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 */
  59struct 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 */
  76static dev_t watchdog_devt;
  77/* Reference to watchdog device behind /dev/watchdog */
  78static struct watchdog_core_data *old_wd_data;
  79
  80static struct kthread_worker *watchdog_kworker;
  81
  82static bool handle_boot_enabled =
  83	IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
  84
  85static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
  86
  87static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
  88{
  89	return ktime_after(ktime_get(), data->open_deadline);
  90}
  91
  92static 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
  98static 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
 121static 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
 151static 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
 166static 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
 207static 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
 220static 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
 233static 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
 245static 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
 266static 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 = __watchdog_ping(wdd);
 280		if (err == 0)
 281			set_bit(WDOG_ACTIVE, &wdd->status);
 282	} else {
 283		err = wdd->ops->start(wdd);
 284		if (err == 0) {
 285			set_bit(WDOG_ACTIVE, &wdd->status);
 286			wd_data->last_keepalive = started_at;
 287			wd_data->last_hw_keepalive = started_at;
 288			watchdog_update_worker(wdd);
 289		}
 290	}
 291
 292	return err;
 293}
 294
 295/*
 296 *	watchdog_stop: wrapper to stop the watchdog.
 297 *	@wdd: the watchdog device to stop
 298 *
 299 *	The caller must hold wd_data->lock.
 300 *
 301 *	Stop the watchdog if it is still active and unmark it active.
 302 *	This function returns zero on success or a negative errno code for
 303 *	failure.
 304 *	If the 'nowayout' feature was set, the watchdog cannot be stopped.
 305 */
 306
 307static int watchdog_stop(struct watchdog_device *wdd)
 308{
 309	int err = 0;
 310
 311	if (!watchdog_active(wdd))
 312		return 0;
 313
 314	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
 315		pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
 316			wdd->id);
 317		return -EBUSY;
 318	}
 319
 320	if (wdd->ops->stop) {
 321		clear_bit(WDOG_HW_RUNNING, &wdd->status);
 322		err = wdd->ops->stop(wdd);
 323	} else {
 324		set_bit(WDOG_HW_RUNNING, &wdd->status);
 325	}
 326
 327	if (err == 0) {
 328		clear_bit(WDOG_ACTIVE, &wdd->status);
 329		watchdog_update_worker(wdd);
 
 330	}
 331
 332	return err;
 333}
 334
 335/*
 336 *	watchdog_get_status: wrapper to get the watchdog status
 337 *	@wdd: the watchdog device to get the status from
 338 *
 339 *	The caller must hold wd_data->lock.
 340 *
 341 *	Get the watchdog's status flags.
 342 */
 343
 344static unsigned int watchdog_get_status(struct watchdog_device *wdd)
 345{
 346	struct watchdog_core_data *wd_data = wdd->wd_data;
 347	unsigned int status;
 348
 349	if (wdd->ops->status)
 350		status = wdd->ops->status(wdd);
 351	else
 352		status = wdd->bootstatus & (WDIOF_CARDRESET |
 353					    WDIOF_OVERHEAT |
 354					    WDIOF_FANFAULT |
 355					    WDIOF_EXTERN1 |
 356					    WDIOF_EXTERN2 |
 357					    WDIOF_POWERUNDER |
 358					    WDIOF_POWEROVER);
 359
 360	if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
 361		status |= WDIOF_MAGICCLOSE;
 362
 363	if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
 364		status |= WDIOF_KEEPALIVEPING;
 365
 366	return status;
 367}
 368
 369/*
 370 *	watchdog_set_timeout: set the watchdog timer timeout
 371 *	@wdd: the watchdog device to set the timeout for
 372 *	@timeout: timeout to set in seconds
 373 *
 374 *	The caller must hold wd_data->lock.
