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 = wdd->ops->ping(wdd);
 280         else
 281                 err = wdd->ops->start(wdd);
 282         if (err == 0) {
 283                 set_bit(WDOG_ACTIVE, &wdd->status);
 284                 wd_data->last_keepalive = started_at;
 285                 wd_data->last_hw_keepalive = started_at;
 286                 watchdog_update_worker(wdd);
 287         }
 288
 289         return err;
 290 }
 291
 292 /*
 293  *      watchdog_stop: wrapper to stop the watchdog.
 294  *      @wdd: the watchdog device to stop
 295  *
 296  *      The caller must hold wd_data->lock.
 297  *
 298  *      Stop the watchdog if it is still active and unmark it active.
 299  *      This function returns zero on success or a negative errno code for
 300  *      failure.
 301  *      If the 'nowayout' feature was set, the watchdog cannot be stopped.
 302  */
 303
 304 static int watchdog_stop(struct watchdog_device *wdd)
 305 {
 306         int err = 0;
 307
 308         if (!watchdog_active(wdd))
 309                 return 0;
 310
 311         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
 312                 pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
 313                         wdd->id);
 314                 return -EBUSY;
 315         }
 316
 317         if (wdd->ops->stop) {
 318                 clear_bit(WDOG_HW_RUNNING, &wdd->status);
 319                 err = wdd->ops->stop(wdd);
 320         } else {
 321                 set_bit(WDOG_HW_RUNNING, &wdd->status);
 322         }
 323
 324         if (err == 0) {
 325                 clear_bit(WDOG_ACTIVE, &wdd->status);
 326                 watchdog_update_worker(wdd);
 327         }
 328
 329         return err;
 330 }
 331
 332 /*
 333  *      watchdog_get_status: wrapper to get the watchdog status
 334  *      @wdd: the watchdog device to get the status from
 335  *
 336  *      The caller must hold wd_data->lock.
 337  *
 338  *      Get the watchdog's status flags.
 339  */
 340
 341 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
 342 {
 343         struct watchdog_core_data *wd_data = wdd->wd_data;
 344         unsigned int status;
 345
 346         if (wdd->ops->status)
 347                 status = wdd->ops->status(wdd);
 348         else
 349                 status = wdd->bootstatus & (WDIOF_CARDRESET |
 350                                             WDIOF_OVERHEAT |
 351                                             WDIOF_FANFAULT |
 352                                             WDIOF_EXTERN1 |
 353                                             WDIOF_EXTERN2 |
 354                                             WDIOF_POWERUNDER |
 355                                             WDIOF_POWEROVER);
 356
 357         if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
 358                 status |= WDIOF_MAGICCLOSE;
 359
 360         if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
 361                 status |= WDIOF_KEEPALIVEPING;
 362
 363         return status;
 364 }
 365
 366 /*
 367  *      watchdog_set_timeout: set the watchdog timer timeout
 368  *      @wdd: the watchdog device to set the timeout for
 369  *      @timeout: timeout to set in seconds
 370  *
 371  *      The caller must hold wd_data->lock.
 372  */
 373
 374 static int watchdog_set_timeout(struct watchdog_device *wdd,
 375                                                         unsigned int timeout)
 376 {
 377         int err = 0;
 378
 379         if (!(wdd->info->options & WDIOF_SETTIMEOUT))
 380                 return -EOPNOTSUPP;
 381
 382         if (watchdog_timeout_invalid(wdd, timeout))
 383                 return -EINVAL;
 384
 385         if (wdd->ops->set_timeout) {
 386                 err = wdd->ops->set_timeout(wdd, timeout);
 387         } else {
 388                 wdd->timeout = timeout;
 389                 /* Disable pretimeout if it doesn't fit the new timeout */
 390                 if (wdd->pretimeout >= wdd->timeout)
 391                         wdd->pretimeout = 0;
 392         }
 393
 394         watchdog_update_worker(wdd);
 395
 396         return err;
 397 }
 398
 399 /*
 400  *      watchdog_set_pretimeout: set the watchdog timer pretimeout
 401  *      @wdd: the watchdog device to set the timeout for
 402  *      @timeout: pretimeout to set in seconds
 403  */
 404
 405 static int watchdog_set_pretimeout(struct watchdog_device *wdd,
 406                                    unsigned int timeout)
 407 {
 408         int err = 0;
 409
 410         if (!(wdd->info->options & WDIOF_PRETIMEOUT))
 411                 return -EOPNOTSUPP;
 412
 413         if (watchdog_pretimeout_invalid(wdd, timeout))
 414                 return -EINVAL;
 415
 416         if (wdd->ops->set_pretimeout)
 417                 err = wdd->ops->set_pretimeout(wdd, timeout);
 418         else
 419                 wdd->pretimeout = timeout;
 420
 421         return err;
 422 }
 423
 424 /*
 425  *      watchdog_get_timeleft: wrapper to get the time left before a reboot
 426  *      @wdd: the watchdog device to get the remaining time from
 427  *      @timeleft: the time that's left
 428  *
 429  *      The caller must hold wd_data->lock.
