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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 "watchdog_core.h"
47 #include "watchdog_pretimeout.h"
48 
49 /*
50  * struct watchdog_core_data - watchdog core internal data
51  * @dev:	The watchdog's internal device
52  * @cdev:	The watchdog's Character device.
53  * @wdd:	Pointer to watchdog device.
54  * @lock:	Lock for watchdog core.
55  * @status:	Watchdog core internal status bits.
56  */
57 struct watchdog_core_data {
58 	struct device dev;
59 	struct cdev cdev;
60 	struct watchdog_device *wdd;
61 	struct mutex lock;
62 	ktime_t last_keepalive;
63 	ktime_t last_hw_keepalive;
64 	ktime_t open_deadline;
65 	struct hrtimer timer;
66 	struct kthread_work work;
67 	unsigned long status;		/* Internal status bits */
68 #define _WDOG_DEV_OPEN		0	/* Opened ? */
69 #define _WDOG_ALLOW_RELEASE	1	/* Did we receive the magic char ? */
70 #define _WDOG_KEEPALIVE		2	/* Did we receive a keepalive ? */
71 };
72 
73 /* the dev_t structure to store the dynamically allocated watchdog devices */
74 static dev_t watchdog_devt;
75 /* Reference to watchdog device behind /dev/watchdog */
76 static struct watchdog_core_data *old_wd_data;
77 
78 static struct kthread_worker *watchdog_kworker;
79 
80 static bool handle_boot_enabled =
81 	IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
82 
83 static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
84 
watchdog_past_open_deadline(struct watchdog_core_data * data)85 static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
86 {
87 	return ktime_after(ktime_get(), data->open_deadline);
88 }
89 
watchdog_set_open_deadline(struct watchdog_core_data * data)90 static void watchdog_set_open_deadline(struct watchdog_core_data *data)
91 {
92 	data->open_deadline = open_timeout ?
93 		ktime_get() + ktime_set(open_timeout, 0) : KTIME_MAX;
94 }
95 
watchdog_need_worker(struct watchdog_device * wdd)96 static inline bool watchdog_need_worker(struct watchdog_device *wdd)
97 {
98 	/* All variables in milli-seconds */
99 	unsigned int hm = wdd->max_hw_heartbeat_ms;
100 	unsigned int t = wdd->timeout * 1000;
101 
102 	/*
103 	 * A worker to generate heartbeat requests is needed if all of the
104 	 * following conditions are true.
105 	 * - Userspace activated the watchdog.
106 	 * - The driver provided a value for the maximum hardware timeout, and
107 	 *   thus is aware that the framework supports generating heartbeat
108 	 *   requests.
109 	 * - Userspace requests a longer timeout than the hardware can handle.
110 	 *
111 	 * Alternatively, if userspace has not opened the watchdog
112 	 * device, we take care of feeding the watchdog if it is
113 	 * running.
114 	 */
115 	return (hm && watchdog_active(wdd) && t > hm) ||
116 		(t && !watchdog_active(wdd) && watchdog_hw_running(wdd));
117 }
118 
watchdog_next_keepalive(struct watchdog_device * wdd)119 static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
120 {
121 	struct watchdog_core_data *wd_data = wdd->wd_data;
122 	unsigned int timeout_ms = wdd->timeout * 1000;
123 	ktime_t keepalive_interval;
124 	ktime_t last_heartbeat, latest_heartbeat;
125 	ktime_t virt_timeout;
126 	unsigned int hw_heartbeat_ms;
127 
128 	if (watchdog_active(wdd))
129 		virt_timeout = ktime_add(wd_data->last_keepalive,
130 					 ms_to_ktime(timeout_ms));
131 	else
132 		virt_timeout = wd_data->open_deadline;
133 
134 	hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms);
135 	keepalive_interval = ms_to_ktime(hw_heartbeat_ms / 2);
136 
137 	/*
138 	 * To ensure that the watchdog times out wdd->timeout seconds
139 	 * after the most recent ping from userspace, the last
140 	 * worker ping has to come in hw_heartbeat_ms before this timeout.
141 	 */
142 	last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms));
143 	latest_heartbeat = ktime_sub(last_heartbeat, ktime_get());
144 	if (ktime_before(latest_heartbeat, keepalive_interval))
145 		return latest_heartbeat;
146 	return keepalive_interval;
147 }
148 
watchdog_update_worker(struct watchdog_device * wdd)149 static inline void watchdog_update_worker(struct watchdog_device *wdd)
150 {
151 	struct watchdog_core_data *wd_data = wdd->wd_data;
152 
153 	if (watchdog_need_worker(wdd)) {
154 		ktime_t t = watchdog_next_keepalive(wdd);
155 
156 		if (t > 0)
157 			hrtimer_start(&wd_data->timer, t,
158 				      HRTIMER_MODE_REL_HARD);
159 	} else {
160 		hrtimer_cancel(&wd_data->timer);
161 	}
162 }
163 
__watchdog_ping(struct watchdog_device * wdd)164 static int __watchdog_ping(struct watchdog_device *wdd)
165 {
166 	struct watchdog_core_data *wd_data = wdd->wd_data;
167 	ktime_t earliest_keepalive, now;
168 	int err;
169 
170 	earliest_keepalive = ktime_add(wd_data->last_hw_keepalive,
171 				       ms_to_ktime(wdd->min_hw_heartbeat_ms));
172 	now = ktime_get();
173 
174 	if (ktime_after(earliest_keepalive, now)) {
175 		hrtimer_start(&wd_data->timer,
176 			      ktime_sub(earliest_keepalive, now),
177 			      HRTIMER_MODE_REL_HARD);
178 		return 0;
179 	}
180 
181 	wd_data->last_hw_keepalive = now;
182 
183 	if (wdd->ops->ping)
184 		err = wdd->ops->ping(wdd);  /* ping the watchdog */
185 	else
186 		err = wdd->ops->start(wdd); /* restart watchdog */
187 
188 	watchdog_update_worker(wdd);
189 
190 	return err;
191 }
192 
193 /*
194  *	watchdog_ping: ping the watchdog.
