174module_misc_device(harddog_miscdev);
175

source code of linux/arch/um/drivers/harddog_kern.c