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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/*
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 0755
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, umode_t mode, dev_t dev,
38 void *data, const struct file_operations *fops)
39
40{
41 struct inode *inode = new_inode(sb);
42
43 if (inode) {
44 inode->i_ino = get_next_ino();
45 inode->i_mode = mode;
46 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
47 switch (mode & S_IFMT) {
48 default:
49 init_special_inode(inode, mode, dev);
50 break;
51 case S_IFREG:
52 inode->i_fop = fops ? fops : &debugfs_file_operations;
53 inode->i_private = data;
54 break;
55 case S_IFLNK:
56 inode->i_op = &debugfs_link_operations;
57 inode->i_fop = fops;
58 inode->i_private = data;
59 break;
60 case S_IFDIR:
61 inode->i_op = &simple_dir_inode_operations;
62 inode->i_fop = fops ? fops : &simple_dir_operations;
63 inode->i_private = data;
64
65 /* directory inodes start off with i_nlink == 2
66 * (for "." entry) */
67 inc_nlink(inode);
68 break;
69 }
70 }
71 return inode;
72}
73
74/* SMP-safe */
75static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
76 umode_t mode, dev_t dev, void *data,
77 const struct file_operations *fops)
78{
79 struct inode *inode;
80 int error = -EPERM;
81
82 if (dentry->d_inode)
83 return -EEXIST;
84
85 inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops);
86 if (inode) {
87 d_instantiate(dentry, inode);
88 dget(dentry);
89 error = 0;
90 }
91 return error;
92}
93
94static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode,
95 void *data, const struct file_operations *fops)
96{
97 int res;
98
99 mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
100 res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
101 if (!res) {
102 inc_nlink(dir);
103 fsnotify_mkdir(dir, dentry);
104 }
105 return res;
106}
107
108static int debugfs_link(struct inode *dir, struct dentry *dentry, umode_t mode,
109 void *data, const struct file_operations *fops)
110{
111 mode = (mode & S_IALLUGO) | S_IFLNK;
112 return debugfs_mknod(dir, dentry, mode, 0, data, fops);
113}
114
115static int debugfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
116 void *data, const struct file_operations *fops)
117{
118 int res;
119
120 mode = (mode & S_IALLUGO) | S_IFREG;
121 res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
122 if (!res)
123 fsnotify_create(dir, dentry);
124 return res;
125}
126
127static inline int debugfs_positive(struct dentry *dentry)
128{
129 return dentry->d_inode && !d_unhashed(dentry);
130}
131
132struct debugfs_mount_opts {
133 uid_t uid;
134 gid_t gid;
135 umode_t mode;
136};
137
138enum {
139 Opt_uid,
140 Opt_gid,
141 Opt_mode,
142 Opt_err
143};
144
145static const match_table_t tokens = {
146 {Opt_uid, "uid=%u"},
147 {Opt_gid, "gid=%u"},
148 {Opt_mode, "mode=%o"},
149 {Opt_err, NULL}
150};
151
152struct debugfs_fs_info {
153 struct debugfs_mount_opts mount_opts;
154};
155
156static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
157{
158 substring_t args[MAX_OPT_ARGS];
159 int option;
160 int token;
161 char *p;
162
163 opts->mode = DEBUGFS_DEFAULT_MODE;
164
165 while ((p = strsep(&data, ",")) != NULL) {
166 if (!*p)
167 continue;
168
169 token = match_token(p, tokens, args);
170 switch (token) {
171 case Opt_uid:
172 if (match_int(&args[0], &option))
173 return -EINVAL;
174 opts->uid = option;
175 break;
176 case Opt_gid:
177 if (match_octal(&args[0], &option))
178 return -EINVAL;
179 opts->gid = option;
180 break;
181 case Opt_mode:
182 if (match_octal(&args[0], &option))
183 return -EINVAL;
184 opts->mode = option & S_IALLUGO;
185 break;
186 /*
187 * We might like to report bad mount options here;
188 * but traditionally debugfs has ignored all mount options
189 */
190 }
191 }
192
193 return 0;
194}
195
196static int debugfs_apply_options(struct super_block *sb)
197{
198 struct debugfs_fs_info *fsi = sb->s_fs_info;
199 struct inode *inode = sb->s_root->d_inode;
200 struct debugfs_mount_opts *opts = &fsi->mount_opts;
201
202 inode->i_mode &= ~S_IALLUGO;
203 inode->i_mode |= opts->mode;
204
205 inode->i_uid = opts->uid;
206 inode->i_gid = opts->gid;
207
208 return 0;
209}
210
211static int debugfs_remount(struct super_block *sb, int *flags, char *data)
212{
213 int err;
214 struct debugfs_fs_info *fsi = sb->s_fs_info;