195  *	@wdd: the watchdog device to ping
196  *
197  *	The caller must hold wd_data->lock.
198  *
199  *	If the watchdog has no own ping operation then it needs to be
200  *	restarted via the start operation. This wrapper function does
201  *	exactly that.
202  *	We only ping when the watchdog device is running.
203  */
204 
watchdog_ping(struct watchdog_device * wdd)205 static int watchdog_ping(struct watchdog_device *wdd)
206 {
207 	struct watchdog_core_data *wd_data = wdd->wd_data;
208 
209 	if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
210 		return 0;
211 
212 	set_bit(_WDOG_KEEPALIVE, &wd_data->status);
213 
214 	wd_data->last_keepalive = ktime_get();
215 	return __watchdog_ping(wdd);
216 }
217 
watchdog_worker_should_ping(struct watchdog_core_data * wd_data)218 static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data)
219 {
220 	struct watchdog_device *wdd = wd_data->wdd;
221 
222 	if (!wdd)
223 		return false;
224 
225 	if (watchdog_active(wdd))
226 		return true;
227 
228 	return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data);
229 }
230 
watchdog_ping_work(struct kthread_work * work)231 static void watchdog_ping_work(struct kthread_work *work)
232 {
233 	struct watchdog_core_data *wd_data;
234 
235 	wd_data = container_of(work, struct watchdog_core_data, work);
236 
237 	mutex_lock(&wd_data->lock);
238 	if (watchdog_worker_should_ping(wd_data))
239 		__watchdog_ping(wd_data->wdd);
240 	mutex_unlock(&wd_data->lock);
241 }
242 
watchdog_timer_expired(struct hrtimer * timer)243 static enum hrtimer_restart watchdog_timer_expired(struct hrtimer *timer)
244 {
245 	struct watchdog_core_data *wd_data;
246 
247 	wd_data = container_of(timer, struct watchdog_core_data, timer);
248 
249 	kthread_queue_work(watchdog_kworker, &wd_data->work);
250 	return HRTIMER_NORESTART;
251 }
252 
253 /*
254  *	watchdog_start: wrapper to start the watchdog.
255  *	@wdd: the watchdog device to start
256  *
257  *	The caller must hold wd_data->lock.
258  *
259  *	Start the watchdog if it is not active and mark it active.
260  *	This function returns zero on success or a negative errno code for
261  *	failure.
262  */
263 
watchdog_start(struct watchdog_device * wdd)264 static int watchdog_start(struct watchdog_device *wdd)
265 {
266 	struct watchdog_core_data *wd_data = wdd->wd_data;
267 	ktime_t started_at;
268 	int err;
269 
270 	if (watchdog_active(wdd))
271 		return 0;
272 
273 	set_bit(_WDOG_KEEPALIVE, &wd_data->status);
274 
275 	started_at = ktime_get();
276 	if (watchdog_hw_running(wdd) && wdd->ops->ping) {
277 		err = __watchdog_ping(wdd);
278 		if (err == 0)
279 			set_bit(WDOG_ACTIVE, &wdd->status);
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 
290 	return err;
291 }
292 
293 /*
294  *	watchdog_stop: wrapper to stop the watchdog.
295  *	@wdd: the watchdog device to stop
296  *
297  *	The caller must hold wd_data->lock.
298  *
299  *	Stop the watchdog if it is still active and unmark it active.
300  *	This function returns zero on success or a negative errno code for
301  *	failure.
302  *	If the 'nowayout' feature was set, the watchdog cannot be stopped.
303  */
304 
watchdog_stop(struct watchdog_device * wdd)305 static int watchdog_stop(struct watchdog_device *wdd)
306 {
307 	int err = 0;
308 
309 	if (!watchdog_active(wdd))
310 		return 0;
311 
312 	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
313 		pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
314 			wdd->id);
315 		return -EBUSY;
316 	}
317 
318 	if (wdd->ops->stop) {
319 		clear_bit(WDOG_HW_RUNNING, &wdd->status);
320 		err = wdd->ops->stop(wdd);
321 	} else {
322 		set_bit(WDOG_HW_RUNNING, &wdd->status);
323 	}
324 
325 	if (err == 0) {
326 		clear_bit(WDOG_ACTIVE, &wdd->status);
327 		watchdog_update_worker(wdd);
328 	}
329 
330 	return err;
331 }
332 
333 /*
334  *	watchdog_get_status: wrapper to get the watchdog status
335  *	@wdd: the watchdog device to get the status from
336  *
337  *	The caller must hold wd_data->lock.
