Merge remote-tracking branch 'stable/linux-5.15.y' into rpi-5.15.y
[platform/kernel/linux-rpi.git] / drivers / watchdog / watchdog_dev.c
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  *      (c) Copyright 2021 Hewlett Packard Enterprise Development LP.
11  *
12  *      This source code is part of the generic code that can be used
13  *      by all the watchdog timer drivers.
14  *
15  *      This part of the generic code takes care of the following
16  *      misc device: /dev/watchdog.
17  *
18  *      Based on source code of the following authors:
19  *        Matt Domsch <Matt_Domsch@dell.com>,
20  *        Rob Radez <rob@osinvestor.com>,
21  *        Rusty Lynch <rusty@linux.co.intel.com>
22  *        Satyam Sharma <satyam@infradead.org>
23  *        Randy Dunlap <randy.dunlap@oracle.com>
24  *
25  *      Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
26  *      admit liability nor provide warranty for any of this software.
27  *      This material is provided "AS-IS" and at no charge.
28  */
29
30 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
31
32 #include <linux/cdev.h>         /* For character device */
33 #include <linux/errno.h>        /* For the -ENODEV/... values */
34 #include <linux/fs.h>           /* For file operations */
35 #include <linux/init.h>         /* For __init/__exit/... */
36 #include <linux/hrtimer.h>      /* For hrtimers */
37 #include <linux/kernel.h>       /* For printk/panic/... */
38 #include <linux/kthread.h>      /* For kthread_work */
39 #include <linux/miscdevice.h>   /* For handling misc devices */
40 #include <linux/module.h>       /* For module stuff/... */
41 #include <linux/mutex.h>        /* For mutexes */
42 #include <linux/slab.h>         /* For memory functions */
43 #include <linux/types.h>        /* For standard types (like size_t) */
44 #include <linux/watchdog.h>     /* For watchdog specific items */
45 #include <linux/uaccess.h>      /* For copy_to_user/put_user/... */
46
47 #include "watchdog_core.h"
48 #include "watchdog_pretimeout.h"
49
50 /* the dev_t structure to store the dynamically allocated watchdog devices */
51 static dev_t watchdog_devt;
52 /* Reference to watchdog device behind /dev/watchdog */
53 static struct watchdog_core_data *old_wd_data;
54
55 static struct kthread_worker *watchdog_kworker;
56
57 static bool handle_boot_enabled =
58         IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
59
60 static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
61
62 static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
63 {
64         return ktime_after(ktime_get(), data->open_deadline);
65 }
66
67 static void watchdog_set_open_deadline(struct watchdog_core_data *data)
68 {
69         data->open_deadline = open_timeout ?
70                 ktime_get() + ktime_set(open_timeout, 0) : KTIME_MAX;
71 }
72
73 static inline bool watchdog_need_worker(struct watchdog_device *wdd)
74 {
75         /* All variables in milli-seconds */
76         unsigned int hm = wdd->max_hw_heartbeat_ms;
77         unsigned int t = wdd->timeout * 1000;
78
79         /*
80          * A worker to generate heartbeat requests is needed if all of the
81          * following conditions are true.
82          * - Userspace activated the watchdog.
83          * - The driver provided a value for the maximum hardware timeout, and
84          *   thus is aware that the framework supports generating heartbeat
85          *   requests.
86          * - Userspace requests a longer timeout than the hardware can handle.
87          *
88          * Alternatively, if userspace has not opened the watchdog
89          * device, we take care of feeding the watchdog if it is
90          * running.
91          */
92         return (hm && watchdog_active(wdd) && t > hm) ||
93                 (t && !watchdog_active(wdd) && watchdog_hw_running(wdd));
94 }
95
96 static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
97 {
98         struct watchdog_core_data *wd_data = wdd->wd_data;
99         unsigned int timeout_ms = wdd->timeout * 1000;
100         ktime_t keepalive_interval;
101         ktime_t last_heartbeat, latest_heartbeat;
102         ktime_t virt_timeout;
103         unsigned int hw_heartbeat_ms;
104
105         if (watchdog_active(wdd))
106                 virt_timeout = ktime_add(wd_data->last_keepalive,
107                                          ms_to_ktime(timeout_ms));
108         else
109                 virt_timeout = wd_data->open_deadline;
110
111         hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms);
112         keepalive_interval = ms_to_ktime(hw_heartbeat_ms / 2);
113
114         /*
115          * To ensure that the watchdog times out wdd->timeout seconds
116          * after the most recent ping from userspace, the last
117          * worker ping has to come in hw_heartbeat_ms before this timeout.