 430  *
 431  *      Get the time before a watchdog will reboot (if not pinged).
 432  */
 433
 434 static int watchdog_get_timeleft(struct watchdog_device *wdd,
 435                                                         unsigned int *timeleft)
 436 {
 437         *timeleft = 0;
 438
 439         if (!wdd->ops->get_timeleft)
 440                 return -EOPNOTSUPP;
 441
 442         *timeleft = wdd->ops->get_timeleft(wdd);
 443
 444         return 0;
 445 }
 446
 447 #ifdef CONFIG_WATCHDOG_SYSFS
 448 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
 449                                 char *buf)
 450 {
 451         struct watchdog_device *wdd = dev_get_drvdata(dev);
 452
 453         return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
 454 }
 455 static DEVICE_ATTR_RO(nowayout);
 456
 457 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
 458                                 char *buf)
 459 {
 460         struct watchdog_device *wdd = dev_get_drvdata(dev);
 461         struct watchdog_core_data *wd_data = wdd->wd_data;
 462         unsigned int status;
 463
 464         mutex_lock(&wd_data->lock);
 465         status = watchdog_get_status(wdd);
 466         mutex_unlock(&wd_data->lock);
 467
 468         return sprintf(buf, "0x%x\n", status);
 469 }
 470 static DEVICE_ATTR_RO(status);
 471
 472 static ssize_t bootstatus_show(struct device *dev,
 473                                 struct device_attribute *attr, char *buf)
 474 {
 475         struct watchdog_device *wdd = dev_get_drvdata(dev);
 476
 477         return sprintf(buf, "%u\n", wdd->bootstatus);
 478 }
 479 static DEVICE_ATTR_RO(bootstatus);
 480
 481 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
 482                                 char *buf)
 483 {
 484         struct watchdog_device *wdd = dev_get_drvdata(dev);
 485         struct watchdog_core_data *wd_data = wdd->wd_data;
 486         ssize_t status;
 487         unsigned int val;
 488
 489         mutex_lock(&wd_data->lock);
 490         status = watchdog_get_timeleft(wdd, &val);
 491         mutex_unlock(&wd_data->lock);
 492         if (!status)
 493                 status = sprintf(buf, "%u\n", val);
 494
 495         return status;
 496 }
 497 static DEVICE_ATTR_RO(timeleft);
 498
 499 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
 500                                 char *buf)
 501 {
 502         struct watchdog_device *wdd = dev_get_drvdata(dev);
 503
 504         return sprintf(buf, "%u\n", wdd->timeout);
 505 }
 506 static DEVICE_ATTR_RO(timeout);
 507
 508 static ssize_t pretimeout_show(struct device *dev,
 509                                struct device_attribute *attr, char *buf)
 510 {
 511         struct watchdog_device *wdd = dev_get_drvdata(dev);
 512
 513         return sprintf(buf, "%u\n", wdd->pretimeout);
 514 }
 515 static DEVICE_ATTR_RO(pretimeout);
 516
 517 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
 518                                 char *buf)
 519 {
 520         struct watchdog_device *wdd = dev_get_drvdata(dev);
 521
 522         return sprintf(buf, "%s\n", wdd->info->identity);
 523 }
 524 static DEVICE_ATTR_RO(identity);
 525
 526 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 527                                 char *buf)
 528 {
 529         struct watchdog_device *wdd = dev_get_drvdata(dev);
 530
 531         if (watchdog_active(wdd))
 532                 return sprintf(buf, "active\n");
 533
 534         return sprintf(buf, "inactive\n");
 535 }
 536 static DEVICE_ATTR_RO(state);
 537
 538 static ssize_t pretimeout_available_governors_show(struct device *dev,
 539                                    struct device_attribute *attr, char *buf)
 540 {
 541         return watchdog_pretimeout_available_governors_get(buf);
 542 }
 543 static DEVICE_ATTR_RO(pretimeout_available_governors);
 544
 545 static ssize_t pretimeout_governor_show(struct device *dev,
