1 /* 2 * file.c - part of debugfs, a tiny little debug file system 3 * 4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com> 5 * Copyright (C) 2004 IBM Inc. 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License version 9 * 2 as published by the Free Software Foundation. 10 * 11 * debugfs is for people to use instead of /proc or /sys. 12 * See Documentation/DocBook/kernel-api for more details. 13 * 14 */ 15 16 /* uncomment to get debug messages from the debug filesystem, ah the irony. */ 17 /* #define DEBUG */ 18 19 #include <linux/module.h> 20 #include <linux/fs.h> 21 #include <linux/mount.h> 22 #include <linux/pagemap.h> 23 #include <linux/init.h> 24 #include <linux/kobject.h> 25 #include <linux/namei.h> 26 #include <linux/debugfs.h> 27 #include <linux/fsnotify.h> 28 #include <linux/string.h> 29 #include <linux/magic.h> 30 31 static struct vfsmount *debugfs_mount; 32 static int debugfs_mount_count; 33 static bool debugfs_registered; 34 35 static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev, 36 void *data, const struct file_operations *fops) 37 38 { 39 struct inode *inode = new_inode(sb); 40 41 if (inode) { 42 inode->i_mode = mode; 43 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 44 switch (mode & S_IFMT) { 45 default: 46 init_special_inode(inode, mode, dev); 47 break; 48 case S_IFREG: 49 inode->i_fop = fops ? fops : &debugfs_file_operations; 50 inode->i_private = data; 51 break; 52 case S_IFLNK: 53 inode->i_op = &debugfs_link_operations; 54 inode->i_fop = fops; 55 inode->i_private = data; 56 break; 57 case S_IFDIR: 58 inode->i_op = &simple_dir_inode_operations; 59 inode->i_fop = fops ? fops : &simple_dir_operations; 60 inode->i_private = data; 61 62 /* directory inodes start off with i_nlink == 2 63 * (for "." entry) */ 64 inc_nlink(inode); 65 break; 66 } 67 } 68 return inode; 69 } 70 71 /* SMP-safe */ 72 static int debugfs_mknod(struct inode *dir, struct dentry *dentry, 73 int mode, dev_t dev, void *data, 74 const struct file_operations *fops) 75 { 76 struct inode *inode; 77 int error = -EPERM; 78 79 if (dentry->d_inode) 80 return -EEXIST; 81 82 inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops); 83 if (inode) { 84 d_instantiate(dentry, inode); 85 dget(dentry); 86 error = 0; 87 } 88 return error; 89 } 90 91 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode, 92 void *data, const struct file_operations *fops) 93 { 94 int res; 95 96 mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR; 97 res = debugfs_mknod(dir, dentry, mode, 0, data, fops); 98 if (!res) { 99 inc_nlink(dir); 100 fsnotify_mkdir(dir, dentry); 101 } 102 return res; 103 } 104 105 static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode, 106 void *data, const struct file_operations *fops) 107 { 108 mode = (mode & S_IALLUGO) | S_IFLNK; 109 return debugfs_mknod(dir, dentry, mode, 0, data, fops); 110 } 111 112 static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode, 113 void *data, const struct file_operations *fops) 114 { 115 int res; 116 117 mode = (mode & S_IALLUGO) | S_IFREG; 118 res = debugfs_mknod(dir, dentry, mode, 0, data, fops); 119 if (!res) 120 fsnotify_create(dir, dentry); 121 return res; 122 } 123 124 static inline int debugfs_positive(struct dentry *dentry) 125 { 126 return dentry->d_inode && !d_unhashed(dentry); 127 } 128 129 static int debug_fill_super(struct super_block *sb, void *data, int silent) 130 { 131 static struct tree_descr debug_files[] = {{""}}; 132 133 return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files); 134 } 135 136 static int debug_get_sb(struct file_system_type *fs_type, 137 int flags, const char *dev_name, 138 void *data, struct vfsmount *mnt) 139 { 140 return get_sb_single(fs_type, flags, data, debug_fill_super, mnt); 141 } 142 143 static struct file_system_type debug_fs_type = { 144 .owner = THIS_MODULE, 145 .name = "debugfs", 146 .get_sb = debug_get_sb, 147 .kill_sb = kill_litter_super, 148 }; 149 150 static int debugfs_create_by_name(const char *name, mode_t mode, 151 struct dentry *parent, 152 struct dentry **dentry, 153 void *data, 154 const struct file_operations *fops) 155 { 156 int error = 0; 157 158 /* If the parent is not specified, we create it in the root. 159 * We need the root dentry to do this, which is in the super 160 * block. A pointer to that is in the struct vfsmount that we 161 * have around. 