118          */
119         last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms));
120         latest_heartbeat = ktime_sub(last_heartbeat, ktime_get());
121         if (ktime_before(latest_heartbeat, keepalive_interval))
122                 return latest_heartbeat;
123         return keepalive_interval;
124 }
125
126 static inline void watchdog_update_worker(struct watchdog_device *wdd)
127 {
128         struct watchdog_core_data *wd_data = wdd->wd_data;
129
130         if (watchdog_need_worker(wdd)) {
131                 ktime_t t = watchdog_next_keepalive(wdd);
132
133                 if (t > 0)
134                         hrtimer_start(&wd_data->timer, t,
135                                       HRTIMER_MODE_REL_HARD);
136         } else {
137                 hrtimer_cancel(&wd_data->timer);
138         }
139 }
140
141 static int __watchdog_ping(struct watchdog_device *wdd)
142 {
143         struct watchdog_core_data *wd_data = wdd->wd_data;
144         ktime_t earliest_keepalive, now;
145         int err;
146
147         earliest_keepalive = ktime_add(wd_data->last_hw_keepalive,
148                                        ms_to_ktime(wdd->min_hw_heartbeat_ms));
149         now = ktime_get();
150
151         if (ktime_after(earliest_keepalive, now)) {
152                 hrtimer_start(&wd_data->timer,
153                               ktime_sub(earliest_keepalive, now),
154                               HRTIMER_MODE_REL_HARD);
155                 return 0;
156         }
157
158         wd_data->last_hw_keepalive = now;
159
160         if (wdd->ops->ping)
161                 err = wdd->ops->ping(wdd);  /* ping the watchdog */
162         else
163                 err = wdd->ops->start(wdd); /* restart watchdog */
164
165         if (err == 0)
166                 watchdog_hrtimer_pretimeout_start(wdd);
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 = ktime_get();
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         if (!wdd)
203                 return false;
204
205         if (watchdog_active(wdd))
206                 return true;
207
208         return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data);
209 }
210
211 static void watchdog_ping_work(struct kthread_work *work)
212 {
213         struct watchdog_core_data *wd_data;
214
215         wd_data = container_of(work, struct watchdog_core_data, work);
216
217         mutex_lock(&wd_data->lock);
218         if (watchdog_worker_should_ping(wd_data))
219                 __watchdog_ping(wd_data->wdd);
220         mutex_unlock(&wd_data->lock);
221 }
222
223 static enum hrtimer_restart watchdog_timer_expired(struct hrtimer *timer)
224 {
225         struct watchdog_core_data *wd_data;
226
227         wd_data = container_of(timer, struct watchdog_core_data, timer);
228
229         kthread_queue_work(watchdog_kworker, &wd_data->work);
230         return HRTIMER_NORESTART;
231 }
232
233 /*
234  *      watchdog_start: wrapper to start the watchdog.
235  *      @wdd: the watchdog device to start
236  *
237  *      The caller must hold wd_data->lock.
238  *
239  *      Start the watchdog if it is not active and mark it active.
240  *      This function returns zero on success or a negative errno code for
241  *      failure.
242  */
243
244 static int watchdog_start(struct watchdog_device *wdd)
245 {
246         struct watchdog_core_data *wd_data = wdd->wd_data;
247         ktime_t started_at;
248         int err;
249
250         if (watchdog_active(wdd))
251                 return 0;
252
253         set_bit(_WDOG_KEEPALIVE, &wd_data->status);
254
255         started_at = ktime_get();
256         if (watchdog_hw_running(wdd) && wdd->ops->ping) {
257                 err = __watchdog_ping(wdd);
258                 if (err == 0) {
259                         set_bit(WDOG_ACTIVE, &wdd->status);
260                         watchdog_hrtimer_pretimeout_start(wdd);
261                 }
262         } else {
263                 err = wdd->ops->start(wdd);
264                 if (err == 0) {
265                         set_bit(WDOG_ACTIVE, &wdd->status);
266                         wd_data->last_keepalive = started_at;
267                         wd_data->last_hw_keepalive = started_at;
268                         watchdog_update_worker(wdd);
269                         watchdog_hrtimer_pretimeout_start(wdd);
270                 }
271         }
272
273         return err;
274 }
275
276 /*
277  *      watchdog_stop: wrapper to stop the watchdog.
278  *      @wdd: the watchdog device to stop
279  *
280  *      The caller must hold wd_data->lock.
281  *
282  *      Stop the watchdog if it is still active and unmark it active.
283  *      This function returns zero on success or a negative errno code for
284  *      failure.
285  *      If the 'nowayout' feature was set, the watchdog cannot be stopped.
286  */
287
288 static int watchdog_stop(struct watchdog_device *wdd)
289 {
290         int err = 0;
291
292         if (!watchdog_active(wdd))
293                 return 0;
294
295         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
296                 pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
297                         wdd->id);
298                 return -EBUSY;
299         }
300
301         if (wdd->ops->stop) {
302                 clear_bit(WDOG_HW_RUNNING, &wdd->status);
303                 err = wdd->ops->stop(wdd);
304         } else {
305                 set_bit(WDOG_HW_RUNNING, &wdd->status);
306         }
307
308         if (err == 0) {
309                 clear_bit(WDOG_ACTIVE, &wdd->status);
310                 watchdog_update_worker(wdd);
311                 watchdog_hrtimer_pretimeout_stop(wdd);
312         }
313
314         return err;
315 }
316
317 /*
318  *      watchdog_get_status: wrapper to get the watchdog status
319  *      @wdd: the watchdog device to get the status from
320  *
321  *      The caller must hold wd_data->lock.
322  *
323  *      Get the watchdog's status flags.
