1 /*
2  *	watchdog_dev.c
3  *
4  *	(c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
5  *						All Rights Reserved.
6  *
7  *	(c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
8  *
9  *
10  *	This source code is part of the generic code that can be used
11  *	by all the watchdog timer drivers.
12  *
13  *	This part of the generic code takes care of the following
14  *	misc device: /dev/watchdog.
15  *
16  *	Based on source code of the following authors:
17  *	  Matt Domsch <Matt_Domsch@dell.com>,
18  *	  Rob Radez <rob@osinvestor.com>,
19  *	  Rusty Lynch <rusty@linux.co.intel.com>
20  *	  Satyam Sharma <satyam@infradead.org>
21  *	  Randy Dunlap <randy.dunlap@oracle.com>
22  *
23  *	This program is free software; you can redistribute it and/or
24  *	modify it under the terms of the GNU General Public License
25  *	as published by the Free Software Foundation; either version
26  *	2 of the License, or (at your option) any later version.
27  *
28  *	Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
29  *	admit liability nor provide warranty for any of this software.
30  *	This material is provided "AS-IS" and at no charge.
31  */
32 
33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
34 
35 #include <linux/cdev.h>		/* For character device */
36 #include <linux/errno.h>	/* For the -ENODEV/... values */
37 #include <linux/fs.h>		/* For file operations */
38 #include <linux/init.h>		/* For __init/__exit/... */
39 #include <linux/jiffies.h>	/* For timeout functions */
40 #include <linux/kernel.h>	/* For printk/panic/... */
41 #include <linux/kref.h>		/* For data references */
42 #include <linux/miscdevice.h>	/* For handling misc devices */
43 #include <linux/module.h>	/* For module stuff/... */
44 #include <linux/mutex.h>	/* For mutexes */
45 #include <linux/slab.h>		/* For memory functions */
46 #include <linux/types.h>	/* For standard types (like size_t) */
47 #include <linux/watchdog.h>	/* For watchdog specific items */
48 #include <linux/workqueue.h>	/* For workqueue */
49 #include <linux/uaccess.h>	/* For copy_to_user/put_user/... */
50 
51 #include "watchdog_core.h"
52 #include "watchdog_pretimeout.h"
53 
54 /*
55  * struct watchdog_core_data - watchdog core internal data
56  * @kref:	Reference count.
57  * @cdev:	The watchdog's Character device.
58  * @wdd:	Pointer to watchdog device.
59  * @lock:	Lock for watchdog core.
60  * @status:	Watchdog core internal status bits.
61  */
62 struct watchdog_core_data {
63 	struct kref kref;
64 	struct cdev cdev;
65 	struct watchdog_device *wdd;
66 	struct mutex lock;
67 	unsigned long last_keepalive;
68 	unsigned long last_hw_keepalive;
69 	struct delayed_work work;
70 	unsigned long status;		/* Internal status bits */
71 #define _WDOG_DEV_OPEN		0	/* Opened ? */
72 #define _WDOG_ALLOW_RELEASE	1	/* Did we receive the magic char ? */
73 #define _WDOG_KEEPALIVE		2	/* Did we receive a keepalive ? */
74 };
75 
76 /* the dev_t structure to store the dynamically allocated watchdog devices */
77 static dev_t watchdog_devt;
78 /* Reference to watchdog device behind /dev/watchdog */
79 static struct watchdog_core_data *old_wd_data;
80 
81 static struct workqueue_struct *watchdog_wq;
82 
83 static bool handle_boot_enabled =
84 	IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
85 
86 static inline bool watchdog_need_worker(struct watchdog_device *wdd)
87 {
88 	/* All variables in milli-seconds */
89 	unsigned int hm = wdd->max_hw_heartbeat_ms;
90 	unsigned int t = wdd->timeout * 1000;
91 
92 	/*
93 	 * A worker to generate heartbeat requests is needed if all of the
94 	 * following conditions are true.
95 	 * - Userspace activated the watchdog.
96 	 * - The driver provided a value for the maximum hardware timeout, and
97 	 *   thus is aware that the framework supports generating heartbeat
98 	 *   requests.
99 	 * - Userspace requests a longer timeout than the hardware can handle.
100 	 *
101 	 * Alternatively, if userspace has not opened the watchdog
102 	 * device, we take care of feeding the watchdog if it is
103 	 * running.
