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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * inode.c - part of debugfs, a tiny little debug file system
4 *
5 * Copyright (C) 2004,2019 Greg Kroah-Hartman <greg@kroah.com>
6 * Copyright (C) 2004 IBM Inc.
7 * Copyright (C) 2019 Linux Foundation <gregkh@linuxfoundation.org>
8 *
9 * debugfs is for people to use instead of /proc or /sys.
10 * See ./Documentation/core-api/kernel-api.rst for more details.
11 */
12
13#define pr_fmt(fmt) "debugfs: " fmt
14
15#include <linux/module.h>
16#include <linux/fs.h>
17#include <linux/mount.h>
18#include <linux/pagemap.h>
19#include <linux/init.h>
20#include <linux/kobject.h>
21#include <linux/namei.h>
22#include <linux/debugfs.h>
23#include <linux/fsnotify.h>
24#include <linux/string.h>
25#include <linux/seq_file.h>
26#include <linux/parser.h>
27#include <linux/magic.h>
28#include <linux/slab.h>
29#include <linux/security.h>
30
31#include "internal.h"
32
33#define DEBUGFS_DEFAULT_MODE 0700
34
35static struct vfsmount *debugfs_mount;
36static int debugfs_mount_count;
37static bool debugfs_registered;
38static unsigned int debugfs_allow __ro_after_init = DEFAULT_DEBUGFS_ALLOW_BITS;
39
40/*
41 * Don't allow access attributes to be changed whilst the kernel is locked down
42 * so that we can use the file mode as part of a heuristic to determine whether
43 * to lock down individual files.
44 */
45static int debugfs_setattr(struct user_namespace *mnt_userns,
46 struct dentry *dentry, struct iattr *ia)
47{
48 int ret;
49
50 if (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) {
51 ret = security_locked_down(LOCKDOWN_DEBUGFS);
52 if (ret)
53 return ret;
54 }
55 return simple_setattr(&init_user_ns, dentry, ia);
56}
57
58static const struct inode_operations debugfs_file_inode_operations = {
59 .setattr = debugfs_setattr,
60};
61static const struct inode_operations debugfs_dir_inode_operations = {
62 .lookup = simple_lookup,
63 .setattr = debugfs_setattr,
64};
65static const struct inode_operations debugfs_symlink_inode_operations = {
66 .get_link = simple_get_link,
67 .setattr = debugfs_setattr,
68};
69
70static struct inode *debugfs_get_inode(struct super_block *sb)
71{
72 struct inode *inode = new_inode(sb);
73 if (inode) {
74 inode->i_ino = get_next_ino();
75 inode->i_atime = inode->i_mtime =
76 inode->i_ctime = current_time(inode);
77 }
78 return inode;
79}
80
81struct debugfs_mount_opts {
82 kuid_t uid;
83 kgid_t gid;
84 umode_t mode;
85 /* Opt_* bitfield. */
86 unsigned int opts;
87};
88
89enum {
90 Opt_uid,
91 Opt_gid,
92 Opt_mode,
93 Opt_err
94};
95
96static const match_table_t tokens = {
97 {Opt_uid, "uid=%u"},
98 {Opt_gid, "gid=%u"},
99 {Opt_mode, "mode=%o"},
100 {Opt_err, NULL}
101};
102
103struct debugfs_fs_info {
104 struct debugfs_mount_opts mount_opts;
105};
106
107static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
108{
109 substring_t args[MAX_OPT_ARGS];
110 int option;
111 int token;
112 kuid_t uid;
113 kgid_t gid;
114 char *p;
115
116 opts->opts = 0;
117 opts->mode = DEBUGFS_DEFAULT_MODE;
118
119 while ((p = strsep(&data, ",")) != NULL) {
120 if (!*p)
121 continue;
122
123 token = match_token(p, tokens, args);
124 switch (token) {
125 case Opt_uid:
126 if (match_int(&args[0], &option))
127 return -EINVAL;
128 uid = make_kuid(current_user_ns(), option);
129 if (!uid_valid(uid))
130 return -EINVAL;
131 opts->uid = uid;
132 break;
133 case Opt_gid:
134 if (match_int(&args[0], &option))
135 return -EINVAL;
136 gid = make_kgid(current_user_ns(), option);
137 if (!gid_valid(gid))
138 return -EINVAL;
139 opts->gid = gid;
140 break;
141 case Opt_mode:
142 if (match_octal(&args[0], &option))
143 return -EINVAL;
144 opts->mode = option & S_IALLUGO;
145 break;
146 /*
147 * We might like to report bad mount options here;
148 * but traditionally debugfs has ignored all mount options
149 */
150 }
151
152 opts->opts |= BIT(token);
153 }
154
155 return 0;
156}
157
158static void _debugfs_apply_options(struct super_block *sb, bool remount)
159{
160 struct debugfs_fs_info *fsi = sb->s_fs_info;
161 struct inode *inode = d_inode(sb->s_root);
162 struct debugfs_mount_opts *opts = &fsi->mount_opts;
163
164 /*
165 * On remount, only reset mode/uid/gid if they were provided as mount
166 * options.
