1 /* 2 * watchdog_dev.c 3 * 4 * (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>, 5 * All Rights Reserved. 6 * 7 * (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>. 8 * 9 * 10 * This source code is part of the generic code that can be used 11 * by all the watchdog timer drivers. 12 * 13 * This part of the generic code takes care of the following 14 * misc device: /dev/watchdog. 15 * 16 * Based on source code of the following authors: 17 * Matt Domsch <Matt_Domsch@dell.com>, 18 * Rob Radez <rob@osinvestor.com>, 19 * Rusty Lynch <rusty@linux.co.intel.com> 20 * Satyam Sharma <satyam@infradead.org> 21 * Randy Dunlap <randy.dunlap@oracle.com> 22 * 23 * This program is free software; you can redistribute it and/or 24 * modify it under the terms of the GNU General Public License 25 * as published by the Free Software Foundation; either version 26 * 2 of the License, or (at your option) any later version. 27 * 28 * Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw. 29 * admit liability nor provide warranty for any of this software. 30 * This material is provided "AS-IS" and at no charge. 31 */ 32 33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 34 35 #include <linux/module.h> /* For module stuff/... */ 36 #include <linux/types.h> /* For standard types (like size_t) */ 37 #include <linux/errno.h> /* For the -ENODEV/... values */ 38 #include <linux/kernel.h> /* For printk/panic/... */ 39 #include <linux/fs.h> /* For file operations */ 40 #include <linux/watchdog.h> /* For watchdog specific items */ 41 #include <linux/miscdevice.h> /* For handling misc devices */ 42 #include <linux/init.h> /* For __init/__exit/... */ 43 #include <linux/uaccess.h> /* For copy_to_user/put_user/... */ 44 45 #include "watchdog_core.h" 46 47 /* the dev_t structure to store the dynamically allocated watchdog devices */ 48 static dev_t watchdog_devt; 49 /* the watchdog device behind /dev/watchdog */ 50 static struct watchdog_device *old_wdd; 51 52 /* 53 * watchdog_ping: ping the watchdog. 54 * @wddev: the watchdog device to ping 55 * 56 * If the watchdog has no own ping operation then it needs to be 57 * restarted via the start operation. This wrapper function does 58 * exactly that. 59 * We only ping when the watchdog device is running. 60 */ 61 62 static int watchdog_ping(struct watchdog_device *wddev) 63 { 64 int err = 0; 65 66 mutex_lock(&wddev->lock); 67 68 if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { 69 err = -ENODEV; 70 goto out_ping; 71 } 72 73 if (!watchdog_active(wddev)) 74 goto out_ping; 75 76 if (wddev->ops->ping) 77 err = wddev->ops->ping(wddev); /* ping the watchdog */ 78 else 79 err = wddev->ops->start(wddev); /* restart watchdog */ 80 81 out_ping: 82 mutex_unlock(&wddev->lock); 83 return err; 84 } 85 86 /* 87 * watchdog_start: wrapper to start the watchdog. 88 * @wddev: the watchdog device to start 89 * 90 * Start the watchdog if it is not active and mark it active. 91 * This function returns zero on success or a negative errno code for 92 * failure. 93 */ 94 95 static int watchdog_start(struct watchdog_device *wddev) 96 { 97 int err = 0; 98 99 mutex_lock(&wddev->lock); 100 101 if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { 102 err = -ENODEV; 103 goto out_start; 104 } 105 106 if (watchdog_active(wddev)) 107 goto out_start; 108 109 err = wddev->ops->start(wddev); 110 if (err == 0) 111 set_bit(WDOG_ACTIVE, &wddev->status); 112 113 out_start: 114 mutex_unlock(&wddev->lock); 115 return err; 116 } 117 118 /* 119 * watchdog_stop: wrapper to stop the watchdog. 120 * @wddev: the watchdog device to stop 121 * 122 * Stop the watchdog if it is still active and unmark it active. 123 * This function returns zero on success or a negative errno code for 124 * failure. 125 * If the 'nowayout' feature was set, the watchdog cannot be stopped. 126 */ 127 128 static int watchdog_stop(struct watchdog_device *wddev) 129 { 130 int err = 0; 131 132 mutex_lock(&wddev->lock); 133 134 if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { 135 err = -ENODEV; 136 goto out_stop; 137 } 138 139 if (!watchdog_active(wddev)) 140 goto out_stop; 141 142 if (test_bit(WDOG_NO_WAY_OUT, &wddev->status)) { 143 dev_info(wddev->dev, "nowayout prevents watchdog being stopped!