1 // SPDX-License-Identifier: GPL-2.0
3 * inode.c - part of debugfs, a tiny little debug file system
5 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
6 * Copyright (C) 2004 IBM Inc.
8 * debugfs is for people to use instead of /proc or /sys.
9 * See ./Documentation/core-api/kernel-api.rst for more details.
12 #include <linux/module.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>
29 #define DEBUGFS_DEFAULT_MODE 0700
31 static struct vfsmount *debugfs_mount;
32 static int debugfs_mount_count;
33 static bool debugfs_registered;
35 static struct inode *debugfs_get_inode(struct super_block *sb)
37 struct inode *inode = new_inode(sb);
39 inode->i_ino = get_next_ino();
40 inode->i_atime = inode->i_mtime =
41 inode->i_ctime = current_time(inode);
46 struct debugfs_mount_opts {
59 static const match_table_t tokens = {
62 {Opt_mode, "mode=%o"},
66 struct debugfs_fs_info {
67 struct debugfs_mount_opts mount_opts;
70 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
72 substring_t args[MAX_OPT_ARGS];
79 opts->mode = DEBUGFS_DEFAULT_MODE;
81 while ((p = strsep(&data, ",")) != NULL) {
85 token = match_token(p, tokens, args);
88 if (match_int(&args[0], &option))
90 uid = make_kuid(current_user_ns(), option);
96 if (match_int(&args[0], &option))
98 gid = make_kgid(current_user_ns(), option);
104 if (match_octal(&args[0], &option))
106 opts->mode = option & S_IALLUGO;
109 * We might like to report bad mount options here;
110 * but traditionally debugfs has ignored all mount options
118 static int debugfs_apply_options(struct super_block *sb)
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;
124 inode->i_mode &= ~S_IALLUGO;
125 inode->i_mode |= opts->mode;
127 inode->i_uid = opts->uid;
128 inode->i_gid = opts->gid;
133 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
136 struct debugfs_fs_info *fsi = sb->s_fs_info;
139 err = debugfs_parse_options(data, &fsi->mount_opts);
143 debugfs_apply_options(sb);
149 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
151 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
152 struct debugfs_mount_opts *opts = &fsi->mount_opts;
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);
166 static void debugfs_i_callback(struct rcu_head *head)
168 struct inode *inode = container_of(head, struct inode, i_rcu);
169 if (S_ISLNK(inode->i_mode))
170 kfree(inode->i_link);
171 free_inode_nonrcu(inode);
174 static void debugfs_destroy_inode(struct inode *inode)
176 call_rcu(&inode->i_rcu, debugfs_i_callback);
179 static const struct super_operations debugfs_super_operations = {
180 .statfs = simple_statfs,
181 .remount_fs = debugfs_remount,
182 .show_options = debugfs_show_options,
183 .destroy_inode = debugfs_destroy_inode,
186 static void debugfs_release_dentry(struct dentry *dentry)
188 void *fsd = dentry->d_fsdata;
190 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
191 kfree(dentry->d_fsdata);
194 static struct vfsmount *debugfs_automount(struct path *path)
196 debugfs_automount_t f;
197 f = (debugfs_automount_t)path->dentry->d_fsdata;
198 return f(path->dentry, d_inode(path->dentry)->i_private);
201 static const struct dentry_operations debugfs_dops = {
202 .d_delete = always_delete_dentry,
203 .d_release = debugfs_release_dentry,
204 .d_automount = debugfs_automount,
207 static int debug_fill_super(struct super_block *sb, void *data, int silent)
209 static const struct tree_descr debug_files[] = {{""}};
210 struct debugfs_fs_info *fsi;
213 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
220 err = debugfs_parse_options(data, &fsi->mount_opts);
224 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
228 sb->s_op = &debugfs_super_operations;
229 sb->s_d_op = &debugfs_dops;
231 debugfs_apply_options(sb);
237 sb->s_fs_info = NULL;
241 static struct dentry *debug_mount(struct file_system_type *fs_type,
242 int flags, const char *dev_name,
245 return mount_single(fs_type, flags, data, debug_fill_super);
248 static struct file_system_type debug_fs_type = {
249 .owner = THIS_MODULE,
251 .mount = debug_mount,
252 .kill_sb = kill_litter_super,
254 MODULE_ALIAS_FS("debugfs");
257 * debugfs_lookup() - look up an existing debugfs file
258 * @name: a pointer to a string containing the name of the file to look up.
