inode.c

  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/fs_context.h>
 18#include <linux/fs_parser.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/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 bool debugfs_enabled __ro_after_init = IS_ENABLED(CONFIG_DEBUG_FS_ALLOW_ALL);
 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 mnt_idmap *idmap,
 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(&nop_mnt_idmap, 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		simple_inode_init_ts(inode);
 76	}
 77	return inode;
 78}
 79
 80struct debugfs_fs_info {
 81	kuid_t uid;
 82	kgid_t gid;
 83	umode_t mode;
 84	/* Opt_* bitfield. */
 85	unsigned int opts;
 86};
 87
 88enum {
 89	Opt_uid,
 90	Opt_gid,
 91	Opt_mode,
 92	Opt_source,
 93};
 94
 95static const struct fs_parameter_spec debugfs_param_specs[] = {
 96	fsparam_gid	("gid",		Opt_gid),
 97	fsparam_u32oct	("mode",	Opt_mode),
 98	fsparam_uid	("uid",		Opt_uid),
 99	fsparam_string	("source",	Opt_source),
100	{}
101};
102
103static int debugfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
104{
105	struct debugfs_fs_info *opts = fc->s_fs_info;
106	struct fs_parse_result result;
107	int opt;
108
109	opt = fs_parse(fc, debugfs_param_specs, param, &result);
110	if (opt < 0) {
111		/*
112                * We might like to report bad mount options here; but
113                * traditionally debugfs has ignored all mount options
114                */
115		if (opt == -ENOPARAM)
116			return 0;
117
118		return opt;
119	}
120
121	switch (opt) {
122	case Opt_uid:
123		opts->uid = result.uid;
124		break;
125	case Opt_gid:
126		opts->gid = result.gid;
127		break;
128	case Opt_mode:
129		opts->mode = result.uint_32 & S_IALLUGO;
130		break;
131	case Opt_source:
132		if (fc->source)
133			return invalfc(fc, "Multiple sources specified");
134		fc->source = param->string;
135		param->string = NULL;
136		break;
137	/*
138	 * We might like to report bad mount options here;
139	 * but traditionally debugfs has ignored all mount options
140	 */
141	}
142
143	opts->opts |= BIT(opt);
144
145	return 0;
146}
147
148static void _debugfs_apply_options(struct super_block *sb, bool remount)
149{
150	struct debugfs_fs_info *fsi = sb->s_fs_info;
151	struct inode *inode = d_inode(sb->s_root);
152
153	/*
154	 * On remount, only reset mode/uid/gid if they were provided as mount
155	 * options.
156	 */
157
158	if (!remount || fsi->opts & BIT(Opt_mode)) {
159		inode->i_mode &= ~S_IALLUGO;
160		inode->i_mode |= fsi->mode;
161	}
162
163	if (!remount || fsi->opts & BIT(Opt_uid))
164		inode->i_uid = fsi->uid;
165
166	if (!remount || fsi->opts & BIT(Opt_gid))
167		inode->i_gid = fsi->gid;
168}
169
170static void debugfs_apply_options(struct super_block *sb)
171{
172	_debugfs_apply_options(sb, false);
173}
174
175static void debugfs_apply_options_remount(struct super_block *sb)
176{
177	_debugfs_apply_options(sb, true);
178}
179
180static int debugfs_reconfigure(struct fs_context *fc)
181{
182	struct super_block *sb = fc->root->d_sb;
183	struct debugfs_fs_info *sb_opts = sb->s_fs_info;
184	struct debugfs_fs_info *new_opts = fc->s_fs_info;
185
186	if (!new_opts)
187		return 0;
188
189	sync_filesystem(sb);
190
191	/* structure copy of new mount options to sb */
192	*sb_opts = *new_opts;
193	debugfs_apply_options_remount(sb);
194
195	return 0;
196}
197
198static int debugfs_show_options(struct seq_file *m, struct dentry *root)
199{
200	struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
201
202	if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID))