167 */
168
169 if (!remount || opts->opts & BIT(Opt_mode)) {
170 inode->i_mode &= ~S_IALLUGO;
171 inode->i_mode |= opts->mode;
172 }
173
174 if (!remount || opts->opts & BIT(Opt_uid))
175 inode->i_uid = opts->uid;
176
177 if (!remount || opts->opts & BIT(Opt_gid))
178 inode->i_gid = opts->gid;
179}
180
181static void debugfs_apply_options(struct super_block *sb)
182{
183 _debugfs_apply_options(sb, false);
184}
185
186static void debugfs_apply_options_remount(struct super_block *sb)
187{
188 _debugfs_apply_options(sb, true);
189}
190
191static int debugfs_remount(struct super_block *sb, int *flags, char *data)
192{
193 int err;
194 struct debugfs_fs_info *fsi = sb->s_fs_info;
195
196 sync_filesystem(sb);
197 err = debugfs_parse_options(data, &fsi->mount_opts);
198 if (err)
199 goto fail;
200
201 debugfs_apply_options_remount(sb);
202
203fail:
204 return err;
205}
206
207static int debugfs_show_options(struct seq_file *m, struct dentry *root)
208{
209 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
210 struct debugfs_mount_opts *opts = &fsi->mount_opts;
211
212 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
213 seq_printf(m, ",uid=%u",
214 from_kuid_munged(&init_user_ns, opts->uid));
215 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
216 seq_printf(m, ",gid=%u",
217 from_kgid_munged(&init_user_ns, opts->gid));
218 if (opts->mode != DEBUGFS_DEFAULT_MODE)
219 seq_printf(m, ",mode=%o", opts->mode);
220
221 return 0;
222}
223
224static void debugfs_free_inode(struct inode *inode)
225{
226 if (S_ISLNK(inode->i_mode))
227 kfree(inode->i_link);
228 free_inode_nonrcu(inode);
229}
230
231static const struct super_operations debugfs_super_operations = {
232 .statfs = simple_statfs,
233 .remount_fs = debugfs_remount,
234 .show_options = debugfs_show_options,
235 .free_inode = debugfs_free_inode,
236};
237
238static void debugfs_release_dentry(struct dentry *dentry)
239{
240 void *fsd = dentry->d_fsdata;
241
242 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
243 kfree(dentry->d_fsdata);
244}
245
246static struct vfsmount *debugfs_automount(struct path *path)
247{
248 debugfs_automount_t f;
249 f = (debugfs_automount_t)path->dentry->d_fsdata;
250 return f(path->dentry, d_inode(path->dentry)->i_private);
251}
252
253static const struct dentry_operations debugfs_dops = {
254 .d_delete = always_delete_dentry,
255 .d_release = debugfs_release_dentry,
256 .d_automount = debugfs_automount,
257};
258
259static int debug_fill_super(struct super_block *sb, void *data, int silent)
260{
261 static const struct tree_descr debug_files[] = {{""}};
262 struct debugfs_fs_info *fsi;
263 int err;
264
265 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
266 sb->s_fs_info = fsi;
267 if (!fsi) {
268 err = -ENOMEM;
269 goto fail;
270 }
271
272 err = debugfs_parse_options(data, &fsi->mount_opts);
273 if (err)
274 goto fail;
275
276 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
277 if (err)
278 goto fail;
279
280 sb->s_op = &debugfs_super_operations;
281 sb->s_d_op = &debugfs_dops;
282
283 debugfs_apply_options(sb);
284
285 return 0;
286
287fail:
288 kfree(fsi);
289 sb->s_fs_info = NULL;
290 return err;
291}
292
293static struct dentry *debug_mount(struct file_system_type *fs_type,
294 int flags, const char *dev_name,
295 void *data)
296{
297 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
298 return ERR_PTR(-EPERM);
299
300 return mount_single(fs_type, flags, data, debug_fill_super);
301}
302
303static struct file_system_type debug_fs_type = {
304 .owner = THIS_MODULE,
305 .name = "debugfs",
306 .mount = debug_mount,
307 .kill_sb = kill_litter_super,
308};
309MODULE_ALIAS_FS("debugfs");
310
311/**
312 * debugfs_lookup() - look up an existing debugfs file
313 * @name: a pointer to a string containing the name of the file to look up.
314 * @parent: a pointer to the parent dentry of the file.
315 *
316 * This function will return a pointer to a dentry if it succeeds. If the file
317 * doesn't exist or an error occurs, %NULL will be returned. The returned
318 * dentry must be passed to dput() when it is no longer needed.
319 *
320 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
321 * returned.
322 */
323struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
324{
325 struct dentry *dentry;
326
327 if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
328 return NULL;
329
330 if (!parent)
331 parent = debugfs_mount->mnt_root;
332
333 dentry = lookup_positive_unlocked(name, parent, strlen(name));
334 if (IS_ERR(dentry))
335 return NULL;
336 return dentry;
337}
338EXPORT_SYMBOL_GPL(debugfs_lookup);
339
340static struct dentry *start_creating(const char *name, struct dentry *parent)
341{
342 struct dentry *dentry;
343 int error;
344
345 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
346 return ERR_PTR(-EPERM);
347
348 if (!debugfs_initialized())
349 return ERR_PTR(-ENOENT);
350
351 pr_debug("creating file '%s'\n", name);
352
353 if (IS_ERR(parent))
354 return parent;
355
356 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
357 &debugfs_mount_count);
358 if (error) {
359 pr_err("Unable to pin filesystem for file '%s'\n", name);
360 return ERR_PTR(error);
361 }
362
363 /* If the parent is not specified, we create it in the root.
364 * We need the root dentry to do this, which is in the super
365 * block. A pointer to that is in the struct vfsmount that we
366 * have around.
