1 // SPDX-License-Identifier: GPL-2.0
3 * inode.c - part of debugfs, a tiny little debug file system
5 * Copyright (C) 2004,2019 Greg Kroah-Hartman <greg@kroah.com>
6 * Copyright (C) 2004 IBM Inc.
7 * Copyright (C) 2019 Linux Foundation <gregkh@linuxfoundation.org>
9 * debugfs is for people to use instead of /proc or /sys.
10 * See ./Documentation/core-api/kernel-api.rst for more details.
13 #define pr_fmt(fmt) "debugfs: " fmt
15 #include <linux/module.h>
17 #include <linux/mount.h>
18 #include <linux/pagemap.h>
19 #include <linux/init.h>
20 #include <linux/kobject.h>
21 #include <linux/namei.h>
22 #include <linux/debugfs.h>
23 #include <linux/fsnotify.h>
24 #include <linux/string.h>
25 #include <linux/seq_file.h>
26 #include <linux/parser.h>
27 #include <linux/magic.h>
28 #include <linux/slab.h>
29 #include <linux/security.h>
33 #define DEBUGFS_DEFAULT_MODE 0700
35 static struct vfsmount *debugfs_mount;
36 static int debugfs_mount_count;
37 static bool debugfs_registered;
38 static unsigned int debugfs_allow = DEFAULT_DEBUGFS_ALLOW_BITS;
41 * Don't allow access attributes to be changed whilst the kernel is locked down
42 * so that we can use the file mode as part of a heuristic to determine whether
43 * to lock down individual files.
45 static int debugfs_setattr(struct dentry *dentry, struct iattr *ia)
47 int ret = security_locked_down(LOCKDOWN_DEBUGFS);
49 if (ret && (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
51 return simple_setattr(dentry, ia);
54 static const struct inode_operations debugfs_file_inode_operations = {
55 .setattr = debugfs_setattr,
57 static const struct inode_operations debugfs_dir_inode_operations = {
58 .lookup = simple_lookup,
59 .setattr = debugfs_setattr,
61 static const struct inode_operations debugfs_symlink_inode_operations = {
62 .get_link = simple_get_link,
63 .setattr = debugfs_setattr,
66 static struct inode *debugfs_get_inode(struct super_block *sb)
68 struct inode *inode = new_inode(sb);
70 inode->i_ino = get_next_ino();
71 inode->i_atime = inode->i_mtime =
72 inode->i_ctime = current_time(inode);
77 struct debugfs_mount_opts {
90 static const match_table_t tokens = {
93 {Opt_mode, "mode=%o"},
97 struct debugfs_fs_info {
98 struct debugfs_mount_opts mount_opts;
101 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
103 substring_t args[MAX_OPT_ARGS];
110 opts->mode = DEBUGFS_DEFAULT_MODE;
112 while ((p = strsep(&data, ",")) != NULL) {
116 token = match_token(p, tokens, args);
119 if (match_int(&args[0], &option))
121 uid = make_kuid(current_user_ns(), option);
127 if (match_int(&args[0], &option))
129 gid = make_kgid(current_user_ns(), option);
135 if (match_octal(&args[0], &option))
137 opts->mode = option & S_IALLUGO;
140 * We might like to report bad mount options here;
141 * but traditionally debugfs has ignored all mount options
149 static int debugfs_apply_options(struct super_block *sb)
151 struct debugfs_fs_info *fsi = sb->s_fs_info;
152 struct inode *inode = d_inode(sb->s_root);
153 struct debugfs_mount_opts *opts = &fsi->mount_opts;
155 inode->i_mode &= ~S_IALLUGO;
156 inode->i_mode |= opts->mode;
158 inode->i_uid = opts->uid;
159 inode->i_gid = opts->gid;
164 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
167 struct debugfs_fs_info *fsi = sb->s_fs_info;
170 err = debugfs_parse_options(data, &fsi->mount_opts);
174 debugfs_apply_options(sb);
180 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
182 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