203		seq_printf(m, ",uid=%u",
204			   from_kuid_munged(&init_user_ns, fsi->uid));
205	if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))
206		seq_printf(m, ",gid=%u",
207			   from_kgid_munged(&init_user_ns, fsi->gid));
208	if (fsi->mode != DEBUGFS_DEFAULT_MODE)
209		seq_printf(m, ",mode=%o", fsi->mode);
210
211	return 0;
212}
213
214static struct kmem_cache *debugfs_inode_cachep __ro_after_init;
215
216static void init_once(void *foo)
217{
218	struct debugfs_inode_info *info = foo;
219	inode_init_once(&info->vfs_inode);
220}
221
222static struct inode *debugfs_alloc_inode(struct super_block *sb)
223{
224	struct debugfs_inode_info *info;
225	info = alloc_inode_sb(sb, debugfs_inode_cachep, GFP_KERNEL);
226	if (!info)
227		return NULL;
228	return &info->vfs_inode;
229}
230
231static void debugfs_free_inode(struct inode *inode)
232{
233	if (S_ISLNK(inode->i_mode))
234		kfree(inode->i_link);
235	kmem_cache_free(debugfs_inode_cachep, DEBUGFS_I(inode));
236}
237
238static const struct super_operations debugfs_super_operations = {
239	.statfs		= simple_statfs,
240	.show_options	= debugfs_show_options,
241	.alloc_inode	= debugfs_alloc_inode,
242	.free_inode	= debugfs_free_inode,
243};
244
245static void debugfs_release_dentry(struct dentry *dentry)
246{
247	struct debugfs_fsdata *fsd = dentry->d_fsdata;
248
249	if (fsd) {
250		WARN_ON(!list_empty(&fsd->cancellations));
251		mutex_destroy(&fsd->cancellations_mtx);
252	}
253	kfree(fsd);
254}
255
256static struct vfsmount *debugfs_automount(struct path *path)
257{
258	struct inode *inode = path->dentry->d_inode;
259
260	return DEBUGFS_I(inode)->automount(path->dentry, inode->i_private);
261}
262
263static const struct dentry_operations debugfs_dops = {
264	.d_release = debugfs_release_dentry,
265	.d_automount = debugfs_automount,
266};
267
268static int debugfs_fill_super(struct super_block *sb, struct fs_context *fc)
269{
270	static const struct tree_descr debug_files[] = {{""}};
271	int err;
272
273	err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
274	if (err)
275		return err;
276
277	sb->s_op = &debugfs_super_operations;
278	set_default_d_op(sb, &debugfs_dops);
279	sb->s_d_flags |= DCACHE_DONTCACHE;
280
281	debugfs_apply_options(sb);
282
283	return 0;
284}
285
286static int debugfs_get_tree(struct fs_context *fc)
287{
288	int err;
289
290	err = get_tree_single(fc, debugfs_fill_super);
291	if (err)
292		return err;
293
294	return debugfs_reconfigure(fc);
295}
296
297static void debugfs_free_fc(struct fs_context *fc)
298{
299	kfree(fc->s_fs_info);
300}
301
302static const struct fs_context_operations debugfs_context_ops = {
303	.free		= debugfs_free_fc,
304	.parse_param	= debugfs_parse_param,
305	.get_tree	= debugfs_get_tree,
306	.reconfigure	= debugfs_reconfigure,
307};
308
309static int debugfs_init_fs_context(struct fs_context *fc)
310{
311	struct debugfs_fs_info *fsi;
312
313	fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
314	if (!fsi)
315		return -ENOMEM;
316
317	fsi->mode = DEBUGFS_DEFAULT_MODE;
318
319	fc->s_fs_info = fsi;
320	fc->ops = &debugfs_context_ops;
321	return 0;
322}
323
324static struct file_system_type debug_fs_type = {
325	.owner =	THIS_MODULE,
326	.name =		"debugfs",
327	.init_fs_context = debugfs_init_fs_context,
328	.parameters =	debugfs_param_specs,
329	.kill_sb =	kill_anon_super,
330};
331MODULE_ALIAS_FS("debugfs");
332
333/**
334 * debugfs_lookup() - look up an existing debugfs file
335 * @name: a pointer to a string containing the name of the file to look up.
