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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 user_namespace *mnt_userns,
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(&init_user_ns, 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 inode->i_atime = inode->i_mtime =
76 inode->i_ctime = current_time(inode);
77 }
78 return inode;
79}
80
81struct debugfs_mount_opts {
82 kuid_t uid;
83 kgid_t gid;
84 umode_t mode;
85 /* Opt_* bitfield. */
86 unsigned int opts;
87};
88
89enum {
90 Opt_uid,
91 Opt_gid,
92 Opt_mode,
93 Opt_err
94};
95
96static const match_table_t tokens = {
97 {Opt_uid, "uid=%u"},
98 {Opt_gid, "gid=%u"},
99 {Opt_mode, "mode=%o"},
100 {Opt_err, NULL}
101};
102
103struct debugfs_fs_info {
104 struct debugfs_mount_opts mount_opts;
105};
106
107static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
108{
109 substring_t args[MAX_OPT_ARGS];
110 int option;
111 int token;
112 kuid_t uid;
113 kgid_t gid;
114 char *p;
115
116 opts->opts = 0;
117 opts->mode = DEBUGFS_DEFAULT_MODE;
118
119 while ((p = strsep(&data, ",")) != NULL) {
120 if (!*p)
121 continue;
122
123 token = match_token(p, tokens, args);
124 switch (token) {
125 case Opt_uid:
126 if (match_int(&args[0], &option))
127 return -EINVAL;
128 uid = make_kuid(current_user_ns(), option);
129 if (!uid_valid(uid))
130 return -EINVAL;
131 opts->uid = uid;
132 break;
133 case Opt_gid:
134 if (match_int(&args[0], &option))
135 return -EINVAL;
136 gid = make_kgid(current_user_ns(), option);
137 if (!gid_valid(gid))
138 return -EINVAL;
139 opts->gid = gid;
140 break;
141 case Opt_mode:
142 if (match_octal(&args[0], &option))
143 return -EINVAL;
144 opts->mode = option & S_IALLUGO;
145 break;
146 /*
147 * We might like to report bad mount options here;
148 * but traditionally debugfs has ignored all mount options
149 */
150 }
151
152 opts->opts |= BIT(token);
153 }
154
155 return 0;
156}
157
158static void _debugfs_apply_options(struct super_block *sb, bool remount)
159{
160 struct debugfs_fs_info *fsi = sb->s_fs_info;
161 struct inode *inode = d_inode(sb->s_root);
162 struct debugfs_mount_opts *opts = &fsi->mount_opts;
163
164 /*
165 * On remount, only reset mode/uid/gid if they were provided as mount
166 * options.
167 */
168
169 if (!remount || opts->opts & BIT(Opt_mode)) {
170 inode->i_mode &= ~S_IALLUGO;
171 inode->i_mode |= opts->mode;
172 }
173
174 if (!remount || opts->opts & BIT(Opt_uid))
175 inode->i_uid = opts->uid;
176
177 if (!remount || opts->opts & BIT(Opt_gid))
178 inode->i_gid = opts->gid;
179}
180
181static void debugfs_apply_options(struct super_block *sb)
182{
183 _debugfs_apply_options(sb, false);
184}
185
186static void debugfs_apply_options_remount(struct super_block *sb)
187{
188 _debugfs_apply_options(sb, true);
189}
190
191static int debugfs_remount(struct super_block *sb, int *flags, char *data)
192{
193 int err;
194 struct debugfs_fs_info *fsi = sb->s_fs_info;
195
196 sync_filesystem(sb);
197 err = debugfs_parse_options(data, &fsi->mount_opts);
198 if (err)
199 goto fail;
200
201 debugfs_apply_options_remount(sb);
202
203fail:
204 return err;
205}
206
207static int debugfs_show_options(struct seq_file *m, struct dentry *root)
208{
209 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
210 struct debugfs_mount_opts *opts = &fsi->mount_opts;
211
212 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
213 seq_printf(m, ",uid=%u",
214 from_kuid_munged(&init_user_ns, opts->uid));
215 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
216 seq_printf(m, ",gid=%u",
217 from_kgid_munged(&init_user_ns, opts->gid));
218 if (opts->mode != DEBUGFS_DEFAULT_MODE)
219 seq_printf(m, ",mode=%o", opts->mode);
220
221 return 0;
222}
223
224static void debugfs_free_inode(struct inode *inode)
