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1/*
2 * inode.c - part of debugfs, a tiny little debug file system
3 *
4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
5 * Copyright (C) 2004 IBM Inc.
6 *
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.
10 *
11 * debugfs is for people to use instead of /proc or /sys.
12 * See Documentation/DocBook/kernel-api for more details.
13 *
14 */
15
16#include <linux/module.h>
17#include <linux/fs.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
31#define DEBUGFS_DEFAULT_MODE 0700
32
33static struct vfsmount *debugfs_mount;
34static int debugfs_mount_count;
35static bool debugfs_registered;
36
37static struct inode *debugfs_get_inode(struct super_block *sb)
38{
39 struct inode *inode = new_inode(sb);
40 if (inode) {
41 inode->i_ino = get_next_ino();
42 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
43 }
44 return inode;
45}
46
47struct debugfs_mount_opts {
48 kuid_t uid;
49 kgid_t gid;
50 umode_t mode;
51};
52
53enum {
54 Opt_uid,
55 Opt_gid,
56 Opt_mode,
57 Opt_err
58};
59
60static const match_table_t tokens = {
61 {Opt_uid, "uid=%u"},
62 {Opt_gid, "gid=%u"},
63 {Opt_mode, "mode=%o"},
64 {Opt_err, NULL}
65};
66
67struct debugfs_fs_info {
68 struct debugfs_mount_opts mount_opts;
69};
70
71static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
72{
73 substring_t args[MAX_OPT_ARGS];
74 int option;
75 int token;
76 kuid_t uid;
77 kgid_t gid;
78 char *p;
79
80 opts->mode = DEBUGFS_DEFAULT_MODE;
81
82 while ((p = strsep(&data, ",")) != NULL) {
83 if (!*p)
84 continue;
85
86 token = match_token(p, tokens, args);
87 switch (token) {
88 case Opt_uid:
89 if (match_int(&args[0], &option))
90 return -EINVAL;
91 uid = make_kuid(current_user_ns(), option);
92 if (!uid_valid(uid))
93 return -EINVAL;
94 opts->uid = uid;
95 break;
96 case Opt_gid:
97 if (match_int(&args[0], &option))
98 return -EINVAL;
99 gid = make_kgid(current_user_ns(), option);
100 if (!gid_valid(gid))
101 return -EINVAL;
102 opts->gid = gid;
103 break;
104 case Opt_mode:
105 if (match_octal(&args[0], &option))
106 return -EINVAL;
107 opts->mode = option & S_IALLUGO;
108 break;
109 /*
110 * We might like to report bad mount options here;
111 * but traditionally debugfs has ignored all mount options
112 */
113 }
114 }
115
116 return 0;
117}
118
119static int debugfs_apply_options(struct super_block *sb)
120{
121 struct debugfs_fs_info *fsi = sb->s_fs_info;
122 struct inode *inode = d_inode(sb->s_root);
123 struct debugfs_mount_opts *opts = &fsi->mount_opts;
124
125 inode->i_mode &= ~S_IALLUGO;
126 inode->i_mode |= opts->mode;
127
128 inode->i_uid = opts->uid;
129 inode->i_gid = opts->gid;
130
131 return 0;
132}
133
134static int debugfs_remount(struct super_block *sb, int *flags, char *data)
135{
136 int err;
137 struct debugfs_fs_info *fsi = sb->s_fs_info;
138
139 sync_filesystem(sb);
140 err = debugfs_parse_options(data, &fsi->mount_opts);
141 if (err)
142 goto fail;
143
144 debugfs_apply_options(sb);
145
146fail:
147 return err;
148}
149
150static int debugfs_show_options(struct seq_file *m, struct dentry *root)
151{
152 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
153 struct debugfs_mount_opts *opts = &fsi->mount_opts;
154
155 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
156 seq_printf(m, ",uid=%u",
157 from_kuid_munged(&init_user_ns, opts->uid));
158 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
159 seq_printf(m, ",gid=%u",
160 from_kgid_munged(&init_user_ns, opts->gid));
161 if (opts->mode != DEBUGFS_DEFAULT_MODE)
162 seq_printf(m, ",mode=%o", opts->mode);
163
164 return 0;
165}
166
167static void debugfs_evict_inode(struct inode *inode)
168{
169 truncate_inode_pages_final(&inode->i_data);
170 clear_inode(inode);
171 if (S_ISLNK(inode->i_mode))
172 kfree(inode->i_link);
173}
174
175static const struct super_operations debugfs_super_operations = {
176 .statfs = simple_statfs,
177 .remount_fs = debugfs_remount,
178 .show_options = debugfs_show_options,
179 .evict_inode = debugfs_evict_inode,
180};
181
182static struct vfsmount *debugfs_automount(struct path *path)
183{
184 struct vfsmount *(*f)(void *);
185 f = (struct vfsmount *(*)(void *))path->dentry->d_fsdata;
186 return f(d_inode(path->dentry)->i_private);
187}
188
189static const struct dentry_operations debugfs_dops = {
190 .d_delete = always_delete_dentry,
191 .d_automount = debugfs_automount,
192};
193
194static int debug_fill_super(struct super_block *sb, void *data, int silent)
195{
196 static struct tree_descr debug_files[] = {{""}};
197 struct debugfs_fs_info *fsi;
198 int err;
199
200 save_mount_options(sb, data);
201
202 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
203 sb->s_fs_info = fsi;
204 if (!fsi) {
205 err = -ENOMEM;
206 goto fail;
207 }
208
209 err = debugfs_parse_options(data, &fsi->mount_opts);
210 if (err)
211 goto fail;
212
213 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
214 if (err)
215 goto fail;
216
217 sb->s_op = &debugfs_super_operations;
218 sb->s_d_op = &debugfs_dops;
219
220 debugfs_apply_options(sb);
221
222 return 0;
223
224fail:
225 kfree(fsi);
226 sb->s_fs_info = NULL;
227 return err;
228}
229
230static struct dentry *debug_mount(struct file_system_type *fs_type,
231 int flags, const char *dev_name,
232 void *data)
233{
234 return mount_single(fs_type, flags, data, debug_fill_super);
235}
236
237static struct file_system_type debug_fs_type = {
238 .owner = THIS_MODULE,
239 .name = "debugfs",
240 .mount = debug_mount,
241 .kill_sb = kill_litter_super,
242};
243MODULE_ALIAS_FS("debugfs");
244
245static struct dentry *start_creating(const char *name, struct dentry *parent)
246{
247 struct dentry *dentry;
248 int error;
249
250 pr_debug("debugfs: creating file '%s'\n",name);
251
252 if (IS_ERR(parent))
253 return parent;
254
255 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
256 &debugfs_mount_count);
257 if (error)
258 return ERR_PTR(error);
259
260 /* If the parent is not specified, we create it in the root.
