1 /*
2 * SoftDog 0.07: A Software Watchdog Device
3 *
4 * (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
5 * All Rights Reserved.
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 #include <linux/uaccess.h>
51 #include <linux/kernel.h>
52
53 #define PFX "SoftDog: "
54
55 #define TIMER_MARGIN 60 /* Default is 60 seconds */
56 static int soft_margin = TIMER_MARGIN; /* in seconds */
57 module_param(soft_margin, int, 0);
58 MODULE_PARM_DESC(soft_margin,
59 "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
60 __MODULE_STRING(TIMER_MARGIN) ")");
61
62 static int nowayout = WATCHDOG_NOWAYOUT;
63 module_param(nowayout, int, 0);
64 MODULE_PARM_DESC(nowayout,
65 "Watchdog cannot be stopped once started (default="
66 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
67
68 #ifdef ONLY_TESTING
69 static int soft_noboot = 1;
70 #else
71 static int soft_noboot = 0;
72 #endif /* ONLY_TESTING */
73
74 module_param(soft_noboot, int, 0);
75 MODULE_PARM_DESC(soft_noboot,
76 "Softdog action, set to 1 to ignore reboots, 0 to reboot "
77 "(default depends on ONLY_TESTING)");
78
79 static int soft_panic;
80 module_param(soft_panic, int, 0);
81 MODULE_PARM_DESC(soft_panic,
82 "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
83
84 /*
85 * Our timer
86 */
87
88 static void watchdog_fire(unsigned long);
89
90 static struct timer_list watchdog_ticktock =
91 TIMER_INITIALIZER(watchdog_fire, 0, 0);
92 static unsigned long driver_open, orphan_timer;
93 static char expect_close;
94
95
96 /*
97 * If the timer expires..
98 */
99
watchdog_fire(unsigned long data)100 static void watchdog_fire(unsigned long data)
101 {
102 if (test_and_clear_bit(0, &orphan_timer))
103 module_put(THIS_MODULE);
104
105 if (soft_noboot)
106 printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
107 else if (soft_panic) {
108 printk(KERN_CRIT PFX "Initiating panic.\n");
109 panic("Software Watchdog Timer expired.");
110 } else {
111 printk(KERN_CRIT PFX "Initiating system reboot.\n");
112 emergency_restart();
113 printk(KERN_CRIT PFX "Reboot didn't ?????\n");
114 }
115 }
116
117 /*
118 * Softdog operations
119 */
120
softdog_keepalive(void)121 static int softdog_keepalive(void)
122 {
123 mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
124 return 0;
125 }
126
softdog_stop(void)127 static int softdog_stop(void)
128 {
129 del_timer(&watchdog_ticktock);
130 return 0;
131 }
132
softdog_set_heartbeat(int t)133 static int softdog_set_heartbeat(int t)
134 {
135 if ((t < 0x0001) || (t > 0xFFFF))
136 return -EINVAL;
137
138 soft_margin = t;
139 return 0;
140 }
141
142 /*
143 * /dev/watchdog handling
144 */
145
softdog_open(struct inode * inode,struct file * file)146 static int softdog_open(struct inode *inode, struct file *file)
147 {
148 if (test_and_set_bit(0, &driver_open))
149 return -EBUSY;
150 if (!test_and_clear_bit(0, &orphan_timer))
151 __module_get(THIS_MODULE);
152 /*
153 * Activate timer
154 */
155 softdog_keepalive();
156 return nonseekable_open(inode, file);
157 }
158
softdog_release(struct inode * inode,struct file * file)159 static int softdog_release(struct inode *inode, struct file *file)
160 {
161 /*
162 * Shut off the timer.
163 * Lock it in if it's a module and we set nowayout
164 */
165 if (expect_close == 42) {
166 softdog_stop();
167 module_put(THIS_MODULE);
168 } else {
169 printk(KERN_CRIT PFX
170 "Unexpected close, not stopping watchdog!\n");
171 set_bit(0, &orphan_timer);
172 softdog_keepalive();
173 }
174 clear_bit(0, &driver_open);
175 expect_close = 0;
176 return 0;
177 }
178
softdog_write(struct file * file,const char __user * data,size_t len,loff_t * ppos)179 static ssize_t softdog_write(struct file *file, const char __user *data,
180 size_t len, loff_t *ppos)
181 {
182 /*
183 * Refresh the timer.