225{
226 if (S_ISLNK(inode->i_mode))
227 kfree(inode->i_link);
228 free_inode_nonrcu(inode);
229}
230
231static const struct super_operations debugfs_super_operations = {
232 .statfs = simple_statfs,
233 .remount_fs = debugfs_remount,
234 .show_options = debugfs_show_options,
235 .free_inode = debugfs_free_inode,
236};
237
238static void debugfs_release_dentry(struct dentry *dentry)
239{
240 void *fsd = dentry->d_fsdata;
241
242 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
243 kfree(dentry->d_fsdata);
244}
245
246static struct vfsmount *debugfs_automount(struct path *path)
247{
248 debugfs_automount_t f;
249 f = (debugfs_automount_t)path->dentry->d_fsdata;
250 return f(path->dentry, d_inode(path->dentry)->i_private);
251}
252
253static const struct dentry_operations debugfs_dops = {
254 .d_delete = always_delete_dentry,
255 .d_release = debugfs_release_dentry,
256 .d_automount = debugfs_automount,
257};
258
259static int debug_fill_super(struct super_block *sb, void *data, int silent)
260{
261 static const struct tree_descr debug_files[] = {{""}};
262 struct debugfs_fs_info *fsi;
263 int err;
264
265 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
266 sb->s_fs_info = fsi;
267 if (!fsi) {
268 err = -ENOMEM;
269 goto fail;
270 }
271
272 err = debugfs_parse_options(data, &fsi->mount_opts);
273 if (err)
274 goto fail;
275
276 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
277 if (err)
278 goto fail;
279
280 sb->s_op = &debugfs_super_operations;
281 sb->s_d_op = &debugfs_dops;
282
283 debugfs_apply_options(sb);
284
285 return 0;
286
287fail:
288 kfree(fsi);
289 sb->s_fs_info = NULL;
290 return err;
291}
292
293static struct dentry *debug_mount(struct file_system_type *fs_type,
294 int flags, const char *dev_name,
295 void *data)
296{
297 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
298 return ERR_PTR(-EPERM);
299
300 return mount_single(fs_type, flags, data, debug_fill_super);
301}
302
303static struct file_system_type debug_fs_type = {
304 .owner = THIS_MODULE,
305 .name = "debugfs",
306 .mount = debug_mount,
307 .kill_sb = kill_litter_super,
308};
309MODULE_ALIAS_FS("debugfs");
310
311/**
312 * debugfs_lookup() - look up an existing debugfs file
313 * @name: a pointer to a string containing the name of the file to look up.
314 * @parent: a pointer to the parent dentry of the file.
315 *
316 * This function will return a pointer to a dentry if it succeeds. If the file
317 * doesn't exist or an error occurs, %NULL will be returned. The returned
318 * dentry must be passed to dput() when it is no longer needed.
319 *
320 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
321 * returned.
322 */
323struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
324{
325 struct dentry *dentry;
326
327 if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
328 return NULL;
329
330 if (!parent)
331 parent = debugfs_mount->mnt_root;
332
333 dentry = lookup_positive_unlocked(name, parent, strlen(name));
334 if (IS_ERR(dentry))
335 return NULL;
336 return dentry;
337}
338EXPORT_SYMBOL_GPL(debugfs_lookup);
339
340static struct dentry *start_creating(const char *name, struct dentry *parent)
341{
342 struct dentry *dentry;
343 int error;
344
345 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
346 return ERR_PTR(-EPERM);
347
348 if (!debugfs_initialized())
349 return ERR_PTR(-ENOENT);
350
351 pr_debug("creating file '%s'\n", name);
352
353 if (IS_ERR(parent))
354 return parent;
355
356 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
357 &debugfs_mount_count);
358 if (error) {
359 pr_err("Unable to pin filesystem for file '%s'\n", name);
360 return ERR_PTR(error);
361 }
362
363 /* If the parent is not specified, we create it in the root.
