linux/drivers/watchdog/watchdog_dev.c
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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 *      (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 */
  51static dev_t watchdog_devt;
  52/* Reference to watchdog device behind /dev/watchdog */
  53static struct watchdog_core_data *old_wd_data;
  54
  55static struct kthread_worker *watchdog_kworker;
  56
  57static bool handle_boot_enabled =
  58        IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
  59
  60static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
  61
  62static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
  63{
  64        return ktime_after(ktime_get(), data->open_deadline);
  65}
  66
  67static 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
  73static 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
  96static 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
 126static 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
 141static 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
 185static 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
 198static 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
 211static 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
 223static 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
 244static 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
 288static 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
 326static 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
 362static 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
 393static 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)
 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
 422static 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
 436static 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
 445static 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}
 463static DEVICE_ATTR_RW(nowayout);
 464
 465static 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}
 478static DEVICE_ATTR_RO(status);
 479
 480static 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}
 487static DEVICE_ATTR_RO(bootstatus);
 488
 489static 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}
 505static DEVICE_ATTR_RO(timeleft);
 506
 507static 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}
 514static DEVICE_ATTR_RO(timeout);
 515
 516static 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}
 523static DEVICE_ATTR_RO(min_timeout);
 524
 525static 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}
 532static DEVICE_ATTR_RO(max_timeout);
 533
 534static 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}
 541static DEVICE_ATTR_RO(pretimeout);
 542
 543static 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}
 550static DEVICE_ATTR_RO(identity);
 551
 552static 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}
 562static DEVICE_ATTR_RO(state);
 563
 564static 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}
 569static DEVICE_ATTR_RO(pretimeout_available_governors);
 570
 571static 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
 580static 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}
 592static DEVICE_ATTR_RW(pretimeout_governor);
 593
 594static 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}
 612static 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
 628static 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
 646static 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
 667static 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
 718static 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
 816out_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
 831static 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
 882out_mod:
 883        module_put(wd_data->wdd->ops->owner);
 884out_clear:
 885        clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 886        return err;
 887}
 888
 889static 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
 908static 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
 943done:
 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
 958static 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
 967static struct miscdevice watchdog_miscdev = {
 968        .minor          = WATCHDOG_MINOR,
 969        .name           = "watchdog",
 970        .fops           = &watchdog_fops,
 971};
 972
 973static 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
 988static 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
1084static 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        mutex_lock(&wd_data->lock);
1100        wd_data->wdd = NULL;
1101        wdd->wd_data = NULL;
1102        mutex_unlock(&wd_data->lock);
1103
1104        hrtimer_cancel(&wd_data->timer);
1105        kthread_cancel_work_sync(&wd_data->work);
1106        watchdog_hrtimer_pretimeout_stop(wdd);
1107
1108        put_device(&wd_data->dev);
1109}
1110
1111/*
1112 *      watchdog_dev_register: register a watchdog device
1113 *      @wdd: watchdog device
1114 *
1115 *      Register a watchdog device including handling the legacy
1116 *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1117 *      thus we set it up like that.
1118 */
1119
1120int watchdog_dev_register(struct watchdog_device *wdd)
1121{
1122        int ret;
1123
1124        ret = watchdog_cdev_register(wdd);
1125        if (ret)
1126                return ret;
1127
1128        ret = watchdog_register_pretimeout(wdd);
1129        if (ret)
1130                watchdog_cdev_unregister(wdd);
1131
1132        return ret;
1133}
1134
1135/*
1136 *      watchdog_dev_unregister: unregister a watchdog device
1137 *      @watchdog: watchdog device
1138 *
1139 *      Unregister watchdog device and if needed the legacy
1140 *      /dev/watchdog device.
1141 */
1142
1143void watchdog_dev_unregister(struct watchdog_device *wdd)
1144{
1145        watchdog_unregister_pretimeout(wdd);
1146        watchdog_cdev_unregister(wdd);
1147}
1148
1149/*
1150 *      watchdog_set_last_hw_keepalive: set last HW keepalive time for watchdog
1151 *      @wdd: watchdog device
1152 *      @last_ping_ms: time since last HW heartbeat
1153 *
1154 *      Adjusts the last known HW keepalive time for a watchdog timer.
1155 *      This is needed if the watchdog is already running when the probe
1156 *      function is called, and it can't be pinged immediately. This
1157 *      function must be called immediately after watchdog registration,
1158 *      and min_hw_heartbeat_ms must be set for this to be useful.
1159 */
1160int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
1161                                   unsigned int last_ping_ms)
1162{
1163        struct watchdog_core_data *wd_data;
1164        ktime_t now;
1165
1166        if (!wdd)
1167                return -EINVAL;
1168
1169        wd_data = wdd->wd_data;
1170
1171        now = ktime_get();
1172
1173        wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));
1174
1175        return __watchdog_ping(wdd);
1176}
1177EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);
1178
1179/*
1180 *      watchdog_dev_init: init dev part of watchdog core
1181 *
1182 *      Allocate a range of chardev nodes to use for watchdog devices
1183 */
1184
1185int __init watchdog_dev_init(void)
1186{
1187        int err;
1188
1189        watchdog_kworker = kthread_create_worker(0, "watchdogd");
1190        if (IS_ERR(watchdog_kworker)) {
1191                pr_err("Failed to create watchdog kworker\n");
1192                return PTR_ERR(watchdog_kworker);
1193        }
1194        sched_set_fifo(watchdog_kworker->task);
1195
1196        err = class_register(&watchdog_class);
1197        if (err < 0) {
1198                pr_err("couldn't register class\n");
1199                goto err_register;
1200        }
1201
1202        err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1203        if (err < 0) {
1204                pr_err("watchdog: unable to allocate char dev region\n");
1205                goto err_alloc;
1206        }
1207
1208        return 0;
1209
1210err_alloc:
1211        class_unregister(&watchdog_class);
1212err_register:
1213        kthread_destroy_worker(watchdog_kworker);
1214        return err;
1215}
1216
1217/*
1218 *      watchdog_dev_exit: exit dev part of watchdog core
1219 *
1220 *      Release the range of chardev nodes used for watchdog devices
1221 */
1222
1223void __exit watchdog_dev_exit(void)
1224{
1225        unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1226        class_unregister(&watchdog_class);
1227        kthread_destroy_worker(watchdog_kworker);
1228}
1229
1230module_param(handle_boot_enabled, bool, 0444);
1231MODULE_PARM_DESC(handle_boot_enabled,
1232        "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1233        __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1234
1235module_param(open_timeout, uint, 0644);
1236MODULE_PARM_DESC(open_timeout,
1237        "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1238        __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");
1239