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 "watchdog_core.h"
  47 #include "watchdog_pretimeout.h"
  48
  49 /*
  50  * struct watchdog_core_data - watchdog core internal data
  51  * @dev:        The watchdog's internal device
  52  * @cdev:       The watchdog's Character device.
  53  * @wdd:        Pointer to watchdog device.
  54  * @lock:       Lock for watchdog core.
  55  * @status:     Watchdog core internal status bits.
  56  */
  57 struct watchdog_core_data {
  58         struct device dev;
  59         struct cdev cdev;
  60         struct watchdog_device *wdd;
  61         struct mutex lock;
  62         ktime_t last_keepalive;
  63         ktime_t last_hw_keepalive;
  64         ktime_t open_deadline;
  65         struct hrtimer timer;
  66         struct kthread_work work;
  67         unsigned long status;           /* Internal status bits */
  68 #define _WDOG_DEV_OPEN          0       /* Opened ? */
  69 #define _WDOG_ALLOW_RELEASE     1       /* Did we receive the magic char ? */
  70 #define _WDOG_KEEPALIVE         2       /* Did we receive a keepalive ? */
  71 };
  72
  73 /* the dev_t structure to store the dynamically allocated watchdog devices */
  74 static dev_t watchdog_devt;
  75 /* Reference to watchdog device behind /dev/watchdog */
  76 static struct watchdog_core_data *old_wd_data;
  77
  78 static struct kthread_worker *watchdog_kworker;
  79
  80 static bool handle_boot_enabled =
  81         IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
  82
  83 static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
  84
  85 static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
  86 {
  87         return ktime_after(ktime_get(), data->open_deadline);
  88 }
  89
  90 static void watchdog_set_open_deadline(struct watchdog_core_data *data)
  91 {
  92         data->open_deadline = open_timeout ?
  93                 ktime_get() + ktime_set(open_timeout, 0) : KTIME_MAX;
  94 }
  95
  96 static inline bool watchdog_need_worker(struct watchdog_device *wdd)
  97 {
  98         /* All variables in milli-seconds */
  99         unsigned int hm = wdd->max_hw_heartbeat_ms;
 100         unsigned int t = wdd->timeout * 1000;
 101
 102         /*
 103          * A worker to generate heartbeat requests is needed if all of the
 104          * following conditions are true.
 105          * - Userspace activated the watchdog.
 106          * - The driver provided a value for the maximum hardware timeout, and
 107          *   thus is aware that the framework supports generating heartbeat
 108          *   requests.
 109          * - Userspace requests a longer timeout than the hardware can handle.
 110          *
 111          * Alternatively, if userspace has not opened the watchdog
 112          * device, we take care of feeding the watchdog if it is
 113          * running.
 114          */
 115         return (hm && watchdog_active(wdd) && t > hm) ||
 116                 (t && !watchdog_active(wdd) && watchdog_hw_running(wdd));
 117 }
 118
 119 static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
 120 {
 121         struct watchdog_core_data *wd_data = wdd->wd_data;
 122         unsigned int timeout_ms = wdd->timeout * 1000;
 123         ktime_t keepalive_interval;
 124         ktime_t last_heartbeat, latest_heartbeat;
 125         ktime_t virt_timeout;
 126         unsigned int hw_heartbeat_ms;
 127
 128         if (watchdog_active(wdd))
 129                 virt_timeout = ktime_add(wd_data->last_keepalive,
 130                                          ms_to_ktime(timeout_ms));
 131         else
 132                 virt_timeout = wd_data->open_deadline;
 133
 134         hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms);
 135         keepalive_interval = ms_to_ktime(hw_heartbeat_ms / 2);
 136
 137         /*
 138          * To ensure that the watchdog times out wdd->timeout seconds
 139          * after the most recent ping from userspace, the last
 140          * worker ping has to come in hw_heartbeat_ms before this timeout.
 141          */
 142         last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms));
 143         latest_heartbeat = ktime_sub(last_heartbeat, ktime_get());
 144         if (ktime_before(latest_heartbeat, keepalive_interval))
 145                 return latest_heartbeat;
 146         return keepalive_interval;
 147 }
 148
 149 static inline void watchdog_update_worker(struct watchdog_device *wdd)
 150 {
 151         struct watchdog_core_data *wd_data = wdd->wd_data;
 152
 153         if (watchdog_need_worker(wdd)) {
 154                 ktime_t t = watchdog_next_keepalive(wdd);
 155
 156                 if (t > 0)
 157                         hrtimer_start(&wd_data->timer, t,
 158                                       HRTIMER_MODE_REL_HARD);
 159         } else {
 160                 hrtimer_cancel(&wd_data->timer);
 161         }
 162 }
 163
 164 static int __watchdog_ping(struct watchdog_device *wdd)
 165 {
 166         struct watchdog_core_data *wd_data = wdd->wd_data;
 167         ktime_t earliest_keepalive, now;
 168         int err;
 169
 170         earliest_keepalive = ktime_add(wd_data->last_hw_keepalive,
 171                                        ms_to_ktime(wdd->min_hw_heartbeat_ms));
 172         now = ktime_get();
 173
 174         if (ktime_after(earliest_keepalive, now)) {
 175                 hrtimer_start(&wd_data->timer,
 176                               ktime_sub(earliest_keepalive, now),
 177                               HRTIMER_MODE_REL_HARD);
 178                 return 0;
 179         }
 180
 181         wd_data->last_hw_keepalive = now;
 182
 183         if (wdd->ops->ping)
 184                 err = wdd->ops->ping(wdd);  /* ping the watchdog */
 185         else
 186                 err = wdd->ops->start(wdd); /* restart watchdog */
 187
 188         watchdog_update_worker(wdd);
 189
 190         return err;
 191 }
 192
 193 /*
 194  *      watchdog_ping: ping the watchdog.
