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_LICENSE("GPL");
53
54static DEFINE_MUTEX(harddog_mutex);
55static DEFINE_SPINLOCK(lock);
56static int timer_alive;
57static int harddog_in_fd = -1;
58static int harddog_out_fd = -1;
59
60/*
61 * Allow only one person to hold it open
62 */
63
64static int harddog_open(struct inode *inode, struct file *file)
65{
66 int err = -EBUSY;
67 char *sock = NULL;
68
69 mutex_lock(&harddog_mutex);
70 spin_lock(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(in_fd_ret: &harddog_in_fd, out_fd_ret: &harddog_out_fd, sock);
81 if(err)
82 goto err;
83
84 timer_alive = 1;
85 spin_unlock(lock: &lock);
86 mutex_unlock(lock: &harddog_mutex);
87 return stream_open(inode, filp: file);
88err:
89 spin_unlock(lock: &lock);
90 mutex_unlock(lock: &harddog_mutex);
91 return err;
92}
93
94static int harddog_release(struct inode *inode, struct file *file)
95{
96 /*
97 * Shut off the timer.
98 */
99
100 spin_lock(lock: &lock);
101
102 stop_watchdog(in_fd: harddog_in_fd, out_fd: harddog_out_fd);
103 harddog_in_fd = -1;
104 harddog_out_fd = -1;
105
106 timer_alive=0;
107 spin_unlock(lock: &lock);
108
109 return 0;
110}
111
112static ssize_t harddog_write(struct file *file, const char __user *data, size_t len,
113 loff_t *ppos)
114{
115 /*
116 * Refresh the timer.
117 */
118 if(len)
119 return ping_watchdog(fd: harddog_out_fd);
120 return 0;
121}
122
123static int harddog_ioctl_unlocked(struct file *file,
124 unsigned int cmd, unsigned long arg)
125{
126 void __user *argp= (void __user *)arg;
127 static struct watchdog_info ident = {
128 WDIOC_SETTIMEOUT,
129 0,
130 "UML Hardware Watchdog"
131 };
132 switch (cmd) {
133 default:
134 return -ENOTTY;
135 case WDIOC_GETSUPPORT:
136 if(copy_to_user(to: argp, from: &ident, n: sizeof(ident)))
137 return -EFAULT;
138 return 0;
139 case WDIOC_GETSTATUS:
140 case WDIOC_GETBOOTSTATUS:
141 return put_user(0,(int __user *)argp);
142 case WDIOC_KEEPALIVE:
143 return ping_watchdog(fd: harddog_out_fd);
144 }
145}
146
147static long harddog_ioctl(struct file *file,
148 unsigned int cmd, unsigned long arg)
149{
150 long ret;
151
152 mutex_lock(&harddog_mutex);
153 ret = harddog_ioctl_unlocked(file, cmd, arg);
154 mutex_unlock(lock: &harddog_mutex);
155
156 return ret;
157}
158
159static const struct file_operations harddog_fops = {
160 .owner = THIS_MODULE,
161 .write = harddog_write,
162 .unlocked_ioctl = harddog_ioctl,
163 .compat_ioctl = compat_ptr_ioctl,
164 .open = harddog_open,
165 .release = harddog_release,
166 .llseek = no_llseek,
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