fs/debugfs/inode.c

   1 /*
   2  *  inode.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 #include <linux/module.h>
  17 #include <linux/fs.h>
  18 #include <linux/mount.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/init.h>
  21 #include <linux/kobject.h>
  22 #include <linux/namei.h>
  23 #include <linux/debugfs.h>
  24 #include <linux/fsnotify.h>
  25 #include <linux/string.h>
  26 #include <linux/seq_file.h>
  27 #include <linux/parser.h>
  28 #include <linux/magic.h>
  29 #include <linux/slab.h>
  30
  31 #define DEBUGFS_DEFAULT_MODE    0700
  32
  33 static struct vfsmount *debugfs_mount;
  34 static int debugfs_mount_count;
  35 static bool debugfs_registered;
  36
  37 static struct inode *debugfs_get_inode(struct super_block *sb, umode_t mode, dev_t dev,
  38                                        void *data, const struct file_operations *fops)
  39
  40 {
  41         struct inode *inode = new_inode(sb);
  42
  43         if (inode) {
  44                 inode->i_ino = get_next_ino();
  45                 inode->i_mode = mode;
  46                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  47                 switch (mode & S_IFMT) {
  48                 default:
  49                         init_special_inode(inode, mode, dev);
  50                         break;
  51                 case S_IFREG:
  52                         inode->i_fop = fops ? fops : &debugfs_file_operations;
  53                         inode->i_private = data;
  54                         break;
  55                 case S_IFLNK:
  56                         inode->i_op = &debugfs_link_operations;
  57                         inode->i_private = data;
  58                         break;
  59                 case S_IFDIR:
  60                         inode->i_op = &simple_dir_inode_operations;
  61                         inode->i_fop = &simple_dir_operations;
  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                          umode_t 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, umode_t mode)
  93 {
  94         int res;
  95
  96         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  97         res = debugfs_mknod(dir, dentry, mode, 0, NULL, NULL);
  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, umode_t mode,
 106                         void *data)
 107 {
 108         mode = (mode & S_IALLUGO) | S_IFLNK;
 109         return debugfs_mknod(dir, dentry, mode, 0, data, NULL);
 110 }
 111
 112 static int debugfs_create(struct inode *dir, struct dentry *dentry, umode_t 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 struct debugfs_mount_opts {
 130         kuid_t uid;
 131         kgid_t gid;
 132         umode_t mode;
 133 };
 134
 135 enum {
 136         Opt_uid,
 137         Opt_gid,
 138         Opt_mode,
 139         Opt_err
 140 };
 141
 142 static const match_table_t tokens = {
 143         {Opt_uid, "uid=%u"},
 144         {Opt_gid, "gid=%u"},
 145         {Opt_mode, "mode=%o"},
 146         {Opt_err, NULL}
 147 };
 148
 149 struct debugfs_fs_info {
 150         struct debugfs_mount_opts mount_opts;
 151 };
 152
 153 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
 154 {
 155         substring_t args[MAX_OPT_ARGS];
 156         int option;
 157         int token;
 158         kuid_t uid;
 159         kgid_t gid;
 160         char *p;
 161
 162         opts->mode = DEBUGFS_DEFAULT_MODE;
 163
 164         while ((p = strsep(&data, ",")) != NULL) {
 165                 if (!*p)
 166                         continue;
 167
 168                 token = match_token(p, tokens, args);
 169                 switch (token) {
 170                 case Opt_uid:
 171                         if (match_int(&args[0], &option))
 172                                 return -EINVAL;
 173                         uid = make_kuid(current_user_ns(), option);
 174                         if (!uid_valid(uid))
 175                                 return -EINVAL;
 176                         opts->uid = uid;
 177                         break;
 178                 case Opt_gid:
 179                         if (match_int(&args[0], &option))
 180                                 return -EINVAL;
 181                         gid = make_kgid(current_user_ns(), option);
 182                         if (!gid_valid(gid))
 183                                 return -EINVAL;
 184                         opts->gid = gid;
 185                         break;
 186                 case Opt_mode:
 187                         if (match_octal(&args[0], &option))