261 * We need the root dentry to do this, which is in the super
262 * block. A pointer to that is in the struct vfsmount that we
263 * have around.
264 */
265 if (!parent)
266 parent = debugfs_mount->mnt_root;
267
268 inode_lock(d_inode(parent));
269 dentry = lookup_one_len(name, parent, strlen(name));
270 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
271 dput(dentry);
272 dentry = ERR_PTR(-EEXIST);
273 }
274
275 if (IS_ERR(dentry)) {
276 inode_unlock(d_inode(parent));
277 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
278 }
279
280 return dentry;
281}
282
283static struct dentry *failed_creating(struct dentry *dentry)
284{
285 inode_unlock(d_inode(dentry->d_parent));
286 dput(dentry);
287 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
288 return NULL;
289}
290
291static struct dentry *end_creating(struct dentry *dentry)
292{
293 inode_unlock(d_inode(dentry->d_parent));
294 return dentry;
295}
296
297/**
298 * debugfs_create_file - create a file in the debugfs filesystem
299 * @name: a pointer to a string containing the name of the file to create.
300 * @mode: the permission that the file should have.
301 * @parent: a pointer to the parent dentry for this file. This should be a
302 * directory dentry if set. If this parameter is NULL, then the
303 * file will be created in the root of the debugfs filesystem.
304 * @data: a pointer to something that the caller will want to get to later
305 * on. The inode.i_private pointer will point to this value on
306 * the open() call.
307 * @fops: a pointer to a struct file_operations that should be used for
308 * this file.
309 *
310 * This is the basic "create a file" function for debugfs. It allows for a
311 * wide range of flexibility in creating a file, or a directory (if you want
312 * to create a directory, the debugfs_create_dir() function is
313 * recommended to be used instead.)
314 *
315 * This function will return a pointer to a dentry if it succeeds. This
316 * pointer must be passed to the debugfs_remove() function when the file is
317 * to be removed (no automatic cleanup happens if your module is unloaded,
318 * you are responsible here.) If an error occurs, %NULL will be returned.
319 *
320 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
321 * returned.
322 */
323struct dentry *debugfs_create_file(const char *name, umode_t mode,
324 struct dentry *parent, void *data,
325 const struct file_operations *fops)
326{
327 struct dentry *dentry;
328 struct inode *inode;
329
330 if (!(mode & S_IFMT))
331 mode |= S_IFREG;
332 BUG_ON(!S_ISREG(mode));
333 dentry = start_creating(name, parent);
334
335 if (IS_ERR(dentry))
336 return NULL;
337
338 inode = debugfs_get_inode(dentry->d_sb);
339 if (unlikely(!inode))
340 return failed_creating(dentry);
341
342 inode->i_mode = mode;
343 inode->i_fop = fops ? fops : &debugfs_file_operations;
344 inode->i_private = data;
345 d_instantiate(dentry, inode);
346 fsnotify_create(d_inode(dentry->d_parent), dentry);
347 return end_creating(dentry);
348}
349EXPORT_SYMBOL_GPL(debugfs_create_file);
350
351/**
352 * debugfs_create_file_size - create a file in the debugfs filesystem
353 * @name: a pointer to a string containing the name of the file to create.
354 * @mode: the permission that the file should have.
355 * @parent: a pointer to the parent dentry for this file. This should be a
356 * directory dentry if set. If this parameter is NULL, then the
357 * file will be created in the root of the debugfs filesystem.
358 * @data: a pointer to something that the caller will want to get to later
359 * on. The inode.i_private pointer will point to this value on
360 * the open() call.
361 * @fops: a pointer to a struct file_operations that should be used for
362 * this file.
363 * @file_size: initial file size
364 *
365 * This is the basic "create a file" function for debugfs. It allows for a
366 * wide range of flexibility in creating a file, or a directory (if you want
367 * to create a directory, the debugfs_create_dir() function is
368 * recommended to be used instead.)
369 *
370 * This function will return a pointer to a dentry if it succeeds. This
371 * pointer must be passed to the debugfs_remove() function when the file is
372 * to be removed (no automatic cleanup happens if your module is unloaded,
373 * you are responsible here.) If an error occurs, %NULL will be returned.
374 *
375 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
376 * returned.
377 */
378struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
379 struct dentry *parent, void *data,
380 const struct file_operations *fops,
381 loff_t file_size)
382{
383 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
384
385 if (de)
386 d_inode(de)->i_size = file_size;
387 return de;
388}
389EXPORT_SYMBOL_GPL(debugfs_create_file_size);
390
391/**
392 * debugfs_create_dir - create a directory in the debugfs filesystem
393 * @name: a pointer to a string containing the name of the directory to
394 * create.
395 * @parent: a pointer to the parent dentry for this file. This should be a
396 * directory dentry if set. If this parameter is NULL, then the
397 * directory will be created in the root of the debugfs filesystem.
398 *
399 * This function creates a directory in debugfs with the given name.
400 *
401 * This function will return a pointer to a dentry if it succeeds. This
402 * pointer must be passed to the debugfs_remove() function when the file is
403 * to be removed (no automatic cleanup happens if your module is unloaded,
404 * you are responsible here.) If an error occurs, %NULL will be returned.
405 *
406 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
407 * returned.
408 */
409struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
410{
411 struct dentry *dentry = start_creating(name, parent);
412 struct inode *inode;
413
414 if (IS_ERR(dentry))
415 return NULL;
416
417 inode = debugfs_get_inode(dentry->d_sb);
418 if (unlikely(!inode))
419 return failed_creating(dentry);
420
421 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
422 inode->i_op = &simple_dir_inode_operations;
423 inode->i_fop = &simple_dir_operations;
424
425 /* directory inodes start off with i_nlink == 2 (for "." entry) */
426 inc_nlink(inode);
427 d_instantiate(dentry, inode);
428 inc_nlink(d_inode(dentry->d_parent));
429 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
430 return end_creating(dentry);
431}
432EXPORT_SYMBOL_GPL(debugfs_create_dir);
433
434/**
435 * debugfs_create_automount - create automount point in the debugfs filesystem
436 * @name: a pointer to a string containing the name of the file to create.
