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/reboot.h>       /* For reboot notifier */
  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 <uapi/linux/sched/types.h>     /* For struct sched_param */
  48
  49 #include "watchdog_core.h"
  50 #include "watchdog_pretimeout.h"
  51
  52 /*
  53  * struct watchdog_core_data - watchdog core internal data
  54  * @dev:        The watchdog's internal device
  55  * @cdev:       The watchdog's Character device.
  56  * @wdd:        Pointer to watchdog device.
  57  * @lock:       Lock for watchdog core.
  58  * @status:     Watchdog core internal status bits.
  59  */
  60 struct watchdog_core_data {
  61         struct device dev;
  62         struct cdev cdev;
  63         struct watchdog_device *wdd;
  64         struct mutex lock;
  65         ktime_t last_keepalive;
  66         ktime_t last_hw_keepalive;
  67         ktime_t open_deadline;
  68         struct hrtimer timer;
  69         struct kthread_work work;
  70         unsigned long status;           /* Internal status bits */
  71 #define _WDOG_DEV_OPEN          0       /* Opened ? */
  72 #define _WDOG_ALLOW_RELEASE     1       /* Did we receive the magic char ? */
  73 #define _WDOG_KEEPALIVE         2       /* Did we receive a keepalive ? */
  74 };
  75
  76 /* the dev_t structure to store the dynamically allocated watchdog devices */
  77 static dev_t watchdog_devt;
  78 /* Reference to watchdog device behind /dev/watchdog */
  79 static struct watchdog_core_data *old_wd_data;
  80
  81 static struct kthread_worker *watchdog_kworker;
  82
  83 static bool handle_boot_enabled =
  84         IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
  85
  86 static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
  87
  88 static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
  89 {
  90         return ktime_after(ktime_get(), data->open_deadline);
  91 }
  92
  93 static void watchdog_set_open_deadline(struct watchdog_core_data *data)
  94 {
  95         data->open_deadline = open_timeout ?
  96                 ktime_get() + ktime_set(open_timeout, 0) : KTIME_MAX;
  97 }
  98
  99 static inline bool watchdog_need_worker(struct watchdog_device *wdd)
 100 {
 101         /* All variables in milli-seconds */
 102         unsigned int hm = wdd->max_hw_heartbeat_ms;
 103         unsigned int t = wdd->timeout * 1000;
 104
 105         /*
 106          * A worker to generate heartbeat requests is needed if all of the
 107          * following conditions are true.
 108          * - Userspace activated the watchdog.
 109          * - The driver provided a value for the maximum hardware timeout, and
 110          *   thus is aware that the framework supports generating heartbeat
 111          *   requests.
 112          * - Userspace requests a longer timeout than the hardware can handle.
 113          *
 114          * Alternatively, if userspace has not opened the watchdog
 115          * device, we take care of feeding the watchdog if it is
 116          * running.
 117          */
 118         return (hm && watchdog_active(wdd) && t > hm) ||
 119                 (t && !watchdog_active(wdd) && watchdog_hw_running(wdd));
 120 }
 121
 122 static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
 123 {
 124         struct watchdog_core_data *wd_data = wdd->wd_data;
 125         unsigned int timeout_ms = wdd->timeout * 1000;
 126         ktime_t keepalive_interval;
 127         ktime_t last_heartbeat, latest_heartbeat;
 128         ktime_t virt_timeout;
 129         unsigned int hw_heartbeat_ms;
 130
 131         if (watchdog_active(wdd))
 132                 virt_timeout = ktime_add(wd_data->last_keepalive,
 133                                          ms_to_ktime(timeout_ms));
 134         else
 135                 virt_timeout = wd_data->open_deadline;
 136
 137         hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms);
 138         keepalive_interval = ms_to_ktime(hw_heartbeat_ms / 2);
 139
 140         /*
 141          * To ensure that the watchdog times out wdd->timeout seconds
 142          * after the most recent ping from userspace, the last
 143          * worker ping has to come in hw_heartbeat_ms before this timeout.