183 struct debugfs_mount_opts *opts = &fsi->mount_opts;
185 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
186 seq_printf(m, ",uid=%u",
187 from_kuid_munged(&init_user_ns, opts->uid));
188 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
189 seq_printf(m, ",gid=%u",
190 from_kgid_munged(&init_user_ns, opts->gid));
191 if (opts->mode != DEBUGFS_DEFAULT_MODE)
192 seq_printf(m, ",mode=%o", opts->mode);
197 static void debugfs_free_inode(struct inode *inode)
199 if (S_ISLNK(inode->i_mode))
200 kfree(inode->i_link);
201 free_inode_nonrcu(inode);
204 static const struct super_operations debugfs_super_operations = {
205 .statfs = simple_statfs,
206 .remount_fs = debugfs_remount,
207 .show_options = debugfs_show_options,
208 .free_inode = debugfs_free_inode,
211 static void debugfs_release_dentry(struct dentry *dentry)
213 void *fsd = dentry->d_fsdata;
215 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
216 kfree(dentry->d_fsdata);
219 static struct vfsmount *debugfs_automount(struct path *path)
221 debugfs_automount_t f;
222 f = (debugfs_automount_t)path->dentry->d_fsdata;
223 return f(path->dentry, d_inode(path->dentry)->i_private);
226 static const struct dentry_operations debugfs_dops = {
227 .d_delete = always_delete_dentry,
228 .d_release = debugfs_release_dentry,
229 .d_automount = debugfs_automount,
232 static int debug_fill_super(struct super_block *sb, void *data, int silent)
234 static const struct tree_descr debug_files[] = {{""}};
235 struct debugfs_fs_info *fsi;
238 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
245 err = debugfs_parse_options(data, &fsi->mount_opts);
249 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
253 sb->s_op = &debugfs_super_operations;
254 sb->s_d_op = &debugfs_dops;
256 debugfs_apply_options(sb);
262 sb->s_fs_info = NULL;
266 static struct dentry *debug_mount(struct file_system_type *fs_type,
267 int flags, const char *dev_name,
270 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
271 return ERR_PTR(-EPERM);
273 return mount_single(fs_type, flags, data, debug_fill_super);
276 static struct file_system_type debug_fs_type = {
277 .owner = THIS_MODULE,
279 .mount = debug_mount,
280 .kill_sb = kill_litter_super,
282 MODULE_ALIAS_FS("debugfs");
285 * debugfs_lookup() - look up an existing debugfs file
286 * @name: a pointer to a string containing the name of the file to look up.
287 * @parent: a pointer to the parent dentry of the file.
289 * This function will return a pointer to a dentry if it succeeds. If the file
290 * doesn't exist or an error occurs, %NULL will be returned. The returned
291 * dentry must be passed to dput() when it is no longer needed.
293 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
296 struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
298 struct dentry *dentry;
304 parent = debugfs_mount->mnt_root;
306 dentry = lookup_positive_unlocked(name, parent, strlen(name));
311 EXPORT_SYMBOL_GPL(debugfs_lookup);
313 static struct dentry *start_creating(const char *name, struct dentry *parent)
315 struct dentry *dentry;
318 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
319 return ERR_PTR(-EPERM);
321 pr_debug("creating file '%s'\n", name);
326 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
327 &debugfs_mount_count);
329 pr_err("Unable to pin filesystem for file '%s'\n", name);
330 return ERR_PTR(error);
333 /* If the parent is not specified, we create it in the root.