184 */
185 if (len) {
186 if (!nowayout) {
187 size_t i;
188
189 /* In case it was set long ago */
190 expect_close = 0;
191
192 for (i = 0; i != len; i++) {
193 char c;
194
195 if (get_user(c, data + i))
196 return -EFAULT;
197 if (c == 'V')
198 expect_close = 42;
199 }
200 }
201 softdog_keepalive();
202 }
203 return len;
204 }
205
softdog_ioctl(struct file * file,unsigned int cmd,unsigned long arg)206 static long softdog_ioctl(struct file *file, unsigned int cmd,
207 unsigned long arg)
208 {
209 void __user *argp = (void __user *)arg;
210 int __user *p = argp;
211 int new_margin;
212 static const struct watchdog_info ident = {
213 .options = WDIOF_SETTIMEOUT |
214 WDIOF_KEEPALIVEPING |
215 WDIOF_MAGICCLOSE,
216 .firmware_version = 0,
217 .identity = "Software Watchdog",
218 };
219 switch (cmd) {
220 case WDIOC_GETSUPPORT:
221 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
222 case WDIOC_GETSTATUS:
223 case WDIOC_GETBOOTSTATUS:
224 return put_user(0, p);
225 case WDIOC_KEEPALIVE:
226 softdog_keepalive();
227 return 0;
228 case WDIOC_SETTIMEOUT:
229 if (get_user(new_margin, p))
230 return -EFAULT;
231 if (softdog_set_heartbeat(new_margin))
232 return -EINVAL;
233 softdog_keepalive();
234 /* Fall */
235 case WDIOC_GETTIMEOUT:
236 return put_user(soft_margin, p);
237 default:
238 return -ENOTTY;
239 }
240 }
241
242 /*
243 * Notifier for system down
244 */
245
softdog_notify_sys(struct notifier_block * this,unsigned long code,void * unused)246 static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
247 void *unused)
248 {
249 if (code == SYS_DOWN || code == SYS_HALT)
250 /* Turn the WDT off */
251 softdog_stop();
252 return NOTIFY_DONE;
253 }
254
255 /*
256 * Kernel Interfaces
257 */
258
259 static const struct file_operations softdog_fops = {
260 .owner = THIS_MODULE,
261 .llseek = no_llseek,
262 .write = softdog_write,
263 .unlocked_ioctl = softdog_ioctl,
264 .open = softdog_open,
265 .release = softdog_release,
266 };
267
268 static struct miscdevice softdog_miscdev = {
269 .minor = WATCHDOG_MINOR,
270 .name = "watchdog",
271 .fops = &softdog_fops,
272 };
273
274 static struct notifier_block softdog_notifier = {
275 .notifier_call = softdog_notify_sys,
276 };
277
278 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 "
279 "initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d "
280 "(nowayout= %d)\n";
281
watchdog_init(void)282 static int __init watchdog_init(void)
283 {
284 int ret;
285
286 /* Check that the soft_margin value is within it's range;
287 if not reset to the default */
288 if (softdog_set_heartbeat(soft_margin)) {
289 softdog_set_heartbeat(TIMER_MARGIN);
290 printk(KERN_INFO PFX
291 "soft_margin must be 0 < soft_margin < 65536, using %d\n",
292 TIMER_MARGIN);
293 }
294
295 ret = register_reboot_notifier(&softdog_notifier);
296 if (ret) {
297 printk(KERN_ERR PFX
298 "cannot register reboot notifier (err=%d)\n", ret);
299 return ret;
300 }
301
302 ret = misc_register(&softdog_miscdev);
303 if (ret) {
304 printk(KERN_ERR PFX
305 "cannot register miscdev on minor=%d (err=%d)\n",
306 WATCHDOG_MINOR, ret);
307 unregister_reboot_notifier(&softdog_notifier);
308 return ret;
309 }
310
311 printk(banner, soft_noboot, soft_margin, soft_panic, nowayout);
312
313 return 0;
314 }
315
watchdog_exit(void)316 static void __exit watchdog_exit(void)
317 {
318 misc_deregister(&softdog_miscdev);
319 unregister_reboot_notifier(&softdog_notifier);
320 }
321
322 module_init(watchdog_init);
323 module_exit(watchdog_exit);
324
325 MODULE_AUTHOR("Alan Cox");
326 MODULE_DESCRIPTION("Software Watchdog Device Driver");
327 MODULE_LICENSE("GPL");
328 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
329