104 	 */
105 	return (hm && watchdog_active(wdd) && t > hm) ||
106 		(t && !watchdog_active(wdd) && watchdog_hw_running(wdd));
107 }
108 
109 static long watchdog_next_keepalive(struct watchdog_device *wdd)
110 {
111 	struct watchdog_core_data *wd_data = wdd->wd_data;
112 	unsigned int timeout_ms = wdd->timeout * 1000;
113 	unsigned long keepalive_interval;
114 	unsigned long last_heartbeat;
115 	unsigned long virt_timeout;
116 	unsigned int hw_heartbeat_ms;
117 
118 	virt_timeout = wd_data->last_keepalive + msecs_to_jiffies(timeout_ms);
119 	hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms);
120 	keepalive_interval = msecs_to_jiffies(hw_heartbeat_ms / 2);
121 
122 	if (!watchdog_active(wdd))
123 		return keepalive_interval;
124 
125 	/*
126 	 * To ensure that the watchdog times out wdd->timeout seconds
127 	 * after the most recent ping from userspace, the last
128 	 * worker ping has to come in hw_heartbeat_ms before this timeout.
129 	 */
130 	last_heartbeat = virt_timeout - msecs_to_jiffies(hw_heartbeat_ms);
131 	return min_t(long, last_heartbeat - jiffies, keepalive_interval);
132 }
133 
134 static inline void watchdog_update_worker(struct watchdog_device *wdd)
135 {
136 	struct watchdog_core_data *wd_data = wdd->wd_data;
137 
138 	if (watchdog_need_worker(wdd)) {
139 		long t = watchdog_next_keepalive(wdd);
140 
141 		if (t > 0)
142 			mod_delayed_work(watchdog_wq, &wd_data->work, t);
143 	} else {
144 		cancel_delayed_work(&wd_data->work);
145 	}
146 }
147 
148 static int __watchdog_ping(struct watchdog_device *wdd)
149 {
150 	struct watchdog_core_data *wd_data = wdd->wd_data;
151 	unsigned long earliest_keepalive = wd_data->last_hw_keepalive +
152 				msecs_to_jiffies(wdd->min_hw_heartbeat_ms);
153 	int err;
154 
155 	if (time_is_after_jiffies(earliest_keepalive)) {
156 		mod_delayed_work(watchdog_wq, &wd_data->work,
157 				 earliest_keepalive - jiffies);
158 		return 0;
159 	}
160 
161 	wd_data->last_hw_keepalive = jiffies;
162 
163 	if (wdd->ops->ping)
164 		err = wdd->ops->ping(wdd);  /* ping the watchdog */
165 	else
166 		err = wdd->ops->start(wdd); /* restart watchdog */
167 
168 	watchdog_update_worker(wdd);
169 
170 	return err;
171 }
172 
173 /*
174  *	watchdog_ping: ping the watchdog.
175  *	@wdd: the watchdog device to ping
176  *
177  *	The caller must hold wd_data->lock.
178  *
179  *	If the watchdog has no own ping operation then it needs to be
180  *	restarted via the start operation. This wrapper function does
181  *	exactly that.
182  *	We only ping when the watchdog device is running.
183  */
184 
185 static int watchdog_ping(struct watchdog_device *wdd)
186 {
187 	struct watchdog_core_data *wd_data = wdd->wd_data;
188 
189 	if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
190 		return 0;
191 
192 	set_bit(_WDOG_KEEPALIVE, &wd_data->status);
193 
194 	wd_data->last_keepalive = jiffies;
195 	return __watchdog_ping(wdd);
196 }
197 
198 static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data)
199 {
200 	struct watchdog_device *wdd = wd_data->wdd;
201 
202 	return wdd && (watchdog_active(wdd) || watchdog_hw_running(wdd));
203 }
204 
205 static void watchdog_ping_work(struct work_struct *work)
206 {
207 	struct watchdog_core_data *wd_data;
208 
209 	wd_data = container_of(to_delayed_work(work), struct watchdog_core_data,
210 			       work);
211 
212 	mutex_lock(&wd_data->lock);
213 	if (watchdog_worker_should_ping(wd_data))
214 		__watchdog_ping(wd_data->wdd);
215 	mutex_unlock(&wd_data->lock);
216 }
217 
218 /*
219  *	watchdog_start: wrapper to start the watchdog.
220  *	@wdd: the watchdog device to start
221  *
222  *	The caller must hold wd_data->lock.
223  *
224  *	Start the watchdog if it is not active and mark it active.
225  *	This function returns zero on success or a negative errno code for
226  *	failure.
227  */
228 
229 static int watchdog_start(struct watchdog_device *wdd)
230 {
231 	struct watchdog_core_data *wd_data = wdd->wd_data;
232 	unsigned long started_at;
233 	int err;
234 
235 	if (watchdog_active(wdd))
236 		return 0;
237 
238 	set_bit(_WDOG_KEEPALIVE, &wd_data->status);
239 
240 	started_at = jiffies;
241 	if (watchdog_hw_running(wdd) && wdd->ops->ping)
242 		err = wdd->ops->ping(wdd);
243 	else
244 		err = wdd->ops->start(wdd);
245 	if (err == 0) {
246 		set_bit(WDOG_ACTIVE, &wdd->status);
247 		wd_data->last_keepalive = started_at;
248 		watchdog_update_worker(wdd);
249 	}
250 
251 	return err;
252 }
253 
254 /*
255  *	watchdog_stop: wrapper to stop the watchdog.
