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,
 161                                       HRTIMER_MODE_REL_HARD);
 162         } else {
 163                 hrtimer_cancel(&wd_data->timer);
 164         }
 165 }
 166
 167 static int __watchdog_ping(struct watchdog_device *wdd)
 168 {
 169         struct watchdog_core_data *wd_data = wdd->wd_data;
 170         ktime_t earliest_keepalive, now;
 171         int err;
 172
 173         earliest_keepalive = ktime_add(wd_data->last_hw_keepalive,
 174                                        ms_to_ktime(wdd->min_hw_heartbeat_ms));
 175         now = ktime_get();
 176
 177         if (ktime_after(earliest_keepalive, now)) {
 178                 hrtimer_start(&wd_data->timer,
 179                               ktime_sub(earliest_keepalive, now),
 180                               HRTIMER_MODE_REL_HARD);
 181                 return 0;
 182         }
 183
 184         wd_data->last_hw_keepalive = now;
 185
 186         if (wdd->ops->ping)
 187                 err = wdd->ops->ping(wdd);  /* ping the watchdog */
 188         else
 189                 err = wdd->ops->start(wdd); /* restart watchdog */
 190
 191         watchdog_update_worker(wdd);
 192
 193         return err;
 194 }
 195
 196 /*
 197  *      watchdog_ping: ping the watchdog.
 198  *      @wdd: the watchdog device to ping
 199  *
 200  *      The caller must hold wd_data->lock.
 201  *
 202  *      If the watchdog has no own ping operation then it needs to be
 203  *      restarted via the start operation. This wrapper function does
 204  *      exactly that.
 205  *      We only ping when the watchdog device is running.
 206  */
 207
 208 static int watchdog_ping(struct watchdog_device *wdd)
 209 {
 210         struct watchdog_core_data *wd_data = wdd->wd_data;
 211
 212         if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
 213                 return 0;
 214
 215         set_bit(_WDOG_KEEPALIVE, &wd_data->status);
 216
 217         wd_data->last_keepalive = ktime_get();
 218         return __watchdog_ping(wdd);
 219 }
 220
 221 static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data)
 222 {
 223         struct watchdog_device *wdd = wd_data->wdd;
 224
 225         if (!wdd)
 226                 return false;
 227
 228         if (watchdog_active(wdd))
 229                 return true;
 230
 231         return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data);
 232 }
 233
 234 static void watchdog_ping_work(struct kthread_work *work)
 235 {
 236         struct watchdog_core_data *wd_data;
 237
 238         wd_data = container_of(work, struct watchdog_core_data, work);
 239
 240         mutex_lock(&wd_data->lock);
 241         if (watchdog_worker_should_ping(wd_data))
 242                 __watchdog_ping(wd_data->wdd);
 243         mutex_unlock(&wd_data->lock);
 244 }
 245
 246 static enum hrtimer_restart watchdog_timer_expired(struct hrtimer *timer)
 247 {
 248         struct watchdog_core_data *wd_data;
 249
 250         wd_data = container_of(timer, struct watchdog_core_data, timer);
 251
 252         kthread_queue_work(watchdog_kworker, &wd_data->work);
 253         return HRTIMER_NORESTART;
 254 }
 255
 256 /*
 257  *      watchdog_start: wrapper to start the watchdog.
 258  *      @wdd: the watchdog device to start
 259  *
 260  *      The caller must hold wd_data->lock.
 261  *
 262  *      Start the watchdog if it is not active and mark it active.
 263  *      This function returns zero on success or a negative errno code for
 264  *      failure.
