drivers/watchdog/watchdog_dev.c

   1 /*
   2  *      watchdog_dev.c
   3  *
   4  *      (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   5  *                                              All Rights Reserved.
   6  *
   7  *      (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
   8  *
   9  *
  10  *      This source code is part of the generic code that can be used
  11  *      by all the watchdog timer drivers.
  12  *
  13  *      This part of the generic code takes care of the following
  14  *      misc device: /dev/watchdog.
  15  *
  16  *      Based on source code of the following authors:
  17  *        Matt Domsch <Matt_Domsch@dell.com>,
  18  *        Rob Radez <rob@osinvestor.com>,
  19  *        Rusty Lynch <rusty@linux.co.intel.com>
  20  *        Satyam Sharma <satyam@infradead.org>
  21  *        Randy Dunlap <randy.dunlap@oracle.com>
  22  *
  23  *      This program is free software; you can redistribute it and/or
  24  *      modify it under the terms of the GNU General Public License
  25  *      as published by the Free Software Foundation; either version
  26  *      2 of the License, or (at your option) any later version.
  27  *
  28  *      Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
  29  *      admit liability nor provide warranty for any of this software.
  30  *      This material is provided "AS-IS" and at no charge.
  31  */
  32
  33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  34
  35 #include <linux/cdev.h>         /* For character device */
  36 #include <linux/errno.h>        /* For the -ENODEV/... values */
  37 #include <linux/fs.h>           /* For file operations */
  38 #include <linux/init.h>         /* For __init/__exit/... */
  39 #include <linux/hrtimer.h>      /* For hrtimers */
  40 #include <linux/kernel.h>       /* For printk/panic/... */
  41 #include <linux/kref.h>         /* For data references */
  42 #include <linux/kthread.h>      /* For kthread_work */
  43 #include <linux/miscdevice.h>   /* For handling misc devices */
  44 #include <linux/module.h>       /* For module stuff/... */
  45 #include <linux/mutex.h>        /* For mutexes */
  46 #include <linux/reboot.h>       /* For reboot notifier */
  47 #include <linux/slab.h>         /* For memory functions */
  48 #include <linux/types.h>        /* For standard types (like size_t) */
  49 #include <linux/watchdog.h>     /* For watchdog specific items */
  50 #include <linux/uaccess.h>      /* For copy_to_user/put_user/... */
  51
  52 #include <uapi/linux/sched/types.h>     /* For struct sched_param */
  53
  54 #include "watchdog_core.h"
  55 #include "watchdog_pretimeout.h"
  56
  57 /*
  58  * struct watchdog_core_data - watchdog core internal data
  59  * @kref:       Reference count.
  60  * @cdev:       The watchdog's Character device.
  61  * @wdd:        Pointer to watchdog device.
  62  * @lock:       Lock for watchdog core.
  63  * @status:     Watchdog core internal status bits.
  64  */
  65 struct watchdog_core_data {
  66         struct kref kref;
  67         struct cdev cdev;
  68         struct watchdog_device *wdd;
  69         struct mutex lock;
  70         ktime_t last_keepalive;
  71         ktime_t last_hw_keepalive;
  72         struct hrtimer timer;
  73         struct kthread_work work;
  74         unsigned long status;           /* Internal status bits */
  75 #define _WDOG_DEV_OPEN          0       /* Opened ? */
  76 #define _WDOG_ALLOW_RELEASE     1       /* Did we receive the magic char ? */
  77 #define _WDOG_KEEPALIVE         2       /* Did we receive a keepalive ? */
  78 };
  79
  80 /* the dev_t structure to store the dynamically allocated watchdog devices */
  81 static dev_t watchdog_devt;
  82 /* Reference to watchdog device behind /dev/watchdog */
  83 static struct watchdog_core_data *old_wd_data;
  84
  85 static struct kthread_worker *watchdog_kworker;
  86
  87 static bool handle_boot_enabled =
  88         IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
  89
  90 static inline bool watchdog_need_worker(struct watchdog_device *wdd)
  91 {
  92         /* All variables in milli-seconds */
  93         unsigned int hm = wdd->max_hw_heartbeat_ms;
  94         unsigned int t = wdd->timeout * 1000;
  95
  96         /*
  97          * A worker to generate heartbeat requests is needed if all of the
  98          * following conditions are true.
  99          * - Userspace activated the watchdog.
 100          * - The driver provided a value for the maximum hardware timeout, and
 101          *   thus is aware that the framework supports generating heartbeat
 102          *   requests.
 103          * - Userspace requests a longer timeout than the hardware can handle.
 104          *
 105          * Alternatively, if userspace has not opened the watchdog
 106          * device, we take care of feeding the watchdog if it is
 107          * running.