\n"); 144 err = -EBUSY; 145 goto out_stop; 146 } 147 148 err = wddev->ops->stop(wddev); 149 if (err == 0) 150 clear_bit(WDOG_ACTIVE, &wddev->status); 151 152 out_stop: 153 mutex_unlock(&wddev->lock); 154 return err; 155 } 156 157 /* 158 * watchdog_get_status: wrapper to get the watchdog status 159 * @wddev: the watchdog device to get the status from 160 * @status: the status of the watchdog device 161 * 162 * Get the watchdog's status flags. 163 */ 164 165 static int watchdog_get_status(struct watchdog_device *wddev, 166 unsigned int *status) 167 { 168 int err = 0; 169 170 *status = 0; 171 if (!wddev->ops->status) 172 return -EOPNOTSUPP; 173 174 mutex_lock(&wddev->lock); 175 176 if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { 177 err = -ENODEV; 178 goto out_status; 179 } 180 181 *status = wddev->ops->status(wddev); 182 183 out_status: 184 mutex_unlock(&wddev->lock); 185 return err; 186 } 187 188 /* 189 * watchdog_set_timeout: set the watchdog timer timeout 190 * @wddev: the watchdog device to set the timeout for 191 * @timeout: timeout to set in seconds 192 */ 193 194 static int watchdog_set_timeout(struct watchdog_device *wddev, 195 unsigned int timeout) 196 { 197 int err; 198 199 if ((wddev->ops->set_timeout == NULL) || 200 !(wddev->info->options & WDIOF_SETTIMEOUT)) 201 return -EOPNOTSUPP; 202 203 if ((wddev->max_timeout != 0) && 204 (timeout < wddev->min_timeout || timeout > wddev->max_timeout)) 205 return -EINVAL; 206 207 mutex_lock(&wddev->lock); 208 209 if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { 210 err = -ENODEV; 211 goto out_timeout; 212 } 213 214 err = wddev->ops->set_timeout(wddev, timeout); 215 216 out_timeout: 217 mutex_unlock(&wddev->lock); 218 return err; 219 } 220 221 /* 222 * watchdog_get_timeleft: wrapper to get the time left before a reboot 223 * @wddev: the watchdog device to get the remaining time from 224 * @timeleft: the time that's left 225 * 226 * Get the time before a watchdog will reboot (if not pinged). 227 */ 228 229 static int watchdog_get_timeleft(struct watchdog_device *wddev, 230 unsigned int *timeleft) 231 { 232 int err = 0; 233 234 *timeleft = 0; 235 if (!wddev->ops->get_timeleft) 236 return -EOPNOTSUPP; 237 238 mutex_lock(&wddev->lock); 239 240 if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { 241 err = -ENODEV; 242 goto out_timeleft; 243 } 244 245 *timeleft = wddev->ops->get_timeleft(wddev); 246 247 out_timeleft: 248 mutex_unlock(&wddev->lock); 249 return err; 250 } 251 252 /* 253 * watchdog_ioctl_op: call the watchdog drivers ioctl op if defined 254 * @wddev: the watchdog device to do the ioctl on 255 * @cmd: watchdog command 256 * @arg: argument pointer 257 */ 258 259 static int watchdog_ioctl_op(struct watchdog_device *wddev, unsigned int cmd, 260 unsigned long arg) 261 { 262 int err; 263 264 if (!wddev->ops->ioctl) 265 return -ENOIOCTLCMD; 266 267 mutex_lock(&wddev->lock); 268 269 if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { 270 err = -ENODEV; 271 goto out_ioctl; 272 } 273 274 err = wddev->ops->ioctl(wddev, cmd, arg); 275 276 out_ioctl: 277 mutex_unlock(&wddev->lock); 278 return err; 279 } 280 281 /* 282 * watchdog_write: writes to the watchdog. 283 * @file: file from VFS 284 * @data: user address of data 285 * @len: length of data 286 * @ppos: pointer to the file offset 287 * 288 * A write to a watchdog device is defined as a keepalive ping. 289 * Writing the magic 'V' sequence allows the next close to turn 290 * off the watchdog (if 'nowayout' is not set). 