watchdog: Xen watchdog driver

While the hypervisor change adding SCHEDOP_watchdog support included a
daemon to make use of the new functionality, having a kernel driver
for /dev/watchdog so that user space code doesn't need to distinguish
non-Xen and Xen seems to be preferable.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

1 files changed, 359 insertions, 0 deletions

diff --git a/drivers/watchdog/xen_wdt.c b/drivers/watchdog/xen_wdt.c
new file mode 100644
index 000000000000..49bd9d395562
--- /dev/null
+++ b/drivers/watchdog/xen_wdt.c
@@ -0,0 +1,359 @@
+/*
+ *      Xen Watchdog Driver
+ *
+ *      (c) Copyright 2010 Novell, Inc.
+ *
+ *      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.
+ */
+
+#define DRV_NAME        "wdt"
+#define DRV_VERSION     "0.01"
+#define PFX             DRV_NAME ": "
+
+#include <linux/bug.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/hrtimer.h>
+#include <linux/kernel.h>
+#include <linux/ktime.h>
+#include <linux/init.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include <linux/watchdog.h>
+#include <xen/xen.h>
+#include <asm/xen/hypercall.h>
+#include <xen/interface/sched.h>
+
+static struct platform_device *platform_device;
+static DEFINE_SPINLOCK(wdt_lock);
+static struct sched_watchdog wdt;
+static __kernel_time_t wdt_expires;
+static bool is_active, expect_release;
+
+#define WATCHDOG_TIMEOUT 60 /* in seconds */
+static unsigned int timeout = WATCHDOG_TIMEOUT;
+module_param(timeout, uint, S_IRUGO);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
+        "(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, S_IRUGO);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
+        "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+static inline __kernel_time_t set_timeout(void)
+{
+        wdt.timeout = timeout;
+        return ktime_to_timespec(ktime_get()).tv_sec + timeout;
+}
+
+static int xen_wdt_start(void)
+{
+        __kernel_time_t expires;
+        int err;
+
+        spin_lock(&wdt_lock);
+
+        expires = set_timeout();
+        if (!wdt.id)
+                err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
+        else
+                err = -EBUSY;
+        if (err > 0) {
+                wdt.id = err;
+                wdt_expires = expires;
+                err = 0;
+        } else
+                BUG_ON(!err);
+
+        spin_unlock(&wdt_lock);
+
+        return err;
+}
+
+static int xen_wdt_stop(void)
+{
+        int err = 0;
+
+        spin_lock(&wdt_lock);
+
+        wdt.timeout = 0;
+        if (wdt.id)
+                err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
+        if (!err)
+                wdt.id = 0;
+
+        spin_unlock(&wdt_lock);
+
+        return err;
+}
+
+static int xen_wdt_kick(void)
+{
+        __kernel_time_t expires;
+        int err;
+
+        spin_lock(&wdt_lock);
+
+        expires = set_timeout();
+        if (wdt.id)
+                err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
+        else
+                err = -ENXIO;
+        if (!err)
+                wdt_expires = expires;
+
+        spin_unlock(&wdt_lock);
+
+        return err;
+}
+
+static int xen_wdt_open(struct inode *inode, struct file *file)
+{
+        int err;
+
+        /* /dev/watchdog can only be opened once */
+        if (xchg(&is_active, true))
+                return -EBUSY;
+
+        err = xen_wdt_start();
+        if (err == -EBUSY)
+                err = xen_wdt_kick();
+        return err ?: nonseekable_open(inode, file);
+}
+
+static int xen_wdt_release(struct inode *inode, struct file *file)
+{
+        if (expect_release)
+                xen_wdt_stop();
+        else {
+                printk(KERN_CRIT PFX
+                       "unexpected close, not stopping watchdog!\n");
+                xen_wdt_kick();
+        }
+        is_active = false;
+        expect_release = false;
+        return 0;
+}
+
+static ssize_t xen_wdt_write(struct file *file, const char __user *data,
+                             size_t len, loff_t *ppos)
+{
+        /* See if we got the magic character 'V' and reload the timer */
+        if (len) {
+                if (!nowayout) {
+                        size_t i;
+
+                        /* in case it was set long ago */
+                        expect_release = false;
+
+                        /* scan to see whether or not we got the magic
+                           character */
+                        for (i = 0; i != len; i++) {
+                                char c;
+                                if (get_user(c, data + i))
+                                        return -EFAULT;
+                                if (c == 'V')
+                                        expect_release = true;
+                        }
+                }
+
+                /* someone wrote to us, we should reload the timer */
+                xen_wdt_kick();
+        }
+        return len;
+}
+
+static long xen_wdt_ioctl(struct file *file, unsigned int cmd,
+                          unsigned long arg)
+{
+        int new_options, retval = -EINVAL;
+        int new_timeout;
+        int __user *argp = (void __user *)arg;
+        static const struct watchdog_info ident = {
+                .options =              WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
+                .firmware_version =     0,
