1/*
2 *	SoftDog	0.07:	A Software Watchdog Device
3 *
4 *	(c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
5 *				http://www.redhat.com
6 *
7 *	This program is free software; you can redistribute it and/or
8 *	modify it under the terms of the GNU General Public License
9 *	as published by the Free Software Foundation; either version
10 *	2 of the License, or (at your option) any later version.
11 *
12 *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
13 *	warranty for any of this software. This material is provided
14 *	"AS-IS" and at no charge.
15 *
16 *	(c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
17 *
18 *	Software only watchdog driver. Unlike its big brother the WDT501P
19 *	driver this won't always recover a failed machine.
20 *
21 *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
22 *	Modularised.
23 *	Added soft_margin; use upon insmod to change the timer delay.
24 *	NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
25 *	    minors.
26 *
27 *  19980911 Alan Cox
28 *	Made SMP safe for 2.3.x
29 *
30 *  20011127 Joel Becker (jlbec@evilplan.org>
31 *	Added soft_noboot; Allows testing the softdog trigger without
32 *	requiring a recompile.
33 *	Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
34 *
35 *  20020530 Joel Becker <joel.becker@oracle.com>
36 *  	Added Matt Domsch's nowayout module option.
37 */
38
39#include <linux/module.h>
40#include <linux/moduleparam.h>
41#include <linux/types.h>
42#include <linux/timer.h>
43#include <linux/miscdevice.h>
44#include <linux/watchdog.h>
45#include <linux/fs.h>
46#include <linux/notifier.h>
47#include <linux/reboot.h>
48#include <linux/init.h>
49#include <linux/jiffies.h>
50
51#include <asm/uaccess.h>
52
53#define PFX "SoftDog: "
54
55#define TIMER_MARGIN	60		/* Default is 60 seconds */
56static int soft_margin = TIMER_MARGIN;	/* in seconds */
57module_param(soft_margin, int, 0);
58MODULE_PARM_DESC(soft_margin, "Watchdog soft_margin in seconds. (0<soft_margin<65536, default=" __MODULE_STRING(TIMER_MARGIN) ")");
59
60static int nowayout = WATCHDOG_NOWAYOUT;
61module_param(nowayout, int, 0);
62MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
63
64#ifdef ONLY_TESTING
65static int soft_noboot = 1;
66#else
67static int soft_noboot = 0;
68#endif  /* ONLY_TESTING */
69
70module_param(soft_noboot, int, 0);
71MODULE_PARM_DESC(soft_noboot, "Softdog action, set to 1 to ignore reboots, 0 to reboot (default depends on ONLY_TESTING)");
72
73/*
74 *	Our timer
75 */
76
77static void watchdog_fire(unsigned long);
78
79static struct timer_list watchdog_ticktock =
80		TIMER_INITIALIZER(watchdog_fire, 0, 0);
81static unsigned long driver_open, orphan_timer;
82static char expect_close;
83
84
85/*
86 *	If the timer expires..
87 */
88
89static void watchdog_fire(unsigned long data)
90{
91	if (test_and_clear_bit(0, &orphan_timer))
92		module_put(THIS_MODULE);
93
94	if (soft_noboot)
95		printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
96	else
97	{
98		printk(KERN_CRIT PFX "Initiating system reboot.\n");
99		emergency_restart();
100		printk(KERN_CRIT PFX "Reboot didn't ?????\n");
101	}
102}
103
104/*
105 *	Softdog operations
106 */
107
108static int softdog_keepalive(void)
109{
110	mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
111	return 0;
112}
113
114static int softdog_stop(void)
115{
116	del_timer(&watchdog_ticktock);
117	return 0;
118}
119
120static int softdog_set_heartbeat(int t)
121{
122	if ((t < 0x0001) || (t > 0xFFFF))
123		return -EINVAL;
124
125	soft_margin = t;
126	return 0;
127}
128
129/*
130 *	/dev/watchdog handling
131 */
132
133static int softdog_open(struct inode *inode, struct file *file)
134{
135	if (test_and_set_bit(0, &driver_open))
136		return -EBUSY;
137	if (!test_and_clear_bit(0, &orphan_timer))
138		__module_get(THIS_MODULE);
139	/*
140	 *	Activate timer
141	 */
142	softdog_keepalive();
143	return nonseekable_open(inode, file);
144}
145
146static int softdog_release(struct inode *inode, struct file *file)
147{
148	/*
149	 *	Shut off the timer.
