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_one_len_unlocked(name, parent, strlen(name));
281 if (!d_really_is_positive(dentry)) {
287 EXPORT_SYMBOL_GPL(debugfs_lookup);
289 static struct dentry *start_creating(const char *name, struct dentry *parent)
291 struct dentry *dentry;
294 pr_debug("debugfs: creating file '%s'\n",name);
299 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
300 &debugfs_mount_count);
302 return ERR_PTR(error);
304 /* If the parent is not specified, we create it in the root.
305 * We need the root dentry to do this, which is in the super
306 * block. A pointer to that is in the struct vfsmount that we
310 parent = debugfs_mount->mnt_root;
312 inode_lock(d_inode(parent));
313 dentry = lookup_one_len(name, parent, strlen(name));
314 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
316 dentry = ERR_PTR(-EEXIST);
319 if (IS_ERR(dentry)) {
320 inode_unlock(d_inode(parent));
321 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
327 static struct dentry *failed_creating(struct dentry *dentry)
329 inode_unlock(d_inode(dentry->d_parent));
331 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
332 return ERR_PTR(-ENOMEM);
335 static struct dentry *end_creating(struct dentry *dentry)
337 inode_unlock(d_inode(dentry->d_parent));
341 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
342 struct dentry *parent, void *data,
343 const struct file_operations *proxy_fops,
344 const struct file_operations *real_fops)
346 struct dentry *dentry;
349 if (!(mode & S_IFMT))
351 BUG_ON(!S_ISREG(mode));
352 dentry = start_creating(name, parent);
357 inode = debugfs_get_inode(dentry->d_sb);
358 if (unlikely(!inode))
359 return failed_creating(dentry);
361 inode->i_mode = mode;
362 inode->i_private = data;
364 inode->i_fop = proxy_fops;
365 dentry->d_fsdata = (void *)((unsigned long)real_fops |
366 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
368 d_instantiate(dentry, inode);
369 fsnotify_create(d_inode(dentry->d_parent), dentry);
370 return end_creating(dentry);
374 * debugfs_create_file - create a file in the debugfs filesystem
375 * @name: a pointer to a string containing the name of the file to create.
376 * @mode: the permission that the file should have.
377 * @parent: a pointer to the parent dentry for this file. This should be a
378 * directory dentry if set. If this parameter is NULL, then the
379 * file will be created in the root of the debugfs filesystem.
380 * @data: a pointer to something that the caller will want to get to later
381 * on. The inode.i_private pointer will point to this value on
383 * @fops: a pointer to a struct file_operations that should be used for
386 * This is the basic "create a file" function for debugfs. It allows for a
387 * wide range of flexibility in creating a file, or a directory (if you want
388 * to create a directory, the debugfs_create_dir() function is
389 * recommended to be used instead.)
391 * This function will return a pointer to a dentry if it succeeds. This
392 * pointer must be passed to the debugfs_remove() function when the file is
393 * to be removed (no automatic cleanup happens if your module is unloaded,
394 * you are responsible here.) If an error occurs, %ERR_PTR(-ERROR) will be
397 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
400 struct dentry *debugfs_create_file(const char *name, umode_t mode,
401 struct dentry *parent, void *data,
402 const struct file_operations *fops)
405 return __debugfs_create_file(name, mode, parent, data,
406 fops ? &debugfs_full_proxy_file_operations :
407 &debugfs_noop_file_operations,
410 EXPORT_SYMBOL_GPL(debugfs_create_file);
413 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
414 * @name: a pointer to a string containing the name of the file to create.
415 * @mode: the permission that the file should have.
416 * @parent: a pointer to the parent dentry for this file. This should be a
417 * directory dentry if set. If this parameter is NULL, then the
418 * file will be created in the root of the debugfs filesystem.
