2 * inode.c - part of debugfs, a tiny little debug file system
4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
5 * Copyright (C) 2004 IBM Inc.
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License version
9 * 2 as published by the Free Software Foundation.
11 * debugfs is for people to use instead of /proc or /sys.
12 * See ./Documentation/core-api/kernel-api.rst for more details.
16 #include <linux/module.h>
18 #include <linux/mount.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/parser.h>
28 #include <linux/magic.h>
29 #include <linux/slab.h>
30 #include <linux/srcu.h>
34 #define DEBUGFS_DEFAULT_MODE 0700
36 DEFINE_SRCU(debugfs_srcu);
38 static struct vfsmount *debugfs_mount;
39 static int debugfs_mount_count;
40 static bool debugfs_registered;
42 static struct inode *debugfs_get_inode(struct super_block *sb)
44 struct inode *inode = new_inode(sb);
46 inode->i_ino = get_next_ino();
47 inode->i_atime = inode->i_mtime =
48 inode->i_ctime = current_time(inode);
53 struct debugfs_mount_opts {
66 static const match_table_t tokens = {
69 {Opt_mode, "mode=%o"},
73 struct debugfs_fs_info {
74 struct debugfs_mount_opts mount_opts;
77 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
79 substring_t args[MAX_OPT_ARGS];
86 opts->mode = DEBUGFS_DEFAULT_MODE;
88 while ((p = strsep(&data, ",")) != NULL) {
92 token = match_token(p, tokens, args);
95 if (match_int(&args[0], &option))
97 uid = make_kuid(current_user_ns(), option);
103 if (match_int(&args[0], &option))
105 gid = make_kgid(current_user_ns(), option);
111 if (match_octal(&args[0], &option))
113 opts->mode = option & S_IALLUGO;
116 * We might like to report bad mount options here;
117 * but traditionally debugfs has ignored all mount options
125 static int debugfs_apply_options(struct super_block *sb)
127 struct debugfs_fs_info *fsi = sb->s_fs_info;
128 struct inode *inode = d_inode(sb->s_root);
129 struct debugfs_mount_opts *opts = &fsi->mount_opts;
131 inode->i_mode &= ~S_IALLUGO;
132 inode->i_mode |= opts->mode;
134 inode->i_uid = opts->uid;
135 inode->i_gid = opts->gid;
140 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
143 struct debugfs_fs_info *fsi = sb->s_fs_info;
146 err = debugfs_parse_options(data, &fsi->mount_opts);
150 debugfs_apply_options(sb);
156 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
158 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
159 struct debugfs_mount_opts *opts = &fsi->mount_opts;
161 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
162 seq_printf(m, ",uid=%u",
163 from_kuid_munged(&init_user_ns, opts->uid));
164 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
165 seq_printf(m, ",gid=%u",
166 from_kgid_munged(&init_user_ns, opts->gid));
167 if (opts->mode != DEBUGFS_DEFAULT_MODE)
168 seq_printf(m, ",mode=%o", opts->mode);
173 static void debugfs_i_callback(struct rcu_head *head)
175 struct inode *inode = container_of(head, struct inode, i_rcu);
176 if (S_ISLNK(inode->i_mode))
177 kfree(inode->i_link);
178 free_inode_nonrcu(inode);
181 static void debugfs_destroy_inode(struct inode *inode)
183 call_rcu(&inode->i_rcu, debugfs_i_callback);
186 static const struct super_operations debugfs_super_operations = {
187 .statfs = simple_statfs,
188 .remount_fs = debugfs_remount,
189 .show_options = debugfs_show_options,
190 .destroy_inode = debugfs_destroy_inode,
193 static struct vfsmount *debugfs_automount(struct path *path)
195 debugfs_automount_t f;
196 f = (debugfs_automount_t)path->dentry->d_fsdata;
197 return f(path->dentry, d_inode(path->dentry)->i_private);
200 static const struct dentry_operations debugfs_dops = {
201 .d_delete = always_delete_dentry,
202 .d_automount = debugfs_automount,
205 static int debug_fill_super(struct super_block *sb, void *data, int silent)
207 static const struct tree_descr debug_files[] = {{""}};
208 struct debugfs_fs_info *fsi;
211 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
218 err = debugfs_parse_options(data, &fsi->mount_opts);
222 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
226 sb->s_op = &debugfs_super_operations;
227 sb->s_d_op = &debugfs_dops;
229 debugfs_apply_options(sb);
235 sb->s_fs_info = NULL;
239 static struct dentry *debug_mount(struct file_system_type *fs_type,
240 int flags, const char *dev_name,
243 return mount_single(fs_type, flags, data, debug_fill_super);
246 static struct file_system_type debug_fs_type = {
247 .owner = THIS_MODULE,
249 .mount = debug_mount,
250 .kill_sb = kill_litter_super,
252 MODULE_ALIAS_FS("debugfs");
255 * debugfs_lookup() - look up an existing debugfs file
256 * @name: a pointer to a string containing the name of the file to look up.
