1/*
2 *	Xen Watchdog Driver
3 *
4 *	(c) Copyright 2010 Novell, Inc.
5 *
6 *	This program is free software; you can redistribute it and/or
7 *	modify it under the terms of the GNU General Public License
8 *	as published by the Free Software Foundation; either version
9 *	2 of the License, or (at your option) any later version.
10 */
11
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
14#define DRV_NAME	"wdt"
15#define DRV_VERSION	"0.01"
16
17#include <linux/bug.h>
18#include <linux/errno.h>
19#include <linux/fs.h>
20#include <linux/hrtimer.h>
21#include <linux/kernel.h>
22#include <linux/ktime.h>
23#include <linux/init.h>
24#include <linux/miscdevice.h>
25#include <linux/module.h>
26#include <linux/moduleparam.h>
27#include <linux/platform_device.h>
28#include <linux/spinlock.h>
29#include <linux/uaccess.h>
30#include <linux/watchdog.h>
31#include <xen/xen.h>
32#include <asm/xen/hypercall.h>
33#include <xen/interface/sched.h>
34
35static struct platform_device *platform_device;
36static DEFINE_SPINLOCK(wdt_lock);
37static struct sched_watchdog wdt;
38static __kernel_time_t wdt_expires;
39static bool is_active, expect_release;
40
41#define WATCHDOG_TIMEOUT 60 /* in seconds */
42static unsigned int timeout = WATCHDOG_TIMEOUT;
43module_param(timeout, uint, S_IRUGO);
44MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
45	"(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
46
47static bool nowayout = WATCHDOG_NOWAYOUT;
48module_param(nowayout, bool, S_IRUGO);
49MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
50	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
51
52static inline __kernel_time_t set_timeout(void)
53{
54	wdt.timeout = timeout;
55	return ktime_to_timespec(ktime_get()).tv_sec + timeout;
56}
57
58static int xen_wdt_start(void)
59{
60	__kernel_time_t expires;
61	int err;
62
63	spin_lock(&wdt_lock);
64
65	expires = set_timeout();
66	if (!wdt.id)
67		err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
68	else
69		err = -EBUSY;
70	if (err > 0) {
71		wdt.id = err;
72		wdt_expires = expires;
73		err = 0;
74	} else
75		BUG_ON(!err);
76
77	spin_unlock(&wdt_lock);
78
79	return err;
80}
81
82static int xen_wdt_stop(void)
83{
84	int err = 0;
85
86	spin_lock(&wdt_lock);
87
88	wdt.timeout = 0;
89	if (wdt.id)
90		err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
91	if (!err)
92		wdt.id = 0;
93
94	spin_unlock(&wdt_lock);
95
96	return err;
97}
98
99static int xen_wdt_kick(void)
100{
101	__kernel_time_t expires;
102	int err;
103
104	spin_lock(&wdt_lock);
105
106	expires = set_timeout();
107	if (wdt.id)
108		err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
109	else
110		err = -ENXIO;
111	if (!err)
112		wdt_expires = expires;
113
114	spin_unlock(&wdt_lock);
115
116	return err;
117}
118
119static int xen_wdt_open(struct inode *inode, struct file *file)
120{
121	int err;
122
123	/* /dev/watchdog can only be opened once */
124	if (xchg(&is_active, true))
125		return -EBUSY;
126
127	err = xen_wdt_start();
128	if (err == -EBUSY)
129		err = xen_wdt_kick();
130	return err ?: nonseekable_open(inode, file);
131}
132
133static int xen_wdt_release(struct inode *inode, struct file *file)
134{
135	int err = 0;
136
137	if (expect_release)
138		err = xen_wdt_stop();
139	else {
140		pr_crit("unexpected close, not stopping watchdog!\n");
141		xen_wdt_kick();
142	}
143	is_active = err;
144	expect_release = false;
145	return err;
146}
147
148static ssize_t xen_wdt_write(struct file *file, const char __user *data,
149			     size_t len, loff_t *ppos)
150{
151	/* See if we got the magic character 'V' and reload the timer */
152	if (len) {
153		if (!nowayout) {
154			size_t i;
155
156			/* in case it was set long ago */
157			expect_release = false;
158
159			/* scan to see whether or not we got the magic
160			   character */
161			for (i = 0; i != len; i++) {
162				char c;
163				if (get_user(c, data + i))
164					return -EFAULT;
165				if (c == 'V')
166					expect_release = true;
167			}
168		}
169
170		/* someone wrote to us, we should reload the timer */
171		xen_wdt_kick();
172	}
173	return len;
174}
175
176static long xen_wdt_ioctl(struct file *file, unsigned int cmd,
177			  unsigned long arg)
178{
179	int new_options, retval = -EINVAL;
180	int new_timeout;
181	int __user *argp = (void __user *)arg;