334 * We need the root dentry to do this, which is in the super
335 * block. A pointer to that is in the struct vfsmount that we
339 parent = debugfs_mount->mnt_root;
341 inode_lock(d_inode(parent));
342 if (unlikely(IS_DEADDIR(d_inode(parent))))
343 dentry = ERR_PTR(-ENOENT);
345 dentry = lookup_one_len(name, parent, strlen(name));
346 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
347 if (d_is_dir(dentry))
348 pr_err("Directory '%s' with parent '%s' already present!\n",
349 name, parent->d_name.name);
351 pr_err("File '%s' in directory '%s' already present!\n",
352 name, parent->d_name.name);
354 dentry = ERR_PTR(-EEXIST);
357 if (IS_ERR(dentry)) {
358 inode_unlock(d_inode(parent));
359 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
365 static struct dentry *failed_creating(struct dentry *dentry)
367 inode_unlock(d_inode(dentry->d_parent));
369 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
370 return ERR_PTR(-ENOMEM);
373 static struct dentry *end_creating(struct dentry *dentry)
375 inode_unlock(d_inode(dentry->d_parent));
379 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
380 struct dentry *parent, void *data,
381 const struct file_operations *proxy_fops,
382 const struct file_operations *real_fops)
384 struct dentry *dentry;
387 if (!(mode & S_IFMT))
389 BUG_ON(!S_ISREG(mode));
390 dentry = start_creating(name, parent);
395 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
396 failed_creating(dentry);
397 return ERR_PTR(-EPERM);
400 inode = debugfs_get_inode(dentry->d_sb);
401 if (unlikely(!inode)) {
402 pr_err("out of free dentries, can not create file '%s'\n",
404 return failed_creating(dentry);
407 inode->i_mode = mode;
408 inode->i_private = data;
410 inode->i_op = &debugfs_file_inode_operations;
411 inode->i_fop = proxy_fops;
412 dentry->d_fsdata = (void *)((unsigned long)real_fops |
413 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
415 d_instantiate(dentry, inode);
416 fsnotify_create(d_inode(dentry->d_parent), dentry);
417 return end_creating(dentry);
421 * debugfs_create_file - create a file in the debugfs filesystem
422 * @name: a pointer to a string containing the name of the file to create.
423 * @mode: the permission that the file should have.
424 * @parent: a pointer to the parent dentry for this file. This should be a
425 * directory dentry if set. If this parameter is NULL, then the
426 * file will be created in the root of the debugfs filesystem.
427 * @data: a pointer to something that the caller will want to get to later
428 * on. The inode.i_private pointer will point to this value on
430 * @fops: a pointer to a struct file_operations that should be used for
433 * This is the basic "create a file" function for debugfs. It allows for a
434 * wide range of flexibility in creating a file, or a directory (if you want
435 * to create a directory, the debugfs_create_dir() function is
436 * recommended to be used instead.)
438 * This function will return a pointer to a dentry if it succeeds. This
439 * pointer must be passed to the debugfs_remove() function when the file is
440 * to be removed (no automatic cleanup happens if your module is unloaded,
441 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
444 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
447 struct dentry *debugfs_create_file(const char *name, umode_t mode,
448 struct dentry *parent, void *data,
449 const struct file_operations *fops)
452 return __debugfs_create_file(name, mode, parent, data,
453 fops ? &debugfs_full_proxy_file_operations :
454 &debugfs_noop_file_operations,
457 EXPORT_SYMBOL_GPL(debugfs_create_file);
460 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
461 * @name: a pointer to a string containing the name of the file to create.
462 * @mode: the permission that the file should have.
463 * @parent: a pointer to the parent dentry for this file. This should be a
464 * directory dentry if set. If this parameter is NULL, then the
465 * file will be created in the root of the debugfs filesystem.
466 * @data: a pointer to something that the caller will want to get to later
467 * on. The inode.i_private pointer will point to this value on
469 * @fops: a pointer to a struct file_operations that should be used for
472 * debugfs_create_file_unsafe() is completely analogous to
473 * debugfs_create_file(), the only difference being that the fops
474 * handed it will not get protected against file removals by the
477 * It is your responsibility to protect your struct file_operation
478 * methods against file removals by means of debugfs_file_get()
479 * and debugfs_file_put(). ->open() is still protected by
482 * Any struct file_operations defined by means of
483 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
484 * thus, may be used here.
486 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
487 struct dentry *parent, void *data,
488 const struct file_operations *fops)
491 return __debugfs_create_file(name, mode, parent, data,
492 fops ? &debugfs_open_proxy_file_operations :
493 &debugfs_noop_file_operations,
496 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
499 * debugfs_create_file_size - create a file in the debugfs filesystem
500 * @name: a pointer to a string containing the name of the file to create.
501 * @mode: the permission that the file should have.
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 * @data: a pointer to something that the caller will want to get to later
506 * on. The inode.i_private pointer will point to this value on
508 * @fops: a pointer to a struct file_operations that should be used for
510 * @file_size: initial file size
512 * This is the basic "create a file" function for debugfs. It allows for a
513 * wide range of flexibility in creating a file, or a directory (if you want
514 * to create a directory, the debugfs_create_dir() function is
515 * recommended to be used instead.)