256  *	@wdd: the watchdog device to stop
257  *
258  *	The caller must hold wd_data->lock.
259  *
260  *	Stop the watchdog if it is still active and unmark it active.
261  *	This function returns zero on success or a negative errno code for
262  *	failure.
263  *	If the 'nowayout' feature was set, the watchdog cannot be stopped.
264  */
265 
266 static int watchdog_stop(struct watchdog_device *wdd)
267 {
268 	int err = 0;
269 
270 	if (!watchdog_active(wdd))
271 		return 0;
272 
273 	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
274 		pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
275 			wdd->id);
276 		return -EBUSY;
277 	}
278 
279 	if (wdd->ops->stop) {
280 		clear_bit(WDOG_HW_RUNNING, &wdd->status);
281 		err = wdd->ops->stop(wdd);
282 	} else {
283 		set_bit(WDOG_HW_RUNNING, &wdd->status);
284 	}
285 
286 	if (err == 0) {
287 		clear_bit(WDOG_ACTIVE, &wdd->status);
288 		watchdog_update_worker(wdd);
289 	}
290 
291 	return err;
292 }
293 
294 /*
295  *	watchdog_get_status: wrapper to get the watchdog status
296  *	@wdd: the watchdog device to get the status from
297  *
298  *	The caller must hold wd_data->lock.
299  *
300  *	Get the watchdog's status flags.
301  */
302 
303 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
304 {
305 	struct watchdog_core_data *wd_data = wdd->wd_data;
306 	unsigned int status;
307 
308 	if (wdd->ops->status)
309 		status = wdd->ops->status(wdd);
310 	else
311 		status = wdd->bootstatus & (WDIOF_CARDRESET |
312 					    WDIOF_OVERHEAT |
313 					    WDIOF_FANFAULT |
314 					    WDIOF_EXTERN1 |
315 					    WDIOF_EXTERN2 |
316 					    WDIOF_POWERUNDER |
317 					    WDIOF_POWEROVER);
318 
319 	if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
320 		status |= WDIOF_MAGICCLOSE;
321 
322 	if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
323 		status |= WDIOF_KEEPALIVEPING;
324 
325 	return status;
326 }
327 
328 /*
329  *	watchdog_set_timeout: set the watchdog timer timeout
330  *	@wdd: the watchdog device to set the timeout for
331  *	@timeout: timeout to set in seconds
332  *
333  *	The caller must hold wd_data->lock.
334  */
335 
336 static int watchdog_set_timeout(struct watchdog_device *wdd,
337 							unsigned int timeout)
338 {
339 	int err = 0;
340 
341 	if (!(wdd->info->options & WDIOF_SETTIMEOUT))
342 		return -EOPNOTSUPP;
343 
344 	if (watchdog_timeout_invalid(wdd, timeout))
345 		return -EINVAL;
346 
347 	if (wdd->ops->set_timeout) {
348 		err = wdd->ops->set_timeout(wdd, timeout);
349 	} else {
350 		wdd->timeout = timeout;
351 		/* Disable pretimeout if it doesn't fit the new timeout */
352 		if (wdd->pretimeout >= wdd->timeout)
353 			wdd->pretimeout = 0;
354 	}
355 
356 	watchdog_update_worker(wdd);
357 
358 	return err;
359 }
360 
361 /*
362  *	watchdog_set_pretimeout: set the watchdog timer pretimeout
363  *	@wdd: the watchdog device to set the timeout for
364  *	@timeout: pretimeout to set in seconds
365  */
366 
367 static int watchdog_set_pretimeout(struct watchdog_device *wdd,
368 				   unsigned int timeout)
369 {
370 	int err = 0;
371 
372 	if (!(wdd->info->options & WDIOF_PRETIMEOUT))
373 		return -EOPNOTSUPP;
374 
375 	if (watchdog_pretimeout_invalid(wdd, timeout))
376 		return -EINVAL;
377 
378 	if (wdd->ops->set_pretimeout)
379 		err = wdd->ops->set_pretimeout(wdd, timeout);
380 	else
381 		wdd->pretimeout = timeout;
382 
383 	return err;
384 }
385 
386 /*
387  *	watchdog_get_timeleft: wrapper to get the time left before a reboot
388  *	@wdd: the watchdog device to get the remaining time from
389  *	@timeleft: the time that's left
390  *
391  *	The caller must hold wd_data->lock.
392  *
393  *	Get the time before a watchdog will reboot (if not pinged).