 144          */
 145         last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms));
 146         latest_heartbeat = ktime_sub(last_heartbeat, ktime_get());
 147         if (ktime_before(latest_heartbeat, keepalive_interval))
 148                 return latest_heartbeat;
 149         return keepalive_interval;
 150 }
 151
 152 static inline void watchdog_update_worker(struct watchdog_device *wdd)
 153 {
 154         struct watchdog_core_data *wd_data = wdd->wd_data;
 155
 156         if (watchdog_need_worker(wdd)) {
 157                 ktime_t t = watchdog_next_keepalive(wdd);
 158
 159                 if (t > 0)
 160                         hrtimer_start(&wd_data->timer, t, HRTIMER_MODE_REL);
 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);
 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                 watchdog_update_worker(wdd);
 286         }
 287
 288         return err;
 289 }
 290
 291 /*
 292  *      watchdog_stop: wrapper to stop the watchdog.
 293  *      @wdd: the watchdog device to stop
 294  *
 295  *      The caller must hold wd_data->lock.
 296  *
 297  *      Stop the watchdog if it is still active and unmark it active.
 298  *      This function returns zero on success or a negative errno code for
 299  *      failure.
 300  *      If the 'nowayout' feature was set, the watchdog cannot be stopped.
 301  */
 302
 303 static int watchdog_stop(struct watchdog_device *wdd)
 304 {
 305         int err = 0;
 306
 307         if (!watchdog_active(wdd))
 308                 return 0;
 309
 310         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
 311                 pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
 312                         wdd->id);
 313                 return -EBUSY;
 314         }
 315
 316         if (wdd->ops->stop) {
 317                 clear_bit(WDOG_HW_RUNNING, &wdd->status);
 318                 err = wdd->ops->stop(wdd);
 319         } else {
 320                 set_bit(WDOG_HW_RUNNING, &wdd->status);
 321         }
 322
 323         if (err == 0) {
 324                 clear_bit(WDOG_ACTIVE, &wdd->status);
 325                 watchdog_update_worker(wdd);
 326         }
 327
 328         return err;
 329 }
 330
 331 /*
 332  *      watchdog_get_status: wrapper to get the watchdog status
 333  *      @wdd: the watchdog device to get the status from
 334  *
 335  *      The caller must hold wd_data->lock.
 336  *
 337  *      Get the watchdog's status flags.
 338  */
 339
 340 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
 341 {
 342         struct watchdog_core_data *wd_data = wdd->wd_data;
 343         unsigned int status;
 344
 345         if (wdd->ops->status)
 346                 status = wdd->ops->status(wdd);
 347         else
 348                 status = wdd->bootstatus & (WDIOF_CARDRESET |
 349                                             WDIOF_OVERHEAT |
 350                                             WDIOF_FANFAULT |
 351                                             WDIOF_EXTERN1 |
 352                                             WDIOF_EXTERN2 |
 353                                             WDIOF_POWERUNDER |
 354                                             WDIOF_POWEROVER);
 355
 356         if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
 357                 status |= WDIOF_MAGICCLOSE;
 358
 359         if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
 360                 status |= WDIOF_KEEPALIVEPING;
 361
 362         return status;
 363 }
 364
 365 /*
 366  *      watchdog_set_timeout: set the watchdog timer timeout
 367  *      @wdd: the watchdog device to set the timeout for
 368  *      @timeout: timeout to set in seconds
 369  *
 370  *      The caller must hold wd_data->lock.
 371  */
 372
 373 static int watchdog_set_timeout(struct watchdog_device *wdd,
 374                                                         unsigned int timeout)
 375 {
 376         int err = 0;
 377
 378         if (!(wdd->info->options & WDIOF_SETTIMEOUT))
 379                 return -EOPNOTSUPP;
 380
 381         if (watchdog_timeout_invalid(wdd, timeout))
 382                 return -EINVAL;
 383
 384         if (wdd->ops->set_timeout) {
 385                 err = wdd->ops->set_timeout(wdd, timeout);
 386         } else {
 387                 wdd->timeout = timeout;
 388                 /* Disable pretimeout if it doesn't fit the new timeout */
 389                 if (wdd->pretimeout >= wdd->timeout)
 390                         wdd->pretimeout = 0;
 391         }
 392
 393         watchdog_update_worker(wdd);
 394
 395         return err;
 396 }
 397
 398 /*
 399  *      watchdog_set_pretimeout: set the watchdog timer pretimeout
 400  *      @wdd: the watchdog device to set the timeout for
 401  *      @timeout: pretimeout to set in seconds
 402  */
 403
 404 static int watchdog_set_pretimeout(struct watchdog_device *wdd,
 405                                    unsigned int timeout)
 406 {
 407         int err = 0;
 408
 409         if (!(wdd->info->options & WDIOF_PRETIMEOUT))
 410                 return -EOPNOTSUPP;
 411
 412         if (watchdog_pretimeout_invalid(wdd, timeout))
 413                 return -EINVAL;
 414
 415         if (wdd->ops->set_pretimeout)
 416                 err = wdd->ops->set_pretimeout(wdd, timeout);
 417         else
 418                 wdd->pretimeout = timeout;
 419
 420         return err;
 421 }
 422
 423 /*
 424  *      watchdog_get_timeleft: wrapper to get the time left before a reboot
 425  *      @wdd: the watchdog device to get the remaining time from
 426  *      @timeleft: the time that's left
 427  *
 428  *      The caller must hold wd_data->lock.
