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 #ifdef CONFIG_WATCHDOG_SYSFS 251 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr, 252 char *buf) 253 { 254 struct watchdog_device *wdd = dev_get_drvdata(dev); 255 256 return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status)); 257 } 258 static DEVICE_ATTR_RO(nowayout); 259 260 static ssize_t status_show(struct device *dev, struct device_attribute *attr, 261 char *buf) 262 { 263 struct watchdog_device *wdd = dev_get_drvdata(dev); 264 ssize_t status; 265 unsigned int val; 266 267 status = watchdog_get_status(wdd, &val); 268 if (!status) 269 status = sprintf(buf, "%u\n", val); 270 271 return status; 272 } 273 static DEVICE_ATTR_RO(status); 274 275 static ssize_t bootstatus_show(struct device *dev, 276 struct device_attribute *attr, char *buf) 277 { 278 struct watchdog_device *wdd = dev_get_drvdata(dev); 279 280 return sprintf(buf, "%u\n", wdd->bootstatus); 281 } 282 static DEVICE_ATTR_RO(bootstatus); 283 284 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr, 285 char *buf) 286 { 287 struct watchdog_device *wdd = dev_get_drvdata(dev); 288 ssize_t status; 289 unsigned int val; 290 291 status = watchdog_get_timeleft(wdd, &val); 292 if (!status) 293 status = sprintf(buf, "%u\n", val); 294 295 return status; 296 } 297 static DEVICE_ATTR_RO(timeleft); 298 299 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr, 300 char *buf) 301 { 302 struct watchdog_device *wdd = dev_get_drvdata(dev); 303 304 return sprintf(buf, "%u\n", wdd->timeout); 305 } 306 static DEVICE_ATTR_RO(timeout); 307 308 static ssize_t identity_show(struct device *dev, struct device_attribute *attr, 309 char *buf) 310 { 311 struct watchdog_device *wdd = dev_get_drvdata(dev); 312 313 return sprintf(buf, "%s\n", wdd->info->identity); 314 } 315 static DEVICE_ATTR_RO(identity); 316 317 static ssize_t state_show(struct device *dev, struct device_attribute *attr, 318 char *buf) 319 { 320 struct watchdog_device *wdd = dev_get_drvdata(dev); 321 322 if (watchdog_active(wdd)) 323 return sprintf(buf, "active\n"); 324 325 return sprintf(buf, "inactive\n"); 326 } 327 static DEVICE_ATTR_RO(state); 328 329 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr, 330 int n) 331 { 332 struct device *dev = container_of(kobj, struct device, kobj); 333 struct watchdog_device *wdd = dev_get_drvdata(dev); 334 umode_t mode = attr->mode; 335 336 if (attr == &dev_attr_status.attr && !wdd->ops->status) 337 mode = 0; 338 else if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft) 339 mode = 0; 340 341 return mode; 342 } 343 static struct attribute *wdt_attrs[] = { 344 &dev_attr_state.attr, 345 &dev_attr_identity.attr, 346 &dev_attr_timeout.attr, 347 &dev_attr_timeleft.attr, 348 &dev_attr_bootstatus.attr, 349 &dev_attr_status.attr, 350 &dev_attr_nowayout.attr, 351 NULL, 352 }; 353 354 static const struct attribute_group wdt_group = { 355 .attrs = wdt_attrs, 356 .is_visible = wdt_is_visible, 357 }; 358 __ATTRIBUTE_GROUPS(wdt); 359 #else 360 #define wdt_groups NULL 361 #endif 362 363 /* 364 * watchdog_ioctl_op: call the watchdog drivers ioctl op if defined 365 * @wdd: the watchdog device to do the ioctl on 366 * @cmd: watchdog command 367 * @arg: argument pointer 368 */ 369 370 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd, 371 unsigned long arg) 372 { 373 int err; 374 375 if (!wdd->ops->ioctl) 376 return -ENOIOCTLCMD; 377 378 mutex_lock(&wdd->lock); 379 380 if (test_bit(WDOG_UNREGISTERED, &wdd->status)) { 381 err = -ENODEV; 382 goto out_ioctl; 383 } 384 385 err = wdd->ops->ioctl(wdd, cmd, arg); 386 387 out_ioctl: 388 mutex_unlock(&wdd->lock); 389 return err; 390 } 391 392 /* 393 * watchdog_write: writes to the watchdog. 