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  *
  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  */
  59 struct 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 */
  76 static dev_t watchdog_devt;
  77 /* Reference to watchdog device behind /dev/watchdog */
  78 static struct watchdog_core_data *old_wd_data;
  79
  80 static struct kthread_worker *watchdog_kworker;
  81
  82 static bool handle_boot_enabled =
  83         IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
  84
  85 static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
  86
  87 static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
  88 {
  89         return ktime_after(ktime_get(), data->open_deadline);
  90 }
  91
  92 static 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
  98 static 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
 121 static 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
 151 static 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
 166 static 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
 207 static 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
 220 static 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
 233 static 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
 245 static 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
 266 static 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
 307 static 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
 344 static 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
 377 static 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
 408 static 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
 437 static 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
 451 static 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
 459 static 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 }
 477 static DEVICE_ATTR_RW(nowayout);
 478
 479 static 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 }
 492 static DEVICE_ATTR_RO(status);
 493
 494 static 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 }
 501 static DEVICE_ATTR_RO(bootstatus);
 502
 503 static 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 }
 519 static DEVICE_ATTR_RO(timeleft);
 520
 521 static 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 }
 528 static DEVICE_ATTR_RO(timeout);
 529
 530 static 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 }
 537 static DEVICE_ATTR_RO(pretimeout);
 538
 539 static 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 }
 546 static DEVICE_ATTR_RO(identity);
 547
 548 static 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 }
 558 static DEVICE_ATTR_RO(state);
 559
 560 static 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 }
 565 static DEVICE_ATTR_RO(pretimeout_available_governors);
 566
 567 static 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
 576 static 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 }
 588 static DEVICE_ATTR_RW(pretimeout_governor);
 589
 590 static 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 }
 610 static 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
 624 static 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
 642 static 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
 663 static 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
 714 static 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
 812 out_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
 827 static 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
 878 out_mod:
 879         module_put(wd_data->wdd->ops->owner);
 880 out_clear:
 881         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 882         return err;
 883 }
 884
 885 static 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
 904 static 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
 939 done:
 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
 954 static 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
 963 static struct miscdevice watchdog_miscdev = {
 964         .minor          = WATCHDOG_MINOR,
 965         .name           = "watchdog",
 966         .fops           = &watchdog_fops,
 967 };
 968
 969 static 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
 984 static 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
1077 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1078 {
1079         struct watchdog_core_data *wd_data = wdd->wd_data;
1080
1081         cdev_device_del(&wd_data->cdev, &wd_data->dev);
1082         if (wdd->id == 0) {
1083                 misc_deregister(&watchdog_miscdev);
1084                 old_wd_data = NULL;
1085         }
1086
1087         if (watchdog_active(wdd) &&
1088             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1089                 watchdog_stop(wdd);
1090         }
1091
1092         mutex_lock(&wd_data->lock);
1093         wd_data->wdd = NULL;
1094         wdd->wd_data = NULL;
1095         mutex_unlock(&wd_data->lock);
1096
1097         hrtimer_cancel(&wd_data->timer);
1098         kthread_cancel_work_sync(&wd_data->work);
1099
1100         put_device(&wd_data->dev);
1101 }
1102
1103 /*
1104  *      watchdog_dev_register: register a watchdog device
1105  *      @wdd: watchdog device
1106  *
1107  *      Register a watchdog device including handling the legacy
1108  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1109  *      thus we set it up like that.
1110  */
1111
1112 int watchdog_dev_register(struct watchdog_device *wdd)
1113 {
1114         int ret;
1115
1116         ret = watchdog_cdev_register(wdd);
1117         if (ret)
1118                 return ret;
1119
1120         ret = watchdog_register_pretimeout(wdd);
1121         if (ret)
1122                 watchdog_cdev_unregister(wdd);
1123
1124         return ret;
1125 }
1126
1127 /*
1128  *      watchdog_dev_unregister: unregister a watchdog device
1129  *      @watchdog: watchdog device
1130  *
1131  *      Unregister watchdog device and if needed the legacy
1132  *      /dev/watchdog device.
1133  */
1134
1135 void watchdog_dev_unregister(struct watchdog_device *wdd)
1136 {
1137         watchdog_unregister_pretimeout(wdd);
1138         watchdog_cdev_unregister(wdd);
1139 }
1140
1141 /*
1142  *      watchdog_set_last_hw_keepalive: set last HW keepalive time for watchdog
1143  *      @wdd: watchdog device
1144  *      @last_ping_ms: time since last HW heartbeat
1145  *
1146  *      Adjusts the last known HW keepalive time for a watchdog timer.
1147  *      This is needed if the watchdog is already running when the probe
1148  *      function is called, and it can't be pinged immediately. This
1149  *      function must be called immediately after watchdog registration,
1150  *      and min_hw_heartbeat_ms must be set for this to be useful.
1151  */
1152 int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
1153                                    unsigned int last_ping_ms)
1154 {
1155         struct watchdog_core_data *wd_data;
1156         ktime_t now;
1157
1158         if (!wdd)
1159                 return -EINVAL;
1160
1161         wd_data = wdd->wd_data;
1162
1163         now = ktime_get();
1164
1165         wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));
1166
1167         return __watchdog_ping(wdd);
1168 }
1169 EXPORT_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
1177 int __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
1202 err_alloc:
1203         class_unregister(&watchdog_class);
1204 err_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
1215 void __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
1222 module_param(handle_boot_enabled, bool, 0444);
1223 MODULE_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
1227 module_param(open_timeout, uint, 0644);
1228 MODULE_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) ")");