 429  *
 430  *      Get the time before a watchdog will reboot (if not pinged).
 431  */
 432
 433 static int watchdog_get_timeleft(struct watchdog_device *wdd,
 434                                                         unsigned int *timeleft)
 435 {
 436         *timeleft = 0;
 437
 438         if (!wdd->ops->get_timeleft)
 439                 return -EOPNOTSUPP;
 440
 441         *timeleft = wdd->ops->get_timeleft(wdd);
 442
 443         return 0;
 444 }
 445
 446 #ifdef CONFIG_WATCHDOG_SYSFS
 447 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
 448                                 char *buf)
 449 {
 450         struct watchdog_device *wdd = dev_get_drvdata(dev);
 451
 452         return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
 453 }
 454 static DEVICE_ATTR_RO(nowayout);
 455
 456 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
 457                                 char *buf)
 458 {
 459         struct watchdog_device *wdd = dev_get_drvdata(dev);
 460         struct watchdog_core_data *wd_data = wdd->wd_data;
 461         unsigned int status;
 462
 463         mutex_lock(&wd_data->lock);
 464         status = watchdog_get_status(wdd);
 465         mutex_unlock(&wd_data->lock);
 466
 467         return sprintf(buf, "0x%x\n", status);
 468 }
 469 static DEVICE_ATTR_RO(status);
 470
 471 static ssize_t bootstatus_show(struct device *dev,
 472                                 struct device_attribute *attr, char *buf)
 473 {
 474         struct watchdog_device *wdd = dev_get_drvdata(dev);
 475
 476         return sprintf(buf, "%u\n", wdd->bootstatus);
 477 }
 478 static DEVICE_ATTR_RO(bootstatus);
 479
 480 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
 481                                 char *buf)
 482 {
 483         struct watchdog_device *wdd = dev_get_drvdata(dev);
 484         struct watchdog_core_data *wd_data = wdd->wd_data;
 485         ssize_t status;
 486         unsigned int val;
 487
 488         mutex_lock(&wd_data->lock);
 489         status = watchdog_get_timeleft(wdd, &val);
 490         mutex_unlock(&wd_data->lock);
 491         if (!status)
 492                 status = sprintf(buf, "%u\n", val);
 493
 494         return status;
 495 }
 496 static DEVICE_ATTR_RO(timeleft);
 497
 498 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
 499                                 char *buf)
 500 {
 501         struct watchdog_device *wdd = dev_get_drvdata(dev);
 502
 503         return sprintf(buf, "%u\n", wdd->timeout);
 504 }
 505 static DEVICE_ATTR_RO(timeout);
 506
 507 static ssize_t pretimeout_show(struct device *dev,
 508                                struct device_attribute *attr, char *buf)
 509 {
 510         struct watchdog_device *wdd = dev_get_drvdata(dev);
 511
 512         return sprintf(buf, "%u\n", wdd->pretimeout);
 513 }
 514 static DEVICE_ATTR_RO(pretimeout);
 515
 516 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
 517                                 char *buf)
 518 {
 519         struct watchdog_device *wdd = dev_get_drvdata(dev);
 520
 521         return sprintf(buf, "%s\n", wdd->info->identity);
 522 }
 523 static DEVICE_ATTR_RO(identity);
 524
 525 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 526                                 char *buf)
 527 {
 528         struct watchdog_device *wdd = dev_get_drvdata(dev);
 529
 530         if (watchdog_active(wdd))
 531                 return sprintf(buf, "active\n");
 532
 533         return sprintf(buf, "inactive\n");
 534 }
 535 static DEVICE_ATTR_RO(state);
 536
 537 static ssize_t pretimeout_available_governors_show(struct device *dev,
 538                                    struct device_attribute *attr, char *buf)
 539 {
 540         return watchdog_pretimeout_available_governors_get(buf);
 541 }
 542 static DEVICE_ATTR_RO(pretimeout_available_governors);
 543
 544 static ssize_t pretimeout_governor_show(struct device *dev,