394 * @file: file from VFS 395 * @data: user address of data 396 * @len: length of data 397 * @ppos: pointer to the file offset 398 * 399 * A write to a watchdog device is defined as a keepalive ping. 400 * Writing the magic 'V' sequence allows the next close to turn 401 * off the watchdog (if 'nowayout' is not set). 402 */ 403 404 static ssize_t watchdog_write(struct file *file, const char __user *data, 405 size_t len, loff_t *ppos) 406 { 407 struct watchdog_device *wdd = file->private_data; 408 size_t i; 409 char c; 410 int err; 411 412 if (len == 0) 413 return 0; 414 415 /* 416 * Note: just in case someone wrote the magic character 417 * five months ago... 418 */ 419 clear_bit(WDOG_ALLOW_RELEASE, &wdd->status); 420 421 /* scan to see whether or not we got the magic character */ 422 for (i = 0; i != len; i++) { 423 if (get_user(c, data + i)) 424 return -EFAULT; 425 if (c == 'V') 426 set_bit(WDOG_ALLOW_RELEASE, &wdd->status); 427 } 428 429 /* someone wrote to us, so we send the watchdog a keepalive ping */ 430 err = watchdog_ping(wdd); 431 if (err < 0) 432 return err; 433 434 return len; 435 } 436 437 /* 438 * watchdog_ioctl: handle the different ioctl's for the watchdog device. 439 * @file: file handle to the device 440 * @cmd: watchdog command 441 * @arg: argument pointer 442 * 443 * The watchdog API defines a common set of functions for all watchdogs 444 * according to their available features. 445 */ 446 447 static long watchdog_ioctl(struct file *file, unsigned int cmd, 448 unsigned long arg) 449 { 450 struct watchdog_device *wdd = file->private_data; 451 void __user *argp = (void __user *)arg; 452 int __user *p = argp; 453 unsigned int val; 454 int err; 455 456 err = watchdog_ioctl_op(wdd, cmd, arg); 457 if (err != -ENOIOCTLCMD) 458 return err; 459 460 switch (cmd) { 461 case WDIOC_GETSUPPORT: 462 return copy_to_user(argp, wdd->info, 463 sizeof(struct watchdog_info)) ? -EFAULT : 0; 464 case WDIOC_GETSTATUS: 465 err = watchdog_get_status(wdd, &val); 466 if (err == -ENODEV) 467 return err; 468 return put_user(val, p); 469 case WDIOC_GETBOOTSTATUS: 470 return put_user(wdd->bootstatus, p); 471 case WDIOC_SETOPTIONS: 472 if (get_user(val, p)) 473 return -EFAULT; 474 if (val & WDIOS_DISABLECARD) { 475 err = watchdog_stop(wdd); 476 if (err < 0) 477 return err; 478 } 479 if (val & WDIOS_ENABLECARD) { 480 err = watchdog_start(wdd); 481 if (err < 0) 482 return err; 483 } 484 return 0; 485 case WDIOC_KEEPALIVE: 486 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) 487 return -EOPNOTSUPP; 488 return watchdog_ping(wdd); 489 case WDIOC_SETTIMEOUT: 490 if (get_user(val, p)) 491 return -EFAULT; 492 err = watchdog_set_timeout(wdd, val); 493 if (err < 0) 494 return err; 495 /* If the watchdog is active then we send a keepalive ping 496 * to make sure that the watchdog