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  *      @wdd: 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 *wdd)
  63 {
  64         int err = 0;
  65
  66         mutex_lock(&wdd->lock);
  67
  68         if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
  69                 err = -ENODEV;
  70                 goto out_ping;
  71         }
  72
  73         if (!watchdog_active(wdd))
  74                 goto out_ping;
  75
  76         if (wdd->ops->ping)
  77                 err = wdd->ops->ping(wdd);      /* ping the watchdog */
  78         else
  79                 err = wdd->ops->start(wdd);     /* restart watchdog */
  80
  81 out_ping:
  82         mutex_unlock(&wdd->lock);
  83         return err;
  84 }
  85
  86 /*
  87  *      watchdog_start: wrapper to start the watchdog.
  88  *      @wdd: 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 *wdd)
  96 {
  97         int err = 0;
  98
  99         mutex_lock(&wdd->lock);
 100
 101         if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
 102                 err = -ENODEV;
 103                 goto out_start;
 104         }
 105
 106         if (watchdog_active(wdd))
 107                 goto out_start;
 108
 109         err = wdd->ops->start(wdd);
 110         if (err == 0)
 111                 set_bit(WDOG_ACTIVE, &wdd->status);
 112
 113 out_start:
 114         mutex_unlock(&wdd->lock);
 115         return err;
 116 }
 117
 118 /*
 119  *      watchdog_stop: wrapper to stop the watchdog.
 120  *      @wdd: 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 *wdd)
 129 {
 130         int err = 0;
 131
 132         mutex_lock(&wdd->lock);
 133
 134         if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
 135                 err = -ENODEV;
 136                 goto out_stop;
 137         }
 138
 139         if (!watchdog_active(wdd))
 140                 goto out_stop;
 141
 142         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
 143                 dev_info(wdd->dev, "nowayout prevents watchdog being stopped!\n");
 144                 err = -EBUSY;
 145                 goto out_stop;
 146         }
 147
 148         err = wdd->ops->stop(wdd);
 149         if (err == 0)
 150                 clear_bit(WDOG_ACTIVE, &wdd->status);
 151
 152 out_stop:
 153         mutex_unlock(&wdd->lock);
 154         return err;
 155 }
 156
 157 /*
 158  *      watchdog_get_status: wrapper to get the watchdog status
 159  *      @wdd: 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 *wdd,
 166                                                         unsigned int *status)
 167 {
 168         int err = 0;
 169
 170         *status = 0;
 171         if (!wdd->ops->status)
 172                 return -EOPNOTSUPP;
 173
 174         mutex_lock(&wdd->lock);
 175
 176         if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
 177                 err = -ENODEV;
 178                 goto out_status;
 179         }
 180
 181         *status = wdd->ops->status(wdd);
 182
 183 out_status:
 184         mutex_unlock(&wdd->lock);
 185         return err;
 186 }
 187
 188 /*
 189  *      watchdog_set_timeout: set the watchdog timer timeout
 190  *      @wdd: 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 *wdd,
 195                                                         unsigned int timeout)
 196 {
 197         int err;
 198
 199         if (!wdd->ops->set_timeout || !(wdd->info->options & WDIOF_SETTIMEOUT))
 200                 return -EOPNOTSUPP;
 201
 202         if (watchdog_timeout_invalid(wdd, timeout))
 203                 return -EINVAL;
 204
 205         mutex_lock(&wdd->lock);
 206
 207         if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
 208                 err = -ENODEV;
 209                 goto out_timeout;
 210         }
 211
 212         err = wdd->ops->set_timeout(wdd, timeout);
 213
 214 out_timeout:
 215         mutex_unlock(&wdd->lock);
 216         return err;
 217 }
 218
 219 /*
 220  *      watchdog_get_timeleft: wrapper to get the time left before a reboot
 221  *      @wdd: the watchdog device to get the remaining time from
 222  *      @timeleft: the time that's left
 223  *
 224  *      Get the time before a watchdog will reboot (if not pinged).
