1 /* 2 * watchdog_dev.c 3 * 4 * (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>, 5 * All Rights Reserved. 6 * 7 * (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>. 8 * 9 * 10 * This source code is part of the generic code that can be used 11 * by all the watchdog timer drivers. 12 * 13 * This part of the generic code takes care of the following 14 * misc device: /dev/watchdog. 15 * 16 * Based on source code of the following authors: 17 * Matt Domsch <Matt_Domsch@dell.com>, 18 * Rob Radez <rob@osinvestor.com>, 19 * Rusty Lynch <rusty@linux.co.intel.com> 20 * Satyam Sharma <satyam@infradead.org> 21 * Randy Dunlap <randy.dunlap@oracle.com> 22 * 23 * This program is free software; you can redistribute it and/or 24 * modify it under the terms of the GNU General Public License 25 * as published by the Free Software Foundation; either version 26 * 2 of the License, or (at your option) any later version. 27 * 28 * Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw. 29 * admit liability nor provide warranty for any of this software. 30 * This material is provided "AS-IS" and at no charge. 31 */ 32 33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 34 35 #include <linux/module.h> /* For module stuff/... */ 36 #include <linux/types.h> /* For standard types (like size_t) */ 37 #include <linux/errno.h> /* For the -ENODEV/... values */ 38 #include <linux/kernel.h> /* For printk/panic/... */ 39 #include <linux/fs.h> /* For file operations */ 40 #include <linux/watchdog.h> /* For watchdog specific items */ 41 #include <linux/miscdevice.h> /* For handling misc devices */ 42 #include <linux/init.h> /* For __init/__exit/... */ 43 #include <linux/uaccess.h> /* For copy_to_user/put_user/... */ 44 45 #include "watchdog_core.h" 46 47 /* the dev_t structure to store the dynamically allocated watchdog devices */ 48 static dev_t watchdog_devt; 49 /* the watchdog device behind /dev/watchdog */ 50 static struct watchdog_device *old_wdd; 51 52 /* 53 * watchdog_ping: ping the watchdog. 54 * @wdd: the watchdog device to ping 55 * 56 * If the watchdog has no own ping operation then it needs to be 57 * restarted via the start operation. This wrapper function does 58 * exactly that. 59 * We only ping when the watchdog device is running. 60 */ 61 62 static int watchdog_ping(struct watchdog_device *wdd) 63 { 64 int err = 0; 65 66 mutex_lock(&wdd->lock); 67 68 if (test_bit(WDOG_UNREGISTERED, &wdd->status)) { 69 err = -ENODEV; 70 goto out_ping; 71 } 72 73 if (!watchdog_active(wdd)) 74 goto out_ping; 75 76 if (wdd->ops->ping) 77 err = wdd->ops->ping(wdd); /* ping the watchdog */ 78 else 79 err = wdd->ops->start(wdd); /* restart watchdog */ 80 81 out_ping: 82 mutex_unlock(&wdd->lock); 83 return err; 84 } 85 86 /* 87 * watchdog_start: wrapper to start the watchdog. 88 * @wdd: the watchdog device to start 89 * 90 * Start the watchdog if it is not active and mark it active. 91 * This function returns zero on success or a negative errno code for 92 * failure. 93 */ 94 95 static int watchdog_start(struct watchdog_device *wdd) 96 { 97 int err = 0; 98 99 mutex_lock(&wdd->lock); 100 101 if (test_bit(WDOG_UNREGISTERED, &wdd->status)) { 102 err = -ENODEV; 103 goto out_start; 104 } 105 106 if (watchdog_active(wdd)) 107 goto out_start; 108 109 err = wdd->ops->start(wdd); 110 if (err == 0) 111 set_bit(WDOG_ACTIVE, &wdd->status); 112 113 out_start: 114 mutex_unlock(&wdd->lock); 115 return err; 116 } 117 118 /* 119 * watchdog_stop: wrapper to stop the watchdog. 120 * @wdd: the watchdog device to stop 121 * 122 * Stop the watchdog if it is still active and unmark it active. 123 * This function returns zero on success or a negative errno code for 124 * failure. 