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                 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
 455 static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,
 456                                 const char *buf, size_t len)
 457 {
 458         struct watchdog_device *wdd = dev_get_drvdata(dev);
 459         unsigned int value;
 460         int ret;
 461
 462         ret = kstrtouint(buf, 0, &value);
 463         if (ret)
 464                 return ret;
 465         if (value > 1)
 466                 return -EINVAL;
 467         /* nowayout cannot be disabled once set */
 468         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)
 469                 return -EPERM;
 470         watchdog_set_nowayout(wdd, value);
 471         return len;
 472 }
 473 static DEVICE_ATTR_RW(nowayout);
 474
 475 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
 476                                 char *buf)
 477 {
 478         struct watchdog_device *wdd = dev_get_drvdata(dev);
 479         struct watchdog_core_data *wd_data = wdd->wd_data;
 480         unsigned int status;
 481
 482         mutex_lock(&wd_data->lock);
 483         status = watchdog_get_status(wdd);
 484         mutex_unlock(&wd_data->lock);
 485
 486         return sprintf(buf, "0x%x\n", status);
 487 }
 488 static DEVICE_ATTR_RO(status);
 489
 490 static ssize_t bootstatus_show(struct device *dev,
 491                                 struct device_attribute *attr, char *buf)
 492 {
 493         struct watchdog_device *wdd = dev_get_drvdata(dev);
 494
 495         return sprintf(buf, "%u\n", wdd->bootstatus);
 496 }
 497 static DEVICE_ATTR_RO(bootstatus);
 498
 499 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
 500                                 char *buf)
 501 {
 502         struct watchdog_device *wdd = dev_get_drvdata(dev);
 503         struct watchdog_core_data *wd_data = wdd->wd_data;
 504         ssize_t status;
 505         unsigned int val;
 506
 507         mutex_lock(&wd_data->lock);
 508         status = watchdog_get_timeleft(wdd, &val);
 509         mutex_unlock(&wd_data->lock);
 510         if (!status)
 511                 status = sprintf(buf, "%u\n", val);
 512
 513         return status;
 514 }
 515 static DEVICE_ATTR_RO(timeleft);
 516
 517 static ssize_t timeout_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, "%u\n", wdd->timeout);
 523 }
 524 static DEVICE_ATTR_RO(timeout);
 525
 526 static ssize_t pretimeout_show(struct device *dev,
 527                                struct device_attribute *attr, char *buf)
 528 {
 529         struct watchdog_device *wdd = dev_get_drvdata(dev);
 530
 531         return sprintf(buf, "%u\n", wdd->pretimeout);
 532 }
 533 static DEVICE_ATTR_RO(pretimeout);
 534
 535 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
 536                                 char *buf)
 537 {
 538         struct watchdog_device *wdd = dev_get_drvdata(dev);
 539
 540         return sprintf(buf, "%s\n", wdd->info->identity);
 541 }
 542 static DEVICE_ATTR_RO(identity);
 543
 544 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 545                                 char *buf)
 546 {
 547         struct watchdog_device *wdd = dev_get_drvdata(dev);
 548
 549         if (watchdog_active(wdd))
 550                 return sprintf(buf, "active\n");
 551
 552         return sprintf(buf, "inactive\n");
 553 }
 554 static DEVICE_ATTR_RO(state);
 555
 556 static ssize_t pretimeout_available_governors_show(struct device *dev,
 557                                    struct device_attribute *attr, char *buf)
 558 {
 559         return watchdog_pretimeout_available_governors_get(buf);
 560 }
 561 static DEVICE_ATTR_RO(pretimeout_available_governors);
 562
 563 static ssize_t pretimeout_governor_show(struct device *dev,
 564                                         struct device_attribute *attr,
 565                                         char *buf)
 566 {
 567         struct watchdog_device *wdd = dev_get_drvdata(dev);
 568
 569         return watchdog_pretimeout_governor_get(wdd, buf);
 570 }
 571
 572 static ssize_t pretimeout_governor_store(struct device *dev,
 573                                          struct device_attribute *attr,
 574                                          const char *buf, size_t count)
 575 {
 576         struct watchdog_device *wdd = dev_get_drvdata(dev);
 577         int ret = watchdog_pretimeout_governor_set(wdd, buf);
 578
 579         if (!ret)