338  *
339  *	Get the watchdog's status flags.
340  */
341 
watchdog_get_status(struct watchdog_device * wdd)342 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
343 {
344 	struct watchdog_core_data *wd_data = wdd->wd_data;
345 	unsigned int status;
346 
347 	if (wdd->ops->status)
348 		status = wdd->ops->status(wdd);
349 	else
350 		status = wdd->bootstatus & (WDIOF_CARDRESET |
351 					    WDIOF_OVERHEAT |
352 					    WDIOF_FANFAULT |
353 					    WDIOF_EXTERN1 |
354 					    WDIOF_EXTERN2 |
355 					    WDIOF_POWERUNDER |
356 					    WDIOF_POWEROVER);
357 
358 	if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
359 		status |= WDIOF_MAGICCLOSE;
360 
361 	if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
362 		status |= WDIOF_KEEPALIVEPING;
363 
364 	return status;
365 }
366 
367 /*
368  *	watchdog_set_timeout: set the watchdog timer timeout
369  *	@wdd: the watchdog device to set the timeout for
370  *	@timeout: timeout to set in seconds
371  *
372  *	The caller must hold wd_data->lock.
373  */
374 
watchdog_set_timeout(struct watchdog_device * wdd,unsigned int timeout)375 static int watchdog_set_timeout(struct watchdog_device *wdd,
376 							unsigned int timeout)
377 {
378 	int err = 0;
379 
380 	if (!(wdd->info->options & WDIOF_SETTIMEOUT))
381 		return -EOPNOTSUPP;
382 
383 	if (watchdog_timeout_invalid(wdd, timeout))
384 		return -EINVAL;
385 
386 	if (wdd->ops->set_timeout) {
387 		err = wdd->ops->set_timeout(wdd, timeout);
388 	} else {
389 		wdd->timeout = timeout;
390 		/* Disable pretimeout if it doesn't fit the new timeout */
391 		if (wdd->pretimeout >= wdd->timeout)
392 			wdd->pretimeout = 0;
393 	}
394 
395 	watchdog_update_worker(wdd);
396 
397 	return err;
398 }
399 
400 /*
401  *	watchdog_set_pretimeout: set the watchdog timer pretimeout
402  *	@wdd: the watchdog device to set the timeout for
403  *	@timeout: pretimeout to set in seconds
404  */
405 
watchdog_set_pretimeout(struct watchdog_device * wdd,unsigned int timeout)406 static int watchdog_set_pretimeout(struct watchdog_device *wdd,
407 				   unsigned int timeout)
408 {
409 	int err = 0;
410 
411 	if (!(wdd->info->options & WDIOF_PRETIMEOUT))
412 		return -EOPNOTSUPP;
413 
414 	if (watchdog_pretimeout_invalid(wdd, timeout))
415 		return -EINVAL;
416 
417 	if (wdd->ops->set_pretimeout)
418 		err = wdd->ops->set_pretimeout(wdd, timeout);
419 	else
420 		wdd->pretimeout = timeout;
421 
422 	return err;
423 }
424 
425 /*
426  *	watchdog_get_timeleft: wrapper to get the time left before a reboot
427  *	@wdd: the watchdog device to get the remaining time from
428  *	@timeleft: the time that's left
429  *
430  *	The caller must hold wd_data->lock.
431  *
432  *	Get the time before a watchdog will reboot (if not pinged).
433  */
434 
watchdog_get_timeleft(struct watchdog_device * wdd,unsigned int * timeleft)435 static int watchdog_get_timeleft(struct watchdog_device *wdd,
436 							unsigned int *timeleft)
437 {
438 	*timeleft = 0;
439 
440 	if (!wdd->ops->get_timeleft)
441 		return -EOPNOTSUPP;
442 
443 	*timeleft = wdd->ops->get_timeleft(wdd);
444 
445 	return 0;
446 }
447 
448 #ifdef CONFIG_WATCHDOG_SYSFS
nowayout_show(struct device * dev,struct device_attribute * attr,char * buf)449 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
450 				char *buf)
451 {
452 	struct watchdog_device *wdd = dev_get_drvdata(dev);
453 
454 	return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
455 }
456 
nowayout_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t len)457 static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,
458 				const char *buf, size_t len)
459 {
460 	struct watchdog_device *wdd = dev_get_drvdata(dev);
461 	unsigned int value;
462 	int ret;
463 
464 	ret = kstrtouint(buf, 0, &value);
465 	if (ret)
466 		return ret;
467 	if (value > 1)
468 		return -EINVAL;
469 	/* nowayout cannot be disabled once set */
470 	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)
471 		return -EPERM;
472 	watchdog_set_nowayout(wdd, value);
473 	return len;
474 }
475 static DEVICE_ATTR_RW(nowayout);
476 
status_show(struct device * dev,struct device_attribute * attr,char * buf)477 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
478 				char *buf)
479 {
480 	struct watchdog_device *wdd = dev_get_drvdata(dev);
481 	struct watchdog_core_data *wd_data = wdd->wd_data;
482 	unsigned int status;
483 
484 	mutex_lock(&wd_data->lock);
485 	status = watchdog_get_status(wdd);
486 	mutex_unlock(&wd_data->lock);
487 
488 	return sprintf(buf, "0x%x\n", status);
489 }
490 static DEVICE_ATTR_RO(status);
491 
bootstatus_show(struct device * dev,struct device_attribute * attr,char * buf)492 static ssize_t bootstatus_show(struct device *dev,
493 				struct device_attribute *attr, char *buf)
494 {
495 	struct watchdog_device *wdd = dev_get_drvdata(dev);
496 