162 */ 163 if (!parent) { 164 if (debugfs_mount && debugfs_mount->mnt_sb) { 165 parent = debugfs_mount->mnt_sb->s_root; 166 } 167 } 168 if (!parent) { 169 pr_debug("debugfs: Ah! can not find a parent!\n"); 170 return -EFAULT; 171 } 172 173 *dentry = NULL; 174 mutex_lock(&parent->d_inode->i_mutex); 175 *dentry = lookup_one_len(name, parent, strlen(name)); 176 if (!IS_ERR(*dentry)) { 177 switch (mode & S_IFMT) { 178 case S_IFDIR: 179 error = debugfs_mkdir(parent->d_inode, *dentry, mode, 180 data, fops); 181 break; 182 case S_IFLNK: 183 error = debugfs_link(parent->d_inode, *dentry, mode, 184 data, fops); 185 break; 186 default: 187 error = debugfs_create(parent->d_inode, *dentry, mode, 188 data, fops); 189 break; 190 } 191 dput(*dentry); 192 } else 193 error = PTR_ERR(*dentry); 194 mutex_unlock(&parent->d_inode->i_mutex); 195 196 return error; 197 } 198 199 /** 200 * debugfs_create_file - create a file in the debugfs filesystem 201 * @name: a pointer to a string containing the name of the file to create. 202 * @mode: the permission that the file should have. 203 * @parent: a pointer to the parent dentry for this file. This should be a 204 * directory dentry if set. If this paramater is NULL, then the 205 * file will be created in the root of the debugfs filesystem. 206 * @data: a pointer to something that the caller will want to get to later 207 * on. The inode.i_private pointer will point to this value on 208 * the open() call. 209 * @fops: a pointer to a struct file_operations that should be used for 210 * this file. 211 * 212 * This is the basic "create a file" function for debugfs. It allows for a 213 * wide range of flexibility in creating a file, or a directory (if you want 214 * to create a directory, the debugfs_create_dir() function is 215 * recommended to be used instead.) 216 * 217 * This function will return a pointer to a dentry if it succeeds. This 218 * pointer must be passed to the debugfs_remove() function when the file is 219 * to be removed (no automatic cleanup happens if your module is unloaded, 220 * you are responsible here.) If an error occurs, %NULL will be returned. 221 * 222 * If debugfs is not enabled in the kernel, the value -%ENODEV will be 223 * returned. 224 */ 225 struct dentry *debugfs_create_file(const char *name, mode_t mode, 226 struct dentry *parent, void *data, 227 const struct file_operations *fops) 228 { 229 struct dentry *dentry = NULL; 230 int error; 231 232 pr_debug("debugfs: creating file '%s'\n",name); 233 234 error = simple_pin_fs(&debug_fs_type, &debugfs_mount, 235 &debugfs_mount_count); 236 if (error) 237 goto exit; 238 239 error = debugfs_create_by_name(name, mode, parent, &dentry, 240 data, fops); 241 if (error) { 242 dentry = NULL; 243 simple_release_fs(&debugfs_mount, &debugfs_mount_count); 244 goto exit; 245 } 246 exit: 247 return dentry; 248 } 249 EXPORT_SYMBOL_GPL(debugfs_create_file); 250 251 /** 252 * debugfs_create_dir - create a directory in the debugfs filesystem 253 * @name: a pointer to a string containing the name of the directory to 254 * create. 255 * @parent: a pointer to the parent dentry for this file. This should be a 256 * directory dentry if set. If this paramater is NULL, then the 257 * directory will be created in the root of the debugfs filesystem. 258 * 259 * This function creates a directory in debugfs with the given name. 260 * 261 * This function will return a pointer to a dentry if it succeeds. This 262 * pointer must be passed to the debugfs_remove() function when the file is 263 * to be removed (no automatic cleanup happens if your module is unloaded, 264 * you are responsible here.) If an error occurs, %NULL will be returned. 265 * 266 * If debugfs is not enabled in the kernel, the value -%ENODEV will be 267 * returned. 268 */ 269 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent) 270 { 271 return debugfs_create_file(name, 272 S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO, 273 parent, NULL, NULL); 274 } 275 EXPORT_SYMBOL_GPL(debugfs_create_dir); 276 277 /** 278 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem 279 * @name: a pointer to a string containing the name of the symbolic link to 280 * create. 