419 * @data: a pointer to something that the caller will want to get to later
420 * on. The inode.i_private pointer will point to this value on
422 * @fops: a pointer to a struct file_operations that should be used for
425 * debugfs_create_file_unsafe() is completely analogous to
426 * debugfs_create_file(), the only difference being that the fops
427 * handed it will not get protected against file removals by the
430 * It is your responsibility to protect your struct file_operation
431 * methods against file removals by means of debugfs_file_get()
432 * and debugfs_file_put(). ->open() is still protected by
435 * Any struct file_operations defined by means of
436 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
437 * thus, may be used here.
439 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
440 struct dentry *parent, void *data,
441 const struct file_operations *fops)
444 return __debugfs_create_file(name, mode, parent, data,
445 fops ? &debugfs_open_proxy_file_operations :
446 &debugfs_noop_file_operations,
449 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
452 * debugfs_create_file_size - create a file in the debugfs filesystem
453 * @name: a pointer to a string containing the name of the file to create.
454 * @mode: the permission that the file should have.
455 * @parent: a pointer to the parent dentry for this file. This should be a
456 * directory dentry if set. If this parameter is NULL, then the
457 * file will be created in the root of the debugfs filesystem.
458 * @data: a pointer to something that the caller will want to get to later
459 * on. The inode.i_private pointer will point to this value on
461 * @fops: a pointer to a struct file_operations that should be used for
463 * @file_size: initial file size
465 * This is the basic "create a file" function for debugfs. It allows for a
466 * wide range of flexibility in creating a file, or a directory (if you want
467 * to create a directory, the debugfs_create_dir() function is
468 * recommended to be used instead.)
470 * This function will return a pointer to a dentry if it succeeds. This
471 * pointer must be passed to the debugfs_remove() function when the file is
472 * to be removed (no automatic cleanup happens if your module is unloaded,
473 * you are responsible here.) If an error occurs, %ERR_PTR(-ERROR) will be
476 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
479 struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
480 struct dentry *parent, void *data,
481 const struct file_operations *fops,
484 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
487 d_inode(de)->i_size = file_size;
490 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
493 * debugfs_create_dir - create a directory in the debugfs filesystem
494 * @name: a pointer to a string containing the name of the directory to
496 * @parent: a pointer to the parent dentry for this file. This should be a
497 * directory dentry if set. If this parameter is NULL, then the
498 * directory will be created in the root of the debugfs filesystem.
500 * This function creates a directory in debugfs with the given name.
502 * This function will return a pointer to a dentry if it succeeds. This
503 * pointer must be passed to the debugfs_remove() function when the file is
504 * to be removed (no automatic cleanup happens if your module is unloaded,
505 * you are responsible here.) If an error occurs, %ERR_PTR(-ERROR) will be
508 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
511 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
513 struct dentry *dentry = start_creating(name, parent);
519 inode = debugfs_get_inode(dentry->d_sb);
520 if (unlikely(!inode))
521 return failed_creating(dentry);
523 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
524 inode->i_op = &simple_dir_inode_operations;
525 inode->i_fop = &simple_dir_operations;
527 /* directory inodes start off with i_nlink == 2 (for "." entry) */
529 d_instantiate(dentry, inode);
530 inc_nlink(d_inode(dentry->d_parent));
531 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
532 return end_creating(dentry);
534 EXPORT_SYMBOL_GPL(debugfs_create_dir);
537 * debugfs_create_automount - create automount point in the debugfs filesystem
538 * @name: a pointer to a string containing the name of the file to create.
539 * @parent: a pointer to the parent dentry for this file. This should be a
540 * directory dentry if set. If this parameter is NULL, then the
541 * file will be created in the root of the debugfs filesystem.
542 * @f: function to be called when pathname resolution steps on that one.
543 * @data: opaque argument to pass to f().
545 * @f should return what ->d_automount() would.