497 	return sprintf(buf, "%u\n", wdd->bootstatus);
498 }
499 static DEVICE_ATTR_RO(bootstatus);
500 
timeleft_show(struct device * dev,struct device_attribute * attr,char * buf)501 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
502 				char *buf)
503 {
504 	struct watchdog_device *wdd = dev_get_drvdata(dev);
505 	struct watchdog_core_data *wd_data = wdd->wd_data;
506 	ssize_t status;
507 	unsigned int val;
508 
509 	mutex_lock(&wd_data->lock);
510 	status = watchdog_get_timeleft(wdd, &val);
511 	mutex_unlock(&wd_data->lock);
512 	if (!status)
513 		status = sprintf(buf, "%u\n", val);
514 
515 	return status;
516 }
517 static DEVICE_ATTR_RO(timeleft);
518 
timeout_show(struct device * dev,struct device_attribute * attr,char * buf)519 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
520 				char *buf)
521 {
522 	struct watchdog_device *wdd = dev_get_drvdata(dev);
523 
524 	return sprintf(buf, "%u\n", wdd->timeout);
525 }
526 static DEVICE_ATTR_RO(timeout);
527 
pretimeout_show(struct device * dev,struct device_attribute * attr,char * buf)528 static ssize_t pretimeout_show(struct device *dev,
529 			       struct device_attribute *attr, char *buf)
530 {
531 	struct watchdog_device *wdd = dev_get_drvdata(dev);
532 
533 	return sprintf(buf, "%u\n", wdd->pretimeout);
534 }
535 static DEVICE_ATTR_RO(pretimeout);
536 
identity_show(struct device * dev,struct device_attribute * attr,char * buf)537 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
538 				char *buf)
539 {
540 	struct watchdog_device *wdd = dev_get_drvdata(dev);
541 
542 	return sprintf(buf, "%s\n", wdd->info->identity);
543 }
544 static DEVICE_ATTR_RO(identity);
545 
state_show(struct device * dev,struct device_attribute * attr,char * buf)546 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
547 				char *buf)
548 {
549 	struct watchdog_device *wdd = dev_get_drvdata(dev);
550 
551 	if (watchdog_active(wdd))
552 		return sprintf(buf, "active\n");
553 
554 	return sprintf(buf, "inactive\n");
555 }
556 static DEVICE_ATTR_RO(state);
557 
pretimeout_available_governors_show(struct device * dev,struct device_attribute * attr,char * buf)558 static ssize_t pretimeout_available_governors_show(struct device *dev,
559 				   struct device_attribute *attr, char *buf)
560 {
561 	return watchdog_pretimeout_available_governors_get(buf);
562 }
563 static DEVICE_ATTR_RO(pretimeout_available_governors);
564 
pretimeout_governor_show(struct device * dev,struct device_attribute * attr,char * buf)565 static ssize_t pretimeout_governor_show(struct device *dev,
566 					struct device_attribute *attr,
567 					char *buf)
568 {
569 	struct watchdog_device *wdd = dev_get_drvdata(dev);
570 
571 	return watchdog_pretimeout_governor_get(wdd, buf);
572 }
573 
pretimeout_governor_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)574 static ssize_t pretimeout_governor_store(struct device *dev,
575 					 struct device_attribute *attr,
576 					 const char *buf, size_t count)
577 {
578 	struct watchdog_device *wdd = dev_get_drvdata(dev);
579 	int ret = watchdog_pretimeout_governor_set(wdd, buf);
580 
581 	if (!ret)
582 		ret = count;
583 
584 	return ret;
585 }
586 static DEVICE_ATTR_RW(pretimeout_governor);
587 
wdt_is_visible(struct kobject * kobj,struct attribute * attr,int n)588 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
589 				int n)
590 {
591 	struct device *dev = kobj_to_dev(kobj);
592 	struct watchdog_device *wdd = dev_get_drvdata(dev);
593 	umode_t mode = attr->mode;
594 
595 	if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
596 		mode = 0;
597 	else if (attr == &dev_attr_pretimeout.attr &&
598 		 !(wdd->info->options & WDIOF_PRETIMEOUT))
599 		mode = 0;
600 	else if ((attr == &dev_attr_pretimeout_governor.attr ||
601 		  attr == &dev_attr_pretimeout_available_governors.attr) &&
602 		 (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
603 		  !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
604 		mode = 0;
605 
606 	return mode;
607 }
608 static struct attribute *wdt_attrs[] = {
609 	&dev_attr_state.attr,
610 	&dev_attr_identity.attr,
611 	&dev_attr_timeout.attr,
612 	&dev_attr_pretimeout.attr,
613 	&dev_attr_timeleft.attr,
614 	&dev_attr_bootstatus.attr,
615 	&dev_attr_status.attr,
616 	&dev_attr_nowayout.attr,
617 	&dev_attr_pretimeout_governor.attr,
618 	&dev_attr_pretimeout_available_governors.attr,
619 	NULL,
620 };
621 
622 static const struct attribute_group wdt_group = {
623 	.attrs = wdt_attrs,
624 	.is_visible = wdt_is_visible,
625 };
626 __ATTRIBUTE_GROUPS(wdt);
627 #else
628 #define wdt_groups	NULL
629 #endif
630 
631 /*
632  *	watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
633  *	@wdd: the watchdog device to do the ioctl on
634  *	@cmd: watchdog command
635  *	@arg: argument pointer
636  *
637  *	The caller must hold wd_data->lock.