336 * @parent: a pointer to the parent dentry of the file.
337 *
338 * This function will return a pointer to a dentry if it succeeds.  If the file
339 * doesn't exist or an error occurs, %NULL will be returned.  The returned
340 * dentry must be passed to dput() when it is no longer needed.
341 *
342 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
343 * returned.
344 */
345struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
346{
347	struct dentry *dentry;
348
349	if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
350		return NULL;
351
352	if (!parent)
353		parent = debugfs_mount->mnt_root;
354
355	dentry = lookup_noperm_positive_unlocked(&QSTR(name), parent);
356	if (IS_ERR(dentry))
357		return NULL;
358	return dentry;
359}
360EXPORT_SYMBOL_GPL(debugfs_lookup);
361
362static struct dentry *debugfs_start_creating(const char *name,
363					     struct dentry *parent)
364{
365	struct dentry *dentry;
366	int error;
367
368	if (!debugfs_enabled)
369		return ERR_PTR(-EPERM);
370
371	if (!debugfs_initialized())
372		return ERR_PTR(-ENOENT);
373
374	pr_debug("creating file '%s'\n", name);
375
376	if (IS_ERR(parent))
377		return parent;
378
379	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
380			      &debugfs_mount_count);
381	if (error) {
382		pr_err("Unable to pin filesystem for file '%s'\n", name);
383		return ERR_PTR(error);
384	}
385
386	/* If the parent is not specified, we create it in the root.
387	 * We need the root dentry to do this, which is in the super
388	 * block. A pointer to that is in the struct vfsmount that we
389	 * have around.
390	 */
391	if (!parent)
392		parent = debugfs_mount->mnt_root;
393
394	dentry = simple_start_creating(parent, name);
395	if (IS_ERR(dentry)) {
396		if (dentry == ERR_PTR(-EEXIST))
397			pr_err("'%s' already exists in '%pd'\n", name, parent);
398		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
399	}
400	return dentry;
401}
402
403static struct dentry *debugfs_failed_creating(struct dentry *dentry)
404{
405	simple_done_creating(dentry);
406	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
407	return ERR_PTR(-ENOMEM);
408}
409
410static struct dentry *debugfs_end_creating(struct dentry *dentry)
411{
412	simple_done_creating(dentry);
413	return dentry; // borrowed
414}
415
416static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
417				struct dentry *parent, void *data,
418				const void *aux,
419				const struct file_operations *proxy_fops,
420				const void *real_fops)
421{
422	struct dentry *dentry;
423	struct inode *inode;
424
425	if (!(mode & S_IFMT))
426		mode |= S_IFREG;
427	BUG_ON(!S_ISREG(mode));
428	dentry = debugfs_start_creating(name, parent);
429
430	if (IS_ERR(dentry))
431		return dentry;
432
433	inode = debugfs_get_inode(dentry->d_sb);
434	if (unlikely(!inode)) {
435		pr_err("out of free dentries, can not create file '%s'\n",
436		       name);
437		return debugfs_failed_creating(dentry);
438	}
439
440	inode->i_mode = mode;
441	inode->i_private = data;
442
443	inode->i_op = &debugfs_file_inode_operations;
444	if (!real_fops)
445		proxy_fops = &debugfs_noop_file_operations;
446	inode->i_fop = proxy_fops;
447	DEBUGFS_I(inode)->raw = real_fops;
448	DEBUGFS_I(inode)->aux = (void *)aux;
449
450	d_make_persistent(dentry, inode);
451	fsnotify_create(d_inode(dentry->d_parent), dentry);
452	return debugfs_end_creating(dentry);
453}
454
455struct dentry *debugfs_create_file_full(const char *name, umode_t mode,
456					struct dentry *parent, void *data,
457					const void *aux,
458					const struct file_operations *fops)
459{
460	return __debugfs_create_file(name, mode, parent, data, aux,
461				&debugfs_full_proxy_file_operations,
462				fops);
463}
464EXPORT_SYMBOL_GPL(debugfs_create_file_full);
465
466struct dentry *debugfs_create_file_short(const char *name, umode_t mode,
467					struct dentry *parent, void *data,
468					const void *aux,
469					const struct debugfs_short_fops *fops)
470{
471	return __debugfs_create_file(name, mode, parent, data, aux,
472				&debugfs_full_short_proxy_file_operations,
473				fops);
474}
475EXPORT_SYMBOL_GPL(debugfs_create_file_short);
476
477/**
478 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
479 * @name: a pointer to a string containing the name of the file to create.
