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/module.h>       /* For module stuff/... */
  36 #include <linux/types.h>        /* For standard types (like size_t) */
  37 #include <linux/errno.h>        /* For the -ENODEV/... values */
  38 #include <linux/kernel.h>       /* For printk/panic/... */
  39 #include <linux/fs.h>           /* For file operations */
  40 #include <linux/watchdog.h>     /* For watchdog specific items */
  41 #include <linux/miscdevice.h>   /* For handling misc devices */
  42 #include <linux/init.h>         /* For __init/__exit/... */
  43 #include <linux/uaccess.h>      /* For copy_to_user/put_user/... */
  44
  45 #include "watchdog_core.h"
  46
  47 /* the dev_t structure to store the dynamically allocated watchdog devices */
  48 static dev_t watchdog_devt;
  49 /* the watchdog device behind /dev/watchdog */
  50 static struct watchdog_device *old_wdd;
  51
  52 /*
  53  *      watchdog_ping: ping the watchdog.
  54  *      @wddev: the watchdog device to ping
  55  *
  56  *      If the watchdog has no own ping operation then it needs to be
  57  *      restarted via the start operation. This wrapper function does
  58  *      exactly that.
  59  *      We only ping when the watchdog device is running.
  60  */
  61
  62 static int watchdog_ping(struct watchdog_device *wddev)
  63 {
  64         int err = 0;
  65
  66         mutex_lock(&wddev->lock);
  67
  68         if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
  69                 err = -ENODEV;
  70                 goto out_ping;
  71         }
  72
  73         if (!watchdog_active(wddev))
  74                 goto out_ping;
  75
  76         if (wddev->ops->ping)
  77                 err = wddev->ops->ping(wddev);  /* ping the watchdog */
  78         else
  79                 err = wddev->ops->start(wddev); /* restart watchdog */
  80
  81 out_ping:
  82         mutex_unlock(&wddev->lock);
  83         return err;
  84 }
  85
  86 /*
  87  *      watchdog_start: wrapper to start the watchdog.
  88  *      @wddev: the watchdog device to start
  89  *
  90  *      Start the watchdog if it is not active and mark it active.
  91  *      This function returns zero on success or a negative errno code for
  92  *      failure.
  93  */
  94
  95 static int watchdog_start(struct watchdog_device *wddev)
  96 {
  97         int err = 0;
  98
  99         mutex_lock(&wddev->lock);
 100
 101         if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 102                 err = -ENODEV;
 103                 goto out_start;
 104         }
 105
 106         if (watchdog_active(wddev))
 107                 goto out_start;
 108
 109         err = wddev->ops->start(wddev);
 110         if (err == 0)
 111                 set_bit(WDOG_ACTIVE, &wddev->status);
 112
 113 out_start:
 114         mutex_unlock(&wddev->lock);
 115         return err;
 116 }
 117
 118 /*
 119  *      watchdog_stop: wrapper to stop the watchdog.
 120  *      @wddev: the watchdog device to stop
 121  *
 122  *      Stop the watchdog if it is still active and unmark it active.
 123  *      This function returns zero on success or a negative errno code for
 124  *      failure.
 125  *      If the 'nowayout' feature was set, the watchdog cannot be stopped.
 126  */
 127
 128 static int watchdog_stop(struct watchdog_device *wddev)
 129 {
 130         int err = 0;
 131
 132         mutex_lock(&wddev->lock);
 133
 134         if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 135                 err = -ENODEV;
 136                 goto out_stop;
 137         }
 138
 139         if (!watchdog_active(wddev))
 140                 goto out_stop;
 141
 142         if (test_bit(WDOG_NO_WAY_OUT, &wddev->status)) {
 143                 dev_info(wddev->dev, "nowayout prevents watchdog being stopped!\n");
 144                 err = -EBUSY;
 145                 goto out_stop;
 146         }
 147
 148         err = wddev->ops->stop(wddev);
 149         if (err == 0)
 150                 clear_bit(WDOG_ACTIVE, &wddev->status);
 151
 152 out_stop:
 153         mutex_unlock(&wddev->lock);
 154         return err;
 155 }
 156
 157 /*
 158  *      watchdog_get_status: wrapper to get the watchdog status
 159  *      @wddev: the watchdog device to get the status from
 160  *      @status: the status of the watchdog device
 161  *
 162  *      Get the watchdog's status flags.
