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