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 dentry *dentry, umode_t mode)
  93 {
  94         struct inode *dir = dentry->d_parent->d_inode;
  95         int res;
  96
  97         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  98         res = debugfs_mknod(dir, dentry, mode, 0, NULL, NULL);
  99         if (!res) {
 100                 inc_nlink(dir);
 101                 fsnotify_mkdir(dir, dentry);
 102         }
 103         return res;
 104 }
 105
 106 static int debugfs_link(struct dentry *dentry, umode_t mode,
 107                         void *data)
 108 {
 109         struct inode *dir = dentry->d_parent->d_inode;
 110         mode = (mode & S_IALLUGO) | S_IFLNK;
 111         return debugfs_mknod(dir, dentry, mode, 0, data, NULL);
 112 }
 113
 114 static int debugfs_create(struct dentry *dentry, umode_t mode,
 115                           void *data, const struct file_operations *fops)
 116 {
 117         struct inode *dir = dentry->d_parent->d_inode;
 118         int res;
 119
 120         mode = (mode & S_IALLUGO) | S_IFREG;
 121         res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
 122         if (!res)
 123                 fsnotify_create(dir, dentry);
 124         return res;
 125 }
 126
 127 static inline int debugfs_positive(struct dentry *dentry)
 128 {
 129         return dentry->d_inode && !d_unhashed(dentry);
 130 }
 131
 132 struct debugfs_mount_opts {
 133         kuid_t uid;
 134         kgid_t gid;
 135         umode_t mode;
 136 };
 137
 138 enum {
 139         Opt_uid,
 140         Opt_gid,
 141         Opt_mode,
 142         Opt_err
 143 };
 144
 145 static const match_table_t tokens = {
 146         {Opt_uid, "uid=%u"},
 147         {Opt_gid, "gid=%u"},
 148         {Opt_mode, "mode=%o"},
 149         {Opt_err, NULL}
 150 };
 151
 152 struct debugfs_fs_info {
 153         struct debugfs_mount_opts mount_opts;
 154 };
 155
 156 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
 157 {
 158         substring_t args[MAX_OPT_ARGS];
 159         int option;
 160         int token;
 161         kuid_t uid;
 162         kgid_t gid;
 163         char *p;
 164
 165         opts->mode = DEBUGFS_DEFAULT_MODE;
 166
 167         while ((p = strsep(&data, ",")) != NULL) {
 168                 if (!*p)
 169                         continue;
 170
 171                 token = match_token(p, tokens, args);
 172                 switch (token) {
 173                 case Opt_uid:
 174                         if (match_int(&args[0], &option))
 175                                 return -EINVAL;
 176                         uid = make_kuid(current_user_ns(), option);
 177                         if (!uid_valid(uid))
 178                                 return -EINVAL;
 179                         opts->uid = uid;
 180                         break;
 181                 case Opt_gid:
 182                         if (match_int(&args[0], &option))
 183                                 return -EINVAL;
 184                         gid = make_kgid(current_user_ns(), option);
 185                         if (!gid_valid(gid))
 186                                 return -EINVAL;
 187                         opts->gid = gid;
 188                         break;
 189                 case Opt_mode:
 190                         if (match_octal(&args[0], &option))
 191                                 return -EINVAL;
 192                         opts->mode = option & S_IALLUGO;
 193                         break;
 194                 /*
 195                  * We might like to report bad mount options here;
 196                  * but traditionally debugfs has ignored all mount options
 197                  */
 198                 }
 199         }
 200
 201         return 0;
 202 }
 203
 204 static int debugfs_apply_options(struct super_block *sb)
 205 {
 206         struct debugfs_fs_info *fsi = sb->s_fs_info;
 207         struct inode *inode = sb->s_root->d_inode;
 208         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 209
 210         inode->i_mode &= ~S_IALLUGO;
 211         inode->i_mode |= opts->mode;
 212
 213         inode->i_uid = opts->uid;
 214         inode->i_gid = opts->gid;
 215
 216         return 0;
 217 }
 218
 219 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
 220 {
 221         int err;
 222         struct debugfs_fs_info *fsi = sb->s_fs_info;
 223
 224         sync_filesystem(sb);
 225         err = debugfs_parse_options(data, &fsi->mount_opts);
 226         if (err)
 227                 goto fail;
 228
 229         debugfs_apply_options(sb);
 230
 231 fail:
 232         return err;
 233 }
 234
 235 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
 236 {
 237         struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
 238         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 239