 195  *      @wdd: the watchdog device to ping
 196  *
 197  *      The caller must hold wd_data->lock.
 198  *
 199  *      If the watchdog has no own ping operation then it needs to be
 200  *      restarted via the start operation. This wrapper function does
 201  *      exactly that.
 202  *      We only ping when the watchdog device is running.
 203  */
 204
 205 static int watchdog_ping(struct watchdog_device *wdd)
 206 {
 207         struct watchdog_core_data *wd_data = wdd->wd_data;
 208
 209         if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
 210                 return 0;
 211
 212         set_bit(_WDOG_KEEPALIVE, &wd_data->status);
 213
 214         wd_data->last_keepalive = ktime_get();
 215         return __watchdog_ping(wdd);
 216 }
 217
 218 static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data)
 219 {
 220         struct watchdog_device *wdd = wd_data->wdd;
 221
 222         if (!wdd)
 223                 return false;
 224
 225         if (watchdog_active(wdd))
 226                 return true;
 227
 228         return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data);
 229 }
 230
 231 static void watchdog_ping_work(struct kthread_work *work)
 232 {
 233         struct watchdog_core_data *wd_data;
 234
 235         wd_data = container_of(work, struct watchdog_core_data, work);
 236
 237         mutex_lock(&wd_data->lock);
 238         if (watchdog_worker_should_ping(wd_data))
 239                 __watchdog_ping(wd_data->wdd);
 240         mutex_unlock(&wd_data->lock);
 241 }
 242
 243 static enum hrtimer_restart watchdog_timer_expired(struct hrtimer *timer)
 244 {
 245         struct watchdog_core_data *wd_data;
 246
 247         wd_data = container_of(timer, struct watchdog_core_data, timer);
 248
 249         kthread_queue_work(watchdog_kworker, &wd_data->work);
 250         return HRTIMER_NORESTART;
 251 }
 252
 253 /*
 254  *      watchdog_start: wrapper to start the watchdog.
 255  *      @wdd: the watchdog device to start
 256  *
 257  *      The caller must hold wd_data->lock.
 258  *
 259  *      Start the watchdog if it is not active and mark it active.
 260  *      This function returns zero on success or a negative errno code for
 261  *      failure.
 262  */
 263
 264 static int watchdog_start(struct watchdog_device *wdd)
 265 {
 266         struct watchdog_core_data *wd_data = wdd->wd_data;
 267         ktime_t started_at;
 268         int err;
 269
 270         if (watchdog_active(wdd))
 271                 return 0;
 272
 273         set_bit(_WDOG_KEEPALIVE, &wd_data->status);
 274
 275         started_at = ktime_get();
 276         if (watchdog_hw_running(wdd) && wdd->ops->ping) {
 277                 err = __watchdog_ping(wdd);
 278                 if (err == 0)
 279                         set_bit(WDOG_ACTIVE, &wdd->status);
 280         } else {
 281                 err = wdd->ops->start(wdd);
 282                 if (err == 0) {
 283                         set_bit(WDOG_ACTIVE, &wdd->status);
 284                         wd_data->last_keepalive = started_at;
 285                         wd_data->last_hw_keepalive = started_at;
 286                         watchdog_update_worker(wdd);
 287                 }
 288         }
 289
 290         return err;
 291 }
 292
 293 /*
 294  *      watchdog_stop: wrapper to stop the watchdog.
 295  *      @wdd: the watchdog device to stop
 296  *
 297  *      The caller must hold wd_data->lock.
 298  *
 299  *      Stop the watchdog if it is still active and unmark it active.
 300  *      This function returns zero on success or a negative errno code for
 301  *      failure.
 302  *      If the 'nowayout' feature was set, the watchdog cannot be stopped.
 303  */
 304
 305 static int watchdog_stop(struct watchdog_device *wdd)
 306 {
 307         int err = 0;
 308
 309         if (!watchdog_active(wdd))
 310                 return 0;
 311
 312         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
 313                 pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
 314                         wdd->id);
 315                 return -EBUSY;
 316         }
 317
 318         if (wdd->ops->stop) {
 319                 clear_bit(WDOG_HW_RUNNING, &wdd->status);
 320                 err = wdd->ops->stop(wdd);
 321         } else {
 322                 set_bit(WDOG_HW_RUNNING, &wdd->status);
 323         }
 324
 325         if (err == 0) {
 326                 clear_bit(WDOG_ACTIVE, &wdd->status);
 327                 watchdog_update_worker(wdd);
 328         }
 329
 330         return err;
 331 }
 332
 333 /*
 334  *      watchdog_get_status: wrapper to get the watchdog status
 335  *      @wdd: the watchdog device to get the status from
 336  *
 337  *      The caller must hold wd_data->lock.