125 * If the 'nowayout' feature was set, the watchdog cannot be stopped. 126 */ 127 128 static int watchdog_stop(struct watchdog_device *wdd) 129 { 130 int err = 0; 131 132 mutex_lock(&wdd->lock); 133 134 if (test_bit(WDOG_UNREGISTERED, &wdd->status)) { 135 err = -ENODEV; 136 goto out_stop; 137 } 138 139 if (!watchdog_active(wdd)) 140 goto out_stop; 141 142 if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) { 143 dev_info(wdd->dev, "nowayout prevents watchdog being stopped!\n"); 144 err = -EBUSY; 145 goto out_stop; 146 } 147 148 err = wdd->ops->stop(wdd); 149 if (err == 0) 150 clear_bit(WDOG_ACTIVE, &wdd->status); 151 152 out_stop: 153 mutex_unlock(&wdd->lock); 154 return err; 155 } 156 157 /* 158 * watchdog_get_status: wrapper to get the watchdog status 159 * @wdd: the watchdog device to get the status from 160 * @status: the status of the watchdog device 161 * 162 * Get the watchdog's status flags. 163 */ 164 165 static int watchdog_get_status(struct watchdog_device *wdd, 166 unsigned int *status) 167 { 168 int err = 0; 169 170 *status = 0; 171 if (!wdd->ops->status) 172 return -EOPNOTSUPP; 173 174 mutex_lock(&wdd->lock); 175 176 if (test_bit(WDOG_UNREGISTERED, &wdd->status)) { 177 err = -ENODEV; 178 goto out_status; 179 } 180 181 *status = wdd->ops->status(wdd); 182 183 out_status: 184 mutex_unlock(&wdd->lock); 185 return err; 186 } 187 188 /* 189 * watchdog_set_timeout: set the watchdog timer timeout 190 * @wdd: the watchdog device to set the timeout for 191 * @timeout: timeout to set in seconds 192 */ 193 194 static int watchdog_set_timeout(struct watchdog_device *wdd, 195 unsigned int timeout) 196 { 197 int err; 198 199 if (!wdd->ops->set_timeout || !(wdd->info->options & WDIOF_SETTIMEOUT)) 200 return -EOPNOTSUPP; 201 202 if (watchdog_timeout_invalid(wdd, timeout)) 203 return -EINVAL; 204 205 mutex_lock(&wdd->lock); 206 207 if (test_bit(WDOG_UNREGISTERED, &wdd->status)) { 208 err = -ENODEV; 209 goto out_timeout; 210 } 211 212 err = wdd->ops->set_timeout(wdd, timeout); 213 214 out_timeout: 215 mutex_unlock(&wdd->lock); 216 return err; 217 } 218 219 /* 220 * watchdog_get_timeleft: wrapper to get the time left before a reboot 221 * @wdd: the watchdog device to get the remaining time from 222 * @timeleft: the time that's left 223 * 224 * Get the time before a watchdog will reboot (if not pinged). 225 */ 226 227 static int watchdog_get_timeleft(struct watchdog_device *wdd, 228 unsigned int *timeleft) 229 { 230 int err = 0; 231 232 *timeleft = 0; 233 if (!wdd->ops->get_timeleft) 234 return -EOPNOTSUPP; 235 236 mutex_lock(&wdd->lock); 237 238 if (test_bit(WDOG_UNREGISTERED, &wdd->status)) { 239 err = -ENODEV; 240 goto out_timeleft; 241 } 242 243 *timeleft = wdd->ops->get_timeleft(wdd); 244 245 out_timeleft: 246 mutex_unlock(&wdd->lock); 247 return err; 248 } 249 250 /* 251 * watchdog_ioctl_op: call the watchdog drivers ioctl op if defined 252 * @wdd: the watchdog device to do the ioctl on 253 * @cmd: watchdog command 254 * @arg: argument pointer 255 */ 256 257 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd, 258 unsigned long arg) 259 { 260 int err; 261 262 if (!wdd->ops->ioctl) 263 return -ENOIOCTLCMD; 264 265 mutex_lock(&wdd->lock); 266 267 if (test_bit(WDOG_UNREGISTERED, &wdd->status)) { 268 err = -ENODEV; 269 goto out_ioctl; 270 } 271 272 err = wdd->ops->ioctl(wdd, cmd, arg); 273 274 out_ioctl: 275 mutex_unlock(&wdd->lock); 276 return err; 277 } 278 279 /* 280 * watchdog_write: writes to the watchdog. 