324  */
325
326 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
327 {
328         struct watchdog_core_data *wd_data = wdd->wd_data;
329         unsigned int status;
330
331         if (wdd->ops->status)
332                 status = wdd->ops->status(wdd);
333         else
334                 status = wdd->bootstatus & (WDIOF_CARDRESET |
335                                             WDIOF_OVERHEAT |
336                                             WDIOF_FANFAULT |
337                                             WDIOF_EXTERN1 |
338                                             WDIOF_EXTERN2 |
339                                             WDIOF_POWERUNDER |
340                                             WDIOF_POWEROVER);
341
342         if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
343                 status |= WDIOF_MAGICCLOSE;
344
345         if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
346                 status |= WDIOF_KEEPALIVEPING;
347
348         if (IS_ENABLED(CONFIG_WATCHDOG_HRTIMER_PRETIMEOUT))
349                 status |= WDIOF_PRETIMEOUT;
350
351         return status;
352 }
353
354 /*
355  *      watchdog_set_timeout: set the watchdog timer timeout
356  *      @wdd: the watchdog device to set the timeout for
357  *      @timeout: timeout to set in seconds
358  *
359  *      The caller must hold wd_data->lock.
360  */
361
362 static int watchdog_set_timeout(struct watchdog_device *wdd,
363                                                         unsigned int timeout)
364 {
365         int err = 0;
366
367         if (!(wdd->info->options & WDIOF_SETTIMEOUT))
368                 return -EOPNOTSUPP;
369
370         if (watchdog_timeout_invalid(wdd, timeout))
371                 return -EINVAL;
372
373         if (wdd->ops->set_timeout) {
374                 err = wdd->ops->set_timeout(wdd, timeout);
375         } else {
376                 wdd->timeout = timeout;
377                 /* Disable pretimeout if it doesn't fit the new timeout */
378                 if (wdd->pretimeout >= wdd->timeout)
379                         wdd->pretimeout = 0;
380         }
381
382         watchdog_update_worker(wdd);
383
384         return err;
385 }
386
387 /*
388  *      watchdog_set_pretimeout: set the watchdog timer pretimeout
389  *      @wdd: the watchdog device to set the timeout for
390  *      @timeout: pretimeout to set in seconds
391  */
392
393 static int watchdog_set_pretimeout(struct watchdog_device *wdd,
394                                    unsigned int timeout)
395 {
396         int err = 0;
397
398         if (!watchdog_have_pretimeout(wdd))
399                 return -EOPNOTSUPP;
400
401         if (watchdog_pretimeout_invalid(wdd, timeout))
402                 return -EINVAL;
403
404         if (wdd->ops->set_pretimeout && (wdd->info->options & WDIOF_PRETIMEOUT))
405                 err = wdd->ops->set_pretimeout(wdd, timeout);
406         else
407                 wdd->pretimeout = timeout;
408
409         return err;
410 }
411
412 /*
413  *      watchdog_get_timeleft: wrapper to get the time left before a reboot
414  *      @wdd: the watchdog device to get the remaining time from
415  *      @timeleft: the time that's left
416  *
417  *      The caller must hold wd_data->lock.
418  *
419  *      Get the time before a watchdog will reboot (if not pinged).
420  */
421
422 static int watchdog_get_timeleft(struct watchdog_device *wdd,
423                                                         unsigned int *timeleft)
424 {
425         *timeleft = 0;
426
427         if (!wdd->ops->get_timeleft)
428                 return -EOPNOTSUPP;
429
430         *timeleft = wdd->ops->get_timeleft(wdd);
431
432         return 0;
433 }
434
435 #ifdef CONFIG_WATCHDOG_SYSFS
436 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
437                                 char *buf)
438 {
439         struct watchdog_device *wdd = dev_get_drvdata(dev);
440
441         return sysfs_emit(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT,
442                                                   &wdd->status));
443 }
444
445 static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,
446                                 const char *buf, size_t len)
447 {
448         struct watchdog_device *wdd = dev_get_drvdata(dev);
449         unsigned int value;
450         int ret;
451
452         ret = kstrtouint(buf, 0, &value);
453         if (ret)
454                 return ret;
455         if (value > 1)
456                 return -EINVAL;
457         /* nowayout cannot be disabled once set */
458         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)
459                 return -EPERM;
460         watchdog_set_nowayout(wdd, value);
461         return len;
462 }
463 static DEVICE_ATTR_RW(nowayout);
464
465 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
466                                 char *buf)
467 {
468         struct watchdog_device *wdd = dev_get_drvdata(dev);
469         struct watchdog_core_data *wd_data = wdd->wd_data;
470         unsigned int status;
471
472         mutex_lock(&wd_data->lock);
473         status = watchdog_get_status(wdd);
474         mutex_unlock(&wd_data->lock);
475
476         return sysfs_emit(buf, "0x%x\n", status);
477 }
478 static DEVICE_ATTR_RO(status);
479
480 static ssize_t bootstatus_show(struct device *dev,
481                                 struct device_attribute *attr, char *buf)
482 {
483         struct watchdog_device *wdd = dev_get_drvdata(dev);
484
485         return sysfs_emit(buf, "%u\n", wdd->bootstatus);