257 * @parent: a pointer to the parent dentry of the file.
259 * This function will return a pointer to a dentry if it succeeds. If the file
260 * doesn't exist or an error occurs, %NULL will be returned. The returned
261 * dentry must be passed to dput() when it is no longer needed.
263 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
266 struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
268 struct dentry *dentry;
274 parent = debugfs_mount->mnt_root;
276 inode_lock(d_inode(parent));
277 dentry = lookup_one_len(name, parent, strlen(name));
278 inode_unlock(d_inode(parent));
282 if (!d_really_is_positive(dentry)) {
288 EXPORT_SYMBOL_GPL(debugfs_lookup);
290 static struct dentry *start_creating(const char *name, struct dentry *parent)
292 struct dentry *dentry;
295 pr_debug("debugfs: creating file '%s'\n",name);
300 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
301 &debugfs_mount_count);
303 return ERR_PTR(error);
305 /* If the parent is not specified, we create it in the root.
306 * We need the root dentry to do this, which is in the super
307 * block. A pointer to that is in the struct vfsmount that we
311 parent = debugfs_mount->mnt_root;
313 inode_lock(d_inode(parent));
314 dentry = lookup_one_len(name, parent, strlen(name));
315 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
317 dentry = ERR_PTR(-EEXIST);
320 if (IS_ERR(dentry)) {
321 inode_unlock(d_inode(parent));
322 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
328 static struct dentry *failed_creating(struct dentry *dentry)
330 inode_unlock(d_inode(dentry->d_parent));
332 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
336 static struct dentry *end_creating(struct dentry *dentry)
338 inode_unlock(d_inode(dentry->d_parent));
342 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
343 struct dentry *parent, void *data,
344 const struct file_operations *proxy_fops,
345 const struct file_operations *real_fops)
347 struct dentry *dentry;
350 if (!(mode & S_IFMT))
352 BUG_ON(!S_ISREG(mode));
353 dentry = start_creating(name, parent);
358 inode = debugfs_get_inode(dentry->d_sb);
359 if (unlikely(!inode))
360 return failed_creating(dentry);
362 inode->i_mode = mode;
363 inode->i_private = data;
365 inode->i_fop = proxy_fops;
366 dentry->d_fsdata = (void *)real_fops;
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, %NULL will be returned.
396 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
399 struct dentry *debugfs_create_file(const char *name, umode_t mode,
400 struct dentry *parent, void *data,
401 const struct file_operations *fops)
404 return __debugfs_create_file(name, mode, parent, data,
405 fops ? &debugfs_full_proxy_file_operations :
406 &debugfs_noop_file_operations,
409 EXPORT_SYMBOL_GPL(debugfs_create_file);
412 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
413 * @name: a pointer to a string containing the name of the file to create.
414 * @mode: the permission that the file should have.
415 * @parent: a pointer to the parent dentry for this file. This should be a
416 * directory dentry if set. If this parameter is NULL, then the
417 * file will be created in the root of the debugfs filesystem.
418 * @data: a pointer to something that the caller will want to get to later
419 * on. The inode.i_private pointer will point to this value on
421 * @fops: a pointer to a struct file_operations that should be used for
424 * debugfs_create_file_unsafe() is completely analogous to
425 * debugfs_create_file(), the only difference being that the fops
426 * handed it will not get protected against file removals by the
429 * It is your responsibility to protect your struct file_operation
430 * methods against file removals by means of debugfs_use_file_start()
431 * and debugfs_use_file_finish(). ->open() is still protected by
434 * Any struct file_operations defined by means of
435 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
436 * thus, may be used here.
438 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
439 struct dentry *parent, void *data,
440 const struct file_operations *fops)
443 return __debugfs_create_file(name, mode, parent, data,
444 fops ? &debugfs_open_proxy_file_operations :
445 &debugfs_noop_file_operations,
448 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
451 * debugfs_create_file_size - create a file in the debugfs filesystem
452 * @name: a pointer to a string containing the name of the file to create.
453 * @mode: the permission that the file should have.
454 * @parent: a pointer to the parent dentry for this file. This should be a
455 * directory dentry if set. If this parameter is NULL, then the
456 * file will be created in the root of the debugfs filesystem.
457 * @data: a pointer to something that the caller will want to get to later
458 * on. The inode.i_private pointer will point to this value on
460 * @fops: a pointer to a struct file_operations that should be used for
462 * @file_size: initial file size
464 * This is the basic "create a file" function for debugfs. It allows for a
465 * wide range of flexibility in creating a file, or a directory (if you want
466 * to create a directory, the debugfs_create_dir() function is
467 * recommended to be used instead.)