keep's running (and if 497 * possible that it takes the new timeout) */ 498 err = watchdog_ping(wdd); 499 if (err < 0) 500 return err; 501 /* Fall */ 502 case WDIOC_GETTIMEOUT: 503 /* timeout == 0 means that we don't know the timeout */ 504 if (wdd->timeout == 0) 505 return -EOPNOTSUPP; 506 return put_user(wdd->timeout, p); 507 case WDIOC_GETTIMELEFT: 508 err = watchdog_get_timeleft(wdd, &val); 509 if (err) 510 return err; 511 return put_user(val, p); 512 default: 513 return -ENOTTY; 514 } 515 } 516 517 /* 518 * watchdog_open: open the /dev/watchdog* devices. 519 * @inode: inode of device 520 * @file: file handle to device 521 * 522 * When the /dev/watchdog* device gets opened, we start the watchdog. 523 * Watch out: the /dev/watchdog device is single open, so we make sure 524 * it can only be opened once. 525 */ 526 527 static int watchdog_open(struct inode *inode, struct file *file) 528 { 529 int err = -EBUSY; 530 struct watchdog_device *wdd; 531 532 /* Get the corresponding watchdog device */ 533 if (imajor(inode) == MISC_MAJOR) 534 wdd = old_wdd; 535 else 536 wdd = container_of(inode->i_cdev, struct watchdog_device, cdev); 537 538 /* the watchdog is single open! */ 539 if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status)) 540 return -EBUSY; 541 542 /* 543 * If the /dev/watchdog device is open, we don't want the module 544 * to be unloaded. 545 */ 546 if (!try_module_get(wdd->ops->owner)) 547 goto out; 548 549 err = watchdog_start(wdd); 550 if (err < 0) 551 goto out_mod; 552 553 file->private_data = wdd; 554 555 if (wdd->ops->ref) 556 wdd->ops->ref(wdd); 557 558 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ 559 return nonseekable_open(inode, file); 560 561 out_mod: 562 module_put(wdd->ops->owner); 563 out: 564 clear_bit(WDOG_DEV_OPEN, &wdd->status); 565 return err; 566 } 567 568 /* 569 * watchdog_release: release the watchdog device. 570 * @inode: inode of device 571 * @file: file handle to device 572 * 573 * This is the code for when /dev/watchdog gets closed. We will only 574 * stop the watchdog when we have received the magic char (and nowayout 575 * was not set), else the watchdog will keep running. 576 */ 577 578 static int watchdog_release(struct inode *inode, struct file *file) 579 { 580 struct watchdog_device *wdd = file->private_data; 581 int err = -EBUSY; 582 583 /* 584 * We only stop the watchdog if we received the magic character 585 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then 586 * watchdog_stop will fail. 587 */ 588 if (!test_bit(WDOG_ACTIVE, &wdd->status)) 589 err = 0; 590 else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) || 591 !(wdd->info->options & WDIOF_MAGICCLOSE)) 592 err = watchdog_stop(wdd); 593 594 /* If the watchdog was not stopped, send a keepalive ping */ 595 if (err < 0) { 596 mutex_lock(&wdd->lock); 597 if (!test_bit(WDOG_UNREGISTERED, &wdd->status)) 598 dev_crit(wdd->dev, "watchdog did not stop!