486 }
487 static DEVICE_ATTR_RO(bootstatus);
488
489 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
490                                 char *buf)
491 {
492         struct watchdog_device *wdd = dev_get_drvdata(dev);
493         struct watchdog_core_data *wd_data = wdd->wd_data;
494         ssize_t status;
495         unsigned int val;
496
497         mutex_lock(&wd_data->lock);
498         status = watchdog_get_timeleft(wdd, &val);
499         mutex_unlock(&wd_data->lock);
500         if (!status)
501                 status = sysfs_emit(buf, "%u\n", val);
502
503         return status;
504 }
505 static DEVICE_ATTR_RO(timeleft);
506
507 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
508                                 char *buf)
509 {
510         struct watchdog_device *wdd = dev_get_drvdata(dev);
511
512         return sysfs_emit(buf, "%u\n", wdd->timeout);
513 }
514 static DEVICE_ATTR_RO(timeout);
515
516 static ssize_t min_timeout_show(struct device *dev,
517                                 struct device_attribute *attr, char *buf)
518 {
519         struct watchdog_device *wdd = dev_get_drvdata(dev);
520
521         return sysfs_emit(buf, "%u\n", wdd->min_timeout);
522 }
523 static DEVICE_ATTR_RO(min_timeout);
524
525 static ssize_t max_timeout_show(struct device *dev,
526                                 struct device_attribute *attr, char *buf)
527 {
528         struct watchdog_device *wdd = dev_get_drvdata(dev);
529
530         return sysfs_emit(buf, "%u\n", wdd->max_timeout);
531 }
532 static DEVICE_ATTR_RO(max_timeout);
533
534 static ssize_t pretimeout_show(struct device *dev,
535                                struct device_attribute *attr, char *buf)
536 {
537         struct watchdog_device *wdd = dev_get_drvdata(dev);
538
539         return sysfs_emit(buf, "%u\n", wdd->pretimeout);
540 }
541 static DEVICE_ATTR_RO(pretimeout);
542
543 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
544                                 char *buf)
545 {
546         struct watchdog_device *wdd = dev_get_drvdata(dev);
547
548         return sysfs_emit(buf, "%s\n", wdd->info->identity);
549 }
550 static DEVICE_ATTR_RO(identity);
551
552 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
553                                 char *buf)
554 {
555         struct watchdog_device *wdd = dev_get_drvdata(dev);
556
557         if (watchdog_active(wdd))
558                 return sysfs_emit(buf, "active\n");
559
560         return sysfs_emit(buf, "inactive\n");
561 }
562 static DEVICE_ATTR_RO(state);
563
564 static ssize_t pretimeout_available_governors_show(struct device *dev,
565                                    struct device_attribute *attr, char *buf)
566 {
567         return watchdog_pretimeout_available_governors_get(buf);
568 }
569 static DEVICE_ATTR_RO(pretimeout_available_governors);
570
571 static ssize_t pretimeout_governor_show(struct device *dev,
572                                         struct device_attribute *attr,
573                                         char *buf)
574 {
575         struct watchdog_device *wdd = dev_get_drvdata(dev);
576
577         return watchdog_pretimeout_governor_get(wdd, buf);
578 }
579
580 static ssize_t pretimeout_governor_store(struct device *dev,
581                                          struct device_attribute *attr,
582                                          const char *buf, size_t count)
583 {
584         struct watchdog_device *wdd = dev_get_drvdata(dev);
585         int ret = watchdog_pretimeout_governor_set(wdd, buf);
586
587         if (!ret)
588                 ret = count;
589
590         return ret;
591 }
592 static DEVICE_ATTR_RW(pretimeout_governor);
593
594 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
595                                 int n)
596 {
597         struct device *dev = kobj_to_dev(kobj);
598         struct watchdog_device *wdd = dev_get_drvdata(dev);
599         umode_t mode = attr->mode;
600
601         if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
602                 mode = 0;
603         else if (attr == &dev_attr_pretimeout.attr && !watchdog_have_pretimeout(wdd))
604                 mode = 0;
605         else if ((attr == &dev_attr_pretimeout_governor.attr ||
606                   attr == &dev_attr_pretimeout_available_governors.attr) &&
607                  (!watchdog_have_pretimeout(wdd) || !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
608                 mode = 0;
609
610         return mode;
611 }
612 static struct attribute *wdt_attrs[] = {
613         &dev_attr_state.attr,
614         &dev_attr_identity.attr,
615         &dev_attr_timeout.attr,
616         &dev_attr_min_timeout.attr,
617         &dev_attr_max_timeout.attr,
618         &dev_attr_pretimeout.attr,
619         &dev_attr_timeleft.attr,
620         &dev_attr_bootstatus.attr,
621         &dev_attr_status.attr,
622         &dev_attr_nowayout.attr,
623         &dev_attr_pretimeout_governor.attr,
624         &dev_attr_pretimeout_available_governors.attr,
625         NULL,
626 };
627
628 static const struct attribute_group wdt_group = {
629         .attrs = wdt_attrs,
630         .is_visible = wdt_is_visible,
631 };
632 __ATTRIBUTE_GROUPS(wdt);
633 #else
634 #define wdt_groups      NULL
635 #endif
636
637 /*
638  *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
639  *      @wdd: the watchdog device to do the ioctl on
640  *      @cmd: watchdog command
641  *      @arg: argument pointer
642  *
643  *      The caller must hold wd_data->lock.