 546                                         struct device_attribute *attr,
 547                                         char *buf)
 548 {
 549         struct watchdog_device *wdd = dev_get_drvdata(dev);
 550
 551         return watchdog_pretimeout_governor_get(wdd, buf);
 552 }
 553
 554 static ssize_t pretimeout_governor_store(struct device *dev,
 555                                          struct device_attribute *attr,
 556                                          const char *buf, size_t count)
 557 {
 558         struct watchdog_device *wdd = dev_get_drvdata(dev);
 559         int ret = watchdog_pretimeout_governor_set(wdd, buf);
 560
 561         if (!ret)
 562                 ret = count;
 563
 564         return ret;
 565 }
 566 static DEVICE_ATTR_RW(pretimeout_governor);
 567
 568 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
 569                                 int n)
 570 {
 571         struct device *dev = container_of(kobj, struct device, kobj);
 572         struct watchdog_device *wdd = dev_get_drvdata(dev);
 573         umode_t mode = attr->mode;
 574
 575         if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
 576                 mode = 0;
 577         else if (attr == &dev_attr_pretimeout.attr &&
 578                  !(wdd->info->options & WDIOF_PRETIMEOUT))
 579                 mode = 0;
 580         else if ((attr == &dev_attr_pretimeout_governor.attr ||
 581                   attr == &dev_attr_pretimeout_available_governors.attr) &&
 582                  (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
 583                   !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
 584                 mode = 0;
 585
 586         return mode;
 587 }
 588 static struct attribute *wdt_attrs[] = {
 589         &dev_attr_state.attr,
 590         &dev_attr_identity.attr,
 591         &dev_attr_timeout.attr,
 592         &dev_attr_pretimeout.attr,
 593         &dev_attr_timeleft.attr,
 594         &dev_attr_bootstatus.attr,
 595         &dev_attr_status.attr,
 596         &dev_attr_nowayout.attr,
 597         &dev_attr_pretimeout_governor.attr,
 598         &dev_attr_pretimeout_available_governors.attr,
 599         NULL,
 600 };
 601
 602 static const struct attribute_group wdt_group = {
 603         .attrs = wdt_attrs,
 604         .is_visible = wdt_is_visible,
 605 };
 606 __ATTRIBUTE_GROUPS(wdt);
 607 #else
 608 #define wdt_groups      NULL
 609 #endif
 610
 611 /*
 612  *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 613  *      @wdd: the watchdog device to do the ioctl on
 614  *      @cmd: watchdog command
 615  *      @arg: argument pointer
 616  *
 617  *      The caller must hold wd_data->lock.
 618  */
 619
 620 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
 621                                                         unsigned long arg)
 622 {
 623         if (!wdd->ops->ioctl)
 624                 return -ENOIOCTLCMD;
 625
 626         return wdd->ops->ioctl(wdd, cmd, arg);
 627 }
 628
 629 /*
 630  *      watchdog_write: writes to the watchdog.
 631  *      @file: file from VFS
 632  *      @data: user address of data
 633  *      @len: length of data
 634  *      @ppos: pointer to the file offset
 635  *
 636  *      A write to a watchdog device is defined as a keepalive ping.
 637  *      Writing the magic 'V' sequence allows the next close to turn
 638  *      off the watchdog (if 'nowayout' is not set).
 639  */
 640
 641 static ssize_t watchdog_write(struct file *file, const char __user *data,
 642                                                 size_t len, loff_t *ppos)
 643 {
 644         struct watchdog_core_data *wd_data = file->private_data;
 645         struct watchdog_device *wdd;
 646         int err;
 647         size_t i;
 648         char c;
 649
 650         if (len == 0)
 651                 return 0;
 652
 653         /*
 654          * Note: just in case someone wrote the magic character
 655          * five months ago...