480 * @mode: the permission that the file should have.
481 * @parent: a pointer to the parent dentry for this file.  This should be a
482 *          directory dentry if set.  If this parameter is NULL, then the
483 *          file will be created in the root of the debugfs filesystem.
484 * @data: a pointer to something that the caller will want to get to later
485 *        on.  The inode.i_private pointer will point to this value on
486 *        the open() call.
487 * @fops: a pointer to a struct file_operations that should be used for
488 *        this file.
489 *
490 * debugfs_create_file_unsafe() is completely analogous to
491 * debugfs_create_file(), the only difference being that the fops
492 * handed it will not get protected against file removals by the
493 * debugfs core.
494 *
495 * It is your responsibility to protect your struct file_operation
496 * methods against file removals by means of debugfs_file_get()
497 * and debugfs_file_put(). ->open() is still protected by
498 * debugfs though.
499 *
500 * Any struct file_operations defined by means of
501 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
502 * thus, may be used here.
503 */
504struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
505				   struct dentry *parent, void *data,
506				   const struct file_operations *fops)
507{
508
509	return __debugfs_create_file(name, mode, parent, data, NULL,
510				&debugfs_open_proxy_file_operations,
511				fops);
512}
513EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
514
515/**
516 * debugfs_create_file_size - create a file in the debugfs filesystem
517 * @name: a pointer to a string containing the name of the file to create.
518 * @mode: the permission that the file should have.
519 * @parent: a pointer to the parent dentry for this file.  This should be a
520 *          directory dentry if set.  If this parameter is NULL, then the
521 *          file will be created in the root of the debugfs filesystem.
522 * @data: a pointer to something that the caller will want to get to later
523 *        on.  The inode.i_private pointer will point to this value on
524 *        the open() call.
525 * @fops: a pointer to a struct file_operations that should be used for
526 *        this file.
527 * @file_size: initial file size
528 *
529 * This is the basic "create a file" function for debugfs.  It allows for a
530 * wide range of flexibility in creating a file, or a directory (if you want
531 * to create a directory, the debugfs_create_dir() function is
532 * recommended to be used instead.)
533 */
534void debugfs_create_file_size(const char *name, umode_t mode,
535			      struct dentry *parent, void *data,
536			      const struct file_operations *fops,
537			      loff_t file_size)
538{
539	struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
540
541	if (!IS_ERR(de))
542		d_inode(de)->i_size = file_size;
543}
544EXPORT_SYMBOL_GPL(debugfs_create_file_size);
545
546/**
547 * debugfs_create_dir - create a directory in the debugfs filesystem
548 * @name: a pointer to a string containing the name of the directory to
549 *        create.
550 * @parent: a pointer to the parent dentry for this file.  This should be a
551 *          directory dentry if set.  If this parameter is NULL, then the
552 *          directory will be created in the root of the debugfs filesystem.
553 *
554 * This function creates a directory in debugfs with the given name.
555 *
556 * This function will return a pointer to a dentry if it succeeds.  This
557 * pointer must be passed to the debugfs_remove() function when the file is
558 * to be removed (no automatic cleanup happens if your module is unloaded,
559 * you are responsible here.)  If an error occurs, ERR_PTR(-ERROR) will be
560 * returned.
561 *
562 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
563 * returned.
564 *
565 * NOTE: it's expected that most callers should _ignore_ the errors returned
566 * by this function. Other debugfs functions handle the fact that the "dentry"
567 * passed to them could be an error and they don't crash in that case.
568 * Drivers should generally work fine even if debugfs fails to init anyway.