644  */
645
646 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
647                                                         unsigned long arg)
648 {
649         if (!wdd->ops->ioctl)
650                 return -ENOIOCTLCMD;
651
652         return wdd->ops->ioctl(wdd, cmd, arg);
653 }
654
655 /*
656  *      watchdog_write: writes to the watchdog.
657  *      @file: file from VFS
658  *      @data: user address of data
659  *      @len: length of data
660  *      @ppos: pointer to the file offset
661  *
662  *      A write to a watchdog device is defined as a keepalive ping.
663  *      Writing the magic 'V' sequence allows the next close to turn
664  *      off the watchdog (if 'nowayout' is not set).
665  */
666
667 static ssize_t watchdog_write(struct file *file, const char __user *data,
668                                                 size_t len, loff_t *ppos)
669 {
670         struct watchdog_core_data *wd_data = file->private_data;
671         struct watchdog_device *wdd;
672         int err;
673         size_t i;
674         char c;
675
676         if (len == 0)
677                 return 0;
678
679         /*
680          * Note: just in case someone wrote the magic character
681          * five months ago...
682          */
683         clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
684
685         /* scan to see whether or not we got the magic character */
686         for (i = 0; i != len; i++) {
687                 if (get_user(c, data + i))
688                         return -EFAULT;
689                 if (c == 'V')
690                         set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
691         }
692
693         /* someone wrote to us, so we send the watchdog a keepalive ping */
694
695         err = -ENODEV;
696         mutex_lock(&wd_data->lock);
697         wdd = wd_data->wdd;
698         if (wdd)
699                 err = watchdog_ping(wdd);
700         mutex_unlock(&wd_data->lock);
701
702         if (err < 0)
703                 return err;
704
705         return len;
706 }
707
708 /*
709  *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
710  *      @file: file handle to the device
711  *      @cmd: watchdog command
712  *      @arg: argument pointer
713  *
714  *      The watchdog API defines a common set of functions for all watchdogs
715  *      according to their available features.
716  */
717
718 static long watchdog_ioctl(struct file *file, unsigned int cmd,
719                                                         unsigned long arg)
720 {
721         struct watchdog_core_data *wd_data = file->private_data;
722         void __user *argp = (void __user *)arg;
723         struct watchdog_device *wdd;
724         int __user *p = argp;
725         unsigned int val;
726         int err;
727
728         mutex_lock(&wd_data->lock);
729
730         wdd = wd_data->wdd;
731         if (!wdd) {
732                 err = -ENODEV;
733                 goto out_ioctl;
734         }
735
736         err = watchdog_ioctl_op(wdd, cmd, arg);
737         if (err != -ENOIOCTLCMD)
738                 goto out_ioctl;
739
740         switch (cmd) {
741         case WDIOC_GETSUPPORT:
742                 err = copy_to_user(argp, wdd->info,
743                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
744                 break;
745         case WDIOC_GETSTATUS:
746                 val = watchdog_get_status(wdd);
747                 err = put_user(val, p);
748                 break;
749         case WDIOC_GETBOOTSTATUS:
750                 err = put_user(wdd->bootstatus, p);
751                 break;
752         case WDIOC_SETOPTIONS:
753                 if (get_user(val, p)) {
754                         err = -EFAULT;
755                         break;
756                 }
757                 if (val & WDIOS_DISABLECARD) {
758                         err = watchdog_stop(wdd);
759                         if (err < 0)
760                                 break;
761                 }
762                 if (val & WDIOS_ENABLECARD)
763                         err = watchdog_start(wdd);
764                 break;
765         case WDIOC_KEEPALIVE:
766                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
767                         err = -EOPNOTSUPP;
768                         break;
769                 }
770                 err = watchdog_ping(wdd);
771                 break;
772         case WDIOC_SETTIMEOUT:
773                 if (get_user(val, p)) {
774                         err = -EFAULT;
775                         break;
776                 }
777                 err = watchdog_set_timeout(wdd, val);
778                 if (err < 0)
779                         break;
780                 /* If the watchdog is active then we send a keepalive ping
781                  * to make sure that the watchdog keep's running (and if
782                  * possible that it takes the new timeout) */
783                 err = watchdog_ping(wdd);
784                 if (err < 0)
785                         break;
786                 fallthrough;
787         case WDIOC_GETTIMEOUT:
788                 /* timeout == 0 means that we don't know the timeout */
789                 if (wdd->timeout == 0) {
790                         err = -EOPNOTSUPP;
791                         break;
792                 }
793                 err = put_user(wdd->timeout, p);
794                 break;
795         case WDIOC_GETTIMELEFT:
796                 err = watchdog_get_timeleft(wdd, &val);
797                 if (err < 0)
798                         break;
799                 err = put_user(val, p);
800                 break;
801         case WDIOC_SETPRETIMEOUT:
802                 if (get_user(val, p)) {
803                         err = -EFAULT;
804                         break;
805                 }
806                 err = watchdog_set_pretimeout(wdd, val);
807                 break;
808         case WDIOC_GETPRETIMEOUT:
809                 err = put_user(wdd->pretimeout, p);
810                 break;
811         default:
812                 err = -ENOTTY;
813                 break;
814         }
815
816 out_ioctl:
817         mutex_unlock(&wd_data->lock);
818         return err;
819 }
820
821 /*
822  *      watchdog_open: open the /dev/watchdog* devices.