394  */
395 
396 static int watchdog_get_timeleft(struct watchdog_device *wdd,
397 							unsigned int *timeleft)
398 {
399 	*timeleft = 0;
400 
401 	if (!wdd->ops->get_timeleft)
402 		return -EOPNOTSUPP;
403 
404 	*timeleft = wdd->ops->get_timeleft(wdd);
405 
406 	return 0;
407 }
408 
409 #ifdef CONFIG_WATCHDOG_SYSFS
410 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
411 				char *buf)
412 {
413 	struct watchdog_device *wdd = dev_get_drvdata(dev);
414 
415 	return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
416 }
417 static DEVICE_ATTR_RO(nowayout);
418 
419 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
420 				char *buf)
421 {
422 	struct watchdog_device *wdd = dev_get_drvdata(dev);
423 	struct watchdog_core_data *wd_data = wdd->wd_data;
424 	unsigned int status;
425 
426 	mutex_lock(&wd_data->lock);
427 	status = watchdog_get_status(wdd);
428 	mutex_unlock(&wd_data->lock);
429 
430 	return sprintf(buf, "0x%x\n", status);
431 }
432 static DEVICE_ATTR_RO(status);
433 
434 static ssize_t bootstatus_show(struct device *dev,
435 				struct device_attribute *attr, char *buf)
436 {
437 	struct watchdog_device *wdd = dev_get_drvdata(dev);
438 
439 	return sprintf(buf, "%u\n", wdd->bootstatus);
440 }
441 static DEVICE_ATTR_RO(bootstatus);
442 
443 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
444 				char *buf)
445 {
446 	struct watchdog_device *wdd = dev_get_drvdata(dev);
447 	struct watchdog_core_data *wd_data = wdd->wd_data;
448 	ssize_t status;
449 	unsigned int val;
450 
451 	mutex_lock(&wd_data->lock);
452 	status = watchdog_get_timeleft(wdd, &val);
453 	mutex_unlock(&wd_data->lock);
454 	if (!status)
455 		status = sprintf(buf, "%u\n", val);
456 
457 	return status;
458 }
459 static DEVICE_ATTR_RO(timeleft);
460 
461 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
462 				char *buf)
463 {
464 	struct watchdog_device *wdd = dev_get_drvdata(dev);
465 
466 	return sprintf(buf, "%u\n", wdd->timeout);
467 }
468 static DEVICE_ATTR_RO(timeout);
469 
470 static ssize_t pretimeout_show(struct device *dev,
471 			       struct device_attribute *attr, char *buf)
472 {
473 	struct watchdog_device *wdd = dev_get_drvdata(dev);
474 
475 	return sprintf(buf, "%u\n", wdd->pretimeout);
476 }
477 static DEVICE_ATTR_RO(pretimeout);
478 
479 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
480 				char *buf)
481 {
482 	struct watchdog_device *wdd = dev_get_drvdata(dev);
483 
484 	return sprintf(buf, "%s\n", wdd->info->identity);
485 }
486 static DEVICE_ATTR_RO(identity);
487 
488 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
489 				char *buf)
490 {
491 	struct watchdog_device *wdd = dev_get_drvdata(dev);
492 
493 	if (watchdog_active(wdd))
494 		return sprintf(buf, "active\n");
495 
496 	return sprintf(buf, "inactive\n");
497 }
498 static DEVICE_ATTR_RO(state);
499 
500 static ssize_t pretimeout_available_governors_show(struct device *dev,
501 				   struct device_attribute *attr, char *buf)
502 {
503 	return watchdog_pretimeout_available_governors_get(buf);
504 }
505 static DEVICE_ATTR_RO(pretimeout_available_governors);
506 
507 static ssize_t pretimeout_governor_show(struct device *dev,
508 					struct device_attribute *attr,
509 					char *buf)
510 {
511 	struct watchdog_device *wdd = dev_get_drvdata(dev);
512 
513 	return watchdog_pretimeout_governor_get(wdd, buf);
514 }
515 
516 static ssize_t pretimeout_governor_store(struct device *dev,
517 					 struct device_attribute *attr,
518 					 const char *buf, size_t count)
519 {
520 	struct watchdog_device *wdd = dev_get_drvdata(dev);
521 	int ret = watchdog_pretimeout_governor_set(wdd, buf);
522 
523 	if (!ret)
524 		ret = count;
525 
526 	return ret;
527 }
528 static DEVICE_ATTR_RW(pretimeout_governor);
529 
530 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
531 				int n)
532 {
533 	struct device *dev = container_of(kobj, struct device, kobj);
534 	struct watchdog_device *wdd = dev_get_drvdata(dev);
535 	umode_t mode = attr->mode;
536 
537 	if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
538 		mode = 0;
539 	else if (attr == &dev_attr_pretimeout.attr &&
540 		 !(wdd->info->options & WDIOF_PRETIMEOUT))
541 		mode = 0;
542 	else if ((attr == &dev_attr_pretimeout_governor.attr ||
543 		  attr == &dev_attr_pretimeout_available_governors.attr) &&
544 		 (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
545 		  !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
546 		mode = 0;
547 
548 	return mode;
549 }
550 static struct attribute *wdt_attrs[] = {
551 	&dev_attr_state.attr,
552 	&dev_attr_identity.attr,
553 	&dev_attr_timeout.attr,
554 	&dev_attr_pretimeout.attr,
555 	&dev_attr_timeleft.attr,
556 	&dev_attr_bootstatus.attr,
557 	&dev_attr_status.attr,
558 	&dev_attr_nowayout.attr,
559 	&dev_attr_pretimeout_governor.attr,
560 	&dev_attr_pretimeout_available_governors.attr,
561 	NULL,
562 };
563 
564 static const struct attribute_group wdt_group = {
565 	.attrs = wdt_attrs,
566 	.is_visible = wdt_is_visible,
567 };
568 __ATTRIBUTE_GROUPS(wdt);
569 #else
570 #define wdt_groups	NULL
571 #endif
572 
573 /*
574  *	watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
575  *	@wdd: the watchdog device to do the ioctl on
576  *	@cmd: watchdog command
577  *	@arg: argument pointer
578  *
579  *	The caller must hold wd_data->lock.