 580                 ret = count;
 581
 582         return ret;
 583 }
 584 static DEVICE_ATTR_RW(pretimeout_governor);
 585
 586 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
 587                                 int n)
 588 {
 589         struct device *dev = container_of(kobj, struct device, kobj);
 590         struct watchdog_device *wdd = dev_get_drvdata(dev);
 591         umode_t mode = attr->mode;
 592
 593         if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
 594                 mode = 0;
 595         else if (attr == &dev_attr_pretimeout.attr &&
 596                  !(wdd->info->options & WDIOF_PRETIMEOUT))
 597                 mode = 0;
 598         else if ((attr == &dev_attr_pretimeout_governor.attr ||
 599                   attr == &dev_attr_pretimeout_available_governors.attr) &&
 600                  (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
 601                   !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
 602                 mode = 0;
 603
 604         return mode;
 605 }
 606 static struct attribute *wdt_attrs[] = {
 607         &dev_attr_state.attr,
 608         &dev_attr_identity.attr,
 609         &dev_attr_timeout.attr,
 610         &dev_attr_pretimeout.attr,
 611         &dev_attr_timeleft.attr,
 612         &dev_attr_bootstatus.attr,
 613         &dev_attr_status.attr,
 614         &dev_attr_nowayout.attr,
 615         &dev_attr_pretimeout_governor.attr,
 616         &dev_attr_pretimeout_available_governors.attr,
 617         NULL,
 618 };
 619
 620 static const struct attribute_group wdt_group = {
 621         .attrs = wdt_attrs,
 622         .is_visible = wdt_is_visible,
 623 };
 624 __ATTRIBUTE_GROUPS(wdt);
 625 #else
 626 #define wdt_groups      NULL
 627 #endif
 628
 629 /*
 630  *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 631  *      @wdd: the watchdog device to do the ioctl on
 632  *      @cmd: watchdog command
 633  *      @arg: argument pointer
 634  *
 635  *      The caller must hold wd_data->lock.
 636  */
 637
 638 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
 639                                                         unsigned long arg)
 640 {
 641         if (!wdd->ops->ioctl)
 642                 return -ENOIOCTLCMD;
 643
 644         return wdd->ops->ioctl(wdd, cmd, arg);
 645 }
 646
 647 /*
 648  *      watchdog_write: writes to the watchdog.
 649  *      @file: file from VFS
 650  *      @data: user address of data
 651  *      @len: length of data
 652  *      @ppos: pointer to the file offset
 653  *
 654  *      A write to a watchdog device is defined as a keepalive ping.
 655  *      Writing the magic 'V' sequence allows the next close to turn
 656  *      off the watchdog (if 'nowayout' is not set).
 657  */
 658
 659 static ssize_t watchdog_write(struct file *file, const char __user *data,
 660                                                 size_t len, loff_t *ppos)
 661 {
 662         struct watchdog_core_data *wd_data = file->private_data;
 663         struct watchdog_device *wdd;
 664         int err;
 665         size_t i;
 666         char c;
 667
 668         if (len == 0)
 669                 return 0;
 670
 671         /*
 672          * Note: just in case someone wrote the magic character
 673          * five months ago...
 674          */
 675         clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 676
 677         /* scan to see whether or not we got the magic character */
 678         for (i = 0; i != len; i++) {
 679                 if (get_user(c, data + i))
 680                         return -EFAULT;
 681                 if (c == 'V')
 682                         set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 683         }
 684
 685         /* someone wrote to us, so we send the watchdog a keepalive ping */
 686
 687         err = -ENODEV;
 688         mutex_lock(&wd_data->lock);
 689         wdd = wd_data->wdd;
 690         if (wdd)
 691                 err = watchdog_ping(wdd);
 692         mutex_unlock(&wd_data->lock);
 693
 694         if (err < 0)
 695                 return err;
 696
 697         return len;
 698 }
 699
 700 /*
 701  *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 702  *      @file: file handle to the device
 703  *      @cmd: watchdog command
 704  *      @arg: argument pointer
 705  *
 706  *      The watchdog API defines a common set of functions for all watchdogs
 707  *      according to their available features.