367 */
368 if (!parent)
369 parent = debugfs_mount->mnt_root;
370
371 inode_lock(d_inode(parent));
372 if (unlikely(IS_DEADDIR(d_inode(parent))))
373 dentry = ERR_PTR(-ENOENT);
374 else
375 dentry = lookup_one_len(name, parent, strlen(name));
376 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
377 if (d_is_dir(dentry))
378 pr_err("Directory '%s' with parent '%s' already present!\n",
379 name, parent->d_name.name);
380 else
381 pr_err("File '%s' in directory '%s' already present!\n",
382 name, parent->d_name.name);
383 dput(dentry);
384 dentry = ERR_PTR(-EEXIST);
385 }
386
387 if (IS_ERR(dentry)) {
388 inode_unlock(d_inode(parent));
389 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
390 }
391
392 return dentry;
393}
394
395static struct dentry *failed_creating(struct dentry *dentry)
396{
397 inode_unlock(d_inode(dentry->d_parent));
398 dput(dentry);
399 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
400 return ERR_PTR(-ENOMEM);
401}
402
403static struct dentry *end_creating(struct dentry *dentry)
404{
405 inode_unlock(d_inode(dentry->d_parent));
406 return dentry;
407}
408
409static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
410 struct dentry *parent, void *data,
411 const struct file_operations *proxy_fops,
412 const struct file_operations *real_fops)
413{
414 struct dentry *dentry;
415 struct inode *inode;
416
417 if (!(mode & S_IFMT))
418 mode |= S_IFREG;
419 BUG_ON(!S_ISREG(mode));
420 dentry = start_creating(name, parent);
421
422 if (IS_ERR(dentry))
423 return dentry;
424
425 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
426 failed_creating(dentry);
427 return ERR_PTR(-EPERM);
428 }
429
430 inode = debugfs_get_inode(dentry->d_sb);
431 if (unlikely(!inode)) {
432 pr_err("out of free dentries, can not create file '%s'\n",
433 name);
434 return failed_creating(dentry);
435 }
436
437 inode->i_mode = mode;
438 inode->i_private = data;
439
440 inode->i_op = &debugfs_file_inode_operations;
441 inode->i_fop = proxy_fops;
442 dentry->d_fsdata = (void *)((unsigned long)real_fops |
443 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
444
445 d_instantiate(dentry, inode);
446 fsnotify_create(d_inode(dentry->d_parent), dentry);
447 return end_creating(dentry);
448}
449
450/**
451 * debugfs_create_file - create a file in the debugfs filesystem
452 * @name: a pointer to a string containing the name of the file to create.
453 * @mode: the permission that the file should have.
454 * @parent: a pointer to the parent dentry for this file. This should be a
455 * directory dentry if set. If this parameter is NULL, then the
456 * file will be created in the root of the debugfs filesystem.
457 * @data: a pointer to something that the caller will want to get to later
458 * on. The inode.i_private pointer will point to this value on
459 * the open() call.
460 * @fops: a pointer to a struct file_operations that should be used for
461 * this file.
462 *
463 * This is the basic "create a file" function for debugfs. It allows for a
464 * wide range of flexibility in creating a file, or a directory (if you want
465 * to create a directory, the debugfs_create_dir() function is
466 * recommended to be used instead.)
467 *
468 * This function will return a pointer to a dentry if it succeeds. This
469 * pointer must be passed to the debugfs_remove() function when the file is
470 * to be removed (no automatic cleanup happens if your module is unloaded,
471 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
472 * returned.
473 *
474 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
475 * returned.
476 *
477 * NOTE: it's expected that most callers should _ignore_ the errors returned
478 * by this function. Other debugfs functions handle the fact that the "dentry"
479 * passed to them could be an error and they don't crash in that case.
480 * Drivers should generally work fine even if debugfs fails to init anyway.
481 */
482struct dentry *debugfs_create_file(const char *name, umode_t mode,
483 struct dentry *parent, void *data,
484 const struct file_operations *fops)
485{
486
487 return __debugfs_create_file(name, mode, parent, data,
488 fops ? &debugfs_full_proxy_file_operations :
489 &debugfs_noop_file_operations,
490 fops);
491}
492EXPORT_SYMBOL_GPL(debugfs_create_file);
493
494/**
495 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
496 * @name: a pointer to a string containing the name of the file to create.
497 * @mode: the permission that the file should have.
498 * @parent: a pointer to the parent dentry for this file. This should be a
499 * directory dentry if set. If this parameter is NULL, then the
500 * file will be created in the root of the debugfs filesystem.
501 * @data: a pointer to something that the caller will want to get to later
502 * on. The inode.i_private pointer will point to this value on
503 * the open() call.
504 * @fops: a pointer to a struct file_operations that should be used for
505 * this file.
506 *
507 * debugfs_create_file_unsafe() is completely analogous to
508 * debugfs_create_file(), the only difference being that the fops
509 * handed it will not get protected against file removals by the
510 * debugfs core.
511 *
512 * It is your responsibility to protect your struct file_operation
513 * methods against file removals by means of debugfs_file_get()
514 * and debugfs_file_put(). ->open() is still protected by
515 * debugfs though.
516 *
517 * Any struct file_operations defined by means of
518 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
519 * thus, may be used here.
520 */
521struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
522 struct dentry *parent, void *data,
523 const struct file_operations *fops)
524{
525
526 return __debugfs_create_file(name, mode, parent, data,
527 fops ? &debugfs_open_proxy_file_operations :
528 &debugfs_noop_file_operations,
529 fops);
530}
531EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
532
533/**
534 * debugfs_create_file_size - create a file in the debugfs filesystem
535 * @name: a pointer to a string containing the name of the file to create.