 375 */
 376
 377static int watchdog_set_timeout(struct watchdog_device *wdd,
 378							unsigned int timeout)
 379{
 380	int err = 0;
 381
 382	if (!(wdd->info->options & WDIOF_SETTIMEOUT))
 383		return -EOPNOTSUPP;
 384
 385	if (watchdog_timeout_invalid(wdd, timeout))
 386		return -EINVAL;
 387
 388	if (wdd->ops->set_timeout) {
 389		err = wdd->ops->set_timeout(wdd, timeout);
 390	} else {
 391		wdd->timeout = timeout;
 392		/* Disable pretimeout if it doesn't fit the new timeout */
 393		if (wdd->pretimeout >= wdd->timeout)
 394			wdd->pretimeout = 0;
 395	}
 396
 397	watchdog_update_worker(wdd);
 398
 399	return err;
 400}
 401
 402/*
 403 *	watchdog_set_pretimeout: set the watchdog timer pretimeout
 404 *	@wdd: the watchdog device to set the timeout for
 405 *	@timeout: pretimeout to set in seconds
 406 */
 407
 408static int watchdog_set_pretimeout(struct watchdog_device *wdd,
 409				   unsigned int timeout)
 410{
 411	int err = 0;
 412
 413	if (!(wdd->info->options & WDIOF_PRETIMEOUT))
 414		return -EOPNOTSUPP;
 415
 416	if (watchdog_pretimeout_invalid(wdd, timeout))
 417		return -EINVAL;
 418
 419	if (wdd->ops->set_pretimeout)
 420		err = wdd->ops->set_pretimeout(wdd, timeout);
 421	else
 422		wdd->pretimeout = timeout;
 423
 424	return err;
 425}
 426
 427/*
 428 *	watchdog_get_timeleft: wrapper to get the time left before a reboot
 429 *	@wdd: the watchdog device to get the remaining time from
 430 *	@timeleft: the time that's left
 431 *
 432 *	The caller must hold wd_data->lock.
 433 *
 434 *	Get the time before a watchdog will reboot (if not pinged).
 435 */
 436
 437static int watchdog_get_timeleft(struct watchdog_device *wdd,
 438							unsigned int *timeleft)
 439{
 440	*timeleft = 0;
 441
 442	if (!wdd->ops->get_timeleft)
 443		return -EOPNOTSUPP;
 444
 445	*timeleft = wdd->ops->get_timeleft(wdd);
 446
 447	return 0;
 448}
 449
 450#ifdef CONFIG_WATCHDOG_SYSFS
 451static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
 452				char *buf)
 453{
 454	struct watchdog_device *wdd = dev_get_drvdata(dev);
 455
 456	return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
 457}
 458
 459static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,
 460				const char *buf, size_t len)
 461{
 462	struct watchdog_device *wdd = dev_get_drvdata(dev);
 463	unsigned int value;
 464	int ret;
 465
 466	ret = kstrtouint(buf, 0, &value);
 467	if (ret)
 468		return ret;
 469	if (value > 1)
 470		return -EINVAL;
 471	/* nowayout cannot be disabled once set */
 472	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)
 473		return -EPERM;
 474	watchdog_set_nowayout(wdd, value);
 475	return len;
 476}
 477static DEVICE_ATTR_RW(nowayout);
 478
 479static ssize_t status_show(struct device *dev, struct device_attribute *attr,
 480				char *buf)
 481{
 482	struct watchdog_device *wdd = dev_get_drvdata(dev);
 483	struct watchdog_core_data *wd_data = wdd->wd_data;
 484	unsigned int status;
 485
 486	mutex_lock(&wd_data->lock);
 487	status = watchdog_get_status(wdd);
 488	mutex_unlock(&wd_data->lock);
 489
 490	return sprintf(buf, "0x%x\n", status);
 491}
 492static DEVICE_ATTR_RO(status);
 493
 494static ssize_t bootstatus_show(struct device *dev,
 495				struct device_attribute *attr, char *buf)
 496{
 497	struct watchdog_device *wdd = dev_get_drvdata(dev);
 498
 499	return sprintf(buf, "%u\n", wdd->bootstatus);
 500}
 501static DEVICE_ATTR_RO(bootstatus);
 502
 503static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
 504				char *buf)
 505{
 506	struct watchdog_device *wdd = dev_get_drvdata(dev);
 507	struct watchdog_core_data *wd_data = wdd->wd_data;
 508	ssize_t status;
 509	unsigned int val;
 510
 511	mutex_lock(&wd_data->lock);
 512	status = watchdog_get_timeleft(wdd, &val);
 513	mutex_unlock(&wd_data->lock);
 514	if (!status)
 515		status = sprintf(buf, "%u\n", val);
 516
 517	return status;
 518}
