1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  *	watchdog_dev.c
4  *
5  *	(c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
6  *						All Rights Reserved.
7  *
8  *	(c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
9  *
10  *
11  *	This source code is part of the generic code that can be used
12  *	by all the watchdog timer drivers.
13  *
14  *	This part of the generic code takes care of the following
15  *	misc device: /dev/watchdog.
16  *
17  *	Based on source code of the following authors:
18  *	  Matt Domsch <Matt_Domsch@dell.com>,
19  *	  Rob Radez <rob@osinvestor.com>,
20  *	  Rusty Lynch <rusty@linux.co.intel.com>
21  *	  Satyam Sharma <satyam@infradead.org>
22  *	  Randy Dunlap <randy.dunlap@oracle.com>
23  *
24  *	Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
25  *	admit liability nor provide warranty for any of this software.
26  *	This material is provided "AS-IS" and at no charge.
27  */
28 
29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
30 
31 #include <linux/cdev.h>		/* For character device */
32 #include <linux/errno.h>	/* For the -ENODEV/... values */
33 #include <linux/fs.h>		/* For file operations */
34 #include <linux/init.h>		/* For __init/__exit/... */
35 #include <linux/hrtimer.h>	/* For hrtimers */
36 #include <linux/kernel.h>	/* For printk/panic/... */
37 #include <linux/kthread.h>	/* For kthread_work */
38 #include <linux/miscdevice.h>	/* For handling misc devices */
39 #include <linux/module.h>	/* For module stuff/... */
40 #include <linux/mutex.h>	/* For mutexes */
41 #include <linux/slab.h>		/* For memory functions */
42 #include <linux/types.h>	/* For standard types (like size_t) */
43 #include <linux/watchdog.h>	/* For watchdog specific items */
44 #include <linux/uaccess.h>	/* For copy_to_user/put_user/... */
45 
46 #include <uapi/linux/sched/types.h>	/* For struct sched_param */
47 
48 #include "watchdog_core.h"
49 #include "watchdog_pretimeout.h"
50 
51 /*
52  * struct watchdog_core_data - watchdog core internal data
53  * @dev:	The watchdog's internal device
54  * @cdev:	The watchdog's Character device.
55  * @wdd:	Pointer to watchdog device.
56  * @lock:	Lock for watchdog core.
57  * @status:	Watchdog core internal status bits.
58  */
59 struct watchdog_core_data {
60 	struct device dev;
61 	struct cdev cdev;
62 	struct watchdog_device *wdd;
63 	struct mutex lock;
64 	ktime_t last_keepalive;
65 	ktime_t last_hw_keepalive;
66 	ktime_t open_deadline;
67 	struct hrtimer timer;
68 	struct kthread_work work;
69 	unsigned long status;		/* Internal status bits */
70 #define _WDOG_DEV_OPEN		0	/* Opened ? */
71 #define _WDOG_ALLOW_RELEASE	1	/* Did we receive the magic char ? */
72 #define _WDOG_KEEPALIVE		2	/* Did we receive a keepalive ? */
73 };
74 
75 /* the dev_t structure to store the dynamically allocated watchdog devices */
76 static dev_t watchdog_devt;
77 /* Reference to watchdog device behind /dev/watchdog */
78 static struct watchdog_core_data *old_wd_data;
79 
80 static struct kthread_worker *watchdog_kworker;
81 
82 static bool handle_boot_enabled =
83 	IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
84 
85 static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
86 
87 static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
88 {
89 	return ktime_after(ktime_get(), data->open_deadline);
90 }
91 
92 static void watchdog_set_open_deadline(struct watchdog_core_data *data)
93 {
94 	data->open_deadline = open_timeout ?
95 		ktime_get() + ktime_set(open_timeout, 0) : KTIME_MAX;
96 }
97 
98 static inline bool watchdog_need_worker(struct watchdog_device *wdd)
99 {
100 	/* All variables in milli-seconds */
101 	unsigned int hm = wdd->max_hw_heartbeat_ms;
102 	unsigned int t = wdd->timeout * 1000;
103 
104 	/*
105 	 * A worker to generate heartbeat requests is needed if all of the
106 	 * following conditions are true.
107 	 * - Userspace activated the watchdog.
108 	 * - The driver provided a value for the maximum hardware timeout, and
109 	 *   thus is aware that the framework supports generating heartbeat
110 	 *   requests.
111 	 * - Userspace requests a longer timeout than the hardware can handle.
112 	 *
113 	 * Alternatively, if userspace has not opened the watchdog
114 	 * device, we take care of feeding the watchdog if it is
115 	 * running.