437 * @parent: a pointer to the parent dentry for this file. This should be a
438 * directory dentry if set. If this parameter is NULL, then the
439 * file will be created in the root of the debugfs filesystem.
440 * @f: function to be called when pathname resolution steps on that one.
441 * @data: opaque argument to pass to f().
442 *
443 * @f should return what ->d_automount() would.
444 */
445struct dentry *debugfs_create_automount(const char *name,
446 struct dentry *parent,
447 struct vfsmount *(*f)(void *),
448 void *data)
449{
450 struct dentry *dentry = start_creating(name, parent);
451 struct inode *inode;
452
453 if (IS_ERR(dentry))
454 return NULL;
455
456 inode = debugfs_get_inode(dentry->d_sb);
457 if (unlikely(!inode))
458 return failed_creating(dentry);
459
460 make_empty_dir_inode(inode);
461 inode->i_flags |= S_AUTOMOUNT;
462 inode->i_private = data;
463 dentry->d_fsdata = (void *)f;
464 d_instantiate(dentry, inode);
465 return end_creating(dentry);
466}
467EXPORT_SYMBOL(debugfs_create_automount);
468
469/**
470 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
471 * @name: a pointer to a string containing the name of the symbolic link to
472 * create.
473 * @parent: a pointer to the parent dentry for this symbolic link. This
474 * should be a directory dentry if set. If this parameter is NULL,
475 * then the symbolic link will be created in the root of the debugfs
476 * filesystem.
477 * @target: a pointer to a string containing the path to the target of the
478 * symbolic link.
479 *
480 * This function creates a symbolic link with the given name in debugfs that
481 * links to the given target path.
482 *
483 * This function will return a pointer to a dentry if it succeeds. This
484 * pointer must be passed to the debugfs_remove() function when the symbolic
485 * link is to be removed (no automatic cleanup happens if your module is
486 * unloaded, you are responsible here.) If an error occurs, %NULL will be
487 * returned.
488 *
489 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
490 * returned.
491 */
492struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
493 const char *target)
494{
495 struct dentry *dentry;
496 struct inode *inode;
497 char *link = kstrdup(target, GFP_KERNEL);
498 if (!link)
499 return NULL;
500
501 dentry = start_creating(name, parent);
502 if (IS_ERR(dentry)) {
503 kfree(link);
504 return NULL;
505 }
506
507 inode = debugfs_get_inode(dentry->d_sb);
508 if (unlikely(!inode)) {
509 kfree(link);
510 return failed_creating(dentry);
511 }
512 inode->i_mode = S_IFLNK | S_IRWXUGO;
513 inode->i_op = &simple_symlink_inode_operations;
514 inode->i_link = link;
515 d_instantiate(dentry, inode);
516 return end_creating(dentry);
517}
518EXPORT_SYMBOL_GPL(debugfs_create_symlink);
519
520static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
521{
522 int ret = 0;
523
524 if (simple_positive(dentry)) {
525 dget(dentry);
526 if (d_is_dir(dentry))
527 ret = simple_rmdir(d_inode(parent), dentry);
528 else
529 simple_unlink(d_inode(parent), dentry);
530 if (!ret)
531 d_delete(dentry);
532 dput(dentry);
533 }
534 return ret;
535}
536
537/**
538 * debugfs_remove - removes a file or directory from the debugfs filesystem
539 * @dentry: a pointer to a the dentry of the file or directory to be
540 * removed. If this parameter is NULL or an error value, nothing
541 * will be done.
542 *
543 * This function removes a file or directory in debugfs that was previously
544 * created with a call to another debugfs function (like
545 * debugfs_create_file() or variants thereof.)
546 *
547 * This function is required to be called in order for the file to be
548 * removed, no automatic cleanup of files will happen when a module is
549 * removed, you are responsible here.
550 */
551void debugfs_remove(struct dentry *dentry)
552{
553 struct dentry *parent;
554 int ret;
555
556 if (IS_ERR_OR_NULL(dentry))
557 return;
558
559 parent = dentry->d_parent;
560 if (!parent || d_really_is_negative(parent))
561 return;
562
563 inode_lock(d_inode(parent));
564 ret = __debugfs_remove(dentry, parent);
565 inode_unlock(d_inode(parent));
566 if (!ret)
567 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
568}
569EXPORT_SYMBOL_GPL(debugfs_remove);
570
571/**
572 * debugfs_remove_recursive - recursively removes a directory
573 * @dentry: a pointer to a the dentry of the directory to be removed. If this
574 * parameter is NULL or an error value, nothing will be done.
575 *
576 * This function recursively removes a directory tree in debugfs that
577 * was previously created with a call to another debugfs function
578 * (like debugfs_create_file() or variants thereof.)
579 *
580 * This function is required to be called in order for the file to be
581 * removed, no automatic cleanup of files will happen when a module is
582 * removed, you are responsible here.
583 */
584void debugfs_remove_recursive(struct dentry *dentry)
585{
586 struct dentry *child, *parent;
587
588 if (IS_ERR_OR_NULL(dentry))
589 return;
590
591 parent = dentry->d_parent;
592 if (!parent || d_really_is_negative(parent))
593 return;
594
595 parent = dentry;
596 down:
597 inode_lock(d_inode(parent));
598 loop:
599 /*
600 * The parent->d_subdirs is protected by the d_lock. Outside that
601 * lock, the child can be unlinked and set to be freed which can
602 * use the d_u.d_child as the rcu head and corrupt this list.
603 */
604 spin_lock(&parent->d_lock);
605 list_for_each_entry(child, &parent->d_subdirs, d_child) {
606 if (!simple_positive(child))
607 continue;
608
609 /* perhaps simple_empty(child) makes more sense */
610 if (!list_empty(&child->d_subdirs)) {
611 spin_unlock(&parent->d_lock);
612 inode_unlock(d_inode(parent));
613 parent = child;
614 goto down;
615 }
616
617 spin_unlock(&parent->d_lock);
618
619 if (!__debugfs_remove(child, parent))
620 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
621
622 /*
623 * The parent->d_lock protects agaist child from unlinking
624 * from d_subdirs. When releasing the parent->d_lock we can
625 * no longer trust that the next pointer is valid.
626 * Restart the loop. We'll skip this one with the
627 * simple_positive() check.
628 */
629 goto loop;
630 }
631 spin_unlock(&parent->d_lock);
632
633 inode_unlock(d_inode(parent));
634 child = parent;
635 parent = parent->d_parent;
636 inode_lock(d_inode(parent));
637
638 if (child != dentry)
639 /* go up */
640 goto loop;
641
642 if (!__debugfs_remove(child, parent))
643 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
644 inode_unlock(d_inode(parent));
645}
646EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
647
648/**
649 * debugfs_rename - rename a file/directory in the debugfs filesystem
650 * @old_dir: a pointer to the parent dentry for the renamed object. This
651 * should be a directory dentry.