 108          */
 109         return (hm && watchdog_active(wdd) && t > hm) ||
 110                 (t && !watchdog_active(wdd) && watchdog_hw_running(wdd));
 111 }
 112
 113 static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
 114 {
 115         struct watchdog_core_data *wd_data = wdd->wd_data;
 116         unsigned int timeout_ms = wdd->timeout * 1000;
 117         ktime_t keepalive_interval;
 118         ktime_t last_heartbeat, latest_heartbeat;
 119         ktime_t virt_timeout;
 120         unsigned int hw_heartbeat_ms;
 121
 122         virt_timeout = ktime_add(wd_data->last_keepalive,
 123                                  ms_to_ktime(timeout_ms));
 124         hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms);
 125         keepalive_interval = ms_to_ktime(hw_heartbeat_ms / 2);
 126
 127         if (!watchdog_active(wdd))
 128                 return keepalive_interval;
 129
 130         /*
 131          * To ensure that the watchdog times out wdd->timeout seconds
 132          * after the most recent ping from userspace, the last
 133          * worker ping has to come in hw_heartbeat_ms before this timeout.
 134          */
 135         last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms));
 136         latest_heartbeat = ktime_sub(last_heartbeat, ktime_get());
 137         if (ktime_before(latest_heartbeat, keepalive_interval))
 138                 return latest_heartbeat;
 139         return keepalive_interval;
 140 }
 141
 142 static inline void watchdog_update_worker(struct watchdog_device *wdd)
 143 {
 144         struct watchdog_core_data *wd_data = wdd->wd_data;
 145
 146         if (watchdog_need_worker(wdd)) {
 147                 ktime_t t = watchdog_next_keepalive(wdd);
 148
 149                 if (t > 0)
 150                         hrtimer_start(&wd_data->timer, t, HRTIMER_MODE_REL);
 151         } else {
 152                 hrtimer_cancel(&wd_data->timer);
 153         }
 154 }
 155
 156 static int __watchdog_ping(struct watchdog_device *wdd)
 157 {
 158         struct watchdog_core_data *wd_data = wdd->wd_data;
 159         ktime_t earliest_keepalive, now;
 160         int err;
 161
 162         earliest_keepalive = ktime_add(wd_data->last_hw_keepalive,
 163                                        ms_to_ktime(wdd->min_hw_heartbeat_ms));
 164         now = ktime_get();
 165
 166         if (ktime_after(earliest_keepalive, now)) {
 167                 hrtimer_start(&wd_data->timer,
 168                               ktime_sub(earliest_keepalive, now),
 169                               HRTIMER_MODE_REL);
 170                 return 0;
 171         }
 172
 173         wd_data->last_hw_keepalive = now;
 174
 175         if (wdd->ops->ping)
 176                 err = wdd->ops->ping(wdd);  /* ping the watchdog */
 177         else
 178                 err = wdd->ops->start(wdd); /* restart watchdog */
 179
 180         watchdog_update_worker(wdd);
 181
 182         return err;
 183 }
 184
 185 /*
 186  *      watchdog_ping: ping the watchdog.
 187  *      @wdd: the watchdog device to ping
 188  *
 189  *      The caller must hold wd_data->lock.
 190  *
 191  *      If the watchdog has no own ping operation then it needs to be
 192  *      restarted via the start operation. This wrapper function does
 193  *      exactly that.
 194  *      We only ping when the watchdog device is running.
 195  */
 196
 197 static int watchdog_ping(struct watchdog_device *wdd)
 198 {
 199         struct watchdog_core_data *wd_data = wdd->wd_data;
 200
 201         if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
 202                 return 0;
 203
 204         set_bit(_WDOG_KEEPALIVE, &wd_data->status);
 205
 206         wd_data->last_keepalive = ktime_get();
 207         return __watchdog_ping(wdd);
 208 }
 209
 210 static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data)
 211 {
 212         struct watchdog_device *wdd = wd_data->wdd;
 213
 214         return wdd && (watchdog_active(wdd) || watchdog_hw_running(wdd));
 215 }
 216
 217 static void watchdog_ping_work(struct kthread_work *work)
 218 {
 219         struct watchdog_core_data *wd_data;
 220
 221         wd_data = container_of(work, struct watchdog_core_data, work);
 222
 223         mutex_lock(&wd_data->lock);
 224         if (watchdog_worker_should_ping(wd_data))
 225                 __watchdog_ping(wd_data->wdd);
 226         mutex_unlock(&wd_data->lock);
 227 }
 228
 229 static enum hrtimer_restart watchdog_timer_expired(struct hrtimer *timer)
 230 {
 231         struct watchdog_core_data *wd_data;
 232
 233         wd_data = container_of(timer, struct watchdog_core_data, timer);
 234
 235         kthread_queue_work(watchdog_kworker, &wd_data->work);
 236         return HRTIMER_NORESTART;
 237 }
 238
 239 /*
 240  *      watchdog_start: wrapper to start the watchdog.
 241  *      @wdd: the watchdog device to start
 242  *
 243  *      The caller must hold wd_data->lock.
 244  *
 245  *      Start the watchdog if it is not active and mark it active.
 246  *      This function returns zero on success or a negative errno code for
 247  *      failure.