 656          */
 657         clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 658
 659         /* scan to see whether or not we got the magic character */
 660         for (i = 0; i != len; i++) {
 661                 if (get_user(c, data + i))
 662                         return -EFAULT;
 663                 if (c == 'V')
 664                         set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 665         }
 666
 667         /* someone wrote to us, so we send the watchdog a keepalive ping */
 668
 669         err = -ENODEV;
 670         mutex_lock(&wd_data->lock);
 671         wdd = wd_data->wdd;
 672         if (wdd)
 673                 err = watchdog_ping(wdd);
 674         mutex_unlock(&wd_data->lock);
 675
 676         if (err < 0)
 677                 return err;
 678
 679         return len;
 680 }
 681
 682 /*
 683  *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 684  *      @file: file handle to the device
 685  *      @cmd: watchdog command
 686  *      @arg: argument pointer
 687  *
 688  *      The watchdog API defines a common set of functions for all watchdogs
 689  *      according to their available features.
 690  */
 691
 692 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 693                                                         unsigned long arg)
 694 {
 695         struct watchdog_core_data *wd_data = file->private_data;
 696         void __user *argp = (void __user *)arg;
 697         struct watchdog_device *wdd;
 698         int __user *p = argp;
 699         unsigned int val;
 700         int err;
 701
 702         mutex_lock(&wd_data->lock);
 703
 704         wdd = wd_data->wdd;
 705         if (!wdd) {
 706                 err = -ENODEV;
 707                 goto out_ioctl;
 708         }
 709
 710         err = watchdog_ioctl_op(wdd, cmd, arg);
 711         if (err != -ENOIOCTLCMD)
 712                 goto out_ioctl;
 713
 714         switch (cmd) {
 715         case WDIOC_GETSUPPORT:
 716                 err = copy_to_user(argp, wdd->info,
 717                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
 718                 break;
 719         case WDIOC_GETSTATUS:
 720                 val = watchdog_get_status(wdd);
 721                 err = put_user(val, p);
 722                 break;
 723         case WDIOC_GETBOOTSTATUS:
 724                 err = put_user(wdd->bootstatus, p);
 725                 break;
 726         case WDIOC_SETOPTIONS:
 727                 if (get_user(val, p)) {
 728                         err = -EFAULT;
 729                         break;
 730                 }
 731                 if (val & WDIOS_DISABLECARD) {
 732                         err = watchdog_stop(wdd);
 733                         if (err < 0)
 734                                 break;
 735                 }
 736                 if (val & WDIOS_ENABLECARD)
 737                         err = watchdog_start(wdd);
 738                 break;
 739         case WDIOC_KEEPALIVE:
 740                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
 741                         err = -EOPNOTSUPP;
 742                         break;
 743                 }
 744                 err = watchdog_ping(wdd);
 745                 break;
 746         case WDIOC_SETTIMEOUT:
 747                 if (get_user(val, p)) {
 748                         err = -EFAULT;
 749                         break;
 750                 }
 751                 err = watchdog_set_timeout(wdd, val);
 752                 if (err < 0)
 753                         break;
 754                 /* If the watchdog is active then we send a keepalive ping
 755                  * to make sure that the watchdog keep's running (and if
 756                  * possible that it takes the new timeout) */
 757                 err = watchdog_ping(wdd);
 758                 if (err < 0)
 759                         break;
 760                 /* fall through */
 761         case WDIOC_GETTIMEOUT:
 762                 /* timeout == 0 means that we don't know the timeout */
 763                 if (wdd->timeout == 0) {
 764                         err = -EOPNOTSUPP;
 765                         break;
 766                 }
 767                 err = put_user(wdd->timeout, p);
 768                 break;
 769         case WDIOC_GETTIMELEFT:
 770                 err = watchdog_get_timeleft(wdd, &val);
 771                 if (err < 0)
 772                         break;
 773                 err = put_user(val, p);
 774                 break;
 775         case WDIOC_SETPRETIMEOUT:
 776                 if (get_user(val, p)) {
 777                         err = -EFAULT;
 778                         break;
 779                 }
 780                 err = watchdog_set_pretimeout(wdd, val);
 781                 break;
 782         case WDIOC_GETPRETIMEOUT:
 783                 err = put_user(wdd->pretimeout, p);
 784                 break;
 785         default:
 786                 err = -ENOTTY;
 787                 break;
 788         }
 789
 790 out_ioctl:
 791         mutex_unlock(&wd_data->lock);
 792         return err;
 793 }
 794
 795 /*
 796  *      watchdog_open: open the /dev/watchdog* devices.