 338  *
 339  *      Get the watchdog's status flags.
 340  */
 341
 342 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
 343 {
 344         struct watchdog_core_data *wd_data = wdd->wd_data;
 345         unsigned int status;
 346
 347         if (wdd->ops->status)
 348                 status = wdd->ops->status(wdd);
 349         else
 350                 status = wdd->bootstatus & (WDIOF_CARDRESET |
 351                                             WDIOF_OVERHEAT |
 352                                             WDIOF_FANFAULT |
 353                                             WDIOF_EXTERN1 |
 354                                             WDIOF_EXTERN2 |
 355                                             WDIOF_POWERUNDER |
 356                                             WDIOF_POWEROVER);
 357
 358         if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
 359                 status |= WDIOF_MAGICCLOSE;
 360
 361         if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
 362                 status |= WDIOF_KEEPALIVEPING;
 363
 364         return status;
 365 }
 366
 367 /*
 368  *      watchdog_set_timeout: set the watchdog timer timeout
 369  *      @wdd: the watchdog device to set the timeout for
 370  *      @timeout: timeout to set in seconds
 371  *
 372  *      The caller must hold wd_data->lock.
 373  */
 374
 375 static int watchdog_set_timeout(struct watchdog_device *wdd,
 376                                                         unsigned int timeout)
 377 {
 378         int err = 0;
 379
 380         if (!(wdd->info->options & WDIOF_SETTIMEOUT))
 381                 return -EOPNOTSUPP;
 382
 383         if (watchdog_timeout_invalid(wdd, timeout))
 384                 return -EINVAL;
 385
 386         if (wdd->ops->set_timeout) {
 387                 err = wdd->ops->set_timeout(wdd, timeout);
 388         } else {
 389                 wdd->timeout = timeout;
 390                 /* Disable pretimeout if it doesn't fit the new timeout */
 391                 if (wdd->pretimeout >= wdd->timeout)
 392                         wdd->pretimeout = 0;
 393         }
 394
 395         watchdog_update_worker(wdd);
 396
 397         return err;
 398 }
 399
 400 /*
 401  *      watchdog_set_pretimeout: set the watchdog timer pretimeout
 402  *      @wdd: the watchdog device to set the timeout for
 403  *      @timeout: pretimeout to set in seconds
 404  */
 405
 406 static int watchdog_set_pretimeout(struct watchdog_device *wdd,
 407                                    unsigned int timeout)
 408 {
 409         int err = 0;
 410
 411         if (!(wdd->info->options & WDIOF_PRETIMEOUT))
 412                 return -EOPNOTSUPP;
 413
 414         if (watchdog_pretimeout_invalid(wdd, timeout))
 415                 return -EINVAL;
 416
 417         if (wdd->ops->set_pretimeout)
 418                 err = wdd->ops->set_pretimeout(wdd, timeout);
 419         else
 420                 wdd->pretimeout = timeout;
 421
 422         return err;
 423 }
 424
 425 /*
 426  *      watchdog_get_timeleft: wrapper to get the time left before a reboot
 427  *      @wdd: the watchdog device to get the remaining time from
 428  *      @timeleft: the time that's left
 429  *
 430  *      The caller must hold wd_data->lock.
 431  *
 432  *      Get the time before a watchdog will reboot (if not pinged).