 240         if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
 241                 seq_printf(m, ",uid=%u",
 242                            from_kuid_munged(&init_user_ns, opts->uid));
 243         if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
 244                 seq_printf(m, ",gid=%u",
 245                            from_kgid_munged(&init_user_ns, opts->gid));
 246         if (opts->mode != DEBUGFS_DEFAULT_MODE)
 247                 seq_printf(m, ",mode=%o", opts->mode);
 248
 249         return 0;
 250 }
 251
 252 static const struct super_operations debugfs_super_operations = {
 253         .statfs         = simple_statfs,
 254         .remount_fs     = debugfs_remount,
 255         .show_options   = debugfs_show_options,
 256 };
 257
 258 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 259 {
 260         static struct tree_descr debug_files[] = {{""}};
 261         struct debugfs_fs_info *fsi;
 262         int err;
 263
 264         save_mount_options(sb, data);
 265
 266         fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
 267         sb->s_fs_info = fsi;
 268         if (!fsi) {
 269                 err = -ENOMEM;
 270                 goto fail;
 271         }
 272
 273         err = debugfs_parse_options(data, &fsi->mount_opts);
 274         if (err)
 275                 goto fail;
 276
 277         err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 278         if (err)
 279                 goto fail;
 280
 281         sb->s_op = &debugfs_super_operations;
 282
 283         debugfs_apply_options(sb);
 284
 285         return 0;
 286
 287 fail:
 288         kfree(fsi);
 289         sb->s_fs_info = NULL;
 290         return err;
 291 }
 292
 293 static struct dentry *debug_mount(struct file_system_type *fs_type,
 294                         int flags, const char *dev_name,
 295                         void *data)
 296 {
 297         return mount_single(fs_type, flags, data, debug_fill_super);
 298 }
 299
 300 static struct file_system_type debug_fs_type = {
 301         .owner =        THIS_MODULE,
 302         .name =         "debugfs",
 303         .mount =        debug_mount,
 304         .kill_sb =      kill_litter_super,
 305 };
 306 MODULE_ALIAS_FS("debugfs");
 307
 308 static struct dentry *start_creating(const char *name, struct dentry *parent)
 309 {
 310         struct dentry *dentry;
 311         int error;
 312
 313         pr_debug("debugfs: creating file '%s'\n",name);
 314
 315         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 316                               &debugfs_mount_count);
 317         if (error)
 318                 return ERR_PTR(error);
 319
 320         /* If the parent is not specified, we create it in the root.
 321          * We need the root dentry to do this, which is in the super
 322          * block. A pointer to that is in the struct vfsmount that we
 323          * have around.
 324          */
 325         if (!parent)
 326                 parent = debugfs_mount->mnt_root;
 327
 328         mutex_lock(&parent->d_inode->i_mutex);
 329         dentry = lookup_one_len(name, parent, strlen(name));
 330         if (!IS_ERR(dentry) && dentry->d_inode) {
 331                 dput(dentry);
 332                 dentry = ERR_PTR(-EEXIST);
 333         }
 334         if (IS_ERR(dentry))
 335                 mutex_unlock(&parent->d_inode->i_mutex);
 336         return dentry;
 337 }
 338
 339 static struct dentry *end_creating(struct dentry *dentry, int error)
 340 {
 341         mutex_unlock(&dentry->d_parent->d_inode->i_mutex);
 342         dput(dentry);
 343
 344         if (error) {
 345                 dentry = NULL;
 346                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 347         }
 348         return dentry;
 349 }
 350
 351 static struct dentry *__create_file(const char *name, umode_t mode,
 352                                     struct dentry *parent, void *data,
 353                                     const struct file_operations *fops)
 354 {
 355         struct dentry *dentry = start_creating(name, parent);
 356         int error;
 357
 358         if (IS_ERR(dentry))
 359                 return NULL;
 360
 361         switch (mode & S_IFMT) {
 362         case S_IFDIR:
 363                 error = debugfs_mkdir(dentry, mode);
 364                 break;
 365         case S_IFLNK:
 366                 error = debugfs_link(dentry, mode, data);
 367                 break;
 368         default:
 369                 error = debugfs_create(dentry, mode, data, fops);
 370                 break;
 371         }
 372         return end_creating(dentry, error);
 373 }
 374
 375 /**
 376  * debugfs_create_file - create a file in the debugfs filesystem
 377  * @name: a pointer to a string containing the name of the file to create.