580  */
581 
582 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
583 							unsigned long arg)
584 {
585 	if (!wdd->ops->ioctl)
586 		return -ENOIOCTLCMD;
587 
588 	return wdd->ops->ioctl(wdd, cmd, arg);
589 }
590 
591 /*
592  *	watchdog_write: writes to the watchdog.
593  *	@file: file from VFS
594  *	@data: user address of data
595  *	@len: length of data
596  *	@ppos: pointer to the file offset
597  *
598  *	A write to a watchdog device is defined as a keepalive ping.
599  *	Writing the magic 'V' sequence allows the next close to turn
600  *	off the watchdog (if 'nowayout' is not set).
601  */
602 
603 static ssize_t watchdog_write(struct file *file, const char __user *data,
604 						size_t len, loff_t *ppos)
605 {
606 	struct watchdog_core_data *wd_data = file->private_data;
607 	struct watchdog_device *wdd;
608 	int err;
609 	size_t i;
610 	char c;
611 
612 	if (len == 0)
613 		return 0;
614 
615 	/*
616 	 * Note: just in case someone wrote the magic character
617 	 * five months ago...
618 	 */
619 	clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
620 
621 	/* scan to see whether or not we got the magic character */
622 	for (i = 0; i != len; i++) {
623 		if (get_user(c, data + i))
624 			return -EFAULT;
625 		if (c == 'V')
626 			set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
627 	}
628 
629 	/* someone wrote to us, so we send the watchdog a keepalive ping */
630 
631 	err = -ENODEV;
632 	mutex_lock(&wd_data->lock);
633 	wdd = wd_data->wdd;
634 	if (wdd)
635 		err = watchdog_ping(wdd);
636 	mutex_unlock(&wd_data->lock);
637 
638 	if (err < 0)
639 		return err;
640 
641 	return len;
642 }
643 
644 /*
645  *	watchdog_ioctl: handle the different ioctl's for the watchdog device.
646  *	@file: file handle to the device
647  *	@cmd: watchdog command
648  *	@arg: argument pointer
649  *
650  *	The watchdog API defines a common set of functions for all watchdogs
651  *	according to their available features.
