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/DocBook/kernel-api 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 struct tree_descr debug_files[] = {{""}};
208 struct debugfs_fs_info *fsi;
211 save_mount_options(sb, data);
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");
256 static struct dentry *start_creating(const char *name, struct dentry *parent)
258 struct dentry *dentry;
261 pr_debug("debugfs: creating file '%s'\n",name);
266 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
267 &debugfs_mount_count);
269 return ERR_PTR(error);
271 /* If the parent is not specified, we create it in the root.
272 * We need the root dentry to do this, which is in the super
273 * block. A pointer to that is in the struct vfsmount that we
277 parent = debugfs_mount->mnt_root;
279 inode_lock(d_inode(parent));
280 dentry = lookup_one_len(name, parent, strlen(name));
281 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
283 dentry = ERR_PTR(-EEXIST);
286 if (IS_ERR(dentry)) {
287 inode_unlock(d_inode(parent));
288 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
294 static struct dentry *failed_creating(struct dentry *dentry)
296 inode_unlock(d_inode(dentry->d_parent));
298 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
302 static struct dentry *end_creating(struct dentry *dentry)
304 inode_unlock(d_inode(dentry->d_parent));
308 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
309 struct dentry *parent, void *data,
310 const struct file_operations *proxy_fops,
311 const struct file_operations *real_fops)
313 struct dentry *dentry;
316 if (!(mode & S_IFMT))
318 BUG_ON(!S_ISREG(mode));
319 dentry = start_creating(name, parent);
324 inode = debugfs_get_inode(dentry->d_sb);
325 if (unlikely(!inode))
326 return failed_creating(dentry);
328 inode->i_mode = mode;
329 inode->i_private = data;
331 inode->i_fop = proxy_fops;
332 dentry->d_fsdata = (void *)real_fops;
334 d_instantiate(dentry, inode);
335 fsnotify_create(d_inode(dentry->d_parent), dentry);
336 return end_creating(dentry);
340 * debugfs_create_file - create a file in the debugfs filesystem
341 * @name: a pointer to a string containing the name of the file to create.
342 * @mode: the permission that the file should have.
343 * @parent: a pointer to the parent dentry for this file. This should be a
344 * directory dentry if set. If this parameter is NULL, then the
345 * file will be created in the root of the debugfs filesystem.
346 * @data: a pointer to something that the caller will want to get to later
347 * on. The inode.i_private pointer will point to this value on
349 * @fops: a pointer to a struct file_operations that should be used for
352 * This is the basic "create a file" function for debugfs. It allows for a
353 * wide range of flexibility in creating a file, or a directory (if you want
354 * to create a directory, the debugfs_create_dir() function is
355 * recommended to be used instead.)
357 * This function will return a pointer to a dentry if it succeeds. This
358 * pointer must be passed to the debugfs_remove() function when the file is
359 * to be removed (no automatic cleanup happens if your module is unloaded,
360 * you are responsible here.) If an error occurs, %NULL will be returned.
362 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
365 struct dentry *debugfs_create_file(const char *name, umode_t mode,
366 struct dentry *parent, void *data,
367 const struct file_operations *fops)
370 return __debugfs_create_file(name, mode, parent, data,
371 fops ? &debugfs_full_proxy_file_operations :
372 &debugfs_noop_file_operations,
375 EXPORT_SYMBOL_GPL(debugfs_create_file);
378 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
379 * @name: a pointer to a string containing the name of the file to create.
380 * @mode: the permission that the file should have.
381 * @parent: a pointer to the parent dentry for this file. This should be a
382 * directory dentry if set. If this parameter is NULL, then the
383 * file will be created in the root of the debugfs filesystem.
384 * @data: a pointer to something that the caller will want to get to later
385 * on. The inode.i_private pointer will point to this value on
387 * @fops: a pointer to a struct file_operations that should be used for
390 * debugfs_create_file_unsafe() is completely analogous to
391 * debugfs_create_file(), the only difference being that the fops
392 * handed it will not get protected against file removals by the
395 * It is your responsibility to protect your struct file_operation
396 * methods against file removals by means of debugfs_use_file_start()
397 * and debugfs_use_file_finish(). ->open() is still protected by
400 * Any struct file_operations defined by means of
401 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
402 * thus, may be used here.
404 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
405 struct dentry *parent, void *data,
406 const struct file_operations *fops)
409 return __debugfs_create_file(name, mode, parent, data,
410 fops ? &debugfs_open_proxy_file_operations :
411 &debugfs_noop_file_operations,
414 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
417 * debugfs_create_file_size - create a file in the debugfs filesystem
418 * @name: a pointer to a string containing the name of the file to create.
419 * @mode: the permission that the file should have.
420 * @parent: a pointer to the parent dentry for this file. This should be a
421 * directory dentry if set. If this parameter is NULL, then the
422 * file will be created in the root of the debugfs filesystem.