\n"); 599 mutex_unlock(&wdd->lock); 600 watchdog_ping(wdd); 601 } 602 603 /* Allow the owner module to be unloaded again */ 604 module_put(wdd->ops->owner); 605 606 /* make sure that /dev/watchdog can be re-opened */ 607 clear_bit(WDOG_DEV_OPEN, &wdd->status); 608 609 /* Note wdd may be gone after this, do not use after this! */ 610 if (wdd->ops->unref) 611 wdd->ops->unref(wdd); 612 613 return 0; 614 } 615 616 static const struct file_operations watchdog_fops = { 617 .owner = THIS_MODULE, 618 .write = watchdog_write, 619 .unlocked_ioctl = watchdog_ioctl, 620 .open = watchdog_open, 621 .release = watchdog_release, 622 }; 623 624 static struct miscdevice watchdog_miscdev = { 625 .minor = WATCHDOG_MINOR, 626 .name = "watchdog", 627 .fops = &watchdog_fops, 628 }; 629 630 /* 631 * watchdog_dev_register: register a watchdog device 632 * @wdd: watchdog device 633 * 634 * Register a watchdog device including handling the legacy 635 * /dev/watchdog node. /dev/watchdog is actually a miscdevice and 636 * thus we set it up like that. 637 */ 638 639 int watchdog_dev_register(struct watchdog_device *wdd) 640 { 641 int err, devno; 642 643 if (wdd->id == 0) { 644 old_wdd = wdd; 645 watchdog_miscdev.parent = wdd->parent; 646 err = misc_register(&watchdog_miscdev); 647 if (err != 0) { 648 pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n", 649 wdd->info->identity, WATCHDOG_MINOR, err); 650 if (err == -EBUSY) 651 pr_err("%s: a legacy watchdog module is probably present.\n", 652 wdd->info->identity); 653 old_wdd = NULL; 654 return err; 655 } 656 } 657 658 /* Fill in the data structures */ 659 devno = MKDEV(MAJOR(watchdog_devt), wdd->id); 660 cdev_init(&wdd->cdev, &watchdog_fops); 661 wdd->cdev.owner = wdd->ops->owner; 662 663 /* Add the device */ 664 err = cdev_add(&wdd->cdev, devno, 1); 665 if (err) { 666 pr_err("watchdog%d unable to add device %d:%d\n", 667 wdd->id, MAJOR(watchdog_devt), wdd->id); 668 if (wdd->id == 0) { 669 misc_deregister(&watchdog_miscdev); 670 old_wdd = NULL; 671 } 672 } 673 return err; 674 } 675 676 /* 677 * watchdog_dev_unregister: unregister a watchdog device 678 * @watchdog: watchdog device 679 * 680 * Unregister the watchdog and if needed the legacy /dev/watchdog device. 681 */ 682 683 int watchdog_dev_unregister(struct watchdog_device *wdd) 684 { 685 mutex_lock(&wdd->lock); 686 set_bit(WDOG_UNREGISTERED, &wdd->status); 687 mutex_unlock(&wdd->lock); 688 689 cdev_del(&wdd->cdev); 690 if (wdd->id == 0) { 691 misc_deregister(&watchdog_miscdev); 692 old_wdd = NULL; 693 } 694 return 0; 695 } 696 697 static struct class watchdog_class = { 698 .name = "watchdog", 699 .owner = THIS_MODULE, 700 .dev_groups = wdt_groups, 701 }; 702 703 /* 704 * watchdog_dev_init: init dev part of watchdog core 705 * 706 * Allocate a range of chardev nodes to use for watchdog devices 707 */ 708 709 struct class * __init watchdog_dev_init(void) 710 { 711 int err; 712 713 err = class_register(&watchdog_class); 714 if (err < 0) { 715 pr_err("couldn't register class\n"); 716 return ERR_PTR(err); 717 } 718 719 err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog"); 720 if (err < 0) { 721 pr_err("watchdog: unable to allocate char dev region\n"); 722 class_unregister(&watchdog_class); 723 return ERR_PTR(err); 724 } 725 726 return &watchdog_class; 727 } 728 729 /* 730 * watchdog_dev_exit: exit dev part of watchdog core 731 * 732 * Release the range of chardev nodes used for watchdog devices 733 */ 734 735 void __exit watchdog_dev_exit(void) 736 { 737 unregister_chrdev_region(watchdog_devt, MAX_DOGS); 738 class_unregister(&watchdog_class); 739 } 740