 248  */
 249
 250 static int watchdog_start(struct watchdog_device *wdd)
 251 {
 252         struct watchdog_core_data *wd_data = wdd->wd_data;
 253         ktime_t started_at;
 254         int err;
 255
 256         if (watchdog_active(wdd))
 257                 return 0;
 258
 259         set_bit(_WDOG_KEEPALIVE, &wd_data->status);
 260
 261         started_at = ktime_get();
 262         if (watchdog_hw_running(wdd) && wdd->ops->ping)
 263                 err = wdd->ops->ping(wdd);
 264         else
 265                 err = wdd->ops->start(wdd);
 266         if (err == 0) {
 267                 set_bit(WDOG_ACTIVE, &wdd->status);
 268                 wd_data->last_keepalive = started_at;
 269                 watchdog_update_worker(wdd);
 270         }
 271
 272         return err;
 273 }
 274
 275 /*
 276  *      watchdog_stop: wrapper to stop the watchdog.
 277  *      @wdd: the watchdog device to stop
 278  *
 279  *      The caller must hold wd_data->lock.
 280  *
 281  *      Stop the watchdog if it is still active and unmark it active.
 282  *      This function returns zero on success or a negative errno code for
 283  *      failure.
 284  *      If the 'nowayout' feature was set, the watchdog cannot be stopped.
 285  */
 286
 287 static int watchdog_stop(struct watchdog_device *wdd)
 288 {
 289         int err = 0;
 290
 291         if (!watchdog_active(wdd))
 292                 return 0;
 293
 294         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
 295                 pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
 296                         wdd->id);
 297                 return -EBUSY;
 298         }
 299
 300         if (wdd->ops->stop) {
 301                 clear_bit(WDOG_HW_RUNNING, &wdd->status);
 302                 err = wdd->ops->stop(wdd);
 303         } else {
 304                 set_bit(WDOG_HW_RUNNING, &wdd->status);
 305         }
 306
 307         if (err == 0) {
 308                 clear_bit(WDOG_ACTIVE, &wdd->status);
 309                 watchdog_update_worker(wdd);
 310         }
 311
 312         return err;
 313 }
 314
 315 /*
 316  *      watchdog_get_status: wrapper to get the watchdog status
 317  *      @wdd: the watchdog device to get the status from
 318  *
 319  *      The caller must hold wd_data->lock.
 320  *
 321  *      Get the watchdog's status flags.
 322  */
 323
 324 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
 325 {
 326         struct watchdog_core_data *wd_data = wdd->wd_data;
 327         unsigned int status;
 328
 329         if (wdd->ops->status)
 330                 status = wdd->ops->status(wdd);
 331         else
 332                 status = wdd->bootstatus & (WDIOF_CARDRESET |
 333                                             WDIOF_OVERHEAT |
 334                                             WDIOF_FANFAULT |
 335                                             WDIOF_EXTERN1 |
 336                                             WDIOF_EXTERN2 |
 337                                             WDIOF_POWERUNDER |
 338                                             WDIOF_POWEROVER);
 339
 340         if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
 341                 status |= WDIOF_MAGICCLOSE;
 342
 343         if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
 344                 status |= WDIOF_KEEPALIVEPING;
 345
 346         return status;
 347 }
 348
 349 /*
 350  *      watchdog_set_timeout: set the watchdog timer timeout
 351  *      @wdd: the watchdog device to set the timeout for
 352  *      @timeout: timeout to set in seconds
 353  *
 354  *      The caller must hold wd_data->lock.
 355  */
 356
 357 static int watchdog_set_timeout(struct watchdog_device *wdd,
 358                                                         unsigned int timeout)
 359 {
 360         int err = 0;
 361
 362         if (!(wdd->info->options & WDIOF_SETTIMEOUT))
 363                 return -EOPNOTSUPP;
 364
 365         if (watchdog_timeout_invalid(wdd, timeout))
 366                 return -EINVAL;
 367
 368         if (wdd->ops->set_timeout) {
 369                 err = wdd->ops->set_timeout(wdd, timeout);
 370         } else {
 371                 wdd->timeout = timeout;
 372                 /* Disable pretimeout if it doesn't fit the new timeout */
 373                 if (wdd->pretimeout >= wdd->timeout)
 374                         wdd->pretimeout = 0;
 375         }
 376
 377         watchdog_update_worker(wdd);
 378
 379         return err;
 380 }
 381
 382 /*
 383  *      watchdog_set_pretimeout: set the watchdog timer pretimeout
 384  *      @wdd: the watchdog device to set the timeout for
 385  *      @timeout: pretimeout to set in seconds
 386  */
 387
 388 static int watchdog_set_pretimeout(struct watchdog_device *wdd,
 389                                    unsigned int timeout)
 390 {
 391         int err = 0;
 392
 393         if (!(wdd->info->options & WDIOF_PRETIMEOUT))
 394                 return -EOPNOTSUPP;
 395
 396         if (watchdog_pretimeout_invalid(wdd, timeout))
 397                 return -EINVAL;
 398
 399         if (wdd->ops->set_pretimeout)
 400                 err = wdd->ops->set_pretimeout(wdd, timeout);
 401         else
 402                 wdd->pretimeout = timeout;
 403
 404         return err;
 405 }
 406
 407 /*
 408  *      watchdog_get_timeleft: wrapper to get the time left before a reboot
 409  *      @wdd: the watchdog device to get the remaining time from
 410  *      @timeleft: the time that's left
 411  *
 412  *      The caller must hold wd_data->lock.