536 * @mode: the permission that the file should have.
537 * @parent: a pointer to the parent dentry for this file. This should be a
538 * directory dentry if set. If this parameter is NULL, then the
539 * file will be created in the root of the debugfs filesystem.
540 * @data: a pointer to something that the caller will want to get to later
541 * on. The inode.i_private pointer will point to this value on
542 * the open() call.
543 * @fops: a pointer to a struct file_operations that should be used for
544 * this file.
545 * @file_size: initial file size
546 *
547 * This is the basic "create a file" function for debugfs. It allows for a
548 * wide range of flexibility in creating a file, or a directory (if you want
549 * to create a directory, the debugfs_create_dir() function is
550 * recommended to be used instead.)
551 */
552void debugfs_create_file_size(const char *name, umode_t mode,
553 struct dentry *parent, void *data,
554 const struct file_operations *fops,
555 loff_t file_size)
556{
557 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
558
559 if (!IS_ERR(de))
560 d_inode(de)->i_size = file_size;
561}
562EXPORT_SYMBOL_GPL(debugfs_create_file_size);
563
564/**
565 * debugfs_create_dir - create a directory in the debugfs filesystem
566 * @name: a pointer to a string containing the name of the directory to
567 * create.
568 * @parent: a pointer to the parent dentry for this file. This should be a
569 * directory dentry if set. If this parameter is NULL, then the
570 * directory will be created in the root of the debugfs filesystem.
571 *
572 * This function creates a directory in debugfs with the given name.
573 *
574 * This function will return a pointer to a dentry if it succeeds. This
575 * pointer must be passed to the debugfs_remove() function when the file is
576 * to be removed (no automatic cleanup happens if your module is unloaded,
577 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
578 * returned.
579 *
580 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
581 * returned.
582 *
583 * NOTE: it's expected that most callers should _ignore_ the errors returned
584 * by this function. Other debugfs functions handle the fact that the "dentry"
585 * passed to them could be an error and they don't crash in that case.
586 * Drivers should generally work fine even if debugfs fails to init anyway.
587 */
588struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
589{
590 struct dentry *dentry = start_creating(name, parent);
591 struct inode *inode;
592
593 if (IS_ERR(dentry))
594 return dentry;
595
596 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
597 failed_creating(dentry);
598 return ERR_PTR(-EPERM);
599 }
600
601 inode = debugfs_get_inode(dentry->d_sb);
602 if (unlikely(!inode)) {
603 pr_err("out of free dentries, can not create directory '%s'\n",
604 name);
605 return failed_creating(dentry);
606 }
607
608 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
609 inode->i_op = &debugfs_dir_inode_operations;
610 inode->i_fop = &simple_dir_operations;
611
612 /* directory inodes start off with i_nlink == 2 (for "." entry) */
613 inc_nlink(inode);
614 d_instantiate(dentry, inode);
615 inc_nlink(d_inode(dentry->d_parent));
616 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
617 return end_creating(dentry);
618}
619EXPORT_SYMBOL_GPL(debugfs_create_dir);
620
621/**
622 * debugfs_create_automount - create automount point in the debugfs filesystem
623 * @name: a pointer to a string containing the name of the file to create.
624 * @parent: a pointer to the parent dentry for this file. This should be a
625 * directory dentry if set. If this parameter is NULL, then the
626 * file will be created in the root of the debugfs filesystem.
627 * @f: function to be called when pathname resolution steps on that one.
628 * @data: opaque argument to pass to f().
629 *
630 * @f should return what ->d_automount() would.
631 */
632struct dentry *debugfs_create_automount(const char *name,
633 struct dentry *parent,
634 debugfs_automount_t f,
635 void *data)
636{
637 struct dentry *dentry = start_creating(name, parent);
638 struct inode *inode;
639
640 if (IS_ERR(dentry))
641 return dentry;
642
643 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
644 failed_creating(dentry);
645 return ERR_PTR(-EPERM);
646 }
647
648 inode = debugfs_get_inode(dentry->d_sb);
649 if (unlikely(!inode)) {
650 pr_err("out of free dentries, can not create automount '%s'\n",
651 name);
652 return failed_creating(dentry);
653 }
654
655 make_empty_dir_inode(inode);
656 inode->i_flags |= S_AUTOMOUNT;
657 inode->i_private = data;
658 dentry->d_fsdata = (void *)f;
659 /* directory inodes start off with i_nlink == 2 (for "." entry) */
660 inc_nlink(inode);
661 d_instantiate(dentry, inode);
662 inc_nlink(d_inode(dentry->d_parent));
663 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
664 return end_creating(dentry);
665}
666EXPORT_SYMBOL(debugfs_create_automount);
667
668/**
669 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
670 * @name: a pointer to a string containing the name of the symbolic link to
671 * create.
672 * @parent: a pointer to the parent dentry for this symbolic link. This
673 * should be a directory dentry if set. If this parameter is NULL,
674 * then the symbolic link will be created in the root of the debugfs
675 * filesystem.
676 * @target: a pointer to a string containing the path to the target of the
677 * symbolic link.
678 *
679 * This function creates a symbolic link with the given name in debugfs that
680 * links to the given target path.
681 *
682 * This function will return a pointer to a dentry if it succeeds. This
683 * pointer must be passed to the debugfs_remove() function when the symbolic
684 * link is to be removed (no automatic cleanup happens if your module is
685 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
686 * will be returned.