638  */
639 
watchdog_ioctl_op(struct watchdog_device * wdd,unsigned int cmd,unsigned long arg)640 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
641 							unsigned long arg)
642 {
643 	if (!wdd->ops->ioctl)
644 		return -ENOIOCTLCMD;
645 
646 	return wdd->ops->ioctl(wdd, cmd, arg);
647 }
648 
649 /*
650  *	watchdog_write: writes to the watchdog.
651  *	@file: file from VFS
652  *	@data: user address of data
653  *	@len: length of data
654  *	@ppos: pointer to the file offset
655  *
656  *	A write to a watchdog device is defined as a keepalive ping.
657  *	Writing the magic 'V' sequence allows the next close to turn
658  *	off the watchdog (if 'nowayout' is not set).
659  */
660 
watchdog_write(struct file * file,const char __user * data,size_t len,loff_t * ppos)661 static ssize_t watchdog_write(struct file *file, const char __user *data,
662 						size_t len, loff_t *ppos)
663 {
664 	struct watchdog_core_data *wd_data = file->private_data;
665 	struct watchdog_device *wdd;
666 	int err;
667 	size_t i;
668 	char c;
669 
670 	if (len == 0)
671 		return 0;
672 
673 	/*
674 	 * Note: just in case someone wrote the magic character
675 	 * five months ago...
676 	 */
677 	clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
678 
679 	/* scan to see whether or not we got the magic character */
680 	for (i = 0; i != len; i++) {
681 		if (get_user(c, data + i))
682 			return -EFAULT;
683 		if (c == 'V')
684 			set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
685 	}
686 
687 	/* someone wrote to us, so we send the watchdog a keepalive ping */
688 
689 	err = -ENODEV;
690 	mutex_lock(&wd_data->lock);
691 	wdd = wd_data->wdd;
692 	if (wdd)
693 		err = watchdog_ping(wdd);
694 	mutex_unlock(&wd_data->lock);
695 
696 	if (err < 0)
697 		return err;
698 
699 	return len;
700 }
701 
702 /*
703  *	watchdog_ioctl: handle the different ioctl's for the watchdog device.
704  *	@file: file handle to the device
705  *	@cmd: watchdog command
706  *	@arg: argument pointer
707  *
708  *	The watchdog API defines a common set of functions for all watchdogs
709  *	according to their available features.
710  */
711 
watchdog_ioctl(struct file * file,unsigned int cmd,unsigned long arg)712 static long watchdog_ioctl(struct file *file, unsigned int cmd,
713 							unsigned long arg)
714 {
715 	struct watchdog_core_data *wd_data = file->private_data;
716 	void __user *argp = (void __user *)arg;
717 	struct watchdog_device *wdd;
718 	int __user *p = argp;
719 	unsigned int val;
720 	int err;
721 
722 	mutex_lock(&wd_data->lock);
723 
724 	wdd = wd_data->wdd;
725 	if (!wdd) {
726 		err = -ENODEV;
727 		goto out_ioctl;
728 	}
729 
730 	err = watchdog_ioctl_op(wdd, cmd, arg);
731 	if (err != -ENOIOCTLCMD)
732 		goto out_ioctl;
733 
734 	switch (cmd) {
735 	case WDIOC_GETSUPPORT:
736 		err = copy_to_user(argp, wdd->info,
737 			sizeof(struct watchdog_info)) ? -EFAULT : 0;
738 		break;
739 	case WDIOC_GETSTATUS:
740 		val = watchdog_get_status(wdd);
741 		err = put_user(val, p);
742 		break;
743 	case WDIOC_GETBOOTSTATUS:
744 		err = put_user(wdd->bootstatus, p);
745 		break;
746 	case WDIOC_SETOPTIONS:
747 		if (get_user(val, p)) {
748 			err = -EFAULT;
749 			break;
750 		}
751 		if (val & WDIOS_DISABLECARD) {
752 			err = watchdog_stop(wdd);
753 			if (err < 0)
754 				break;
755 		}
756 		if (val & WDIOS_ENABLECARD)
757 			err = watchdog_start(wdd);
758 		break;
759 	case WDIOC_KEEPALIVE:
760 		if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
761 			err = -EOPNOTSUPP;
762 			break;
763 		}
764 		err = watchdog_ping(wdd);
765 		break;
766 	case WDIOC_SETTIMEOUT:
767 		if (get_user(val, p)) {
768 			err = -EFAULT;
769 			break;
770 		}
771 		err = watchdog_set_timeout(wdd, val);
772 		if (err < 0)
773 			break;
774 		/* If the watchdog is active then we send a keepalive ping
775 		 * to make sure that the watchdog keep's running (and if
776 		 * possible that it takes the new timeout) */
777 		err = watchdog_ping(wdd);
778 		if (err < 0)
779 			break;
780 		fallthrough;
781 	case WDIOC_GETTIMEOUT:
782 		/* timeout == 0 means that we don't know the timeout */
783 		if (wdd->timeout == 0) {
784 			err = -EOPNOTSUPP;
785 			break;
786 		}
787 		err = put_user(wdd->timeout, p);
788 		break;
789 	case WDIOC_GETTIMELEFT:
790 		err = watchdog_get_timeleft(wdd, &val);
791 		if (err < 0)
792 			break;
793 		err = put_user(val, p);
794 		break;
795 	case WDIOC_SETPRETIMEOUT:
796 		if (get_user(val, p)) {
797 			err = -EFAULT;
798 			break;
799 		}
800 		err = watchdog_set_pretimeout(wdd, val);
801 		break;
802 	case WDIOC_GETPRETIMEOUT:
803 		err = put_user(wdd->pretimeout, p);
804 		break;
805 	default:
806 		err = -ENOTTY;
807 		break;
808 	}
809 
810 out_ioctl:
811 	mutex_unlock(&wd_data->lock);
812 	return err;
813 }
814 
815 /*
816  *	watchdog_open: open the /dev/watchdog* devices.
