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 pretimeout_show(struct device *dev,
 529                                struct device_attribute *attr, char *buf)
 530 {
 531         struct watchdog_device *wdd = dev_get_drvdata(dev);
 532
 533         return sprintf(buf, "%u\n", wdd->pretimeout);
 534 }
 535 static DEVICE_ATTR_RO(pretimeout);
 536
 537 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
 538                                 char *buf)
 539 {
 540         struct watchdog_device *wdd = dev_get_drvdata(dev);
 541
 542         return sprintf(buf, "%s\n", wdd->info->identity);
 543 }
 544 static DEVICE_ATTR_RO(identity);
 545
 546 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 547                                 char *buf)
 548 {
 549         struct watchdog_device *wdd = dev_get_drvdata(dev);
 550
 551         if (watchdog_active(wdd))
 552                 return sprintf(buf, "active\n");
 553
 554         return sprintf(buf, "inactive\n");
 555 }
 556 static DEVICE_ATTR_RO(state);
 557
 558 static ssize_t pretimeout_available_governors_show(struct device *dev,
 559                                    struct device_attribute *attr, char *buf)
 560 {
 561         return watchdog_pretimeout_available_governors_get(buf);
 562 }
 563 static DEVICE_ATTR_RO(pretimeout_available_governors);
 564
 565 static ssize_t pretimeout_governor_show(struct device *dev,
 566                                         struct device_attribute *attr,
 567                                         char *buf)
 568 {
 569         struct watchdog_device *wdd = dev_get_drvdata(dev);
 570
 571         return watchdog_pretimeout_governor_get(wdd, buf);
 572 }
 573
 574 static ssize_t pretimeout_governor_store(struct device *dev,
 575                                          struct device_attribute *attr,
 576                                          const char *buf, size_t count)
 577 {
 578         struct watchdog_device *wdd = dev_get_drvdata(dev);
 579         int ret = watchdog_pretimeout_governor_set(wdd, buf);
 580
 581         if (!ret)
 582                 ret = count;
 583
 584         return ret;
 585 }
 586 static DEVICE_ATTR_RW(pretimeout_governor);
 587
 588 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
 589                                 int n)
 590 {
 591         struct device *dev = kobj_to_dev(kobj);
 592         struct watchdog_device *wdd = dev_get_drvdata(dev);
 593         umode_t mode = attr->mode;
 594
 595         if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
 596                 mode = 0;
 597         else if (attr == &dev_attr_pretimeout.attr &&
 598                  !(wdd->info->options & WDIOF_PRETIMEOUT))
 599                 mode = 0;
 600         else if ((attr == &dev_attr_pretimeout_governor.attr ||
 601                   attr == &dev_attr_pretimeout_available_governors.attr) &&
 602                  (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
 603                   !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
 604                 mode = 0;
 605
 606         return mode;
 607 }
 608 static struct attribute *wdt_attrs[] = {
 609         &dev_attr_state.attr,
 610         &dev_attr_identity.attr,
 611         &dev_attr_timeout.attr,
 612         &dev_attr_pretimeout.attr,
 613         &dev_attr_timeleft.attr,
 614         &dev_attr_bootstatus.attr,
 615         &dev_attr_status.attr,
 616         &dev_attr_nowayout.attr,
 617         &dev_attr_pretimeout_governor.attr,
 618         &dev_attr_pretimeout_available_governors.attr,
 619         NULL,
 620 };
 621
 622 static const struct attribute_group wdt_group = {
 623         .attrs = wdt_attrs,
 624         .is_visible = wdt_is_visible,
 625 };
 626 __ATTRIBUTE_GROUPS(wdt);
 627 #else
 628 #define wdt_groups      NULL
 629 #endif
 630
 631 /*
 632  *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 633  *      @wdd: the watchdog device to do the ioctl on
 634  *      @cmd: watchdog command
 635  *      @arg: argument pointer
 636  *
 637  *      The caller must hold wd_data->lock.
 638  */
 639
 640 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
 641                                                         unsigned long arg)
 642 {
 643         if (!wdd->ops->ioctl)
 644                 return -ENOIOCTLCMD;
 645
 646         return wdd->ops->ioctl(wdd, cmd, arg);
 647 }
 648
 649 /*
 650  *      watchdog_write: writes to the watchdog.
 651  *      @file: file from VFS
 652  *      @data: user address of data
 653  *      @len: length of data
 654  *      @ppos: pointer to the file offset
 655  *
 656  *      A write to a watchdog device is defined as a keepalive ping.
 657  *      Writing the magic 'V' sequence allows the next close to turn
 658  *      off the watchdog (if 'nowayout' is not set).