423 * @data: a pointer to something that the caller will want to get to later
424 * on. The inode.i_private pointer will point to this value on
426 * @fops: a pointer to a struct file_operations that should be used for
428 * @file_size: initial file size
430 * This is the basic "create a file" function for debugfs. It allows for a
431 * wide range of flexibility in creating a file, or a directory (if you want
432 * to create a directory, the debugfs_create_dir() function is
433 * recommended to be used instead.)
435 * This function will return a pointer to a dentry if it succeeds. This
436 * pointer must be passed to the debugfs_remove() function when the file is
437 * to be removed (no automatic cleanup happens if your module is unloaded,
438 * you are responsible here.) If an error occurs, %NULL will be returned.
440 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
443 struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
444 struct dentry *parent, void *data,
445 const struct file_operations *fops,
448 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
451 d_inode(de)->i_size = file_size;
454 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
457 * debugfs_create_dir - create a directory in the debugfs filesystem
458 * @name: a pointer to a string containing the name of the directory to
460 * @parent: a pointer to the parent dentry for this file. This should be a
461 * directory dentry if set. If this parameter is NULL, then the
462 * directory will be created in the root of the debugfs filesystem.
464 * This function creates a directory in debugfs with the given name.
466 * This function will return a pointer to a dentry if it succeeds. This
467 * pointer must be passed to the debugfs_remove() function when the file is
468 * to be removed (no automatic cleanup happens if your module is unloaded,
469 * you are responsible here.) If an error occurs, %NULL will be returned.
471 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
474 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
476 struct dentry *dentry = start_creating(name, parent);
482 inode = debugfs_get_inode(dentry->d_sb);
483 if (unlikely(!inode))
484 return failed_creating(dentry);
486 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
487 inode->i_op = &simple_dir_inode_operations;
488 inode->i_fop = &simple_dir_operations;
490 /* directory inodes start off with i_nlink == 2 (for "." entry) */
492 d_instantiate(dentry, inode);
493 inc_nlink(d_inode(dentry->d_parent));
494 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
495 return end_creating(dentry);
497 EXPORT_SYMBOL_GPL(debugfs_create_dir);
500 * debugfs_create_automount - create automount point in the debugfs filesystem
501 * @name: a pointer to a string containing the name of the file to create.
502 * @parent: a pointer to the parent dentry for this file. This should be a
503 * directory dentry if set. If this parameter is NULL, then the
504 * file will be created in the root of the debugfs filesystem.
505 * @f: function to be called when pathname resolution steps on that one.
506 * @data: opaque argument to pass to f().
508 * @f should return what ->d_automount() would.
510 struct dentry *debugfs_create_automount(const char *name,
511 struct dentry *parent,
512 debugfs_automount_t f,
515 struct dentry *dentry = start_creating(name, parent);
521 inode = debugfs_get_inode(dentry->d_sb);
522 if (unlikely(!inode))
523 return failed_creating(dentry);
525 make_empty_dir_inode(inode);
526 inode->i_flags |= S_AUTOMOUNT;
527 inode->i_private = data;
528 dentry->d_fsdata = (void *)f;
529 /* directory inodes start off with i_nlink == 2 (for "." entry) */
531 d_instantiate(dentry, inode);
532 inc_nlink(d_inode(dentry->d_parent));
533 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
534 return end_creating(dentry);
536 EXPORT_SYMBOL(debugfs_create_automount);
539 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
540 * @name: a pointer to a string containing the name of the symbolic link to
542 * @parent: a pointer to the parent dentry for this symbolic link. This
543 * should be a directory dentry if set. If this parameter is NULL,
544 * then the symbolic link will be created in the root of the debugfs
546 * @target: a pointer to a string containing the path to the target of the
549 * This function creates a symbolic link with the given name in debugfs that
550 * links to the given target path.
552 * This function will return a pointer to a dentry if it succeeds. This
553 * pointer must be passed to the debugfs_remove() function when the symbolic
554 * link is to be removed (no automatic cleanup happens if your module is
555 * unloaded, you are responsible here.) If an error occurs, %NULL will be
558 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
561 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
564 struct dentry *dentry;
566 char *link = kstrdup(target, GFP_KERNEL);
570 dentry = start_creating(name, parent);
571 if (IS_ERR(dentry)) {
576 inode = debugfs_get_inode(dentry->d_sb);
577 if (unlikely(!inode)) {
579 return failed_creating(dentry);
581 inode->i_mode = S_IFLNK | S_IRWXUGO;
582 inode->i_op = &simple_symlink_inode_operations;
583 inode->i_link = link;
584 d_instantiate(dentry, inode);
585 return end_creating(dentry);
587 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
589 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
593 if (simple_positive(dentry)) {
595 if (d_is_dir(dentry))
596 ret = simple_rmdir(d_inode(parent), dentry);
598 simple_unlink(d_inode(parent), dentry);
607 * debugfs_remove - removes a file or directory from the debugfs filesystem
608 * @dentry: a pointer to a the dentry of the file or directory to be
609 * removed. If this parameter is NULL or an error value, nothing
612 * This function removes a file or directory in debugfs that was previously
613 * created with a call to another debugfs function (like
614 * debugfs_create_file() or variants thereof.)