 265  */
 266
 267 static int watchdog_start(struct watchdog_device *wdd)
 268 {
 269         struct watchdog_core_data *wd_data = wdd->wd_data;
 270         ktime_t started_at;
 271         int err;
 272
 273         if (watchdog_active(wdd))
 274                 return 0;
 275
 276         set_bit(_WDOG_KEEPALIVE, &wd_data->status);
 277
 278         started_at = ktime_get();
 279         if (watchdog_hw_running(wdd) && wdd->ops->ping)
 280                 err = wdd->ops->ping(wdd);
 281         else
 282                 err = wdd->ops->start(wdd);
 283         if (err == 0) {
 284                 set_bit(WDOG_ACTIVE, &wdd->status);
 285                 wd_data->last_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                 return -ENODEV;
 976
 977         kthread_init_work(&wd_data->work, watchdog_ping_work);
 978         hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
 979         wd_data->timer.function = watchdog_timer_expired;
 980
 981         if (wdd->id == 0) {
 982                 old_wd_data = wd_data;
 983                 watchdog_miscdev.parent = wdd->parent;
 984                 err = misc_register(&watchdog_miscdev);
 985                 if (err != 0) {
 986                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
 987                                 wdd->info->identity, WATCHDOG_MINOR, err);
 988                         if (err == -EBUSY)
 989                                 pr_err("%s: a legacy watchdog module is probably present.\n",
 990                                         wdd->info->identity);
 991                         old_wd_data = NULL;
 992                         kfree(wd_data);
 993                         return err;
 994                 }
 995         }
 996
 997         device_initialize(&wd_data->dev);
 998         wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
 999         wd_data->dev.class = &watchdog_class;
1000         wd_data->dev.parent = wdd->parent;
1001         wd_data->dev.groups = wdd->groups;
1002         wd_data->dev.release = watchdog_core_data_release;
1003         dev_set_drvdata(&wd_data->dev, wdd);
1004         dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
1005
1006         /* Fill in the data structures */
1007         cdev_init(&wd_data->cdev, &watchdog_fops);
1008
1009         /* Add the device */
1010         err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1011         if (err) {
1012                 pr_err("watchdog%d unable to add device %d:%d\n",
1013                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
1014                 if (wdd->id == 0) {
1015                         misc_deregister(&watchdog_miscdev);
1016                         old_wd_data = NULL;
1017                         put_device(&wd_data->dev);
1018                 }
1019                 return err;
1020         }
1021
1022         wd_data->cdev.owner = wdd->ops->owner;
1023
1024         /* Record time of most recent heartbeat as 'just before now'. */
1025         wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1026         watchdog_set_open_deadline(wd_data);
1027
1028         /*
1029          * If the watchdog is running, prevent its driver from being unloaded,
1030          * and schedule an immediate ping.
1031          */
1032         if (watchdog_hw_running(wdd)) {
1033                 __module_get(wdd->ops->owner);
1034                 get_device(&wd_data->dev);
1035                 if (handle_boot_enabled)
1036                         hrtimer_start(&wd_data->timer, 0,
1037                                       HRTIMER_MODE_REL_HARD);
1038                 else
1039                         pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1040                                 wdd->id);
1041         }
1042
1043         return 0;
1044 }
1045
1046 /*
1047  *      watchdog_cdev_unregister: unregister watchdog character device
1048  *      @watchdog: watchdog device
1049  *
1050  *      Unregister watchdog character device and if needed the legacy
1051  *      /dev/watchdog device.
1052  */
1053
1054 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1055 {
1056         struct watchdog_core_data *wd_data = wdd->wd_data;
1057
1058         cdev_device_del(&wd_data->cdev, &wd_data->dev);
1059         if (wdd->id == 0) {
1060                 misc_deregister(&watchdog_miscdev);
1061                 old_wd_data = NULL;
1062         }
1063
1064         if (watchdog_active(wdd) &&
1065             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1066                 watchdog_stop(wdd);
1067         }
1068
1069         mutex_lock(&wd_data->lock);
1070         wd_data->wdd = NULL;
1071         wdd->wd_data = NULL;
1072         mutex_unlock(&wd_data->lock);
1073
1074         hrtimer_cancel(&wd_data->timer);
1075         kthread_cancel_work_sync(&wd_data->work);
1076
1077         put_device(&wd_data->dev);
1078 }
1079
1080 static int watchdog_reboot_notifier(struct notifier_block *nb,
1081                                     unsigned long code, void *data)
1082 {
1083         struct watchdog_device *wdd;
1084
1085         wdd = container_of(nb, struct watchdog_device, reboot_nb);
1086         if (code == SYS_DOWN || code == SYS_HALT) {
1087                 if (watchdog_active(wdd)) {
1088                         int ret;
1089
1090                         ret = wdd->ops->stop(wdd);
1091                         if (ret)
1092                                 return NOTIFY_BAD;
1093                 }
1094         }
1095
1096         return NOTIFY_DONE;
1097 }
1098
1099 /*
1100  *      watchdog_dev_register: register a watchdog device
1101  *      @wdd: watchdog device
1102  *
1103  *      Register a watchdog device including handling the legacy
1104  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1105  *      thus we set it up like that.