 545                                         struct device_attribute *attr,
 546                                         char *buf)
 547 {
 548         struct watchdog_device *wdd = dev_get_drvdata(dev);
 549
 550         return watchdog_pretimeout_governor_get(wdd, buf);
 551 }
 552
 553 static ssize_t pretimeout_governor_store(struct device *dev,
 554                                          struct device_attribute *attr,
 555                                          const char *buf, size_t count)
 556 {
 557         struct watchdog_device *wdd = dev_get_drvdata(dev);
 558         int ret = watchdog_pretimeout_governor_set(wdd, buf);
 559
 560         if (!ret)
 561                 ret = count;
 562
 563         return ret;
 564 }
 565 static DEVICE_ATTR_RW(pretimeout_governor);
 566
 567 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
 568                                 int n)
 569 {
 570         struct device *dev = container_of(kobj, struct device, kobj);
 571         struct watchdog_device *wdd = dev_get_drvdata(dev);
 572         umode_t mode = attr->mode;
 573
 574         if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
 575                 mode = 0;
 576         else if (attr == &dev_attr_pretimeout.attr &&
 577                  !(wdd->info->options & WDIOF_PRETIMEOUT))
 578                 mode = 0;
 579         else if ((attr == &dev_attr_pretimeout_governor.attr ||
 580                   attr == &dev_attr_pretimeout_available_governors.attr) &&
 581                  (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
 582                   !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
 583                 mode = 0;
 584
 585         return mode;
 586 }
 587 static struct attribute *wdt_attrs[] = {
 588         &dev_attr_state.attr,
 589         &dev_attr_identity.attr,
 590         &dev_attr_timeout.attr,
 591         &dev_attr_pretimeout.attr,
 592         &dev_attr_timeleft.attr,
 593         &dev_attr_bootstatus.attr,
 594         &dev_attr_status.attr,
 595         &dev_attr_nowayout.attr,
 596         &dev_attr_pretimeout_governor.attr,
 597         &dev_attr_pretimeout_available_governors.attr,
 598         NULL,
 599 };
 600
 601 static const struct attribute_group wdt_group = {
 602         .attrs = wdt_attrs,
 603         .is_visible = wdt_is_visible,
 604 };
 605 __ATTRIBUTE_GROUPS(wdt);
 606 #else
 607 #define wdt_groups      NULL
 608 #endif
 609
 610 /*
 611  *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 612  *      @wdd: the watchdog device to do the ioctl on
 613  *      @cmd: watchdog command
 614  *      @arg: argument pointer
 615  *
 616  *      The caller must hold wd_data->lock.
 617  */
 618
 619 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
 620                                                         unsigned long arg)
 621 {
 622         if (!wdd->ops->ioctl)
 623                 return -ENOIOCTLCMD;
 624
 625         return wdd->ops->ioctl(wdd, cmd, arg);
 626 }
 627
 628 /*
 629  *      watchdog_write: writes to the watchdog.
 630  *      @file: file from VFS
 631  *      @data: user address of data
 632  *      @len: length of data
 633  *      @ppos: pointer to the file offset
 634  *
 635  *      A write to a watchdog device is defined as a keepalive ping.
 636  *      Writing the magic 'V' sequence allows the next close to turn
 637  *      off the watchdog (if 'nowayout' is not set).
 638  */
 639
 640 static ssize_t watchdog_write(struct file *file, const char __user *data,
 641                                                 size_t len, loff_t *ppos)
 642 {
 643         struct watchdog_core_data *wd_data = file->private_data;
 644         struct watchdog_device *wdd;
 645         int err;
 646         size_t i;
 647         char c;
 648
 649         if (len == 0)
 650                 return 0;
 651
 652         /*
 653          * Note: just in case someone wrote the magic character
 654          * five months ago...
