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) ")");