// SPDX-License-Identifier: GPL-2.0+ /* * SoftDog: A Software Watchdog Device * * (c) Copyright 1996 Alan Cox , * All Rights Reserved. * * Neither Alan Cox nor CymruNet Ltd. admit liability nor provide * warranty for any of this software. This material is provided * "AS-IS" and at no charge. * * (c) Copyright 1995 Alan Cox * * Software only watchdog driver. Unlike its big brother the WDT501P * driver this won't always recover a failed machine. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #define TIMER_MARGIN 60 /* Default is 60 seconds */ static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */ module_param(soft_margin, uint, 0); MODULE_PARM_DESC(soft_margin, "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default=" __MODULE_STRING(TIMER_MARGIN) ")"); static bool nowayout = WATCHDOG_NOWAYOUT; module_param(nowayout, bool, 0); MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); static int soft_noboot; module_param(soft_noboot, int, 0); MODULE_PARM_DESC(soft_noboot, "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)"); static int soft_panic; module_param(soft_panic, int, 0); MODULE_PARM_DESC(soft_panic, "Softdog action, set to 1 to panic, 0 to reboot (default=0)"); static char *soft_reboot_cmd; module_param(soft_reboot_cmd, charp, 0000); MODULE_PARM_DESC(soft_reboot_cmd, "Set reboot command. Emergency reboot takes place if unset"); static bool soft_active_on_boot; module_param(soft_active_on_boot, bool, 0000); MODULE_PARM_DESC(soft_active_on_boot, "Set to true to active Softdog on boot (default=false)"); static struct hrtimer softdog_ticktock; static struct hrtimer softdog_preticktock; static int reboot_kthread_fn(void *data) { kernel_restart(soft_reboot_cmd); return -EPERM; /* Should not reach here */ } static void reboot_work_fn(struct work_struct *unused) { kthread_run(reboot_kthread_fn, NULL, "softdog_reboot"); } static enum hrtimer_restart softdog_fire(struct hrtimer *timer) { static bool soft_reboot_fired; module_put(THIS_MODULE); if (soft_noboot) { pr_crit("Triggered - Reboot ignored\n"); } else if (soft_panic) { pr_crit("Initiating panic\n"); panic("Software Watchdog Timer expired"); } else { pr_crit("Initiating system reboot\n"); if (!soft_reboot_fired && soft_reboot_cmd != NULL) { static DECLARE_WORK(reboot_work, reboot_work_fn); /* * The 'kernel_restart' is a 'might-sleep' operation. * Also, executing it in system-wide workqueues blocks * any driver from using the same workqueue in its * shutdown callback function. Thus, we should execute * the 'kernel_restart' in a standalone kernel thread. * But since starting a kernel thread is also a * 'might-sleep' operation, so the 'reboot_work' is * required as a launcher of the kernel thread. * * After request the reboot, restart the timer to * schedule an 'emergency_restart' reboot after * 'TIMER_MARGIN' seconds. It's because if the softdog * hangs, it might be because of scheduling issues. And * if that is the case, both 'schedule_work' and * 'kernel_restart' may possibly be malfunctional at the * same time. */ soft_reboot_fired = true; schedule_work(&reboot_work); hrtimer_add_expires_ns(timer, (u64)TIMER_MARGIN * NSEC_PER_SEC); return HRTIMER_RESTART; } emergency_restart(); pr_crit("Reboot didn't ?????\n"); } return HRTIMER_NORESTART; } static struct watchdog_device softdog_dev; static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer) { watchdog_notify_pretimeout(&softdog_dev); return HRTIMER_NORESTART; } static int softdog_ping(struct watchdog_device *w) { if (!hrtimer_active(&softdog_ticktock)) __module_get(THIS_MODULE); hrtimer_start(&softdog_ticktock, ktime_set(w->timeout, 0), HRTIMER_MODE_REL); if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) { if (w->pretimeout) hrtimer_start(&softdog_preticktock, ktime_set(w->timeout - w->pretimeout, 0), HRTIMER_MODE_REL); else hrtimer_cancel(&softdog_preticktock); } return 0; } static int softdog_stop(struct watchdog_device *w) { if (hrtimer_cancel(&softdog_ticktock)) module_put(THIS_MODULE); if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) hrtimer_cancel(&softdog_preticktock); return 0; } static struct watchdog_info softdog_info = { .identity = "Software Watchdog", .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE, }; static const struct watchdog_ops softdog_ops = { .owner = THIS_MODULE, .start = softdog_ping, .stop = softdog_stop, }; static struct watchdog_device softdog_dev = { .info = &softdog_info, .ops = &softdog_ops, .min_timeout = 1, .max_timeout = 65535, .timeout = TIMER_MARGIN, }; static int __init softdog_init(void) { int ret; watchdog_init_timeout(&softdog_dev, soft_margin, NULL); watchdog_set_nowayout(&softdog_dev, nowayout); watchdog_stop_on_reboot(&softdog_dev); hrtimer_init(&softdog_ticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL); softdog_ticktock.function = softdog_fire; if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) { softdog_info.options |= WDIOF_PRETIMEOUT; hrtimer_init(&softdog_preticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL); softdog_preticktock.function = softdog_pretimeout; } if (soft_active_on_boot) softdog_ping(&softdog_dev); ret = watchdog_register_device(&softdog_dev); if (ret) return ret; pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n", soft_noboot, softdog_dev.timeout, soft_panic, nowayout); pr_info(" soft_reboot_cmd=%s soft_active_on_boot=%d\n", soft_reboot_cmd ?: "", soft_active_on_boot); return 0; } module_init(softdog_init); static void __exit softdog_exit(void) { watchdog_unregister_device(&softdog_dev); } module_exit(softdog_exit); MODULE_AUTHOR("Alan Cox"); MODULE_DESCRIPTION("Software Watchdog Device Driver"); MODULE_LICENSE("GPL");