 655          */
 656         clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 657
 658         /* scan to see whether or not we got the magic character */
 659         for (i = 0; i != len; i++) {
 660                 if (get_user(c, data + i))
 661                         return -EFAULT;
 662                 if (c == 'V')
 663                         set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 664         }
 665
 666         /* someone wrote to us, so we send the watchdog a keepalive ping */
 667
 668         err = -ENODEV;
 669         mutex_lock(&wd_data->lock);
 670         wdd = wd_data->wdd;
 671         if (wdd)
 672                 err = watchdog_ping(wdd);
 673         mutex_unlock(&wd_data->lock);
 674
 675         if (err < 0)
 676                 return err;
 677
 678         return len;
 679 }
 680
 681 /*
 682  *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 683  *      @file: file handle to the device
 684  *      @cmd: watchdog command
 685  *      @arg: argument pointer
 686  *
 687  *      The watchdog API defines a common set of functions for all watchdogs
 688  *      according to their available features.
 689  */
 690
 691 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 692                                                         unsigned long arg)
 693 {
 694         struct watchdog_core_data *wd_data = file->private_data;
 695         void __user *argp = (void __user *)arg;
 696         struct watchdog_device *wdd;
 697         int __user *p = argp;
 698         unsigned int val;
 699         int err;
 700
 701         mutex_lock(&wd_data->lock);
 702
 703         wdd = wd_data->wdd;
 704         if (!wdd) {
 705                 err = -ENODEV;
 706                 goto out_ioctl;
 707         }
 708
 709         err = watchdog_ioctl_op(wdd, cmd, arg);
 710         if (err != -ENOIOCTLCMD)
 711                 goto out_ioctl;
 712
 713         switch (cmd) {
 714         case WDIOC_GETSUPPORT:
 715                 err = copy_to_user(argp, wdd->info,
 716                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
 717                 break;
 718         case WDIOC_GETSTATUS:
 719                 val = watchdog_get_status(wdd);
 720                 err = put_user(val, p);
 721                 break;
 722         case WDIOC_GETBOOTSTATUS:
 723                 err = put_user(wdd->bootstatus, p);
 724                 break;
 725         case WDIOC_SETOPTIONS:
 726                 if (get_user(val, p)) {
 727                         err = -EFAULT;
 728                         break;
 729                 }
 730                 if (val & WDIOS_DISABLECARD) {
 731                         err = watchdog_stop(wdd);
 732                         if (err < 0)
 733                                 break;
 734                 }
 735                 if (val & WDIOS_ENABLECARD)
 736                         err = watchdog_start(wdd);
 737                 break;
 738         case WDIOC_KEEPALIVE:
 739                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
 740                         err = -EOPNOTSUPP;
 741                         break;
 742                 }
 743                 err = watchdog_ping(wdd);
 744                 break;
 745         case WDIOC_SETTIMEOUT:
 746                 if (get_user(val, p)) {
 747                         err = -EFAULT;
 748                         break;
 749                 }
 750                 err = watchdog_set_timeout(wdd, val);
 751                 if (err < 0)
 752                         break;
 753                 /* If the watchdog is active then we send a keepalive ping
 754                  * to make sure that the watchdog keep's running (and if
 755                  * possible that it takes the new timeout) */
 756                 err = watchdog_ping(wdd);
 757                 if (err < 0)
 758                         break;
 759                 /* fall through */
 760         case WDIOC_GETTIMEOUT:
 761                 /* timeout == 0 means that we don't know the timeout */
 762                 if (wdd->timeout == 0) {
 763                         err = -EOPNOTSUPP;
 764                         break;
 765                 }
 766                 err = put_user(wdd->timeout, p);
 767                 break;
 768         case WDIOC_GETTIMELEFT:
 769                 err = watchdog_get_timeleft(wdd, &val);
 770                 if (err < 0)
 771                         break;
 772                 err = put_user(val, p);
 773                 break;
 774         case WDIOC_SETPRETIMEOUT:
 775                 if (get_user(val, p)) {
 776                         err = -EFAULT;
 777                         break;
 778                 }
 779                 err = watchdog_set_pretimeout(wdd, val);
 780                 break;
 781         case WDIOC_GETPRETIMEOUT:
 782                 err = put_user(wdd->pretimeout, p);
 783                 break;
 784         default:
 785                 err = -ENOTTY;
 786                 break;
 787         }
 788
 789 out_ioctl:
 790         mutex_unlock(&wd_data->lock);
 791         return err;
 792 }
 793
 794 /*
 795  *      watchdog_open: open the /dev/watchdog* devices.
 796  *      @inode: inode of device
 797  *      @file: file handle to device
 798  *
 799  *      When the /dev/watchdog* device gets opened, we start the watchdog.