1106  */
1107
1108 int watchdog_dev_register(struct watchdog_device *wdd)
1109 {
1110         int ret;
1111
1112         ret = watchdog_cdev_register(wdd);
1113         if (ret)
1114                 return ret;
1115
1116         ret = watchdog_register_pretimeout(wdd);
1117         if (ret) {
1118                 watchdog_cdev_unregister(wdd);
1119                 return ret;
1120         }
1121
1122         if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
1123                 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
1124
1125                 ret = devm_register_reboot_notifier(&wdd->wd_data->dev,
1126                                                     &wdd->reboot_nb);
1127                 if (ret) {
1128                         pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
1129                                wdd->id, ret);
1130                         watchdog_dev_unregister(wdd);
1131                 }
1132         }
1133
1134         return ret;
1135 }
1136
1137 /*
1138  *      watchdog_dev_unregister: unregister a watchdog device
1139  *      @watchdog: watchdog device
1140  *
1141  *      Unregister watchdog device and if needed the legacy
1142  *      /dev/watchdog device.
1143  */
1144
1145 void watchdog_dev_unregister(struct watchdog_device *wdd)
1146 {
1147         watchdog_unregister_pretimeout(wdd);
1148         watchdog_cdev_unregister(wdd);
1149 }
1150
1151 /*
1152  *      watchdog_dev_init: init dev part of watchdog core
1153  *
1154  *      Allocate a range of chardev nodes to use for watchdog devices
1155  */
1156
1157 int __init watchdog_dev_init(void)
1158 {
1159         int err;
1160         struct sched_param param = {.sched_priority = MAX_RT_PRIO - 1,};
1161
1162         watchdog_kworker = kthread_create_worker(0, "watchdogd");
1163         if (IS_ERR(watchdog_kworker)) {
1164                 pr_err("Failed to create watchdog kworker\n");
1165                 return PTR_ERR(watchdog_kworker);
1166         }
1167         sched_setscheduler(watchdog_kworker->task, SCHED_FIFO, &param);
1168
1169         err = class_register(&watchdog_class);
1170         if (err < 0) {
1171                 pr_err("couldn't register class\n");
1172                 goto err_register;
1173         }
1174
1175         err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1176         if (err < 0) {
1177                 pr_err("watchdog: unable to allocate char dev region\n");
1178                 goto err_alloc;
1179         }
1180
1181         return 0;
1182
1183 err_alloc:
1184         class_unregister(&watchdog_class);
1185 err_register:
1186         kthread_destroy_worker(watchdog_kworker);
1187         return err;
1188 }
1189
1190 /*
1191  *      watchdog_dev_exit: exit dev part of watchdog core
1192  *
1193  *      Release the range of chardev nodes used for watchdog devices
1194  */
1195
1196 void __exit watchdog_dev_exit(void)
1197 {
1198         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1199         class_unregister(&watchdog_class);
1200         kthread_destroy_worker(watchdog_kworker);
1201 }
1202
1203 module_param(handle_boot_enabled, bool, 0444);
1204 MODULE_PARM_DESC(handle_boot_enabled,
1205         "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1206         __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1207
1208 module_param(open_timeout, uint, 0644);
1209 MODULE_PARM_DESC(open_timeout,
1210         "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1211         __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");