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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * SoftDog: A Software Watchdog Device
4 *
5 * (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
6 * All Rights Reserved.
7 *
8 * Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
9 * warranty for any of this software. This material is provided
10 * "AS-IS" and at no charge.
11 *
12 * (c) Copyright 1995 Alan Cox <alan@lxorguk.ukuu.org.uk>
13 *
14 * Software only watchdog driver. Unlike its big brother the WDT501P
15 * driver this won't always recover a failed machine.
16 */
17
18#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
19
20#include <linux/hrtimer.h>
21#include <linux/init.h>
22#include <linux/kernel.h>
23#include <linux/kthread.h>
24#include <linux/module.h>
25#include <linux/moduleparam.h>
26#include <linux/reboot.h>
27#include <linux/types.h>
28#include <linux/watchdog.h>
29#include <linux/workqueue.h>
30
31#define TIMER_MARGIN 60 /* Default is 60 seconds */
32static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
33module_param(soft_margin, uint, 0);
34MODULE_PARM_DESC(soft_margin,
35 "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
36 __MODULE_STRING(TIMER_MARGIN) ")");
37
38static bool nowayout = WATCHDOG_NOWAYOUT;
39module_param(nowayout, bool, 0);
40MODULE_PARM_DESC(nowayout,
41 "Watchdog cannot be stopped once started (default="
42 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
43
44static int soft_noboot;
45module_param(soft_noboot, int, 0);
46MODULE_PARM_DESC(soft_noboot,
47 "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");
48
49static int soft_panic;
50module_param(soft_panic, int, 0);
51MODULE_PARM_DESC(soft_panic,
52 "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
53
54static char *soft_reboot_cmd;
55module_param(soft_reboot_cmd, charp, 0000);
56MODULE_PARM_DESC(soft_reboot_cmd,
57 "Set reboot command. Emergency reboot takes place if unset");
58
59static bool soft_active_on_boot;
60module_param(soft_active_on_boot, bool, 0000);
61MODULE_PARM_DESC(soft_active_on_boot,
62 "Set to true to active Softdog on boot (default=false)");
63
64static struct hrtimer softdog_ticktock;
65static struct hrtimer softdog_preticktock;
66
67static int reboot_kthread_fn(void *data)
68{
69 kernel_restart(soft_reboot_cmd);
70 return -EPERM; /* Should not reach here */
71}
72
73static void reboot_work_fn(struct work_struct *unused)
74{
75 kthread_run(reboot_kthread_fn, NULL, "softdog_reboot");
76}
77
78static enum hrtimer_restart softdog_fire(struct hrtimer *timer)
79{
80 static bool soft_reboot_fired;
81
82 module_put(THIS_MODULE);
83 if (soft_noboot) {
84 pr_crit("Triggered - Reboot ignored\n");
85 } else if (soft_panic) {
86 pr_crit("Initiating panic\n");
87 panic("Software Watchdog Timer expired");
88 } else {
89 pr_crit("Initiating system reboot\n");
90 if (!soft_reboot_fired && soft_reboot_cmd != NULL) {
91 static DECLARE_WORK(reboot_work, reboot_work_fn);
92 /*
93 * The 'kernel_restart' is a 'might-sleep' operation.
94 * Also, executing it in system-wide workqueues blocks
95 * any driver from using the same workqueue in its
96 * shutdown callback function. Thus, we should execute
97 * the 'kernel_restart' in a standalone kernel thread.
98 * But since starting a kernel thread is also a
99 * 'might-sleep' operation, so the 'reboot_work' is
100 * required as a launcher of the kernel thread.
101 *
102 * After request the reboot, restart the timer to
103 * schedule an 'emergency_restart' reboot after
104 * 'TIMER_MARGIN' seconds. It's because if the softdog
105 * hangs, it might be because of scheduling issues. And
106 * if that is the case, both 'schedule_work' and
107 * 'kernel_restart' may possibly be malfunctional at the
108 * same time.