 188                                 return -EINVAL;
 189                         opts->mode = option & S_IALLUGO;
 190                         break;
 191                 /*
 192                  * We might like to report bad mount options here;
 193                  * but traditionally debugfs has ignored all mount options
 194                  */
 195                 }
 196         }
 197
 198         return 0;
 199 }
 200
 201 static int debugfs_apply_options(struct super_block *sb)
 202 {
 203         struct debugfs_fs_info *fsi = sb->s_fs_info;
 204         struct inode *inode = sb->s_root->d_inode;
 205         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 206
 207         inode->i_mode &= ~S_IALLUGO;
 208         inode->i_mode |= opts->mode;
 209
 210         inode->i_uid = opts->uid;
 211         inode->i_gid = opts->gid;
 212
 213         return 0;
 214 }
 215
 216 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
 217 {
 218         int err;
 219         struct debugfs_fs_info *fsi = sb->s_fs_info;
 220
 221         err = debugfs_parse_options(data, &fsi->mount_opts);
 222         if (err)
 223                 goto fail;
 224
 225         debugfs_apply_options(sb);
 226
 227 fail:
 228         return err;
 229 }
 230
 231 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
 232 {
 233         struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
 234         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 235
 236         if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
 237                 seq_printf(m, ",uid=%u",
 238                            from_kuid_munged(&init_user_ns, opts->uid));
 239         if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
 240                 seq_printf(m, ",gid=%u",
 241                            from_kgid_munged(&init_user_ns, opts->gid));
 242         if (opts->mode != DEBUGFS_DEFAULT_MODE)
 243                 seq_printf(m, ",mode=%o", opts->mode);
 244
 245         return 0;
 246 }
 247
 248 static const struct super_operations debugfs_super_operations = {
 249         .statfs         = simple_statfs,
 250         .remount_fs     = debugfs_remount,
 251         .show_options   = debugfs_show_options,
 252 };
 253
 254 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 255 {
 256         static struct tree_descr debug_files[] = {{""}};
 257         struct debugfs_fs_info *fsi;
 258         int err;
 259
 260         save_mount_options(sb, data);
 261
 262         fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
 263         sb->s_fs_info = fsi;
 264         if (!fsi) {
 265                 err = -ENOMEM;
 266                 goto fail;
 267         }
 268
 269         err = debugfs_parse_options(data, &fsi->mount_opts);
 270         if (err)
 271                 goto fail;
 272
 273         err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 274         if (err)
 275                 goto fail;
 276
 277         sb->s_op = &debugfs_super_operations;
 278
 279         debugfs_apply_options(sb);
 280
 281         return 0;
 282
 283 fail:
 284         kfree(fsi);
 285         sb->s_fs_info = NULL;
 286         return err;
 287 }
 288
 289 static struct dentry *debug_mount(struct file_system_type *fs_type,
 290                         int flags, const char *dev_name,
 291                         void *data)
 292 {
 293         return mount_single(fs_type, flags, data, debug_fill_super);
 294 }
 295
 296 static struct file_system_type debug_fs_type = {
 297         .owner =        THIS_MODULE,
 298         .name =         "debugfs",
 299         .mount =        debug_mount,
 300         .kill_sb =      kill_litter_super,
 301 };
 302
 303 static struct dentry *__create_file(const char *name, umode_t mode,
 304                                     struct dentry *parent, void *data,
 305                                     const struct file_operations *fops)
 306 {
 307         struct dentry *dentry = NULL;
 308         int error;
 309
 310         pr_debug("debugfs: creating file '%s'\n",name);
 311
 312         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 313                               &debugfs_mount_count);
 314         if (error)
 315                 goto exit;
 316
 317         /* If the parent is not specified, we create it in the root.
 318          * We need the root dentry to do this, which is in the super
 319          * block. A pointer to that is in the struct vfsmount that we
 320          * have around.