 659  */
 660
 661 static ssize_t watchdog_write(struct file *file, const char __user *data,
 662                                                 size_t len, loff_t *ppos)
 663 {
 664         struct watchdog_core_data *wd_data = file->private_data;
 665         struct watchdog_device *wdd;
 666         int err;
 667         size_t i;
 668         char c;
 669
 670         if (len == 0)
 671                 return 0;
 672
 673         /*
 674          * Note: just in case someone wrote the magic character
 675          * five months ago...
 676          */
 677         clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 678
 679         /* scan to see whether or not we got the magic character */
 680         for (i = 0; i != len; i++) {
 681                 if (get_user(c, data + i))
 682                         return -EFAULT;
 683                 if (c == 'V')
 684                         set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 685         }
 686
 687         /* someone wrote to us, so we send the watchdog a keepalive ping */
 688
 689         err = -ENODEV;
 690         mutex_lock(&wd_data->lock);
 691         wdd = wd_data->wdd;
 692         if (wdd)
 693                 err = watchdog_ping(wdd);
 694         mutex_unlock(&wd_data->lock);
 695
 696         if (err < 0)
 697                 return err;
 698
 699         return len;
 700 }
 701
 702 /*
 703  *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 704  *      @file: file handle to the device
 705  *      @cmd: watchdog command
 706  *      @arg: argument pointer
 707  *
 708  *      The watchdog API defines a common set of functions for all watchdogs
 709  *      according to their available features.
 710  */
 711
 712 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 713                                                         unsigned long arg)
 714 {
 715         struct watchdog_core_data *wd_data = file->private_data;
 716         void __user *argp = (void __user *)arg;
 717         struct watchdog_device *wdd;
 718         int __user *p = argp;
 719         unsigned int val;
 720         int err;
 721
 722         mutex_lock(&wd_data->lock);
 723
 724         wdd = wd_data->wdd;
 725         if (!wdd) {
 726                 err = -ENODEV;
 727                 goto out_ioctl;
 728         }
 729
 730         err = watchdog_ioctl_op(wdd, cmd, arg);
 731         if (err != -ENOIOCTLCMD)
 732                 goto out_ioctl;
 733
 734         switch (cmd) {
 735         case WDIOC_GETSUPPORT:
 736                 err = copy_to_user(argp, wdd->info,
 737                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
 738                 break;
 739         case WDIOC_GETSTATUS:
 740                 val = watchdog_get_status(wdd);
 741                 err = put_user(val, p);
 742                 break;
 743         case WDIOC_GETBOOTSTATUS:
 744                 err = put_user(wdd->bootstatus, p);
 745                 break;
 746         case WDIOC_SETOPTIONS:
 747                 if (get_user(val, p)) {
 748                         err = -EFAULT;
 749                         break;
 750                 }
 751                 if (val & WDIOS_DISABLECARD) {
 752                         err = watchdog_stop(wdd);
 753                         if (err < 0)
 754                                 break;
 755                 }
 756                 if (val & WDIOS_ENABLECARD)
 757                         err = watchdog_start(wdd);
 758                 break;
 759         case WDIOC_KEEPALIVE:
 760                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
 761                         err = -EOPNOTSUPP;
 762                         break;
 763                 }
 764                 err = watchdog_ping(wdd);
 765                 break;
 766         case WDIOC_SETTIMEOUT:
 767                 if (get_user(val, p)) {
 768                         err = -EFAULT;
 769                         break;
 770                 }
 771                 err = watchdog_set_timeout(wdd, val);
 772                 if (err < 0)
 773                         break;
 774                 /* If the watchdog is active then we send a keepalive ping
 775                  * to make sure that the watchdog keep's running (and if
 776                  * possible that it takes the new timeout) */
 777                 err = watchdog_ping(wdd);
 778                 if (err < 0)
 779                         break;
 780                 fallthrough;
 781         case WDIOC_GETTIMEOUT:
 782                 /* timeout == 0 means that we don't know the timeout */
 783                 if (wdd->timeout == 0) {
 784                         err = -EOPNOTSUPP;
 785                         break;
 786                 }
 787                 err = put_user(wdd->timeout, p);
 788                 break;
 789         case WDIOC_GETTIMELEFT:
 790                 err = watchdog_get_timeleft(wdd, &val);
 791                 if (err < 0)
 792                         break;
 793                 err = put_user(val, p);
 794                 break;
 795         case WDIOC_SETPRETIMEOUT:
 796                 if (get_user(val, p)) {
 797                         err = -EFAULT;
 798                         break;
 799                 }
 800                 err = watchdog_set_pretimeout(wdd, val);
 801                 break;
 802         case WDIOC_GETPRETIMEOUT:
 803                 err = put_user(wdd->pretimeout, p);
 804                 break;
 805         default:
 806                 err = -ENOTTY;
 807                 break;
 808         }
 809
 810 out_ioctl:
 811         mutex_unlock(&wd_data->lock);
 812         return err;
 813 }
 814
 815 /*
 816  *      watchdog_open: open the /dev/watchdog* devices.