 708  */
 709
 710 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 711                                                         unsigned long arg)
 712 {
 713         struct watchdog_core_data *wd_data = file->private_data;
 714         void __user *argp = (void __user *)arg;
 715         struct watchdog_device *wdd;
 716         int __user *p = argp;
 717         unsigned int val;
 718         int err;
 719
 720         mutex_lock(&wd_data->lock);
 721
 722         wdd = wd_data->wdd;
 723         if (!wdd) {
 724                 err = -ENODEV;
 725                 goto out_ioctl;
 726         }
 727
 728         err = watchdog_ioctl_op(wdd, cmd, arg);
 729         if (err != -ENOIOCTLCMD)
 730                 goto out_ioctl;
 731
 732         switch (cmd) {
 733         case WDIOC_GETSUPPORT:
 734                 err = copy_to_user(argp, wdd->info,
 735                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
 736                 break;
 737         case WDIOC_GETSTATUS:
 738                 val = watchdog_get_status(wdd);
 739                 err = put_user(val, p);
 740                 break;
 741         case WDIOC_GETBOOTSTATUS:
 742                 err = put_user(wdd->bootstatus, p);
 743                 break;
 744         case WDIOC_SETOPTIONS:
 745                 if (get_user(val, p)) {
 746                         err = -EFAULT;
 747                         break;
 748                 }
 749                 if (val & WDIOS_DISABLECARD) {
 750                         err = watchdog_stop(wdd);
 751                         if (err < 0)
 752                                 break;
 753                 }
 754                 if (val & WDIOS_ENABLECARD)
 755                         err = watchdog_start(wdd);
 756                 break;
 757         case WDIOC_KEEPALIVE:
 758                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
 759                         err = -EOPNOTSUPP;
 760                         break;
 761                 }
 762                 err = watchdog_ping(wdd);
 763                 break;
 764         case WDIOC_SETTIMEOUT:
 765                 if (get_user(val, p)) {
 766                         err = -EFAULT;
 767                         break;
 768                 }
 769                 err = watchdog_set_timeout(wdd, val);
 770                 if (err < 0)
 771                         break;
 772                 /* If the watchdog is active then we send a keepalive ping
 773                  * to make sure that the watchdog keep's running (and if
 774                  * possible that it takes the new timeout) */
 775                 err = watchdog_ping(wdd);
 776                 if (err < 0)
 777                         break;
 778                 /* fall through */
 779         case WDIOC_GETTIMEOUT:
 780                 /* timeout == 0 means that we don't know the timeout */
 781                 if (wdd->timeout == 0) {
 782                         err = -EOPNOTSUPP;
 783                         break;
 784                 }
 785                 err = put_user(wdd->timeout, p);
 786                 break;
 787         case WDIOC_GETTIMELEFT:
 788                 err = watchdog_get_timeleft(wdd, &val);
 789                 if (err < 0)
 790                         break;
 791                 err = put_user(val, p);
 792                 break;
 793         case WDIOC_SETPRETIMEOUT:
 794                 if (get_user(val, p)) {
 795                         err = -EFAULT;
 796                         break;
 797                 }
 798                 err = watchdog_set_pretimeout(wdd, val);
 799                 break;
 800         case WDIOC_GETPRETIMEOUT:
 801                 err = put_user(wdd->pretimeout, p);
 802                 break;
 803         default:
 804                 err = -ENOTTY;
 805                 break;
 806         }
 807
 808 out_ioctl:
 809         mutex_unlock(&wd_data->lock);
 810         return err;
 811 }
 812
 813 /*
 814  *      watchdog_open: open the /dev/watchdog* devices.