 378  * @mode: the permission that the file should have.
 379  * @parent: a pointer to the parent dentry for this file.  This should be a
 380  *          directory dentry if set.  If this parameter is NULL, then the
 381  *          file will be created in the root of the debugfs filesystem.
 382  * @data: a pointer to something that the caller will want to get to later
 383  *        on.  The inode.i_private pointer will point to this value on
 384  *        the open() call.
 385  * @fops: a pointer to a struct file_operations that should be used for
 386  *        this file.
 387  *
 388  * This is the basic "create a file" function for debugfs.  It allows for a
 389  * wide range of flexibility in creating a file, or a directory (if you want
 390  * to create a directory, the debugfs_create_dir() function is
 391  * recommended to be used instead.)
 392  *
 393  * This function will return a pointer to a dentry if it succeeds.  This
 394  * pointer must be passed to the debugfs_remove() function when the file is
 395  * to be removed (no automatic cleanup happens if your module is unloaded,
 396  * you are responsible here.)  If an error occurs, %NULL will be returned.
 397  *
 398  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 399  * returned.
 400  */
 401 struct dentry *debugfs_create_file(const char *name, umode_t mode,
 402                                    struct dentry *parent, void *data,
 403                                    const struct file_operations *fops)
 404 {
 405         switch (mode & S_IFMT) {
 406         case S_IFREG:
 407         case 0:
 408                 break;
 409         default:
 410                 BUG();
 411         }
 412
 413         return __create_file(name, mode, parent, data, fops);
 414 }
 415 EXPORT_SYMBOL_GPL(debugfs_create_file);
 416
 417 /**
 418  * debugfs_create_dir - create a directory in the debugfs filesystem
 419  * @name: a pointer to a string containing the name of the directory to
 420  *        create.
 421  * @parent: a pointer to the parent dentry for this file.  This should be a
 422  *          directory dentry if set.  If this parameter is NULL, then the
 423  *          directory will be created in the root of the debugfs filesystem.
 424  *
 425  * This function creates a directory in debugfs with the given name.
 426  *
 427  * This function will return a pointer to a dentry if it succeeds.  This
 428  * pointer must be passed to the debugfs_remove() function when the file is
 429  * to be removed (no automatic cleanup happens if your module is unloaded,
 430  * you are responsible here.)  If an error occurs, %NULL will be returned.
 431  *
 432  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 433  * returned.
 434  */
 435 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 436 {
 437         return __create_file(name, S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 438                                    parent, NULL, NULL);
 439 }
 440 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 441
 442 /**
 443  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 444  * @name: a pointer to a string containing the name of the symbolic link to
 445  *        create.
 446  * @parent: a pointer to the parent dentry for this symbolic link.  This
 447  *          should be a directory dentry if set.  If this parameter is NULL,
 448  *          then the symbolic link will be created in the root of the debugfs
 449  *          filesystem.
 450  * @target: a pointer to a string containing the path to the target of the
 451  *          symbolic link.
 452  *
 453  * This function creates a symbolic link with the given name in debugfs that
 454  * links to the given target path.
 455  *
 456  * This function will return a pointer to a dentry if it succeeds.  This
 457  * pointer must be passed to the debugfs_remove() function when the symbolic
 458  * link is to be removed (no automatic cleanup happens if your module is
 459  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 460  * returned.
 461  *
 462  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 463  * returned.