116 	 */
117 	return (hm && watchdog_active(wdd) && t > hm) ||
118 		(t && !watchdog_active(wdd) && watchdog_hw_running(wdd));
119 }
120 
121 static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
122 {
123 	struct watchdog_core_data *wd_data = wdd->wd_data;
124 	unsigned int timeout_ms = wdd->timeout * 1000;
125 	ktime_t keepalive_interval;
126 	ktime_t last_heartbeat, latest_heartbeat;
127 	ktime_t virt_timeout;
128 	unsigned int hw_heartbeat_ms;
129 
130 	if (watchdog_active(wdd))
131 		virt_timeout = ktime_add(wd_data->last_keepalive,
132 					 ms_to_ktime(timeout_ms));
133 	else
134 		virt_timeout = wd_data->open_deadline;
135 
136 	hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms);
137 	keepalive_interval = ms_to_ktime(hw_heartbeat_ms / 2);
138 
139 	/*
140 	 * To ensure that the watchdog times out wdd->timeout seconds
141 	 * after the most recent ping from userspace, the last
142 	 * worker ping has to come in hw_heartbeat_ms before this timeout.
143 	 */
144 	last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms));
145 	latest_heartbeat = ktime_sub(last_heartbeat, ktime_get());
146 	if (ktime_before(latest_heartbeat, keepalive_interval))
147 		return latest_heartbeat;
148 	return keepalive_interval;
149 }
150 
151 static inline void watchdog_update_worker(struct watchdog_device *wdd)
152 {
153 	struct watchdog_core_data *wd_data = wdd->wd_data;
154 
155 	if (watchdog_need_worker(wdd)) {
156 		ktime_t t = watchdog_next_keepalive(wdd);
157 
158 		if (t > 0)
159 			hrtimer_start(&wd_data->timer, t,
160 				      HRTIMER_MODE_REL_HARD);
161 	} else {
162 		hrtimer_cancel(&wd_data->timer);
163 	}
164 }
165 
166 static int __watchdog_ping(struct watchdog_device *wdd)
167 {
168 	struct watchdog_core_data *wd_data = wdd->wd_data;
169 	ktime_t earliest_keepalive, now;
170 	int err;
171 
172 	earliest_keepalive = ktime_add(wd_data->last_hw_keepalive,
173 				       ms_to_ktime(wdd->min_hw_heartbeat_ms));
174 	now = ktime_get();
175 
176 	if (ktime_after(earliest_keepalive, now)) {
177 		hrtimer_start(&wd_data->timer,
178 			      ktime_sub(earliest_keepalive, now),
179 			      HRTIMER_MODE_REL_HARD);
180 		return 0;
181 	}
182 
183 	wd_data->last_hw_keepalive = now;
184 
185 	if (wdd->ops->ping)
186 		err = wdd->ops->ping(wdd);  /* ping the watchdog */
187 	else
188 		err = wdd->ops->start(wdd); /* restart watchdog */
189 
190 	watchdog_update_worker(wdd);
191 
192 	return err;
193 }
194 
195 /*
196  *	watchdog_ping: ping the watchdog.
197  *	@wdd: the watchdog device to ping
198  *
199  *	The caller must hold wd_data->lock.
200  *
201  *	If the watchdog has no own ping operation then it needs to be
202  *	restarted via the start operation. This wrapper function does
203  *	exactly that.
204  *	We only ping when the watchdog device is running.
205  */
206 
207 static int watchdog_ping(struct watchdog_device *wdd)
208 {
209 	struct watchdog_core_data *wd_data = wdd->wd_data;
210 
211 	if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
212 		return 0;
213 
214 	set_bit(_WDOG_KEEPALIVE, &wd_data->status);
215 
216 	wd_data->last_keepalive = ktime_get();
217 	return __watchdog_ping(wdd);
218 }
219 
220 static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data)
221 {
222 	struct watchdog_device *wdd = wd_data->wdd;
223 
224 	if (!wdd)
225 		return false;
226 
227 	if (watchdog_active(wdd))
228 		return true;
229 
230 	return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data);
231 }
232 
233 static void watchdog_ping_work(struct kthread_work *work)
234 {
235 	struct watchdog_core_data *wd_data;
236 
237 	wd_data = container_of(work, struct watchdog_core_data, work);
238 
239 	mutex_lock(&wd_data->lock);
240 	if (watchdog_worker_should_ping(wd_data))
241 		__watchdog_ping(wd_data->wdd);
242 	mutex_unlock(&wd_data->lock);
243 }
244 
245 static enum hrtimer_restart watchdog_timer_expired(struct hrtimer *timer)
246 {
247 	struct watchdog_core_data *wd_data;
248 
249 	wd_data = container_of(timer, struct watchdog_core_data, timer);
250 
251 	kthread_queue_work(watchdog_kworker, &wd_data->work);
252 	return HRTIMER_NORESTART;
253 }
254 
255 /*
256  *	watchdog_start: wrapper to start the watchdog.
257  *	@wdd: the watchdog device to start
258  *
259  *	The caller must hold wd_data->lock.
260  *
261  *	Start the watchdog if it is not active and mark it active.
262  *	This function returns zero on success or a negative errno code for
263  *	failure.