 321          */
 322         if (!parent)
 323                 parent = debugfs_mount->mnt_root;
 324
 325         mutex_lock(&parent->d_inode->i_mutex);
 326         dentry = lookup_one_len(name, parent, strlen(name));
 327         if (!IS_ERR(dentry)) {
 328                 switch (mode & S_IFMT) {
 329                 case S_IFDIR:
 330                         error = debugfs_mkdir(parent->d_inode, dentry, mode);
 331
 332                         break;
 333                 case S_IFLNK:
 334                         error = debugfs_link(parent->d_inode, dentry, mode,
 335                                              data);
 336                         break;
 337                 default:
 338                         error = debugfs_create(parent->d_inode, dentry, mode,
 339                                                data, fops);
 340                         break;
 341                 }
 342                 dput(dentry);
 343         } else
 344                 error = PTR_ERR(dentry);
 345         mutex_unlock(&parent->d_inode->i_mutex);
 346
 347         if (error) {
 348                 dentry = NULL;
 349                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 350         }
 351 exit:
 352         return dentry;
 353 }
 354
 355 /**
 356  * debugfs_create_file - create a file in the debugfs filesystem
 357  * @name: a pointer to a string containing the name of the file to create.
 358  * @mode: the permission that the file should have.
 359  * @parent: a pointer to the parent dentry for this file.  This should be a
 360  *          directory dentry if set.  If this paramater is NULL, then the
 361  *          file will be created in the root of the debugfs filesystem.
 362  * @data: a pointer to something that the caller will want to get to later
 363  *        on.  The inode.i_private pointer will point to this value on
 364  *        the open() call.
 365  * @fops: a pointer to a struct file_operations that should be used for
 366  *        this file.
 367  *
 368  * This is the basic "create a file" function for debugfs.  It allows for a
 369  * wide range of flexibility in creating a file, or a directory (if you want
 370  * to create a directory, the debugfs_create_dir() function is
 371  * recommended to be used instead.)
 372  *
 373  * This function will return a pointer to a dentry if it succeeds.  This
 374  * pointer must be passed to the debugfs_remove() function when the file is
 375  * to be removed (no automatic cleanup happens if your module is unloaded,
 376  * you are responsible here.)  If an error occurs, %NULL will be returned.
 377  *
 378  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 379  * returned.
 380  */
 381 struct dentry *debugfs_create_file(const char *name, umode_t mode,
 382                                    struct dentry *parent, void *data,
 383                                    const struct file_operations *fops)
 384 {
 385         switch (mode & S_IFMT) {
 386         case S_IFREG:
 387         case 0:
 388                 break;
 389         default:
 390                 BUG();
 391         }
 392
 393         return __create_file(name, mode, parent, data, fops);
 394 }
 395 EXPORT_SYMBOL_GPL(debugfs_create_file);
 396
 397 /**
 398  * debugfs_create_dir - create a directory in the debugfs filesystem
 399  * @name: a pointer to a string containing the name of the directory to
 400  *        create.
 401  * @parent: a pointer to the parent dentry for this file.  This should be a
 402  *          directory dentry if set.  If this paramater is NULL, then the
 403  *          directory will be created in the root of the debugfs filesystem.
 404  *
 405  * This function creates a directory in debugfs with the given name.
 406  *
 407  * This function will return a pointer to a dentry if it succeeds.  This
 408  * pointer must be passed to the debugfs_remove() function when the file is
 409  * to be removed (no automatic cleanup happens if your module is unloaded,
 410  * you are responsible here.)  If an error occurs, %NULL will be returned.
 411  *
 412  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 413  * returned.
 414  */
 415 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 416 {
 417         return __create_file(name, S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 418                                    parent, NULL, NULL);
 419 }
 420 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 421
 422 /**
 423  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 424  * @name: a pointer to a string containing the name of the symbolic link to
 425  *        create.
 426  * @parent: a pointer to the parent dentry for this symbolic link.  This
 427  *          should be a directory dentry if set.  If this paramater is NULL,
 428  *          then the symbolic link will be created in the root of the debugfs
 429  *          filesystem.
 430  * @target: a pointer to a string containing the path to the target of the
 431  *          symbolic link.
 432  *
 433  * This function creates a symbolic link with the given name in debugfs that
 434  * links to the given target path.
 435  *
 436  * This function will return a pointer to a dentry if it succeeds.  This
 437  * pointer must be passed to the debugfs_remove() function when the symbolic
 438  * link is to be removed (no automatic cleanup happens if your module is
 439  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 440  * returned.
 441  *
 442  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 443  * returned.
