v4.19.13 snapshot.
diff --git a/arch/um/drivers/harddog_kern.c b/arch/um/drivers/harddog_kern.c
new file mode 100644
index 0000000..6d38127
--- /dev/null
+++ b/arch/um/drivers/harddog_kern.c
@@ -0,0 +1,178 @@
+/* UML hardware watchdog, shamelessly stolen from:
+ *
+ * SoftDog 0.05: A Software Watchdog Device
+ *
+ * (c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
+ * http://www.redhat.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * 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.
+ *
+ * 03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
+ * Modularised.
+ * Added soft_margin; use upon insmod to change the timer delay.
+ * NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
+ * minors.
+ *
+ * 19980911 Alan Cox
+ * Made SMP safe for 2.3.x
+ *
+ * 20011127 Joel Becker (jlbec@evilplan.org>
+ * Added soft_noboot; Allows testing the softdog trigger without
+ * requiring a recompile.
+ * Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/miscdevice.h>
+#include <linux/watchdog.h>
+#include <linux/reboot.h>
+#include <linux/mutex.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include "mconsole.h"
+
+MODULE_LICENSE("GPL");
+
+static DEFINE_MUTEX(harddog_mutex);
+static DEFINE_SPINLOCK(lock);
+static int timer_alive;
+static int harddog_in_fd = -1;
+static int harddog_out_fd = -1;
+
+/*
+ * Allow only one person to hold it open
+ */
+
+extern int start_watchdog(int *in_fd_ret, int *out_fd_ret, char *sock);
+
+static int harddog_open(struct inode *inode, struct file *file)
+{
+ int err = -EBUSY;
+ char *sock = NULL;
+
+ mutex_lock(&harddog_mutex);
+ spin_lock(&lock);
+ if(timer_alive)
+ goto err;
+#ifdef CONFIG_WATCHDOG_NOWAYOUT
+ __module_get(THIS_MODULE);
+#endif
+
+#ifdef CONFIG_MCONSOLE
+ sock = mconsole_notify_socket();
+#endif
+ err = start_watchdog(&harddog_in_fd, &harddog_out_fd, sock);
+ if(err)
+ goto err;
+
+ timer_alive = 1;
+ spin_unlock(&lock);
+ mutex_unlock(&harddog_mutex);
+ return nonseekable_open(inode, file);
+err:
+ spin_unlock(&lock);
+ mutex_unlock(&harddog_mutex);
+ return err;
+}
+
+extern void stop_watchdog(int in_fd, int out_fd);
+
+static int harddog_release(struct inode *inode, struct file *file)
+{
+ /*
+ * Shut off the timer.
+ */
+
+ spin_lock(&lock);
+
+ stop_watchdog(harddog_in_fd, harddog_out_fd);
+ harddog_in_fd = -1;
+ harddog_out_fd = -1;
+
+ timer_alive=0;
+ spin_unlock(&lock);
+
+ return 0;
+}
+
+extern int ping_watchdog(int fd);
+
+static ssize_t harddog_write(struct file *file, const char __user *data, size_t len,
+ loff_t *ppos)
+{
+ /*
+ * Refresh the timer.
+ */
+ if(len)
+ return ping_watchdog(harddog_out_fd);
+ return 0;
+}
+
+static int harddog_ioctl_unlocked(struct file *file,
+ unsigned int cmd, unsigned long arg)
+{
+ void __user *argp= (void __user *)arg;
+ static struct watchdog_info ident = {
+ WDIOC_SETTIMEOUT,
+ 0,
+ "UML Hardware Watchdog"
+ };
+ switch (cmd) {
+ default:
+ return -ENOTTY;
+ case WDIOC_GETSUPPORT:
+ if(copy_to_user(argp, &ident, sizeof(ident)))
+ return -EFAULT;
+ return 0;
+ case WDIOC_GETSTATUS:
+ case WDIOC_GETBOOTSTATUS:
+ return put_user(0,(int __user *)argp);
+ case WDIOC_KEEPALIVE:
+ return ping_watchdog(harddog_out_fd);
+ }
+}
+
+static long harddog_ioctl(struct file *file,
+ unsigned int cmd, unsigned long arg)
+{
+ long ret;
+
+ mutex_lock(&harddog_mutex);
+ ret = harddog_ioctl_unlocked(file, cmd, arg);
+ mutex_unlock(&harddog_mutex);
+
+ return ret;
+}
+
+static const struct file_operations harddog_fops = {
+ .owner = THIS_MODULE,
+ .write = harddog_write,
+ .unlocked_ioctl = harddog_ioctl,
+ .open = harddog_open,
+ .release = harddog_release,
+ .llseek = no_llseek,
+};
+
+static struct miscdevice harddog_miscdev = {
+ .minor = WATCHDOG_MINOR,
+ .name = "watchdog",
+ .fops = &harddog_fops,
+};
+module_misc_device(harddog_miscdev);