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