 797  *      @inode: inode of device
 798  *      @file: file handle to device
 799  *
 800  *      When the /dev/watchdog* device gets opened, we start the watchdog.
 801  *      Watch out: the /dev/watchdog device is single open, so we make sure
 802  *      it can only be opened once.
 803  */
 804
 805 static int watchdog_open(struct inode *inode, struct file *file)
 806 {
 807         struct watchdog_core_data *wd_data;
 808         struct watchdog_device *wdd;
 809         bool hw_running;
 810         int err;
 811
 812         /* Get the corresponding watchdog device */
 813         if (imajor(inode) == MISC_MAJOR)
 814                 wd_data = old_wd_data;
 815         else
 816                 wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
 817                                        cdev);
 818
 819         /* the watchdog is single open! */
 820         if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
 821                 return -EBUSY;
 822
 823         wdd = wd_data->wdd;
 824
 825         /*
 826          * If the /dev/watchdog device is open, we don't want the module
 827          * to be unloaded.
 828          */
 829         hw_running = watchdog_hw_running(wdd);
 830         if (!hw_running && !try_module_get(wdd->ops->owner)) {
 831                 err = -EBUSY;
 832                 goto out_clear;
 833         }
 834
 835         err = watchdog_start(wdd);
 836         if (err < 0)
 837                 goto out_mod;
 838
 839         file->private_data = wd_data;
 840
 841         if (!hw_running)
 842                 get_device(&wd_data->dev);
 843
 844         /*
 845          * open_timeout only applies for the first open from
 846          * userspace. Set open_deadline to infinity so that the kernel
 847          * will take care of an always-running hardware watchdog in
 848          * case the device gets magic-closed or WDIOS_DISABLECARD is
 849          * applied.
 850          */
 851         wd_data->open_deadline = KTIME_MAX;
 852
 853         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 854         return stream_open(inode, file);
 855
 856 out_mod:
 857         module_put(wd_data->wdd->ops->owner);
 858 out_clear:
 859         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 860         return err;
 861 }
 862
 863 static void watchdog_core_data_release(struct device *dev)
 864 {
 865         struct watchdog_core_data *wd_data;
 866
 867         wd_data = container_of(dev, struct watchdog_core_data, dev);
 868
 869         kfree(wd_data);
 870 }
 871
 872 /*
 873  *      watchdog_release: release the watchdog device.
 874  *      @inode: inode of device
 875  *      @file: file handle to device
 876  *
 877  *      This is the code for when /dev/watchdog gets closed. We will only
 878  *      stop the watchdog when we have received the magic char (and nowayout
 879  *      was not set), else the watchdog will keep running.
 880  */
 881
 882 static int watchdog_release(struct inode *inode, struct file *file)
 883 {
 884         struct watchdog_core_data *wd_data = file->private_data;
 885         struct watchdog_device *wdd;
 886         int err = -EBUSY;
 887         bool running;
 888
 889         mutex_lock(&wd_data->lock);
 890
 891         wdd = wd_data->wdd;
 892         if (!wdd)
 893                 goto done;
 894
 895         /*
 896          * We only stop the watchdog if we received the magic character
 897          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 898          * watchdog_stop will fail.
 899          */
 900         if (!test_bit(WDOG_ACTIVE, &wdd->status))
 901                 err = 0;
 902         else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
 903                  !(wdd->info->options & WDIOF_MAGICCLOSE))
 904                 err = watchdog_stop(wdd);
 905
 906         /* If the watchdog was not stopped, send a keepalive ping */
 907         if (err < 0) {
 908                 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
 909                 watchdog_ping(wdd);
 910         }
 911
 912         watchdog_update_worker(wdd);
 913
 914         /* make sure that /dev/watchdog can be re-opened */
 915         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 916
 917 done:
 918         running = wdd && watchdog_hw_running(wdd);
 919         mutex_unlock(&wd_data->lock);
 920         /*
 921          * Allow the owner module to be unloaded again unless the watchdog
 922          * is still running. If the watchdog is still running, it can not
 923          * be stopped, and its driver must not be unloaded.
