watchdog: nowayout is bool
[linux-2.6.git] / drivers / watchdog / softdog.c
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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
40
41 #include <linux/module.h>
42 #include <linux/moduleparam.h>
43 #include <linux/types.h>
44 #include <linux/timer.h>
45 #include <linux/miscdevice.h>
46 #include <linux/watchdog.h>
47 #include <linux/fs.h>
48 #include <linux/notifier.h>
49 #include <linux/reboot.h>
50 #include <linux/init.h>
51 #include <linux/jiffies.h>
52 #include <linux/uaccess.h>
53 #include <linux/kernel.h>
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 bool nowayout = WATCHDOG_NOWAYOUT;
63 module_param(nowayout, bool, 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
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                 pr_crit("Triggered - Reboot ignored\n");
107         else if (soft_panic) {
108                 pr_crit("Initiating panic\n");
109                 panic("Software Watchdog Timer expired");
110         } else {
111                 pr_crit("Initiating system reboot\n");
112                 emergency_restart();
113                 pr_crit("Reboot didn't ?????\n");
114         }
115 }
116
117 /*
118  *      Softdog operations
119  */
120
121 static int softdog_keepalive(void)
122 {
123         mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
124         return 0;
125 }
126
127 static int softdog_stop(void)
128 {
129         del_timer(&watchdog_ticktock);
130         return 0;
131 }
132
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
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
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                 pr_crit("Unexpected close, not stopping watchdog!\n");
170                 set_bit(0, &orphan_timer);
171                 softdog_keepalive();
172         }
173         clear_bit(0, &driver_open);
174         expect_close = 0;
175         return 0;
176 }
177
178 static ssize_t softdog_write(struct file *file, const char __user *data,
179                                                 size_t len, loff_t *ppos)
180 {
181         /*
182          *      Refresh the timer.
183          */
184         if (len) {
185                 if (!nowayout) {
186                         size_t i;
187
188                         /* In case it was set long ago */
189                         expect_close = 0;
190
191                         for (i = 0; i != len; i++) {
192                                 char c;
193
194                                 if (get_user(c, data + i))
195                                         return -EFAULT;
196                                 if (c == 'V')
197                                         expect_close = 42;
198                         }
199                 }
200                 softdog_keepalive();
201         }
202         return len;
203 }
204
205 static long softdog_ioctl(struct file *file, unsigned int cmd,
206                                                         unsigned long arg)
207 {
208         void __user *argp = (void __user *)arg;
209         int __user *p = argp;
210         int new_margin;
211         static const struct watchdog_info ident = {
212                 .options =              WDIOF_SETTIMEOUT |
213                                         WDIOF_KEEPALIVEPING |
214                                         WDIOF_MAGICCLOSE,
215                 .firmware_version =     0,
216                 .identity =             "Software Watchdog",
217         };
218         switch (cmd) {
219         case WDIOC_GETSUPPORT:
220                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
221         case WDIOC_GETSTATUS:
222         case WDIOC_GETBOOTSTATUS:
223                 return put_user(0, p);
224         case WDIOC_KEEPALIVE:
225                 softdog_keepalive();
226                 return 0;
227         case WDIOC_SETTIMEOUT:
228                 if (get_user(new_margin, p))
229                         return -EFAULT;
230                 if (softdog_set_heartbeat(new_margin))
231                         return -EINVAL;
232                 softdog_keepalive();
233                 /* Fall */
234         case WDIOC_GETTIMEOUT:
235                 return put_user(soft_margin, p);
236         default:
237                 return -ENOTTY;
238         }
239 }
240
241 /*
242  *      Notifier for system down
243  */
244
245 static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
246         void *unused)
247 {
248         if (code == SYS_DOWN || code == SYS_HALT)
249                 /* Turn the WDT off */
250                 softdog_stop();
251         return NOTIFY_DONE;
252 }
253
254 /*
255  *      Kernel Interfaces
256  */
257
258 static const struct file_operations softdog_fops = {
259         .owner          = THIS_MODULE,
260         .llseek         = no_llseek,
261         .write          = softdog_write,
262         .unlocked_ioctl = softdog_ioctl,
263         .open           = softdog_open,
264         .release        = softdog_release,
265 };
266
267 static struct miscdevice softdog_miscdev = {
268         .minor          = WATCHDOG_MINOR,
269         .name           = "watchdog",
270         .fops           = &softdog_fops,
271 };
272
273 static struct notifier_block softdog_notifier = {
274         .notifier_call  = softdog_notify_sys,
275 };
276
277 static int __init watchdog_init(void)
278 {
279         int ret;
280
281         /* Check that the soft_margin value is within it's range;
282            if not reset to the default */
283         if (softdog_set_heartbeat(soft_margin)) {
284                 softdog_set_heartbeat(TIMER_MARGIN);
285                 pr_info("soft_margin must be 0 < soft_margin < 65536, using %d\n",
286                         TIMER_MARGIN);
287         }
288
289         ret = register_reboot_notifier(&softdog_notifier);
290         if (ret) {
291                 pr_err("cannot register reboot notifier (err=%d)\n", ret);
292                 return ret;
293         }
294
295         ret = misc_register(&softdog_miscdev);
296         if (ret) {
297                 pr_err("cannot register miscdev on minor=%d (err=%d)\n",
298                        WATCHDOG_MINOR, ret);
299                 unregister_reboot_notifier(&softdog_notifier);
300                 return ret;
301         }
302
303         pr_info("Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout= %d)\n",
304                 soft_noboot, soft_margin, soft_panic, nowayout);
305
306         return 0;
307 }
308
309 static void __exit watchdog_exit(void)
310 {
311         misc_deregister(&softdog_miscdev);
312         unregister_reboot_notifier(&softdog_notifier);
313 }
314
315 module_init(watchdog_init);
316 module_exit(watchdog_exit);
317
318 MODULE_AUTHOR("Alan Cox");
319 MODULE_DESCRIPTION("Software Watchdog Device Driver");
320 MODULE_LICENSE("GPL");
321 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);