281 * @parent: a pointer to the parent dentry for this symbolic link. This 282 * should be a directory dentry if set. If this paramater is NULL, 283 * then the symbolic link will be created in the root of the debugfs 284 * filesystem. 285 * @target: a pointer to a string containing the path to the target of the 286 * symbolic link. 287 * 288 * This function creates a symbolic link with the given name in debugfs that 289 * links to the given target path. 290 * 291 * This function will return a pointer to a dentry if it succeeds. This 292 * pointer must be passed to the debugfs_remove() function when the symbolic 293 * link is to be removed (no automatic cleanup happens if your module is 294 * unloaded, you are responsible here.) If an error occurs, %NULL will be 295 * returned. 296 * 297 * If debugfs is not enabled in the kernel, the value -%ENODEV will be 298 * returned. 299 */ 300 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent, 301 const char *target) 302 { 303 struct dentry *result; 304 char *link; 305 306 link = kstrdup(target, GFP_KERNEL); 307 if (!link) 308 return NULL; 309 310 result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link, 311 NULL); 312 if (!result) 313 kfree(link); 314 return result; 315 } 316 EXPORT_SYMBOL_GPL(debugfs_create_symlink); 317 318 static void __debugfs_remove(struct dentry *dentry, struct dentry *parent) 319 { 320 int ret = 0; 321 322 if (debugfs_positive(dentry)) { 323 if (dentry->d_inode) { 324 dget(dentry); 325 switch (dentry->d_inode->i_mode & S_IFMT) { 326 case S_IFDIR: 327 ret = simple_rmdir(parent->d_inode, dentry); 328 break; 329 case S_IFLNK: 330 kfree(dentry->d_inode->i_private); 331 /* fall through */ 332 default: 333 simple_unlink(parent->d_inode, dentry); 334 break; 335 } 336 if (!ret) 337 d_delete(dentry); 338 dput(dentry); 339 } 340 } 341 } 342 343 /** 344 * debugfs_remove - removes a file or directory from the debugfs filesystem 345 * @dentry: a pointer to a the dentry of the file or directory to be 346 * removed. 347 * 348 * This function removes a file or directory in debugfs that was previously 349 * created with a call to another debugfs function (like 350 * debugfs_create_file() or variants thereof.) 351 * 352 * This function is required to be called in order for the file to be 353 * removed, no automatic cleanup of files will happen when a module is 354 * removed, you are responsible here. 355 */ 356 void debugfs_remove(struct dentry *dentry) 357 { 358 struct dentry *parent; 359 360 if (!dentry) 361 return; 362 363 parent = dentry->d_parent; 364 if (!parent || !parent->d_inode) 365 return; 366 367 mutex_lock(&parent->d_inode->i_mutex); 368 __debugfs_remove(dentry, parent); 369 mutex_unlock(&parent->d_inode->i_mutex); 370 simple_release_fs(&debugfs_mount, &debugfs_mount_count); 371 } 372 EXPORT_SYMBOL_GPL(debugfs_remove); 373 374 /** 375 * debugfs_remove_recursive - recursively removes a directory 376 * @dentry: a pointer to a the dentry of the directory to be removed. 377 * 378 * This function recursively removes a directory tree in debugfs that 379 * was previously created with a call to another debugfs function 380 * (like debugfs_create_file() or variants thereof.) 381 * 382 * This function is required to be called in order for the file to be 383 * removed, no automatic cleanup of files will happen when a module is 384 * removed, you are responsible here. 385 */ 386 void debugfs_remove_recursive(struct dentry *dentry) 387 { 388 struct dentry *child; 389 struct dentry *parent; 390 391 if (!dentry) 392 return; 393 394 parent = dentry->d_parent; 395 if (!parent || !parent->d_inode) 396 return; 397 398 parent = dentry; 399 mutex_lock(&parent->d_inode->i_mutex); 400 401 while (1) { 402 /* 403 * When all dentries under "parent" has been removed, 404 * walk up the tree until we reach our starting point. 405 */ 406 if (list_empty(&parent->d_subdirs)) { 407 mutex_unlock(&parent->d_inode->i_mutex); 408 if (parent == dentry) 409 break; 410 parent = parent->d_parent; 411 mutex_lock(&parent->d_inode->i_mutex); 412 } 413 child = list_entry(parent->d_subdirs.next, struct dentry, 414 d_u.d_child); 415 next_sibling: 416 417 /* 418 * If "child" isn't empty, walk down the tree and 419 * remove all its descendants first. 