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 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 74 static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer) 75 { 76 watchdog_notify_pretimeout(&softdog_dev); 77 78 return HRTIMER_NORESTART; 79 } 80 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 } 99 100 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 }; 129 130 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); 158 159 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