469 * This function will return a pointer to a dentry if it succeeds. This
470 * pointer must be passed to the debugfs_remove() function when the file is
471 * to be removed (no automatic cleanup happens if your module is unloaded,
472 * you are responsible here.) If an error occurs, %NULL will be returned.
474 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
477 struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
478 struct dentry *parent, void *data,
479 const struct file_operations *fops,
482 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
485 d_inode(de)->i_size = file_size;
488 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
491 * debugfs_create_dir - create a directory in the debugfs filesystem
492 * @name: a pointer to a string containing the name of the directory to
494 * @parent: a pointer to the parent dentry for this file. This should be a
495 * directory dentry if set. If this parameter is NULL, then the
496 * directory will be created in the root of the debugfs filesystem.
498 * This function creates a directory in debugfs with the given name.
500 * This function will return a pointer to a dentry if it succeeds. This
501 * pointer must be passed to the debugfs_remove() function when the file is
502 * to be removed (no automatic cleanup happens if your module is unloaded,
503 * you are responsible here.) If an error occurs, %NULL will be returned.
505 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
508 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
510 struct dentry *dentry = start_creating(name, parent);
516 inode = debugfs_get_inode(dentry->d_sb);
517 if (unlikely(!inode))
518 return failed_creating(dentry);
520 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
521 inode->i_op = &simple_dir_inode_operations;
522 inode->i_fop = &simple_dir_operations;
524 /* directory inodes start off with i_nlink == 2 (for "." entry) */
526 d_instantiate(dentry, inode);
527 inc_nlink(d_inode(dentry->d_parent));
528 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
529 return end_creating(dentry);
531 EXPORT_SYMBOL_GPL(debugfs_create_dir);
534 * debugfs_create_automount - create automount point in the debugfs filesystem
535 * @name: a pointer to a string containing the name of the file to create.
536 * @parent: a pointer to the parent dentry for this file. This should be a
537 * directory dentry if set. If this parameter is NULL, then the
538 * file will be created in the root of the debugfs filesystem.
539 * @f: function to be called when pathname resolution steps on that one.
540 * @data: opaque argument to pass to f().
542 * @f should return what ->d_automount() would.
544 struct dentry *debugfs_create_automount(const char *name,
545 struct dentry *parent,
546 debugfs_automount_t f,
549 struct dentry *dentry = start_creating(name, parent);
555 inode = debugfs_get_inode(dentry->d_sb);
556 if (unlikely(!inode))
557 return failed_creating(dentry);
559 make_empty_dir_inode(inode);
560 inode->i_flags |= S_AUTOMOUNT;
561 inode->i_private = data;
562 dentry->d_fsdata = (void *)f;
563 /* directory inodes start off with i_nlink == 2 (for "." entry) */
565 d_instantiate(dentry, inode);
566 inc_nlink(d_inode(dentry->d_parent));
567 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
568 return end_creating(dentry);
570 EXPORT_SYMBOL(debugfs_create_automount);
573 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
574 * @name: a pointer to a string containing the name of the symbolic link to
576 * @parent: a pointer to the parent dentry for this symbolic link. This
577 * should be a directory dentry if set. If this parameter is NULL,
578 * then the symbolic link will be created in the root of the debugfs
580 * @target: a pointer to a string containing the path to the target of the
583 * This function creates a symbolic link with the given name in debugfs that
584 * links to the given target path.
586 * This function will return a pointer to a dentry if it succeeds. This
587 * pointer must be passed to the debugfs_remove() function when the symbolic
588 * link is to be removed (no automatic cleanup happens if your module is
589 * unloaded, you are responsible here.) If an error occurs, %NULL will be
592 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
595 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
598 struct dentry *dentry;
600 char *link = kstrdup(target, GFP_KERNEL);
604 dentry = start_creating(name, parent);
605 if (IS_ERR(dentry)) {
610 inode = debugfs_get_inode(dentry->d_sb);
611 if (unlikely(!inode)) {
613 return failed_creating(dentry);
615 inode->i_mode = S_IFLNK | S_IRWXUGO;
616 inode->i_op = &simple_symlink_inode_operations;
617 inode->i_link = link;
618 d_instantiate(dentry, inode);
619 return end_creating(dentry);
621 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
623 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
627 if (simple_positive(dentry)) {
629 if (d_is_dir(dentry))
630 ret = simple_rmdir(d_inode(parent), dentry);
632 simple_unlink(d_inode(parent), dentry);
641 * debugfs_remove - removes a file or directory from the debugfs filesystem
642 * @dentry: a pointer to a the dentry of the file or directory to be
643 * removed. If this parameter is NULL or an error value, nothing
646 * This function removes a file or directory in debugfs that was previously
647 * created with a call to another debugfs function (like
648 * debugfs_create_file() or variants thereof.)