 815  *      @inode: inode of device
 816  *      @file: file handle to device
 817  *
 818  *      When the /dev/watchdog* device gets opened, we start the watchdog.
 819  *      Watch out: the /dev/watchdog device is single open, so we make sure
 820  *      it can only be opened once.
 821  */
 822
 823 static int watchdog_open(struct inode *inode, struct file *file)
 824 {
 825         struct watchdog_core_data *wd_data;
 826         struct watchdog_device *wdd;
 827         bool hw_running;
 828         int err;
 829
 830         /* Get the corresponding watchdog device */
 831         if (imajor(inode) == MISC_MAJOR)
 832                 wd_data = old_wd_data;
 833         else
 834                 wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
 835                                        cdev);
 836
 837         /* the watchdog is single open! */
 838         if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
 839                 return -EBUSY;
 840
 841         wdd = wd_data->wdd;
 842
 843         /*
 844          * If the /dev/watchdog device is open, we don't want the module
 845          * to be unloaded.
 846          */
 847         hw_running = watchdog_hw_running(wdd);
 848         if (!hw_running && !try_module_get(wdd->ops->owner)) {
 849                 err = -EBUSY;
 850                 goto out_clear;
 851         }
 852
 853         err = watchdog_start(wdd);
 854         if (err < 0)
 855                 goto out_mod;
 856
 857         file->private_data = wd_data;
 858
 859         if (!hw_running)
 860                 get_device(&wd_data->dev);
 861
 862         /*
 863          * open_timeout only applies for the first open from
 864          * userspace. Set open_deadline to infinity so that the kernel
 865          * will take care of an always-running hardware watchdog in
 866          * case the device gets magic-closed or WDIOS_DISABLECARD is
 867          * applied.
 868          */
 869         wd_data->open_deadline = KTIME_MAX;
 870
 871         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 872         return stream_open(inode, file);
 873
 874 out_mod:
 875         module_put(wd_data->wdd->ops->owner);
 876 out_clear:
 877         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 878         return err;
 879 }
 880
 881 static void watchdog_core_data_release(struct device *dev)
 882 {
 883         struct watchdog_core_data *wd_data;
 884
 885         wd_data = container_of(dev, struct watchdog_core_data, dev);
 886
 887         kfree(wd_data);
 888 }
 889
 890 /*
 891  *      watchdog_release: release the watchdog device.
 892  *      @inode: inode of device
 893  *      @file: file handle to device
 894  *
 895  *      This is the code for when /dev/watchdog gets closed. We will only
 896  *      stop the watchdog when we have received the magic char (and nowayout
 897  *      was not set), else the watchdog will keep running.
 898  */
 899
 900 static int watchdog_release(struct inode *inode, struct file *file)
 901 {
 902         struct watchdog_core_data *wd_data = file->private_data;
 903         struct watchdog_device *wdd;
 904         int err = -EBUSY;
 905         bool running;
 906
 907         mutex_lock(&wd_data->lock);
 908
 909         wdd = wd_data->wdd;
 910         if (!wdd)
 911                 goto done;
 912
 913         /*
 914          * We only stop the watchdog if we received the magic character
 915          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 916          * watchdog_stop will fail.
 917          */
 918         if (!test_bit(WDOG_ACTIVE, &wdd->status))
 919                 err = 0;
 920         else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
 921                  !(wdd->info->options & WDIOF_MAGICCLOSE))
 922                 err = watchdog_stop(wdd);
 923
 924         /* If the watchdog was not stopped, send a keepalive ping */
 925         if (err < 0) {
 926                 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
 927                 watchdog_ping(wdd);
 928         }
 929
 930         watchdog_update_worker(wdd);
 931
 932         /* make sure that /dev/watchdog can be re-opened */
 933         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 934
 935 done:
 936         running = wdd && watchdog_hw_running(wdd);
 937         mutex_unlock(&wd_data->lock);
 938         /*
 939          * Allow the owner module to be unloaded again unless the watchdog
 940          * is still running. If the watchdog is still running, it can not
 941          * be stopped, and its driver must not be unloaded.