 413  *
 414  *      Get the time before a watchdog will reboot (if not pinged).
 415  */
 416
 417 static int watchdog_get_timeleft(struct watchdog_device *wdd,
 418                                                         unsigned int *timeleft)
 419 {
 420         *timeleft = 0;
 421
 422         if (!wdd->ops->get_timeleft)
 423                 return -EOPNOTSUPP;
 424
 425         *timeleft = wdd->ops->get_timeleft(wdd);
 426
 427         return 0;
 428 }
 429
 430 #ifdef CONFIG_WATCHDOG_SYSFS
 431 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
 432                                 char *buf)
 433 {
 434         struct watchdog_device *wdd = dev_get_drvdata(dev);
 435
 436         return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
 437 }
 438 static DEVICE_ATTR_RO(nowayout);
 439
 440 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
 441                                 char *buf)
 442 {
 443         struct watchdog_device *wdd = dev_get_drvdata(dev);
 444         struct watchdog_core_data *wd_data = wdd->wd_data;
 445         unsigned int status;
 446
 447         mutex_lock(&wd_data->lock);
 448         status = watchdog_get_status(wdd);
 449         mutex_unlock(&wd_data->lock);
 450
 451         return sprintf(buf, "0x%x\n", status);
 452 }
 453 static DEVICE_ATTR_RO(status);
 454
 455 static ssize_t bootstatus_show(struct device *dev,
 456                                 struct device_attribute *attr, char *buf)
 457 {
 458         struct watchdog_device *wdd = dev_get_drvdata(dev);
 459
 460         return sprintf(buf, "%u\n", wdd->bootstatus);
 461 }
 462 static DEVICE_ATTR_RO(bootstatus);
 463
 464 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
 465                                 char *buf)
 466 {
 467         struct watchdog_device *wdd = dev_get_drvdata(dev);
 468         struct watchdog_core_data *wd_data = wdd->wd_data;
 469         ssize_t status;
 470         unsigned int val;
 471
 472         mutex_lock(&wd_data->lock);
 473         status = watchdog_get_timeleft(wdd, &val);
 474         mutex_unlock(&wd_data->lock);
 475         if (!status)
 476                 status = sprintf(buf, "%u\n", val);
 477
 478         return status;
 479 }
 480 static DEVICE_ATTR_RO(timeleft);
 481
 482 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
 483                                 char *buf)
 484 {
 485         struct watchdog_device *wdd = dev_get_drvdata(dev);
 486
 487         return sprintf(buf, "%u\n", wdd->timeout);
 488 }
 489 static DEVICE_ATTR_RO(timeout);
 490
 491 static ssize_t pretimeout_show(struct device *dev,
 492                                struct device_attribute *attr, char *buf)
 493 {
 494         struct watchdog_device *wdd = dev_get_drvdata(dev);
 495
 496         return sprintf(buf, "%u\n", wdd->pretimeout);
 497 }
 498 static DEVICE_ATTR_RO(pretimeout);
 499
 500 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
 501                                 char *buf)
 502 {
 503         struct watchdog_device *wdd = dev_get_drvdata(dev);
 504
 505         return sprintf(buf, "%s\n", wdd->info->identity);
 506 }
 507 static DEVICE_ATTR_RO(identity);
 508
 509 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 510                                 char *buf)
 511 {
 512         struct watchdog_device *wdd = dev_get_drvdata(dev);
 513
 514         if (watchdog_active(wdd))
 515                 return sprintf(buf, "active\n");
 516
 517         return sprintf(buf, "inactive\n");
 518 }
 519 static DEVICE_ATTR_RO(state);
 520
 521 static ssize_t pretimeout_available_governors_show(struct device *dev,
 522                                    struct device_attribute *attr, char *buf)
 523 {
 524         return watchdog_pretimeout_available_governors_get(buf);
 525 }
 526 static DEVICE_ATTR_RO(pretimeout_available_governors);
 527
 528 static ssize_t pretimeout_governor_show(struct device *dev,
 529                                         struct device_attribute *attr,
 530                                         char *buf)
 531 {
 532         struct watchdog_device *wdd = dev_get_drvdata(dev);
 533
 534         return watchdog_pretimeout_governor_get(wdd, buf);
 535 }
 536
 537 static ssize_t pretimeout_governor_store(struct device *dev,
 538                                          struct device_attribute *attr,
 539                                          const char *buf, size_t count)
 540 {
 541         struct watchdog_device *wdd = dev_get_drvdata(dev);