823  *      @inode: inode of device
824  *      @file: file handle to device
825  *
826  *      When the /dev/watchdog* device gets opened, we start the watchdog.
827  *      Watch out: the /dev/watchdog device is single open, so we make sure
828  *      it can only be opened once.
829  */
830
831 static int watchdog_open(struct inode *inode, struct file *file)
832 {
833         struct watchdog_core_data *wd_data;
834         struct watchdog_device *wdd;
835         bool hw_running;
836         int err;
837
838         /* Get the corresponding watchdog device */
839         if (imajor(inode) == MISC_MAJOR)
840                 wd_data = old_wd_data;
841         else
842                 wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
843                                        cdev);
844
845         /* the watchdog is single open! */
846         if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
847                 return -EBUSY;
848
849         wdd = wd_data->wdd;
850
851         /*
852          * If the /dev/watchdog device is open, we don't want the module
853          * to be unloaded.
854          */
855         hw_running = watchdog_hw_running(wdd);
856         if (!hw_running && !try_module_get(wdd->ops->owner)) {
857                 err = -EBUSY;
858                 goto out_clear;
859         }
860
861         err = watchdog_start(wdd);
862         if (err < 0)
863                 goto out_mod;
864
865         file->private_data = wd_data;
866
867         if (!hw_running)
868                 get_device(&wd_data->dev);
869
870         /*
871          * open_timeout only applies for the first open from
872          * userspace. Set open_deadline to infinity so that the kernel
873          * will take care of an always-running hardware watchdog in
874          * case the device gets magic-closed or WDIOS_DISABLECARD is
875          * applied.
876          */
877         wd_data->open_deadline = KTIME_MAX;
878
879         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
880         return stream_open(inode, file);
881
882 out_mod:
883         module_put(wd_data->wdd->ops->owner);
884 out_clear:
885         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
886         return err;
887 }
888
889 static void watchdog_core_data_release(struct device *dev)
890 {
891         struct watchdog_core_data *wd_data;
892
893         wd_data = container_of(dev, struct watchdog_core_data, dev);
894
895         kfree(wd_data);
896 }
897
898 /*
899  *      watchdog_release: release the watchdog device.
900  *      @inode: inode of device
901  *      @file: file handle to device
902  *
903  *      This is the code for when /dev/watchdog gets closed. We will only
904  *      stop the watchdog when we have received the magic char (and nowayout
905  *      was not set), else the watchdog will keep running.
906  */
907
908 static int watchdog_release(struct inode *inode, struct file *file)
909 {
910         struct watchdog_core_data *wd_data = file->private_data;
911         struct watchdog_device *wdd;
912         int err = -EBUSY;
913         bool running;
914
915         mutex_lock(&wd_data->lock);
916
917         wdd = wd_data->wdd;
918         if (!wdd)
919                 goto done;
920
921         /*
922          * We only stop the watchdog if we received the magic character
923          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
924          * watchdog_stop will fail.
925          */
926         if (!watchdog_active(wdd))
927                 err = 0;
928         else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
929                  !(wdd->info->options & WDIOF_MAGICCLOSE))
930                 err = watchdog_stop(wdd);
931
932         /* If the watchdog was not stopped, send a keepalive ping */
933         if (err < 0) {
934                 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
935                 watchdog_ping(wdd);
936         }
937
938         watchdog_update_worker(wdd);
939
940         /* make sure that /dev/watchdog can be re-opened */
941         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
942
943 done:
944         running = wdd && watchdog_hw_running(wdd);
945         mutex_unlock(&wd_data->lock);
946         /*
947          * Allow the owner module to be unloaded again unless the watchdog
948          * is still running. If the watchdog is still running, it can not
949          * be stopped, and its driver must not be unloaded.
950          */
951         if (!running) {
952                 module_put(wd_data->cdev.owner);
953                 put_device(&wd_data->dev);
954         }
955         return 0;
956 }
957
958 static const struct file_operations watchdog_fops = {
959         .owner          = THIS_MODULE,
960         .write          = watchdog_write,
961         .unlocked_ioctl = watchdog_ioctl,
962         .compat_ioctl   = compat_ptr_ioctl,
963         .open           = watchdog_open,
964         .release        = watchdog_release,
965 };
966
967 static struct miscdevice watchdog_miscdev = {
968         .minor          = WATCHDOG_MINOR,
969         .name           = "watchdog",
970         .fops           = &watchdog_fops,
971 };
972
973 static struct class watchdog_class = {
974         .name =         "watchdog",
975         .owner =        THIS_MODULE,
976         .dev_groups =   wdt_groups,
977 };
978
979 /*
980  *      watchdog_cdev_register: register watchdog character device
981  *      @wdd: watchdog device
982  *
983  *      Register a watchdog character device including handling the legacy
984  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
985  *      thus we set it up like that.