215
216 err = debugfs_parse_options(data, &fsi->mount_opts);
217 if (err)
218 goto fail;
219
220 debugfs_apply_options(sb);
221
222fail:
223 return err;
224}
225
226static int debugfs_show_options(struct seq_file *m, struct dentry *root)
227{
228 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
229 struct debugfs_mount_opts *opts = &fsi->mount_opts;
230
231 if (opts->uid != 0)
232 seq_printf(m, ",uid=%u", opts->uid);
233 if (opts->gid != 0)
234 seq_printf(m, ",gid=%u", opts->gid);
235 if (opts->mode != DEBUGFS_DEFAULT_MODE)
236 seq_printf(m, ",mode=%o", opts->mode);
237
238 return 0;
239}
240
241static const struct super_operations debugfs_super_operations = {
242 .statfs = simple_statfs,
243 .remount_fs = debugfs_remount,
244 .show_options = debugfs_show_options,
245};
246
247static int debug_fill_super(struct super_block *sb, void *data, int silent)
248{
249 static struct tree_descr debug_files[] = {{""}};
250 struct debugfs_fs_info *fsi;
251 int err;
252
253 save_mount_options(sb, data);
254
255 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
256 sb->s_fs_info = fsi;
257 if (!fsi) {
258 err = -ENOMEM;
259 goto fail;
260 }
261
262 err = debugfs_parse_options(data, &fsi->mount_opts);
263 if (err)
264 goto fail;
265
266 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
267 if (err)
268 goto fail;
269
270 sb->s_op = &debugfs_super_operations;
271
272 debugfs_apply_options(sb);
273
274 return 0;
275
276fail:
277 kfree(fsi);
278 sb->s_fs_info = NULL;
279 return err;
280}
281
282static struct dentry *debug_mount(struct file_system_type *fs_type,
283 int flags, const char *dev_name,
284 void *data)
285{
286 return mount_single(fs_type, flags, data, debug_fill_super);
287}
288
289static struct file_system_type debug_fs_type = {
290 .owner = THIS_MODULE,
291 .name = "debugfs",
292 .mount = debug_mount,
293 .kill_sb = kill_litter_super,
294};
295
296static int debugfs_create_by_name(const char *name, umode_t mode,
297 struct dentry *parent,
298 struct dentry **dentry,
299 void *data,
300 const struct file_operations *fops)
301{
302 int error = 0;
303
304 /* If the parent is not specified, we create it in the root.
305 * We need the root dentry to do this, which is in the super
306 * block. A pointer to that is in the struct vfsmount that we
307 * have around.
308 */
309 if (!parent)
310 parent = debugfs_mount->mnt_root;
311
312 *dentry = NULL;
313 mutex_lock(&parent->d_inode->i_mutex);
314 *dentry = lookup_one_len(name, parent, strlen(name));
315 if (!IS_ERR(*dentry)) {
316 switch (mode & S_IFMT) {
317 case S_IFDIR:
318 error = debugfs_mkdir(parent->d_inode, *dentry, mode,
319 data, fops);
320 break;
321 case S_IFLNK:
322 error = debugfs_link(parent->d_inode, *dentry, mode,
323 data, fops);
324 break;
325 default:
326 error = debugfs_create(parent->d_inode, *dentry, mode,
327 data, fops);
328 break;
329 }
330 dput(*dentry);
331 } else
332 error = PTR_ERR(*dentry);
333 mutex_unlock(&parent->d_inode->i_mutex);
334
335 return error;
336}
337
338/**
339 * debugfs_create_file - create a file in the debugfs filesystem
340 * @name: a pointer to a string containing the name of the file to create.
341 * @mode: the permission that the file should have.
342 * @parent: a pointer to the parent dentry for this file. This should be a
343 * directory dentry if set. If this paramater is NULL, then the
344 * file will be created in the root of the debugfs filesystem.
345 * @data: a pointer to something that the caller will want to get to later
346 * on. The inode.i_private pointer will point to this value on
347 * the open() call.
348 * @fops: a pointer to a struct file_operations that should be used for
349 * this file.
350 *
351 * This is the basic "create a file" function for debugfs. It allows for a
352 * wide range of flexibility in creating a file, or a directory (if you want
353 * to create a directory, the debugfs_create_dir() function is
354 * recommended to be used instead.)
355 *
356 * This function will return a pointer to a dentry if it succeeds. This
357 * pointer must be passed to the debugfs_remove() function when the file is
358 * to be removed (no automatic cleanup happens if your module is unloaded,
359 * you are responsible here.) If an error occurs, %NULL will be returned.
360 *
361 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
362 * returned.