817  *	@inode: inode of device
818  *	@file: file handle to device
819  *
820  *	When the /dev/watchdog* device gets opened, we start the watchdog.
821  *	Watch out: the /dev/watchdog device is single open, so we make sure
822  *	it can only be opened once.
823  */
824 
watchdog_open(struct inode * inode,struct file * file)825 static int watchdog_open(struct inode *inode, struct file *file)
826 {
827 	struct watchdog_core_data *wd_data;
828 	struct watchdog_device *wdd;
829 	bool hw_running;
830 	int err;
831 
832 	/* Get the corresponding watchdog device */
833 	if (imajor(inode) == MISC_MAJOR)
834 		wd_data = old_wd_data;
835 	else
836 		wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
837 				       cdev);
838 
839 	/* the watchdog is single open! */
840 	if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
841 		return -EBUSY;
842 
843 	wdd = wd_data->wdd;
844 
845 	/*
846 	 * If the /dev/watchdog device is open, we don't want the module
847 	 * to be unloaded.
848 	 */
849 	hw_running = watchdog_hw_running(wdd);
850 	if (!hw_running && !try_module_get(wdd->ops->owner)) {
851 		err = -EBUSY;
852 		goto out_clear;
853 	}
854 
855 	err = watchdog_start(wdd);
856 	if (err < 0)
857 		goto out_mod;
858 
859 	file->private_data = wd_data;
860 
861 	if (!hw_running)
862 		get_device(&wd_data->dev);
863 
864 	/*
865 	 * open_timeout only applies for the first open from
866 	 * userspace. Set open_deadline to infinity so that the kernel
867 	 * will take care of an always-running hardware watchdog in
868 	 * case the device gets magic-closed or WDIOS_DISABLECARD is
869 	 * applied.
870 	 */
871 	wd_data->open_deadline = KTIME_MAX;
872 
873 	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
874 	return stream_open(inode, file);
875 
876 out_mod:
877 	module_put(wd_data->wdd->ops->owner);
878 out_clear:
879 	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
880 	return err;
881 }
882 
watchdog_core_data_release(struct device * dev)883 static void watchdog_core_data_release(struct device *dev)
884 {
885 	struct watchdog_core_data *wd_data;
886 
887 	wd_data = container_of(dev, struct watchdog_core_data, dev);
888 
889 	kfree(wd_data);
890 }
891 
892 /*
893  *	watchdog_release: release the watchdog device.
894  *	@inode: inode of device
895  *	@file: file handle to device
896  *
897  *	This is the code for when /dev/watchdog gets closed. We will only
898  *	stop the watchdog when we have received the magic char (and nowayout
899  *	was not set), else the watchdog will keep running.
900  */
901 
watchdog_release(struct inode * inode,struct file * file)902 static int watchdog_release(struct inode *inode, struct file *file)
903 {
904 	struct watchdog_core_data *wd_data = file->private_data;
905 	struct watchdog_device *wdd;
906 	int err = -EBUSY;
907 	bool running;
908 
909 	mutex_lock(&wd_data->lock);
910 
911 	wdd = wd_data->wdd;
912 	if (!wdd)
913 		goto done;
914 
915 	/*
916 	 * We only stop the watchdog if we received the magic character
917 	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
918 	 * watchdog_stop will fail.
919 	 */
920 	if (!watchdog_active(wdd))
921 		err = 0;
922 	else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
923 		 !(wdd->info->options & WDIOF_MAGICCLOSE))
924 		err = watchdog_stop(wdd);
925 
926 	/* If the watchdog was not stopped, send a keepalive ping */
927 	if (err < 0) {
928 		pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
929 		watchdog_ping(wdd);
930 	}
931 
932 	watchdog_update_worker(wdd);
933 
934 	/* make sure that /dev/watchdog can be re-opened */
935 	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
936 
937 done:
938 	running = wdd && watchdog_hw_running(wdd);
939 	mutex_unlock(&wd_data->lock);
940 	/*
941 	 * Allow the owner module to be unloaded again unless the watchdog
942 	 * is still running. If the watchdog is still running, it can not
943 	 * be stopped, and its driver must not be unloaded.