 225  */
 226
 227 static int watchdog_get_timeleft(struct watchdog_device *wdd,
 228                                                         unsigned int *timeleft)
 229 {
 230         int err = 0;
 231
 232         *timeleft = 0;
 233         if (!wdd->ops->get_timeleft)
 234                 return -EOPNOTSUPP;
 235
 236         mutex_lock(&wdd->lock);
 237
 238         if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
 239                 err = -ENODEV;
 240                 goto out_timeleft;
 241         }
 242
 243         *timeleft = wdd->ops->get_timeleft(wdd);
 244
 245 out_timeleft:
 246         mutex_unlock(&wdd->lock);
 247         return err;
 248 }
 249
 250 /*
 251  *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 252  *      @wdd: the watchdog device to do the ioctl on
 253  *      @cmd: watchdog command
 254  *      @arg: argument pointer
 255  */
 256
 257 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
 258                                                         unsigned long arg)
 259 {
 260         int err;
 261
 262         if (!wdd->ops->ioctl)
 263                 return -ENOIOCTLCMD;
 264
 265         mutex_lock(&wdd->lock);
 266
 267         if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
 268                 err = -ENODEV;
 269                 goto out_ioctl;
 270         }
 271
 272         err = wdd->ops->ioctl(wdd, cmd, arg);
 273
 274 out_ioctl:
 275         mutex_unlock(&wdd->lock);
 276         return err;
 277 }
 278
 279 /*
 280  *      watchdog_write: writes to the watchdog.
 281  *      @file: file from VFS
 282  *      @data: user address of data
 283  *      @len: length of data
 284  *      @ppos: pointer to the file offset
 285  *
 286  *      A write to a watchdog device is defined as a keepalive ping.
 287  *      Writing the magic 'V' sequence allows the next close to turn
 288  *      off the watchdog (if 'nowayout' is not set).
 289  */
 290
 291 static ssize_t watchdog_write(struct file *file, const char __user *data,
 292                                                 size_t len, loff_t *ppos)
 293 {
 294         struct watchdog_device *wdd = file->private_data;
 295         size_t i;
 296         char c;
 297         int err;
 298
 299         if (len == 0)
 300                 return 0;
 301
 302         /*
 303          * Note: just in case someone wrote the magic character
 304          * five months ago...
 305          */
 306         clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
 307
 308         /* scan to see whether or not we got the magic character */
 309         for (i = 0; i != len; i++) {
 310                 if (get_user(c, data + i))
 311                         return -EFAULT;
 312                 if (c == 'V')
 313                         set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
 314         }
 315
 316         /* someone wrote to us, so we send the watchdog a keepalive ping */
 317         err = watchdog_ping(wdd);
 318         if (err < 0)
 319                 return err;
 320
 321         return len;
 322 }
 323
 324 /*
 325  *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 326  *      @file: file handle to the device
 327  *      @cmd: watchdog command
 328  *      @arg: argument pointer
 329  *
 330  *      The watchdog API defines a common set of functions for all watchdogs
 331  *      according to their available features.