 433  */
 434
 435 static int watchdog_get_timeleft(struct watchdog_device *wdd,
 436                                                         unsigned int *timeleft)
 437 {
 438         *timeleft = 0;
 439
 440         if (!wdd->ops->get_timeleft)
 441                 return -EOPNOTSUPP;
 442
 443         *timeleft = wdd->ops->get_timeleft(wdd);
 444
 445         return 0;
 446 }
 447
 448 #ifdef CONFIG_WATCHDOG_SYSFS
 449 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
 450                                 char *buf)
 451 {
 452         struct watchdog_device *wdd = dev_get_drvdata(dev);
 453
 454         return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
 455 }
 456
 457 static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,
 458                                 const char *buf, size_t len)
 459 {
 460         struct watchdog_device *wdd = dev_get_drvdata(dev);
 461         unsigned int value;
 462         int ret;
 463
 464         ret = kstrtouint(buf, 0, &value);
 465         if (ret)
 466                 return ret;
 467         if (value > 1)
 468                 return -EINVAL;
 469         /* nowayout cannot be disabled once set */
 470         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)
 471                 return -EPERM;
 472         watchdog_set_nowayout(wdd, value);
 473         return len;
 474 }
 475 static DEVICE_ATTR_RW(nowayout);
 476
 477 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
 478                                 char *buf)
 479 {
 480         struct watchdog_device *wdd = dev_get_drvdata(dev);
 481         struct watchdog_core_data *wd_data = wdd->wd_data;
 482         unsigned int status;
 483
 484         mutex_lock(&wd_data->lock);
 485         status = watchdog_get_status(wdd);
 486         mutex_unlock(&wd_data->lock);
 487
 488         return sprintf(buf, "0x%x\n", status);
 489 }
 490 static DEVICE_ATTR_RO(status);
 491
 492 static ssize_t bootstatus_show(struct device *dev,
 493                                 struct device_attribute *attr, char *buf)
 494 {
 495         struct watchdog_device *wdd = dev_get_drvdata(dev);
 496
 497         return sprintf(buf, "%u\n", wdd->bootstatus);
 498 }
 499 static DEVICE_ATTR_RO(bootstatus);
 500
 501 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
 502                                 char *buf)
 503 {
 504         struct watchdog_device *wdd = dev_get_drvdata(dev);
 505         struct watchdog_core_data *wd_data = wdd->wd_data;
 506         ssize_t status;
 507         unsigned int val;
 508
 509         mutex_lock(&wd_data->lock);
 510         status = watchdog_get_timeleft(wdd, &val);
 511         mutex_unlock(&wd_data->lock);
 512         if (!status)
 513                 status = sprintf(buf, "%u\n", val);
 514
 515         return status;
 516 }
 517 static DEVICE_ATTR_RO(timeleft);
 518
 519 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
 520                                 char *buf)
 521 {
 522         struct watchdog_device *wdd = dev_get_drvdata(dev);
 523
 524         return sprintf(buf, "%u\n", wdd->timeout);
 525 }
 526 static DEVICE_ATTR_RO(timeout);
 527
 528 static ssize_t min_timeout_show(struct device *dev,
 529                                 struct device_attribute *attr, char *buf)
 530 {
 531         struct watchdog_device *wdd = dev_get_drvdata(dev);
 532
 533         return sysfs_emit(buf, "%u\n", wdd->min_timeout);
 534 }
 535 static DEVICE_ATTR_RO(min_timeout);
 536
 537 static ssize_t max_timeout_show(struct device *dev,
 538                                 struct device_attribute *attr, char *buf)
 539 {
 540         struct watchdog_device *wdd = dev_get_drvdata(dev);
 541
 542         return sysfs_emit(buf, "%u\n", wdd->max_timeout);
 543 }
 544 static DEVICE_ATTR_RO(max_timeout);
 545
 546 static ssize_t pretimeout_show(struct device *dev,
 547                                struct device_attribute *attr, char *buf)
 548 {
 549         struct watchdog_device *wdd = dev_get_drvdata(dev);
 550
 551         return sprintf(buf, "%u\n", wdd->pretimeout);
 552 }
 553 static DEVICE_ATTR_RO(pretimeout);
 554
 555 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
 556                                 char *buf)
 557 {
 558         struct watchdog_device *wdd = dev_get_drvdata(dev);
 559
 560         return sprintf(buf, "%s\n", wdd->info->identity);
 561 }
 562 static DEVICE_ATTR_RO(identity);
 563
 564 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 565                                 char *buf)
 566 {
 567         struct watchdog_device *wdd = dev_get_drvdata(dev);
 568
 569         if (watchdog_active(wdd))
 570                 return sprintf(buf, "active\n");
 571
 572         return sprintf(buf, "inactive\n");
 573 }
 574 static DEVICE_ATTR_RO(state);
 575
 576 static ssize_t pretimeout_available_governors_show(struct device *dev,
 577                                    struct device_attribute *attr, char *buf)
 578 {
 579         return watchdog_pretimeout_available_governors_get(buf);
 580 }
 581 static DEVICE_ATTR_RO(pretimeout_available_governors);
 582
 583 static ssize_t pretimeout_governor_show(struct device *dev,
 584                                         struct device_attribute *attr,
 585                                         char *buf)
 586 {
 587         struct watchdog_device *wdd = dev_get_drvdata(dev);
 588
 589         return watchdog_pretimeout_governor_get(wdd, buf);
 590 }
 591
 592 static ssize_t pretimeout_governor_store(struct device *dev,
 593                                          struct device_attribute *attr,
 594                                          const char *buf, size_t count)
 595 {
 596         struct watchdog_device *wdd = dev_get_drvdata(dev);
 597         int ret = watchdog_pretimeout_governor_set(wdd, buf);
 598
 599         if (!ret)
 600                 ret = count;
 601
 602         return ret;
 603 }
 604 static DEVICE_ATTR_RW(pretimeout_governor);
 605
 606 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
 607                                 int n)
 608 {
 609         struct device *dev = kobj_to_dev(kobj);
 610         struct watchdog_device *wdd = dev_get_drvdata(dev);
 611         umode_t mode = attr->mode;
 612
 613         if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
 614                 mode = 0;
 615         else if (attr == &dev_attr_pretimeout.attr &&
 616                  !(wdd->info->options & WDIOF_PRETIMEOUT))
 617                 mode = 0;
 618         else if ((attr == &dev_attr_pretimeout_governor.attr ||
 619                   attr == &dev_attr_pretimeout_available_governors.attr) &&
 620                  (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
 621                   !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
 622                 mode = 0;
 623
 624         return mode;
 625 }
 626 static struct attribute *wdt_attrs[] = {
 627         &dev_attr_state.attr,
 628         &dev_attr_identity.attr,
 629         &dev_attr_timeout.attr,
 630         &dev_attr_min_timeout.attr,
 631         &dev_attr_max_timeout.attr,
 632         &dev_attr_pretimeout.attr,
 633         &dev_attr_timeleft.attr,
 634         &dev_attr_bootstatus.attr,
 635         &dev_attr_status.attr,
 636         &dev_attr_nowayout.attr,
 637         &dev_attr_pretimeout_governor.attr,
 638         &dev_attr_pretimeout_available_governors.attr,
 639         NULL,
 640 };
 641
 642 static const struct attribute_group wdt_group = {
 643         .attrs = wdt_attrs,
 644         .is_visible = wdt_is_visible,
 645 };
 646 __ATTRIBUTE_GROUPS(wdt);
 647 #else
 648 #define wdt_groups      NULL
 649 #endif
 650
 651 /*
 652  *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 653  *      @wdd: the watchdog device to do the ioctl on
 654  *      @cmd: watchdog command
 655  *      @arg: argument pointer
 656  *
 657  *      The caller must hold wd_data->lock.