517 void debugfs_create_file_size(const char *name, umode_t mode,
518 struct dentry *parent, void *data,
519 const struct file_operations *fops,
522 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
525 d_inode(de)->i_size = file_size;
527 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
530 * debugfs_create_dir - create a directory in the debugfs filesystem
531 * @name: a pointer to a string containing the name of the directory to
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 * directory will be created in the root of the debugfs filesystem.
537 * This function creates a directory in debugfs with the given name.
539 * This function will return a pointer to a dentry if it succeeds. This
540 * pointer must be passed to the debugfs_remove() function when the file is
541 * to be removed (no automatic cleanup happens if your module is unloaded,
542 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
545 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
548 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
550 struct dentry *dentry = start_creating(name, parent);
556 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
557 failed_creating(dentry);
558 return ERR_PTR(-EPERM);
561 inode = debugfs_get_inode(dentry->d_sb);
562 if (unlikely(!inode)) {
563 pr_err("out of free dentries, can not create directory '%s'\n",
565 return failed_creating(dentry);
568 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
569 inode->i_op = &debugfs_dir_inode_operations;
570 inode->i_fop = &simple_dir_operations;
572 /* directory inodes start off with i_nlink == 2 (for "." entry) */
574 d_instantiate(dentry, inode);
575 inc_nlink(d_inode(dentry->d_parent));
576 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
577 return end_creating(dentry);
579 EXPORT_SYMBOL_GPL(debugfs_create_dir);
582 * debugfs_create_automount - create automount point in the debugfs filesystem
583 * @name: a pointer to a string containing the name of the file to create.
584 * @parent: a pointer to the parent dentry for this file. This should be a
585 * directory dentry if set. If this parameter is NULL, then the
586 * file will be created in the root of the debugfs filesystem.
587 * @f: function to be called when pathname resolution steps on that one.
588 * @data: opaque argument to pass to f().
590 * @f should return what ->d_automount() would.
592 struct dentry *debugfs_create_automount(const char *name,
593 struct dentry *parent,
594 debugfs_automount_t f,
597 struct dentry *dentry = start_creating(name, parent);
603 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
604 failed_creating(dentry);
605 return ERR_PTR(-EPERM);
608 inode = debugfs_get_inode(dentry->d_sb);
609 if (unlikely(!inode)) {
610 pr_err("out of free dentries, can not create automount '%s'\n",
612 return failed_creating(dentry);
615 make_empty_dir_inode(inode);
616 inode->i_flags |= S_AUTOMOUNT;
617 inode->i_private = data;
618 dentry->d_fsdata = (void *)f;
619 /* directory inodes start off with i_nlink == 2 (for "." entry) */
621 d_instantiate(dentry, inode);
622 inc_nlink(d_inode(dentry->d_parent));
623 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
624 return end_creating(dentry);
626 EXPORT_SYMBOL(debugfs_create_automount);
629 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
630 * @name: a pointer to a string containing the name of the symbolic link to
632 * @parent: a pointer to the parent dentry for this symbolic link. This
633 * should be a directory dentry if set. If this parameter is NULL,
634 * then the symbolic link will be created in the root of the debugfs
636 * @target: a pointer to a string containing the path to the target of the
639 * This function creates a symbolic link with the given name in debugfs that
640 * links to the given target path.
642 * This function will return a pointer to a dentry if it succeeds. This
643 * pointer must be passed to the debugfs_remove() function when the symbolic
644 * link is to be removed (no automatic cleanup happens if your module is
645 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
648 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
651 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
654 struct dentry *dentry;
656 char *link = kstrdup(target, GFP_KERNEL);
658 return ERR_PTR(-ENOMEM);
660 dentry = start_creating(name, parent);
661 if (IS_ERR(dentry)) {
666 inode = debugfs_get_inode(dentry->d_sb);
667 if (unlikely(!inode)) {
668 pr_err("out of free dentries, can not create symlink '%s'\n",
671 return failed_creating(dentry);
673 inode->i_mode = S_IFLNK | S_IRWXUGO;
674 inode->i_op = &debugfs_symlink_inode_operations;
675 inode->i_link = link;
676 d_instantiate(dentry, inode);
677 return end_creating(dentry);
679 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
681 static void __debugfs_file_removed(struct dentry *dentry)
683 struct debugfs_fsdata *fsd;
686 * Paired with the closing smp_mb() implied by a successful
687 * cmpxchg() in debugfs_file_get(): either
688 * debugfs_file_get() must see a dead dentry or we must see a
689 * debugfs_fsdata instance at ->d_fsdata here (or both).