986  */
987
988 static int watchdog_cdev_register(struct watchdog_device *wdd)
989 {
990         struct watchdog_core_data *wd_data;
991         int err;
992
993         wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
994         if (!wd_data)
995                 return -ENOMEM;
996         mutex_init(&wd_data->lock);
997
998         wd_data->wdd = wdd;
999         wdd->wd_data = wd_data;
1000
1001         if (IS_ERR_OR_NULL(watchdog_kworker)) {
1002                 kfree(wd_data);
1003                 return -ENODEV;
1004         }
1005
1006         device_initialize(&wd_data->dev);
1007         wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
1008         wd_data->dev.class = &watchdog_class;
1009         wd_data->dev.parent = wdd->parent;
1010         wd_data->dev.groups = wdd->groups;
1011         wd_data->dev.release = watchdog_core_data_release;
1012         dev_set_drvdata(&wd_data->dev, wdd);
1013         dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
1014
1015         kthread_init_work(&wd_data->work, watchdog_ping_work);
1016         hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1017         wd_data->timer.function = watchdog_timer_expired;
1018         watchdog_hrtimer_pretimeout_init(wdd);
1019
1020         if (wdd->id == 0) {
1021                 old_wd_data = wd_data;
1022                 watchdog_miscdev.parent = wdd->parent;
1023                 err = misc_register(&watchdog_miscdev);
1024                 if (err != 0) {
1025                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
1026                                 wdd->info->identity, WATCHDOG_MINOR, err);
1027                         if (err == -EBUSY)
1028                                 pr_err("%s: a legacy watchdog module is probably present.\n",
1029                                         wdd->info->identity);
1030                         old_wd_data = NULL;
1031                         put_device(&wd_data->dev);
1032                         return err;
1033                 }
1034         }
1035
1036         /* Fill in the data structures */
1037         cdev_init(&wd_data->cdev, &watchdog_fops);
1038
1039         /* Add the device */
1040         err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1041         if (err) {
1042                 pr_err("watchdog%d unable to add device %d:%d\n",
1043                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
1044                 if (wdd->id == 0) {
1045                         misc_deregister(&watchdog_miscdev);
1046                         old_wd_data = NULL;
1047                         put_device(&wd_data->dev);
1048                 }
1049                 return err;
1050         }
1051
1052         wd_data->cdev.owner = wdd->ops->owner;
1053
1054         /* Record time of most recent heartbeat as 'just before now'. */
1055         wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1056         watchdog_set_open_deadline(wd_data);
1057
1058         /*
1059          * If the watchdog is running, prevent its driver from being unloaded,
1060          * and schedule an immediate ping.
1061          */
1062         if (watchdog_hw_running(wdd)) {
1063                 __module_get(wdd->ops->owner);
1064                 get_device(&wd_data->dev);
1065                 if (handle_boot_enabled)
1066                         hrtimer_start(&wd_data->timer, 0,
1067                                       HRTIMER_MODE_REL_HARD);
1068                 else
1069                         pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1070                                 wdd->id);
1071         }
1072
1073         return 0;
1074 }
1075
1076 /*
1077  *      watchdog_cdev_unregister: unregister watchdog character device
1078  *      @watchdog: watchdog device
1079  *
1080  *      Unregister watchdog character device and if needed the legacy
1081  *      /dev/watchdog device.
1082  */
1083
1084 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1085 {
1086         struct watchdog_core_data *wd_data = wdd->wd_data;
1087
1088         cdev_device_del(&wd_data->cdev, &wd_data->dev);
1089         if (wdd->id == 0) {
1090                 misc_deregister(&watchdog_miscdev);
1091                 old_wd_data = NULL;
1092         }
1093
1094         if (watchdog_active(wdd) &&
1095             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1096                 watchdog_stop(wdd);
1097         }
1098
1099         watchdog_hrtimer_pretimeout_stop(wdd);
1100
1101         mutex_lock(&wd_data->lock);
1102         wd_data->wdd = NULL;
1103         wdd->wd_data = NULL;
1104         mutex_unlock(&wd_data->lock);
1105
1106         hrtimer_cancel(&wd_data->timer);
1107         kthread_cancel_work_sync(&wd_data->work);
1108
1109         put_device(&wd_data->dev);
1110 }
1111
1112 /*
1113  *      watchdog_dev_register: register a watchdog device
1114  *      @wdd: watchdog device
1115  *
1116  *      Register a watchdog device including handling the legacy
1117  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1118  *      thus we set it up like that.