652 * @old_dentry: dentry of an object to be renamed.
653 * @new_dir: a pointer to the parent dentry where the object should be
654 * moved. This should be a directory dentry.
655 * @new_name: a pointer to a string containing the target name.
656 *
657 * This function renames a file/directory in debugfs. The target must not
658 * exist for rename to succeed.
659 *
660 * This function will return a pointer to old_dentry (which is updated to
661 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
662 * returned.
663 *
664 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
665 * returned.
666 */
667struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
668 struct dentry *new_dir, const char *new_name)
669{
670 int error;
671 struct dentry *dentry = NULL, *trap;
672 const char *old_name;
673
674 trap = lock_rename(new_dir, old_dir);
675 /* Source or destination directories don't exist? */
676 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
677 goto exit;
678 /* Source does not exist, cyclic rename, or mountpoint? */
679 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
680 d_mountpoint(old_dentry))
681 goto exit;
682 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
683 /* Lookup failed, cyclic rename or target exists? */
684 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
685 goto exit;
686
687 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
688
689 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
690 dentry);
691 if (error) {
692 fsnotify_oldname_free(old_name);
693 goto exit;
694 }
695 d_move(old_dentry, dentry);
696 fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name,
697 d_is_dir(old_dentry),
698 NULL, old_dentry);
699 fsnotify_oldname_free(old_name);
700 unlock_rename(new_dir, old_dir);
701 dput(dentry);
702 return old_dentry;
703exit:
704 if (dentry && !IS_ERR(dentry))
705 dput(dentry);
706 unlock_rename(new_dir, old_dir);
707 return NULL;
708}
709EXPORT_SYMBOL_GPL(debugfs_rename);
710
711/**
712 * debugfs_initialized - Tells whether debugfs has been registered
713 */
714bool debugfs_initialized(void)
715{
716 return debugfs_registered;
717}
718EXPORT_SYMBOL_GPL(debugfs_initialized);
719
720static int __init debugfs_init(void)
721{
722 int retval;
723
724 retval = sysfs_create_mount_point(kernel_kobj, "debug");
725 if (retval)
726 return retval;
727
728 retval = register_filesystem(&debug_fs_type);
729 if (retval)
730 sysfs_remove_mount_point(kernel_kobj, "debug");
731 else
732 debugfs_registered = true;
733
734 return retval;
735}
736core_initcall(debugfs_init);
737
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * inode.c - part of debugfs, a tiny little debug file system
4 *
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>
8 *
9 * debugfs is for people to use instead of /proc or /sys.
10 * See ./Documentation/core-api/kernel-api.rst for more details.
11 */
12
13#define pr_fmt(fmt) "debugfs: " fmt
14
15#include <linux/module.h>
16#include <linux/fs.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>
30
31#include "internal.h"
32
33#define DEBUGFS_DEFAULT_MODE 0700
34
35static struct vfsmount *debugfs_mount;
36static int debugfs_mount_count;
37static bool debugfs_registered;
38static unsigned int debugfs_allow __ro_after_init = DEFAULT_DEBUGFS_ALLOW_BITS;
39
40/*
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.
44 */
45static int debugfs_setattr(struct mnt_idmap *idmap,
46 struct dentry *dentry, struct iattr *ia)
47{
48 int ret;
49
50 if (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) {
51 ret = security_locked_down(LOCKDOWN_DEBUGFS);
52 if (ret)
53 return ret;
54 }
55 return simple_setattr(&nop_mnt_idmap, dentry, ia);
56}
57
58static const struct inode_operations debugfs_file_inode_operations = {
59 .setattr = debugfs_setattr,
60};
61static const struct inode_operations debugfs_dir_inode_operations = {
62 .lookup = simple_lookup,
63 .setattr = debugfs_setattr,
64};
65static const struct inode_operations debugfs_symlink_inode_operations = {
66 .get_link = simple_get_link,
67 .setattr = debugfs_setattr,
68};
69
70static struct inode *debugfs_get_inode(struct super_block *sb)
71{
72 struct inode *inode = new_inode(sb);
73 if (inode) {
74 inode->i_ino = get_next_ino();
75 simple_inode_init_ts(inode);
76 }
77 return inode;
78}
79
80struct debugfs_mount_opts {
81 kuid_t uid;
82 kgid_t gid;
83 umode_t mode;
84 /* Opt_* bitfield. */
85 unsigned int opts;
86};
87
88enum {
89 Opt_uid,
90 Opt_gid,
91 Opt_mode,
92 Opt_err
93};
94
95static const match_table_t tokens = {
96 {Opt_uid, "uid=%u"},
97 {Opt_gid, "gid=%u"},
98 {Opt_mode, "mode=%o"},
99 {Opt_err, NULL}
100};
101
102struct debugfs_fs_info {
103 struct debugfs_mount_opts mount_opts;
104};
105
106static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
107{
108 substring_t args[MAX_OPT_ARGS];
109 int option;
110 int token;
111 kuid_t uid;
112 kgid_t gid;
113 char *p;
114
115 opts->opts = 0;
116 opts->mode = DEBUGFS_DEFAULT_MODE;
117
118 while ((p = strsep(&data, ",")) != NULL) {
119 if (!*p)
120 continue;
121
122 token = match_token(p, tokens, args);
123 switch (token) {
124 case Opt_uid:
125 if (match_int(&args[0], &option))
126 return -EINVAL;
127 uid = make_kuid(current_user_ns(), option);
128 if (!uid_valid(uid))
129 return -EINVAL;
130 opts->uid = uid;
131 break;
132 case Opt_gid:
133 if (match_int(&args[0], &option))
134 return -EINVAL;
135 gid = make_kgid(current_user_ns(), option);
136 if (!gid_valid(gid))
137 return -EINVAL;
138 opts->gid = gid;
139 break;
140 case Opt_mode:
141 if (match_octal(&args[0], &option))
142 return -EINVAL;
143 opts->mode = option & S_IALLUGO;
144 break;
145 /*
146 * We might like to report bad mount options here;
147 * but traditionally debugfs has ignored all mount options
148 */
149 }
150
151 opts->opts |= BIT(token);
152 }
153
154 return 0;
155}
156
157static void _debugfs_apply_options(struct super_block *sb, bool remount)
158{
159 struct debugfs_fs_info *fsi = sb->s_fs_info;
160 struct inode *inode = d_inode(sb->s_root);
161 struct debugfs_mount_opts *opts = &fsi->mount_opts;
162
163 /*
164 * On remount, only reset mode/uid/gid if they were provided as mount
165 * options.