547 struct dentry *debugfs_create_automount(const char *name,
548 struct dentry *parent,
549 debugfs_automount_t f,
552 struct dentry *dentry = start_creating(name, parent);
558 inode = debugfs_get_inode(dentry->d_sb);
559 if (unlikely(!inode))
560 return failed_creating(dentry);
562 make_empty_dir_inode(inode);
563 inode->i_flags |= S_AUTOMOUNT;
564 inode->i_private = data;
565 dentry->d_fsdata = (void *)f;
566 /* directory inodes start off with i_nlink == 2 (for "." entry) */
568 d_instantiate(dentry, inode);
569 inc_nlink(d_inode(dentry->d_parent));
570 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
571 return end_creating(dentry);
573 EXPORT_SYMBOL(debugfs_create_automount);
576 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
577 * @name: a pointer to a string containing the name of the symbolic link to
579 * @parent: a pointer to the parent dentry for this symbolic link. This
580 * should be a directory dentry if set. If this parameter is NULL,
581 * then the symbolic link will be created in the root of the debugfs
583 * @target: a pointer to a string containing the path to the target of the
586 * This function creates a symbolic link with the given name in debugfs that
587 * links to the given target path.
589 * This function will return a pointer to a dentry if it succeeds. This
590 * pointer must be passed to the debugfs_remove() function when the symbolic
591 * link is to be removed (no automatic cleanup happens if your module is
592 * unloaded, you are responsible here.) If an error occurs, %ERR_PTR(-ERROR)
595 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
598 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
601 struct dentry *dentry;
603 char *link = kstrdup(target, GFP_KERNEL);
605 return ERR_PTR(-ENOMEM);
607 dentry = start_creating(name, parent);
608 if (IS_ERR(dentry)) {
613 inode = debugfs_get_inode(dentry->d_sb);
614 if (unlikely(!inode)) {
616 return failed_creating(dentry);
618 inode->i_mode = S_IFLNK | S_IRWXUGO;
619 inode->i_op = &simple_symlink_inode_operations;
620 inode->i_link = link;
621 d_instantiate(dentry, inode);
622 return end_creating(dentry);
624 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
626 static void __debugfs_remove_file(struct dentry *dentry, struct dentry *parent)
628 struct debugfs_fsdata *fsd;
630 simple_unlink(d_inode(parent), dentry);
634 * Paired with the closing smp_mb() implied by a successful
635 * cmpxchg() in debugfs_file_get(): either
636 * debugfs_file_get() must see a dead dentry or we must see a
637 * debugfs_fsdata instance at ->d_fsdata here (or both).
640 fsd = READ_ONCE(dentry->d_fsdata);
641 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
643 if (!refcount_dec_and_test(&fsd->active_users))
644 wait_for_completion(&fsd->active_users_drained);
647 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
651 if (simple_positive(dentry)) {
653 if (!d_is_reg(dentry)) {
654 if (d_is_dir(dentry))
655 ret = simple_rmdir(d_inode(parent), dentry);
657 simple_unlink(d_inode(parent), dentry);
661 __debugfs_remove_file(dentry, parent);
669 * debugfs_remove - removes a file or directory from the debugfs filesystem
670 * @dentry: a pointer to a the dentry of the file or directory to be
671 * removed. If this parameter is NULL or an error value, nothing
674 * This function removes a file or directory in debugfs that was previously
675 * created with a call to another debugfs function (like
676 * debugfs_create_file() or variants thereof.)
678 * This function is required to be called in order for the file to be
679 * removed, no automatic cleanup of files will happen when a module is
680 * removed, you are responsible here.
682 void debugfs_remove(struct dentry *dentry)
684 struct dentry *parent;
687 if (IS_ERR_OR_NULL(dentry))
690 parent = dentry->d_parent;
691 inode_lock(d_inode(parent));
692 ret = __debugfs_remove(dentry, parent);
693 inode_unlock(d_inode(parent));
695 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
697 EXPORT_SYMBOL_GPL(debugfs_remove);
700 * debugfs_remove_recursive - recursively removes a directory
701 * @dentry: a pointer to a the dentry of the directory to be removed. If this
702 * parameter is NULL or an error value, nothing will be done.