687 *
688 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
689 * returned.
690 */
691struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
692 const char *target)
693{
694 struct dentry *dentry;
695 struct inode *inode;
696 char *link = kstrdup(target, GFP_KERNEL);
697 if (!link)
698 return ERR_PTR(-ENOMEM);
699
700 dentry = start_creating(name, parent);
701 if (IS_ERR(dentry)) {
702 kfree(link);
703 return dentry;
704 }
705
706 inode = debugfs_get_inode(dentry->d_sb);
707 if (unlikely(!inode)) {
708 pr_err("out of free dentries, can not create symlink '%s'\n",
709 name);
710 kfree(link);
711 return failed_creating(dentry);
712 }
713 inode->i_mode = S_IFLNK | S_IRWXUGO;
714 inode->i_op = &debugfs_symlink_inode_operations;
715 inode->i_link = link;
716 d_instantiate(dentry, inode);
717 return end_creating(dentry);
718}
719EXPORT_SYMBOL_GPL(debugfs_create_symlink);
720
721static void __debugfs_file_removed(struct dentry *dentry)
722{
723 struct debugfs_fsdata *fsd;
724
725 /*
726 * Paired with the closing smp_mb() implied by a successful
727 * cmpxchg() in debugfs_file_get(): either
728 * debugfs_file_get() must see a dead dentry or we must see a
729 * debugfs_fsdata instance at ->d_fsdata here (or both).
730 */
731 smp_mb();
732 fsd = READ_ONCE(dentry->d_fsdata);
733 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
734 return;
735 if (!refcount_dec_and_test(&fsd->active_users))
736 wait_for_completion(&fsd->active_users_drained);
737}
738
739static void remove_one(struct dentry *victim)
740{
741 if (d_is_reg(victim))
742 __debugfs_file_removed(victim);
743 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
744}
745
746/**
747 * debugfs_remove - recursively removes a directory
748 * @dentry: a pointer to a the dentry of the directory to be removed. If this
749 * parameter is NULL or an error value, nothing will be done.
750 *
751 * This function recursively removes a directory tree in debugfs that
752 * was previously created with a call to another debugfs function
753 * (like debugfs_create_file() or variants thereof.)
754 *
755 * This function is required to be called in order for the file to be
756 * removed, no automatic cleanup of files will happen when a module is
757 * removed, you are responsible here.
758 */
759void debugfs_remove(struct dentry *dentry)
760{
761 if (IS_ERR_OR_NULL(dentry))
762 return;
763
764 simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
765 simple_recursive_removal(dentry, remove_one);
766 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
767}
768EXPORT_SYMBOL_GPL(debugfs_remove);
769
770/**
771 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
772 * @name: a pointer to a string containing the name of the item to look up.
773 * @parent: a pointer to the parent dentry of the item.
774 *
775 * This is the equlivant of doing something like
776 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
777 * handled for the directory being looked up.
778 */
779void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
780{
781 struct dentry *dentry;
782
783 dentry = debugfs_lookup(name, parent);
784 if (!dentry)
785 return;
786
787 debugfs_remove(dentry);
788 dput(dentry);
789}
790EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
791
792/**
793 * debugfs_rename - rename a file/directory in the debugfs filesystem
794 * @old_dir: a pointer to the parent dentry for the renamed object. This
795 * should be a directory dentry.
796 * @old_dentry: dentry of an object to be renamed.
797 * @new_dir: a pointer to the parent dentry where the object should be
798 * moved. This should be a directory dentry.
799 * @new_name: a pointer to a string containing the target name.
800 *
801 * This function renames a file/directory in debugfs. The target must not
802 * exist for rename to succeed.
803 *
804 * This function will return a pointer to old_dentry (which is updated to
805 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
806 * returned.
807 *
808 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
809 * returned.