652  */
653 
654 static long watchdog_ioctl(struct file *file, unsigned int cmd,
655 							unsigned long arg)
656 {
657 	struct watchdog_core_data *wd_data = file->private_data;
658 	void __user *argp = (void __user *)arg;
659 	struct watchdog_device *wdd;
660 	int __user *p = argp;
661 	unsigned int val;
662 	int err;
663 
664 	mutex_lock(&wd_data->lock);
665 
666 	wdd = wd_data->wdd;
667 	if (!wdd) {
668 		err = -ENODEV;
669 		goto out_ioctl;
670 	}
671 
672 	err = watchdog_ioctl_op(wdd, cmd, arg);
673 	if (err != -ENOIOCTLCMD)
674 		goto out_ioctl;
675 
676 	switch (cmd) {
677 	case WDIOC_GETSUPPORT:
678 		err = copy_to_user(argp, wdd->info,
679 			sizeof(struct watchdog_info)) ? -EFAULT : 0;
680 		break;
681 	case WDIOC_GETSTATUS:
682 		val = watchdog_get_status(wdd);
683 		err = put_user(val, p);
684 		break;
685 	case WDIOC_GETBOOTSTATUS:
686 		err = put_user(wdd->bootstatus, p);
687 		break;
688 	case WDIOC_SETOPTIONS:
689 		if (get_user(val, p)) {
690 			err = -EFAULT;
691 			break;
692 		}
693 		if (val & WDIOS_DISABLECARD) {
694 			err = watchdog_stop(wdd);
695 			if (err < 0)
696 				break;
697 		}
698 		if (val & WDIOS_ENABLECARD)
699 			err = watchdog_start(wdd);
700 		break;
701 	case WDIOC_KEEPALIVE:
702 		if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
703 			err = -EOPNOTSUPP;
704 			break;
705 		}
706 		err = watchdog_ping(wdd);
707 		break;
708 	case WDIOC_SETTIMEOUT:
709 		if (get_user(val, p)) {
710 			err = -EFAULT;
711 			break;
712 		}
713 		err = watchdog_set_timeout(wdd, val);
714 		if (err < 0)
715 			break;
716 		/* If the watchdog is active then we send a keepalive ping
717 		 * to make sure that the watchdog keep's running (and if
718 		 * possible that it takes the new timeout) */
719 		err = watchdog_ping(wdd);
720 		if (err < 0)
721 			break;
722 		/* Fall */
723 	case WDIOC_GETTIMEOUT:
724 		/* timeout == 0 means that we don't know the timeout */
725 		if (wdd->timeout == 0) {
726 			err = -EOPNOTSUPP;
727 			break;
728 		}
729 		err = put_user(wdd->timeout, p);
730 		break;
731 	case WDIOC_GETTIMELEFT:
732 		err = watchdog_get_timeleft(wdd, &val);
733 		if (err < 0)
734 			break;
735 		err = put_user(val, p);
736 		break;
737 	case WDIOC_SETPRETIMEOUT:
738 		if (get_user(val, p)) {
739 			err = -EFAULT;
740 			break;
741 		}
742 		err = watchdog_set_pretimeout(wdd, val);
743 		break;
744 	case WDIOC_GETPRETIMEOUT:
745 		err = put_user(wdd->pretimeout, p);
746 		break;
747 	default:
748 		err = -ENOTTY;
749 		break;
750 	}
751 
752 out_ioctl:
753 	mutex_unlock(&wd_data->lock);
754 	return err;
755 }
756 
757 /*
758  *	watchdog_open: open the /dev/watchdog* devices.
759  *	@inode: inode of device
760  *	@file: file handle to device
761  *
762  *	When the /dev/watchdog* device gets opened, we start the watchdog.
763  *	Watch out: the /dev/watchdog device is single open, so we make sure
764  *	it can only be opened once.
765  */
766 
767 static int watchdog_open(struct inode *inode, struct file *file)
768 {
769 	struct watchdog_core_data *wd_data;
770 	struct watchdog_device *wdd;
771 	int err;
772 
773 	/* Get the corresponding watchdog device */
774 	if (imajor(inode) == MISC_MAJOR)
775 		wd_data = old_wd_data;
776 	else
777 		wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
778 				       cdev);
779 
780 	/* the watchdog is single open! */
781 	if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
782 		return -EBUSY;
783 
784 	wdd = wd_data->wdd;
785 
786 	/*
787 	 * If the /dev/watchdog device is open, we don't want the module
788 	 * to be unloaded.
789 	 */
790 	if (!watchdog_hw_running(wdd) && !try_module_get(wdd->ops->owner)) {
791 		err = -EBUSY;
792 		goto out_clear;
793 	}
794 
795 	err = watchdog_start(wdd);
796 	if (err < 0)
797 		goto out_mod;
798 
799 	file->private_data = wd_data;
800 
801 	if (!watchdog_hw_running(wdd))
802 		kref_get(&wd_data->kref);
803 
804 	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
805 	return nonseekable_open(inode, file);
806 
807 out_mod:
808 	module_put(wd_data->wdd->ops->owner);
809 out_clear:
810 	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
811 	return err;
812 }
813 
814 static void watchdog_core_data_release(struct kref *kref)
815 {
816 	struct watchdog_core_data *wd_data;
817 
818 	wd_data = container_of(kref, struct watchdog_core_data, kref);
819 
820 	kfree(wd_data);
821 }
822 
823 /*
824  *	watchdog_release: release the watchdog device.
825  *	@inode: inode of device
826  *	@file: file handle to device
827  *
828  *	This is the code for when /dev/watchdog gets closed. We will only
829  *	stop the watchdog when we have received the magic char (and nowayout
830  *	was not set), else the watchdog will keep running.
