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