 800  *      Watch out: the /dev/watchdog device is single open, so we make sure
 801  *      it can only be opened once.
 802  */
 803
 804 static int watchdog_open(struct inode *inode, struct file *file)
 805 {
 806         struct watchdog_core_data *wd_data;
 807         struct watchdog_device *wdd;
 808         bool hw_running;
 809         int err;
 810
 811         /* Get the corresponding watchdog device */
 812         if (imajor(inode) == MISC_MAJOR)
 813                 wd_data = old_wd_data;
 814         else
 815                 wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
 816                                        cdev);
 817
 818         /* the watchdog is single open! */
 819         if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
 820                 return -EBUSY;
 821
 822         wdd = wd_data->wdd;
 823
 824         /*
 825          * If the /dev/watchdog device is open, we don't want the module
 826          * to be unloaded.
 827          */
 828         hw_running = watchdog_hw_running(wdd);
 829         if (!hw_running && !try_module_get(wdd->ops->owner)) {
 830                 err = -EBUSY;
 831                 goto out_clear;
 832         }
 833
 834         err = watchdog_start(wdd);
 835         if (err < 0)
 836                 goto out_mod;
 837
 838         file->private_data = wd_data;
 839
 840         if (!hw_running)
 841                 get_device(&wd_data->dev);
 842
 843         /*
 844          * open_timeout only applies for the first open from
 845          * userspace. Set open_deadline to infinity so that the kernel
 846          * will take care of an always-running hardware watchdog in
 847          * case the device gets magic-closed or WDIOS_DISABLECARD is
 848          * applied.
 849          */
 850         wd_data->open_deadline = KTIME_MAX;
 851
 852         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 853         return stream_open(inode, file);
 854
 855 out_mod:
 856         module_put(wd_data->wdd->ops->owner);
 857 out_clear:
 858         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 859         return err;
 860 }
 861
 862 static void watchdog_core_data_release(struct device *dev)
 863 {
 864         struct watchdog_core_data *wd_data;
 865
 866         wd_data = container_of(dev, struct watchdog_core_data, dev);
 867
 868         kfree(wd_data);
 869 }
 870
 871 /*
 872  *      watchdog_release: release the watchdog device.
 873  *      @inode: inode of device
 874  *      @file: file handle to device
 875  *
 876  *      This is the code for when /dev/watchdog gets closed. We will only
 877  *      stop the watchdog when we have received the magic char (and nowayout
 878  *      was not set), else the watchdog will keep running.
 879  */
 880
 881 static int watchdog_release(struct inode *inode, struct file *file)
 882 {
 883         struct watchdog_core_data *wd_data = file->private_data;
 884         struct watchdog_device *wdd;
 885         int err = -EBUSY;
 886         bool running;
 887
 888         mutex_lock(&wd_data->lock);
 889
 890         wdd = wd_data->wdd;
 891         if (!wdd)
 892                 goto done;
 893
 894         /*
 895          * We only stop the watchdog if we received the magic character
 896          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 897          * watchdog_stop will fail.
 898          */
 899         if (!test_bit(WDOG_ACTIVE, &wdd->status))
 900                 err = 0;
 901         else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
 902                  !(wdd->info->options & WDIOF_MAGICCLOSE))
 903                 err = watchdog_stop(wdd);
 904
 905         /* If the watchdog was not stopped, send a keepalive ping */
 906         if (err < 0) {
 907                 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
 908                 watchdog_ping(wdd);
 909         }
 910
 911         watchdog_update_worker(wdd);
 912
 913         /* make sure that /dev/watchdog can be re-opened */
 914         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 915
 916 done:
 917         running = wdd && watchdog_hw_running(wdd);
 918         mutex_unlock(&wd_data->lock);
 919         /*
 920          * Allow the owner module to be unloaded again unless the watchdog
 921          * is still running. If the watchdog is still running, it can not
 922          * be stopped, and its driver must not be unloaded.