 817  *      @inode: inode of device
 818  *      @file: file handle to device
 819  *
 820  *      When the /dev/watchdog* device gets opened, we start the watchdog.
 821  *      Watch out: the /dev/watchdog device is single open, so we make sure
 822  *      it can only be opened once.
 823  */
 824
 825 static int watchdog_open(struct inode *inode, struct file *file)
 826 {
 827         struct watchdog_core_data *wd_data;
 828         struct watchdog_device *wdd;
 829         bool hw_running;
 830         int err;
 831
 832         /* Get the corresponding watchdog device */
 833         if (imajor(inode) == MISC_MAJOR)
 834                 wd_data = old_wd_data;
 835         else
 836                 wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
 837                                        cdev);
 838
 839         /* the watchdog is single open! */
 840         if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
 841                 return -EBUSY;
 842
 843         wdd = wd_data->wdd;
 844
 845         /*
 846          * If the /dev/watchdog device is open, we don't want the module
 847          * to be unloaded.
 848          */
 849         hw_running = watchdog_hw_running(wdd);
 850         if (!hw_running && !try_module_get(wdd->ops->owner)) {
 851                 err = -EBUSY;
 852                 goto out_clear;
 853         }
 854
 855         err = watchdog_start(wdd);
 856         if (err < 0)
 857                 goto out_mod;
 858
 859         file->private_data = wd_data;
 860
 861         if (!hw_running)
 862                 get_device(&wd_data->dev);
 863
 864         /*
 865          * open_timeout only applies for the first open from
 866          * userspace. Set open_deadline to infinity so that the kernel
 867          * will take care of an always-running hardware watchdog in
 868          * case the device gets magic-closed or WDIOS_DISABLECARD is
 869          * applied.
 870          */
 871         wd_data->open_deadline = KTIME_MAX;
 872
 873         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 874         return stream_open(inode, file);
 875
 876 out_mod:
 877         module_put(wd_data->wdd->ops->owner);
 878 out_clear:
 879         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 880         return err;
 881 }
 882
 883 static void watchdog_core_data_release(struct device *dev)
 884 {
 885         struct watchdog_core_data *wd_data;
 886
 887         wd_data = container_of(dev, struct watchdog_core_data, dev);
 888
 889         kfree(wd_data);
 890 }
 891
 892 /*
 893  *      watchdog_release: release the watchdog device.
 894  *      @inode: inode of device
 895  *      @file: file handle to device
 896  *
 897  *      This is the code for when /dev/watchdog gets closed. We will only
 898  *      stop the watchdog when we have received the magic char (and nowayout
 899  *      was not set), else the watchdog will keep running.
 900  */
 901
 902 static int watchdog_release(struct inode *inode, struct file *file)
 903 {
 904         struct watchdog_core_data *wd_data = file->private_data;
 905         struct watchdog_device *wdd;
 906         int err = -EBUSY;
 907         bool running;
 908
 909         mutex_lock(&wd_data->lock);
 910
 911         wdd = wd_data->wdd;
 912         if (!wdd)
 913                 goto done;
 914
 915         /*
 916          * We only stop the watchdog if we received the magic character
 917          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 918          * watchdog_stop will fail.
 919          */
 920         if (!watchdog_active(wdd))
 921                 err = 0;
 922         else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
 923                  !(wdd->info->options & WDIOF_MAGICCLOSE))
 924                 err = watchdog_stop(wdd);
 925
 926         /* If the watchdog was not stopped, send a keepalive ping */
 927         if (err < 0) {
 928                 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
 929                 watchdog_ping(wdd);
 930         }
 931
 932         watchdog_update_worker(wdd);
 933
 934         /* make sure that /dev/watchdog can be re-opened */
 935         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 936
 937 done:
 938         running = wdd && watchdog_hw_running(wdd);
 939         mutex_unlock(&wd_data->lock);
 940         /*
 941          * Allow the owner module to be unloaded again unless the watchdog
 942          * is still running. If the watchdog is still running, it can not
 943          * be stopped, and its driver must not be unloaded.