364 * We need the root dentry to do this, which is in the super
365 * block. A pointer to that is in the struct vfsmount that we
366 * have around.
367 */
368 if (!parent)
369 parent = debugfs_mount->mnt_root;
370
371 inode_lock(d_inode(parent));
372 if (unlikely(IS_DEADDIR(d_inode(parent))))
373 dentry = ERR_PTR(-ENOENT);
374 else
375 dentry = lookup_one_len(name, parent, strlen(name));
376 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
377 if (d_is_dir(dentry))
378 pr_err("Directory '%s' with parent '%s' already present!\n",
379 name, parent->d_name.name);
380 else
381 pr_err("File '%s' in directory '%s' already present!\n",
382 name, parent->d_name.name);
383 dput(dentry);
384 dentry = ERR_PTR(-EEXIST);
385 }
386
387 if (IS_ERR(dentry)) {
388 inode_unlock(d_inode(parent));
389 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
390 }
391
392 return dentry;
393}
394
395static struct dentry *failed_creating(struct dentry *dentry)
396{
397 inode_unlock(d_inode(dentry->d_parent));
398 dput(dentry);
399 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
400 return ERR_PTR(-ENOMEM);
401}
402
403static struct dentry *end_creating(struct dentry *dentry)
404{
405 inode_unlock(d_inode(dentry->d_parent));
406 return dentry;
407}
408
409static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
410 struct dentry *parent, void *data,
411 const struct file_operations *proxy_fops,
412 const struct file_operations *real_fops)
413{
414 struct dentry *dentry;
415 struct inode *inode;
416
417 if (!(mode & S_IFMT))
418 mode |= S_IFREG;
419 BUG_ON(!S_ISREG(mode));
420 dentry = start_creating(name, parent);
421
422 if (IS_ERR(dentry))
423 return dentry;
424
425 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
426 failed_creating(dentry);
427 return ERR_PTR(-EPERM);
428 }
429
430 inode = debugfs_get_inode(dentry->d_sb);
431 if (unlikely(!inode)) {
432 pr_err("out of free dentries, can not create file '%s'\n",
433 name);
434 return failed_creating(dentry);
435 }
436
437 inode->i_mode = mode;
438 inode->i_private = data;
439
440 inode->i_op = &debugfs_file_inode_operations;
441 inode->i_fop = proxy_fops;
442 dentry->d_fsdata = (void *)((unsigned long)real_fops |
443 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
444
445 d_instantiate(dentry, inode);
446 fsnotify_create(d_inode(dentry->d_parent), dentry);
447 return end_creating(dentry);
448}
449
450/**
451 * debugfs_create_file - create a file in the debugfs filesystem
452 * @name: a pointer to a string containing the name of the file to create.
453 * @mode: the permission that the file should have.
454 * @parent: a pointer to the parent dentry for this file. This should be a
455 * directory dentry if set. If this parameter is NULL, then the
456 * file will be created in the root of the debugfs filesystem.
457 * @data: a pointer to something that the caller will want to get to later
458 * on. The inode.i_private pointer will point to this value on
459 * the open() call.
460 * @fops: a pointer to a struct file_operations that should be used for
461 * this file.
462 *
463 * This is the basic "create a file" function for debugfs. It allows for a
464 * wide range of flexibility in creating a file, or a directory (if you want
465 * to create a directory, the debugfs_create_dir() function is
466 * recommended to be used instead.)
467 *
468 * This function will return a pointer to a dentry if it succeeds. This
469 * pointer must be passed to the debugfs_remove() function when the file is
470 * to be removed (no automatic cleanup happens if your module is unloaded,
471 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
472 * returned.
473 *
474 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
475 * returned.
476 *
477 * NOTE: it's expected that most callers should _ignore_ the errors returned
478 * by this function. Other debugfs functions handle the fact that the "dentry"
479 * passed to them could be an error and they don't crash in that case.
480 * Drivers should generally work fine even if debugfs fails to init anyway.