831  */
832 
833 static int watchdog_release(struct inode *inode, struct file *file)
834 {
835 	struct watchdog_core_data *wd_data = file->private_data;
836 	struct watchdog_device *wdd;
837 	int err = -EBUSY;
838 	bool running;
839 
840 	mutex_lock(&wd_data->lock);
841 
842 	wdd = wd_data->wdd;
843 	if (!wdd)
844 		goto done;
845 
846 	/*
847 	 * We only stop the watchdog if we received the magic character
848 	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
849 	 * watchdog_stop will fail.
850 	 */
851 	if (!test_bit(WDOG_ACTIVE, &wdd->status))
852 		err = 0;
853 	else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
854 		 !(wdd->info->options & WDIOF_MAGICCLOSE))
855 		err = watchdog_stop(wdd);
856 
857 	/* If the watchdog was not stopped, send a keepalive ping */
858 	if (err < 0) {
859 		pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
860 		watchdog_ping(wdd);
861 	}
862 
863 	watchdog_update_worker(wdd);
864 
865 	/* make sure that /dev/watchdog can be re-opened */
866 	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
867 
868 done:
869 	running = wdd && watchdog_hw_running(wdd);
870 	mutex_unlock(&wd_data->lock);
871 	/*
872 	 * Allow the owner module to be unloaded again unless the watchdog
873 	 * is still running. If the watchdog is still running, it can not
874 	 * be stopped, and its driver must not be unloaded.
875 	 */
876 	if (!running) {
877 		module_put(wd_data->cdev.owner);
878 		kref_put(&wd_data->kref, watchdog_core_data_release);
879 	}
880 	return 0;
881 }
882 
883 static const struct file_operations watchdog_fops = {
884 	.owner		= THIS_MODULE,
885 	.write		= watchdog_write,
886 	.unlocked_ioctl	= watchdog_ioctl,
887 	.open		= watchdog_open,
888 	.release	= watchdog_release,
889 };
890 
891 static struct miscdevice watchdog_miscdev = {
892 	.minor		= WATCHDOG_MINOR,
893 	.name		= "watchdog",
894 	.fops		= &watchdog_fops,
895 };
896 
897 /*
898  *	watchdog_cdev_register: register watchdog character device
899  *	@wdd: watchdog device
900  *	@devno: character device number
901  *
902  *	Register a watchdog character device including handling the legacy
903  *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
904  *	thus we set it up like that.
905  */
906 
907 static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
908 {
909 	struct watchdog_core_data *wd_data;
910 	int err;
911 
912 	wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
913 	if (!wd_data)
914 		return -ENOMEM;
915 	kref_init(&wd_data->kref);
916 	mutex_init(&wd_data->lock);
917 
918 	wd_data->wdd = wdd;
919 	wdd->wd_data = wd_data;
920 
921 	if (!watchdog_wq)
922 		return -ENODEV;
923 
924 	INIT_DELAYED_WORK(&wd_data->work, watchdog_ping_work);
925 
926 	if (wdd->id == 0) {
927 		old_wd_data = wd_data;
928 		watchdog_miscdev.parent = wdd->parent;
929 		err = misc_register(&watchdog_miscdev);
930 		if (err != 0) {
931 			pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
932 				wdd->info->identity, WATCHDOG_MINOR, err);
933 			if (err == -EBUSY)
934 				pr_err("%s: a legacy watchdog module is probably present.\n",
935 					wdd->info->identity);
936 			old_wd_data = NULL;
937 			kfree(wd_data);
938 			return err;
939 		}
940 	}
941 
942 	/* Fill in the data structures */
943 	cdev_init(&wd_data->cdev, &watchdog_fops);
944 	wd_data->cdev.owner = wdd->ops->owner;
945 
946 	/* Add the device */
947 	err = cdev_add(&wd_data->cdev, devno, 1);
948 	if (err) {
949 		pr_err("watchdog%d unable to add device %d:%d\n",
950 			wdd->id,  MAJOR(watchdog_devt), wdd->id);
951 		if (wdd->id == 0) {
952 			misc_deregister(&watchdog_miscdev);
953 			old_wd_data = NULL;
954 			kref_put(&wd_data->kref, watchdog_core_data_release);
955 		}
956 		return err;
957 	}
958 
959 	/* Record time of most recent heartbeat as 'just before now'. */
960 	wd_data->last_hw_keepalive = jiffies - 1;
961 
962 	/*
963 	 * If the watchdog is running, prevent its driver from being unloaded,
964 	 * and schedule an immediate ping.
965 	 */
966 	if (watchdog_hw_running(wdd)) {
967 		if (handle_boot_enabled) {
968 			__module_get(wdd->ops->owner);
969 			kref_get(&wd_data->kref);
970 			queue_delayed_work(watchdog_wq, &wd_data->work, 0);
971 		} else {
972 			pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
973 					wdd->id);
974 		}
975 	}
976 
977 	return 0;
978 }
979 
980 /*
981  *	watchdog_cdev_unregister: unregister watchdog character device
982  *	@watchdog: watchdog device
983  *
984  *	Unregister watchdog character device and if needed the legacy
985  *	/dev/watchdog device.
