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_free_inode(struct inode *inode)
168 if (S_ISLNK(inode->i_mode))
169 kfree(inode->i_link);
170 free_inode_nonrcu(inode);
173 static const struct super_operations debugfs_super_operations = {
174 .statfs = simple_statfs,
175 .remount_fs = debugfs_remount,
176 .show_options = debugfs_show_options,
177 .free_inode = debugfs_free_inode,
180 static void debugfs_release_dentry(struct dentry *dentry)
182 void *fsd = dentry->d_fsdata;
184 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
185 kfree(dentry->d_fsdata);
188 static struct vfsmount *debugfs_automount(struct path *path)
190 debugfs_automount_t f;
191 f = (debugfs_automount_t)path->dentry->d_fsdata;
192 return f(path->dentry, d_inode(path->dentry)->i_private);
195 static const struct dentry_operations debugfs_dops = {
196 .d_delete = always_delete_dentry,
197 .d_release = debugfs_release_dentry,
198 .d_automount = debugfs_automount,
201 static int debug_fill_super(struct super_block *sb, void *data, int silent)
203 static const struct tree_descr debug_files[] = {{""}};
204 struct debugfs_fs_info *fsi;
207 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
214 err = debugfs_parse_options(data, &fsi->mount_opts);
218 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
222 sb->s_op = &debugfs_super_operations;
223 sb->s_d_op = &debugfs_dops;
225 debugfs_apply_options(sb);
231 sb->s_fs_info = NULL;
235 static struct dentry *debug_mount(struct file_system_type *fs_type,
236 int flags, const char *dev_name,
239 return mount_single(fs_type, flags, data, debug_fill_super);
242 static struct file_system_type debug_fs_type = {
243 .owner = THIS_MODULE,
245 .mount = debug_mount,
246 .kill_sb = kill_litter_super,
248 MODULE_ALIAS_FS("debugfs");
251 * debugfs_lookup() - look up an existing debugfs file
252 * @name: a pointer to a string containing the name of the file to look up.
253 * @parent: a pointer to the parent dentry of the file.
255 * This function will return a pointer to a dentry if it succeeds. If the file
256 * doesn't exist or an error occurs, %NULL will be returned. The returned
257 * dentry must be passed to dput() when it is no longer needed.
259 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
262 struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
264 struct dentry *dentry;
270 parent = debugfs_mount->mnt_root;
272 dentry = lookup_one_len_unlocked(name, parent, strlen(name));
275 if (!d_really_is_positive(dentry)) {
281 EXPORT_SYMBOL_GPL(debugfs_lookup);
283 static struct dentry *start_creating(const char *name, struct dentry *parent)
285 struct dentry *dentry;
288 pr_debug("debugfs: creating file '%s'\n",name);
293 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
294 &debugfs_mount_count);
296 return ERR_PTR(error);
298 /* If the parent is not specified, we create it in the root.
299 * We need the root dentry to do this, which is in the super
300 * block. A pointer to that is in the struct vfsmount that we
304 parent = debugfs_mount->mnt_root;
306 inode_lock(d_inode(parent));
307 dentry = lookup_one_len(name, parent, strlen(name));
308 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
310 dentry = ERR_PTR(-EEXIST);
313 if (IS_ERR(dentry)) {
314 inode_unlock(d_inode(parent));
315 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
321 static struct dentry *failed_creating(struct dentry *dentry)
323 inode_unlock(d_inode(dentry->d_parent));
325 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
326 return ERR_PTR(-ENOMEM);
329 static struct dentry *end_creating(struct dentry *dentry)
331 inode_unlock(d_inode(dentry->d_parent));
335 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
336 struct dentry *parent, void *data,
337 const struct file_operations *proxy_fops,
338 const struct file_operations *real_fops)
340 struct dentry *dentry;
343 if (!(mode & S_IFMT))
345 BUG_ON(!S_ISREG(mode));
346 dentry = start_creating(name, parent);
351 inode = debugfs_get_inode(dentry->d_sb);
352 if (unlikely(!inode))
353 return failed_creating(dentry);
355 inode->i_mode = mode;
356 inode->i_private = data;
358 inode->i_fop = proxy_fops;
359 dentry->d_fsdata = (void *)((unsigned long)real_fops |
360 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
362 d_instantiate(dentry, inode);
363 fsnotify_create(d_inode(dentry->d_parent), dentry);
364 return end_creating(dentry);
368 * debugfs_create_file - create a file in the debugfs filesystem
369 * @name: a pointer to a string containing the name of the file to create.