 658  */
 659
 660 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
 661                                                         unsigned long arg)
 662 {
 663         if (!wdd->ops->ioctl)
 664                 return -ENOIOCTLCMD;
 665
 666         return wdd->ops->ioctl(wdd, cmd, arg);
 667 }
 668
 669 /*
 670  *      watchdog_write: writes to the watchdog.
 671  *      @file: file from VFS
 672  *      @data: user address of data
 673  *      @len: length of data
 674  *      @ppos: pointer to the file offset
 675  *
 676  *      A write to a watchdog device is defined as a keepalive ping.
 677  *      Writing the magic 'V' sequence allows the next close to turn
 678  *      off the watchdog (if 'nowayout' is not set).
 679  */
 680
 681 static ssize_t watchdog_write(struct file *file, const char __user *data,
 682                                                 size_t len, loff_t *ppos)
 683 {
 684         struct watchdog_core_data *wd_data = file->private_data;
 685         struct watchdog_device *wdd;
 686         int err;
 687         size_t i;
 688         char c;
 689
 690         if (len == 0)
 691                 return 0;
 692
 693         /*
 694          * Note: just in case someone wrote the magic character
 695          * five months ago...
 696          */
 697         clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 698
 699         /* scan to see whether or not we got the magic character */
 700         for (i = 0; i != len; i++) {
 701                 if (get_user(c, data + i))
 702                         return -EFAULT;
 703                 if (c == 'V')
 704                         set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 705         }
 706
 707         /* someone wrote to us, so we send the watchdog a keepalive ping */
 708
 709         err = -ENODEV;
 710         mutex_lock(&wd_data->lock);
 711         wdd = wd_data->wdd;
 712         if (wdd)
 713                 err = watchdog_ping(wdd);
 714         mutex_unlock(&wd_data->lock);
 715
 716         if (err < 0)
 717                 return err;
 718
 719         return len;
 720 }
 721
 722 /*
 723  *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 724  *      @file: file handle to the device
 725  *      @cmd: watchdog command
 726  *      @arg: argument pointer
 727  *
 728  *      The watchdog API defines a common set of functions for all watchdogs
 729  *      according to their available features.
 730  */
 731
 732 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 733                                                         unsigned long arg)
 734 {
 735         struct watchdog_core_data *wd_data = file->private_data;
 736         void __user *argp = (void __user *)arg;
 737         struct watchdog_device *wdd;
 738         int __user *p = argp;
 739         unsigned int val;
 740         int err;
 741
 742         mutex_lock(&wd_data->lock);
 743
 744         wdd = wd_data->wdd;
 745         if (!wdd) {
 746                 err = -ENODEV;
 747                 goto out_ioctl;
 748         }
 749
 750         err = watchdog_ioctl_op(wdd, cmd, arg);
 751         if (err != -ENOIOCTLCMD)
 752                 goto out_ioctl;
 753
 754         switch (cmd) {
 755         case WDIOC_GETSUPPORT:
 756                 err = copy_to_user(argp, wdd->info,
 757                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
 758                 break;
 759         case WDIOC_GETSTATUS:
 760                 val = watchdog_get_status(wdd);
 761                 err = put_user(val, p);
 762                 break;
 763         case WDIOC_GETBOOTSTATUS:
 764                 err = put_user(wdd->bootstatus, p);
 765                 break;
 766         case WDIOC_SETOPTIONS:
 767                 if (get_user(val, p)) {
 768                         err = -EFAULT;
 769                         break;
 770                 }
 771                 if (val & WDIOS_DISABLECARD) {
 772                         err = watchdog_stop(wdd);
 773                         if (err < 0)
 774                                 break;
 775                 }
 776                 if (val & WDIOS_ENABLECARD)
 777                         err = watchdog_start(wdd);
 778                 break;
 779         case WDIOC_KEEPALIVE:
 780                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
 781                         err = -EOPNOTSUPP;
 782                         break;
 783                 }
 784                 err = watchdog_ping(wdd);
 785                 break;
 786         case WDIOC_SETTIMEOUT:
 787                 if (get_user(val, p)) {
 788                         err = -EFAULT;
 789                         break;
 790                 }
 791                 err = watchdog_set_timeout(wdd, val);
 792                 if (err < 0)
 793                         break;
 794                 /* If the watchdog is active then we send a keepalive ping
 795                  * to make sure that the watchdog keep's running (and if