569 */
570struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
571{
572	struct dentry *dentry = debugfs_start_creating(name, parent);
573	struct inode *inode;
574
575	if (IS_ERR(dentry))
576		return dentry;
577
578	inode = debugfs_get_inode(dentry->d_sb);
579	if (unlikely(!inode)) {
580		pr_err("out of free dentries, can not create directory '%s'\n",
581		       name);
582		return debugfs_failed_creating(dentry);
583	}
584
585	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
586	inode->i_op = &debugfs_dir_inode_operations;
587	inode->i_fop = &simple_dir_operations;
588
589	/* directory inodes start off with i_nlink == 2 (for "." entry) */
590	inc_nlink(inode);
591	d_make_persistent(dentry, inode);
592	inc_nlink(d_inode(dentry->d_parent));
593	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
594	return debugfs_end_creating(dentry);
595}
596EXPORT_SYMBOL_GPL(debugfs_create_dir);
597
598/**
599 * debugfs_create_automount - create automount point in the debugfs filesystem
600 * @name: a pointer to a string containing the name of the file to create.
601 * @parent: a pointer to the parent dentry for this file.  This should be a
602 *          directory dentry if set.  If this parameter is NULL, then the
603 *          file will be created in the root of the debugfs filesystem.
604 * @f: function to be called when pathname resolution steps on that one.
605 * @data: opaque argument to pass to f().
606 *
607 * @f should return what ->d_automount() would.
608 */
609struct dentry *debugfs_create_automount(const char *name,
610					struct dentry *parent,
611					debugfs_automount_t f,
612					void *data)
613{
614	struct dentry *dentry = debugfs_start_creating(name, parent);
615	struct inode *inode;
616
617	if (IS_ERR(dentry))
618		return dentry;
619
620	inode = debugfs_get_inode(dentry->d_sb);
621	if (unlikely(!inode)) {
622		pr_err("out of free dentries, can not create automount '%s'\n",
623		       name);
624		return debugfs_failed_creating(dentry);
625	}
626
627	make_empty_dir_inode(inode);
628	inode->i_flags |= S_AUTOMOUNT;
629	inode->i_private = data;
630	DEBUGFS_I(inode)->automount = f;
631	/* directory inodes start off with i_nlink == 2 (for "." entry) */
632	inc_nlink(inode);
633	d_make_persistent(dentry, inode);
634	inc_nlink(d_inode(dentry->d_parent));
635	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
636	return debugfs_end_creating(dentry);
637}
638EXPORT_SYMBOL(debugfs_create_automount);
639
640/**
641 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
642 * @name: a pointer to a string containing the name of the symbolic link to
643 *        create.
644 * @parent: a pointer to the parent dentry for this symbolic link.  This
645 *          should be a directory dentry if set.  If this parameter is NULL,
646 *          then the symbolic link will be created in the root of the debugfs
647 *          filesystem.
648 * @target: a pointer to a string containing the path to the target of the
649 *          symbolic link.
650 *
651 * This function creates a symbolic link with the given name in debugfs that
652 * links to the given target path.
653 *
654 * This function will return a pointer to a dentry if it succeeds.  This
655 * pointer must be passed to the debugfs_remove() function when the symbolic
656 * link is to be removed (no automatic cleanup happens if your module is
657 * unloaded, you are responsible here.)  If an error occurs, ERR_PTR(-ERROR)
658 * will be returned.
659 *
660 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
661 * returned.
662 */
663struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
664				      const char *target)
665{
666	struct dentry *dentry;
667	struct inode *inode;
668	char *link = kstrdup(target, GFP_KERNEL);
669	if (!link)
670		return ERR_PTR(-ENOMEM);
671
672	dentry = debugfs_start_creating(name, parent);
673	if (IS_ERR(dentry)) {
674		kfree(link);
675		return dentry;
676	}
677
678	inode = debugfs_get_inode(dentry->d_sb);
679	if (unlikely(!inode)) {
680		pr_err("out of free dentries, can not create symlink '%s'\n",
681		       name);
682		kfree(link);
683		return debugfs_failed_creating(dentry);
684	}
685	inode->i_mode = S_IFLNK | S_IRWXUGO;
686	inode->i_op = &debugfs_symlink_inode_operations;
687	inode->i_link = link;
688	d_make_persistent(dentry, inode);
689	return debugfs_end_creating(dentry);
690}
691EXPORT_SYMBOL_GPL(debugfs_create_symlink);
692
693static void __debugfs_file_removed(struct dentry *dentry)
694{
695	struct debugfs_fsdata *fsd;
696
697	/*
698	 * Paired with the closing smp_mb() implied by a successful
699	 * cmpxchg() in debugfs_file_get(): either
700	 * debugfs_file_get() must see a dead dentry or we must see a
701	 * debugfs_fsdata instance at ->d_fsdata here (or both).
