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(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("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; 125 126 static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer) 127 { 128 watchdog_notify_pretimeout(&softdog_dev); 129 130 return HRTIMER_NORESTART; 131 } 132 133 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 } 151 152 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 }; 181 182 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); 215 216 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