291 */ 292 293 static ssize_t watchdog_write(struct file *file, const char __user *data, 294 size_t len, loff_t *ppos) 295 { 296 struct watchdog_device *wdd = file->private_data; 297 size_t i; 298 char c; 299 300 if (len == 0) 301 return 0; 302 303 /* 304 * Note: just in case someone wrote the magic character 305 * five months ago... 306 */ 307 clear_bit(WDOG_ALLOW_RELEASE, &wdd->status); 308 309 /* scan to see whether or not we got the magic character */ 310 for (i = 0; i != len; i++) { 311 if (get_user(c, data + i)) 312 return -EFAULT; 313 if (c == 'V') 314 set_bit(WDOG_ALLOW_RELEASE, &wdd->status); 315 } 316 317 /* someone wrote to us, so we send the watchdog a keepalive ping */ 318 watchdog_ping(wdd); 319 320 return len; 321 } 322 323 /* 324 * watchdog_ioctl: handle the different ioctl's for the watchdog device. 325 * @file: file handle to the device 326 * @cmd: watchdog command 327 * @arg: argument pointer 328 * 329 * The watchdog API defines a common set of functions for all watchdogs 330 * according to their available features. 331 */ 332 333 static long watchdog_ioctl(struct file *file, unsigned int cmd, 334 unsigned long arg) 335 { 336 struct watchdog_device *wdd = file->private_data; 337 void __user *argp = (void __user *)arg; 338 int __user *p = argp; 339 unsigned int val; 340 int err; 341 342 err = watchdog_ioctl_op(wdd, cmd, arg); 343 if (err != -ENOIOCTLCMD) 344 return err; 345 346 switch (cmd) { 347 case WDIOC_GETSUPPORT: 348 return copy_to_user(argp, wdd->info, 349 sizeof(struct watchdog_info)) ? -EFAULT : 0; 350 case WDIOC_GETSTATUS: 351 err = watchdog_get_status(wdd, &val); 352 if (err == -ENODEV) 353 return err; 354 return put_user(val, p); 355 case WDIOC_GETBOOTSTATUS: 356 return put_user(wdd->bootstatus, p); 357 case WDIOC_SETOPTIONS: 358 if (get_user(val, p)) 359 return -EFAULT; 360 if (val & WDIOS_DISABLECARD) { 361 err = watchdog_stop(wdd); 362 if (err < 0) 363 return err; 364 } 365 if (val & WDIOS_ENABLECARD) { 366 err = watchdog_start(wdd); 367 if (err < 0) 368 return err; 369 } 370 return 0; 371 case WDIOC_KEEPALIVE: 372 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) 373 return -EOPNOTSUPP; 374 watchdog_ping(wdd); 375 return 0; 376 case WDIOC_SETTIMEOUT: 377 if (get_user(val, p)) 378 return -EFAULT; 379 err = watchdog_set_timeout(wdd, val); 380 if (err < 0) 381 return err; 382 /* If the watchdog is active then we send a keepalive ping 383 * to make sure that the watchdog keep's running (and if 384 * possible that it takes the new timeout) */ 385 watchdog_ping(wdd); 386 /* Fall */ 387 case WDIOC_GETTIMEOUT: 388 /* timeout == 0 means that we don't know the timeout */ 389 if (wdd->timeout == 0) 390 return -EOPNOTSUPP; 391 return put_user(wdd->timeout, p); 392 case WDIOC_GETTIMELEFT: 393 err = watchdog_get_timeleft(wdd, &val); 394 if (err) 395 return err; 396 return put_user(val, p); 397 default: 398 return -ENOTTY; 399 } 400 } 401 402 /* 403 * watchdog_open: open the /dev/watchdog* devices. 404 * @inode: inode of device 405 * @file: file handle to device 406 * 407 * When the /dev/watchdog* device gets opened, we start the watchdog. 408 * Watch out: the /dev/watchdog device is single open, so we make sure 409 * it can only be opened once. 410 */ 411 412 static int watchdog_open(struct inode *inode, struct file *file) 413 { 414 int err = -EBUSY; 415 struct watchdog_device *wdd; 416 417 /* Get the corresponding watchdog device */ 418 if (imajor(inode) == MISC_MAJOR) 419 wdd = old_wdd; 420 else 421 wdd = container_of(inode->i_cdev, struct watchdog_device, cdev); 422 423 /* the watchdog is single open! */ 424 if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status)) 425 return -EBUSY; 426 427 /* 428 * If the /dev/watchdog device is open, we don't want the module 429 * to be unloaded. 430 */ 431 if (!try_module_get(wdd->ops->owner)) 432 goto out; 433 434 err = watchdog_start(wdd); 435 if (err < 0) 436 goto out_mod; 437 438 file->private_data = wdd; 439 440 if (wdd->ops->ref) 441 wdd->ops->ref(wdd); 442 443 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ 444 return nonseekable_open(inode, file); 445 446 out_mod: 447 module_put(wdd->ops->owner); 448 out: 449 clear_bit(WDOG_DEV_OPEN, &wdd->status); 450 return err; 451 } 452 453 /* 454 * watchdog_release: release the watchdog device. 455 * @inode: inode of device 456 * @file: file handle to device 457 * 458 * This is the code for when /dev/watchdog gets closed. We will only 459 * stop the watchdog when we have received the magic char (and nowayout 460 * was not set), else the watchdog will keep running. 