264  */
265 
266 static int watchdog_start(struct watchdog_device *wdd)
267 {
268 	struct watchdog_core_data *wd_data = wdd->wd_data;
269 	ktime_t started_at;
270 	int err;
271 
272 	if (watchdog_active(wdd))
273 		return 0;
274 
275 	set_bit(_WDOG_KEEPALIVE, &wd_data->status);
276 
277 	started_at = ktime_get();
278 	if (watchdog_hw_running(wdd) && wdd->ops->ping)
279 		err = wdd->ops->ping(wdd);
280 	else
281 		err = wdd->ops->start(wdd);
282 	if (err == 0) {
283 		set_bit(WDOG_ACTIVE, &wdd->status);
284 		wd_data->last_keepalive = started_at;
285 		wd_data->last_hw_keepalive = started_at;
286 		watchdog_update_worker(wdd);
287 	}
288 
289 	return err;
290 }
291 
292 /*
293  *	watchdog_stop: wrapper to stop the watchdog.
294  *	@wdd: the watchdog device to stop
295  *
296  *	The caller must hold wd_data->lock.
297  *
298  *	Stop the watchdog if it is still active and unmark it active.
299  *	This function returns zero on success or a negative errno code for
300  *	failure.
301  *	If the 'nowayout' feature was set, the watchdog cannot be stopped.
302  */
303 
304 static int watchdog_stop(struct watchdog_device *wdd)
305 {
306 	int err = 0;
307 
308 	if (!watchdog_active(wdd))
309 		return 0;
310 
311 	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
312 		pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
313 			wdd->id);
314 		return -EBUSY;
315 	}
316 
317 	if (wdd->ops->stop) {
318 		clear_bit(WDOG_HW_RUNNING, &wdd->status);
319 		err = wdd->ops->stop(wdd);
320 	} else {
321 		set_bit(WDOG_HW_RUNNING, &wdd->status);
322 	}
323 
324 	if (err == 0) {
325 		clear_bit(WDOG_ACTIVE, &wdd->status);
326 		watchdog_update_worker(wdd);
327 	}
328 
329 	return err;
330 }
331 
332 /*
333  *	watchdog_get_status: wrapper to get the watchdog status
334  *	@wdd: the watchdog device to get the status from
335  *
336  *	The caller must hold wd_data->lock.
337  *
338  *	Get the watchdog's status flags.
339  */
340 
341 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
342 {
343 	struct watchdog_core_data *wd_data = wdd->wd_data;
344 	unsigned int status;
345 
346 	if (wdd->ops->status)
347 		status = wdd->ops->status(wdd);
348 	else
349 		status = wdd->bootstatus & (WDIOF_CARDRESET |
350 					    WDIOF_OVERHEAT |
351 					    WDIOF_FANFAULT |
352 					    WDIOF_EXTERN1 |
353 					    WDIOF_EXTERN2 |
354 					    WDIOF_POWERUNDER |
355 					    WDIOF_POWEROVER);
356 
357 	if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
358 		status |= WDIOF_MAGICCLOSE;
359 
360 	if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
361 		status |= WDIOF_KEEPALIVEPING;
362 
363 	return status;
364 }
365 
366 /*
367  *	watchdog_set_timeout: set the watchdog timer timeout
368  *	@wdd: the watchdog device to set the timeout for
369  *	@timeout: timeout to set in seconds
370  *
371  *	The caller must hold wd_data->lock.
372  */
373 
374 static int watchdog_set_timeout(struct watchdog_device *wdd,
375 							unsigned int timeout)
376 {
377 	int err = 0;
378 
379 	if (!(wdd->info->options & WDIOF_SETTIMEOUT))
380 		return -EOPNOTSUPP;
381 
382 	if (watchdog_timeout_invalid(wdd, timeout))
383 		return -EINVAL;
384 
385 	if (wdd->ops->set_timeout) {
386 		err = wdd->ops->set_timeout(wdd, timeout);
387 	} else {
388 		wdd->timeout = timeout;
389 		/* Disable pretimeout if it doesn't fit the new timeout */
390 		if (wdd->pretimeout >= wdd->timeout)
391 			wdd->pretimeout = 0;
392 	}
393 
394 	watchdog_update_worker(wdd);
395 
396 	return err;
397 }
398 
399 /*
400  *	watchdog_set_pretimeout: set the watchdog timer pretimeout
401  *	@wdd: the watchdog device to set the timeout for
402  *	@timeout: pretimeout to set in seconds
403  */
404 
405 static int watchdog_set_pretimeout(struct watchdog_device *wdd,
406 				   unsigned int timeout)
407 {
408 	int err = 0;
409 
410 	if (!(wdd->info->options & WDIOF_PRETIMEOUT))
411 		return -EOPNOTSUPP;
412 
413 	if (watchdog_pretimeout_invalid(wdd, timeout))
414 		return -EINVAL;
415 
416 	if (wdd->ops->set_pretimeout)
417 		err = wdd->ops->set_pretimeout(wdd, timeout);
418 	else
419 		wdd->pretimeout = timeout;
420 
421 	return err;
422 }
423 
424 /*
425  *	watchdog_get_timeleft: wrapper to get the time left before a reboot
426  *	@wdd: the watchdog device to get the remaining time from
427  *	@timeleft: the time that's left
428  *
429  *	The caller must hold wd_data->lock.