166 */
167
168 if (!remount || opts->opts & BIT(Opt_mode)) {
169 inode->i_mode &= ~S_IALLUGO;
170 inode->i_mode |= opts->mode;
171 }
172
173 if (!remount || opts->opts & BIT(Opt_uid))
174 inode->i_uid = opts->uid;
175
176 if (!remount || opts->opts & BIT(Opt_gid))
177 inode->i_gid = opts->gid;
178}
179
180static void debugfs_apply_options(struct super_block *sb)
181{
182 _debugfs_apply_options(sb, false);
183}
184
185static void debugfs_apply_options_remount(struct super_block *sb)
186{
187 _debugfs_apply_options(sb, true);
188}
189
190static int debugfs_remount(struct super_block *sb, int *flags, char *data)
191{
192 int err;
193 struct debugfs_fs_info *fsi = sb->s_fs_info;
194
195 sync_filesystem(sb);
196 err = debugfs_parse_options(data, &fsi->mount_opts);
197 if (err)
198 goto fail;
199
200 debugfs_apply_options_remount(sb);
201
202fail:
203 return err;
204}
205
206static int debugfs_show_options(struct seq_file *m, struct dentry *root)
207{
208 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
209 struct debugfs_mount_opts *opts = &fsi->mount_opts;
210
211 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
212 seq_printf(m, ",uid=%u",
213 from_kuid_munged(&init_user_ns, opts->uid));
214 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
215 seq_printf(m, ",gid=%u",
216 from_kgid_munged(&init_user_ns, opts->gid));
217 if (opts->mode != DEBUGFS_DEFAULT_MODE)
218 seq_printf(m, ",mode=%o", opts->mode);
219
220 return 0;
221}
222
223static void debugfs_free_inode(struct inode *inode)
224{
225 if (S_ISLNK(inode->i_mode))
226 kfree(inode->i_link);
227 free_inode_nonrcu(inode);
228}
229
230static const struct super_operations debugfs_super_operations = {
231 .statfs = simple_statfs,
232 .remount_fs = debugfs_remount,
233 .show_options = debugfs_show_options,
234 .free_inode = debugfs_free_inode,
235};
236
237static void debugfs_release_dentry(struct dentry *dentry)
238{
239 struct debugfs_fsdata *fsd = dentry->d_fsdata;
240
241 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
242 return;
243
244 /* check it wasn't a dir (no fsdata) or automount (no real_fops) */
245 if (fsd && fsd->real_fops) {
246 WARN_ON(!list_empty(&fsd->cancellations));
247 mutex_destroy(&fsd->cancellations_mtx);
248 }
249
250 kfree(fsd);
251}
252
253static struct vfsmount *debugfs_automount(struct path *path)
254{
255 struct debugfs_fsdata *fsd = path->dentry->d_fsdata;
256
257 return fsd->automount(path->dentry, d_inode(path->dentry)->i_private);
258}
259
260static const struct dentry_operations debugfs_dops = {
261 .d_delete = always_delete_dentry,
262 .d_release = debugfs_release_dentry,
263 .d_automount = debugfs_automount,
264};
265
266static int debug_fill_super(struct super_block *sb, void *data, int silent)
267{
268 static const struct tree_descr debug_files[] = {{""}};
269 struct debugfs_fs_info *fsi;
270 int err;
271
272 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
273 sb->s_fs_info = fsi;
274 if (!fsi) {
275 err = -ENOMEM;
276 goto fail;
277 }
278
279 err = debugfs_parse_options(data, &fsi->mount_opts);
280 if (err)
281 goto fail;
282
283 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
284 if (err)
285 goto fail;
286
287 sb->s_op = &debugfs_super_operations;
288 sb->s_d_op = &debugfs_dops;
289
290 debugfs_apply_options(sb);
291
292 return 0;
293
294fail:
295 kfree(fsi);
296 sb->s_fs_info = NULL;
297 return err;
298}
299
300static struct dentry *debug_mount(struct file_system_type *fs_type,
301 int flags, const char *dev_name,
302 void *data)
303{
304 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
305 return ERR_PTR(-EPERM);
306
307 return mount_single(fs_type, flags, data, debug_fill_super);
308}
309
310static struct file_system_type debug_fs_type = {
311 .owner = THIS_MODULE,
312 .name = "debugfs",
313 .mount = debug_mount,
314 .kill_sb = kill_litter_super,
315};
316MODULE_ALIAS_FS("debugfs");
317
318/**
319 * debugfs_lookup() - look up an existing debugfs file
320 * @name: a pointer to a string containing the name of the file to look up.
321 * @parent: a pointer to the parent dentry of the file.
322 *
323 * This function will return a pointer to a dentry if it succeeds. If the file
324 * doesn't exist or an error occurs, %NULL will be returned. The returned
325 * dentry must be passed to dput() when it is no longer needed.
326 *
327 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
328 * returned.
329 */
330struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
331{
332 struct dentry *dentry;
333
334 if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
335 return NULL;
336
337 if (!parent)
338 parent = debugfs_mount->mnt_root;
339
340 dentry = lookup_positive_unlocked(name, parent, strlen(name));
341 if (IS_ERR(dentry))
342 return NULL;
343 return dentry;
344}
345EXPORT_SYMBOL_GPL(debugfs_lookup);
346
347static struct dentry *start_creating(const char *name, struct dentry *parent)
348{
349 struct dentry *dentry;
350 int error;
351
352 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
353 return ERR_PTR(-EPERM);
354
355 if (!debugfs_initialized())
356 return ERR_PTR(-ENOENT);
357
358 pr_debug("creating file '%s'\n", name);
359
360 if (IS_ERR(parent))
361 return parent;
362
363 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
364 &debugfs_mount_count);
365 if (error) {
366 pr_err("Unable to pin filesystem for file '%s'\n", name);
367 return ERR_PTR(error);
368 }
369
370 /* If the parent is not specified, we create it in the root.
371 * We need the root dentry to do this, which is in the super
372 * block. A pointer to that is in the struct vfsmount that we
373 * have around.