370 * @mode: the permission that the file should have.
371 * @parent: a pointer to the parent dentry for this file. This should be a
372 * directory dentry if set. If this parameter is NULL, then the
373 * file will be created in the root of the debugfs filesystem.
374 * @data: a pointer to something that the caller will want to get to later
375 * on. The inode.i_private pointer will point to this value on
377 * @fops: a pointer to a struct file_operations that should be used for
380 * This is the basic "create a file" function for debugfs. It allows for a
381 * wide range of flexibility in creating a file, or a directory (if you want
382 * to create a directory, the debugfs_create_dir() function is
383 * recommended to be used instead.)
385 * This function will return a pointer to a dentry if it succeeds. This
386 * pointer must be passed to the debugfs_remove() function when the file is
387 * to be removed (no automatic cleanup happens if your module is unloaded,
388 * you are responsible here.) If an error occurs, %ERR_PTR(-ERROR) will be
391 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
394 struct dentry *debugfs_create_file(const char *name, umode_t mode,
395 struct dentry *parent, void *data,
396 const struct file_operations *fops)
399 return __debugfs_create_file(name, mode, parent, data,
400 fops ? &debugfs_full_proxy_file_operations :
401 &debugfs_noop_file_operations,
404 EXPORT_SYMBOL_GPL(debugfs_create_file);
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
416 * @fops: a pointer to a struct file_operations that should be used for
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
424 * It is your responsibility to protect your struct file_operation
425 * methods against file removals by means of debugfs_file_get()
426 * and debugfs_file_put(). ->open() is still protected by
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.
433 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
434 struct dentry *parent, void *data,
435 const struct file_operations *fops)
438 return __debugfs_create_file(name, mode, parent, data,
439 fops ? &debugfs_open_proxy_file_operations :
440 &debugfs_noop_file_operations,
443 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
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
455 * @fops: a pointer to a struct file_operations that should be used for
457 * @file_size: initial file size
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.)
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, %ERR_PTR(-ERROR) will be
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, %ERR_PTR(-ERROR) will be
502 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
505 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
507 struct dentry *dentry = start_creating(name, parent);
513 inode = debugfs_get_inode(dentry->d_sb);
514 if (unlikely(!inode))
515 return failed_creating(dentry);
517 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
518 inode->i_op = &simple_dir_inode_operations;
519 inode->i_fop = &simple_dir_operations;
521 /* directory inodes start off with i_nlink == 2 (for "." entry) */
523 d_instantiate(dentry, inode);
524 inc_nlink(d_inode(dentry->d_parent));
525 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
526 return end_creating(dentry);
528 EXPORT_SYMBOL_GPL(debugfs_create_dir);
531 * debugfs_create_automount - create automount point in the debugfs filesystem
532 * @name: a pointer to a string containing the name of the file to create.
533 * @parent: a pointer to the parent dentry for this file. This should be a
534 * directory dentry if set. If this parameter is NULL, then the
535 * file will be created in the root of the debugfs filesystem.
536 * @f: function to be called when pathname resolution steps on that one.
537 * @data: opaque argument to pass to f().
539 * @f should return what ->d_automount() would.