 464  */
 465 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 466                                       const char *target)
 467 {
 468         struct dentry *result;
 469         char *link;
 470
 471         link = kstrdup(target, GFP_KERNEL);
 472         if (!link)
 473                 return NULL;
 474
 475         result = __create_file(name, S_IFLNK | S_IRWXUGO, parent, link, NULL);
 476         if (!result)
 477                 kfree(link);
 478         return result;
 479 }
 480 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 481
 482 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
 483 {
 484         int ret = 0;
 485
 486         if (debugfs_positive(dentry)) {
 487                 if (dentry->d_inode) {
 488                         dget(dentry);
 489                         switch (dentry->d_inode->i_mode & S_IFMT) {
 490                         case S_IFDIR:
 491                                 ret = simple_rmdir(parent->d_inode, dentry);
 492                                 break;
 493                         case S_IFLNK:
 494                                 kfree(dentry->d_inode->i_private);
 495                                 /* fall through */
 496                         default:
 497                                 simple_unlink(parent->d_inode, dentry);
 498                                 break;
 499                         }
 500                         if (!ret)
 501                                 d_delete(dentry);
 502                         dput(dentry);
 503                 }
 504         }
 505         return ret;
 506 }
 507
 508 /**
 509  * debugfs_remove - removes a file or directory from the debugfs filesystem
 510  * @dentry: a pointer to a the dentry of the file or directory to be
 511  *          removed.
 512  *
 513  * This function removes a file or directory in debugfs that was previously
 514  * created with a call to another debugfs function (like
 515  * debugfs_create_file() or variants thereof.)
 516  *
 517  * This function is required to be called in order for the file to be
 518  * removed, no automatic cleanup of files will happen when a module is
 519  * removed, you are responsible here.
 520  */
 521 void debugfs_remove(struct dentry *dentry)
 522 {
 523         struct dentry *parent;
 524         int ret;
 525
 526         if (IS_ERR_OR_NULL(dentry))
 527                 return;
 528
 529         parent = dentry->d_parent;
 530         if (!parent || !parent->d_inode)
 531                 return;
 532
 533         mutex_lock(&parent->d_inode->i_mutex);
 534         ret = __debugfs_remove(dentry, parent);
 535         mutex_unlock(&parent->d_inode->i_mutex);
 536         if (!ret)
 537                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 538 }
 539 EXPORT_SYMBOL_GPL(debugfs_remove);
 540
 541 /**
 542  * debugfs_remove_recursive - recursively removes a directory
 543  * @dentry: a pointer to a the dentry of the directory to be removed.
 544  *
 545  * This function recursively removes a directory tree in debugfs that
 546  * was previously created with a call to another debugfs function
 547  * (like debugfs_create_file() or variants thereof.)
 548  *
 549  * This function is required to be called in order for the file to be
 550  * removed, no automatic cleanup of files will happen when a module is
 551  * removed, you are responsible here.
 552  */
 553 void debugfs_remove_recursive(struct dentry *dentry)
 554 {
 555         struct dentry *child, *parent;
 556
 557         if (IS_ERR_OR_NULL(dentry))
 558                 return;
 559
 560         parent = dentry->d_parent;
 561         if (!parent || !parent->d_inode)
 562                 return;
 563
 564         parent = dentry;
 565  down:
 566         mutex_lock(&parent->d_inode->i_mutex);
 567  loop:
 568         /*
 569          * The parent->d_subdirs is protected by the d_lock. Outside that
 570          * lock, the child can be unlinked and set to be freed which can
 571          * use the d_u.d_child as the rcu head and corrupt this list.
 572          */
 573         spin_lock(&parent->d_lock);
 574         list_for_each_entry(child, &parent->d_subdirs, d_child) {
 575                 if (!debugfs_positive(child))
 576                         continue;
 577
 578                 /* perhaps simple_empty(child) makes more sense */
 579                 if (!list_empty(&child->d_subdirs)) {
 580                         spin_unlock(&parent->d_lock);
 581                         mutex_unlock(&parent->d_inode->i_mutex);
 582                         parent = child;
 583                         goto down;
 584                 }
 585
 586                 spin_unlock(&parent->d_lock);
 587
 588                 if (!__debugfs_remove(child, parent))
 589                         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 590
 591                 /*
 592                  * The parent->d_lock protects agaist child from unlinking
 593                  * from d_subdirs. When releasing the parent->d_lock we can
 594                  * no longer trust that the next pointer is valid.
