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