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 | |
67 | static int reboot_kthread_fn(void *data) |
68 | { |
69 | kernel_restart(cmd: soft_reboot_cmd); |
70 | return -EPERM; /* Should not reach here */ |
71 | } |
72 | |
73 | static void reboot_work_fn(struct work_struct *unused) |
74 | { |
75 | kthread_run(reboot_kthread_fn, NULL, "softdog_reboot" ); |
76 | } |
77 | |
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(fmt: "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(work: &reboot_work); |
112 | hrtimer_add_expires_ns(timer, |
113 | ns: (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 | |
126 | static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer) |
127 | { |
128 | watchdog_notify_pretimeout(wdd: &softdog_dev); |
129 | |
130 | return HRTIMER_NORESTART; |
131 | } |
132 | |
133 | static int softdog_ping(struct watchdog_device *w) |
134 | { |
135 | if (!hrtimer_active(timer: &softdog_ticktock)) |
136 | __module_get(THIS_MODULE); |
137 | hrtimer_start(timer: &softdog_ticktock, tim: ktime_set(secs: w->timeout, nsecs: 0), |
138 | mode: HRTIMER_MODE_REL); |
139 | |
140 | if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) { |
141 | if (w->pretimeout) |
142 | hrtimer_start(timer: &softdog_preticktock, |
143 | tim: ktime_set(secs: w->timeout - w->pretimeout, nsecs: 0), |
144 | mode: HRTIMER_MODE_REL); |
145 | else |
146 | hrtimer_cancel(timer: &softdog_preticktock); |
147 | } |
148 | |
149 | return 0; |
150 | } |
151 | |
152 | static int softdog_stop(struct watchdog_device *w) |
153 | { |
154 | if (hrtimer_cancel(timer: &softdog_ticktock)) |
155 | module_put(THIS_MODULE); |
156 | |
157 | if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) |
158 | hrtimer_cancel(timer: &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 | |
182 | static int __init softdog_init(void) |
183 | { |
184 | int ret; |
185 | |
186 | watchdog_init_timeout(wdd: &softdog_dev, timeout_parm: soft_margin, NULL); |
187 | watchdog_set_nowayout(wdd: &softdog_dev, nowayout); |
188 | watchdog_stop_on_reboot(wdd: &softdog_dev); |
189 | |
190 | hrtimer_init(timer: &softdog_ticktock, CLOCK_MONOTONIC, mode: 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(timer: &softdog_preticktock, CLOCK_MONOTONIC, |
196 | mode: HRTIMER_MODE_REL); |
197 | softdog_preticktock.function = softdog_pretimeout; |
198 | } |
199 | |
200 | if (soft_active_on_boot) |
201 | softdog_ping(w: &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 | |
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 | |