259 * @parent: a pointer to the parent dentry of the file.
261 * This function will return a pointer to a dentry if it succeeds. If the file
262 * doesn't exist or an error occurs, %NULL will be returned. The returned
263 * dentry must be passed to dput() when it is no longer needed.
265 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
268 struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
270 struct dentry *dentry;
276 parent = debugfs_mount->mnt_root;
278 dentry = lookup_positive_unlocked(name, parent, strlen(name));
283 EXPORT_SYMBOL_GPL(debugfs_lookup);
285 static struct dentry *start_creating(const char *name, struct dentry *parent)
287 struct dentry *dentry;
290 pr_debug("debugfs: creating file '%s'\n",name);
295 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
296 &debugfs_mount_count);
298 return ERR_PTR(error);
300 /* If the parent is not specified, we create it in the root.
301 * We need the root dentry to do this, which is in the super
302 * block. A pointer to that is in the struct vfsmount that we
306 parent = debugfs_mount->mnt_root;
308 inode_lock(d_inode(parent));
309 dentry = lookup_one_len(name, parent, strlen(name));
310 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
312 dentry = ERR_PTR(-EEXIST);
315 if (IS_ERR(dentry)) {
316 inode_unlock(d_inode(parent));
317 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
323 static struct dentry *failed_creating(struct dentry *dentry)
325 inode_unlock(d_inode(dentry->d_parent));
327 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
331 static struct dentry *end_creating(struct dentry *dentry)
333 inode_unlock(d_inode(dentry->d_parent));
337 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
338 struct dentry *parent, void *data,
339 const struct file_operations *proxy_fops,
340 const struct file_operations *real_fops)
342 struct dentry *dentry;
345 if (!(mode & S_IFMT))
347 BUG_ON(!S_ISREG(mode));
348 dentry = start_creating(name, parent);
353 inode = debugfs_get_inode(dentry->d_sb);
354 if (unlikely(!inode))
355 return failed_creating(dentry);
357 inode->i_mode = mode;
358 inode->i_private = data;
360 inode->i_fop = proxy_fops;
361 dentry->d_fsdata = (void *)((unsigned long)real_fops |
362 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
364 d_instantiate(dentry, inode);
365 fsnotify_create(d_inode(dentry->d_parent), dentry);
366 return end_creating(dentry);
370 * debugfs_create_file - create a file in the debugfs filesystem
371 * @name: a pointer to a string containing the name of the file to create.
372 * @mode: the permission that the file should have.
373 * @parent: a pointer to the parent dentry for this file. This should be a
374 * directory dentry if set. If this parameter is NULL, then the
375 * file will be created in the root of the debugfs filesystem.
376 * @data: a pointer to something that the caller will want to get to later
377 * on. The inode.i_private pointer will point to this value on
379 * @fops: a pointer to a struct file_operations that should be used for
382 * This is the basic "create a file" function for debugfs. It allows for a
383 * wide range of flexibility in creating a file, or a directory (if you want
384 * to create a directory, the debugfs_create_dir() function is
385 * recommended to be used instead.)
387 * This function will return a pointer to a dentry if it succeeds. This
388 * pointer must be passed to the debugfs_remove() function when the file is
389 * to be removed (no automatic cleanup happens if your module is unloaded,
390 * you are responsible here.) If an error occurs, %NULL will be returned.
392 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
395 struct dentry *debugfs_create_file(const char *name, umode_t mode,
396 struct dentry *parent, void *data,
397 const struct file_operations *fops)
400 return __debugfs_create_file(name, mode, parent, data,
401 fops ? &debugfs_full_proxy_file_operations :
402 &debugfs_noop_file_operations,
405 EXPORT_SYMBOL_GPL(debugfs_create_file);
408 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
409 * @name: a pointer to a string containing the name of the file to create.