702	 */
703	smp_mb();
704	fsd = READ_ONCE(dentry->d_fsdata);
705	if (!fsd)
706		return;
707
708	/* if this was the last reference, we're done */
709	if (refcount_dec_and_test(&fsd->active_users))
710		return;
711
712	/*
713	 * If there's still a reference, the code that obtained it can
714	 * be in different states:
715	 *  - The common case of not using cancellations, or already
716	 *    after debugfs_leave_cancellation(), where we just need
717	 *    to wait for debugfs_file_put() which signals the completion;
718	 *  - inside a cancellation section, i.e. between
719	 *    debugfs_enter_cancellation() and debugfs_leave_cancellation(),
720	 *    in which case we need to trigger the ->cancel() function,
721	 *    and then wait for debugfs_file_put() just like in the
722	 *    previous case;
723	 *  - before debugfs_enter_cancellation() (but obviously after
724	 *    debugfs_file_get()), in which case we may not see the
725	 *    cancellation in the list on the first round of the loop,
726	 *    but debugfs_enter_cancellation() signals the completion
727	 *    after adding it, so this code gets woken up to call the
728	 *    ->cancel() function.
729	 */
730	while (refcount_read(&fsd->active_users)) {
731		struct debugfs_cancellation *c;
732
733		/*
734		 * Lock the cancellations. Note that the cancellations
735		 * structs are meant to be on the stack, so we need to
736		 * ensure we either use them here or don't touch them,
737		 * and debugfs_leave_cancellation() will wait for this
738		 * to be finished processing before exiting one. It may
739		 * of course win and remove the cancellation, but then
740		 * chances are we never even got into this bit, we only
741		 * do if the refcount isn't zero already.
742		 */
743		mutex_lock(&fsd->cancellations_mtx);
744		while ((c = list_first_entry_or_null(&fsd->cancellations,
745						     typeof(*c), list))) {
746			list_del_init(&c->list);
747			c->cancel(dentry, c->cancel_data);
748		}
749		mutex_unlock(&fsd->cancellations_mtx);
750
751		wait_for_completion(&fsd->active_users_drained);
752	}
753}
754
755static void remove_one(struct dentry *victim)
756{
757        if (d_is_reg(victim))
758		__debugfs_file_removed(victim);
759	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
760}
761
762/**
763 * debugfs_remove - recursively removes a directory
764 * @dentry: a pointer to a the dentry of the directory to be removed.  If this
765 *          parameter is NULL or an error value, nothing will be done.
766 *
767 * This function recursively removes a directory tree in debugfs that
768 * was previously created with a call to another debugfs function
769 * (like debugfs_create_file() or variants thereof.)
770 *
771 * This function is required to be called in order for the file to be
772 * removed, no automatic cleanup of files will happen when a module is
773 * removed, you are responsible here.
774 */
775void debugfs_remove(struct dentry *dentry)
776{
777	if (IS_ERR_OR_NULL(dentry))
778		return;
779
780	simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
781	simple_recursive_removal(dentry, remove_one);
782	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
783}
784EXPORT_SYMBOL_GPL(debugfs_remove);
785
786/**
787 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
788 * @name: a pointer to a string containing the name of the item to look up.
789 * @parent: a pointer to the parent dentry of the item.
790 *
791 * This is the equlivant of doing something like
792 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
793 * handled for the directory being looked up.