944 	 */
945 	if (!running) {
946 		module_put(wd_data->cdev.owner);
947 		put_device(&wd_data->dev);
948 	}
949 	return 0;
950 }
951 
952 static const struct file_operations watchdog_fops = {
953 	.owner		= THIS_MODULE,
954 	.write		= watchdog_write,
955 	.unlocked_ioctl	= watchdog_ioctl,
956 	.compat_ioctl	= compat_ptr_ioctl,
957 	.open		= watchdog_open,
958 	.release	= watchdog_release,
959 };
960 
961 static struct miscdevice watchdog_miscdev = {
962 	.minor		= WATCHDOG_MINOR,
963 	.name		= "watchdog",
964 	.fops		= &watchdog_fops,
965 };
966 
967 static struct class watchdog_class = {
968 	.name =		"watchdog",
969 	.owner =	THIS_MODULE,
970 	.dev_groups =	wdt_groups,
971 };
972 
973 /*
974  *	watchdog_cdev_register: register watchdog character device
975  *	@wdd: watchdog device
976  *
977  *	Register a watchdog character device including handling the legacy
978  *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
979  *	thus we set it up like that.
980  */
981 
watchdog_cdev_register(struct watchdog_device * wdd)982 static int watchdog_cdev_register(struct watchdog_device *wdd)
983 {
984 	struct watchdog_core_data *wd_data;
985 	int err;
986 
987 	wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
988 	if (!wd_data)
989 		return -ENOMEM;
990 	mutex_init(&wd_data->lock);
991 
992 	wd_data->wdd = wdd;
993 	wdd->wd_data = wd_data;
994 
995 	if (IS_ERR_OR_NULL(watchdog_kworker)) {
996 		kfree(wd_data);
997 		return -ENODEV;
998 	}
999 
1000 	device_initialize(&wd_data->dev);
1001 	wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
1002 	wd_data->dev.class = &watchdog_class;
1003 	wd_data->dev.parent = wdd->parent;
1004 	wd_data->dev.groups = wdd->groups;
1005 	wd_data->dev.release = watchdog_core_data_release;
1006 	dev_set_drvdata(&wd_data->dev, wdd);
1007 	dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
1008 
1009 	kthread_init_work(&wd_data->work, watchdog_ping_work);
1010 	hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1011 	wd_data->timer.function = watchdog_timer_expired;
1012 
1013 	if (wdd->id == 0) {
1014 		old_wd_data = wd_data;
1015 		watchdog_miscdev.parent = wdd->parent;
1016 		err = misc_register(&watchdog_miscdev);
1017 		if (err != 0) {
1018 			pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
1019 				wdd->info->identity, WATCHDOG_MINOR, err);
1020 			if (err == -EBUSY)
1021 				pr_err("%s: a legacy watchdog module is probably present.\n",
1022 					wdd->info->identity);
1023 			old_wd_data = NULL;
1024 			put_device(&wd_data->dev);
1025 			return err;
1026 		}
1027 	}
1028 
1029 	/* Fill in the data structures */
1030 	cdev_init(&wd_data->cdev, &watchdog_fops);
1031 
1032 	/* Add the device */
1033 	err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1034 	if (err) {
1035 		pr_err("watchdog%d unable to add device %d:%d\n",
1036 			wdd->id,  MAJOR(watchdog_devt), wdd->id);
1037 		if (wdd->id == 0) {
1038 			misc_deregister(&watchdog_miscdev);
1039 			old_wd_data = NULL;
1040 			put_device(&wd_data->dev);
1041 		}
1042 		return err;
1043 	}
1044 
1045 	wd_data->cdev.owner = wdd->ops->owner;
1046 
1047 	/* Record time of most recent heartbeat as 'just before now'. */
1048 	wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1049 	watchdog_set_open_deadline(wd_data);
1050 
1051 	/*
1052 	 * If the watchdog is running, prevent its driver from being unloaded,
1053 	 * and schedule an immediate ping.
1054 	 */
1055 	if (watchdog_hw_running(wdd)) {
1056 		__module_get(wdd->ops->owner);
1057 		get_device(&wd_data->dev);
1058 		if (handle_boot_enabled)
1059 			hrtimer_start(&wd_data->timer, 0,
1060 				      HRTIMER_MODE_REL_HARD);
1061 		else
1062 			pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1063 				wdd->id);
1064 	}
1065 
1066 	return 0;
1067 }
1068 
1069 /*
1070  *	watchdog_cdev_unregister: unregister watchdog character device
1071  *	@watchdog: watchdog device
1072  *
1073  *	Unregister watchdog character device and if needed the legacy
1074  *	/dev/watchdog device.