1119  */
1120
1121 int watchdog_dev_register(struct watchdog_device *wdd)
1122 {
1123         int ret;
1124
1125         ret = watchdog_cdev_register(wdd);
1126         if (ret)
1127                 return ret;
1128
1129         ret = watchdog_register_pretimeout(wdd);
1130         if (ret)
1131                 watchdog_cdev_unregister(wdd);
1132
1133         return ret;
1134 }
1135
1136 /*
1137  *      watchdog_dev_unregister: unregister a watchdog device
1138  *      @watchdog: watchdog device
1139  *
1140  *      Unregister watchdog device and if needed the legacy
1141  *      /dev/watchdog device.
1142  */
1143
1144 void watchdog_dev_unregister(struct watchdog_device *wdd)
1145 {
1146         watchdog_unregister_pretimeout(wdd);
1147         watchdog_cdev_unregister(wdd);
1148 }
1149
1150 /*
1151  *      watchdog_set_last_hw_keepalive: set last HW keepalive time for watchdog
1152  *      @wdd: watchdog device
1153  *      @last_ping_ms: time since last HW heartbeat
1154  *
1155  *      Adjusts the last known HW keepalive time for a watchdog timer.
1156  *      This is needed if the watchdog is already running when the probe
1157  *      function is called, and it can't be pinged immediately. This
1158  *      function must be called immediately after watchdog registration,
1159  *      and min_hw_heartbeat_ms must be set for this to be useful.
1160  */
1161 int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
1162                                    unsigned int last_ping_ms)
1163 {
1164         struct watchdog_core_data *wd_data;
1165         ktime_t now;
1166
1167         if (!wdd)
1168                 return -EINVAL;
1169
1170         wd_data = wdd->wd_data;
1171
1172         now = ktime_get();
1173
1174         wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));
1175
1176         if (watchdog_hw_running(wdd) && handle_boot_enabled)
1177                 return __watchdog_ping(wdd);
1178
1179         return 0;
1180 }
1181 EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);
1182
1183 /*
1184  *      watchdog_dev_init: init dev part of watchdog core
1185  *
1186  *      Allocate a range of chardev nodes to use for watchdog devices
1187  */
1188
1189 int __init watchdog_dev_init(void)
1190 {
1191         int err;
1192
1193         watchdog_kworker = kthread_create_worker(0, "watchdogd");
1194         if (IS_ERR(watchdog_kworker)) {
1195                 pr_err("Failed to create watchdog kworker\n");
1196                 return PTR_ERR(watchdog_kworker);
1197         }
1198         sched_set_fifo(watchdog_kworker->task);
1199
1200         err = class_register(&watchdog_class);
1201         if (err < 0) {
1202                 pr_err("couldn't register class\n");
1203                 goto err_register;
1204         }
1205
1206         err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1207         if (err < 0) {
1208                 pr_err("watchdog: unable to allocate char dev region\n");
1209                 goto err_alloc;
1210         }
1211
1212         return 0;
1213
1214 err_alloc:
1215         class_unregister(&watchdog_class);
1216 err_register:
1217         kthread_destroy_worker(watchdog_kworker);
1218         return err;
1219 }
1220
1221 /*
1222  *      watchdog_dev_exit: exit dev part of watchdog core
1223  *
1224  *      Release the range of chardev nodes used for watchdog devices
1225  */
1226
1227 void __exit watchdog_dev_exit(void)
1228 {
1229         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1230         class_unregister(&watchdog_class);
1231         kthread_destroy_worker(watchdog_kworker);
1232 }
1233
1234 int watchdog_dev_suspend(struct watchdog_device *wdd)
1235 {
1236         struct watchdog_core_data *wd_data = wdd->wd_data;
1237         int ret = 0;
1238
1239         if (!wdd->wd_data)
1240                 return -ENODEV;
1241
1242         /* ping for the last time before suspend */
1243         mutex_lock(&wd_data->lock);
1244         if (watchdog_worker_should_ping(wd_data))
1245                 ret = __watchdog_ping(wd_data->wdd);
1246         mutex_unlock(&wd_data->lock);
1247
1248         if (ret)
1249                 return ret;
1250
1251         /*
1252          * make sure that watchdog worker will not kick in when the wdog is
1253          * suspended
1254          */
1255         hrtimer_cancel(&wd_data->timer);
1256         kthread_cancel_work_sync(&wd_data->work);
1257
1258         return 0;
1259 }
1260
1261 int watchdog_dev_resume(struct watchdog_device *wdd)
1262 {
1263         struct watchdog_core_data *wd_data = wdd->wd_data;
1264         int ret = 0;
1265
1266         if (!wdd->wd_data)
1267                 return -ENODEV;
1268
1269         /*
1270          * __watchdog_ping will also retrigger hrtimer and therefore restore the
1271          * ping worker if needed.
1272          */
1273         mutex_lock(&wd_data->lock);
1274         if (watchdog_worker_should_ping(wd_data))
1275                 ret = __watchdog_ping(wd_data->wdd);
1276         mutex_unlock(&wd_data->lock);
1277
1278         return ret;
1279 }
1280
1281 module_param(handle_boot_enabled, bool, 0444);
1282 MODULE_PARM_DESC(handle_boot_enabled,
1283         "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1284         __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1285
1286 module_param(open_timeout, uint, 0644);
1287 MODULE_PARM_DESC(open_timeout,
1288         "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1289         __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");