541 struct dentry *debugfs_create_automount(const char *name,
542 struct dentry *parent,
543 debugfs_automount_t f,
546 struct dentry *dentry = start_creating(name, parent);
552 inode = debugfs_get_inode(dentry->d_sb);
553 if (unlikely(!inode))
554 return failed_creating(dentry);
556 make_empty_dir_inode(inode);
557 inode->i_flags |= S_AUTOMOUNT;
558 inode->i_private = data;
559 dentry->d_fsdata = (void *)f;
560 /* directory inodes start off with i_nlink == 2 (for "." entry) */
562 d_instantiate(dentry, inode);
563 inc_nlink(d_inode(dentry->d_parent));
564 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
565 return end_creating(dentry);
567 EXPORT_SYMBOL(debugfs_create_automount);
570 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
571 * @name: a pointer to a string containing the name of the symbolic link to
573 * @parent: a pointer to the parent dentry for this symbolic link. This
574 * should be a directory dentry if set. If this parameter is NULL,
575 * then the symbolic link will be created in the root of the debugfs
577 * @target: a pointer to a string containing the path to the target of the
580 * This function creates a symbolic link with the given name in debugfs that
581 * links to the given target path.
583 * This function will return a pointer to a dentry if it succeeds. This
584 * pointer must be passed to the debugfs_remove() function when the symbolic
585 * link is to be removed (no automatic cleanup happens if your module is
586 * unloaded, you are responsible here.) If an error occurs, %ERR_PTR(-ERROR)
589 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
592 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
595 struct dentry *dentry;
597 char *link = kstrdup(target, GFP_KERNEL);
599 return ERR_PTR(-ENOMEM);
601 dentry = start_creating(name, parent);
602 if (IS_ERR(dentry)) {
607 inode = debugfs_get_inode(dentry->d_sb);
608 if (unlikely(!inode)) {
610 return failed_creating(dentry);
612 inode->i_mode = S_IFLNK | S_IRWXUGO;
613 inode->i_op = &simple_symlink_inode_operations;
614 inode->i_link = link;
615 d_instantiate(dentry, inode);
616 return end_creating(dentry);
618 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
620 static void __debugfs_remove_file(struct dentry *dentry, struct dentry *parent)
622 struct debugfs_fsdata *fsd;
624 simple_unlink(d_inode(parent), dentry);
628 * Paired with the closing smp_mb() implied by a successful
629 * cmpxchg() in debugfs_file_get(): either
630 * debugfs_file_get() must see a dead dentry or we must see a
631 * debugfs_fsdata instance at ->d_fsdata here (or both).
634 fsd = READ_ONCE(dentry->d_fsdata);
635 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
637 if (!refcount_dec_and_test(&fsd->active_users))
638 wait_for_completion(&fsd->active_users_drained);
641 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
645 if (simple_positive(dentry)) {
647 if (!d_is_reg(dentry)) {
648 if (d_is_dir(dentry))
649 ret = simple_rmdir(d_inode(parent), dentry);
651 simple_unlink(d_inode(parent), dentry);
655 __debugfs_remove_file(dentry, parent);
663 * debugfs_remove - removes a file or directory from the debugfs filesystem
664 * @dentry: a pointer to a the dentry of the file or directory to be
665 * removed. If this parameter is NULL or an error value, nothing
668 * This function removes a file or directory in debugfs that was previously
669 * created with a call to another debugfs function (like
670 * debugfs_create_file() or variants thereof.)
672 * This function is required to be called in order for the file to be
673 * removed, no automatic cleanup of files will happen when a module is
674 * removed, you are responsible here.
676 void debugfs_remove(struct dentry *dentry)
678 struct dentry *parent;
681 if (IS_ERR_OR_NULL(dentry))
684 parent = dentry->d_parent;
685 inode_lock(d_inode(parent));
686 ret = __debugfs_remove(dentry, parent);
687 inode_unlock(d_inode(parent));
689 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
691 EXPORT_SYMBOL_GPL(debugfs_remove);
694 * debugfs_remove_recursive - recursively removes a directory
695 * @dentry: a pointer to a the dentry of the directory to be removed. If this
696 * parameter is NULL or an error value, nothing will be done.