 924          */
 925         if (!running) {
 926                 module_put(wd_data->cdev.owner);
 927                 put_device(&wd_data->dev);
 928         }
 929         return 0;
 930 }
 931
 932 static const struct file_operations watchdog_fops = {
 933         .owner          = THIS_MODULE,
 934         .write          = watchdog_write,
 935         .unlocked_ioctl = watchdog_ioctl,
 936         .open           = watchdog_open,
 937         .release        = watchdog_release,
 938 };
 939
 940 static struct miscdevice watchdog_miscdev = {
 941         .minor          = WATCHDOG_MINOR,
 942         .name           = "watchdog",
 943         .fops           = &watchdog_fops,
 944 };
 945
 946 static struct class watchdog_class = {
 947         .name =         "watchdog",
 948         .owner =        THIS_MODULE,
 949         .dev_groups =   wdt_groups,
 950 };
 951
 952 /*
 953  *      watchdog_cdev_register: register watchdog character device
 954  *      @wdd: watchdog device
 955  *
 956  *      Register a watchdog character device including handling the legacy
 957  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 958  *      thus we set it up like that.
 959  */
 960
 961 static int watchdog_cdev_register(struct watchdog_device *wdd)
 962 {
 963         struct watchdog_core_data *wd_data;
 964         int err;
 965
 966         wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
 967         if (!wd_data)
 968                 return -ENOMEM;
 969         mutex_init(&wd_data->lock);
 970
 971         wd_data->wdd = wdd;
 972         wdd->wd_data = wd_data;
 973
 974         if (IS_ERR_OR_NULL(watchdog_kworker)) {
 975                 kfree(wd_data);
 976                 return -ENODEV;
 977         }
 978
 979         device_initialize(&wd_data->dev);
 980         wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
 981         wd_data->dev.class = &watchdog_class;
 982         wd_data->dev.parent = wdd->parent;
 983         wd_data->dev.groups = wdd->groups;
 984         wd_data->dev.release = watchdog_core_data_release;
 985         dev_set_drvdata(&wd_data->dev, wdd);
 986         dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
 987
 988         kthread_init_work(&wd_data->work, watchdog_ping_work);
 989         hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
 990         wd_data->timer.function = watchdog_timer_expired;
 991
 992         if (wdd->id == 0) {
 993                 old_wd_data = wd_data;
 994                 watchdog_miscdev.parent = wdd->parent;
 995                 err = misc_register(&watchdog_miscdev);
 996                 if (err != 0) {
 997                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
 998                                 wdd->info->identity, WATCHDOG_MINOR, err);
 999                         if (err == -EBUSY)
1000                                 pr_err("%s: a legacy watchdog module is probably present.\n",
1001                                         wdd->info->identity);
1002                         old_wd_data = NULL;
1003                         put_device(&wd_data->dev);
1004                         return err;
1005                 }
1006         }
1007
1008         /* Fill in the data structures */
1009         cdev_init(&wd_data->cdev, &watchdog_fops);
1010
1011         /* Add the device */
1012         err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1013         if (err) {
1014                 pr_err("watchdog%d unable to add device %d:%d\n",
1015                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
1016                 if (wdd->id == 0) {
1017                         misc_deregister(&watchdog_miscdev);
1018                         old_wd_data = NULL;
1019                         put_device(&wd_data->dev);
1020                 }
1021                 return err;
1022         }
1023
1024         wd_data->cdev.owner = wdd->ops->owner;
1025
1026         /* Record time of most recent heartbeat as 'just before now'. */
1027         wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1028         watchdog_set_open_deadline(wd_data);
1029
1030         /*
1031          * If the watchdog is running, prevent its driver from being unloaded,
1032          * and schedule an immediate ping.
1033          */
1034         if (watchdog_hw_running(wdd)) {
1035                 __module_get(wdd->ops->owner);
1036                 get_device(&wd_data->dev);
1037                 if (handle_boot_enabled)
1038                         hrtimer_start(&wd_data->timer, 0,
1039                                       HRTIMER_MODE_REL_HARD);
1040                 else
1041                         pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1042                                 wdd->id);
1043         }
1044
1045         return 0;
1046 }
1047
1048 /*
1049  *      watchdog_cdev_unregister: unregister watchdog character device
1050  *      @watchdog: watchdog device
1051  *
1052  *      Unregister watchdog character device and if needed the legacy
1053  *      /dev/watchdog device.