430  *
431  *	Get the time before a watchdog will reboot (if not pinged).
432  */
433 
434 static int watchdog_get_timeleft(struct watchdog_device *wdd,
435 							unsigned int *timeleft)
436 {
437 	*timeleft = 0;
438 
439 	if (!wdd->ops->get_timeleft)
440 		return -EOPNOTSUPP;
441 
442 	*timeleft = wdd->ops->get_timeleft(wdd);
443 
444 	return 0;
445 }
446 
447 #ifdef CONFIG_WATCHDOG_SYSFS
448 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
449 				char *buf)
450 {
451 	struct watchdog_device *wdd = dev_get_drvdata(dev);
452 
453 	return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
454 }
455 
456 static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,
457 				const char *buf, size_t len)
458 {
459 	struct watchdog_device *wdd = dev_get_drvdata(dev);
460 	unsigned int value;
461 	int ret;
462 
463 	ret = kstrtouint(buf, 0, &value);
464 	if (ret)
465 		return ret;
466 	if (value > 1)
467 		return -EINVAL;
468 	/* nowayout cannot be disabled once set */
469 	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)
470 		return -EPERM;
471 	watchdog_set_nowayout(wdd, value);
472 	return len;
473 }
474 static DEVICE_ATTR_RW(nowayout);
475 
476 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
477 				char *buf)
478 {
479 	struct watchdog_device *wdd = dev_get_drvdata(dev);
480 	struct watchdog_core_data *wd_data = wdd->wd_data;
481 	unsigned int status;
482 
483 	mutex_lock(&wd_data->lock);
484 	status = watchdog_get_status(wdd);
485 	mutex_unlock(&wd_data->lock);
486 
487 	return sprintf(buf, "0x%x\n", status);
488 }
489 static DEVICE_ATTR_RO(status);
490 
491 static ssize_t bootstatus_show(struct device *dev,
492 				struct device_attribute *attr, char *buf)
493 {
494 	struct watchdog_device *wdd = dev_get_drvdata(dev);
495 
496 	return sprintf(buf, "%u\n", wdd->bootstatus);
497 }
498 static DEVICE_ATTR_RO(bootstatus);
499 
500 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
501 				char *buf)
502 {
503 	struct watchdog_device *wdd = dev_get_drvdata(dev);
504 	struct watchdog_core_data *wd_data = wdd->wd_data;
505 	ssize_t status;
506 	unsigned int val;
507 
508 	mutex_lock(&wd_data->lock);
509 	status = watchdog_get_timeleft(wdd, &val);
510 	mutex_unlock(&wd_data->lock);
511 	if (!status)
512 		status = sprintf(buf, "%u\n", val);
513 
514 	return status;
515 }
516 static DEVICE_ATTR_RO(timeleft);
517 
518 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
519 				char *buf)
520 {
521 	struct watchdog_device *wdd = dev_get_drvdata(dev);
522 
523 	return sprintf(buf, "%u\n", wdd->timeout);
524 }
525 static DEVICE_ATTR_RO(timeout);
526 
527 static ssize_t pretimeout_show(struct device *dev,
528 			       struct device_attribute *attr, char *buf)
529 {
530 	struct watchdog_device *wdd = dev_get_drvdata(dev);
531 
532 	return sprintf(buf, "%u\n", wdd->pretimeout);
533 }
534 static DEVICE_ATTR_RO(pretimeout);
535 
536 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
537 				char *buf)
538 {
539 	struct watchdog_device *wdd = dev_get_drvdata(dev);
540 
541 	return sprintf(buf, "%s\n", wdd->info->identity);
542 }
543 static DEVICE_ATTR_RO(identity);
544 
545 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
546 				char *buf)
547 {
548 	struct watchdog_device *wdd = dev_get_drvdata(dev);
549 
550 	if (watchdog_active(wdd))
551 		return sprintf(buf, "active\n");
552 
553 	return sprintf(buf, "inactive\n");
554 }
555 static DEVICE_ATTR_RO(state);
556 
557 static ssize_t pretimeout_available_governors_show(struct device *dev,
558 				   struct device_attribute *attr, char *buf)
559 {
560 	return watchdog_pretimeout_available_governors_get(buf);
561 }
562 static DEVICE_ATTR_RO(pretimeout_available_governors);
563 
564 static ssize_t pretimeout_governor_show(struct device *dev,
565 					struct device_attribute *attr,
566 					char *buf)
567 {
568 	struct watchdog_device *wdd = dev_get_drvdata(dev);
569 
570 	return watchdog_pretimeout_governor_get(wdd, buf);