 923          */
 924         if (!running) {
 925                 module_put(wd_data->cdev.owner);
 926                 put_device(&wd_data->dev);
 927         }
 928         return 0;
 929 }
 930
 931 static const struct file_operations watchdog_fops = {
 932         .owner          = THIS_MODULE,
 933         .write          = watchdog_write,
 934         .unlocked_ioctl = watchdog_ioctl,
 935         .open           = watchdog_open,
 936         .release        = watchdog_release,
 937 };
 938
 939 static struct miscdevice watchdog_miscdev = {
 940         .minor          = WATCHDOG_MINOR,
 941         .name           = "watchdog",
 942         .fops           = &watchdog_fops,
 943 };
 944
 945 static struct class watchdog_class = {
 946         .name =         "watchdog",
 947         .owner =        THIS_MODULE,
 948         .dev_groups =   wdt_groups,
 949 };
 950
 951 /*
 952  *      watchdog_cdev_register: register watchdog character device
 953  *      @wdd: watchdog device
 954  *
 955  *      Register a watchdog character device including handling the legacy
 956  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 957  *      thus we set it up like that.
 958  */
 959
 960 static int watchdog_cdev_register(struct watchdog_device *wdd)
 961 {
 962         struct watchdog_core_data *wd_data;
 963         int err;
 964
 965         wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
 966         if (!wd_data)
 967                 return -ENOMEM;
 968         mutex_init(&wd_data->lock);
 969
 970         wd_data->wdd = wdd;
 971         wdd->wd_data = wd_data;
 972
 973         if (IS_ERR_OR_NULL(watchdog_kworker))
 974                 return -ENODEV;
 975
 976         kthread_init_work(&wd_data->work, watchdog_ping_work);
 977         hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 978         wd_data->timer.function = watchdog_timer_expired;
 979
 980         if (wdd->id == 0) {
 981                 old_wd_data = wd_data;
 982                 watchdog_miscdev.parent = wdd->parent;
 983                 err = misc_register(&watchdog_miscdev);
 984                 if (err != 0) {
 985                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
 986                                 wdd->info->identity, WATCHDOG_MINOR, err);
 987                         if (err == -EBUSY)
 988                                 pr_err("%s: a legacy watchdog module is probably present.\n",
 989                                         wdd->info->identity);
 990                         old_wd_data = NULL;
 991                         kfree(wd_data);
 992                         return err;
 993                 }
 994         }
 995
 996         device_initialize(&wd_data->dev);
 997         wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
 998         wd_data->dev.class = &watchdog_class;
 999         wd_data->dev.parent = wdd->parent;
1000         wd_data->dev.groups = wdd->groups;
1001         wd_data->dev.release = watchdog_core_data_release;
1002         dev_set_drvdata(&wd_data->dev, wdd);
1003         dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
1004
1005         /* Fill in the data structures */
1006         cdev_init(&wd_data->cdev, &watchdog_fops);
1007
1008         /* Add the device */
1009         err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1010         if (err) {
1011                 pr_err("watchdog%d unable to add device %d:%d\n",
1012                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
1013                 if (wdd->id == 0) {
1014                         misc_deregister(&watchdog_miscdev);
1015                         old_wd_data = NULL;
1016                         put_device(&wd_data->dev);
1017                 }
1018                 return err;
1019         }
1020
1021         wd_data->cdev.owner = wdd->ops->owner;
1022
1023         /* Record time of most recent heartbeat as 'just before now'. */
1024         wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1025         watchdog_set_open_deadline(wd_data);
1026
1027         /*
1028          * If the watchdog is running, prevent its driver from being unloaded,
1029          * and schedule an immediate ping.
1030          */
1031         if (watchdog_hw_running(wdd)) {
1032                 __module_get(wdd->ops->owner);
1033                 get_device(&wd_data->dev);
1034                 if (handle_boot_enabled)
1035                         hrtimer_start(&wd_data->timer, 0, HRTIMER_MODE_REL);
1036                 else
1037                         pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1038                                 wdd->id);
1039         }
1040
1041         return 0;
1042 }
1043
1044 /*
1045  *      watchdog_cdev_unregister: unregister watchdog character device
1046  *      @watchdog: watchdog device
1047  *
1048  *      Unregister watchdog character device and if needed the legacy
1049  *      /dev/watchdog device.