 444  */
 445 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 446                                       const char *target)
 447 {
 448         struct dentry *result;
 449         char *link;
 450
 451         link = kstrdup(target, GFP_KERNEL);
 452         if (!link)
 453                 return NULL;
 454
 455         result = __create_file(name, S_IFLNK | S_IRWXUGO, parent, link, NULL);
 456         if (!result)
 457                 kfree(link);
 458         return result;
 459 }
 460 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 461
 462 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
 463 {
 464         int ret = 0;
 465
 466         if (debugfs_positive(dentry)) {
 467                 if (dentry->d_inode) {
 468                         dget(dentry);
 469                         switch (dentry->d_inode->i_mode & S_IFMT) {
 470                         case S_IFDIR:
 471                                 ret = simple_rmdir(parent->d_inode, dentry);
 472                                 break;
 473                         case S_IFLNK:
 474                                 kfree(dentry->d_inode->i_private);
 475                                 /* fall through */
 476                         default:
 477                                 simple_unlink(parent->d_inode, dentry);
 478                                 break;
 479                         }
 480                         if (!ret)
 481                                 d_delete(dentry);
 482                         dput(dentry);
 483                 }
 484         }
 485         return ret;
 486 }
 487
 488 /**
 489  * debugfs_remove - removes a file or directory from the debugfs filesystem
 490  * @dentry: a pointer to a the dentry of the file or directory to be
 491  *          removed.
 492  *
 493  * This function removes a file or directory in debugfs that was previously
 494  * created with a call to another debugfs function (like
 495  * debugfs_create_file() or variants thereof.)
 496  *
 497  * This function is required to be called in order for the file to be
 498  * removed, no automatic cleanup of files will happen when a module is
 499  * removed, you are responsible here.
 500  */
 501 void debugfs_remove(struct dentry *dentry)
 502 {
 503         struct dentry *parent;
 504         int ret;
 505
 506         if (IS_ERR_OR_NULL(dentry))
 507                 return;
 508
 509         parent = dentry->d_parent;
 510         if (!parent || !parent->d_inode)
 511                 return;
 512
 513         mutex_lock(&parent->d_inode->i_mutex);
 514         ret = __debugfs_remove(dentry, parent);
 515         mutex_unlock(&parent->d_inode->i_mutex);
 516         if (!ret)
 517                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 518 }
 519 EXPORT_SYMBOL_GPL(debugfs_remove);
 520
 521 /**
 522  * debugfs_remove_recursive - recursively removes a directory
 523  * @dentry: a pointer to a the dentry of the directory to be removed.
 524  *
 525  * This function recursively removes a directory tree in debugfs that
 526  * was previously created with a call to another debugfs function
 527  * (like debugfs_create_file() or variants thereof.)
 528  *
 529  * This function is required to be called in order for the file to be
 530  * removed, no automatic cleanup of files will happen when a module is
 531  * removed, you are responsible here.
 532  */
 533 void debugfs_remove_recursive(struct dentry *dentry)
 534 {
 535         struct dentry *child;
 536         struct dentry *parent;
 537
 538         if (IS_ERR_OR_NULL(dentry))
 539                 return;
 540
 541         parent = dentry->d_parent;
 542         if (!parent || !parent->d_inode)
 543                 return;
 544
 545         parent = dentry;
 546         mutex_lock(&parent->d_inode->i_mutex);
 547
 548         while (1) {
 549                 /*
 550                  * When all dentries under "parent" has been removed,
 551                  * walk up the tree until we reach our starting point.
 552                  */
 553                 if (list_empty(&parent->d_subdirs)) {
 554                         mutex_unlock(&parent->d_inode->i_mutex);
 555                         if (parent == dentry)
 556                                 break;
 557                         parent = parent->d_parent;
 558                         mutex_lock(&parent->d_inode->i_mutex);
 559                 }
 560                 child = list_entry(parent->d_subdirs.next, struct dentry,
 561                                 d_u.d_child);
 562  next_sibling:
 563
 564                 /*
 565                  * If "child" isn't empty, walk down the tree and
 566                  * remove all its descendants first.