571 }
572 
573 static ssize_t pretimeout_governor_store(struct device *dev,
574 					 struct device_attribute *attr,
575 					 const char *buf, size_t count)
576 {
577 	struct watchdog_device *wdd = dev_get_drvdata(dev);
578 	int ret = watchdog_pretimeout_governor_set(wdd, buf);
579 
580 	if (!ret)
581 		ret = count;
582 
583 	return ret;
584 }
585 static DEVICE_ATTR_RW(pretimeout_governor);
586 
587 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
588 				int n)
589 {
590 	struct device *dev = container_of(kobj, struct device, kobj);
591 	struct watchdog_device *wdd = dev_get_drvdata(dev);
592 	umode_t mode = attr->mode;
593 
594 	if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
595 		mode = 0;
596 	else if (attr == &dev_attr_pretimeout.attr &&
597 		 !(wdd->info->options & WDIOF_PRETIMEOUT))
598 		mode = 0;
599 	else if ((attr == &dev_attr_pretimeout_governor.attr ||
600 		  attr == &dev_attr_pretimeout_available_governors.attr) &&
601 		 (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
602 		  !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
603 		mode = 0;
604 
605 	return mode;
606 }
607 static struct attribute *wdt_attrs[] = {
608 	&dev_attr_state.attr,
609 	&dev_attr_identity.attr,
610 	&dev_attr_timeout.attr,
611 	&dev_attr_pretimeout.attr,
612 	&dev_attr_timeleft.attr,
613 	&dev_attr_bootstatus.attr,
614 	&dev_attr_status.attr,
615 	&dev_attr_nowayout.attr,
616 	&dev_attr_pretimeout_governor.attr,
617 	&dev_attr_pretimeout_available_governors.attr,
618 	NULL,
619 };
620 
621 static const struct attribute_group wdt_group = {
622 	.attrs = wdt_attrs,
623 	.is_visible = wdt_is_visible,
624 };
625 __ATTRIBUTE_GROUPS(wdt);
626 #else
627 #define wdt_groups	NULL
628 #endif
629 
630 /*
631  *	watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
632  *	@wdd: the watchdog device to do the ioctl on
633  *	@cmd: watchdog command
634  *	@arg: argument pointer
635  *
636  *	The caller must hold wd_data->lock.
637  */
638 
639 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
640 							unsigned long arg)
641 {
642 	if (!wdd->ops->ioctl)
643 		return -ENOIOCTLCMD;
644 
645 	return wdd->ops->ioctl(wdd, cmd, arg);
646 }
647 
648 /*
649  *	watchdog_write: writes to the watchdog.
650  *	@file: file from VFS
651  *	@data: user address of data
652  *	@len: length of data
653  *	@ppos: pointer to the file offset
654  *
655  *	A write to a watchdog device is defined as a keepalive ping.
656  *	Writing the magic 'V' sequence allows the next close to turn
657  *	off the watchdog (if 'nowayout' is not set).
658  */
659 
660 static ssize_t watchdog_write(struct file *file, const char __user *data,
661 						size_t len, loff_t *ppos)
662 {
663 	struct watchdog_core_data *wd_data = file->private_data;
664 	struct watchdog_device *wdd;
665 	int err;
666 	size_t i;
667 	char c;
668 
669 	if (len == 0)
670 		return 0;
671 
672 	/*
673 	 * Note: just in case someone wrote the magic character
674 	 * five months ago...
675 	 */
676 	clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
677 
678 	/* scan to see whether or not we got the magic character */
679 	for (i = 0; i != len; i++) {
680 		if (get_user(c, data + i))
681 			return -EFAULT;
682 		if (c == 'V')
683 			set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
684 	}
685 
686 	/* someone wrote to us, so we send the watchdog a keepalive ping */
687 
688 	err = -ENODEV;
689 	mutex_lock(&wd_data->lock);
690 	wdd = wd_data->wdd;
691 	if (wdd)
692 		err = watchdog_ping(wdd);
693 	mutex_unlock(&wd_data->lock);
694 
695 	if (err < 0)
696 		return err;
697 
698 	return len;
699 }
700 
701 /*
702  *	watchdog_ioctl: handle the different ioctl's for the watchdog device.
703  *	@file: file handle to the device
704  *	@cmd: watchdog command
705  *	@arg: argument pointer
706  *
707  *	The watchdog API defines a common set of functions for all watchdogs
708  *	according to their available features.