 542         int ret = watchdog_pretimeout_governor_set(wdd, buf);
 543
 544         if (!ret)
 545                 ret = count;
 546
 547         return ret;
 548 }
 549 static DEVICE_ATTR_RW(pretimeout_governor);
 550
 551 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
 552                                 int n)
 553 {
 554         struct device *dev = container_of(kobj, struct device, kobj);
 555         struct watchdog_device *wdd = dev_get_drvdata(dev);
 556         umode_t mode = attr->mode;
 557
 558         if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
 559                 mode = 0;
 560         else if (attr == &dev_attr_pretimeout.attr &&
 561                  !(wdd->info->options & WDIOF_PRETIMEOUT))
 562                 mode = 0;
 563         else if ((attr == &dev_attr_pretimeout_governor.attr ||
 564                   attr == &dev_attr_pretimeout_available_governors.attr) &&
 565                  (!(wdd->info->options & WDIOF_PRETIMEOUT) ||
 566                   !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
 567                 mode = 0;
 568
 569         return mode;
 570 }
 571 static struct attribute *wdt_attrs[] = {
 572         &dev_attr_state.attr,
 573         &dev_attr_identity.attr,
 574         &dev_attr_timeout.attr,
 575         &dev_attr_pretimeout.attr,
 576         &dev_attr_timeleft.attr,
 577         &dev_attr_bootstatus.attr,
 578         &dev_attr_status.attr,
 579         &dev_attr_nowayout.attr,
 580         &dev_attr_pretimeout_governor.attr,
 581         &dev_attr_pretimeout_available_governors.attr,
 582         NULL,
 583 };
 584
 585 static const struct attribute_group wdt_group = {
 586         .attrs = wdt_attrs,
 587         .is_visible = wdt_is_visible,
 588 };
 589 __ATTRIBUTE_GROUPS(wdt);
 590 #else
 591 #define wdt_groups      NULL
 592 #endif
 593
 594 /*
 595  *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 596  *      @wdd: the watchdog device to do the ioctl on
 597  *      @cmd: watchdog command
 598  *      @arg: argument pointer
 599  *
 600  *      The caller must hold wd_data->lock.
 601  */
 602
 603 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
 604                                                         unsigned long arg)
 605 {
 606         if (!wdd->ops->ioctl)
 607                 return -ENOIOCTLCMD;
 608
 609         return wdd->ops->ioctl(wdd, cmd, arg);
 610 }
 611
 612 /*
 613  *      watchdog_write: writes to the watchdog.
 614  *      @file: file from VFS
 615  *      @data: user address of data
 616  *      @len: length of data
 617  *      @ppos: pointer to the file offset
 618  *
 619  *      A write to a watchdog device is defined as a keepalive ping.
 620  *      Writing the magic 'V' sequence allows the next close to turn
 621  *      off the watchdog (if 'nowayout' is not set).
 622  */
 623
 624 static ssize_t watchdog_write(struct file *file, const char __user *data,
 625                                                 size_t len, loff_t *ppos)
 626 {
 627         struct watchdog_core_data *wd_data = file->private_data;
 628         struct watchdog_device *wdd;
 629         int err;
 630         size_t i;
 631         char c;
 632
 633         if (len == 0)
 634                 return 0;
 635
 636         /*
 637          * Note: just in case someone wrote the magic character
 638          * five months ago...
 639          */
 640         clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 641
 642         /* scan to see whether or not we got the magic character */
 643         for (i = 0; i != len; i++) {
 644                 if (get_user(c, data + i))
 645                         return -EFAULT;
 646                 if (c == 'V')
 647                         set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 648         }
 649
 650         /* someone wrote to us, so we send the watchdog a keepalive ping */
 651
 652         err = -ENODEV;
 653         mutex_lock(&wd_data->lock);
 654         wdd = wd_data->wdd;
 655         if (wdd)
 656                 err = watchdog_ping(wdd);
 657         mutex_unlock(&wd_data->lock);
 658
 659         if (err < 0)
 660                 return err;
 661
 662         return len;
 663 }
 664
 665 /*
 666  *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 667  *      @file: file handle to the device
 668  *      @cmd: watchdog command
 669  *      @arg: argument pointer
 670  *
 671  *      The watchdog API defines a common set of functions for all watchdogs
 672  *      according to their available features.