 332  */
 333
 334 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 335                                                         unsigned long arg)
 336 {
 337         struct watchdog_device *wdd = file->private_data;
 338         void __user *argp = (void __user *)arg;
 339         int __user *p = argp;
 340         unsigned int val;
 341         int err;
 342
 343         err = watchdog_ioctl_op(wdd, cmd, arg);
 344         if (err != -ENOIOCTLCMD)
 345                 return err;
 346
 347         switch (cmd) {
 348         case WDIOC_GETSUPPORT:
 349                 return copy_to_user(argp, wdd->info,
 350                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
 351         case WDIOC_GETSTATUS:
 352                 err = watchdog_get_status(wdd, &val);
 353                 if (err == -ENODEV)
 354                         return err;
 355                 return put_user(val, p);
 356         case WDIOC_GETBOOTSTATUS:
 357                 return put_user(wdd->bootstatus, p);
 358         case WDIOC_SETOPTIONS:
 359                 if (get_user(val, p))
 360                         return -EFAULT;
 361                 if (val & WDIOS_DISABLECARD) {
 362                         err = watchdog_stop(wdd);
 363                         if (err < 0)
 364                                 return err;
 365                 }
 366                 if (val & WDIOS_ENABLECARD) {
 367                         err = watchdog_start(wdd);
 368                         if (err < 0)
 369                                 return err;
 370                 }
 371                 return 0;
 372         case WDIOC_KEEPALIVE:
 373                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
 374                         return -EOPNOTSUPP;
 375                 return watchdog_ping(wdd);
 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                 err = watchdog_ping(wdd);
 386                 if (err < 0)
 387                         return err;
 388                 /* Fall */
 389         case WDIOC_GETTIMEOUT:
 390                 /* timeout == 0 means that we don't know the timeout */
 391                 if (wdd->timeout == 0)
 392                         return -EOPNOTSUPP;
 393                 return put_user(wdd->timeout, p);
 394         case WDIOC_GETTIMELEFT:
 395                 err = watchdog_get_timeleft(wdd, &val);
 396                 if (err)
 397                         return err;
 398                 return put_user(val, p);
 399         default:
 400                 return -ENOTTY;
 401         }
 402 }
 403
 404 /*
 405  *      watchdog_open: open the /dev/watchdog* devices.
 406  *      @inode: inode of device
 407  *      @file: file handle to device
 408  *
 409  *      When the /dev/watchdog* device gets opened, we start the watchdog.
 410  *      Watch out: the /dev/watchdog device is single open, so we make sure
 411  *      it can only be opened once.
 412  */
 413
 414 static int watchdog_open(struct inode *inode, struct file *file)
 415 {
 416         int err = -EBUSY;
 417         struct watchdog_device *wdd;
 418
 419         /* Get the corresponding watchdog device */
 420         if (imajor(inode) == MISC_MAJOR)
 421                 wdd = old_wdd;
 422         else
 423                 wdd = container_of(inode->i_cdev, struct watchdog_device, cdev);
 424
 425         /* the watchdog is single open! */
 426         if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
 427                 return -EBUSY;
 428
 429         /*
 430          * If the /dev/watchdog device is open, we don't want the module
 431          * to be unloaded.
 432          */
 433         if (!try_module_get(wdd->ops->owner))
 434                 goto out;
 435
 436         err = watchdog_start(wdd);
 437         if (err < 0)
 438                 goto out_mod;
 439
 440         file->private_data = wdd;
 441
 442         if (wdd->ops->ref)
 443                 wdd->ops->ref(wdd);
 444
 445         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 446         return nonseekable_open(inode, file);
 447
 448 out_mod:
 449         module_put(wdd->ops->owner);
 450 out:
 451         clear_bit(WDOG_DEV_OPEN, &wdd->status);
 452         return err;
 453 }
 454
 455 /*
 456  *      watchdog_release: release the watchdog device.
 457  *      @inode: inode of device
 458  *      @file: file handle to device
 459  *
 460  *      This is the code for when /dev/watchdog gets closed. We will only
 461  *      stop the watchdog when we have received the magic char (and nowayout
 462  *      was not set), else the watchdog will keep running.
 463  */
 464
 465 static int watchdog_release(struct inode *inode, struct file *file)
 466 {
 467         struct watchdog_device *wdd = file->private_data;
 468         int err = -EBUSY;
 469
 470         /*
 471          * We only stop the watchdog if we received the magic character
 472          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 473          * watchdog_stop will fail.