709  */
710 
711 static long watchdog_ioctl(struct file *file, unsigned int cmd,
712 							unsigned long arg)
713 {
714 	struct watchdog_core_data *wd_data = file->private_data;
715 	void __user *argp = (void __user *)arg;
716 	struct watchdog_device *wdd;
717 	int __user *p = argp;
718 	unsigned int val;
719 	int err;
720 
721 	mutex_lock(&wd_data->lock);
722 
723 	wdd = wd_data->wdd;
724 	if (!wdd) {
725 		err = -ENODEV;
726 		goto out_ioctl;
727 	}
728 
729 	err = watchdog_ioctl_op(wdd, cmd, arg);
730 	if (err != -ENOIOCTLCMD)
731 		goto out_ioctl;
732 
733 	switch (cmd) {
734 	case WDIOC_GETSUPPORT:
735 		err = copy_to_user(argp, wdd->info,
736 			sizeof(struct watchdog_info)) ? -EFAULT : 0;
737 		break;
738 	case WDIOC_GETSTATUS:
739 		val = watchdog_get_status(wdd);
740 		err = put_user(val, p);
741 		break;
742 	case WDIOC_GETBOOTSTATUS:
743 		err = put_user(wdd->bootstatus, p);
744 		break;
745 	case WDIOC_SETOPTIONS:
746 		if (get_user(val, p)) {
747 			err = -EFAULT;
748 			break;
749 		}
750 		if (val & WDIOS_DISABLECARD) {
751 			err = watchdog_stop(wdd);
752 			if (err < 0)
753 				break;
754 		}
755 		if (val & WDIOS_ENABLECARD)
756 			err = watchdog_start(wdd);
757 		break;
758 	case WDIOC_KEEPALIVE:
759 		if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
760 			err = -EOPNOTSUPP;
761 			break;
762 		}
763 		err = watchdog_ping(wdd);
764 		break;
765 	case WDIOC_SETTIMEOUT:
766 		if (get_user(val, p)) {
767 			err = -EFAULT;
768 			break;
769 		}
770 		err = watchdog_set_timeout(wdd, val);
771 		if (err < 0)
772 			break;
773 		/* If the watchdog is active then we send a keepalive ping
774 		 * to make sure that the watchdog keep's running (and if
775 		 * possible that it takes the new timeout) */
776 		err = watchdog_ping(wdd);
777 		if (err < 0)
778 			break;
779 		/* fall through */
780 	case WDIOC_GETTIMEOUT:
781 		/* timeout == 0 means that we don't know the timeout */
782 		if (wdd->timeout == 0) {
783 			err = -EOPNOTSUPP;
784 			break;
785 		}
786 		err = put_user(wdd->timeout, p);
787 		break;
788 	case WDIOC_GETTIMELEFT:
789 		err = watchdog_get_timeleft(wdd, &val);
790 		if (err < 0)
791 			break;
792 		err = put_user(val, p);
793 		break;
794 	case WDIOC_SETPRETIMEOUT:
795 		if (get_user(val, p)) {
796 			err = -EFAULT;
797 			break;
798 		}
799 		err = watchdog_set_pretimeout(wdd, val);
800 		break;
801 	case WDIOC_GETPRETIMEOUT:
802 		err = put_user(wdd->pretimeout, p);
803 		break;
804 	default:
805 		err = -ENOTTY;
806 		break;
807 	}
808 
809 out_ioctl:
810 	mutex_unlock(&wd_data->lock);
811 	return err;
812 }
813 
814 /*
815  *	watchdog_open: open the /dev/watchdog* devices.
816  *	@inode: inode of device
817  *	@file: file handle to device
818  *
819  *	When the /dev/watchdog* device gets opened, we start the watchdog.
820  *	Watch out: the /dev/watchdog device is single open, so we make sure
821  *	it can only be opened once.
822  */
823 
824 static int watchdog_open(struct inode *inode, struct file *file)
825 {
826 	struct watchdog_core_data *wd_data;
827 	struct watchdog_device *wdd;
828 	bool hw_running;
829 	int err;
830 
831 	/* Get the corresponding watchdog device */
832 	if (imajor(inode) == MISC_MAJOR)
833 		wd_data = old_wd_data;
834 	else
835 		wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
836 				       cdev);
837 
838 	/* the watchdog is single open! */
839 	if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
840 		return -EBUSY;
841 
842 	wdd = wd_data->wdd;
843 
844 	/*
845 	 * If the /dev/watchdog device is open, we don't want the module
846 	 * to be unloaded.
847 	 */
848 	hw_running = watchdog_hw_running(wdd);
849 	if (!hw_running && !try_module_get(wdd->ops->owner)) {
850 		err = -EBUSY;
851 		goto out_clear;
852 	}
853 
854 	err = watchdog_start(wdd);
855 	if (err < 0)
856 		goto out_mod;
857 
858 	file->private_data = wd_data;
859 
860 	if (!hw_running)
861 		get_device(&wd_data->dev);
862 
863 	/*
864 	 * open_timeout only applies for the first open from
865 	 * userspace. Set open_deadline to infinity so that the kernel
866 	 * will take care of an always-running hardware watchdog in
867 	 * case the device gets magic-closed or WDIOS_DISABLECARD is
868 	 * applied.
869 	 */
870 	wd_data->open_deadline = KTIME_MAX;
871 
872 	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
873 	return stream_open(inode, file);
874 
875 out_mod:
876 	module_put(wd_data->wdd->ops->owner);
877 out_clear:
878 	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
879 	return err;
880 }
881 
882 static void watchdog_core_data_release(struct device *dev)
883 {
884 	struct watchdog_core_data *wd_data;
885 
886 	wd_data = container_of(dev, struct watchdog_core_data, dev);
887 
888 	kfree(wd_data);
889 }
890 
891 /*
892  *	watchdog_release: release the watchdog device.
893  *	@inode: inode of device
894  *	@file: file handle to device
895  *
896  *	This is the code for when /dev/watchdog gets closed. We will only
897  *	stop the watchdog when we have received the magic char (and nowayout
898  *	was not set), else the watchdog will keep running.
