1 files changed, 224 insertions, 0 deletions
diff --git a/drivers/watchdog/softdog.c b/drivers/watchdog/softdog.c
new file mode 100644
index 000000000..7a1096265
--- /dev/null
+++ b/drivers/watchdog/softdog.c
@@ -0,0 +1,224 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *	SoftDog:	A Software Watchdog Device
+ *
+ *	(c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
+ *							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 <alan@lxorguk.ukuu.org.uk>
+ *
+ *	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 <linux/hrtimer.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/reboot.h>
+#include <linux/types.h>
+#include <linux/watchdog.h>
+#include <linux/workqueue.h>
+
+#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 ?: "<not set>", 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");