 944          */
 945         if (!running) {
 946                 module_put(wd_data->cdev.owner);
 947                 put_device(&wd_data->dev);
 948         }
 949         return 0;
 950 }
 951
 952 static const struct file_operations watchdog_fops = {
 953         .owner          = THIS_MODULE,
 954         .write          = watchdog_write,
 955         .unlocked_ioctl = watchdog_ioctl,
 956         .compat_ioctl   = compat_ptr_ioctl,
 957         .open           = watchdog_open,
 958         .release        = watchdog_release,
 959 };
 960
 961 static struct miscdevice watchdog_miscdev = {
 962         .minor          = WATCHDOG_MINOR,
 963         .name           = "watchdog",
 964         .fops           = &watchdog_fops,
 965 };
 966
 967 static struct class watchdog_class = {
 968         .name =         "watchdog",
 969         .owner =        THIS_MODULE,
 970         .dev_groups =   wdt_groups,
 971 };
 972
 973 /*
 974  *      watchdog_cdev_register: register watchdog character device
 975  *      @wdd: watchdog device
 976  *
 977  *      Register a watchdog character device including handling the legacy
 978  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 979  *      thus we set it up like that.
 980  */
 981
 982 static int watchdog_cdev_register(struct watchdog_device *wdd)
 983 {
 984         struct watchdog_core_data *wd_data;
 985         int err;
 986
 987         wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
 988         if (!wd_data)
 989                 return -ENOMEM;
 990         mutex_init(&wd_data->lock);
 991
 992         wd_data->wdd = wdd;
 993         wdd->wd_data = wd_data;
 994
 995         if (IS_ERR_OR_NULL(watchdog_kworker)) {
 996                 kfree(wd_data);
 997                 return -ENODEV;
 998         }
 999
1000         device_initialize(&wd_data->dev);
1001         wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
1002         wd_data->dev.class = &watchdog_class;
1003         wd_data->dev.parent = wdd->parent;
1004         wd_data->dev.groups = wdd->groups;
1005         wd_data->dev.release = watchdog_core_data_release;
1006         dev_set_drvdata(&wd_data->dev, wdd);
1007         dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
1008
1009         kthread_init_work(&wd_data->work, watchdog_ping_work);
1010         hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1011         wd_data->timer.function = watchdog_timer_expired;
1012
1013         if (wdd->id == 0) {
1014                 old_wd_data = wd_data;
1015                 watchdog_miscdev.parent = wdd->parent;
1016                 err = misc_register(&watchdog_miscdev);
1017                 if (err != 0) {
1018                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
1019                                 wdd->info->identity, WATCHDOG_MINOR, err);
1020                         if (err == -EBUSY)
1021                                 pr_err("%s: a legacy watchdog module is probably present.\n",
1022                                         wdd->info->identity);
1023                         old_wd_data = NULL;
1024                         put_device(&wd_data->dev);
1025                         return err;
1026                 }
1027         }
1028
1029         /* Fill in the data structures */
1030         cdev_init(&wd_data->cdev, &watchdog_fops);
1031
1032         /* Add the device */
1033         err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1034         if (err) {
1035                 pr_err("watchdog%d unable to add device %d:%d\n",
1036                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
1037                 if (wdd->id == 0) {
1038                         misc_deregister(&watchdog_miscdev);
1039                         old_wd_data = NULL;
1040                         put_device(&wd_data->dev);
1041                 }
1042                 return err;
1043         }
1044
1045         wd_data->cdev.owner = wdd->ops->owner;
1046
1047         /* Record time of most recent heartbeat as 'just before now'. */
1048         wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1049         watchdog_set_open_deadline(wd_data);
1050
1051         /*
1052          * If the watchdog is running, prevent its driver from being unloaded,
1053          * and schedule an immediate ping.
1054          */
1055         if (watchdog_hw_running(wdd)) {
1056                 __module_get(wdd->ops->owner);
1057                 get_device(&wd_data->dev);
1058                 if (handle_boot_enabled)
1059                         hrtimer_start(&wd_data->timer, 0,
1060                                       HRTIMER_MODE_REL_HARD);
1061                 else
1062                         pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1063                                 wdd->id);
1064         }
1065
1066         return 0;
1067 }
1068
1069 /*
1070  *      watchdog_cdev_unregister: unregister watchdog character device
1071  *      @watchdog: watchdog device
1072  *
1073  *      Unregister watchdog character device and if needed the legacy
1074  *      /dev/watchdog device.