899  */
900 
901 static int watchdog_release(struct inode *inode, struct file *file)
902 {
903 	struct watchdog_core_data *wd_data = file->private_data;
904 	struct watchdog_device *wdd;
905 	int err = -EBUSY;
906 	bool running;
907 
908 	mutex_lock(&wd_data->lock);
909 
910 	wdd = wd_data->wdd;
911 	if (!wdd)
912 		goto done;
913 
914 	/*
915 	 * We only stop the watchdog if we received the magic character
916 	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
917 	 * watchdog_stop will fail.
918 	 */
919 	if (!test_bit(WDOG_ACTIVE, &wdd->status))
920 		err = 0;
921 	else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
922 		 !(wdd->info->options & WDIOF_MAGICCLOSE))
923 		err = watchdog_stop(wdd);
924 
925 	/* If the watchdog was not stopped, send a keepalive ping */
926 	if (err < 0) {
927 		pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
928 		watchdog_ping(wdd);
929 	}
930 
931 	watchdog_update_worker(wdd);
932 
933 	/* make sure that /dev/watchdog can be re-opened */
934 	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
935 
936 done:
937 	running = wdd && watchdog_hw_running(wdd);
938 	mutex_unlock(&wd_data->lock);
939 	/*
940 	 * Allow the owner module to be unloaded again unless the watchdog
941 	 * is still running. If the watchdog is still running, it can not
942 	 * be stopped, and its driver must not be unloaded.
943 	 */
944 	if (!running) {
945 		module_put(wd_data->cdev.owner);
946 		put_device(&wd_data->dev);
947 	}
948 	return 0;
949 }
950 
951 static const struct file_operations watchdog_fops = {
952 	.owner		= THIS_MODULE,
953 	.write		= watchdog_write,
954 	.unlocked_ioctl	= watchdog_ioctl,
955 	.compat_ioctl	= compat_ptr_ioctl,
956 	.open		= watchdog_open,
957 	.release	= watchdog_release,
958 };
959 
960 static struct miscdevice watchdog_miscdev = {
961 	.minor		= WATCHDOG_MINOR,
962 	.name		= "watchdog",
963 	.fops		= &watchdog_fops,
964 };
965 
966 static struct class watchdog_class = {
967 	.name =		"watchdog",
968 	.owner =	THIS_MODULE,
969 	.dev_groups =	wdt_groups,
970 };
971 
972 /*
973  *	watchdog_cdev_register: register watchdog character device
974  *	@wdd: watchdog device
975  *
976  *	Register a watchdog character device including handling the legacy
977  *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
978  *	thus we set it up like that.
979  */
980 
981 static int watchdog_cdev_register(struct watchdog_device *wdd)
982 {
983 	struct watchdog_core_data *wd_data;
984 	int err;
985 
986 	wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
987 	if (!wd_data)
988 		return -ENOMEM;
989 	mutex_init(&wd_data->lock);
990 
991 	wd_data->wdd = wdd;
992 	wdd->wd_data = wd_data;
993 
994 	if (IS_ERR_OR_NULL(watchdog_kworker))
995 		return -ENODEV;
996 
997 	kthread_init_work(&wd_data->work, watchdog_ping_work);
998 	hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
999 	wd_data->timer.function = watchdog_timer_expired;
1000 
1001 	if (wdd->id == 0) {
1002 		old_wd_data = wd_data;
1003 		watchdog_miscdev.parent = wdd->parent;
1004 		err = misc_register(&watchdog_miscdev);
1005 		if (err != 0) {
1006 			pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
1007 				wdd->info->identity, WATCHDOG_MINOR, err);
1008 			if (err == -EBUSY)
1009 				pr_err("%s: a legacy watchdog module is probably present.\n",
1010 					wdd->info->identity);
1011 			old_wd_data = NULL;
1012 			kfree(wd_data);
1013 			return err;
1014 		}
1015 	}
1016 
1017 	device_initialize(&wd_data->dev);
1018 	wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
1019 	wd_data->dev.class = &watchdog_class;
1020 	wd_data->dev.parent = wdd->parent;
1021 	wd_data->dev.groups = wdd->groups;
1022 	wd_data->dev.release = watchdog_core_data_release;
1023 	dev_set_drvdata(&wd_data->dev, wdd);
1024 	dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
1025 
1026 	/* Fill in the data structures */
1027 	cdev_init(&wd_data->cdev, &watchdog_fops);
1028 
1029 	/* Add the device */
1030 	err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1031 	if (err) {
1032 		pr_err("watchdog%d unable to add device %d:%d\n",
1033 			wdd->id,  MAJOR(watchdog_devt), wdd->id);
1034 		if (wdd->id == 0) {
1035 			misc_deregister(&watchdog_miscdev);
1036 			old_wd_data = NULL;
1037 			put_device(&wd_data->dev);
1038 		}
1039 		return err;
1040 	}
1041 
1042 	wd_data->cdev.owner = wdd->ops->owner;
1043 
1044 	/* Record time of most recent heartbeat as 'just before now'. */
1045 	wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1046 	watchdog_set_open_deadline(wd_data);
1047 
1048 	/*
1049 	 * If the watchdog is running, prevent its driver from being unloaded,
1050 	 * and schedule an immediate ping.