374 */
375 if (!parent)
376 parent = debugfs_mount->mnt_root;
377
378 inode_lock(d_inode(parent));
379 if (unlikely(IS_DEADDIR(d_inode(parent))))
380 dentry = ERR_PTR(-ENOENT);
381 else
382 dentry = lookup_one_len(name, parent, strlen(name));
383 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
384 if (d_is_dir(dentry))
385 pr_err("Directory '%s' with parent '%s' already present!\n",
386 name, parent->d_name.name);
387 else
388 pr_err("File '%s' in directory '%s' already present!\n",
389 name, parent->d_name.name);
390 dput(dentry);
391 dentry = ERR_PTR(-EEXIST);
392 }
393
394 if (IS_ERR(dentry)) {
395 inode_unlock(d_inode(parent));
396 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
397 }
398
399 return dentry;
400}
401
402static struct dentry *failed_creating(struct dentry *dentry)
403{
404 inode_unlock(d_inode(dentry->d_parent));
405 dput(dentry);
406 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
407 return ERR_PTR(-ENOMEM);
408}
409
410static struct dentry *end_creating(struct dentry *dentry)
411{
412 inode_unlock(d_inode(dentry->d_parent));
413 return dentry;
414}
415
416static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
417 struct dentry *parent, void *data,
418 const struct file_operations *proxy_fops,
419 const struct file_operations *real_fops)
420{
421 struct dentry *dentry;
422 struct inode *inode;
423
424 if (!(mode & S_IFMT))
425 mode |= S_IFREG;
426 BUG_ON(!S_ISREG(mode));
427 dentry = start_creating(name, parent);
428
429 if (IS_ERR(dentry))
430 return dentry;
431
432 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
433 failed_creating(dentry);
434 return ERR_PTR(-EPERM);
435 }
436
437 inode = debugfs_get_inode(dentry->d_sb);
438 if (unlikely(!inode)) {
439 pr_err("out of free dentries, can not create file '%s'\n",
440 name);
441 return failed_creating(dentry);
442 }
443
444 inode->i_mode = mode;
445 inode->i_private = data;
446
447 inode->i_op = &debugfs_file_inode_operations;
448 inode->i_fop = proxy_fops;
449 dentry->d_fsdata = (void *)((unsigned long)real_fops |
450 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
451
452 d_instantiate(dentry, inode);
453 fsnotify_create(d_inode(dentry->d_parent), dentry);
454 return end_creating(dentry);
455}
456
457/**
458 * debugfs_create_file - create a file in the debugfs filesystem
459 * @name: a pointer to a string containing the name of the file to create.
460 * @mode: the permission that the file should have.
461 * @parent: a pointer to the parent dentry for this file. This should be a
462 * directory dentry if set. If this parameter is NULL, then the
463 * file will be created in the root of the debugfs filesystem.
464 * @data: a pointer to something that the caller will want to get to later
465 * on. The inode.i_private pointer will point to this value on
466 * the open() call.
467 * @fops: a pointer to a struct file_operations that should be used for
468 * this file.
469 *
470 * This is the basic "create a file" function for debugfs. It allows for a
471 * wide range of flexibility in creating a file, or a directory (if you want
472 * to create a directory, the debugfs_create_dir() function is
473 * recommended to be used instead.)
474 *
475 * This function will return a pointer to a dentry if it succeeds. This
476 * pointer must be passed to the debugfs_remove() function when the file is
477 * to be removed (no automatic cleanup happens if your module is unloaded,
478 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
479 * returned.
480 *
481 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
482 * returned.
483 *
484 * NOTE: it's expected that most callers should _ignore_ the errors returned
485 * by this function. Other debugfs functions handle the fact that the "dentry"
486 * passed to them could be an error and they don't crash in that case.
487 * Drivers should generally work fine even if debugfs fails to init anyway.
488 */
489struct dentry *debugfs_create_file(const char *name, umode_t mode,
490 struct dentry *parent, void *data,
491 const struct file_operations *fops)
492{
493
494 return __debugfs_create_file(name, mode, parent, data,
495 fops ? &debugfs_full_proxy_file_operations :
496 &debugfs_noop_file_operations,
497 fops);
498}
499EXPORT_SYMBOL_GPL(debugfs_create_file);
500
501/**
502 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
503 * @name: a pointer to a string containing the name of the file to create.
504 * @mode: the permission that the file should have.
505 * @parent: a pointer to the parent dentry for this file. This should be a
506 * directory dentry if set. If this parameter is NULL, then the
507 * file will be created in the root of the debugfs filesystem.
508 * @data: a pointer to something that the caller will want to get to later
509 * on. The inode.i_private pointer will point to this value on
510 * the open() call.
511 * @fops: a pointer to a struct file_operations that should be used for
512 * this file.
513 *
514 * debugfs_create_file_unsafe() is completely analogous to
515 * debugfs_create_file(), the only difference being that the fops
516 * handed it will not get protected against file removals by the
517 * debugfs core.
518 *
519 * It is your responsibility to protect your struct file_operation
520 * methods against file removals by means of debugfs_file_get()
521 * and debugfs_file_put(). ->open() is still protected by
522 * debugfs though.
523 *
524 * Any struct file_operations defined by means of
525 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
526 * thus, may be used here.
527 */
528struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
529 struct dentry *parent, void *data,
530 const struct file_operations *fops)
531{
532
533 return __debugfs_create_file(name, mode, parent, data,
534 fops ? &debugfs_open_proxy_file_operations :
535 &debugfs_noop_file_operations,
536 fops);
537}
538EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
539
540/**
541 * debugfs_create_file_size - create a file in the debugfs filesystem
542 * @name: a pointer to a string containing the name of the file to create.
543 * @mode: the permission that the file should have.
544 * @parent: a pointer to the parent dentry for this file. This should be a
545 * directory dentry if set. If this parameter is NULL, then the
546 * file will be created in the root of the debugfs filesystem.
547 * @data: a pointer to something that the caller will want to get to later
548 * on. The inode.i_private pointer will point to this value on
549 * the open() call.
550 * @fops: a pointer to a struct file_operations that should be used for
551 * this file.
552 * @file_size: initial file size
553 *
554 * This is the basic "create a file" function for debugfs. It allows for a
555 * wide range of flexibility in creating a file, or a directory (if you want
556 * to create a directory, the debugfs_create_dir() function is
557 * recommended to be used instead.)
558 */
559void debugfs_create_file_size(const char *name, umode_t mode,
560 struct dentry *parent, void *data,
561 const struct file_operations *fops,
562 loff_t file_size)
563{
564 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
565
566 if (!IS_ERR(de))
567 d_inode(de)->i_size = file_size;
568}
569EXPORT_SYMBOL_GPL(debugfs_create_file_size);
570
571/**
572 * debugfs_create_dir - create a directory in the debugfs filesystem
573 * @name: a pointer to a string containing the name of the directory to
574 * create.