1054  */
1055
1056 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1057 {
1058         struct watchdog_core_data *wd_data = wdd->wd_data;
1059
1060         cdev_device_del(&wd_data->cdev, &wd_data->dev);
1061         if (wdd->id == 0) {
1062                 misc_deregister(&watchdog_miscdev);
1063                 old_wd_data = NULL;
1064         }
1065
1066         if (watchdog_active(wdd) &&
1067             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1068                 watchdog_stop(wdd);
1069         }
1070
1071         mutex_lock(&wd_data->lock);
1072         wd_data->wdd = NULL;
1073         wdd->wd_data = NULL;
1074         mutex_unlock(&wd_data->lock);
1075
1076         hrtimer_cancel(&wd_data->timer);
1077         kthread_cancel_work_sync(&wd_data->work);
1078
1079         put_device(&wd_data->dev);
1080 }
1081
1082 /*
1083  *      watchdog_dev_register: register a watchdog device
1084  *      @wdd: watchdog device
1085  *
1086  *      Register a watchdog device including handling the legacy
1087  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1088  *      thus we set it up like that.
1089  */
1090
1091 int watchdog_dev_register(struct watchdog_device *wdd)
1092 {
1093         int ret;
1094
1095         ret = watchdog_cdev_register(wdd);
1096         if (ret)
1097                 return ret;
1098
1099         ret = watchdog_register_pretimeout(wdd);
1100         if (ret)
1101                 watchdog_cdev_unregister(wdd);
1102
1103         return ret;
1104 }
1105
1106 /*
1107  *      watchdog_dev_unregister: unregister a watchdog device
1108  *      @watchdog: watchdog device
1109  *
1110  *      Unregister watchdog device and if needed the legacy
1111  *      /dev/watchdog device.
1112  */
1113
1114 void watchdog_dev_unregister(struct watchdog_device *wdd)
1115 {
1116         watchdog_unregister_pretimeout(wdd);
1117         watchdog_cdev_unregister(wdd);
1118 }
1119
1120 /*
1121  *      watchdog_dev_init: init dev part of watchdog core
1122  *
1123  *      Allocate a range of chardev nodes to use for watchdog devices
1124  */
1125
1126 int __init watchdog_dev_init(void)
1127 {
1128         int err;
1129         struct sched_param param = {.sched_priority = MAX_RT_PRIO - 1,};
1130
1131         watchdog_kworker = kthread_create_worker(0, "watchdogd");
1132         if (IS_ERR(watchdog_kworker)) {
1133                 pr_err("Failed to create watchdog kworker\n");
1134                 return PTR_ERR(watchdog_kworker);
1135         }
1136         sched_setscheduler(watchdog_kworker->task, SCHED_FIFO, &param);
1137
1138         err = class_register(&watchdog_class);
1139         if (err < 0) {
1140                 pr_err("couldn't register class\n");
1141                 goto err_register;
1142         }
1143
1144         err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1145         if (err < 0) {
1146                 pr_err("watchdog: unable to allocate char dev region\n");
1147                 goto err_alloc;
1148         }
1149
1150         return 0;
1151
1152 err_alloc:
1153         class_unregister(&watchdog_class);
1154 err_register:
1155         kthread_destroy_worker(watchdog_kworker);
1156         return err;
1157 }
1158
1159 /*
1160  *      watchdog_dev_exit: exit dev part of watchdog core
1161  *
1162  *      Release the range of chardev nodes used for watchdog devices
1163  */
1164
1165 void __exit watchdog_dev_exit(void)
1166 {
1167         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1168         class_unregister(&watchdog_class);
1169         kthread_destroy_worker(watchdog_kworker);
1170 }
1171
1172 module_param(handle_boot_enabled, bool, 0444);
1173 MODULE_PARM_DESC(handle_boot_enabled,
1174         "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1175         __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1176
1177 module_param(open_timeout, uint, 0644);
1178 MODULE_PARM_DESC(open_timeout,
1179         "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1180         __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");