281 * @file: file from VFS 282 * @data: user address of data 283 * @len: length of data 284 * @ppos: pointer to the file offset 285 * 286 * A write to a watchdog device is defined as a keepalive ping. 287 * Writing the magic 'V' sequence allows the next close to turn 288 * off the watchdog (if 'nowayout' is not set). 289 */ 290 291 static ssize_t watchdog_write(struct file *file, const char __user *data, 292 size_t len, loff_t *ppos) 293 { 294 struct watchdog_device *wdd = file->private_data; 295 size_t i; 296 char c; 297 298 if (len == 0) 299 return 0; 300 301 /* 302 * Note: just in case someone wrote the magic character 303 * five months ago... 304 */ 305 clear_bit(WDOG_ALLOW_RELEASE, &wdd->status); 306 307 /* scan to see whether or not we got the magic character */ 308 for (i = 0; i != len; i++) { 309 if (get_user(c, data + i)) 310 return -EFAULT; 311 if (c == 'V') 312 set_bit(WDOG_ALLOW_RELEASE, &wdd->status); 313 } 314 315 /* someone wrote to us, so we send the watchdog a keepalive ping */ 316 watchdog_ping(wdd); 317 318 return len; 319 } 320 321 /* 322 * watchdog_ioctl: handle the different ioctl's for the watchdog device. 323 * @file: file handle to the device 324 * @cmd: watchdog command 325 * @arg: argument pointer 326 * 327 * The watchdog API defines a common set of functions for all watchdogs 328 * according to their available features. 329 */ 330 331 static long watchdog_ioctl(struct file *file, unsigned int cmd, 332 unsigned long arg) 333 { 334 struct watchdog_device *wdd = file->private_data; 335 void __user *argp = (void __user *)arg; 336 int __user *p = argp; 337 unsigned int val; 338 int err; 339 340 err = watchdog_ioctl_op(wdd, cmd, arg); 341 if (err != -ENOIOCTLCMD) 342 return err; 343 344 switch (cmd) { 345 case WDIOC_GETSUPPORT: 346 return copy_to_user(argp, wdd->info, 347 sizeof(struct watchdog_info)) ? -EFAULT : 0; 348 case WDIOC_GETSTATUS: 349 err = watchdog_get_status(wdd, &val); 350 if (err == -ENODEV) 351 return err; 352 return put_user(val, p); 353 case WDIOC_GETBOOTSTATUS: 354 return put_user(wdd->bootstatus, p); 355 case WDIOC_SETOPTIONS: 356 if (get_user(val, p)) 357 return -EFAULT; 358 if (val & WDIOS_DISABLECARD) { 359 err = watchdog_stop(wdd); 360 if (err < 0) 361 return err; 362 } 363 if (val & WDIOS_ENABLECARD) { 364 err = watchdog_start(wdd); 365 if (err < 0) 366 return err; 367 } 368 return 0; 369 case WDIOC_KEEPALIVE: 370 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) 371 return -EOPNOTSUPP; 372 watchdog_ping(wdd); 373 return 0; 374 case WDIOC_SETTIMEOUT: 375 if (get_user(val, p)) 376 return -EFAULT; 377 err = watchdog_set_timeout(wdd, val); 378 if (err < 0) 379 return err; 380 /* If the watchdog is active then we send a keepalive ping 381 * to make sure that the watchdog keep's running (and if 382 * possible that it takes the new timeout) */ 383 watchdog_ping(wdd); 384 /* Fall */ 385 case WDIOC_GETTIMEOUT: 386 /* timeout == 0 means that we don't know the timeout */ 387 if (wdd->timeout == 0) 388 return -EOPNOTSUPP; 389 return put_user(wdd->timeout, p); 390 case WDIOC_GETTIMELEFT: 391 err = watchdog_get_timeleft(wdd, &val); 392 if (err) 393 return err; 394 return put_user(val, p); 395 default: 396 return -ENOTTY; 397 } 398 } 399 400 /* 401 * watchdog_open: open the /dev/watchdog* devices. 402 * @inode: inode of device 403 * @file: file handle to device 404 * 405 * When the /dev/watchdog* device gets opened, we start the watchdog. 406 * Watch out: the /dev/watchdog device is single open, so we make sure 407 * it can only be opened once. 408 */ 409 410 static int watchdog_open(struct inode *inode, struct file *file) 411 { 412 int err = -EBUSY; 413 struct watchdog_device *wdd; 414 415 /* Get the corresponding watchdog device */ 416 if (imajor(inode) == MISC_MAJOR) 417 wdd = old_wdd; 418 else 419 wdd = container_of(inode->i_cdev, struct watchdog_device, cdev); 420 421 /* the watchdog is single open! */ 422 if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status)) 423 return -EBUSY; 424 425 /* 426 * If the /dev/watchdog device is open, we don't want the module 427 * to be unloaded. 