575 * @parent: a pointer to the parent dentry for this file. This should be a
576 * directory dentry if set. If this parameter is NULL, then the
577 * directory will be created in the root of the debugfs filesystem.
578 *
579 * This function creates a directory in debugfs with the given name.
580 *
581 * This function will return a pointer to a dentry if it succeeds. This
582 * pointer must be passed to the debugfs_remove() function when the file is
583 * to be removed (no automatic cleanup happens if your module is unloaded,
584 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
585 * returned.
586 *
587 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
588 * returned.
589 *
590 * NOTE: it's expected that most callers should _ignore_ the errors returned
591 * by this function. Other debugfs functions handle the fact that the "dentry"
592 * passed to them could be an error and they don't crash in that case.
593 * Drivers should generally work fine even if debugfs fails to init anyway.
594 */
595struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
596{
597 struct dentry *dentry = start_creating(name, parent);
598 struct inode *inode;
599
600 if (IS_ERR(dentry))
601 return dentry;
602
603 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
604 failed_creating(dentry);
605 return ERR_PTR(-EPERM);
606 }
607
608 inode = debugfs_get_inode(dentry->d_sb);
609 if (unlikely(!inode)) {
610 pr_err("out of free dentries, can not create directory '%s'\n",
611 name);
612 return failed_creating(dentry);
613 }
614
615 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
616 inode->i_op = &debugfs_dir_inode_operations;
617 inode->i_fop = &simple_dir_operations;
618
619 /* directory inodes start off with i_nlink == 2 (for "." entry) */
620 inc_nlink(inode);
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);
625}
626EXPORT_SYMBOL_GPL(debugfs_create_dir);
627
628/**
629 * debugfs_create_automount - create automount point in the debugfs filesystem
630 * @name: a pointer to a string containing the name of the file to create.
631 * @parent: a pointer to the parent dentry for this file. This should be a
632 * directory dentry if set. If this parameter is NULL, then the
633 * file will be created in the root of the debugfs filesystem.
634 * @f: function to be called when pathname resolution steps on that one.
635 * @data: opaque argument to pass to f().
636 *
637 * @f should return what ->d_automount() would.
638 */
639struct dentry *debugfs_create_automount(const char *name,
640 struct dentry *parent,
641 debugfs_automount_t f,
642 void *data)
643{
644 struct dentry *dentry = start_creating(name, parent);
645 struct debugfs_fsdata *fsd;
646 struct inode *inode;
647
648 if (IS_ERR(dentry))
649 return dentry;
650
651 fsd = kzalloc(sizeof(*fsd), GFP_KERNEL);
652 if (!fsd) {
653 failed_creating(dentry);
654 return ERR_PTR(-ENOMEM);
655 }
656
657 fsd->automount = f;
658
659 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
660 failed_creating(dentry);
661 kfree(fsd);
662 return ERR_PTR(-EPERM);
663 }
664
665 inode = debugfs_get_inode(dentry->d_sb);
666 if (unlikely(!inode)) {
667 pr_err("out of free dentries, can not create automount '%s'\n",
668 name);
669 kfree(fsd);
670 return failed_creating(dentry);
671 }
672
673 make_empty_dir_inode(inode);
674 inode->i_flags |= S_AUTOMOUNT;
675 inode->i_private = data;
676 dentry->d_fsdata = fsd;
677 /* directory inodes start off with i_nlink == 2 (for "." entry) */
678 inc_nlink(inode);
679 d_instantiate(dentry, inode);
680 inc_nlink(d_inode(dentry->d_parent));
681 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
682 return end_creating(dentry);
683}
684EXPORT_SYMBOL(debugfs_create_automount);
685
686/**
687 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
688 * @name: a pointer to a string containing the name of the symbolic link to
689 * create.
690 * @parent: a pointer to the parent dentry for this symbolic link. This
691 * should be a directory dentry if set. If this parameter is NULL,
692 * then the symbolic link will be created in the root of the debugfs
693 * filesystem.
694 * @target: a pointer to a string containing the path to the target of the
695 * symbolic link.
696 *
697 * This function creates a symbolic link with the given name in debugfs that
698 * links to the given target path.
699 *
700 * This function will return a pointer to a dentry if it succeeds. This
701 * pointer must be passed to the debugfs_remove() function when the symbolic
702 * link is to be removed (no automatic cleanup happens if your module is
703 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
704 * will be returned.
705 *
706 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
707 * returned.
708 */
709struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
710 const char *target)
711{
712 struct dentry *dentry;
713 struct inode *inode;
714 char *link = kstrdup(target, GFP_KERNEL);
715 if (!link)
716 return ERR_PTR(-ENOMEM);
717
718 dentry = start_creating(name, parent);
719 if (IS_ERR(dentry)) {
720 kfree(link);
721 return dentry;
722 }
723
724 inode = debugfs_get_inode(dentry->d_sb);
725 if (unlikely(!inode)) {
726 pr_err("out of free dentries, can not create symlink '%s'\n",
727 name);
728 kfree(link);
729 return failed_creating(dentry);
730 }
731 inode->i_mode = S_IFLNK | S_IRWXUGO;
732 inode->i_op = &debugfs_symlink_inode_operations;
733 inode->i_link = link;
734 d_instantiate(dentry, inode);
735 return end_creating(dentry);
736}
737EXPORT_SYMBOL_GPL(debugfs_create_symlink);
738
739static void __debugfs_file_removed(struct dentry *dentry)
740{
741 struct debugfs_fsdata *fsd;
742
743 /*
744 * Paired with the closing smp_mb() implied by a successful
745 * cmpxchg() in debugfs_file_get(): either
746 * debugfs_file_get() must see a dead dentry or we must see a
747 * debugfs_fsdata instance at ->d_fsdata here (or both).