650 * This function is required to be called in order for the file to be
651 * removed, no automatic cleanup of files will happen when a module is
652 * removed, you are responsible here.
654 void debugfs_remove(struct dentry *dentry)
656 struct dentry *parent;
659 if (IS_ERR_OR_NULL(dentry))
662 parent = dentry->d_parent;
663 inode_lock(d_inode(parent));
664 ret = __debugfs_remove(dentry, parent);
665 inode_unlock(d_inode(parent));
667 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
669 synchronize_srcu(&debugfs_srcu);
671 EXPORT_SYMBOL_GPL(debugfs_remove);
674 * debugfs_remove_recursive - recursively removes a directory
675 * @dentry: a pointer to a the dentry of the directory to be removed. If this
676 * parameter is NULL or an error value, nothing will be done.
678 * This function recursively removes a directory tree in debugfs that
679 * was previously created with a call to another debugfs function
680 * (like debugfs_create_file() or variants thereof.)
682 * This function is required to be called in order for the file to be
683 * removed, no automatic cleanup of files will happen when a module is
684 * removed, you are responsible here.
686 void debugfs_remove_recursive(struct dentry *dentry)
688 struct dentry *child, *parent;
690 if (IS_ERR_OR_NULL(dentry))
695 inode_lock(d_inode(parent));
698 * The parent->d_subdirs is protected by the d_lock. Outside that
699 * lock, the child can be unlinked and set to be freed which can
700 * use the d_u.d_child as the rcu head and corrupt this list.
702 spin_lock(&parent->d_lock);
703 list_for_each_entry(child, &parent->d_subdirs, d_child) {
704 if (!simple_positive(child))
707 /* perhaps simple_empty(child) makes more sense */
708 if (!list_empty(&child->d_subdirs)) {
709 spin_unlock(&parent->d_lock);
710 inode_unlock(d_inode(parent));
715 spin_unlock(&parent->d_lock);
717 if (!__debugfs_remove(child, parent))
718 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
721 * The parent->d_lock protects agaist child from unlinking
722 * from d_subdirs. When releasing the parent->d_lock we can
723 * no longer trust that the next pointer is valid.
724 * Restart the loop. We'll skip this one with the
725 * simple_positive() check.
729 spin_unlock(&parent->d_lock);
731 inode_unlock(d_inode(parent));
733 parent = parent->d_parent;
734 inode_lock(d_inode(parent));
740 if (!__debugfs_remove(child, parent))
741 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
742 inode_unlock(d_inode(parent));
744 synchronize_srcu(&debugfs_srcu);
746 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
749 * debugfs_rename - rename a file/directory in the debugfs filesystem
750 * @old_dir: a pointer to the parent dentry for the renamed object. This
751 * should be a directory dentry.
752 * @old_dentry: dentry of an object to be renamed.
753 * @new_dir: a pointer to the parent dentry where the object should be
754 * moved. This should be a directory dentry.
755 * @new_name: a pointer to a string containing the target name.
757 * This function renames a file/directory in debugfs. The target must not
758 * exist for rename to succeed.
760 * This function will return a pointer to old_dentry (which is updated to
761 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
764 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
767 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
768 struct dentry *new_dir, const char *new_name)
771 struct dentry *dentry = NULL, *trap;
772 struct name_snapshot old_name;
778 if (IS_ERR_OR_NULL(old_dentry))
781 trap = lock_rename(new_dir, old_dir);
782 /* Source or destination directories don't exist? */
783 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
785 /* Source does not exist, cyclic rename, or mountpoint? */
786 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
787 d_mountpoint(old_dentry))
789 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
790 /* Lookup failed, cyclic rename or target exists? */
791 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
794 take_dentry_name_snapshot(&old_name, old_dentry);
796 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
799 release_dentry_name_snapshot(&old_name);
802 d_move(old_dentry, dentry);
803 fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name.name,
804 d_is_dir(old_dentry),
806 release_dentry_name_snapshot(&old_name);
807 unlock_rename(new_dir, old_dir);
811 if (dentry && !IS_ERR(dentry))
813 unlock_rename(new_dir, old_dir);
816 EXPORT_SYMBOL_GPL(debugfs_rename);
819 * debugfs_initialized - Tells whether debugfs has been registered
821 bool debugfs_initialized(void)
823 return debugfs_registered;
825 EXPORT_SYMBOL_GPL(debugfs_initialized);
827 static int __init debugfs_init(void)
831 retval = sysfs_create_mount_point(kernel_kobj, "debug");
835 retval = register_filesystem(&debug_fs_type);
837 sysfs_remove_mount_point(kernel_kobj, "debug");
839 debugfs_registered = true;
843 core_initcall(debugfs_init);