109 */
110 soft_reboot_fired = true;
111 schedule_work(&reboot_work);
112 hrtimer_add_expires_ns(timer,
113 (u64)TIMER_MARGIN * NSEC_PER_SEC);
114
115 return HRTIMER_RESTART;
116 }
117 emergency_restart();
118 pr_crit("Reboot didn't ?????\n");
119 }
120
121 return HRTIMER_NORESTART;
122}
123
124static struct watchdog_device softdog_dev;
125
126static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer)
127{
128 watchdog_notify_pretimeout(&softdog_dev);
129
130 return HRTIMER_NORESTART;
131}
132
133static int softdog_ping(struct watchdog_device *w)
134{
135 if (!hrtimer_active(&softdog_ticktock))
136 __module_get(THIS_MODULE);
137 hrtimer_start(&softdog_ticktock, ktime_set(w->timeout, 0),
138 HRTIMER_MODE_REL);
139
140 if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
141 if (w->pretimeout)
142 hrtimer_start(&softdog_preticktock,
143 ktime_set(w->timeout - w->pretimeout, 0),
144 HRTIMER_MODE_REL);
145 else
146 hrtimer_cancel(&softdog_preticktock);
147 }
148
149 return 0;
150}
151
152static int softdog_stop(struct watchdog_device *w)
153{
154 if (hrtimer_cancel(&softdog_ticktock))
155 module_put(THIS_MODULE);
156
157 if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT))
158 hrtimer_cancel(&softdog_preticktock);
159
160 return 0;
161}
162
163static struct watchdog_info softdog_info = {
164 .identity = "Software Watchdog",
165 .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
166};
167
168static const struct watchdog_ops softdog_ops = {
169 .owner = THIS_MODULE,
170 .start = softdog_ping,
171 .stop = softdog_stop,
172};
173
174static struct watchdog_device softdog_dev = {
175 .info = &softdog_info,
176 .ops = &softdog_ops,
177 .min_timeout = 1,
178 .max_timeout = 65535,
179 .timeout = TIMER_MARGIN,
180};
181
182static int __init softdog_init(void)
183{
184 int ret;
185
186 watchdog_init_timeout(&softdog_dev, soft_margin, NULL);
187 watchdog_set_nowayout(&softdog_dev, nowayout);
188 watchdog_stop_on_reboot(&softdog_dev);
189
190 hrtimer_init(&softdog_ticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
191 softdog_ticktock.function = softdog_fire;
192
193 if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
194 softdog_info.options |= WDIOF_PRETIMEOUT;
195 hrtimer_init(&softdog_preticktock, CLOCK_MONOTONIC,
196 HRTIMER_MODE_REL);
197 softdog_preticktock.function = softdog_pretimeout;
198 }
199
200 if (soft_active_on_boot)
201 softdog_ping(&softdog_dev);
202
203 ret = watchdog_register_device(&softdog_dev);
204 if (ret)
205 return ret;
206
207 pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
208 soft_noboot, softdog_dev.timeout, soft_panic, nowayout);
209 pr_info(" soft_reboot_cmd=%s soft_active_on_boot=%d\n",
210 soft_reboot_cmd ?: "<not set>", soft_active_on_boot);
211
212 return 0;
213}
214module_init(softdog_init);
215
216static void __exit softdog_exit(void)
217{
218 watchdog_unregister_device(&softdog_dev);
219}
220module_exit(softdog_exit);
221
222MODULE_AUTHOR("Alan Cox");
223MODULE_DESCRIPTION("Software Watchdog Device Driver");
224MODULE_LICENSE("GPL");
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 */
56static int soft_margin = TIMER_MARGIN; /* in seconds */
57module_param(soft_margin, int, 0);
58MODULE_PARM_DESC(soft_margin,
59 "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
60 __MODULE_STRING(TIMER_MARGIN) ")");
61
62static int nowayout = WATCHDOG_NOWAYOUT;
63module_param(nowayout, int, 0);
64MODULE_PARM_DESC(nowayout,
65 "Watchdog cannot be stopped once started (default="
66 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
67
68#ifdef ONLY_TESTING
69static int soft_noboot = 1;
70#else
71static int soft_noboot = 0;
72#endif /* ONLY_TESTING */
73
74module_param(soft_noboot, int, 0);
75MODULE_PARM_DESC(soft_noboot,
76 "Softdog action, set to 1 to ignore reboots, 0 to reboot "
77 "(default depends on ONLY_TESTING)");
78
79static int soft_panic;
80module_param(soft_panic, int, 0);
81MODULE_PARM_DESC(soft_panic,
82 "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
83
84/*
85 * Our timer
86 */
87
88static void watchdog_fire(unsigned long);
89
90static struct timer_list watchdog_ticktock =
91 TIMER_INITIALIZER(watchdog_fire, 0, 0);
92static unsigned long driver_open, orphan_timer;
93static char expect_close;
94
95
96/*
97 * If the timer expires..
98 */
99
100static 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
121static int softdog_keepalive(void)
122{
123 mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
124 return 0;
125}
126
127static int softdog_stop(void)
128{
129 del_timer(&watchdog_ticktock);
130 return 0;
131}
132
133static 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
146static 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
159static 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
179static 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
206static 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
246static 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
259static 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
268static struct miscdevice softdog_miscdev = {
269 .minor = WATCHDOG_MINOR,
270 .name = "watchdog",
271 .fops = &softdog_fops,
272};
273
274static struct notifier_block softdog_notifier = {
275 .notifier_call = softdog_notify_sys,
276};
277
278static 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
282static 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
316static void __exit watchdog_exit(void)
317{
318 misc_deregister(&softdog_miscdev);
319 unregister_reboot_notifier(&softdog_notifier);
320}
321
322module_init(watchdog_init);
323module_exit(watchdog_exit);
324
325MODULE_AUTHOR("Alan Cox");
326MODULE_DESCRIPTION("Software Watchdog Device Driver");
327MODULE_LICENSE("GPL");
328MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);