+                .identity =             DRV_NAME,
+        };
+
+        switch (cmd) {
+        case WDIOC_GETSUPPORT:
+                return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
+
+        case WDIOC_GETSTATUS:
+        case WDIOC_GETBOOTSTATUS:
+                return put_user(0, argp);
+
+        case WDIOC_SETOPTIONS:
+                if (get_user(new_options, argp))
+                        return -EFAULT;
+
+                if (new_options & WDIOS_DISABLECARD)
+                        retval = xen_wdt_stop();
+                if (new_options & WDIOS_ENABLECARD) {
+                        retval = xen_wdt_start();
+                        if (retval == -EBUSY)
+                                retval = xen_wdt_kick();
+                }
+                return retval;
+
+        case WDIOC_KEEPALIVE:
+                xen_wdt_kick();
+                return 0;
+
+        case WDIOC_SETTIMEOUT:
+                if (get_user(new_timeout, argp))
+                        return -EFAULT;
+                if (!new_timeout)
+                        return -EINVAL;
+                timeout = new_timeout;
+                xen_wdt_kick();
+                /* fall through */
+        case WDIOC_GETTIMEOUT:
+                return put_user(timeout, argp);
+
+        case WDIOC_GETTIMELEFT:
+                retval = wdt_expires - ktime_to_timespec(ktime_get()).tv_sec;
+                return put_user(retval, argp);
+        }
+
+        return -ENOTTY;
+}
+
+static const struct file_operations xen_wdt_fops = {
+        .owner =                THIS_MODULE,
+        .llseek =               no_llseek,
+        .write =                xen_wdt_write,
+        .unlocked_ioctl =       xen_wdt_ioctl,
+        .open =                 xen_wdt_open,
+        .release =              xen_wdt_release,
+};
+
+static struct miscdevice xen_wdt_miscdev = {
+        .minor =        WATCHDOG_MINOR,
+        .name =         "watchdog",
+        .fops =         &xen_wdt_fops,
+};
+
+static int __devinit xen_wdt_probe(struct platform_device *dev)
+{
+        struct sched_watchdog wd = { .id = ~0 };
+        int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);
+
+        switch (ret) {
+        case -EINVAL:
+                if (!timeout) {
+                        timeout = WATCHDOG_TIMEOUT;
+                        printk(KERN_INFO PFX
+                               "timeout value invalid, using %d\n", timeout);
+                }
+
+                ret = misc_register(&xen_wdt_miscdev);
+                if (ret) {
+                        printk(KERN_ERR PFX
+                               "cannot register miscdev on minor=%d (%d)\n",
+                               WATCHDOG_MINOR, ret);
+                        break;
+                }
+
+                printk(KERN_INFO PFX
+                       "initialized (timeout=%ds, nowayout=%d)\n",
+                       timeout, nowayout);
+                break;
+
+        case -ENOSYS:
+                printk(KERN_INFO PFX "not supported\n");
+                ret = -ENODEV;
+                break;
+
+        default:
+                printk(KERN_INFO PFX "bogus return value %d\n", ret);
+                break;
+        }
+
+        return ret;
+}
+
+static int __devexit xen_wdt_remove(struct platform_device *dev)
+{
+        /* Stop the timer before we leave */
+        if (!nowayout)
+                xen_wdt_stop();
+
+        misc_deregister(&xen_wdt_miscdev);
+
+        return 0;
+}
+
+static void xen_wdt_shutdown(struct platform_device *dev)
+{
+        xen_wdt_stop();
+}
+
+static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
+{
+        return xen_wdt_stop();
+}
+
+static int xen_wdt_resume(struct platform_device *dev)
+{
+        return xen_wdt_start();
+}
+
+static struct platform_driver xen_wdt_driver = {
+        .probe          = xen_wdt_probe,
+        .remove         = __devexit_p(xen_wdt_remove),
+        .shutdown       = xen_wdt_shutdown,
+        .suspend        = xen_wdt_suspend,
+        .resume         = xen_wdt_resume,
+        .driver         = {
+                .owner  = THIS_MODULE,
+                .name   = DRV_NAME,
+        },
+};
+
+static int __init xen_wdt_init_module(void)
+{
+        int err;
+
+        if (!xen_domain())
+                return -ENODEV;
+
+        printk(KERN_INFO PFX "Xen WatchDog Timer Driver v%s\n", DRV_VERSION);
+
+        err = platform_driver_register(&xen_wdt_driver);
+        if (err)
+                return err;
+
+        platform_device = platform_device_register_simple(DRV_NAME,
+                                                                  -1, NULL, 0);
+        if (IS_ERR(platform_device)) {
+                err = PTR_ERR(platform_device);
+                platform_driver_unregister(&xen_wdt_driver);
+        }
+
+        return err;
+}
+
+static void __exit xen_wdt_cleanup_module(void)
+{
+        platform_device_unregister(platform_device);
+        platform_driver_unregister(&xen_wdt_driver);
+        printk(KERN_INFO PFX "module unloaded\n");
+}
+
+module_init(xen_wdt_init_module);
+module_exit(xen_wdt_cleanup_module);
+
+MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
+MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
+MODULE_VERSION(DRV_VERSION);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);