150	 * 	Lock it in if it's a module and we set nowayout
151	 */
152	if (expect_close == 42) {
153		softdog_stop();
154		module_put(THIS_MODULE);
155	} else {
156		printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
157		set_bit(0, &orphan_timer);
158		softdog_keepalive();
159	}
160	clear_bit(0, &driver_open);
161	expect_close = 0;
162	return 0;
163}
164
165static ssize_t softdog_write(struct file *file, const char __user *data, size_t len, loff_t *ppos)
166{
167	/*
168	 *	Refresh the timer.
169	 */
170	if(len) {
171		if (!nowayout) {
172			size_t i;
173
174			/* In case it was set long ago */
175			expect_close = 0;
176
177			for (i = 0; i != len; i++) {
178				char c;
179
180				if (get_user(c, data + i))
181					return -EFAULT;
182				if (c == 'V')
183					expect_close = 42;
184			}
185		}
186		softdog_keepalive();
187	}
188	return len;
189}
190
191static int softdog_ioctl(struct inode *inode, struct file *file,
192	unsigned int cmd, unsigned long arg)
193{
194	void __user *argp = (void __user *)arg;
195	int __user *p = argp;
196	int new_margin;
197	static struct watchdog_info ident = {
198		.options =		WDIOF_SETTIMEOUT |
199					WDIOF_KEEPALIVEPING |
200					WDIOF_MAGICCLOSE,
201		.firmware_version =	0,
202		.identity =		"Software Watchdog",
203	};
204	switch (cmd) {
205		default:
206			return -ENOTTY;
207		case WDIOC_GETSUPPORT:
208			return copy_to_user(argp, &ident,
209				sizeof(ident)) ? -EFAULT : 0;
210		case WDIOC_GETSTATUS:
211		case WDIOC_GETBOOTSTATUS:
212			return put_user(0, p);
213		case WDIOC_KEEPALIVE:
214			softdog_keepalive();
215			return 0;
216		case WDIOC_SETTIMEOUT:
217			if (get_user(new_margin, p))
218				return -EFAULT;
219			if (softdog_set_heartbeat(new_margin))
220				return -EINVAL;
221			softdog_keepalive();
222			/* Fall */
223		case WDIOC_GETTIMEOUT:
224			return put_user(soft_margin, p);
225	}
226}
227
228/*
229 *	Notifier for system down
230 */
231
232static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
233	void *unused)
234{
235	if(code==SYS_DOWN || code==SYS_HALT) {
236		/* Turn the WDT off */
237		softdog_stop();
238	}
239	return NOTIFY_DONE;
240}
241
242/*
243 *	Kernel Interfaces
244 */
245
246static const struct file_operations softdog_fops = {
247	.owner		= THIS_MODULE,
248	.llseek		= no_llseek,
249	.write		= softdog_write,
250	.ioctl		= softdog_ioctl,
251	.open		= softdog_open,
252	.release	= softdog_release,
253};
254
255static struct miscdevice softdog_miscdev = {
256	.minor		= WATCHDOG_MINOR,
257	.name		= "watchdog",
258	.fops		= &softdog_fops,
259};
260
261static struct notifier_block softdog_notifier = {
262	.notifier_call	= softdog_notify_sys,
263};
264
265static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n";
266
267static int __init watchdog_init(void)
268{
269	int ret;
270
271	/* Check that the soft_margin value is within it's range ; if not reset to the default */
272	if (softdog_set_heartbeat(soft_margin)) {
273		softdog_set_heartbeat(TIMER_MARGIN);
274		printk(KERN_INFO PFX "soft_margin value must be 0<soft_margin<65536, using %d\n",
275			TIMER_MARGIN);
276	}
277
278	ret = register_reboot_notifier(&softdog_notifier);
279	if (ret) {
280		printk (KERN_ERR PFX "cannot register reboot notifier (err=%d)\n",
281			ret);
282		return ret;
283	}
284
285	ret = misc_register(&softdog_miscdev);
286	if (ret) {
287		printk (KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",
288			WATCHDOG_MINOR, ret);
289		unregister_reboot_notifier(&softdog_notifier);
290		return ret;
291	}
292
293	printk(banner, soft_noboot, soft_margin, nowayout);
294
295	return 0;
296}
297
298static void __exit watchdog_exit(void)
299{
300	misc_deregister(&softdog_miscdev);
301	unregister_reboot_notifier(&softdog_notifier);
302}
303
304module_init(watchdog_init);
305module_exit(watchdog_exit);
306
307MODULE_AUTHOR("Alan Cox");
308MODULE_DESCRIPTION("Software Watchdog Device Driver");
309MODULE_LICENSE("GPL");
310MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
311