363 */
364struct dentry *debugfs_create_file(const char *name, umode_t mode,
365 struct dentry *parent, void *data,
366 const struct file_operations *fops)
367{
368 struct dentry *dentry = NULL;
369 int error;
370
371 pr_debug("debugfs: creating file '%s'\n",name);
372
373 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
374 &debugfs_mount_count);
375 if (error)
376 goto exit;
377
378 error = debugfs_create_by_name(name, mode, parent, &dentry,
379 data, fops);
380 if (error) {
381 dentry = NULL;
382 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
383 goto exit;
384 }
385exit:
386 return dentry;
387}
388EXPORT_SYMBOL_GPL(debugfs_create_file);
389
390/**
391 * debugfs_create_dir - create a directory in the debugfs filesystem
392 * @name: a pointer to a string containing the name of the directory to
393 * create.
394 * @parent: a pointer to the parent dentry for this file. This should be a
395 * directory dentry if set. If this paramater is NULL, then the
396 * directory will be created in the root of the debugfs filesystem.
397 *
398 * This function creates a directory in debugfs with the given name.
399 *
400 * This function will return a pointer to a dentry if it succeeds. This
401 * pointer must be passed to the debugfs_remove() function when the file is
402 * to be removed (no automatic cleanup happens if your module is unloaded,
403 * you are responsible here.) If an error occurs, %NULL will be returned.
404 *
405 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
406 * returned.
407 */
408struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
409{
410 return debugfs_create_file(name,
411 S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
412 parent, NULL, NULL);
413}
414EXPORT_SYMBOL_GPL(debugfs_create_dir);
415
416/**
417 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
418 * @name: a pointer to a string containing the name of the symbolic link to
419 * create.
420 * @parent: a pointer to the parent dentry for this symbolic link. This
421 * should be a directory dentry if set. If this paramater is NULL,
422 * then the symbolic link will be created in the root of the debugfs
423 * filesystem.
424 * @target: a pointer to a string containing the path to the target of the
425 * symbolic link.
426 *
427 * This function creates a symbolic link with the given name in debugfs that
428 * links to the given target path.
429 *
430 * This function will return a pointer to a dentry if it succeeds. This
431 * pointer must be passed to the debugfs_remove() function when the symbolic
432 * link is to be removed (no automatic cleanup happens if your module is
433 * unloaded, you are responsible here.) If an error occurs, %NULL will be
434 * returned.
435 *
436 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
437 * returned.
438 */
439struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
440 const char *target)
441{
442 struct dentry *result;
443 char *link;
444
445 link = kstrdup(target, GFP_KERNEL);
446 if (!link)
447 return NULL;
448
449 result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
450 NULL);
451 if (!result)
452 kfree(link);
453 return result;
454}
455EXPORT_SYMBOL_GPL(debugfs_create_symlink);
456
457static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
458{
459 int ret = 0;
460
461 if (debugfs_positive(dentry)) {
462 if (dentry->d_inode) {
463 dget(dentry);
464 switch (dentry->d_inode->i_mode & S_IFMT) {
465 case S_IFDIR:
466 ret = simple_rmdir(parent->d_inode, dentry);
467 break;
468 case S_IFLNK:
469 kfree(dentry->d_inode->i_private);
470 /* fall through */
471 default:
472 simple_unlink(parent->d_inode, dentry);
473 break;
474 }
475 if (!ret)
476 d_delete(dentry);
477 dput(dentry);
478 }
479 }
480 return ret;
481}
482
483/**
484 * debugfs_remove - removes a file or directory from the debugfs filesystem
485 * @dentry: a pointer to a the dentry of the file or directory to be
486 * removed.
487 *
488 * This function removes a file or directory in debugfs that was previously
489 * created with a call to another debugfs function (like
490 * debugfs_create_file() or variants thereof.)
491 *
492 * This function is required to be called in order for the file to be
493 * removed, no automatic cleanup of files will happen when a module is
494 * removed, you are responsible here.
495 */
496void debugfs_remove(struct dentry *dentry)
497{
498 struct dentry *parent;
499 int ret;
500
501 if (!dentry)
502 return;
503
504 parent = dentry->d_parent;
505 if (!parent || !parent->d_inode)
506 return;
507
508 mutex_lock(&parent->d_inode->i_mutex);
509 ret = __debugfs_remove(dentry, parent);
510 mutex_unlock(&parent->d_inode->i_mutex);
511 if (!ret)
512 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
513}
514EXPORT_SYMBOL_GPL(debugfs_remove);
515
516/**
517 * debugfs_remove_recursive - recursively removes a directory
518 * @dentry: a pointer to a the dentry of the directory to be removed.
519 *
520 * This function recursively removes a directory tree in debugfs that
521 * was previously created with a call to another debugfs function
522 * (like debugfs_create_file() or variants thereof.)
523 *
524 * This function is required to be called in order for the file to be
525 * removed, no automatic cleanup of files will happen when a module is
526 * removed, you are responsible here.