616 * This function is required to be called in order for the file to be
617 * removed, no automatic cleanup of files will happen when a module is
618 * removed, you are responsible here.
620 void debugfs_remove(struct dentry *dentry)
622 struct dentry *parent;
625 if (IS_ERR_OR_NULL(dentry))
628 parent = dentry->d_parent;
629 inode_lock(d_inode(parent));
630 ret = __debugfs_remove(dentry, parent);
631 inode_unlock(d_inode(parent));
633 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
635 synchronize_srcu(&debugfs_srcu);
637 EXPORT_SYMBOL_GPL(debugfs_remove);
640 * debugfs_remove_recursive - recursively removes a directory
641 * @dentry: a pointer to a the dentry of the directory to be removed. If this
642 * parameter is NULL or an error value, nothing will be done.
644 * This function recursively removes a directory tree in debugfs that
645 * was previously created with a call to another debugfs function
646 * (like debugfs_create_file() or variants thereof.)
648 * This function is required to be called in order for the file to be
649 * removed, no automatic cleanup of files will happen when a module is
650 * removed, you are responsible here.
652 void debugfs_remove_recursive(struct dentry *dentry)
654 struct dentry *child, *parent;
656 if (IS_ERR_OR_NULL(dentry))
661 inode_lock(d_inode(parent));
664 * The parent->d_subdirs is protected by the d_lock. Outside that
665 * lock, the child can be unlinked and set to be freed which can
666 * use the d_u.d_child as the rcu head and corrupt this list.
668 spin_lock(&parent->d_lock);
669 list_for_each_entry(child, &parent->d_subdirs, d_child) {
670 if (!simple_positive(child))
673 /* perhaps simple_empty(child) makes more sense */
674 if (!list_empty(&child->d_subdirs)) {
675 spin_unlock(&parent->d_lock);
676 inode_unlock(d_inode(parent));
681 spin_unlock(&parent->d_lock);
683 if (!__debugfs_remove(child, parent))
684 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
687 * The parent->d_lock protects agaist child from unlinking
688 * from d_subdirs. When releasing the parent->d_lock we can
689 * no longer trust that the next pointer is valid.
690 * Restart the loop. We'll skip this one with the
691 * simple_positive() check.
695 spin_unlock(&parent->d_lock);
697 inode_unlock(d_inode(parent));
699 parent = parent->d_parent;
700 inode_lock(d_inode(parent));
706 if (!__debugfs_remove(child, parent))
707 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
708 inode_unlock(d_inode(parent));
710 synchronize_srcu(&debugfs_srcu);
712 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
715 * debugfs_rename - rename a file/directory in the debugfs filesystem
716 * @old_dir: a pointer to the parent dentry for the renamed object. This
717 * should be a directory dentry.
718 * @old_dentry: dentry of an object to be renamed.
719 * @new_dir: a pointer to the parent dentry where the object should be
720 * moved. This should be a directory dentry.
721 * @new_name: a pointer to a string containing the target name.
723 * This function renames a file/directory in debugfs. The target must not
724 * exist for rename to succeed.
726 * This function will return a pointer to old_dentry (which is updated to
727 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
730 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
733 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
734 struct dentry *new_dir, const char *new_name)
737 struct dentry *dentry = NULL, *trap;
738 struct name_snapshot old_name;
744 if (IS_ERR_OR_NULL(old_dentry))
747 trap = lock_rename(new_dir, old_dir);
748 /* Source or destination directories don't exist? */
749 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
751 /* Source does not exist, cyclic rename, or mountpoint? */
752 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
753 d_mountpoint(old_dentry))
755 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
756 /* Lookup failed, cyclic rename or target exists? */
757 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
760 take_dentry_name_snapshot(&old_name, old_dentry);
762 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
765 release_dentry_name_snapshot(&old_name);
768 d_move(old_dentry, dentry);
769 fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name.name,
770 d_is_dir(old_dentry),
772 release_dentry_name_snapshot(&old_name);
773 unlock_rename(new_dir, old_dir);
777 if (dentry && !IS_ERR(dentry))
779 unlock_rename(new_dir, old_dir);
782 EXPORT_SYMBOL_GPL(debugfs_rename);
785 * debugfs_initialized - Tells whether debugfs has been registered
787 bool debugfs_initialized(void)
789 return debugfs_registered;
791 EXPORT_SYMBOL_GPL(debugfs_initialized);
793 static int __init debugfs_init(void)
797 retval = sysfs_create_mount_point(kernel_kobj, "debug");
801 retval = register_filesystem(&debug_fs_type);
803 sysfs_remove_mount_point(kernel_kobj, "debug");
805 debugfs_registered = true;
809 core_initcall(debugfs_init);