 163  */
 164
 165 static int watchdog_get_status(struct watchdog_device *wddev,
 166                                                         unsigned int *status)
 167 {
 168         int err = 0;
 169
 170         *status = 0;
 171         if (!wddev->ops->status)
 172                 return -EOPNOTSUPP;
 173
 174         mutex_lock(&wddev->lock);
 175
 176         if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 177                 err = -ENODEV;
 178                 goto out_status;
 179         }
 180
 181         *status = wddev->ops->status(wddev);
 182
 183 out_status:
 184         mutex_unlock(&wddev->lock);
 185         return err;
 186 }
 187
 188 /*
 189  *      watchdog_set_timeout: set the watchdog timer timeout
 190  *      @wddev: the watchdog device to set the timeout for
 191  *      @timeout: timeout to set in seconds
 192  */
 193
 194 static int watchdog_set_timeout(struct watchdog_device *wddev,
 195                                                         unsigned int timeout)
 196 {
 197         int err;
 198
 199         if ((wddev->ops->set_timeout == NULL) ||
 200             !(wddev->info->options & WDIOF_SETTIMEOUT))
 201                 return -EOPNOTSUPP;
 202
 203         if ((wddev->max_timeout != 0) &&
 204             (timeout < wddev->min_timeout || timeout > wddev->max_timeout))
 205                 return -EINVAL;
 206
 207         mutex_lock(&wddev->lock);
 208
 209         if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 210                 err = -ENODEV;
 211                 goto out_timeout;
 212         }
 213
 214         err = wddev->ops->set_timeout(wddev, timeout);
 215
 216 out_timeout:
 217         mutex_unlock(&wddev->lock);
 218         return err;
 219 }
 220
 221 /*
 222  *      watchdog_get_timeleft: wrapper to get the time left before a reboot
 223  *      @wddev: the watchdog device to get the remaining time from
 224  *      @timeleft: the time that's left
 225  *
 226  *      Get the time before a watchdog will reboot (if not pinged).
 227  */
 228
 229 static int watchdog_get_timeleft(struct watchdog_device *wddev,
 230                                                         unsigned int *timeleft)
 231 {
 232         int err = 0;
 233
 234         *timeleft = 0;
 235         if (!wddev->ops->get_timeleft)
 236                 return -EOPNOTSUPP;
 237
 238         mutex_lock(&wddev->lock);
 239
 240         if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 241                 err = -ENODEV;
 242                 goto out_timeleft;
 243         }
 244
 245         *timeleft = wddev->ops->get_timeleft(wddev);
 246
 247 out_timeleft:
 248         mutex_unlock(&wddev->lock);
 249         return err;
 250 }
 251
 252 /*
 253  *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 254  *      @wddev: the watchdog device to do the ioctl on
 255  *      @cmd: watchdog command
 256  *      @arg: argument pointer
 257  */
 258
 259 static int watchdog_ioctl_op(struct watchdog_device *wddev, unsigned int cmd,
 260                                                         unsigned long arg)
 261 {
 262         int err;
 263
 264         if (!wddev->ops->ioctl)
 265                 return -ENOIOCTLCMD;
 266
 267         mutex_lock(&wddev->lock);
 268
 269         if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 270                 err = -ENODEV;
 271                 goto out_ioctl;
 272         }
 273
 274         err = wddev->ops->ioctl(wddev, cmd, arg);
 275
 276 out_ioctl:
 277         mutex_unlock(&wddev->lock);
 278         return err;
 279 }
 280
 281 /*
 282  *      watchdog_write: writes to the watchdog.
 283  *      @file: file from VFS
 284  *      @data: user address of data
 285  *      @len: length of data
 286  *      @ppos: pointer to the file offset
 287  *
 288  *      A write to a watchdog device is defined as a keepalive ping.
 289  *      Writing the magic 'V' sequence allows the next close to turn
 290  *      off the watchdog (if 'nowayout' is not set).
 291  */
 292
 293 static ssize_t watchdog_write(struct file *file, const char __user *data,
 294                                                 size_t len, loff_t *ppos)
 295 {
 296         struct watchdog_device *wdd = file->private_data;
 297         size_t i;
 298         char c;
 299
 300         if (len == 0)
 301                 return 0;
 302
 303         /*
 304          * Note: just in case someone wrote the magic character
 305          * five months ago...
 306          */
 307         clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
 308
 309         /* scan to see whether or not we got the magic character */
 310         for (i = 0; i != len; i++) {
 311                 if (get_user(c, data + i))
 312                         return -EFAULT;
 313                 if (c == 'V')
 314                         set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
 315         }
 316
 317         /* someone wrote to us, so we send the watchdog a keepalive ping */
 318         watchdog_ping(wdd);
 319
 320         return len;
 321 }
 322
 323 /*
 324  *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 325  *      @file: file handle to the device
 326  *      @cmd: watchdog command
 327  *      @arg: argument pointer
 328  *
 329  *      The watchdog API defines a common set of functions for all watchdogs
 330  *      according to their available features.