461 */ 462 463 static int watchdog_release(struct inode *inode, struct file *file) 464 { 465 struct watchdog_device *wdd = file->private_data; 466 int err = -EBUSY; 467 468 /* 469 * We only stop the watchdog if we received the magic character 470 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then 471 * watchdog_stop will fail. 472 */ 473 if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) || 474 !(wdd->info->options & WDIOF_MAGICCLOSE)) 475 err = watchdog_stop(wdd); 476 477 /* If the watchdog was not stopped, send a keepalive ping */ 478 if (err < 0) { 479 mutex_lock(&wdd->lock); 480 if (!test_bit(WDOG_UNREGISTERED, &wdd->status)) 481 dev_crit(wdd->dev, "watchdog did not stop!\n"); 482 mutex_unlock(&wdd->lock); 483 watchdog_ping(wdd); 484 } 485 486 /* Allow the owner module to be unloaded again */ 487 module_put(wdd->ops->owner); 488 489 /* make sure that /dev/watchdog can be re-opened */ 490 clear_bit(WDOG_DEV_OPEN, &wdd->status); 491 492 /* Note wdd may be gone after this, do not use after this! */ 493 if (wdd->ops->unref) 494 wdd->ops->unref(wdd); 495 496 return 0; 497 } 498 499 static const struct file_operations watchdog_fops = { 500 .owner = THIS_MODULE, 501 .write = watchdog_write, 502 .unlocked_ioctl = watchdog_ioctl, 503 .open = watchdog_open, 504 .release = watchdog_release, 505 }; 506 507 static struct miscdevice watchdog_miscdev = { 508 .minor = WATCHDOG_MINOR, 509 .name = "watchdog", 510 .fops = &watchdog_fops, 511 }; 512 513 /* 514 * watchdog_dev_register: register a watchdog device 515 * @watchdog: watchdog device 516 * 517 * Register a watchdog device including handling the legacy 518 * /dev/watchdog node. /dev/watchdog is actually a miscdevice and 519 * thus we set it up like that. 520 */ 521 522 int watchdog_dev_register(struct watchdog_device *watchdog) 523 { 524 int err, devno; 525 526 if (watchdog->id == 0) { 527 watchdog_miscdev.parent = watchdog->parent; 528 err = misc_register(&watchdog_miscdev); 529 if (err != 0) { 530 pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n", 531 watchdog->info->identity, WATCHDOG_MINOR, err); 532 if (err == -EBUSY) 533 pr_err("%s: a legacy watchdog module is probably present.\n", 534 watchdog->info->identity); 535 return err; 536 } 537 old_wdd = watchdog; 538 } 539 540 /* Fill in the data structures */ 541 devno = MKDEV(MAJOR(watchdog_devt), watchdog->id); 542 cdev_init(&watchdog->cdev, &watchdog_fops); 543 watchdog->cdev.owner = watchdog->ops->owner; 544 545 /* Add the device */ 546 err = cdev_add(&watchdog->cdev, devno, 1); 547 if (err) { 548 pr_err("watchdog%d unable to add device %d:%d\n", 549 watchdog->id, MAJOR(watchdog_devt), watchdog->id); 550 if (watchdog->id == 0) { 551 misc_deregister(&watchdog_miscdev); 552 old_wdd = NULL; 553 } 554 } 555 return err; 556 } 557 558 /* 559 * watchdog_dev_unregister: unregister a watchdog device 560 * @watchdog: watchdog device 561 * 562 * Unregister the watchdog and if needed the legacy /dev/watchdog device. 563 */ 564 565 int watchdog_dev_unregister(struct watchdog_device *watchdog) 566 { 567 mutex_lock(&watchdog->lock); 568 set_bit(WDOG_UNREGISTERED, &watchdog->status); 569 mutex_unlock(&watchdog->lock); 570 571 cdev_del(&watchdog->cdev); 572 if (watchdog->id == 0) { 573 misc_deregister(&watchdog_miscdev); 574 old_wdd = NULL; 575 } 576 return 0; 577 } 578 579 /* 580 * watchdog_dev_init: init dev part of watchdog core 581 * 582 * Allocate a range of chardev nodes to use for watchdog devices 583 */ 584 585 int __init watchdog_dev_init(void) 586 { 587 int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog"); 588 if (err < 0) 589 pr_err("watchdog: unable to allocate char dev region\n"); 590 return err; 591 } 592 593 /* 594 * watchdog_dev_exit: exit dev part of watchdog core 595 * 596 * Release the range of chardev nodes used for watchdog devices 597 */ 598 599 void __exit watchdog_dev_exit(void) 600 { 601 unregister_chrdev_region(watchdog_devt, MAX_DOGS); 602 } 603