 673  */
 674
 675 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 676                                                         unsigned long arg)
 677 {
 678         struct watchdog_core_data *wd_data = file->private_data;
 679         void __user *argp = (void __user *)arg;
 680         struct watchdog_device *wdd;
 681         int __user *p = argp;
 682         unsigned int val;
 683         int err;
 684
 685         mutex_lock(&wd_data->lock);
 686
 687         wdd = wd_data->wdd;
 688         if (!wdd) {
 689                 err = -ENODEV;
 690                 goto out_ioctl;
 691         }
 692
 693         err = watchdog_ioctl_op(wdd, cmd, arg);
 694         if (err != -ENOIOCTLCMD)
 695                 goto out_ioctl;
 696
 697         switch (cmd) {
 698         case WDIOC_GETSUPPORT:
 699                 err = copy_to_user(argp, wdd->info,
 700                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
 701                 break;
 702         case WDIOC_GETSTATUS:
 703                 val = watchdog_get_status(wdd);
 704                 err = put_user(val, p);
 705                 break;
 706         case WDIOC_GETBOOTSTATUS:
 707                 err = put_user(wdd->bootstatus, p);
 708                 break;
 709         case WDIOC_SETOPTIONS:
 710                 if (get_user(val, p)) {
 711                         err = -EFAULT;
 712                         break;
 713                 }
 714                 if (val & WDIOS_DISABLECARD) {
 715                         err = watchdog_stop(wdd);
 716                         if (err < 0)
 717                                 break;
 718                 }
 719                 if (val & WDIOS_ENABLECARD)
 720                         err = watchdog_start(wdd);
 721                 break;
 722         case WDIOC_KEEPALIVE:
 723                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
 724                         err = -EOPNOTSUPP;
 725                         break;
 726                 }
 727                 err = watchdog_ping(wdd);
 728                 break;
 729         case WDIOC_SETTIMEOUT:
 730                 if (get_user(val, p)) {
 731                         err = -EFAULT;
 732                         break;
 733                 }
 734                 err = watchdog_set_timeout(wdd, val);
 735                 if (err < 0)
 736                         break;
 737                 /* If the watchdog is active then we send a keepalive ping
 738                  * to make sure that the watchdog keep's running (and if
 739                  * possible that it takes the new timeout) */
 740                 err = watchdog_ping(wdd);
 741                 if (err < 0)
 742                         break;
 743                 /* fall through */
 744         case WDIOC_GETTIMEOUT:
 745                 /* timeout == 0 means that we don't know the timeout */
 746                 if (wdd->timeout == 0) {
 747                         err = -EOPNOTSUPP;
 748                         break;
 749                 }
 750                 err = put_user(wdd->timeout, p);
 751                 break;
 752         case WDIOC_GETTIMELEFT:
 753                 err = watchdog_get_timeleft(wdd, &val);
 754                 if (err < 0)
 755                         break;
 756                 err = put_user(val, p);
 757                 break;
 758         case WDIOC_SETPRETIMEOUT:
 759                 if (get_user(val, p)) {
 760                         err = -EFAULT;
 761                         break;
 762                 }
 763                 err = watchdog_set_pretimeout(wdd, val);
 764                 break;
 765         case WDIOC_GETPRETIMEOUT:
 766                 err = put_user(wdd->pretimeout, p);
 767                 break;
 768         default:
 769                 err = -ENOTTY;
 770                 break;
 771         }
 772
 773 out_ioctl:
 774         mutex_unlock(&wd_data->lock);
 775         return err;
 776 }
 777
 778 /*
 779  *      watchdog_open: open the /dev/watchdog* devices.
 780  *      @inode: inode of device
 781  *      @file: file handle to device
 782  *
 783  *      When the /dev/watchdog* device gets opened, we start the watchdog.
 784  *      Watch out: the /dev/watchdog device is single open, so we make sure
 785  *      it can only be opened once.
 786  */
 787
 788 static int watchdog_open(struct inode *inode, struct file *file)
 789 {
 790         struct watchdog_core_data *wd_data;
 791         struct watchdog_device *wdd;
 792         bool hw_running;
 793         int err;
 794
 795         /* Get the corresponding watchdog device */
 796         if (imajor(inode) == MISC_MAJOR)
 797                 wd_data = old_wd_data;
 798         else
 799                 wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
 800                                        cdev);
 801
 802         /* the watchdog is single open! */
 803         if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
 804                 return -EBUSY;
 805
 806         wdd = wd_data->wdd;
 807
 808         /*
 809          * If the /dev/watchdog device is open, we don't want the module
 810          * to be unloaded.
 811          */
 812         hw_running = watchdog_hw_running(wdd);
 813         if (!hw_running && !try_module_get(wdd->ops->owner)) {
 814                 err = -EBUSY;
 815                 goto out_clear;
 816         }
 817
 818         err = watchdog_start(wdd);
 819         if (err < 0)
 820                 goto out_mod;
 821
 822         file->private_data = wd_data;
 823
 824         if (!hw_running)
 825                 kref_get(&wd_data->kref);
 826
 827         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 828         return nonseekable_open(inode, file);
 829
 830 out_mod:
 831         module_put(wd_data->wdd->ops->owner);
 832 out_clear:
 833         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 834         return err;
 835 }
 836
 837 static void watchdog_core_data_release(struct kref *kref)
 838 {
 839         struct watchdog_core_data *wd_data;
 840
 841         wd_data = container_of(kref, struct watchdog_core_data, kref);
 842
 843         kfree(wd_data);
 844 }
 845
 846 /*
 847  *      watchdog_release: release the watchdog device.
 848  *      @inode: inode of device
 849  *      @file: file handle to device
 850  *
 851  *      This is the code for when /dev/watchdog gets closed. We will only
 852  *      stop the watchdog when we have received the magic char (and nowayout
 853  *      was not set), else the watchdog will keep running.
 854  */
 855
 856 static int watchdog_release(struct inode *inode, struct file *file)
 857 {
 858         struct watchdog_core_data *wd_data = file->private_data;
 859         struct watchdog_device *wdd;
 860         int err = -EBUSY;
 861         bool running;
 862
 863         mutex_lock(&wd_data->lock);
 864
 865         wdd = wd_data->wdd;
 866         if (!wdd)
 867                 goto done;
 868
 869         /*
 870          * We only stop the watchdog if we received the magic character
 871          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 872          * watchdog_stop will fail.