748 */
749 smp_mb();
750 fsd = READ_ONCE(dentry->d_fsdata);
751 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
752 return;
753
754 /* if this was the last reference, we're done */
755 if (refcount_dec_and_test(&fsd->active_users))
756 return;
757
758 /*
759 * If there's still a reference, the code that obtained it can
760 * be in different states:
761 * - The common case of not using cancellations, or already
762 * after debugfs_leave_cancellation(), where we just need
763 * to wait for debugfs_file_put() which signals the completion;
764 * - inside a cancellation section, i.e. between
765 * debugfs_enter_cancellation() and debugfs_leave_cancellation(),
766 * in which case we need to trigger the ->cancel() function,
767 * and then wait for debugfs_file_put() just like in the
768 * previous case;
769 * - before debugfs_enter_cancellation() (but obviously after
770 * debugfs_file_get()), in which case we may not see the
771 * cancellation in the list on the first round of the loop,
772 * but debugfs_enter_cancellation() signals the completion
773 * after adding it, so this code gets woken up to call the
774 * ->cancel() function.
775 */
776 while (refcount_read(&fsd->active_users)) {
777 struct debugfs_cancellation *c;
778
779 /*
780 * Lock the cancellations. Note that the cancellations
781 * structs are meant to be on the stack, so we need to
782 * ensure we either use them here or don't touch them,
783 * and debugfs_leave_cancellation() will wait for this
784 * to be finished processing before exiting one. It may
785 * of course win and remove the cancellation, but then
786 * chances are we never even got into this bit, we only
787 * do if the refcount isn't zero already.
788 */
789 mutex_lock(&fsd->cancellations_mtx);
790 while ((c = list_first_entry_or_null(&fsd->cancellations,
791 typeof(*c), list))) {
792 list_del_init(&c->list);
793 c->cancel(dentry, c->cancel_data);
794 }
795 mutex_unlock(&fsd->cancellations_mtx);
796
797 wait_for_completion(&fsd->active_users_drained);
798 }
799}
800
801static void remove_one(struct dentry *victim)
802{
803 if (d_is_reg(victim))
804 __debugfs_file_removed(victim);
805 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
806}
807
808/**
809 * debugfs_remove - recursively removes a directory
810 * @dentry: a pointer to a the dentry of the directory to be removed. If this
811 * parameter is NULL or an error value, nothing will be done.
812 *
813 * This function recursively removes a directory tree in debugfs that
814 * was previously created with a call to another debugfs function
815 * (like debugfs_create_file() or variants thereof.)
816 *
817 * This function is required to be called in order for the file to be
818 * removed, no automatic cleanup of files will happen when a module is
819 * removed, you are responsible here.
820 */
821void debugfs_remove(struct dentry *dentry)
822{
823 if (IS_ERR_OR_NULL(dentry))
824 return;
825
826 simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
827 simple_recursive_removal(dentry, remove_one);
828 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
829}
830EXPORT_SYMBOL_GPL(debugfs_remove);
831
832/**
833 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
834 * @name: a pointer to a string containing the name of the item to look up.
835 * @parent: a pointer to the parent dentry of the item.
836 *
837 * This is the equlivant of doing something like
838 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
839 * handled for the directory being looked up.
840 */
841void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
842{
843 struct dentry *dentry;
844
845 dentry = debugfs_lookup(name, parent);
846 if (!dentry)
847 return;
848
849 debugfs_remove(dentry);
850 dput(dentry);
851}
852EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
853
854/**
855 * debugfs_rename - rename a file/directory in the debugfs filesystem
856 * @old_dir: a pointer to the parent dentry for the renamed object. This
857 * should be a directory dentry.
858 * @old_dentry: dentry of an object to be renamed.
859 * @new_dir: a pointer to the parent dentry where the object should be
860 * moved. This should be a directory dentry.
861 * @new_name: a pointer to a string containing the target name.
862 *
863 * This function renames a file/directory in debugfs. The target must not
864 * exist for rename to succeed.
865 *
866 * This function will return a pointer to old_dentry (which is updated to
867 * reflect renaming) if it succeeds. If an error occurs, ERR_PTR(-ERROR)
868 * will be returned.
869 *
870 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
871 * returned.
872 */
873struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
874 struct dentry *new_dir, const char *new_name)
875{
876 int error;
877 struct dentry *dentry = NULL, *trap;
878 struct name_snapshot old_name;
879
880 if (IS_ERR(old_dir))
881 return old_dir;
882 if (IS_ERR(new_dir))
883 return new_dir;
884 if (IS_ERR_OR_NULL(old_dentry))
885 return old_dentry;
886
887 trap = lock_rename(new_dir, old_dir);
888 /* Source or destination directories don't exist? */
889 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
890 goto exit;
891 /* Source does not exist, cyclic rename, or mountpoint? */
892 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
893 d_mountpoint(old_dentry))
894 goto exit;
895 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
896 /* Lookup failed, cyclic rename or target exists? */
897 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
898 goto exit;
899
900 take_dentry_name_snapshot(&old_name, old_dentry);
901
902 error = simple_rename(&nop_mnt_idmap, d_inode(old_dir), old_dentry,
903 d_inode(new_dir), dentry, 0);
904 if (error) {
905 release_dentry_name_snapshot(&old_name);
906 goto exit;
907 }
908 d_move(old_dentry, dentry);
909 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
910 d_is_dir(old_dentry),
911 NULL, old_dentry);
912 release_dentry_name_snapshot(&old_name);
913 unlock_rename(new_dir, old_dir);
914 dput(dentry);
915 return old_dentry;
916exit:
917 if (dentry && !IS_ERR(dentry))
918 dput(dentry);
919 unlock_rename(new_dir, old_dir);
920 if (IS_ERR(dentry))
921 return dentry;
922 return ERR_PTR(-EINVAL);
923}
924EXPORT_SYMBOL_GPL(debugfs_rename);
925
926/**
927 * debugfs_initialized - Tells whether debugfs has been registered
928 */
929bool debugfs_initialized(void)
930{
931 return debugfs_registered;
932}
933EXPORT_SYMBOL_GPL(debugfs_initialized);
934
935static int __init debugfs_kernel(char *str)
936{
937 if (str) {
938 if (!strcmp(str, "on"))
939 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
940 else if (!strcmp(str, "no-mount"))
941 debugfs_allow = DEBUGFS_ALLOW_API;
942 else if (!strcmp(str, "off"))
943 debugfs_allow = 0;
944 }
945
946 return 0;
947}
948early_param("debugfs", debugfs_kernel);
949static int __init debugfs_init(void)
950{
951 int retval;
952
953 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
954 return -EPERM;
955
956 retval = sysfs_create_mount_point(kernel_kobj, "debug");
957 if (retval)
958 return retval;
959
960 retval = register_filesystem(&debug_fs_type);
961 if (retval)
962 sysfs_remove_mount_point(kernel_kobj, "debug");
963 else
964 debugfs_registered = true;
965
966 return retval;
967}
968core_initcall(debugfs_init);