810 */
811struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
812 struct dentry *new_dir, const char *new_name)
813{
814 int error;
815 struct dentry *dentry = NULL, *trap;
816 struct name_snapshot old_name;
817
818 if (IS_ERR(old_dir))
819 return old_dir;
820 if (IS_ERR(new_dir))
821 return new_dir;
822 if (IS_ERR_OR_NULL(old_dentry))
823 return old_dentry;
824
825 trap = lock_rename(new_dir, old_dir);
826 /* Source or destination directories don't exist? */
827 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
828 goto exit;
829 /* Source does not exist, cyclic rename, or mountpoint? */
830 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
831 d_mountpoint(old_dentry))
832 goto exit;
833 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
834 /* Lookup failed, cyclic rename or target exists? */
835 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
836 goto exit;
837
838 take_dentry_name_snapshot(&old_name, old_dentry);
839
840 error = simple_rename(&init_user_ns, d_inode(old_dir), old_dentry,
841 d_inode(new_dir), dentry, 0);
842 if (error) {
843 release_dentry_name_snapshot(&old_name);
844 goto exit;
845 }
846 d_move(old_dentry, dentry);
847 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
848 d_is_dir(old_dentry),
849 NULL, old_dentry);
850 release_dentry_name_snapshot(&old_name);
851 unlock_rename(new_dir, old_dir);
852 dput(dentry);
853 return old_dentry;
854exit:
855 if (dentry && !IS_ERR(dentry))
856 dput(dentry);
857 unlock_rename(new_dir, old_dir);
858 if (IS_ERR(dentry))
859 return dentry;
860 return ERR_PTR(-EINVAL);
861}
862EXPORT_SYMBOL_GPL(debugfs_rename);
863
864/**
865 * debugfs_initialized - Tells whether debugfs has been registered
866 */
867bool debugfs_initialized(void)
868{
869 return debugfs_registered;
870}
871EXPORT_SYMBOL_GPL(debugfs_initialized);
872
873static int __init debugfs_kernel(char *str)
874{
875 if (str) {
876 if (!strcmp(str, "on"))
877 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
878 else if (!strcmp(str, "no-mount"))
879 debugfs_allow = DEBUGFS_ALLOW_API;
880 else if (!strcmp(str, "off"))
881 debugfs_allow = 0;
882 }
883
884 return 0;
885}
886early_param("debugfs", debugfs_kernel);
887static int __init debugfs_init(void)
888{
889 int retval;
890
891 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
892 return -EPERM;
893
894 retval = sysfs_create_mount_point(kernel_kobj, "debug");
895 if (retval)
896 return retval;
897
898 retval = register_filesystem(&debug_fs_type);
899 if (retval)
900 sysfs_remove_mount_point(kernel_kobj, "debug");
901 else
902 debugfs_registered = true;
903
904 return retval;
905}
906core_initcall(debugfs_init);
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#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/magic.h>
27#include <linux/slab.h>
28
29static struct vfsmount *debugfs_mount;
30static int debugfs_mount_count;
31static bool debugfs_registered;
32
33static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev,
34 void *data, const struct file_operations *fops)
35
36{
37 struct inode *inode = new_inode(sb);
38
39 if (inode) {
40 inode->i_ino = get_next_ino();
41 inode->i_mode = mode;
42 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
43 switch (mode & S_IFMT) {
44 default:
45 init_special_inode(inode, mode, dev);
46 break;
47 case S_IFREG:
48 inode->i_fop = fops ? fops : &debugfs_file_operations;
49 inode->i_private = data;
50 break;
51 case S_IFLNK:
52 inode->i_op = &debugfs_link_operations;
53 inode->i_fop = fops;
54 inode->i_private = data;
55 break;
56 case S_IFDIR:
57 inode->i_op = &simple_dir_inode_operations;
58 inode->i_fop = fops ? fops : &simple_dir_operations;
59 inode->i_private = data;
60
61 /* directory inodes start off with i_nlink == 2
62 * (for "." entry) */
63 inc_nlink(inode);
64 break;
65 }
66 }
67 return inode;
68}
69
70/* SMP-safe */
71static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
72 int mode, dev_t dev, void *data,
73 const struct file_operations *fops)
74{
75 struct inode *inode;
76 int error = -EPERM;
77
78 if (dentry->d_inode)
79 return -EEXIST;
80
81 inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops);
82 if (inode) {
83 d_instantiate(dentry, inode);
84 dget(dentry);
85 error = 0;
86 }
87 return error;
88}
89
90static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode,
91 void *data, const struct file_operations *fops)
92{
93 int res;
94
95 mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
96 res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
97 if (!res) {
98 inc_nlink(dir);
99 fsnotify_mkdir(dir, dentry);
100 }
101 return res;
102}
103
104static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode,
105 void *data, const struct file_operations *fops)
106{
107 mode = (mode & S_IALLUGO) | S_IFLNK;
108 return debugfs_mknod(dir, dentry, mode, 0, data, fops);
109}
110
111static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode,
112 void *data, const struct file_operations *fops)
113{
114 int res;
115
116 mode = (mode & S_IALLUGO) | S_IFREG;
117 res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
118 if (!res)
119 fsnotify_create(dir, dentry);
120 return res;
121}
122
123static inline int debugfs_positive(struct dentry *dentry)
124{
125 return dentry->d_inode && !d_unhashed(dentry);
126}
127
128static int debug_fill_super(struct super_block *sb, void *data, int silent)
129{
130 static struct tree_descr debug_files[] = {{""}};
131
132 return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
133}
134
135static struct dentry *debug_mount(struct file_system_type *fs_type,
136 int flags, const char *dev_name,
137 void *data)
138{
139 return mount_single(fs_type, flags, data, debug_fill_super);
140}
141
142static struct file_system_type debug_fs_type = {
143 .owner = THIS_MODULE,
144 .name = "debugfs",
145 .mount = debug_mount,
146 .kill_sb = kill_litter_super,
147};
148
149static int debugfs_create_by_name(const char *name, mode_t mode,
150 struct dentry *parent,
151 struct dentry **dentry,
152 void *data,
153 const struct file_operations *fops)
154{
155 int error = 0;
156
157 /* If the parent is not specified, we create it in the root.
158 * We need the root dentry to do this, which is in the super
159 * block. A pointer to that is in the struct vfsmount that we
160 * have around.
161 */
162 if (!parent)
163 parent = debugfs_mount->mnt_sb->s_root;
164
165 *dentry = NULL;
166 mutex_lock(&parent->d_inode->i_mutex);
167 *dentry = lookup_one_len(name, parent, strlen(name));
168 if (!IS_ERR(*dentry)) {
169 switch (mode & S_IFMT) {
170 case S_IFDIR:
171 error = debugfs_mkdir(parent->d_inode, *dentry, mode,
172 data, fops);
173 break;
174 case S_IFLNK:
175 error = debugfs_link(parent->d_inode, *dentry, mode,
176 data, fops);
177 break;
178 default:
179 error = debugfs_create(parent->d_inode, *dentry, mode,
180 data, fops);
181 break;
182 }
183 dput(*dentry);
184 } else
185 error = PTR_ERR(*dentry);
186 mutex_unlock(&parent->d_inode->i_mutex);
187
188 return error;
189}
190
191/**
192 * debugfs_create_file - create a file in the debugfs filesystem
193 * @name: a pointer to a string containing the name of the file to create.