 796                  * possible that it takes the new timeout) */
 797                 err = watchdog_ping(wdd);
 798                 if (err < 0)
 799                         break;
 800                 fallthrough;
 801         case WDIOC_GETTIMEOUT:
 802                 /* timeout == 0 means that we don't know the timeout */
 803                 if (wdd->timeout == 0) {
 804                         err = -EOPNOTSUPP;
 805                         break;
 806                 }
 807                 err = put_user(wdd->timeout, p);
 808                 break;
 809         case WDIOC_GETTIMELEFT:
 810                 err = watchdog_get_timeleft(wdd, &val);
 811                 if (err < 0)
 812                         break;
 813                 err = put_user(val, p);
 814                 break;
 815         case WDIOC_SETPRETIMEOUT:
 816                 if (get_user(val, p)) {
 817                         err = -EFAULT;
 818                         break;
 819                 }
 820                 err = watchdog_set_pretimeout(wdd, val);
 821                 break;
 822         case WDIOC_GETPRETIMEOUT:
 823                 err = put_user(wdd->pretimeout, p);
 824                 break;
 825         default:
 826                 err = -ENOTTY;
 827                 break;
 828         }
 829
 830 out_ioctl:
 831         mutex_unlock(&wd_data->lock);
 832         return err;
 833 }
 834
 835 /*
 836  *      watchdog_open: open the /dev/watchdog* devices.
 837  *      @inode: inode of device
 838  *      @file: file handle to device
 839  *
 840  *      When the /dev/watchdog* device gets opened, we start the watchdog.
 841  *      Watch out: the /dev/watchdog device is single open, so we make sure
 842  *      it can only be opened once.
 843  */
 844
 845 static int watchdog_open(struct inode *inode, struct file *file)
 846 {
 847         struct watchdog_core_data *wd_data;
 848         struct watchdog_device *wdd;
 849         bool hw_running;
 850         int err;
 851
 852         /* Get the corresponding watchdog device */
 853         if (imajor(inode) == MISC_MAJOR)
 854                 wd_data = old_wd_data;
 855         else
 856                 wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
 857                                        cdev);
 858
 859         /* the watchdog is single open! */
 860         if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
 861                 return -EBUSY;
 862
 863         wdd = wd_data->wdd;
 864
 865         /*
 866          * If the /dev/watchdog device is open, we don't want the module
 867          * to be unloaded.
 868          */
 869         hw_running = watchdog_hw_running(wdd);
 870         if (!hw_running && !try_module_get(wdd->ops->owner)) {
 871                 err = -EBUSY;
 872                 goto out_clear;
 873         }
 874
 875         err = watchdog_start(wdd);
 876         if (err < 0)
 877                 goto out_mod;
 878
 879         file->private_data = wd_data;
 880
 881         if (!hw_running)
 882                 get_device(&wd_data->dev);
 883
 884         /*
 885          * open_timeout only applies for the first open from
 886          * userspace. Set open_deadline to infinity so that the kernel
 887          * will take care of an always-running hardware watchdog in
 888          * case the device gets magic-closed or WDIOS_DISABLECARD is
 889          * applied.
 890          */
 891         wd_data->open_deadline = KTIME_MAX;
 892
 893         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 894         return stream_open(inode, file);
 895
 896 out_mod:
 897         module_put(wd_data->wdd->ops->owner);
 898 out_clear:
 899         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 900         return err;
 901 }
 902
 903 static void watchdog_core_data_release(struct device *dev)
 904 {
 905         struct watchdog_core_data *wd_data;
 906
 907         wd_data = container_of(dev, struct watchdog_core_data, dev);
 908
 909         kfree(wd_data);
 910 }
 911
 912 /*
 913  *      watchdog_release: release the watchdog device.
 914  *      @inode: inode of device
 915  *      @file: file handle to device
 916  *
 917  *      This is the code for when /dev/watchdog gets closed. We will only
 918  *      stop the watchdog when we have received the magic char (and nowayout
 919  *      was not set), else the watchdog will keep running.
 920  */
 921
 922 static int watchdog_release(struct inode *inode, struct file *file)
 923 {
 924         struct watchdog_core_data *wd_data = file->private_data;
 925         struct watchdog_device *wdd;
 926         int err = -EBUSY;
 927         bool running;
 928
 929         mutex_lock(&wd_data->lock);
 930
 931         wdd = wd_data->wdd;
 932         if (!wdd)
 933                 goto done;
 934
 935         /*
 936          * We only stop the watchdog if we received the magic character
 937          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 938          * watchdog_stop will fail.