 519static DEVICE_ATTR_RO(timeleft);
 520
 521static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
 522				char *buf)
 523{
 524	struct watchdog_device *wdd = dev_get_drvdata(dev);
 525
 526	return sprintf(buf, "%u\n", wdd->timeout);
 527}
 528static DEVICE_ATTR_RO(timeout);
 529
 530static ssize_t pretimeout_show(struct device *dev,
 531			       struct device_attribute *attr, char *buf)
 532{
 533	struct watchdog_device *wdd = dev_get_drvdata(dev);
 534
 535	return sprintf(buf, "%u\n", wdd->pretimeout);
 536}
 537static DEVICE_ATTR_RO(pretimeout);
 538
 539static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
 540				char *buf)
 541{
 542	struct watchdog_device *wdd = dev_get_drvdata(dev);
 543
 544	return sprintf(buf, "%s\n", wdd->info->identity);
 545}
 546static DEVICE_ATTR_RO(identity);
 547
 548static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 549				char *buf)
 550{
 551	struct watchdog_device *wdd = dev_get_drvdata(dev);
 552
 553	if (watchdog_active(wdd))
 554		return sprintf(buf, "active\n");
 555
 556	return sprintf(buf, "inactive\n");
 557}
 558static DEVICE_ATTR_RO(state);
 559
 560static ssize_t pretimeout_available_governors_show(struct device *dev,
 561				   struct device_attribute *attr, char *buf)
 562{
 563	return watchdog_pretimeout_available_governors_get(buf);
 564}
 565static DEVICE_ATTR_RO(pretimeout_available_governors);
 566
 567static ssize_t pretimeout_governor_show(struct device *dev,
 568					struct device_attribute *attr,
 569					char *buf)
 570{
 571	struct watchdog_device *wdd = dev_get_drvdata(dev);
 572
 573	return watchdog_pretimeout_governor_get(wdd, buf);
 574}
 575
 576static ssize_t pretimeout_governor_store(struct device *dev,
 577					 struct device_attribute *attr,
 578					 const char *buf, size_t count)
 579{
 580	struct watchdog_device *wdd = dev_get_drvdata(dev);
 581	int ret = watchdog_pretimeout_governor_set(wdd, buf);
 582
 583	if (!ret)
 584		ret = count;
 585
 586	return ret;
 587}
 588static DEVICE_ATTR_RW(pretimeout_governor);
 589
 590static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
 591				int n)
 592{
 593	struct device *dev = kobj_to_dev(kobj);
 594	struct watchdog_device *wdd = dev_get_drvdata(dev);
 595	umode_t mode = attr->mode;
 596
 597	if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
 598		mode = 0;
 599	else if (attr == &dev_attr_pretimeout.attr &&
 600		 !(wdd->info->options & WDIOF_PRETIMEOUT))
 601		mode = 0;
 602	else if ((attr == &dev_attr_pretimeout_governor.attr ||
 603		  attr == &dev_attr_pretimeout_available_governors.attr) &&
 604		 (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
 605		  !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
 606		mode = 0;
 607
 608	return mode;
 609}
 610static struct attribute *wdt_attrs[] = {
 611	&dev_attr_state.attr,
 612	&dev_attr_identity.attr,
 613	&dev_attr_timeout.attr,
 614	&dev_attr_pretimeout.attr,
 615	&dev_attr_timeleft.attr,
 616	&dev_attr_bootstatus.attr,
 617	&dev_attr_status.attr,
 618	&dev_attr_nowayout.attr,
 619	&dev_attr_pretimeout_governor.attr,
 620	&dev_attr_pretimeout_available_governors.attr,
 621	NULL,
 622};
 623
 624static const struct attribute_group wdt_group = {
 625	.attrs = wdt_attrs,
 626	.is_visible = wdt_is_visible,
 627};
 628__ATTRIBUTE_GROUPS(wdt);
 629#else
 630#define wdt_groups	NULL
 631#endif
 632
 633/*
 634 *	watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 635 *	@wdd: the watchdog device to do the ioctl on
 636 *	@cmd: watchdog command
 637 *	@arg: argument pointer
 638 *
 639 *	The caller must hold wd_data->lock.
 640 */
 641
 642static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
 643							unsigned long arg)
 644{
 645	if (!wdd->ops->ioctl)
 646		return -ENOIOCTLCMD;
 647
 648	return wdd->ops->ioctl(wdd, cmd, arg);
 649}
 650
 651/*
 652 *	watchdog_write: writes to the watchdog.