481 */
482struct dentry *debugfs_create_file(const char *name, umode_t mode,
483 struct dentry *parent, void *data,
484 const struct file_operations *fops)
485{
486
487 return __debugfs_create_file(name, mode, parent, data,
488 fops ? &debugfs_full_proxy_file_operations :
489 &debugfs_noop_file_operations,
490 fops);
491}
492EXPORT_SYMBOL_GPL(debugfs_create_file);
493
494/**
495 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
496 * @name: a pointer to a string containing the name of the file to create.
497 * @mode: the permission that the file should have.
498 * @parent: a pointer to the parent dentry for this file. This should be a
499 * directory dentry if set. If this parameter is NULL, then the
500 * file will be created in the root of the debugfs filesystem.
501 * @data: a pointer to something that the caller will want to get to later
502 * on. The inode.i_private pointer will point to this value on
503 * the open() call.
504 * @fops: a pointer to a struct file_operations that should be used for
505 * this file.
506 *
507 * debugfs_create_file_unsafe() is completely analogous to
508 * debugfs_create_file(), the only difference being that the fops
509 * handed it will not get protected against file removals by the
510 * debugfs core.
511 *
512 * It is your responsibility to protect your struct file_operation
513 * methods against file removals by means of debugfs_file_get()
514 * and debugfs_file_put(). ->open() is still protected by
515 * debugfs though.
516 *
517 * Any struct file_operations defined by means of
518 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
519 * thus, may be used here.
520 */
521struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
522 struct dentry *parent, void *data,
523 const struct file_operations *fops)
524{
525
526 return __debugfs_create_file(name, mode, parent, data,
527 fops ? &debugfs_open_proxy_file_operations :
528 &debugfs_noop_file_operations,
529 fops);
530}
531EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
532
533/**
534 * debugfs_create_file_size - create a file in the debugfs filesystem
535 * @name: a pointer to a string containing the name of the file to create.
536 * @mode: the permission that the file should have.
537 * @parent: a pointer to the parent dentry for this file. This should be a
538 * directory dentry if set. If this parameter is NULL, then the
539 * file will be created in the root of the debugfs filesystem.
540 * @data: a pointer to something that the caller will want to get to later
541 * on. The inode.i_private pointer will point to this value on
542 * the open() call.
543 * @fops: a pointer to a struct file_operations that should be used for
544 * this file.
545 * @file_size: initial file size
546 *
547 * This is the basic "create a file" function for debugfs. It allows for a
548 * wide range of flexibility in creating a file, or a directory (if you want
549 * to create a directory, the debugfs_create_dir() function is
550 * recommended to be used instead.)
551 */
552void debugfs_create_file_size(const char *name, umode_t mode,
553 struct dentry *parent, void *data,
554 const struct file_operations *fops,
555 loff_t file_size)
556{
557 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
558
559 if (!IS_ERR(de))
560 d_inode(de)->i_size = file_size;
561}
562EXPORT_SYMBOL_GPL(debugfs_create_file_size);
563
564/**
565 * debugfs_create_dir - create a directory in the debugfs filesystem
566 * @name: a pointer to a string containing the name of the directory to
567 * create.
568 * @parent: a pointer to the parent dentry for this file. This should be a
569 * directory dentry if set. If this parameter is NULL, then the
570 * directory will be created in the root of the debugfs filesystem.
571 *
572 * This function creates a directory in debugfs with the given name.
573 *
574 * This function will return a pointer to a dentry if it succeeds. This
575 * pointer must be passed to the debugfs_remove() function when the file is
576 * to be removed (no automatic cleanup happens if your module is unloaded,
577 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
578 * returned.
579 *
580 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
581 * returned.
582 *
583 * NOTE: it's expected that most callers should _ignore_ the errors returned
584 * by this function. Other debugfs functions handle the fact that the "dentry"
585 * passed to them could be an error and they don't crash in that case.
586 * Drivers should generally work fine even if debugfs fails to init anyway.