 595                  * Restart the loop. We'll skip this one with the
 596                  * debugfs_positive() check.
 597                  */
 598                 goto loop;
 599         }
 600         spin_unlock(&parent->d_lock);
 601
 602         mutex_unlock(&parent->d_inode->i_mutex);
 603         child = parent;
 604         parent = parent->d_parent;
 605         mutex_lock(&parent->d_inode->i_mutex);
 606
 607         if (child != dentry)
 608                 /* go up */
 609                 goto loop;
 610
 611         if (!__debugfs_remove(child, parent))
 612                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 613         mutex_unlock(&parent->d_inode->i_mutex);
 614 }
 615 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
 616
 617 /**
 618  * debugfs_rename - rename a file/directory in the debugfs filesystem
 619  * @old_dir: a pointer to the parent dentry for the renamed object. This
 620  *          should be a directory dentry.
 621  * @old_dentry: dentry of an object to be renamed.
 622  * @new_dir: a pointer to the parent dentry where the object should be
 623  *          moved. This should be a directory dentry.
 624  * @new_name: a pointer to a string containing the target name.
 625  *
 626  * This function renames a file/directory in debugfs.  The target must not
 627  * exist for rename to succeed.
 628  *
 629  * This function will return a pointer to old_dentry (which is updated to
 630  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 631  * returned.
 632  *
 633  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 634  * returned.
 635  */
 636 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 637                 struct dentry *new_dir, const char *new_name)
 638 {
 639         int error;
 640         struct dentry *dentry = NULL, *trap;
 641         const char *old_name;
 642
 643         trap = lock_rename(new_dir, old_dir);
 644         /* Source or destination directories don't exist? */
 645         if (!old_dir->d_inode || !new_dir->d_inode)
 646                 goto exit;
 647         /* Source does not exist, cyclic rename, or mountpoint? */
 648         if (!old_dentry->d_inode || old_dentry == trap ||
 649             d_mountpoint(old_dentry))
 650                 goto exit;
 651         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 652         /* Lookup failed, cyclic rename or target exists? */
 653         if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
 654                 goto exit;
 655
 656         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
 657
 658         error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
 659                 dentry);
 660         if (error) {
 661                 fsnotify_oldname_free(old_name);
 662                 goto exit;
 663         }
 664         d_move(old_dentry, dentry);
 665         fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
 666                 S_ISDIR(old_dentry->d_inode->i_mode),
 667                 NULL, old_dentry);
 668         fsnotify_oldname_free(old_name);
 669         unlock_rename(new_dir, old_dir);
 670         dput(dentry);
 671         return old_dentry;
 672 exit:
 673         if (dentry && !IS_ERR(dentry))
 674                 dput(dentry);
 675         unlock_rename(new_dir, old_dir);
 676         return NULL;
 677 }
 678 EXPORT_SYMBOL_GPL(debugfs_rename);
 679
 680 /**
 681  * debugfs_initialized - Tells whether debugfs has been registered
 682  */
 683 bool debugfs_initialized(void)
 684 {
 685         return debugfs_registered;
 686 }
 687 EXPORT_SYMBOL_GPL(debugfs_initialized);
 688
 689
 690 static struct kobject *debug_kobj;
 691
 692 static int __init debugfs_init(void)
 693 {
 694         int retval;
 695
 696         debug_kobj = kobject_create_and_add("debug", kernel_kobj);
 697         if (!debug_kobj)
 698                 return -EINVAL;
 699
 700         retval = register_filesystem(&debug_fs_type);
 701         if (retval)
 702                 kobject_put(debug_kobj);
 703         else
 704                 debugfs_registered = true;
 705
 706         return retval;
 707 }
 708 core_initcall(debugfs_init);
 709