420 */ 421 if (!list_empty(&child->d_subdirs)) { 422 mutex_unlock(&parent->d_inode->i_mutex); 423 parent = child; 424 mutex_lock(&parent->d_inode->i_mutex); 425 continue; 426 } 427 __debugfs_remove(child, parent); 428 if (parent->d_subdirs.next == &child->d_u.d_child) { 429 /* 430 * Try the next sibling. 431 */ 432 if (child->d_u.d_child.next != &parent->d_subdirs) { 433 child = list_entry(child->d_u.d_child.next, 434 struct dentry, 435 d_u.d_child); 436 goto next_sibling; 437 } 438 439 /* 440 * Avoid infinite loop if we fail to remove 441 * one dentry. 442 */ 443 mutex_unlock(&parent->d_inode->i_mutex); 444 break; 445 } 446 simple_release_fs(&debugfs_mount, &debugfs_mount_count); 447 } 448 449 parent = dentry->d_parent; 450 mutex_lock(&parent->d_inode->i_mutex); 451 __debugfs_remove(dentry, parent); 452 mutex_unlock(&parent->d_inode->i_mutex); 453 simple_release_fs(&debugfs_mount, &debugfs_mount_count); 454 } 455 EXPORT_SYMBOL_GPL(debugfs_remove_recursive); 456 457 /** 458 * debugfs_rename - rename a file/directory in the debugfs filesystem 459 * @old_dir: a pointer to the parent dentry for the renamed object. This 460 * should be a directory dentry. 461 * @old_dentry: dentry of an object to be renamed. 462 * @new_dir: a pointer to the parent dentry where the object should be 463 * moved. This should be a directory dentry. 464 * @new_name: a pointer to a string containing the target name. 465 * 466 * This function renames a file/directory in debugfs. The target must not 467 * exist for rename to succeed. 468 * 469 * This function will return a pointer to old_dentry (which is updated to 470 * reflect renaming) if it succeeds. If an error occurs, %NULL will be 471 * returned. 472 * 473 * If debugfs is not enabled in the kernel, the value -%ENODEV will be 474 * returned. 475 */ 476 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry, 477 struct dentry *new_dir, const char *new_name) 478 { 479 int error; 480 struct dentry *dentry = NULL, *trap; 481 const char *old_name; 482 483 trap = lock_rename(new_dir, old_dir); 484 /* Source or destination directories don't exist? */ 485 if (!old_dir->d_inode || !new_dir->d_inode) 486 goto exit; 487 /* Source does not exist, cyclic rename, or mountpoint? */ 488 if (!old_dentry->d_inode || old_dentry == trap || 489 d_mountpoint(old_dentry)) 490 goto exit; 491 dentry = lookup_one_len(new_name, new_dir, strlen(new_name)); 492 /* Lookup failed, cyclic rename or target exists? */ 493 if (IS_ERR(dentry) || dentry == trap || dentry->d_inode) 494 goto exit; 495 496 old_name = fsnotify_oldname_init(old_dentry->d_name.name); 497 498 error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode, 499 dentry); 500 if (error) { 501 fsnotify_oldname_free(old_name); 502 goto exit; 503 } 504 d_move(old_dentry, dentry); 505 fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name, 506 old_dentry->d_name.name, S_ISDIR(old_dentry->d_inode->i_mode), 507 NULL, old_dentry); 508 fsnotify_oldname_free(old_name); 509 unlock_rename(new_dir, old_dir); 510 dput(dentry); 511 return old_dentry; 512 exit: 513 if (dentry && !IS_ERR(dentry)) 514 dput(dentry); 515 unlock_rename(new_dir, old_dir); 516 return NULL; 517 } 518 EXPORT_SYMBOL_GPL(debugfs_rename); 519 520 /** 521 * debugfs_initialized - Tells whether debugfs has been registered 522 */ 523 bool debugfs_initialized(void) 524 { 525 return debugfs_registered; 526 } 527 EXPORT_SYMBOL_GPL(debugfs_initialized); 528 529 530 static struct kobject *debug_kobj; 531 532 static int __init debugfs_init(void) 533 { 534 int retval; 535 536 debug_kobj = kobject_create_and_add("debug", kernel_kobj); 537 if (!debug_kobj) 538 return -EINVAL; 539 540 retval = register_filesystem(&debug_fs_type); 541 if (retval) 542 kobject_put(debug_kobj); 543 else 544 debugfs_registered = true; 545 546 return retval; 547 } 548 549 static void __exit debugfs_exit(void) 550 { 551 debugfs_registered = false; 552 553 simple_release_fs(&debugfs_mount, &debugfs_mount_count); 554 unregister_filesystem(&debug_fs_type); 555 kobject_put(debug_kobj); 556 } 557 558 core_initcall(debugfs_init); 559 module_exit(debugfs_exit); 560 MODULE_LICENSE("GPL"); 561 562