 873          */
 874         if (!test_bit(WDOG_ACTIVE, &wdd->status))
 875                 err = 0;
 876         else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
 877                  !(wdd->info->options & WDIOF_MAGICCLOSE))
 878                 err = watchdog_stop(wdd);
 879
 880         /* If the watchdog was not stopped, send a keepalive ping */
 881         if (err < 0) {
 882                 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
 883                 watchdog_ping(wdd);
 884         }
 885
 886         watchdog_update_worker(wdd);
 887
 888         /* make sure that /dev/watchdog can be re-opened */
 889         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 890
 891 done:
 892         running = wdd && watchdog_hw_running(wdd);
 893         mutex_unlock(&wd_data->lock);
 894         /*
 895          * Allow the owner module to be unloaded again unless the watchdog
 896          * is still running. If the watchdog is still running, it can not
 897          * be stopped, and its driver must not be unloaded.
 898          */
 899         if (!running) {
 900                 module_put(wd_data->cdev.owner);
 901                 kref_put(&wd_data->kref, watchdog_core_data_release);
 902         }
 903         return 0;
 904 }
 905
 906 static const struct file_operations watchdog_fops = {
 907         .owner          = THIS_MODULE,
 908         .write          = watchdog_write,
 909         .unlocked_ioctl = watchdog_ioctl,
 910         .open           = watchdog_open,
 911         .release        = watchdog_release,
 912 };
 913
 914 static struct miscdevice watchdog_miscdev = {
 915         .minor          = WATCHDOG_MINOR,
 916         .name           = "watchdog",
 917         .fops           = &watchdog_fops,
 918 };
 919
 920 /*
 921  *      watchdog_cdev_register: register watchdog character device
 922  *      @wdd: watchdog device
 923  *      @devno: character device number
 924  *
 925  *      Register a watchdog character device including handling the legacy
 926  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 927  *      thus we set it up like that.
 928  */
 929
 930 static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
 931 {
 932         struct watchdog_core_data *wd_data;
 933         int err;
 934
 935         wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
 936         if (!wd_data)
 937                 return -ENOMEM;
 938         kref_init(&wd_data->kref);
 939         mutex_init(&wd_data->lock);
 940
 941         wd_data->wdd = wdd;
 942         wdd->wd_data = wd_data;
 943
 944         if (IS_ERR_OR_NULL(watchdog_kworker))
 945                 return -ENODEV;
 946
 947         kthread_init_work(&wd_data->work, watchdog_ping_work);
 948         hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 949         wd_data->timer.function = watchdog_timer_expired;
 950
 951         if (wdd->id == 0) {
 952                 old_wd_data = wd_data;
 953                 watchdog_miscdev.parent = wdd->parent;
 954                 err = misc_register(&watchdog_miscdev);
 955                 if (err != 0) {
 956                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
 957                                 wdd->info->identity, WATCHDOG_MINOR, err);
 958                         if (err == -EBUSY)
 959                                 pr_err("%s: a legacy watchdog module is probably present.\n",
 960                                         wdd->info->identity);
 961                         old_wd_data = NULL;
 962                         kfree(wd_data);
 963                         return err;
 964                 }
 965         }
 966
 967         /* Fill in the data structures */
 968         cdev_init(&wd_data->cdev, &watchdog_fops);
 969         wd_data->cdev.owner = wdd->ops->owner;
 970
 971         /* Add the device */
 972         err = cdev_add(&wd_data->cdev, devno, 1);
 973         if (err) {
 974                 pr_err("watchdog%d unable to add device %d:%d\n",
 975                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
 976                 if (wdd->id == 0) {
 977                         misc_deregister(&watchdog_miscdev);
 978                         old_wd_data = NULL;
 979                         kref_put(&wd_data->kref, watchdog_core_data_release);
 980                 }
 981                 return err;
 982         }
 983
 984         /* Record time of most recent heartbeat as 'just before now'. */
 985         wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
 986
 987         /*
 988          * If the watchdog is running, prevent its driver from being unloaded,
 989          * and schedule an immediate ping.
 990          */
 991         if (watchdog_hw_running(wdd)) {
 992                 __module_get(wdd->ops->owner);
 993                 kref_get(&wd_data->kref);
 994                 if (handle_boot_enabled)
 995                         hrtimer_start(&wd_data->timer, 0, HRTIMER_MODE_REL);
 996                 else
 997                         pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
 998                                 wdd->id);
 999         }
1000
1001         return 0;
1002 }
1003
1004 /*
1005  *      watchdog_cdev_unregister: unregister watchdog character device
1006  *      @watchdog: watchdog device
1007  *
1008  *      Unregister watchdog character device and if needed the legacy
1009  *      /dev/watchdog device.
