fs/debugfs/inode.c

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