1075  */
1076 
watchdog_cdev_unregister(struct watchdog_device * wdd)1077 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1078 {
1079 	struct watchdog_core_data *wd_data = wdd->wd_data;
1080 
1081 	cdev_device_del(&wd_data->cdev, &wd_data->dev);
1082 	if (wdd->id == 0) {
1083 		misc_deregister(&watchdog_miscdev);
1084 		old_wd_data = NULL;
1085 	}
1086 
1087 	if (watchdog_active(wdd) &&
1088 	    test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1089 		watchdog_stop(wdd);
1090 	}
1091 
1092 	mutex_lock(&wd_data->lock);
1093 	wd_data->wdd = NULL;
1094 	wdd->wd_data = NULL;
1095 	mutex_unlock(&wd_data->lock);
1096 
1097 	hrtimer_cancel(&wd_data->timer);
1098 	kthread_cancel_work_sync(&wd_data->work);
1099 
1100 	put_device(&wd_data->dev);
1101 }
1102 
1103 /*
1104  *	watchdog_dev_register: register a watchdog device
1105  *	@wdd: watchdog device
1106  *
1107  *	Register a watchdog device including handling the legacy
1108  *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
1109  *	thus we set it up like that.
1110  */
1111 
watchdog_dev_register(struct watchdog_device * wdd)1112 int watchdog_dev_register(struct watchdog_device *wdd)
1113 {
1114 	int ret;
1115 
1116 	ret = watchdog_cdev_register(wdd);
1117 	if (ret)
1118 		return ret;
1119 
1120 	ret = watchdog_register_pretimeout(wdd);
1121 	if (ret)
1122 		watchdog_cdev_unregister(wdd);
1123 
1124 	return ret;
1125 }
1126 
1127 /*
1128  *	watchdog_dev_unregister: unregister a watchdog device
1129  *	@watchdog: watchdog device
1130  *
1131  *	Unregister watchdog device and if needed the legacy
1132  *	/dev/watchdog device.
1133  */
1134 
watchdog_dev_unregister(struct watchdog_device * wdd)1135 void watchdog_dev_unregister(struct watchdog_device *wdd)
1136 {
1137 	watchdog_unregister_pretimeout(wdd);
1138 	watchdog_cdev_unregister(wdd);
1139 }
1140 
1141 /*
1142  *	watchdog_set_last_hw_keepalive: set last HW keepalive time for watchdog
1143  *	@wdd: watchdog device
1144  *	@last_ping_ms: time since last HW heartbeat
1145  *
1146  *	Adjusts the last known HW keepalive time for a watchdog timer.
1147  *	This is needed if the watchdog is already running when the probe
1148  *	function is called, and it can't be pinged immediately. This
1149  *	function must be called immediately after watchdog registration,
1150  *	and min_hw_heartbeat_ms must be set for this to be useful.
1151  */
watchdog_set_last_hw_keepalive(struct watchdog_device * wdd,unsigned int last_ping_ms)1152 int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
1153 				   unsigned int last_ping_ms)
1154 {
1155 	struct watchdog_core_data *wd_data;
1156 	ktime_t now;
1157 
1158 	if (!wdd)
1159 		return -EINVAL;
1160 
1161 	wd_data = wdd->wd_data;
1162 
1163 	now = ktime_get();
1164 
1165 	wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));
1166 
1167 	if (watchdog_hw_running(wdd) && handle_boot_enabled)
1168 		return __watchdog_ping(wdd);
1169 
1170 	return 0;
1171 }
1172 EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);
1173 
1174 /*
1175  *	watchdog_dev_init: init dev part of watchdog core
1176  *
1177  *	Allocate a range of chardev nodes to use for watchdog devices
1178  */
1179 
watchdog_dev_init(void)1180 int __init watchdog_dev_init(void)
1181 {
1182 	int err;
1183 
1184 	watchdog_kworker = kthread_create_worker(0, "watchdogd");
1185 	if (IS_ERR(watchdog_kworker)) {
1186 		pr_err("Failed to create watchdog kworker\n");
1187 		return PTR_ERR(watchdog_kworker);
1188 	}
1189 	sched_set_fifo(watchdog_kworker->task);
1190 
1191 	err = class_register(&watchdog_class);
1192 	if (err < 0) {
1193 		pr_err("couldn't register class\n");
1194 		goto err_register;
1195 	}
1196 
1197 	err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1198 	if (err < 0) {
1199 		pr_err("watchdog: unable to allocate char dev region\n");
1200 		goto err_alloc;
1201 	}
1202 
1203 	return 0;
1204 
1205 err_alloc:
1206 	class_unregister(&watchdog_class);
1207 err_register:
1208 	kthread_destroy_worker(watchdog_kworker);
1209 	return err;
1210 }
1211 
1212 /*
1213  *	watchdog_dev_exit: exit dev part of watchdog core
1214  *
1215  *	Release the range of chardev nodes used for watchdog devices
1216  */
1217 
watchdog_dev_exit(void)1218 void __exit watchdog_dev_exit(void)
1219 {
1220 	unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1221 	class_unregister(&watchdog_class);
1222 	kthread_destroy_worker(watchdog_kworker);
1223 }
1224 
1225 module_param(handle_boot_enabled, bool, 0444);
1226 MODULE_PARM_DESC(handle_boot_enabled,
1227 	"Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1228 	__MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1229 
1230 module_param(open_timeout, uint, 0644);
1231 MODULE_PARM_DESC(open_timeout,
1232 	"Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1233 	__MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");
1234