182	static const struct watchdog_info ident = {
183		.options =		WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
184		.firmware_version =	0,
185		.identity =		DRV_NAME,
186	};
187
188	switch (cmd) {
189	case WDIOC_GETSUPPORT:
190		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
191
192	case WDIOC_GETSTATUS:
193	case WDIOC_GETBOOTSTATUS:
194		return put_user(0, argp);
195
196	case WDIOC_SETOPTIONS:
197		if (get_user(new_options, argp))
198			return -EFAULT;
199
200		if (new_options & WDIOS_DISABLECARD)
201			retval = xen_wdt_stop();
202		if (new_options & WDIOS_ENABLECARD) {
203			retval = xen_wdt_start();
204			if (retval == -EBUSY)
205				retval = xen_wdt_kick();
206		}
207		return retval;
208
209	case WDIOC_KEEPALIVE:
210		xen_wdt_kick();
211		return 0;
212
213	case WDIOC_SETTIMEOUT:
214		if (get_user(new_timeout, argp))
215			return -EFAULT;
216		if (!new_timeout)
217			return -EINVAL;
218		timeout = new_timeout;
219		xen_wdt_kick();
220		/* fall through */
221	case WDIOC_GETTIMEOUT:
222		return put_user(timeout, argp);
223
224	case WDIOC_GETTIMELEFT:
225		retval = wdt_expires - ktime_to_timespec(ktime_get()).tv_sec;
226		return put_user(retval, argp);
227	}
228
229	return -ENOTTY;
230}
231
232static const struct file_operations xen_wdt_fops = {
233	.owner =		THIS_MODULE,
234	.llseek =		no_llseek,
235	.write =		xen_wdt_write,
236	.unlocked_ioctl =	xen_wdt_ioctl,
237	.open =			xen_wdt_open,
238	.release =		xen_wdt_release,
239};
240
241static struct miscdevice xen_wdt_miscdev = {
242	.minor =	WATCHDOG_MINOR,
243	.name =		"watchdog",
244	.fops =		&xen_wdt_fops,
245};
246
247static int xen_wdt_probe(struct platform_device *dev)
248{
249	struct sched_watchdog wd = { .id = ~0 };
250	int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);
251
252	switch (ret) {
253	case -EINVAL:
254		if (!timeout) {
255			timeout = WATCHDOG_TIMEOUT;
256			pr_info("timeout value invalid, using %d\n", timeout);
257		}
258
259		ret = misc_register(&xen_wdt_miscdev);
260		if (ret) {
261			pr_err("cannot register miscdev on minor=%d (%d)\n",
262			       WATCHDOG_MINOR, ret);
263			break;
264		}
265
266		pr_info("initialized (timeout=%ds, nowayout=%d)\n",
267			timeout, nowayout);
268		break;
269
270	case -ENOSYS:
271		pr_info("not supported\n");
272		ret = -ENODEV;
273		break;
274
275	default:
276		pr_info("bogus return value %d\n", ret);
277		break;
278	}
279
280	return ret;
281}
282
283static int xen_wdt_remove(struct platform_device *dev)
284{
285	/* Stop the timer before we leave */
286	if (!nowayout)
287		xen_wdt_stop();
288
289	misc_deregister(&xen_wdt_miscdev);
290
291	return 0;
292}
293
294static void xen_wdt_shutdown(struct platform_device *dev)
295{
296	xen_wdt_stop();
297}
298
299static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
300{
301	typeof(wdt.id) id = wdt.id;
302	int rc = xen_wdt_stop();
303
304	wdt.id = id;
305	return rc;
306}
307
308static int xen_wdt_resume(struct platform_device *dev)
309{
310	if (!wdt.id)
311		return 0;
312	wdt.id = 0;
313	return xen_wdt_start();
314}
315
316static struct platform_driver xen_wdt_driver = {
317	.probe          = xen_wdt_probe,
318	.remove         = xen_wdt_remove,
319	.shutdown       = xen_wdt_shutdown,
320	.suspend        = xen_wdt_suspend,
321	.resume         = xen_wdt_resume,
322	.driver         = {
323		.name   = DRV_NAME,
324	},
325};
326
327static int __init xen_wdt_init_module(void)
328{
329	int err;
330
331	if (!xen_domain())
332		return -ENODEV;
333
334	pr_info("Xen WatchDog Timer Driver v%s\n", DRV_VERSION);
335
336	err = platform_driver_register(&xen_wdt_driver);
337	if (err)
338		return err;
339
340	platform_device = platform_device_register_simple(DRV_NAME,
341								  -1, NULL, 0);
342	if (IS_ERR(platform_device)) {
343		err = PTR_ERR(platform_device);
344		platform_driver_unregister(&xen_wdt_driver);
345	}
346
347	return err;
348}
349
350static void __exit xen_wdt_cleanup_module(void)
351{
352	platform_device_unregister(platform_device);
353	platform_driver_unregister(&xen_wdt_driver);
354	pr_info("module unloaded\n");
355}
356
357module_init(xen_wdt_init_module);
358module_exit(xen_wdt_cleanup_module);
359
360MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
361MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
362MODULE_VERSION(DRV_VERSION);
363MODULE_LICENSE("GPL");
364