410 * @mode: the permission that the file should have.
411 * @parent: a pointer to the parent dentry for this file. This should be a
412 * directory dentry if set. If this parameter is NULL, then the
413 * file will be created in the root of the debugfs filesystem.
414 * @data: a pointer to something that the caller will want to get to later
415 * on. The inode.i_private pointer will point to this value on
417 * @fops: a pointer to a struct file_operations that should be used for
420 * debugfs_create_file_unsafe() is completely analogous to
421 * debugfs_create_file(), the only difference being that the fops
422 * handed it will not get protected against file removals by the
425 * It is your responsibility to protect your struct file_operation
426 * methods against file removals by means of debugfs_use_file_start()
427 * and debugfs_use_file_finish(). ->open() is still protected by
430 * Any struct file_operations defined by means of
431 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
432 * thus, may be used here.
434 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
435 struct dentry *parent, void *data,
436 const struct file_operations *fops)
439 return __debugfs_create_file(name, mode, parent, data,
440 fops ? &debugfs_open_proxy_file_operations :
441 &debugfs_noop_file_operations,
444 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
447 * debugfs_create_file_size - create a file in the debugfs filesystem
448 * @name: a pointer to a string containing the name of the file to create.
449 * @mode: the permission that the file should have.
450 * @parent: a pointer to the parent dentry for this file. This should be a
451 * directory dentry if set. If this parameter is NULL, then the
452 * file will be created in the root of the debugfs filesystem.
453 * @data: a pointer to something that the caller will want to get to later
454 * on. The inode.i_private pointer will point to this value on
456 * @fops: a pointer to a struct file_operations that should be used for
458 * @file_size: initial file size
460 * This is the basic "create a file" function for debugfs. It allows for a
461 * wide range of flexibility in creating a file, or a directory (if you want
462 * to create a directory, the debugfs_create_dir() function is
463 * recommended to be used instead.)
465 * This function will return a pointer to a dentry if it succeeds. This
466 * pointer must be passed to the debugfs_remove() function when the file is
467 * to be removed (no automatic cleanup happens if your module is unloaded,
468 * you are responsible here.) If an error occurs, %NULL will be returned.
470 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
473 struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
474 struct dentry *parent, void *data,
475 const struct file_operations *fops,
478 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
481 d_inode(de)->i_size = file_size;
484 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
487 * debugfs_create_dir - create a directory in the debugfs filesystem
488 * @name: a pointer to a string containing the name of the directory to
490 * @parent: a pointer to the parent dentry for this file. This should be a
491 * directory dentry if set. If this parameter is NULL, then the
492 * directory will be created in the root of the debugfs filesystem.
494 * This function creates a directory in debugfs with the given name.
496 * This function will return a pointer to a dentry if it succeeds. This
497 * pointer must be passed to the debugfs_remove() function when the file is
498 * to be removed (no automatic cleanup happens if your module is unloaded,
499 * you are responsible here.) If an error occurs, %NULL will be returned.
501 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
504 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
506 struct dentry *dentry = start_creating(name, parent);
512 inode = debugfs_get_inode(dentry->d_sb);
513 if (unlikely(!inode))
514 return failed_creating(dentry);
516 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
517 inode->i_op = &simple_dir_inode_operations;
518 inode->i_fop = &simple_dir_operations;
520 /* directory inodes start off with i_nlink == 2 (for "." entry) */
522 d_instantiate(dentry, inode);
523 inc_nlink(d_inode(dentry->d_parent));
524 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
525 return end_creating(dentry);
527 EXPORT_SYMBOL_GPL(debugfs_create_dir);
530 * debugfs_create_automount - create automount point in the debugfs filesystem
531 * @name: a pointer to a string containing the name of the file to create.
532 * @parent: a pointer to the parent dentry for this file. This should be a
533 * directory dentry if set. If this parameter is NULL, then the
534 * file will be created in the root of the debugfs filesystem.
535 * @f: function to be called when pathname resolution steps on that one.
536 * @data: opaque argument to pass to f().
538 * @f should return what ->d_automount() would.