 942          */
 943         if (!running) {
 944                 module_put(wd_data->cdev.owner);
 945                 put_device(&wd_data->dev);
 946         }
 947         return 0;
 948 }
 949
 950 static const struct file_operations watchdog_fops = {
 951         .owner          = THIS_MODULE,
 952         .write          = watchdog_write,
 953         .unlocked_ioctl = watchdog_ioctl,
 954         .compat_ioctl   = compat_ptr_ioctl,
 955         .open           = watchdog_open,
 956         .release        = watchdog_release,
 957 };
 958
 959 static struct miscdevice watchdog_miscdev = {
 960         .minor          = WATCHDOG_MINOR,
 961         .name           = "watchdog",
 962         .fops           = &watchdog_fops,
 963 };
 964
 965 static struct class watchdog_class = {
 966         .name =         "watchdog",
 967         .owner =        THIS_MODULE,
 968         .dev_groups =   wdt_groups,
 969 };
 970
 971 /*
 972  *      watchdog_cdev_register: register watchdog character device
 973  *      @wdd: watchdog device
 974  *
 975  *      Register a watchdog character device including handling the legacy
 976  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 977  *      thus we set it up like that.
 978  */
 979
 980 static int watchdog_cdev_register(struct watchdog_device *wdd)
 981 {
 982         struct watchdog_core_data *wd_data;
 983         int err;
 984
 985         wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
 986         if (!wd_data)
 987                 return -ENOMEM;
 988         mutex_init(&wd_data->lock);
 989
 990         wd_data->wdd = wdd;
 991         wdd->wd_data = wd_data;
 992
 993         if (IS_ERR_OR_NULL(watchdog_kworker))
 994                 return -ENODEV;
 995
 996         kthread_init_work(&wd_data->work, watchdog_ping_work);
 997         hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
 998         wd_data->timer.function = watchdog_timer_expired;
 999
1000         if (wdd->id == 0) {
1001                 old_wd_data = wd_data;
1002                 watchdog_miscdev.parent = wdd->parent;
1003                 err = misc_register(&watchdog_miscdev);
1004                 if (err != 0) {
1005                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
1006                                 wdd->info->identity, WATCHDOG_MINOR, err);
1007                         if (err == -EBUSY)
1008                                 pr_err("%s: a legacy watchdog module is probably present.\n",
1009                                         wdd->info->identity);
1010                         old_wd_data = NULL;
1011                         kfree(wd_data);
1012                         return err;
1013                 }
1014         }
1015
1016         device_initialize(&wd_data->dev);
1017         wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
1018         wd_data->dev.class = &watchdog_class;
1019         wd_data->dev.parent = wdd->parent;
1020         wd_data->dev.groups = wdd->groups;
1021         wd_data->dev.release = watchdog_core_data_release;
1022         dev_set_drvdata(&wd_data->dev, wdd);
1023         dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
1024
1025         /* Fill in the data structures */
1026         cdev_init(&wd_data->cdev, &watchdog_fops);
1027
1028         /* Add the device */
1029         err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1030         if (err) {
1031                 pr_err("watchdog%d unable to add device %d:%d\n",
1032                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
1033                 if (wdd->id == 0) {
1034                         misc_deregister(&watchdog_miscdev);
1035                         old_wd_data = NULL;
1036                         put_device(&wd_data->dev);
1037                 }
1038                 return err;
1039         }
1040
1041         wd_data->cdev.owner = wdd->ops->owner;
1042
1043         /* Record time of most recent heartbeat as 'just before now'. */
1044         wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1045         watchdog_set_open_deadline(wd_data);
1046
1047         /*
1048          * If the watchdog is running, prevent its driver from being unloaded,
1049          * and schedule an immediate ping.