698 * This function recursively removes a directory tree in debugfs that
699 * was previously created with a call to another debugfs function
700 * (like debugfs_create_file() or variants thereof.)
702 * This function is required to be called in order for the file to be
703 * removed, no automatic cleanup of files will happen when a module is
704 * removed, you are responsible here.
706 void debugfs_remove_recursive(struct dentry *dentry)
708 struct dentry *child, *parent;
710 if (IS_ERR_OR_NULL(dentry))
715 inode_lock(d_inode(parent));
718 * The parent->d_subdirs is protected by the d_lock. Outside that
719 * lock, the child can be unlinked and set to be freed which can
720 * use the d_u.d_child as the rcu head and corrupt this list.
722 spin_lock(&parent->d_lock);
723 list_for_each_entry(child, &parent->d_subdirs, d_child) {
724 if (!simple_positive(child))
727 /* perhaps simple_empty(child) makes more sense */
728 if (!list_empty(&child->d_subdirs)) {
729 spin_unlock(&parent->d_lock);
730 inode_unlock(d_inode(parent));
735 spin_unlock(&parent->d_lock);
737 if (!__debugfs_remove(child, parent))
738 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
741 * The parent->d_lock protects agaist child from unlinking
742 * from d_subdirs. When releasing the parent->d_lock we can
743 * no longer trust that the next pointer is valid.
744 * Restart the loop. We'll skip this one with the
745 * simple_positive() check.
749 spin_unlock(&parent->d_lock);
751 inode_unlock(d_inode(parent));
753 parent = parent->d_parent;
754 inode_lock(d_inode(parent));
760 if (!__debugfs_remove(child, parent))
761 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
762 inode_unlock(d_inode(parent));
764 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
767 * debugfs_rename - rename a file/directory in the debugfs filesystem
768 * @old_dir: a pointer to the parent dentry for the renamed object. This
769 * should be a directory dentry.
770 * @old_dentry: dentry of an object to be renamed.
771 * @new_dir: a pointer to the parent dentry where the object should be
772 * moved. This should be a directory dentry.
773 * @new_name: a pointer to a string containing the target name.
775 * This function renames a file/directory in debugfs. The target must not
776 * exist for rename to succeed.
778 * This function will return a pointer to old_dentry (which is updated to
779 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
782 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
785 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
786 struct dentry *new_dir, const char *new_name)
789 struct dentry *dentry = NULL, *trap;
790 struct name_snapshot old_name;
796 if (IS_ERR_OR_NULL(old_dentry))
799 trap = lock_rename(new_dir, old_dir);
800 /* Source or destination directories don't exist? */
801 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
803 /* Source does not exist, cyclic rename, or mountpoint? */
804 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
805 d_mountpoint(old_dentry))
807 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
808 /* Lookup failed, cyclic rename or target exists? */
809 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
812 take_dentry_name_snapshot(&old_name, old_dentry);
814 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
817 release_dentry_name_snapshot(&old_name);
820 d_move(old_dentry, dentry);
821 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
822 d_is_dir(old_dentry),
824 release_dentry_name_snapshot(&old_name);
825 unlock_rename(new_dir, old_dir);
829 if (dentry && !IS_ERR(dentry))
831 unlock_rename(new_dir, old_dir);
834 return ERR_PTR(-EINVAL);
836 EXPORT_SYMBOL_GPL(debugfs_rename);
839 * debugfs_initialized - Tells whether debugfs has been registered
841 bool debugfs_initialized(void)
843 return debugfs_registered;
845 EXPORT_SYMBOL_GPL(debugfs_initialized);
847 static int __init debugfs_init(void)
851 retval = sysfs_create_mount_point(kernel_kobj, "debug");
855 retval = register_filesystem(&debug_fs_type);
857 sysfs_remove_mount_point(kernel_kobj, "debug");
859 debugfs_registered = true;
863 core_initcall(debugfs_init);