986  */
987 
988 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
989 {
990 	struct watchdog_core_data *wd_data = wdd->wd_data;
991 
992 	cdev_del(&wd_data->cdev);
993 	if (wdd->id == 0) {
994 		misc_deregister(&watchdog_miscdev);
995 		old_wd_data = NULL;
996 	}
997 
998 	mutex_lock(&wd_data->lock);
999 	wd_data->wdd = NULL;
1000 	wdd->wd_data = NULL;
1001 	mutex_unlock(&wd_data->lock);
1002 
1003 	if (watchdog_active(wdd) &&
1004 	    test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1005 		watchdog_stop(wdd);
1006 	}
1007 
1008 	cancel_delayed_work_sync(&wd_data->work);
1009 
1010 	kref_put(&wd_data->kref, watchdog_core_data_release);
1011 }
1012 
1013 static struct class watchdog_class = {
1014 	.name =		"watchdog",
1015 	.owner =	THIS_MODULE,
1016 	.dev_groups =	wdt_groups,
1017 };
1018 
1019 /*
1020  *	watchdog_dev_register: register a watchdog device
1021  *	@wdd: watchdog device
1022  *
1023  *	Register a watchdog device including handling the legacy
1024  *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
1025  *	thus we set it up like that.
1026  */
1027 
1028 int watchdog_dev_register(struct watchdog_device *wdd)
1029 {
1030 	struct device *dev;
1031 	dev_t devno;
1032 	int ret;
1033 
1034 	devno = MKDEV(MAJOR(watchdog_devt), wdd->id);
1035 
1036 	ret = watchdog_cdev_register(wdd, devno);
1037 	if (ret)
1038 		return ret;
1039 
1040 	dev = device_create_with_groups(&watchdog_class, wdd->parent,
1041 					devno, wdd, wdd->groups,
1042 					"watchdog%d", wdd->id);
1043 	if (IS_ERR(dev)) {
1044 		watchdog_cdev_unregister(wdd);
1045 		return PTR_ERR(dev);
1046 	}
1047 
1048 	ret = watchdog_register_pretimeout(wdd);
1049 	if (ret) {
1050 		device_destroy(&watchdog_class, devno);
1051 		watchdog_cdev_unregister(wdd);
1052 	}
1053 
1054 	return ret;
1055 }
1056 
1057 /*
1058  *	watchdog_dev_unregister: unregister a watchdog device
1059  *	@watchdog: watchdog device
1060  *
1061  *	Unregister watchdog device and if needed the legacy
1062  *	/dev/watchdog device.
1063  */
1064 
1065 void watchdog_dev_unregister(struct watchdog_device *wdd)
1066 {
1067 	watchdog_unregister_pretimeout(wdd);
1068 	device_destroy(&watchdog_class, wdd->wd_data->cdev.dev);
1069 	watchdog_cdev_unregister(wdd);
1070 }
1071 
1072 /*
1073  *	watchdog_dev_init: init dev part of watchdog core
1074  *
1075  *	Allocate a range of chardev nodes to use for watchdog devices
1076  */
1077 
1078 int __init watchdog_dev_init(void)
1079 {
1080 	int err;
1081 
1082 	watchdog_wq = alloc_workqueue("watchdogd",
1083 				      WQ_HIGHPRI | WQ_MEM_RECLAIM, 0);
1084 	if (!watchdog_wq) {
1085 		pr_err("Failed to create watchdog workqueue\n");
1086 		return -ENOMEM;
1087 	}
1088 
1089 	err = class_register(&watchdog_class);
1090 	if (err < 0) {
1091 		pr_err("couldn't register class\n");
1092 		goto err_register;
1093 	}
1094 
1095 	err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1096 	if (err < 0) {
1097 		pr_err("watchdog: unable to allocate char dev region\n");
1098 		goto err_alloc;
1099 	}
1100 
1101 	return 0;
1102 
1103 err_alloc:
1104 	class_unregister(&watchdog_class);
1105 err_register:
1106 	destroy_workqueue(watchdog_wq);
1107 	return err;
1108 }
1109 
1110 /*
1111  *	watchdog_dev_exit: exit dev part of watchdog core
1112  *
1113  *	Release the range of chardev nodes used for watchdog devices
1114  */
1115 
1116 void __exit watchdog_dev_exit(void)
1117 {
1118 	unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1119 	class_unregister(&watchdog_class);
1120 	destroy_workqueue(watchdog_wq);
1121 }
1122 
1123 module_param(handle_boot_enabled, bool, 0444);
1124 MODULE_PARM_DESC(handle_boot_enabled,
1125 	"Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1126 	__MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1127