540 struct dentry *debugfs_create_automount(const char *name,
541 struct dentry *parent,
542 debugfs_automount_t f,
545 struct dentry *dentry = start_creating(name, parent);
551 inode = debugfs_get_inode(dentry->d_sb);
552 if (unlikely(!inode))
553 return failed_creating(dentry);
555 make_empty_dir_inode(inode);
556 inode->i_flags |= S_AUTOMOUNT;
557 inode->i_private = data;
558 dentry->d_fsdata = (void *)f;
559 /* directory inodes start off with i_nlink == 2 (for "." entry) */
561 d_instantiate(dentry, inode);
562 inc_nlink(d_inode(dentry->d_parent));
563 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
564 return end_creating(dentry);
566 EXPORT_SYMBOL(debugfs_create_automount);
569 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
570 * @name: a pointer to a string containing the name of the symbolic link to
572 * @parent: a pointer to the parent dentry for this symbolic link. This
573 * should be a directory dentry if set. If this parameter is NULL,
574 * then the symbolic link will be created in the root of the debugfs
576 * @target: a pointer to a string containing the path to the target of the
579 * This function creates a symbolic link with the given name in debugfs that
580 * links to the given target path.
582 * This function will return a pointer to a dentry if it succeeds. This
583 * pointer must be passed to the debugfs_remove() function when the symbolic
584 * link is to be removed (no automatic cleanup happens if your module is
585 * unloaded, you are responsible here.) If an error occurs, %NULL will be
588 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
591 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
594 struct dentry *dentry;
596 char *link = kstrdup(target, GFP_KERNEL);
600 dentry = start_creating(name, parent);
601 if (IS_ERR(dentry)) {
606 inode = debugfs_get_inode(dentry->d_sb);
607 if (unlikely(!inode)) {
609 return failed_creating(dentry);
611 inode->i_mode = S_IFLNK | S_IRWXUGO;
612 inode->i_op = &simple_symlink_inode_operations;
613 inode->i_link = link;
614 d_instantiate(dentry, inode);
615 return end_creating(dentry);
617 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
619 static void __debugfs_remove_file(struct dentry *dentry, struct dentry *parent)
621 struct debugfs_fsdata *fsd;
623 simple_unlink(d_inode(parent), dentry);
627 * Paired with the closing smp_mb() implied by a successful
628 * cmpxchg() in debugfs_file_get(): either
629 * debugfs_file_get() must see a dead dentry or we must see a
630 * debugfs_fsdata instance at ->d_fsdata here (or both).
633 fsd = READ_ONCE(dentry->d_fsdata);
634 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
636 if (!refcount_dec_and_test(&fsd->active_users))
637 wait_for_completion(&fsd->active_users_drained);
640 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
644 if (simple_positive(dentry)) {
646 if (!d_is_reg(dentry)) {
647 if (d_is_dir(dentry))
648 ret = simple_rmdir(d_inode(parent), dentry);
650 simple_unlink(d_inode(parent), dentry);
654 __debugfs_remove_file(dentry, parent);
662 * debugfs_remove - removes a file or directory from the debugfs filesystem
663 * @dentry: a pointer to a the dentry of the file or directory to be
664 * removed. If this parameter is NULL or an error value, nothing
667 * This function removes a file or directory in debugfs that was previously
668 * created with a call to another debugfs function (like
669 * debugfs_create_file() or variants thereof.)
671 * This function is required to be called in order for the file to be
672 * removed, no automatic cleanup of files will happen when a module is
673 * removed, you are responsible here.
675 void debugfs_remove(struct dentry *dentry)
677 struct dentry *parent;
680 if (IS_ERR_OR_NULL(dentry))
683 parent = dentry->d_parent;
684 inode_lock(d_inode(parent));
685 ret = __debugfs_remove(dentry, parent);
686 inode_unlock(d_inode(parent));
688 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
690 EXPORT_SYMBOL_GPL(debugfs_remove);
693 * debugfs_remove_recursive - recursively removes a directory
694 * @dentry: a pointer to a the dentry of the directory to be removed. If this
695 * parameter is NULL or an error value, nothing will be done.
697 * This function recursively removes a directory tree in debugfs that
698 * was previously created with a call to another debugfs function
699 * (like debugfs_create_file() or variants thereof.)