 939          */
 940         if (!watchdog_active(wdd))
 941                 err = 0;
 942         else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
 943                  !(wdd->info->options & WDIOF_MAGICCLOSE))
 944                 err = watchdog_stop(wdd);
 945
 946         /* If the watchdog was not stopped, send a keepalive ping */
 947         if (err < 0) {
 948                 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
 949                 watchdog_ping(wdd);
 950         }
 951
 952         watchdog_update_worker(wdd);
 953
 954         /* make sure that /dev/watchdog can be re-opened */
 955         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 956
 957 done:
 958         running = wdd && watchdog_hw_running(wdd);
 959         mutex_unlock(&wd_data->lock);
 960         /*
 961          * Allow the owner module to be unloaded again unless the watchdog
 962          * is still running. If the watchdog is still running, it can not
 963          * be stopped, and its driver must not be unloaded.
 964          */
 965         if (!running) {
 966                 module_put(wd_data->cdev.owner);
 967                 put_device(&wd_data->dev);
 968         }
 969         return 0;
 970 }
 971
 972 static const struct file_operations watchdog_fops = {
 973         .owner          = THIS_MODULE,
 974         .write          = watchdog_write,
 975         .unlocked_ioctl = watchdog_ioctl,
 976         .compat_ioctl   = compat_ptr_ioctl,
 977         .open           = watchdog_open,
 978         .release        = watchdog_release,
 979 };
 980
 981 static struct miscdevice watchdog_miscdev = {
 982         .minor          = WATCHDOG_MINOR,
 983         .name           = "watchdog",
 984         .fops           = &watchdog_fops,
 985 };
 986
 987 static struct class watchdog_class = {
 988         .name =         "watchdog",
 989         .owner =        THIS_MODULE,
 990         .dev_groups =   wdt_groups,
 991 };
 992
 993 /*
 994  *      watchdog_cdev_register: register watchdog character device
 995  *      @wdd: watchdog device
 996  *
 997  *      Register a watchdog character device including handling the legacy
 998  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 999  *      thus we set it up like that.
1000  */
1001
1002 static int watchdog_cdev_register(struct watchdog_device *wdd)
1003 {
1004         struct watchdog_core_data *wd_data;
1005         int err;
1006
1007         wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
1008         if (!wd_data)
1009                 return -ENOMEM;
1010         mutex_init(&wd_data->lock);
1011
1012         wd_data->wdd = wdd;
1013         wdd->wd_data = wd_data;
1014
1015         if (IS_ERR_OR_NULL(watchdog_kworker)) {
1016                 kfree(wd_data);
1017                 return -ENODEV;
1018         }
1019
1020         device_initialize(&wd_data->dev);
1021         wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
1022         wd_data->dev.class = &watchdog_class;
1023         wd_data->dev.parent = wdd->parent;
1024         wd_data->dev.groups = wdd->groups;
1025         wd_data->dev.release = watchdog_core_data_release;
1026         dev_set_drvdata(&wd_data->dev, wdd);
1027         dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
1028
1029         kthread_init_work(&wd_data->work, watchdog_ping_work);
1030         hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1031         wd_data->timer.function = watchdog_timer_expired;
1032
1033         if (wdd->id == 0) {
1034                 old_wd_data = wd_data;
1035                 watchdog_miscdev.parent = wdd->parent;
1036                 err = misc_register(&watchdog_miscdev);
1037                 if (err != 0) {
1038                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
1039                                 wdd->info->identity, WATCHDOG_MINOR, err);
1040                         if (err == -EBUSY)
1041                                 pr_err("%s: a legacy watchdog module is probably present.\n",
1042                                         wdd->info->identity);
1043                         old_wd_data = NULL;
1044                         put_device(&wd_data->dev);
1045                         return err;
1046                 }
1047         }
1048
1049         /* Fill in the data structures */
1050         cdev_init(&wd_data->cdev, &watchdog_fops);
1051
1052         /* Add the device */
1053         err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1054         if (err) {
1055                 pr_err("watchdog%d unable to add device %d:%d\n",
1056                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
1057                 if (wdd->id == 0) {
1058                         misc_deregister(&watchdog_miscdev);
1059                         old_wd_data = NULL;
1060                         put_device(&wd_data->dev);
1061                 }
1062                 return err;
1063         }
1064
1065         wd_data->cdev.owner = wdd->ops->owner;
1066
1067         /* Record time of most recent heartbeat as 'just before now'. */
1068         wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1069         watchdog_set_open_deadline(wd_data);
1070
1071         /*
1072          * If the watchdog is running, prevent its driver from being unloaded,
1073          * and schedule an immediate ping.
1074          */
1075         if (watchdog_hw_running(wdd)) {
1076                 __module_get(wdd->ops->owner);
1077                 get_device(&wd_data->dev);
1078                 if (handle_boot_enabled)
1079                         hrtimer_start(&wd_data->timer, 0,
1080                                       HRTIMER_MODE_REL_HARD);
1081                 else
1082                         pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1083                                 wdd->id);
1084         }
1085
1086         return 0;
1087 }
1088
1089 /*
1090  *      watchdog_cdev_unregister: unregister watchdog character device
1091  *      @watchdog: watchdog device
1092  *
1093  *      Unregister watchdog character device and if needed the legacy
1094  *      /dev/watchdog device.