 653 *	@file: file from VFS
 654 *	@data: user address of data
 655 *	@len: length of data
 656 *	@ppos: pointer to the file offset
 657 *
 658 *	A write to a watchdog device is defined as a keepalive ping.
 659 *	Writing the magic 'V' sequence allows the next close to turn
 660 *	off the watchdog (if 'nowayout' is not set).
 661 */
 662
 663static ssize_t watchdog_write(struct file *file, const char __user *data,
 664						size_t len, loff_t *ppos)
 665{
 666	struct watchdog_core_data *wd_data = file->private_data;
 667	struct watchdog_device *wdd;
 668	int err;
 669	size_t i;
 670	char c;
 671
 672	if (len == 0)
 673		return 0;
 674
 675	/*
 676	 * Note: just in case someone wrote the magic character
 677	 * five months ago...
 678	 */
 679	clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 680
 681	/* scan to see whether or not we got the magic character */
 682	for (i = 0; i != len; i++) {
 683		if (get_user(c, data + i))
 684			return -EFAULT;
 685		if (c == 'V')
 686			set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 687	}
 688
 689	/* someone wrote to us, so we send the watchdog a keepalive ping */
 690
 691	err = -ENODEV;
 692	mutex_lock(&wd_data->lock);
 693	wdd = wd_data->wdd;
 694	if (wdd)
 695		err = watchdog_ping(wdd);
 696	mutex_unlock(&wd_data->lock);
 697
 698	if (err < 0)
 699		return err;
 700
 701	return len;
 702}
 703
 704/*
 705 *	watchdog_ioctl: handle the different ioctl's for the watchdog device.
 706 *	@file: file handle to the device
 707 *	@cmd: watchdog command
 708 *	@arg: argument pointer
 709 *
 710 *	The watchdog API defines a common set of functions for all watchdogs
 711 *	according to their available features.
 712 */
 713
 714static long watchdog_ioctl(struct file *file, unsigned int cmd,
 715							unsigned long arg)
 716{
 717	struct watchdog_core_data *wd_data = file->private_data;
 718	void __user *argp = (void __user *)arg;
 719	struct watchdog_device *wdd;
 720	int __user *p = argp;
 721	unsigned int val;
 722	int err;
 723
 724	mutex_lock(&wd_data->lock);
 725
 726	wdd = wd_data->wdd;
 727	if (!wdd) {
 728		err = -ENODEV;
 729		goto out_ioctl;
 730	}
 731
 732	err = watchdog_ioctl_op(wdd, cmd, arg);
 733	if (err != -ENOIOCTLCMD)
 734		goto out_ioctl;
 735
 736	switch (cmd) {
 737	case WDIOC_GETSUPPORT:
 738		err = copy_to_user(argp, wdd->info,
 739			sizeof(struct watchdog_info)) ? -EFAULT : 0;
 740		break;
 741	case WDIOC_GETSTATUS:
 742		val = watchdog_get_status(wdd);
 743		err = put_user(val, p);
 744		break;
 745	case WDIOC_GETBOOTSTATUS:
 746		err = put_user(wdd->bootstatus, p);
 747		break;
 748	case WDIOC_SETOPTIONS:
 749		if (get_user(val, p)) {
 750			err = -EFAULT;
 751			break;
 752		}
 753		if (val & WDIOS_DISABLECARD) {
 754			err = watchdog_stop(wdd);
 755			if (err < 0)
 756				break;
 757		}
 758		if (val & WDIOS_ENABLECARD)
 759			err = watchdog_start(wdd);
 760		break;
 761	case WDIOC_KEEPALIVE:
 762		if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
 763			err = -EOPNOTSUPP;
 764			break;
 765		}
 766		err = watchdog_ping(wdd);
 767		break;
 
 
 
 
 768	case WDIOC_SETTIMEOUT:
 769		if (get_user(val, p)) {
 770			err = -EFAULT;
 771			break;
 772		}
 773		err = watchdog_set_timeout(wdd, val);
 
 
 
 
 774		if (err < 0)
 775			break;
 
 776		/* If the watchdog is active then we send a keepalive ping
 777		 * to make sure that the watchdog keep's running (and if
 778		 * possible that it takes the new timeout) */
 779		err = watchdog_ping(wdd);
 780		if (err < 0)
 781			break;
 782		fallthrough;
 783	case WDIOC_GETTIMEOUT:
 784		/* timeout == 0 means that we don't know the timeout */
 785		if (wdd->timeout == 0) {
 786			err = -EOPNOTSUPP;
 787			break;
 788		}
 789		err = put_user(wdd->timeout, p);
 790		break;
 791	case WDIOC_GETTIMELEFT:
 792		err = watchdog_get_timeleft(wdd, &val);
 793		if (err < 0)
 794			break;
 795		err = put_user(val, p);
 796		break;
 797	case WDIOC_SETPRETIMEOUT:
 798		if (get_user(val, p)) {
 799			err = -EFAULT;
 800			break;
 801		}
 802		err = watchdog_set_pretimeout(wdd, val);
 803		break;
 804	case WDIOC_GETPRETIMEOUT:
 805		err = put_user(wdd->pretimeout, p);
 806		break;
 807	default:
 808		err = -ENOTTY;
 809		break;
 810	}
 811
 812out_ioctl:
 813	mutex_unlock(&wd_data->lock);
 814	return err;
 815}
 816
 817/*
 818 *	watchdog_open: open the /dev/watchdog* devices.