701 * This function is required to be called in order for the file to be
702 * removed, no automatic cleanup of files will happen when a module is
703 * removed, you are responsible here.
705 void debugfs_remove_recursive(struct dentry *dentry)
707 struct dentry *child, *parent;
709 if (IS_ERR_OR_NULL(dentry))
714 inode_lock(d_inode(parent));
717 * The parent->d_subdirs is protected by the d_lock. Outside that
718 * lock, the child can be unlinked and set to be freed which can
719 * use the d_u.d_child as the rcu head and corrupt this list.
721 spin_lock(&parent->d_lock);
722 list_for_each_entry(child, &parent->d_subdirs, d_child) {
723 if (!simple_positive(child))
726 /* perhaps simple_empty(child) makes more sense */
727 if (!list_empty(&child->d_subdirs)) {
728 spin_unlock(&parent->d_lock);
729 inode_unlock(d_inode(parent));
734 spin_unlock(&parent->d_lock);
736 if (!__debugfs_remove(child, parent))
737 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
740 * The parent->d_lock protects agaist child from unlinking
741 * from d_subdirs. When releasing the parent->d_lock we can
742 * no longer trust that the next pointer is valid.
743 * Restart the loop. We'll skip this one with the
744 * simple_positive() check.
748 spin_unlock(&parent->d_lock);
750 inode_unlock(d_inode(parent));
752 parent = parent->d_parent;
753 inode_lock(d_inode(parent));
759 if (!__debugfs_remove(child, parent))
760 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
761 inode_unlock(d_inode(parent));
763 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
766 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
767 * @name: a pointer to a string containing the name of the item to look up.
768 * @parent: a pointer to the parent dentry of the item.
770 * This is the equlivant of doing something like
771 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
772 * handled for the directory being looked up.
774 void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
776 struct dentry *dentry;
778 dentry = debugfs_lookup(name, parent);
782 debugfs_remove(dentry);
785 EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
788 * debugfs_rename - rename a file/directory in the debugfs filesystem
789 * @old_dir: a pointer to the parent dentry for the renamed object. This
790 * should be a directory dentry.
791 * @old_dentry: dentry of an object to be renamed.
792 * @new_dir: a pointer to the parent dentry where the object should be
793 * moved. This should be a directory dentry.
794 * @new_name: a pointer to a string containing the target name.
796 * This function renames a file/directory in debugfs. The target must not
797 * exist for rename to succeed.
799 * This function will return a pointer to old_dentry (which is updated to
800 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
803 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
806 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
807 struct dentry *new_dir, const char *new_name)
810 struct dentry *dentry = NULL, *trap;
811 struct name_snapshot old_name;
817 if (IS_ERR_OR_NULL(old_dentry))
820 trap = lock_rename(new_dir, old_dir);
821 /* Source or destination directories don't exist? */
822 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
824 /* Source does not exist, cyclic rename, or mountpoint? */
825 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
826 d_mountpoint(old_dentry))
828 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
829 /* Lookup failed, cyclic rename or target exists? */
830 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
833 take_dentry_name_snapshot(&old_name, old_dentry);
835 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
838 release_dentry_name_snapshot(&old_name);
841 d_move(old_dentry, dentry);
842 fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name.name,
843 d_is_dir(old_dentry),
845 release_dentry_name_snapshot(&old_name);
846 unlock_rename(new_dir, old_dir);
850 if (dentry && !IS_ERR(dentry))
852 unlock_rename(new_dir, old_dir);
855 EXPORT_SYMBOL_GPL(debugfs_rename);
858 * debugfs_initialized - Tells whether debugfs has been registered
860 bool debugfs_initialized(void)
862 return debugfs_registered;
864 EXPORT_SYMBOL_GPL(debugfs_initialized);
866 static int __init debugfs_init(void)
870 retval = sysfs_create_mount_point(kernel_kobj, "debug");
874 retval = register_filesystem(&debug_fs_type);
876 sysfs_remove_mount_point(kernel_kobj, "debug");
878 debugfs_registered = true;
882 core_initcall(debugfs_init);