587 */
588struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
589{
590 struct dentry *dentry = start_creating(name, parent);
591 struct inode *inode;
592
593 if (IS_ERR(dentry))
594 return dentry;
595
596 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
597 failed_creating(dentry);
598 return ERR_PTR(-EPERM);
599 }
600
601 inode = debugfs_get_inode(dentry->d_sb);
602 if (unlikely(!inode)) {
603 pr_err("out of free dentries, can not create directory '%s'\n",
604 name);
605 return failed_creating(dentry);
606 }
607
608 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
609 inode->i_op = &debugfs_dir_inode_operations;
610 inode->i_fop = &simple_dir_operations;
611
612 /* directory inodes start off with i_nlink == 2 (for "." entry) */
613 inc_nlink(inode);
614 d_instantiate(dentry, inode);
615 inc_nlink(d_inode(dentry->d_parent));
616 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
617 return end_creating(dentry);
618}
619EXPORT_SYMBOL_GPL(debugfs_create_dir);
620
621/**
622 * debugfs_create_automount - create automount point in the debugfs filesystem
623 * @name: a pointer to a string containing the name of the file to create.
624 * @parent: a pointer to the parent dentry for this file. This should be a
625 * directory dentry if set. If this parameter is NULL, then the
626 * file will be created in the root of the debugfs filesystem.
627 * @f: function to be called when pathname resolution steps on that one.
628 * @data: opaque argument to pass to f().
629 *
630 * @f should return what ->d_automount() would.
631 */
632struct dentry *debugfs_create_automount(const char *name,
633 struct dentry *parent,
634 debugfs_automount_t f,
635 void *data)
636{
637 struct dentry *dentry = start_creating(name, parent);
638 struct inode *inode;
639
640 if (IS_ERR(dentry))
641 return dentry;
642
643 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
644 failed_creating(dentry);
645 return ERR_PTR(-EPERM);
646 }
647
648 inode = debugfs_get_inode(dentry->d_sb);
649 if (unlikely(!inode)) {
650 pr_err("out of free dentries, can not create automount '%s'\n",
651 name);
652 return failed_creating(dentry);
653 }
654
655 make_empty_dir_inode(inode);
656 inode->i_flags |= S_AUTOMOUNT;
657 inode->i_private = data;
658 dentry->d_fsdata = (void *)f;
659 /* directory inodes start off with i_nlink == 2 (for "." entry) */
660 inc_nlink(inode);
661 d_instantiate(dentry, inode);
662 inc_nlink(d_inode(dentry->d_parent));
663 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
664 return end_creating(dentry);
665}
666EXPORT_SYMBOL(debugfs_create_automount);
667
668/**
669 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
670 * @name: a pointer to a string containing the name of the symbolic link to
671 * create.
672 * @parent: a pointer to the parent dentry for this symbolic link. This
673 * should be a directory dentry if set. If this parameter is NULL,
674 * then the symbolic link will be created in the root of the debugfs
675 * filesystem.
676 * @target: a pointer to a string containing the path to the target of the
677 * symbolic link.
678 *
679 * This function creates a symbolic link with the given name in debugfs that
680 * links to the given target path.
681 *
682 * This function will return a pointer to a dentry if it succeeds. This
683 * pointer must be passed to the debugfs_remove() function when the symbolic
684 * link is to be removed (no automatic cleanup happens if your module is
685 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
686 * will be returned.
687 *
688 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
689 * returned.
690 */
691struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
692 const char *target)
693{
694 struct dentry *dentry;
695 struct inode *inode;
696 char *link = kstrdup(target, GFP_KERNEL);
697 if (!link)
698 return ERR_PTR(-ENOMEM);
699
700 dentry = start_creating(name, parent);
701 if (IS_ERR(dentry)) {
702 kfree(link);
703 return dentry;
704 }
705
706 inode = debugfs_get_inode(dentry->d_sb);
707 if (unlikely(!inode)) {
708 pr_err("out of free dentries, can not create symlink '%s'\n",
709 name);
710 kfree(link);
711 return failed_creating(dentry);
712 }
713 inode->i_mode = S_IFLNK | S_IRWXUGO;
714 inode->i_op = &debugfs_symlink_inode_operations;
715 inode->i_link = link;
716 d_instantiate(dentry, inode);
717 return end_creating(dentry);
718}
719EXPORT_SYMBOL_GPL(debugfs_create_symlink);
720
721static void __debugfs_file_removed(struct dentry *dentry)
722{
723 struct debugfs_fsdata *fsd;
724
725 /*
726 * Paired with the closing smp_mb() implied by a successful
727 * cmpxchg() in debugfs_file_get(): either
728 * debugfs_file_get() must see a dead dentry or we must see a
729 * debugfs_fsdata instance at ->d_fsdata here (or both).