 819 *	@inode: inode of device
 820 *	@file: file handle to device
 821 *
 822 *	When the /dev/watchdog* device gets opened, we start the watchdog.
 823 *	Watch out: the /dev/watchdog device is single open, so we make sure
 824 *	it can only be opened once.
 825 */
 826
 827static int watchdog_open(struct inode *inode, struct file *file)
 828{
 829	struct watchdog_core_data *wd_data;
 830	struct watchdog_device *wdd;
 831	bool hw_running;
 832	int err;
 833
 834	/* Get the corresponding watchdog device */
 835	if (imajor(inode) == MISC_MAJOR)
 836		wd_data = old_wd_data;
 837	else
 838		wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
 839				       cdev);
 840
 841	/* the watchdog is single open! */
 842	if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
 843		return -EBUSY;
 844
 845	wdd = wd_data->wdd;
 846
 847	/*
 848	 * If the /dev/watchdog device is open, we don't want the module
 849	 * to be unloaded.
 850	 */
 851	hw_running = watchdog_hw_running(wdd);
 852	if (!hw_running && !try_module_get(wdd->ops->owner)) {
 853		err = -EBUSY;
 854		goto out_clear;
 855	}
 856
 857	err = watchdog_start(wdd);
 858	if (err < 0)
 859		goto out_mod;
 860
 861	file->private_data = wd_data;
 862
 863	if (!hw_running)
 864		get_device(&wd_data->dev);
 865
 866	/*
 867	 * open_timeout only applies for the first open from
 868	 * userspace. Set open_deadline to infinity so that the kernel
 869	 * will take care of an always-running hardware watchdog in
 870	 * case the device gets magic-closed or WDIOS_DISABLECARD is
 871	 * applied.
 872	 */
 873	wd_data->open_deadline = KTIME_MAX;
 874
 875	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 876	return stream_open(inode, file);
 877
 878out_mod:
 879	module_put(wd_data->wdd->ops->owner);
 880out_clear:
 881	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 882	return err;
 883}
 884
 885static void watchdog_core_data_release(struct device *dev)
 886{
 887	struct watchdog_core_data *wd_data;
 888
 889	wd_data = container_of(dev, struct watchdog_core_data, dev);
 890
 891	kfree(wd_data);
 892}
 893
 894/*
 895 *	watchdog_release: release the watchdog device.
 896 *	@inode: inode of device
 897 *	@file: file handle to device
 898 *
 899 *	This is the code for when /dev/watchdog gets closed. We will only
 900 *	stop the watchdog when we have received the magic char (and nowayout
 901 *	was not set), else the watchdog will keep running.
 902 */
 903
 904static int watchdog_release(struct inode *inode, struct file *file)
 905{
 906	struct watchdog_core_data *wd_data = file->private_data;
 907	struct watchdog_device *wdd;
 908	int err = -EBUSY;
 909	bool running;
 910
 911	mutex_lock(&wd_data->lock);
 912
 913	wdd = wd_data->wdd;
 914	if (!wdd)
 915		goto done;
 916
 917	/*
 918	 * We only stop the watchdog if we received the magic character
 919	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 920	 * watchdog_stop will fail.