692 fsd = READ_ONCE(dentry->d_fsdata);
693 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
695 if (!refcount_dec_and_test(&fsd->active_users))
696 wait_for_completion(&fsd->active_users_drained);
699 static void remove_one(struct dentry *victim)
701 if (d_is_reg(victim))
702 __debugfs_file_removed(victim);
703 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
707 * debugfs_remove - recursively removes a directory
708 * @dentry: a pointer to a the dentry of the directory to be removed. If this
709 * parameter is NULL or an error value, nothing will be done.
711 * This function recursively removes a directory tree in debugfs that
712 * was previously created with a call to another debugfs function
713 * (like debugfs_create_file() or variants thereof.)
715 * This function is required to be called in order for the file to be
716 * removed, no automatic cleanup of files will happen when a module is
717 * removed, you are responsible here.
719 void debugfs_remove(struct dentry *dentry)
721 if (IS_ERR_OR_NULL(dentry))
724 simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
725 simple_recursive_removal(dentry, remove_one);
726 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
728 EXPORT_SYMBOL_GPL(debugfs_remove);
731 * debugfs_rename - rename a file/directory in the debugfs filesystem
732 * @old_dir: a pointer to the parent dentry for the renamed object. This
733 * should be a directory dentry.
734 * @old_dentry: dentry of an object to be renamed.
735 * @new_dir: a pointer to the parent dentry where the object should be
736 * moved. This should be a directory dentry.
737 * @new_name: a pointer to a string containing the target name.
739 * This function renames a file/directory in debugfs. The target must not
740 * exist for rename to succeed.
742 * This function will return a pointer to old_dentry (which is updated to
743 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
746 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
749 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
750 struct dentry *new_dir, const char *new_name)
753 struct dentry *dentry = NULL, *trap;
754 struct name_snapshot old_name;
760 if (IS_ERR_OR_NULL(old_dentry))
763 trap = lock_rename(new_dir, old_dir);
764 /* Source or destination directories don't exist? */
765 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
767 /* Source does not exist, cyclic rename, or mountpoint? */
768 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
769 d_mountpoint(old_dentry))
771 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
772 /* Lookup failed, cyclic rename or target exists? */
773 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
776 take_dentry_name_snapshot(&old_name, old_dentry);
778 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
781 release_dentry_name_snapshot(&old_name);
784 d_move(old_dentry, dentry);
785 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
786 d_is_dir(old_dentry),
788 release_dentry_name_snapshot(&old_name);
789 unlock_rename(new_dir, old_dir);
793 if (dentry && !IS_ERR(dentry))
795 unlock_rename(new_dir, old_dir);
798 return ERR_PTR(-EINVAL);
800 EXPORT_SYMBOL_GPL(debugfs_rename);
803 * debugfs_initialized - Tells whether debugfs has been registered
805 bool debugfs_initialized(void)
807 return debugfs_registered;
809 EXPORT_SYMBOL_GPL(debugfs_initialized);
811 static int __init debugfs_kernel(char *str)
814 if (!strcmp(str, "on"))
815 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
816 else if (!strcmp(str, "no-mount"))
817 debugfs_allow = DEBUGFS_ALLOW_API;
818 else if (!strcmp(str, "off"))
824 early_param("debugfs", debugfs_kernel);
825 static int __init debugfs_init(void)
829 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
832 retval = sysfs_create_mount_point(kernel_kobj, "debug");
836 retval = register_filesystem(&debug_fs_type);
838 sysfs_remove_mount_point(kernel_kobj, "debug");
840 debugfs_registered = true;
844 core_initcall(debugfs_init);