428 */ 429 if (!try_module_get(wdd->ops->owner)) 430 goto out; 431 432 err = watchdog_start(wdd); 433 if (err < 0) 434 goto out_mod; 435 436 file->private_data = wdd; 437 438 if (wdd->ops->ref) 439 wdd->ops->ref(wdd); 440 441 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ 442 return nonseekable_open(inode, file); 443 444 out_mod: 445 module_put(wdd->ops->owner); 446 out: 447 clear_bit(WDOG_DEV_OPEN, &wdd->status); 448 return err; 449 } 450 451 /* 452 * watchdog_release: release the watchdog device. 453 * @inode: inode of device 454 * @file: file handle to device 455 * 456 * This is the code for when /dev/watchdog gets closed. We will only 457 * stop the watchdog when we have received the magic char (and nowayout 458 * was not set), else the watchdog will keep running. 459 */ 460 461 static int watchdog_release(struct inode *inode, struct file *file) 462 { 463 struct watchdog_device *wdd = file->private_data; 464 int err = -EBUSY; 465 466 /* 467 * We only stop the watchdog if we received the magic character 468 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then 469 * watchdog_stop will fail. 470 */ 471 if (!test_bit(WDOG_ACTIVE, &wdd->status)) 472 err = 0; 473 else 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 * @wdd: 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 *wdd) 523 { 524 int err, devno; 525 526 if (wdd->id == 0) { 527 old_wdd = wdd; 528 watchdog_miscdev.parent = wdd->parent; 529 err = misc_register(&watchdog_miscdev); 530 if (err != 0) { 531 pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n", 532 wdd->info->identity, WATCHDOG_MINOR, err); 533 if (err == -EBUSY) 534 pr_err("%s: a legacy watchdog module is probably present.\n", 535 wdd->info->identity); 536 old_wdd = NULL; 537 return err; 538 } 539 } 540 541 /* Fill in the data structures */ 542 devno = MKDEV(MAJOR(watchdog_devt), wdd->id); 543 cdev_init(&wdd->cdev, &watchdog_fops); 544 wdd->cdev.owner = wdd->ops->owner; 545 546 /* Add the device */ 547 err = cdev_add(&wdd->cdev, devno, 1); 548 if (err) { 549 pr_err("watchdog%d unable to add device %d:%d\n", 550 wdd->id, MAJOR(watchdog_devt), wdd->id); 551 if (wdd->id == 0) { 552 misc_deregister(&watchdog_miscdev); 553 old_wdd = NULL; 554 } 555 } 556 return err; 557 } 558 559 /* 560 * watchdog_dev_unregister: unregister a watchdog device 561 * @watchdog: watchdog device 562 * 563 * Unregister the watchdog and if needed the legacy /dev/watchdog device. 564 */ 565 566 int watchdog_dev_unregister(struct watchdog_device *wdd) 567 { 568 mutex_lock(&wdd->lock); 569 set_bit(WDOG_UNREGISTERED, &wdd->status); 570 mutex_unlock(&wdd->lock); 571 572 cdev_del(&wdd->cdev); 573 if (wdd->id == 0) { 574 misc_deregister(&watchdog_miscdev); 575 old_wdd = NULL; 576 } 577 return 0; 578 } 579 580 /* 581 * watchdog_dev_init: init dev part of watchdog core 582 * 583 * Allocate a range of chardev nodes to use for watchdog devices 584 */ 585 586 int __init watchdog_dev_init(void) 587 { 588 int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog"); 589 if (err < 0) 590 pr_err("watchdog: unable to allocate char dev region\n"); 591 return err; 592 } 593 594 /* 595 * watchdog_dev_exit: exit dev part of watchdog core 596 * 597 * Release the range of chardev nodes used for watchdog devices 598 */ 599 600 void __exit watchdog_dev_exit(void) 601 { 602 unregister_chrdev_region(watchdog_devt, MAX_DOGS); 603 } 604