794 */
795void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
796{
797	struct dentry *dentry;
798
799	dentry = debugfs_lookup(name, parent);
800	if (!dentry)
801		return;
802
803	debugfs_remove(dentry);
804	dput(dentry);
805}
806EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
807
808/**
809 * debugfs_change_name - rename a file/directory in the debugfs filesystem
810 * @dentry: dentry of an object to be renamed.
811 * @fmt: format for new name
812 *
813 * This function renames a file/directory in debugfs.  The target must not
814 * exist for rename to succeed.
815 *
816 * This function will return 0 on success and -E... on failure.
817 *
818 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
819 * returned.
820 */
821int __printf(2, 3) debugfs_change_name(struct dentry *dentry, const char *fmt, ...)
822{
823	int error = 0;
824	const char *new_name;
825	struct name_snapshot old_name;
826	struct dentry *target;
827	struct renamedata rd = {};
828	struct inode *dir;
829	va_list ap;
830
831	if (IS_ERR_OR_NULL(dentry))
832		return 0;
833
834	va_start(ap, fmt);
835	new_name = kvasprintf_const(GFP_KERNEL, fmt, ap);
836	va_end(ap);
837	if (!new_name)
838		return -ENOMEM;
839
840	rd.old_parent = dget_parent(dentry);
841	rd.new_parent = rd.old_parent;
842	rd.flags = RENAME_NOREPLACE;
843	target = lookup_noperm_unlocked(&QSTR(new_name), rd.new_parent);
844	if (IS_ERR(target)) {
845		error = PTR_ERR(target);
846		goto out_free;
847	}
848
849	error = start_renaming_two_dentries(&rd, dentry, target);
850	if (error) {
851		if (error == -EEXIST && target == dentry)
852			/* it isn't an error to rename a thing to itself */
853			error = 0;
854		goto out;
855	}
856
857	dir = d_inode(rd.old_parent);
858	take_dentry_name_snapshot(&old_name, dentry);
859	simple_rename_timestamp(dir, dentry, dir, rd.new_dentry);
860	d_move(dentry, rd.new_dentry);
861	fsnotify_move(dir, dir, &old_name.name, d_is_dir(dentry), NULL, dentry);
862	release_dentry_name_snapshot(&old_name);
863	end_renaming(&rd);
864out:
865	dput(rd.old_parent);
866	dput(target);
867out_free:
868	kfree_const(new_name);
869	return error;
870}
871EXPORT_SYMBOL_GPL(debugfs_change_name);
872
873/**
874 * debugfs_initialized - Tells whether debugfs has been registered
875 */
876bool debugfs_initialized(void)
877{
878	return debugfs_registered;
879}
880EXPORT_SYMBOL_GPL(debugfs_initialized);
881
882static int __init debugfs_kernel(char *str)
883{
884	if (str) {
885		if (!strcmp(str, "on"))
886			debugfs_enabled = true;
887		else if (!strcmp(str, "off"))
888			debugfs_enabled = false;
889		else if (!strcmp(str, "no-mount")) {
890			pr_notice("debugfs=no-mount is a deprecated alias "
891				  "for debugfs=off\n");
892			debugfs_enabled = false;
893		}
894	}
895
896	return 0;
897}
898early_param("debugfs", debugfs_kernel);
899
900static int __init debugfs_init(void)
901{
902	int retval;
903
904	if (!debugfs_enabled)
905		return -EPERM;
906
907	retval = sysfs_create_mount_point(kernel_kobj, "debug");
908	if (retval)
909		return retval;
910
911	debugfs_inode_cachep = kmem_cache_create("debugfs_inode_cache",
912				sizeof(struct debugfs_inode_info), 0,
913				SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
914				init_once);
915	if (debugfs_inode_cachep == NULL) {
916		sysfs_remove_mount_point(kernel_kobj, "debug");
917		return -ENOMEM;
918	}
919
920	retval = register_filesystem(&debug_fs_type);
921	if (retval) { // Really not going to happen
922		sysfs_remove_mount_point(kernel_kobj, "debug");
923		kmem_cache_destroy(debugfs_inode_cachep);
924		return retval;
925	}
926	debugfs_registered = true;
927	return 0;
928}
929core_initcall(debugfs_init);