 567                  */
 568                 if (!list_empty(&child->d_subdirs)) {
 569                         mutex_unlock(&parent->d_inode->i_mutex);
 570                         parent = child;
 571                         mutex_lock(&parent->d_inode->i_mutex);
 572                         continue;
 573                 }
 574                 __debugfs_remove(child, parent);
 575                 if (parent->d_subdirs.next == &child->d_u.d_child) {
 576                         /*
 577                          * Try the next sibling.
 578                          */
 579                         if (child->d_u.d_child.next != &parent->d_subdirs) {
 580                                 child = list_entry(child->d_u.d_child.next,
 581                                                    struct dentry,
 582                                                    d_u.d_child);
 583                                 goto next_sibling;
 584                         }
 585
 586                         /*
 587                          * Avoid infinite loop if we fail to remove
 588                          * one dentry.
 589                          */
 590                         mutex_unlock(&parent->d_inode->i_mutex);
 591                         break;
 592                 }
 593                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 594         }
 595
 596         parent = dentry->d_parent;
 597         mutex_lock(&parent->d_inode->i_mutex);
 598         __debugfs_remove(dentry, parent);
 599         mutex_unlock(&parent->d_inode->i_mutex);
 600         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 601 }
 602 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
 603
 604 /**
 605  * debugfs_rename - rename a file/directory in the debugfs filesystem
 606  * @old_dir: a pointer to the parent dentry for the renamed object. This
 607  *          should be a directory dentry.
 608  * @old_dentry: dentry of an object to be renamed.
 609  * @new_dir: a pointer to the parent dentry where the object should be
 610  *          moved. This should be a directory dentry.
 611  * @new_name: a pointer to a string containing the target name.
 612  *
 613  * This function renames a file/directory in debugfs.  The target must not
 614  * exist for rename to succeed.
 615  *
 616  * This function will return a pointer to old_dentry (which is updated to
 617  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 618  * returned.
 619  *
 620  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 621  * returned.
 622  */
 623 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 624                 struct dentry *new_dir, const char *new_name)
 625 {
 626         int error;
 627         struct dentry *dentry = NULL, *trap;
 628         const char *old_name;
 629
 630         trap = lock_rename(new_dir, old_dir);
 631         /* Source or destination directories don't exist? */
 632         if (!old_dir->d_inode || !new_dir->d_inode)
 633                 goto exit;
 634         /* Source does not exist, cyclic rename, or mountpoint? */
 635         if (!old_dentry->d_inode || old_dentry == trap ||
 636             d_mountpoint(old_dentry))
 637                 goto exit;
 638         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 639         /* Lookup failed, cyclic rename or target exists? */
 640         if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
 641                 goto exit;
 642
 643         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
 644
 645         error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
 646                 dentry);
 647         if (error) {
 648                 fsnotify_oldname_free(old_name);
 649                 goto exit;
 650         }
 651         d_move(old_dentry, dentry);
 652         fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
 653                 S_ISDIR(old_dentry->d_inode->i_mode),
 654                 NULL, old_dentry);
 655         fsnotify_oldname_free(old_name);
 656         unlock_rename(new_dir, old_dir);
 657         dput(dentry);
 658         return old_dentry;
 659 exit:
 660         if (dentry && !IS_ERR(dentry))
 661                 dput(dentry);
 662         unlock_rename(new_dir, old_dir);
 663         return NULL;
 664 }
 665 EXPORT_SYMBOL_GPL(debugfs_rename);
 666
 667 /**
 668  * debugfs_initialized - Tells whether debugfs has been registered
 669  */
 670 bool debugfs_initialized(void)
 671 {
 672         return debugfs_registered;
 673 }
 674 EXPORT_SYMBOL_GPL(debugfs_initialized);
 675
 676
 677 static struct kobject *debug_kobj;
 678
 679 static int __init debugfs_init(void)
 680 {
 681         int retval;
 682
 683         debug_kobj = kobject_create_and_add("debug", kernel_kobj);
 684         if (!debug_kobj)
 685                 return -EINVAL;
 686
 687         retval = register_filesystem(&debug_fs_type);
 688         if (retval)
 689                 kobject_put(debug_kobj);
 690         else
 691                 debugfs_registered = true;
 692
 693         return retval;
 694 }
 695 core_initcall(debugfs_init);
 696