194 * @mode: the permission that the file should have.
195 * @parent: a pointer to the parent dentry for this file. This should be a
196 * directory dentry if set. If this paramater is NULL, then the
197 * file will be created in the root of the debugfs filesystem.
198 * @data: a pointer to something that the caller will want to get to later
199 * on. The inode.i_private pointer will point to this value on
200 * the open() call.
201 * @fops: a pointer to a struct file_operations that should be used for
202 * this file.
203 *
204 * This is the basic "create a file" function for debugfs. It allows for a
205 * wide range of flexibility in creating a file, or a directory (if you want
206 * to create a directory, the debugfs_create_dir() function is
207 * recommended to be used instead.)
208 *
209 * This function will return a pointer to a dentry if it succeeds. This
210 * pointer must be passed to the debugfs_remove() function when the file is
211 * to be removed (no automatic cleanup happens if your module is unloaded,
212 * you are responsible here.) If an error occurs, %NULL will be returned.
213 *
214 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
215 * returned.
216 */
217struct dentry *debugfs_create_file(const char *name, mode_t mode,
218 struct dentry *parent, void *data,
219 const struct file_operations *fops)
220{
221 struct dentry *dentry = NULL;
222 int error;
223
224 pr_debug("debugfs: creating file '%s'\n",name);
225
226 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
227 &debugfs_mount_count);
228 if (error)
229 goto exit;
230
231 error = debugfs_create_by_name(name, mode, parent, &dentry,
232 data, fops);
233 if (error) {
234 dentry = NULL;
235 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
236 goto exit;
237 }
238exit:
239 return dentry;
240}
241EXPORT_SYMBOL_GPL(debugfs_create_file);
242
243/**
244 * debugfs_create_dir - create a directory in the debugfs filesystem
245 * @name: a pointer to a string containing the name of the directory to
246 * create.
247 * @parent: a pointer to the parent dentry for this file. This should be a
248 * directory dentry if set. If this paramater is NULL, then the
249 * directory will be created in the root of the debugfs filesystem.
250 *
251 * This function creates a directory in debugfs with the given name.
252 *
253 * This function will return a pointer to a dentry if it succeeds. This
254 * pointer must be passed to the debugfs_remove() function when the file is
255 * to be removed (no automatic cleanup happens if your module is unloaded,
256 * you are responsible here.) If an error occurs, %NULL will be returned.
257 *
258 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
259 * returned.
260 */
261struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
262{
263 return debugfs_create_file(name,
264 S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
265 parent, NULL, NULL);
266}
267EXPORT_SYMBOL_GPL(debugfs_create_dir);
268
269/**
270 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
271 * @name: a pointer to a string containing the name of the symbolic link to
272 * create.
273 * @parent: a pointer to the parent dentry for this symbolic link. This
274 * should be a directory dentry if set. If this paramater is NULL,
275 * then the symbolic link will be created in the root of the debugfs
276 * filesystem.
277 * @target: a pointer to a string containing the path to the target of the
278 * symbolic link.
279 *
280 * This function creates a symbolic link with the given name in debugfs that
281 * links to the given target path.
282 *
283 * This function will return a pointer to a dentry if it succeeds. This
284 * pointer must be passed to the debugfs_remove() function when the symbolic
285 * link is to be removed (no automatic cleanup happens if your module is
286 * unloaded, you are responsible here.) If an error occurs, %NULL will be
287 * returned.
288 *
289 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
290 * returned.
291 */
292struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
293 const char *target)
294{
295 struct dentry *result;
296 char *link;
297
298 link = kstrdup(target, GFP_KERNEL);
299 if (!link)
300 return NULL;
301
302 result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
303 NULL);
304 if (!result)
305 kfree(link);
306 return result;
307}
308EXPORT_SYMBOL_GPL(debugfs_create_symlink);
309
310static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
311{
312 int ret = 0;
313
314 if (debugfs_positive(dentry)) {
315 if (dentry->d_inode) {
316 dget(dentry);
317 switch (dentry->d_inode->i_mode & S_IFMT) {
318 case S_IFDIR:
319 ret = simple_rmdir(parent->d_inode, dentry);
320 break;
321 case S_IFLNK:
322 kfree(dentry->d_inode->i_private);
323 /* fall through */
324 default:
325 simple_unlink(parent->d_inode, dentry);
326 break;
327 }
328 if (!ret)
329 d_delete(dentry);
330 dput(dentry);
331 }
332 }
333 return ret;
334}
335
336/**
337 * debugfs_remove - removes a file or directory from the debugfs filesystem
338 * @dentry: a pointer to a the dentry of the file or directory to be
339 * removed.
340 *
341 * This function removes a file or directory in debugfs that was previously
342 * created with a call to another debugfs function (like
343 * debugfs_create_file() or variants thereof.)
344 *
345 * This function is required to be called in order for the file to be
346 * removed, no automatic cleanup of files will happen when a module is
347 * removed, you are responsible here.