1051 	 */
1052 	if (watchdog_hw_running(wdd)) {
1053 		__module_get(wdd->ops->owner);
1054 		get_device(&wd_data->dev);
1055 		if (handle_boot_enabled)
1056 			hrtimer_start(&wd_data->timer, 0,
1057 				      HRTIMER_MODE_REL_HARD);
1058 		else
1059 			pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1060 				wdd->id);
1061 	}
1062 
1063 	return 0;
1064 }
1065 
1066 /*
1067  *	watchdog_cdev_unregister: unregister watchdog character device
1068  *	@watchdog: watchdog device
1069  *
1070  *	Unregister watchdog character device and if needed the legacy
1071  *	/dev/watchdog device.
1072  */
1073 
1074 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1075 {
1076 	struct watchdog_core_data *wd_data = wdd->wd_data;
1077 
1078 	cdev_device_del(&wd_data->cdev, &wd_data->dev);
1079 	if (wdd->id == 0) {
1080 		misc_deregister(&watchdog_miscdev);
1081 		old_wd_data = NULL;
1082 	}
1083 
1084 	if (watchdog_active(wdd) &&
1085 	    test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1086 		watchdog_stop(wdd);
1087 	}
1088 
1089 	mutex_lock(&wd_data->lock);
1090 	wd_data->wdd = NULL;
1091 	wdd->wd_data = NULL;
1092 	mutex_unlock(&wd_data->lock);
1093 
1094 	hrtimer_cancel(&wd_data->timer);
1095 	kthread_cancel_work_sync(&wd_data->work);
1096 
1097 	put_device(&wd_data->dev);
1098 }
1099 
1100 /*
1101  *	watchdog_dev_register: register a watchdog device
1102  *	@wdd: watchdog device
1103  *
1104  *	Register a watchdog device including handling the legacy
1105  *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
1106  *	thus we set it up like that.
1107  */
1108 
1109 int watchdog_dev_register(struct watchdog_device *wdd)
1110 {
1111 	int ret;
1112 
1113 	ret = watchdog_cdev_register(wdd);
1114 	if (ret)
1115 		return ret;
1116 
1117 	ret = watchdog_register_pretimeout(wdd);
1118 	if (ret)
1119 		watchdog_cdev_unregister(wdd);
1120 
1121 	return ret;
1122 }
1123 
1124 /*
1125  *	watchdog_dev_unregister: unregister a watchdog device
1126  *	@watchdog: watchdog device
1127  *
1128  *	Unregister watchdog device and if needed the legacy
1129  *	/dev/watchdog device.
1130  */
1131 
1132 void watchdog_dev_unregister(struct watchdog_device *wdd)
1133 {
1134 	watchdog_unregister_pretimeout(wdd);
1135 	watchdog_cdev_unregister(wdd);
1136 }
1137 
1138 /*
1139  *	watchdog_dev_init: init dev part of watchdog core
1140  *
1141  *	Allocate a range of chardev nodes to use for watchdog devices
1142  */
1143 
1144 int __init watchdog_dev_init(void)
1145 {
1146 	int err;
1147 	struct sched_param param = {.sched_priority = MAX_RT_PRIO - 1,};
1148 
1149 	watchdog_kworker = kthread_create_worker(0, "watchdogd");
1150 	if (IS_ERR(watchdog_kworker)) {
1151 		pr_err("Failed to create watchdog kworker\n");
1152 		return PTR_ERR(watchdog_kworker);
1153 	}
1154 	sched_setscheduler(watchdog_kworker->task, SCHED_FIFO, &param);
1155 
1156 	err = class_register(&watchdog_class);
1157 	if (err < 0) {
1158 		pr_err("couldn't register class\n");
1159 		goto err_register;
1160 	}
1161 
1162 	err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1163 	if (err < 0) {
1164 		pr_err("watchdog: unable to allocate char dev region\n");
1165 		goto err_alloc;
1166 	}
1167 
1168 	return 0;
1169 
1170 err_alloc:
1171 	class_unregister(&watchdog_class);
1172 err_register:
1173 	kthread_destroy_worker(watchdog_kworker);
1174 	return err;
1175 }
1176 
1177 /*
1178  *	watchdog_dev_exit: exit dev part of watchdog core
1179  *
1180  *	Release the range of chardev nodes used for watchdog devices
1181  */
1182 
1183 void __exit watchdog_dev_exit(void)
1184 {
1185 	unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1186 	class_unregister(&watchdog_class);
1187 	kthread_destroy_worker(watchdog_kworker);
1188 }
1189 
1190 module_param(handle_boot_enabled, bool, 0444);
1191 MODULE_PARM_DESC(handle_boot_enabled,
1192 	"Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1193 	__MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1194 
1195 module_param(open_timeout, uint, 0644);
1196 MODULE_PARM_DESC(open_timeout,
1197 	"Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1198 	__MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");
1199