 474          */
 475         if (!test_bit(WDOG_ACTIVE, &wdd->status))
 476                 err = 0;
 477         else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
 478                  !(wdd->info->options & WDIOF_MAGICCLOSE))
 479                 err = watchdog_stop(wdd);
 480
 481         /* If the watchdog was not stopped, send a keepalive ping */
 482         if (err < 0) {
 483                 mutex_lock(&wdd->lock);
 484                 if (!test_bit(WDOG_UNREGISTERED, &wdd->status))
 485                         dev_crit(wdd->dev, "watchdog did not stop!\n");
 486                 mutex_unlock(&wdd->lock);
 487                 watchdog_ping(wdd);
 488         }
 489
 490         /* Allow the owner module to be unloaded again */
 491         module_put(wdd->ops->owner);
 492
 493         /* make sure that /dev/watchdog can be re-opened */
 494         clear_bit(WDOG_DEV_OPEN, &wdd->status);
 495
 496         /* Note wdd may be gone after this, do not use after this! */
 497         if (wdd->ops->unref)
 498                 wdd->ops->unref(wdd);
 499
 500         return 0;
 501 }
 502
 503 static const struct file_operations watchdog_fops = {
 504         .owner          = THIS_MODULE,
 505         .write          = watchdog_write,
 506         .unlocked_ioctl = watchdog_ioctl,
 507         .open           = watchdog_open,
 508         .release        = watchdog_release,
 509 };
 510
 511 static struct miscdevice watchdog_miscdev = {
 512         .minor          = WATCHDOG_MINOR,
 513         .name           = "watchdog",
 514         .fops           = &watchdog_fops,
 515 };
 516
 517 /*
 518  *      watchdog_dev_register: register a watchdog device
 519  *      @wdd: watchdog device
 520  *
 521  *      Register a watchdog device including handling the legacy
 522  *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 523  *      thus we set it up like that.
 524  */
 525
 526 int watchdog_dev_register(struct watchdog_device *wdd)
 527 {
 528         int err, devno;
 529
 530         if (wdd->id == 0) {
 531                 old_wdd = wdd;
 532                 watchdog_miscdev.parent = wdd->parent;
 533                 err = misc_register(&watchdog_miscdev);
 534                 if (err != 0) {
 535                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
 536                                 wdd->info->identity, WATCHDOG_MINOR, err);
 537                         if (err == -EBUSY)
 538                                 pr_err("%s: a legacy watchdog module is probably present.\n",
 539                                         wdd->info->identity);
 540                         old_wdd = NULL;
 541                         return err;
 542                 }
 543         }
 544
 545         /* Fill in the data structures */
 546         devno = MKDEV(MAJOR(watchdog_devt), wdd->id);
 547         cdev_init(&wdd->cdev, &watchdog_fops);
 548         wdd->cdev.owner = wdd->ops->owner;
 549
 550         /* Add the device */
 551         err  = cdev_add(&wdd->cdev, devno, 1);
 552         if (err) {
 553                 pr_err("watchdog%d unable to add device %d:%d\n",
 554                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
 555                 if (wdd->id == 0) {
 556                         misc_deregister(&watchdog_miscdev);
 557                         old_wdd = NULL;
 558                 }
 559         }
 560         return err;
 561 }
 562
 563 /*
 564  *      watchdog_dev_unregister: unregister a watchdog device
 565  *      @watchdog: watchdog device
 566  *
 567  *      Unregister the watchdog and if needed the legacy /dev/watchdog device.
 568  */
 569
 570 int watchdog_dev_unregister(struct watchdog_device *wdd)
 571 {
 572         mutex_lock(&wdd->lock);
 573         set_bit(WDOG_UNREGISTERED, &wdd->status);
 574         mutex_unlock(&wdd->lock);
 575
 576         cdev_del(&wdd->cdev);
 577         if (wdd->id == 0) {
 578                 misc_deregister(&watchdog_miscdev);
 579                 old_wdd = NULL;
 580         }
 581         return 0;
 582 }
 583
 584 /*
 585  *      watchdog_dev_init: init dev part of watchdog core
 586  *
 587  *      Allocate a range of chardev nodes to use for watchdog devices
 588  */
 589
 590 int __init watchdog_dev_init(void)
 591 {
 592         int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
 593         if (err < 0)
 594                 pr_err("watchdog: unable to allocate char dev region\n");
 595         return err;
 596 }
 597
 598 /*
 599  *      watchdog_dev_exit: exit dev part of watchdog core
 600  *
 601  *      Release the range of chardev nodes used for watchdog devices
 602  */
 603
 604 void __exit watchdog_dev_exit(void)
 605 {
 606         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
 607 }