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 */
32 static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
33 module_param(soft_margin, uint, 0);
34 MODULE_PARM_DESC(soft_margin,
35 "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
36 __MODULE_STRING(TIMER_MARGIN) ")");
37
38 static bool nowayout = WATCHDOG_NOWAYOUT;
39 module_param(nowayout, bool, 0);
40 MODULE_PARM_DESC(nowayout,
41 "Watchdog cannot be stopped once started (default="
42 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
43
44 static int soft_noboot;
45 module_param(soft_noboot, int, 0);
46 MODULE_PARM_DESC(soft_noboot,
47 "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");
48
49 static int soft_panic;
50 module_param(soft_panic, int, 0);
51 MODULE_PARM_DESC(soft_panic,
52 "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
53
54 static char *soft_reboot_cmd;
55 module_param(soft_reboot_cmd, charp, 0000);
56 MODULE_PARM_DESC(soft_reboot_cmd,
57 "Set reboot command. Emergency reboot takes place if unset");
58
59 static bool soft_active_on_boot;
60 module_param(soft_active_on_boot, bool, 0000);
61 MODULE_PARM_DESC(soft_active_on_boot,
62 "Set to true to active Softdog on boot (default=false)");
63
64 static struct hrtimer softdog_ticktock;
65 static struct hrtimer softdog_preticktock;
66
reboot_kthread_fn(void * data)67 static int reboot_kthread_fn(void *data)
68 {
69 kernel_restart(soft_reboot_cmd);
70 return -EPERM; /* Should not reach here */
71 }
72
reboot_work_fn(struct work_struct * unused)73 static void reboot_work_fn(struct work_struct *unused)
74 {
75 kthread_run(reboot_kthread_fn, NULL, "softdog_reboot");
76 }
77
softdog_fire(struct hrtimer * timer)78 static 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
124 static struct watchdog_device softdog_dev;
125
softdog_pretimeout(struct hrtimer * timer)126 static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer)
127 {
128 watchdog_notify_pretimeout(&softdog_dev);
129
130 return HRTIMER_NORESTART;
131 }
132
softdog_ping(struct watchdog_device * w)133 static 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
softdog_stop(struct watchdog_device * w)152 static 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
163 static struct watchdog_info softdog_info = {
164 .identity = "Software Watchdog",
165 .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
166 };
167
168 static const struct watchdog_ops softdog_ops = {
169 .owner = THIS_MODULE,
170 .start = softdog_ping,
171 .stop = softdog_stop,
172 };
173
174 static 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
softdog_init(void)182 static 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 }
214 module_init(softdog_init);
215
softdog_exit(void)216 static void __exit softdog_exit(void)
217 {
218 watchdog_unregister_device(&softdog_dev);
219 }
220 module_exit(softdog_exit);
221
222 MODULE_AUTHOR("Alan Cox");
223 MODULE_DESCRIPTION("Software Watchdog Device Driver");
224 MODULE_LICENSE("GPL");
225