1050          */
1051         if (watchdog_hw_running(wdd)) {
1052                 __module_get(wdd->ops->owner);
1053                 get_device(&wd_data->dev);
1054                 if (handle_boot_enabled)
1055                         hrtimer_start(&wd_data->timer, 0,
1056                                       HRTIMER_MODE_REL_HARD);
1057                 else
1058                         pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1059                                 wdd->id);
1060         }
1061
1062         return 0;
1063 }
1064
1065 /*
1066  *      watchdog_cdev_unregister: unregister watchdog character device
1067  *      @watchdog: watchdog device
1068  *
1069  *      Unregister watchdog character device and if needed the legacy
1070  *      /dev/watchdog device.
1071  */
1072
1073 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1074 {
1075         struct watchdog_core_data *wd_data = wdd->wd_data;
1076
1077         cdev_device_del(&wd_data->cdev, &wd_data->dev);
1078         if (wdd->id == 0) {
1079                 misc_deregister(&watchdog_miscdev);
1080                 old_wd_data = NULL;
1081         }
1082
1083         if (watchdog_active(wdd) &&
1084             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1085                 watchdog_stop(wdd);
1086         }
1087
1088         mutex_lock(&wd_data->lock);
1089         wd_data->wdd = NULL;
1090         wdd->wd_data = NULL;
1091         mutex_unlock(&wd_data->lock);
1092
1093         hrtimer_cancel(&wd_data->timer);
1094         kthread_cancel_work_sync(&wd_data->work);
1095
1096         put_device(&wd_data->dev);
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
1120         return ret;
1121 }
1122
1123 /*
1124  *      watchdog_dev_unregister: unregister a watchdog device
1125  *      @watchdog: watchdog device
1126  *
1127  *      Unregister watchdog device and if needed the legacy
1128  *      /dev/watchdog device.
1129  */
1130
1131 void watchdog_dev_unregister(struct watchdog_device *wdd)
1132 {
1133         watchdog_unregister_pretimeout(wdd);
1134         watchdog_cdev_unregister(wdd);
1135 }
1136
1137 /*
1138  *      watchdog_dev_init: init dev part of watchdog core
1139  *
1140  *      Allocate a range of chardev nodes to use for watchdog devices
1141  */
1142
1143 int __init watchdog_dev_init(void)
1144 {
1145         int err;
1146         struct sched_param param = {.sched_priority = MAX_RT_PRIO - 1,};
1147
1148         watchdog_kworker = kthread_create_worker(0, "watchdogd");
1149         if (IS_ERR(watchdog_kworker)) {
1150                 pr_err("Failed to create watchdog kworker\n");
1151                 return PTR_ERR(watchdog_kworker);
1152         }
1153         sched_setscheduler(watchdog_kworker->task, SCHED_FIFO, &param);
1154
1155         err = class_register(&watchdog_class);
1156         if (err < 0) {
1157                 pr_err("couldn't register class\n");
1158                 goto err_register;
1159         }
1160
1161         err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1162         if (err < 0) {
1163                 pr_err("watchdog: unable to allocate char dev region\n");
1164                 goto err_alloc;
1165         }
1166
1167         return 0;
1168
1169 err_alloc:
1170         class_unregister(&watchdog_class);
1171 err_register:
1172         kthread_destroy_worker(watchdog_kworker);
1173         return err;
1174 }
1175
1176 /*
1177  *      watchdog_dev_exit: exit dev part of watchdog core
1178  *
1179  *      Release the range of chardev nodes used for watchdog devices
1180  */
1181
1182 void __exit watchdog_dev_exit(void)
1183 {
1184         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1185         class_unregister(&watchdog_class);
1186         kthread_destroy_worker(watchdog_kworker);
1187 }
1188
1189 module_param(handle_boot_enabled, bool, 0444);
1190 MODULE_PARM_DESC(handle_boot_enabled,
1191         "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1192         __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1193
1194 module_param(open_timeout, uint, 0644);
1195 MODULE_PARM_DESC(open_timeout,
1196         "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1197         __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");