 921	 */
 922	if (!watchdog_active(wdd))
 923		err = 0;
 924	else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
 925		 !(wdd->info->options & WDIOF_MAGICCLOSE))
 926		err = watchdog_stop(wdd);
 927
 928	/* If the watchdog was not stopped, send a keepalive ping */
 929	if (err < 0) {
 930		pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
 931		watchdog_ping(wdd);
 932	}
 933
 934	watchdog_update_worker(wdd);
 
 935
 936	/* make sure that /dev/watchdog can be re-opened */
 937	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 938
 939done:
 940	running = wdd && watchdog_hw_running(wdd);
 941	mutex_unlock(&wd_data->lock);
 942	/*
 943	 * Allow the owner module to be unloaded again unless the watchdog
 944	 * is still running. If the watchdog is still running, it can not
 945	 * be stopped, and its driver must not be unloaded.
 946	 */
 947	if (!running) {
 948		module_put(wd_data->cdev.owner);
 949		put_device(&wd_data->dev);
 950	}
 951	return 0;
 952}
 953
 954static const struct file_operations watchdog_fops = {
 955	.owner		= THIS_MODULE,
 956	.write		= watchdog_write,
 957	.unlocked_ioctl	= watchdog_ioctl,
 958	.compat_ioctl	= compat_ptr_ioctl,
 959	.open		= watchdog_open,
 960	.release	= watchdog_release,
 961};
 962
 963static struct miscdevice watchdog_miscdev = {
 964	.minor		= WATCHDOG_MINOR,
 965	.name		= "watchdog",
 966	.fops		= &watchdog_fops,
 967};
 968
 969static struct class watchdog_class = {
 970	.name =		"watchdog",
 971	.owner =	THIS_MODULE,
 972	.dev_groups =	wdt_groups,
 973};
 974
 975/*
 976 *	watchdog_cdev_register: register watchdog character device
 977 *	@wdd: watchdog device
 978 *
 979 *	Register a watchdog character device including handling the legacy
 980 *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
 981 *	thus we set it up like that.
 982 */
 983
 984static int watchdog_cdev_register(struct watchdog_device *wdd)
 985{
 986	struct watchdog_core_data *wd_data;
 987	int err;
 988
 989	wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
 990	if (!wd_data)
 991		return -ENOMEM;
 992	mutex_init(&wd_data->lock);
 993
 994	wd_data->wdd = wdd;
 995	wdd->wd_data = wd_data;
 996
 997	if (IS_ERR_OR_NULL(watchdog_kworker))
 998		return -ENODEV;
 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			kfree(wd_data);
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
1077static 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
1112int 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
1135void 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 */
1152int 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	return __watchdog_ping(wdd);
1168}
1169EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);
1170
1171/*
1172 *	watchdog_dev_init: init dev part of watchdog core
1173 *
1174 *	Allocate a range of chardev nodes to use for watchdog devices
1175 */
1176
1177int __init watchdog_dev_init(void)
1178{
1179	int err;
1180
1181	watchdog_kworker = kthread_create_worker(0, "watchdogd");
1182	if (IS_ERR(watchdog_kworker)) {
1183		pr_err("Failed to create watchdog kworker\n");
1184		return PTR_ERR(watchdog_kworker);
1185	}
1186	sched_set_fifo(watchdog_kworker->task);
1187
1188	err = class_register(&watchdog_class);
1189	if (err < 0) {
1190		pr_err("couldn't register class\n");
1191		goto err_register;
1192	}
1193
1194	err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1195	if (err < 0) {
1196		pr_err("watchdog: unable to allocate char dev region\n");
1197		goto err_alloc;
 
1198	}
1199
 
 
 
1200	return 0;
1201
1202err_alloc:
1203	class_unregister(&watchdog_class);
1204err_register:
1205	kthread_destroy_worker(watchdog_kworker);
1206	return err;
1207}
1208
1209/*
1210 *	watchdog_dev_exit: exit dev part of watchdog core
1211 *
1212 *	Release the range of chardev nodes used for watchdog devices
1213 */
1214
1215void __exit watchdog_dev_exit(void)
1216{
1217	unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1218	class_unregister(&watchdog_class);
1219	kthread_destroy_worker(watchdog_kworker);
1220}
1221
1222module_param(handle_boot_enabled, bool, 0444);
1223MODULE_PARM_DESC(handle_boot_enabled,
1224	"Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1225	__MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1226
1227module_param(open_timeout, uint, 0644);
1228MODULE_PARM_DESC(open_timeout,
1229	"Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1230	__MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");