1010  */
1011
1012 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1013 {
1014         struct watchdog_core_data *wd_data = wdd->wd_data;
1015
1016         cdev_del(&wd_data->cdev);
1017         if (wdd->id == 0) {
1018                 misc_deregister(&watchdog_miscdev);
1019                 old_wd_data = NULL;
1020         }
1021
1022         mutex_lock(&wd_data->lock);
1023         wd_data->wdd = NULL;
1024         wdd->wd_data = NULL;
1025         mutex_unlock(&wd_data->lock);
1026
1027         if (watchdog_active(wdd) &&
1028             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1029                 watchdog_stop(wdd);
1030         }
1031
1032         hrtimer_cancel(&wd_data->timer);
1033         kthread_cancel_work_sync(&wd_data->work);
1034
1035         kref_put(&wd_data->kref, watchdog_core_data_release);
1036 }
1037
1038 static struct class watchdog_class = {
1039         .name =         "watchdog",
1040         .owner =        THIS_MODULE,
1041         .dev_groups =   wdt_groups,
1042 };
1043
1044 static int watchdog_reboot_notifier(struct notifier_block *nb,
1045                                     unsigned long code, void *data)
1046 {
1047         struct watchdog_device *wdd;
1048
1049         wdd = container_of(nb, struct watchdog_device, reboot_nb);
1050         if (code == SYS_DOWN || code == SYS_HALT) {
1051                 if (watchdog_active(wdd)) {
1052                         int ret;
1053
1054                         ret = wdd->ops->stop(wdd);
1055                         if (ret)
1056                                 return NOTIFY_BAD;
1057                 }
1058         }
1059
1060         return NOTIFY_DONE;
1061 }
1062
1063 /*
1064  *      watchdog_dev_register: register a watchdog device
1065  *      @wdd: watchdog device
1066  *
1067  *      Register a watchdog device including handling the legacy
1068  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1069  *      thus we set it up like that.
1070  */
1071
1072 int watchdog_dev_register(struct watchdog_device *wdd)
1073 {
1074         struct device *dev;
1075         dev_t devno;
1076         int ret;
1077
1078         devno = MKDEV(MAJOR(watchdog_devt), wdd->id);
1079
1080         ret = watchdog_cdev_register(wdd, devno);
1081         if (ret)
1082                 return ret;
1083
1084         dev = device_create_with_groups(&watchdog_class, wdd->parent,
1085                                         devno, wdd, wdd->groups,
1086                                         "watchdog%d", wdd->id);
1087         if (IS_ERR(dev)) {
1088                 watchdog_cdev_unregister(wdd);
1089                 return PTR_ERR(dev);
1090         }
1091
1092         ret = watchdog_register_pretimeout(wdd);
1093         if (ret) {
1094                 device_destroy(&watchdog_class, devno);
1095                 watchdog_cdev_unregister(wdd);
1096                 return ret;
1097         }
1098
1099         if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
1100                 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
1101
1102                 ret = devm_register_reboot_notifier(dev, &wdd->reboot_nb);
1103                 if (ret) {
1104                         pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
1105                                wdd->id, ret);
1106                         watchdog_dev_unregister(wdd);
1107                 }
1108         }
1109
1110         return ret;
1111 }
1112
1113 /*
1114  *      watchdog_dev_unregister: unregister a watchdog device
1115  *      @watchdog: watchdog device
1116  *
1117  *      Unregister watchdog device and if needed the legacy
1118  *      /dev/watchdog device.
1119  */
1120
1121 void watchdog_dev_unregister(struct watchdog_device *wdd)
1122 {
1123         watchdog_unregister_pretimeout(wdd);
1124         device_destroy(&watchdog_class, wdd->wd_data->cdev.dev);
1125         watchdog_cdev_unregister(wdd);
1126 }
1127
1128 /*
1129  *      watchdog_dev_init: init dev part of watchdog core
1130  *
1131  *      Allocate a range of chardev nodes to use for watchdog devices
1132  */
1133
1134 int __init watchdog_dev_init(void)
1135 {
1136         int err;
1137         struct sched_param param = {.sched_priority = MAX_RT_PRIO - 1,};
1138
1139         watchdog_kworker = kthread_create_worker(0, "watchdogd");
1140         if (IS_ERR(watchdog_kworker)) {
1141                 pr_err("Failed to create watchdog kworker\n");
1142                 return PTR_ERR(watchdog_kworker);
1143         }
1144         sched_setscheduler(watchdog_kworker->task, SCHED_FIFO, &param);
1145
1146         err = class_register(&watchdog_class);
1147         if (err < 0) {
1148                 pr_err("couldn't register class\n");
1149                 goto err_register;
1150         }
1151
1152         err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1153         if (err < 0) {
1154                 pr_err("watchdog: unable to allocate char dev region\n");
1155                 goto err_alloc;
1156         }
1157
1158         return 0;
1159
1160 err_alloc:
1161         class_unregister(&watchdog_class);
1162 err_register:
1163         kthread_destroy_worker(watchdog_kworker);
1164         return err;
1165 }
1166
1167 /*
1168  *      watchdog_dev_exit: exit dev part of watchdog core
1169  *
1170  *      Release the range of chardev nodes used for watchdog devices
1171  */
1172
1173 void __exit watchdog_dev_exit(void)
1174 {
1175         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1176         class_unregister(&watchdog_class);
1177         kthread_destroy_worker(watchdog_kworker);
1178 }
1179
1180 module_param(handle_boot_enabled, bool, 0444);
1181 MODULE_PARM_DESC(handle_boot_enabled,
1182         "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1183         __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");