1075  */
1076
1077 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1078 {
1079         struct watchdog_core_data *wd_data = wdd->wd_data;
1080
1081         cdev_device_del(&wd_data->cdev, &wd_data->dev);
1082         if (wdd->id == 0) {
1083                 misc_deregister(&watchdog_miscdev);
1084                 old_wd_data = NULL;
1085         }
1086
1087         if (watchdog_active(wdd) &&
1088             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1089                 watchdog_stop(wdd);
1090         }
1091
1092         mutex_lock(&wd_data->lock);
1093         wd_data->wdd = NULL;
1094         wdd->wd_data = NULL;
1095         mutex_unlock(&wd_data->lock);
1096
1097         hrtimer_cancel(&wd_data->timer);
1098         kthread_cancel_work_sync(&wd_data->work);
1099
1100         put_device(&wd_data->dev);
1101 }
1102
1103 /*
1104  *      watchdog_dev_register: register a watchdog device
1105  *      @wdd: watchdog device
1106  *
1107  *      Register a watchdog device including handling the legacy
1108  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1109  *      thus we set it up like that.
1110  */
1111
1112 int watchdog_dev_register(struct watchdog_device *wdd)
1113 {
1114         int ret;
1115
1116         ret = watchdog_cdev_register(wdd);
1117         if (ret)
1118                 return ret;
1119
1120         ret = watchdog_register_pretimeout(wdd);
1121         if (ret)
1122                 watchdog_cdev_unregister(wdd);
1123
1124         return ret;
1125 }
1126
1127 /*
1128  *      watchdog_dev_unregister: unregister a watchdog device
1129  *      @watchdog: watchdog device
1130  *
1131  *      Unregister watchdog device and if needed the legacy
1132  *      /dev/watchdog device.
1133  */
1134
1135 void watchdog_dev_unregister(struct watchdog_device *wdd)
1136 {
1137         watchdog_unregister_pretimeout(wdd);
1138         watchdog_cdev_unregister(wdd);
1139 }
1140
1141 /*
1142  *      watchdog_set_last_hw_keepalive: set last HW keepalive time for watchdog
1143  *      @wdd: watchdog device
1144  *      @last_ping_ms: time since last HW heartbeat
1145  *
1146  *      Adjusts the last known HW keepalive time for a watchdog timer.
1147  *      This is needed if the watchdog is already running when the probe
1148  *      function is called, and it can't be pinged immediately. This
1149  *      function must be called immediately after watchdog registration,
1150  *      and min_hw_heartbeat_ms must be set for this to be useful.
1151  */
1152 int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
1153                                    unsigned int last_ping_ms)
1154 {
1155         struct watchdog_core_data *wd_data;
1156         ktime_t now;
1157
1158         if (!wdd)
1159                 return -EINVAL;
1160
1161         wd_data = wdd->wd_data;
1162
1163         now = ktime_get();
1164
1165         wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));
1166
1167         return __watchdog_ping(wdd);
1168 }
1169 EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);
1170
1171 /*
1172  *      watchdog_dev_init: init dev part of watchdog core
1173  *
1174  *      Allocate a range of chardev nodes to use for watchdog devices
1175  */
1176
1177 int __init watchdog_dev_init(void)
1178 {
1179         int err;
1180
1181         watchdog_kworker = kthread_create_worker(0, "watchdogd");
1182         if (IS_ERR(watchdog_kworker)) {
1183                 pr_err("Failed to create watchdog kworker\n");
1184                 return PTR_ERR(watchdog_kworker);
1185         }
1186         sched_set_fifo(watchdog_kworker->task);
1187
1188         err = class_register(&watchdog_class);
1189         if (err < 0) {
1190                 pr_err("couldn't register class\n");
1191                 goto err_register;
1192         }
1193
1194         err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1195         if (err < 0) {
1196                 pr_err("watchdog: unable to allocate char dev region\n");
1197                 goto err_alloc;
1198         }
1199
1200         return 0;
1201
1202 err_alloc:
1203         class_unregister(&watchdog_class);
1204 err_register:
1205         kthread_destroy_worker(watchdog_kworker);
1206         return err;
1207 }
1208
1209 /*
1210  *      watchdog_dev_exit: exit dev part of watchdog core
1211  *
1212  *      Release the range of chardev nodes used for watchdog devices
1213  */
1214
1215 void __exit watchdog_dev_exit(void)
1216 {
1217         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1218         class_unregister(&watchdog_class);
1219         kthread_destroy_worker(watchdog_kworker);
1220 }
1221
1222 module_param(handle_boot_enabled, bool, 0444);
1223 MODULE_PARM_DESC(handle_boot_enabled,
1224         "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1225         __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1226
1227 module_param(open_timeout, uint, 0644);
1228 MODULE_PARM_DESC(open_timeout,
1229         "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1230         __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");