 331  */
 332
 333 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 334                                                         unsigned long arg)
 335 {
 336         struct watchdog_device *wdd = file->private_data;
 337         void __user *argp = (void __user *)arg;
 338         int __user *p = argp;
 339         unsigned int val;
 340         int err;
 341
 342         err = watchdog_ioctl_op(wdd, cmd, arg);
 343         if (err != -ENOIOCTLCMD)
 344                 return err;
 345
 346         switch (cmd) {
 347         case WDIOC_GETSUPPORT:
 348                 return copy_to_user(argp, wdd->info,
 349                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
 350         case WDIOC_GETSTATUS:
 351                 err = watchdog_get_status(wdd, &val);
 352                 if (err)
 353                         return err;
 354                 return put_user(val, p);
 355         case WDIOC_GETBOOTSTATUS:
 356                 return put_user(wdd->bootstatus, p);
 357         case WDIOC_SETOPTIONS:
 358                 if (get_user(val, p))
 359                         return -EFAULT;
 360                 if (val & WDIOS_DISABLECARD) {
 361                         err = watchdog_stop(wdd);
 362                         if (err < 0)
 363                                 return err;
 364                 }
 365                 if (val & WDIOS_ENABLECARD) {
 366                         err = watchdog_start(wdd);
 367                         if (err < 0)
 368                                 return err;
 369                 }
 370                 return 0;
 371         case WDIOC_KEEPALIVE:
 372                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
 373                         return -EOPNOTSUPP;
 374                 watchdog_ping(wdd);
 375                 return 0;
 376         case WDIOC_SETTIMEOUT:
 377                 if (get_user(val, p))
 378                         return -EFAULT;
 379                 err = watchdog_set_timeout(wdd, val);
 380                 if (err < 0)
 381                         return err;
 382                 /* If the watchdog is active then we send a keepalive ping
 383                  * to make sure that the watchdog keep's running (and if
 384                  * possible that it takes the new timeout) */
 385                 watchdog_ping(wdd);
 386                 /* Fall */
 387         case WDIOC_GETTIMEOUT:
 388                 /* timeout == 0 means that we don't know the timeout */
 389                 if (wdd->timeout == 0)
 390                         return -EOPNOTSUPP;
 391                 return put_user(wdd->timeout, p);
 392         case WDIOC_GETTIMELEFT:
 393                 err = watchdog_get_timeleft(wdd, &val);
 394                 if (err)
 395                         return err;
 396                 return put_user(val, p);
 397         default:
 398                 return -ENOTTY;
 399         }
 400 }
 401
 402 /*
 403  *      watchdog_open: open the /dev/watchdog* devices.
 404  *      @inode: inode of device
 405  *      @file: file handle to device
 406  *
 407  *      When the /dev/watchdog* device gets opened, we start the watchdog.
 408  *      Watch out: the /dev/watchdog device is single open, so we make sure
 409  *      it can only be opened once.
 410  */
 411
 412 static int watchdog_open(struct inode *inode, struct file *file)
 413 {
 414         int err = -EBUSY;
 415         struct watchdog_device *wdd;
 416
 417         /* Get the corresponding watchdog device */
 418         if (imajor(inode) == MISC_MAJOR)
 419                 wdd = old_wdd;
 420         else
 421                 wdd = container_of(inode->i_cdev, struct watchdog_device, cdev);
 422
 423         /* the watchdog is single open! */
 424         if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
 425                 return -EBUSY;
 426
 427         /*
 428          * If the /dev/watchdog device is open, we don't want the module
 429          * to be unloaded.
 430          */
 431         if (!try_module_get(wdd->ops->owner))
 432                 goto out;
 433
 434         err = watchdog_start(wdd);
 435         if (err < 0)
 436                 goto out_mod;
 437
 438         file->private_data = wdd;
 439
 440         if (wdd->ops->ref)
 441                 wdd->ops->ref(wdd);
 442
 443         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 444         return nonseekable_open(inode, file);
 445
 446 out_mod:
 447         module_put(wdd->ops->owner);
 448 out:
 449         clear_bit(WDOG_DEV_OPEN, &wdd->status);
 450         return err;
 451 }
 452
 453 /*
 454  *      watchdog_release: release the watchdog device.
 455  *      @inode: inode of device
 456  *      @file: file handle to device
 457  *
 458  *      This is the code for when /dev/watchdog gets closed. We will only
 459  *      stop the watchdog when we have received the magic char (and nowayout
 460  *      was not set), else the watchdog will keep running.
 461  */
 462
 463 static int watchdog_release(struct inode *inode, struct file *file)
 464 {
 465         struct watchdog_device *wdd = file->private_data;
 466         int err = -EBUSY;
 467
 468         /*
 469          * We only stop the watchdog if we received the magic character
 470          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 471          * watchdog_stop will fail.
