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