704 * This function recursively removes a directory tree in debugfs that
705 * was previously created with a call to another debugfs function
706 * (like debugfs_create_file() or variants thereof.)
708 * This function is required to be called in order for the file to be
709 * removed, no automatic cleanup of files will happen when a module is
710 * removed, you are responsible here.
712 void debugfs_remove_recursive(struct dentry *dentry)
714 struct dentry *child, *parent;
716 if (IS_ERR_OR_NULL(dentry))
721 inode_lock(d_inode(parent));
724 * The parent->d_subdirs is protected by the d_lock. Outside that
725 * lock, the child can be unlinked and set to be freed which can
726 * use the d_u.d_child as the rcu head and corrupt this list.
728 spin_lock(&parent->d_lock);
729 list_for_each_entry(child, &parent->d_subdirs, d_child) {
730 if (!simple_positive(child))
733 /* perhaps simple_empty(child) makes more sense */
734 if (!list_empty(&child->d_subdirs)) {
735 spin_unlock(&parent->d_lock);
736 inode_unlock(d_inode(parent));
741 spin_unlock(&parent->d_lock);
743 if (!__debugfs_remove(child, parent))
744 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
747 * The parent->d_lock protects agaist child from unlinking
748 * from d_subdirs. When releasing the parent->d_lock we can
749 * no longer trust that the next pointer is valid.
750 * Restart the loop. We'll skip this one with the
751 * simple_positive() check.
755 spin_unlock(&parent->d_lock);
757 inode_unlock(d_inode(parent));
759 parent = parent->d_parent;
760 inode_lock(d_inode(parent));
766 if (!__debugfs_remove(child, parent))
767 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
768 inode_unlock(d_inode(parent));
770 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
773 * debugfs_rename - rename a file/directory in the debugfs filesystem
774 * @old_dir: a pointer to the parent dentry for the renamed object. This
775 * should be a directory dentry.
776 * @old_dentry: dentry of an object to be renamed.
777 * @new_dir: a pointer to the parent dentry where the object should be
778 * moved. This should be a directory dentry.
779 * @new_name: a pointer to a string containing the target name.
781 * This function renames a file/directory in debugfs. The target must not
782 * exist for rename to succeed.
784 * This function will return a pointer to old_dentry (which is updated to
785 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
788 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
791 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
792 struct dentry *new_dir, const char *new_name)
795 struct dentry *dentry = NULL, *trap;
796 struct name_snapshot old_name;
802 if (IS_ERR_OR_NULL(old_dentry))
805 trap = lock_rename(new_dir, old_dir);
806 /* Source or destination directories don't exist? */
807 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
809 /* Source does not exist, cyclic rename, or mountpoint? */
810 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
811 d_mountpoint(old_dentry))
813 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
814 /* Lookup failed, cyclic rename or target exists? */
815 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
818 take_dentry_name_snapshot(&old_name, old_dentry);
820 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
823 release_dentry_name_snapshot(&old_name);
826 d_move(old_dentry, dentry);
827 fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name.name,
828 d_is_dir(old_dentry),
830 release_dentry_name_snapshot(&old_name);
831 unlock_rename(new_dir, old_dir);
835 if (dentry && !IS_ERR(dentry))
837 unlock_rename(new_dir, old_dir);
840 return ERR_PTR(-EINVAL);
842 EXPORT_SYMBOL_GPL(debugfs_rename);
845 * debugfs_initialized - Tells whether debugfs has been registered
847 bool debugfs_initialized(void)
849 return debugfs_registered;
851 EXPORT_SYMBOL_GPL(debugfs_initialized);
853 static int __init debugfs_init(void)
857 retval = sysfs_create_mount_point(kernel_kobj, "debug");
861 retval = register_filesystem(&debug_fs_type);
863 sysfs_remove_mount_point(kernel_kobj, "debug");
865 debugfs_registered = true;
869 core_initcall(debugfs_init);