1095  */
1096
1097 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1098 {
1099         struct watchdog_core_data *wd_data = wdd->wd_data;
1100
1101         cdev_device_del(&wd_data->cdev, &wd_data->dev);
1102         if (wdd->id == 0) {
1103                 misc_deregister(&watchdog_miscdev);
1104                 old_wd_data = NULL;
1105         }
1106
1107         if (watchdog_active(wdd) &&
1108             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1109                 watchdog_stop(wdd);
1110         }
1111
1112         mutex_lock(&wd_data->lock);
1113         wd_data->wdd = NULL;
1114         wdd->wd_data = NULL;
1115         mutex_unlock(&wd_data->lock);
1116
1117         hrtimer_cancel(&wd_data->timer);
1118         kthread_cancel_work_sync(&wd_data->work);
1119
1120         put_device(&wd_data->dev);
1121 }
1122
1123 /*
1124  *      watchdog_dev_register: register a watchdog device
1125  *      @wdd: watchdog device
1126  *
1127  *      Register a watchdog device including handling the legacy
1128  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1129  *      thus we set it up like that.
1130  */
1131
1132 int watchdog_dev_register(struct watchdog_device *wdd)
1133 {
1134         int ret;
1135
1136         ret = watchdog_cdev_register(wdd);
1137         if (ret)
1138                 return ret;
1139
1140         ret = watchdog_register_pretimeout(wdd);
1141         if (ret)
1142                 watchdog_cdev_unregister(wdd);
1143
1144         return ret;
1145 }
1146
1147 /*
1148  *      watchdog_dev_unregister: unregister a watchdog device
1149  *      @watchdog: watchdog device
1150  *
1151  *      Unregister watchdog device and if needed the legacy
1152  *      /dev/watchdog device.
1153  */
1154
1155 void watchdog_dev_unregister(struct watchdog_device *wdd)
1156 {
1157         watchdog_unregister_pretimeout(wdd);
1158         watchdog_cdev_unregister(wdd);
1159 }
1160
1161 /*
1162  *      watchdog_set_last_hw_keepalive: set last HW keepalive time for watchdog
1163  *      @wdd: watchdog device
1164  *      @last_ping_ms: time since last HW heartbeat
1165  *
1166  *      Adjusts the last known HW keepalive time for a watchdog timer.
1167  *      This is needed if the watchdog is already running when the probe
1168  *      function is called, and it can't be pinged immediately. This
1169  *      function must be called immediately after watchdog registration,
1170  *      and min_hw_heartbeat_ms must be set for this to be useful.
1171  */
1172 int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
1173                                    unsigned int last_ping_ms)
1174 {
1175         struct watchdog_core_data *wd_data;
1176         ktime_t now;
1177
1178         if (!wdd)
1179                 return -EINVAL;
1180
1181         wd_data = wdd->wd_data;
1182
1183         now = ktime_get();
1184
1185         wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));
1186
1187         return __watchdog_ping(wdd);
1188 }
1189 EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);
1190
1191 /*
1192  *      watchdog_dev_init: init dev part of watchdog core
1193  *
1194  *      Allocate a range of chardev nodes to use for watchdog devices
1195  */
1196
1197 int __init watchdog_dev_init(void)
1198 {
1199         int err;
1200
1201         watchdog_kworker = kthread_create_worker(0, "watchdogd");
1202         if (IS_ERR(watchdog_kworker)) {
1203                 pr_err("Failed to create watchdog kworker\n");
1204                 return PTR_ERR(watchdog_kworker);
1205         }
1206         sched_set_fifo(watchdog_kworker->task);
1207
1208         err = class_register(&watchdog_class);
1209         if (err < 0) {
1210                 pr_err("couldn't register class\n");
1211                 goto err_register;
1212         }
1213
1214         err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1215         if (err < 0) {
1216                 pr_err("watchdog: unable to allocate char dev region\n");
1217                 goto err_alloc;
1218         }
1219
1220         return 0;
1221
1222 err_alloc:
1223         class_unregister(&watchdog_class);
1224 err_register:
1225         kthread_destroy_worker(watchdog_kworker);
1226         return err;
1227 }
1228
1229 /*
1230  *      watchdog_dev_exit: exit dev part of watchdog core
1231  *
1232  *      Release the range of chardev nodes used for watchdog devices
1233  */
1234
1235 void __exit watchdog_dev_exit(void)
1236 {
1237         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1238         class_unregister(&watchdog_class);
1239         kthread_destroy_worker(watchdog_kworker);
1240 }
1241
1242 module_param(handle_boot_enabled, bool, 0444);
1243 MODULE_PARM_DESC(handle_boot_enabled,
1244         "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1245         __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1246
1247 module_param(open_timeout, uint, 0644);
1248 MODULE_PARM_DESC(open_timeout,
1249         "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1250         __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");