1050  */
1051
1052 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1053 {
1054         struct watchdog_core_data *wd_data = wdd->wd_data;
1055
1056         cdev_device_del(&wd_data->cdev, &wd_data->dev);
1057         if (wdd->id == 0) {
1058                 misc_deregister(&watchdog_miscdev);
1059                 old_wd_data = NULL;
1060         }
1061
1062         if (watchdog_active(wdd) &&
1063             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1064                 watchdog_stop(wdd);
1065         }
1066
1067         mutex_lock(&wd_data->lock);
1068         wd_data->wdd = NULL;
1069         wdd->wd_data = NULL;
1070         mutex_unlock(&wd_data->lock);
1071
1072         hrtimer_cancel(&wd_data->timer);
1073         kthread_cancel_work_sync(&wd_data->work);
1074
1075         put_device(&wd_data->dev);
1076 }
1077
1078 static int watchdog_reboot_notifier(struct notifier_block *nb,
1079                                     unsigned long code, void *data)
1080 {
1081         struct watchdog_device *wdd;
1082
1083         wdd = container_of(nb, struct watchdog_device, reboot_nb);
1084         if (code == SYS_DOWN || code == SYS_HALT) {
1085                 if (watchdog_active(wdd)) {
1086                         int ret;
1087
1088                         ret = wdd->ops->stop(wdd);
1089                         if (ret)
1090                                 return NOTIFY_BAD;
1091                 }
1092         }
1093
1094         return NOTIFY_DONE;
1095 }
1096
1097 /*
1098  *      watchdog_dev_register: register a watchdog device
1099  *      @wdd: watchdog device
1100  *
1101  *      Register a watchdog device including handling the legacy
1102  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1103  *      thus we set it up like that.
1104  */
1105
1106 int watchdog_dev_register(struct watchdog_device *wdd)
1107 {
1108         int ret;
1109
1110         ret = watchdog_cdev_register(wdd);
1111         if (ret)
1112                 return ret;
1113
1114         ret = watchdog_register_pretimeout(wdd);
1115         if (ret) {
1116                 watchdog_cdev_unregister(wdd);
1117                 return ret;
1118         }
1119
1120         if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
1121                 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
1122
1123                 ret = devm_register_reboot_notifier(&wdd->wd_data->dev,
1124                                                     &wdd->reboot_nb);
1125                 if (ret) {
1126                         pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
1127                                wdd->id, ret);
1128                         watchdog_dev_unregister(wdd);
1129                 }
1130         }
1131
1132         return ret;
1133 }
1134
1135 /*
1136  *      watchdog_dev_unregister: unregister a watchdog device
1137  *      @watchdog: watchdog device
1138  *
1139  *      Unregister watchdog device and if needed the legacy
1140  *      /dev/watchdog device.
1141  */
1142
1143 void watchdog_dev_unregister(struct watchdog_device *wdd)
1144 {
1145         watchdog_unregister_pretimeout(wdd);
1146         watchdog_cdev_unregister(wdd);
1147 }
1148
1149 /*
1150  *      watchdog_dev_init: init dev part of watchdog core
1151  *
1152  *      Allocate a range of chardev nodes to use for watchdog devices
1153  */
1154
1155 int __init watchdog_dev_init(void)
1156 {
1157         int err;
1158         struct sched_param param = {.sched_priority = MAX_RT_PRIO - 1,};
1159
1160         watchdog_kworker = kthread_create_worker(0, "watchdogd");
1161         if (IS_ERR(watchdog_kworker)) {
1162                 pr_err("Failed to create watchdog kworker\n");
1163                 return PTR_ERR(watchdog_kworker);
1164         }
1165         sched_setscheduler(watchdog_kworker->task, SCHED_FIFO, &param);
1166
1167         err = class_register(&watchdog_class);
1168         if (err < 0) {
1169                 pr_err("couldn't register class\n");
1170                 goto err_register;
1171         }
1172
1173         err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1174         if (err < 0) {
1175                 pr_err("watchdog: unable to allocate char dev region\n");
1176                 goto err_alloc;
1177         }
1178
1179         return 0;
1180
1181 err_alloc:
1182         class_unregister(&watchdog_class);
1183 err_register:
1184         kthread_destroy_worker(watchdog_kworker);
1185         return err;
1186 }
1187
1188 /*
1189  *      watchdog_dev_exit: exit dev part of watchdog core
1190  *
1191  *      Release the range of chardev nodes used for watchdog devices
1192  */
1193
1194 void __exit watchdog_dev_exit(void)
1195 {
1196         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1197         class_unregister(&watchdog_class);
1198         kthread_destroy_worker(watchdog_kworker);
1199 }
1200
1201 module_param(handle_boot_enabled, bool, 0444);
1202 MODULE_PARM_DESC(handle_boot_enabled,
1203         "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1204         __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1205
1206 module_param(open_timeout, uint, 0644);
1207 MODULE_PARM_DESC(open_timeout,
1208         "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1209         __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");