527 */
528void debugfs_remove_recursive(struct dentry *dentry)
529{
530 struct dentry *child;
531 struct dentry *parent;
532
533 if (!dentry)
534 return;
535
536 parent = dentry->d_parent;
537 if (!parent || !parent->d_inode)
538 return;
539
540 parent = dentry;
541 mutex_lock(&parent->d_inode->i_mutex);
542
543 while (1) {
544 /*
545 * When all dentries under "parent" has been removed,
546 * walk up the tree until we reach our starting point.
547 */
548 if (list_empty(&parent->d_subdirs)) {
549 mutex_unlock(&parent->d_inode->i_mutex);
550 if (parent == dentry)
551 break;
552 parent = parent->d_parent;
553 mutex_lock(&parent->d_inode->i_mutex);
554 }
555 child = list_entry(parent->d_subdirs.next, struct dentry,
556 d_u.d_child);
557 next_sibling:
558
559 /*
560 * If "child" isn't empty, walk down the tree and
561 * remove all its descendants first.
562 */
563 if (!list_empty(&child->d_subdirs)) {
564 mutex_unlock(&parent->d_inode->i_mutex);
565 parent = child;
566 mutex_lock(&parent->d_inode->i_mutex);
567 continue;
568 }
569 __debugfs_remove(child, parent);
570 if (parent->d_subdirs.next == &child->d_u.d_child) {
571 /*
572 * Try the next sibling.
573 */
574 if (child->d_u.d_child.next != &parent->d_subdirs) {
575 child = list_entry(child->d_u.d_child.next,
576 struct dentry,
577 d_u.d_child);
578 goto next_sibling;
579 }
580
581 /*
582 * Avoid infinite loop if we fail to remove
583 * one dentry.
584 */
585 mutex_unlock(&parent->d_inode->i_mutex);
586 break;
587 }
588 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
589 }
590
591 parent = dentry->d_parent;
592 mutex_lock(&parent->d_inode->i_mutex);
593 __debugfs_remove(dentry, parent);
594 mutex_unlock(&parent->d_inode->i_mutex);
595 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
596}
597EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
598
599/**
600 * debugfs_rename - rename a file/directory in the debugfs filesystem
601 * @old_dir: a pointer to the parent dentry for the renamed object. This
602 * should be a directory dentry.
603 * @old_dentry: dentry of an object to be renamed.
604 * @new_dir: a pointer to the parent dentry where the object should be
605 * moved. This should be a directory dentry.
606 * @new_name: a pointer to a string containing the target name.
607 *
608 * This function renames a file/directory in debugfs. The target must not
609 * exist for rename to succeed.
610 *
611 * This function will return a pointer to old_dentry (which is updated to
612 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
613 * returned.
614 *
615 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
616 * returned.
617 */
618struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
619 struct dentry *new_dir, const char *new_name)
620{
621 int error;
622 struct dentry *dentry = NULL, *trap;
623 const char *old_name;
624
625 trap = lock_rename(new_dir, old_dir);
626 /* Source or destination directories don't exist? */
627 if (!old_dir->d_inode || !new_dir->d_inode)
628 goto exit;
629 /* Source does not exist, cyclic rename, or mountpoint? */
630 if (!old_dentry->d_inode || old_dentry == trap ||
631 d_mountpoint(old_dentry))
632 goto exit;
633 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
634 /* Lookup failed, cyclic rename or target exists? */
635 if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
636 goto exit;
637
638 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
639
640 error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
641 dentry);
642 if (error) {
643 fsnotify_oldname_free(old_name);
644 goto exit;
645 }
646 d_move(old_dentry, dentry);
647 fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
648 S_ISDIR(old_dentry->d_inode->i_mode),
649 NULL, old_dentry);
650 fsnotify_oldname_free(old_name);
651 unlock_rename(new_dir, old_dir);
652 dput(dentry);
653 return old_dentry;
654exit:
655 if (dentry && !IS_ERR(dentry))
656 dput(dentry);
657 unlock_rename(new_dir, old_dir);
658 return NULL;
659}
660EXPORT_SYMBOL_GPL(debugfs_rename);
661
662/**
663 * debugfs_initialized - Tells whether debugfs has been registered
664 */
665bool debugfs_initialized(void)
666{
667 return debugfs_registered;
668}
669EXPORT_SYMBOL_GPL(debugfs_initialized);
670
671
672static struct kobject *debug_kobj;
673
674static int __init debugfs_init(void)
675{
676 int retval;
677
678 debug_kobj = kobject_create_and_add("debug", kernel_kobj);
679 if (!debug_kobj)
680 return -EINVAL;
681
682 retval = register_filesystem(&debug_fs_type);
683 if (retval)
684 kobject_put(debug_kobj);
685 else
686 debugfs_registered = true;
687
688 return retval;
689}
690core_initcall(debugfs_init);
691