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/module.h>
24 #include <linux/moduleparam.h>
25 #include <linux/reboot.h>
26 #include <linux/types.h>
27 #include <linux/watchdog.h>
28
29 #define TIMER_MARGIN 60 /* Default is 60 seconds */
30 static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
31 module_param(soft_margin, uint, 0);
32 MODULE_PARM_DESC(soft_margin,
33 "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
34 __MODULE_STRING(TIMER_MARGIN) ")");
35
36 static bool nowayout = WATCHDOG_NOWAYOUT;
37 module_param(nowayout, bool, 0);
38 MODULE_PARM_DESC(nowayout,
39 "Watchdog cannot be stopped once started (default="
40 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
41
42 static int soft_noboot;
43 module_param(soft_noboot, int, 0);
44 MODULE_PARM_DESC(soft_noboot,
45 "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");
46
47 static int soft_panic;
48 module_param(soft_panic, int, 0);
49 MODULE_PARM_DESC(soft_panic,
50 "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
51
52 static struct hrtimer softdog_ticktock;
53 static struct hrtimer softdog_preticktock;
54
softdog_fire(struct hrtimer * timer)55 static enum hrtimer_restart softdog_fire(struct hrtimer *timer)
56 {
57 module_put(THIS_MODULE);
58 if (soft_noboot) {
59 pr_crit("Triggered - Reboot ignored\n");
60 } else if (soft_panic) {
61 pr_crit("Initiating panic\n");
62 panic("Software Watchdog Timer expired");
63 } else {
64 pr_crit("Initiating system reboot\n");
65 emergency_restart();
66 pr_crit("Reboot didn't ?????\n");
67 }
68
69 return HRTIMER_NORESTART;
70 }
71
72 static struct watchdog_device softdog_dev;
73
softdog_pretimeout(struct hrtimer * timer)74 static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer)
75 {
76 watchdog_notify_pretimeout(&softdog_dev);
77
78 return HRTIMER_NORESTART;
79 }
80
softdog_ping(struct watchdog_device * w)81 static int softdog_ping(struct watchdog_device *w)
82 {
83 if (!hrtimer_active(&softdog_ticktock))
84 __module_get(THIS_MODULE);
85 hrtimer_start(&softdog_ticktock, ktime_set(w->timeout, 0),
86 HRTIMER_MODE_REL);
87
88 if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
89 if (w->pretimeout)
90 hrtimer_start(&softdog_preticktock,
91 ktime_set(w->timeout - w->pretimeout, 0),
92 HRTIMER_MODE_REL);
93 else
94 hrtimer_cancel(&softdog_preticktock);
95 }
96
97 return 0;
98 }
99
softdog_stop(struct watchdog_device * w)100 static int softdog_stop(struct watchdog_device *w)
101 {
102 if (hrtimer_cancel(&softdog_ticktock))
103 module_put(THIS_MODULE);
104
105 if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT))
106 hrtimer_cancel(&softdog_preticktock);
107
108 return 0;
109 }
110
111 static struct watchdog_info softdog_info = {
112 .identity = "Software Watchdog",
113 .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
114 };
115
116 static const struct watchdog_ops softdog_ops = {
117 .owner = THIS_MODULE,
118 .start = softdog_ping,
119 .stop = softdog_stop,
120 };
121
122 static struct watchdog_device softdog_dev = {
123 .info = &softdog_info,
124 .ops = &softdog_ops,
125 .min_timeout = 1,
126 .max_timeout = 65535,
127 .timeout = TIMER_MARGIN,
128 };
129
softdog_init(void)130 static int __init softdog_init(void)
131 {
132 int ret;
133
134 watchdog_init_timeout(&softdog_dev, soft_margin, NULL);
135 watchdog_set_nowayout(&softdog_dev, nowayout);
136 watchdog_stop_on_reboot(&softdog_dev);
137
138 hrtimer_init(&softdog_ticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
139 softdog_ticktock.function = softdog_fire;
140
141 if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
142 softdog_info.options |= WDIOF_PRETIMEOUT;
143 hrtimer_init(&softdog_preticktock, CLOCK_MONOTONIC,
144 HRTIMER_MODE_REL);
145 softdog_preticktock.function = softdog_pretimeout;
146 }
147
148 ret = watchdog_register_device(&softdog_dev);
149 if (ret)
150 return ret;
151
152 pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
153 soft_noboot, softdog_dev.timeout, soft_panic, nowayout);
154
155 return 0;
156 }
157 module_init(softdog_init);
158
softdog_exit(void)159 static void __exit softdog_exit(void)
160 {
161 watchdog_unregister_device(&softdog_dev);
162 }
163 module_exit(softdog_exit);
164
165 MODULE_AUTHOR("Alan Cox");
166 MODULE_DESCRIPTION("Software Watchdog Device Driver");
167 MODULE_LICENSE("GPL");
168