348 */
349void debugfs_remove(struct dentry *dentry)
350{
351 struct dentry *parent;
352 int ret;
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 ret = __debugfs_remove(dentry, parent);
363 mutex_unlock(&parent->d_inode->i_mutex);
364 if (!ret)
365 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
366}
367EXPORT_SYMBOL_GPL(debugfs_remove);
368
369/**
370 * debugfs_remove_recursive - recursively removes a directory
371 * @dentry: a pointer to a the dentry of the directory to be removed.
372 *
373 * This function recursively removes a directory tree in debugfs that
374 * was previously created with a call to another debugfs function
375 * (like debugfs_create_file() or variants thereof.)
376 *
377 * This function is required to be called in order for the file to be
378 * removed, no automatic cleanup of files will happen when a module is
379 * removed, you are responsible here.
380 */
381void debugfs_remove_recursive(struct dentry *dentry)
382{
383 struct dentry *child;
384 struct dentry *parent;
385
386 if (!dentry)
387 return;
388
389 parent = dentry->d_parent;
390 if (!parent || !parent->d_inode)
391 return;
392
393 parent = dentry;
394 mutex_lock(&parent->d_inode->i_mutex);
395
396 while (1) {
397 /*
398 * When all dentries under "parent" has been removed,
399 * walk up the tree until we reach our starting point.
400 */
401 if (list_empty(&parent->d_subdirs)) {
402 mutex_unlock(&parent->d_inode->i_mutex);
403 if (parent == dentry)
404 break;
405 parent = parent->d_parent;
406 mutex_lock(&parent->d_inode->i_mutex);
407 }
408 child = list_entry(parent->d_subdirs.next, struct dentry,
409 d_u.d_child);
410 next_sibling:
411
412 /*
413 * If "child" isn't empty, walk down the tree and
414 * remove all its descendants first.
415 */
416 if (!list_empty(&child->d_subdirs)) {
417 mutex_unlock(&parent->d_inode->i_mutex);
418 parent = child;
419 mutex_lock(&parent->d_inode->i_mutex);
420 continue;
421 }
422 __debugfs_remove(child, parent);
423 if (parent->d_subdirs.next == &child->d_u.d_child) {
424 /*
425 * Try the next sibling.
426 */
427 if (child->d_u.d_child.next != &parent->d_subdirs) {
428 child = list_entry(child->d_u.d_child.next,
429 struct dentry,
430 d_u.d_child);
431 goto next_sibling;
432 }
433
434 /*
435 * Avoid infinite loop if we fail to remove
436 * one dentry.
437 */
438 mutex_unlock(&parent->d_inode->i_mutex);
439 break;
440 }
441 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
442 }
443
444 parent = dentry->d_parent;
445 mutex_lock(&parent->d_inode->i_mutex);
446 __debugfs_remove(dentry, parent);
447 mutex_unlock(&parent->d_inode->i_mutex);
448 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
449}
450EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
451
452/**
453 * debugfs_rename - rename a file/directory in the debugfs filesystem
454 * @old_dir: a pointer to the parent dentry for the renamed object. This
455 * should be a directory dentry.
456 * @old_dentry: dentry of an object to be renamed.
457 * @new_dir: a pointer to the parent dentry where the object should be
458 * moved. This should be a directory dentry.
459 * @new_name: a pointer to a string containing the target name.
460 *
461 * This function renames a file/directory in debugfs. The target must not
462 * exist for rename to succeed.
463 *
464 * This function will return a pointer to old_dentry (which is updated to
465 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
466 * returned.
467 *
468 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
469 * returned.
470 */
471struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
472 struct dentry *new_dir, const char *new_name)
473{
474 int error;
475 struct dentry *dentry = NULL, *trap;
476 const char *old_name;
477
478 trap = lock_rename(new_dir, old_dir);
479 /* Source or destination directories don't exist? */
480 if (!old_dir->d_inode || !new_dir->d_inode)
481 goto exit;
482 /* Source does not exist, cyclic rename, or mountpoint? */
483 if (!old_dentry->d_inode || old_dentry == trap ||
484 d_mountpoint(old_dentry))
485 goto exit;
486 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
487 /* Lookup failed, cyclic rename or target exists? */
488 if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
489 goto exit;
490
491 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
492
493 error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
494 dentry);
495 if (error) {
496 fsnotify_oldname_free(old_name);
497 goto exit;
498 }
499 d_move(old_dentry, dentry);
500 fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
501 S_ISDIR(old_dentry->d_inode->i_mode),
502 NULL, old_dentry);
503 fsnotify_oldname_free(old_name);
504 unlock_rename(new_dir, old_dir);
505 dput(dentry);
506 return old_dentry;
507exit:
508 if (dentry && !IS_ERR(dentry))
509 dput(dentry);
510 unlock_rename(new_dir, old_dir);
511 return NULL;
512}
513EXPORT_SYMBOL_GPL(debugfs_rename);
514
515/**
516 * debugfs_initialized - Tells whether debugfs has been registered
517 */
518bool debugfs_initialized(void)
519{
520 return debugfs_registered;
521}
522EXPORT_SYMBOL_GPL(debugfs_initialized);
523
524
525static struct kobject *debug_kobj;
526
527static int __init debugfs_init(void)
528{
529 int retval;
530
531 debug_kobj = kobject_create_and_add("debug", kernel_kobj);
532 if (!debug_kobj)
533 return -EINVAL;
534
535 retval = register_filesystem(&debug_fs_type);
536 if (retval)
537 kobject_put(debug_kobj);
538 else
539 debugfs_registered = true;
540
541 return retval;
542}
543core_initcall(debugfs_init);
544