 472          */
 473         if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
 474             !(wdd->info->options & WDIOF_MAGICCLOSE))
 475                 err = watchdog_stop(wdd);
 476
 477         /* If the watchdog was not stopped, send a keepalive ping */
 478         if (err < 0) {
 479                 mutex_lock(&wdd->lock);
 480                 if (!test_bit(WDOG_UNREGISTERED, &wdd->status))
 481                         dev_crit(wdd->dev, "watchdog did not stop!\n");
 482                 mutex_unlock(&wdd->lock);
 483                 watchdog_ping(wdd);
 484         }
 485
 486         /* Allow the owner module to be unloaded again */
 487         module_put(wdd->ops->owner);
 488
 489         /* make sure that /dev/watchdog can be re-opened */
 490         clear_bit(WDOG_DEV_OPEN, &wdd->status);
 491
 492         /* Note wdd may be gone after this, do not use after this! */
 493         if (wdd->ops->unref)
 494                 wdd->ops->unref(wdd);
 495
 496         return 0;
 497 }
 498
 499 static const struct file_operations watchdog_fops = {
 500         .owner          = THIS_MODULE,
 501         .write          = watchdog_write,
 502         .unlocked_ioctl = watchdog_ioctl,
 503         .open           = watchdog_open,
 504         .release        = watchdog_release,
 505 };
 506
 507 static struct miscdevice watchdog_miscdev = {
 508         .minor          = WATCHDOG_MINOR,
 509         .name           = "watchdog",
 510         .fops           = &watchdog_fops,
 511 };
 512
 513 /*
 514  *      watchdog_dev_register: register a watchdog device
 515  *      @watchdog: watchdog device
 516  *
 517  *      Register a watchdog device including handling the legacy
 518  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 519  *      thus we set it up like that.
 520  */
 521
 522 int watchdog_dev_register(struct watchdog_device *watchdog)
 523 {
 524         int err, devno;
 525
 526         if (watchdog->id == 0) {
 527                 watchdog_miscdev.parent = watchdog->parent;
 528                 err = misc_register(&watchdog_miscdev);
 529                 if (err != 0) {
 530                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
 531                                 watchdog->info->identity, WATCHDOG_MINOR, err);
 532                         if (err == -EBUSY)
 533                                 pr_err("%s: a legacy watchdog module is probably present.\n",
 534                                         watchdog->info->identity);
 535                         return err;
 536                 }
 537                 old_wdd = watchdog;
 538         }
 539
 540         /* Fill in the data structures */
 541         devno = MKDEV(MAJOR(watchdog_devt), watchdog->id);
 542         cdev_init(&watchdog->cdev, &watchdog_fops);
 543         watchdog->cdev.owner = watchdog->ops->owner;
 544
 545         /* Add the device */
 546         err  = cdev_add(&watchdog->cdev, devno, 1);
 547         if (err) {
 548                 pr_err("watchdog%d unable to add device %d:%d\n",
 549                         watchdog->id,  MAJOR(watchdog_devt), watchdog->id);
 550                 if (watchdog->id == 0) {
 551                         misc_deregister(&watchdog_miscdev);
 552                         old_wdd = NULL;
 553                 }
 554         }
 555         return err;
 556 }
 557
 558 /*
 559  *      watchdog_dev_unregister: unregister a watchdog device
 560  *      @watchdog: watchdog device
 561  *
 562  *      Unregister the watchdog and if needed the legacy /dev/watchdog device.
 563  */
 564
 565 int watchdog_dev_unregister(struct watchdog_device *watchdog)
 566 {
 567         mutex_lock(&watchdog->lock);
 568         set_bit(WDOG_UNREGISTERED, &watchdog->status);
 569         mutex_unlock(&watchdog->lock);
 570
 571         cdev_del(&watchdog->cdev);
 572         if (watchdog->id == 0) {
 573                 misc_deregister(&watchdog_miscdev);
 574                 old_wdd = NULL;
 575         }
 576         return 0;
 577 }
 578
 579 /*
 580  *      watchdog_dev_init: init dev part of watchdog core
 581  *
 582  *      Allocate a range of chardev nodes to use for watchdog devices
 583  */
 584
 585 int __init watchdog_dev_init(void)
 586 {
 587         int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
 588         if (err < 0)
 589                 pr_err("watchdog: unable to allocate char dev region\n");
 590         return err;
 591 }
 592
 593 /*
 594  *      watchdog_dev_exit: exit dev part of watchdog core
 595  *
 596  *      Release the range of chardev nodes used for watchdog devices
 597  */
 598
 599 void __exit watchdog_dev_exit(void)
 600 {
 601         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
 602 }