730 */
731 smp_mb();
732 fsd = READ_ONCE(dentry->d_fsdata);
733 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
734 return;
735 if (!refcount_dec_and_test(&fsd->active_users))
736 wait_for_completion(&fsd->active_users_drained);
737}
738
739static void remove_one(struct dentry *victim)
740{
741 if (d_is_reg(victim))
742 __debugfs_file_removed(victim);
743 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
744}
745
746/**
747 * debugfs_remove - recursively removes a directory
748 * @dentry: a pointer to a the dentry of the directory to be removed. If this
749 * parameter is NULL or an error value, nothing will be done.
750 *
751 * This function recursively removes a directory tree in debugfs that
752 * was previously created with a call to another debugfs function
753 * (like debugfs_create_file() or variants thereof.)
754 *
755 * This function is required to be called in order for the file to be
756 * removed, no automatic cleanup of files will happen when a module is
757 * removed, you are responsible here.
758 */
759void debugfs_remove(struct dentry *dentry)
760{
761 if (IS_ERR_OR_NULL(dentry))
762 return;
763
764 simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
765 simple_recursive_removal(dentry, remove_one);
766 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
767}
768EXPORT_SYMBOL_GPL(debugfs_remove);
769
770/**
771 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
772 * @name: a pointer to a string containing the name of the item to look up.
773 * @parent: a pointer to the parent dentry of the item.
774 *
775 * This is the equlivant of doing something like
776 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
777 * handled for the directory being looked up.
778 */
779void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
780{
781 struct dentry *dentry;
782
783 dentry = debugfs_lookup(name, parent);
784 if (!dentry)
785 return;
786
787 debugfs_remove(dentry);
788 dput(dentry);
789}
790EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
791
792/**
793 * debugfs_rename - rename a file/directory in the debugfs filesystem
794 * @old_dir: a pointer to the parent dentry for the renamed object. This
795 * should be a directory dentry.
796 * @old_dentry: dentry of an object to be renamed.
797 * @new_dir: a pointer to the parent dentry where the object should be
798 * moved. This should be a directory dentry.
799 * @new_name: a pointer to a string containing the target name.
800 *
801 * This function renames a file/directory in debugfs. The target must not
802 * exist for rename to succeed.
803 *
804 * This function will return a pointer to old_dentry (which is updated to
805 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
806 * returned.
807 *
808 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
809 * returned.
810 */
811struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
812 struct dentry *new_dir, const char *new_name)
813{
814 int error;
815 struct dentry *dentry = NULL, *trap;
816 struct name_snapshot old_name;
817
818 if (IS_ERR(old_dir))
819 return old_dir;
820 if (IS_ERR(new_dir))
821 return new_dir;
822 if (IS_ERR_OR_NULL(old_dentry))
823 return old_dentry;
824
825 trap = lock_rename(new_dir, old_dir);
826 /* Source or destination directories don't exist? */
827 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
828 goto exit;
829 /* Source does not exist, cyclic rename, or mountpoint? */
830 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
831 d_mountpoint(old_dentry))
832 goto exit;
833 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
834 /* Lookup failed, cyclic rename or target exists? */
835 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
836 goto exit;
837
838 take_dentry_name_snapshot(&old_name, old_dentry);
839
840 error = simple_rename(&init_user_ns, d_inode(old_dir), old_dentry,
841 d_inode(new_dir), dentry, 0);
842 if (error) {
843 release_dentry_name_snapshot(&old_name);
844 goto exit;
845 }
846 d_move(old_dentry, dentry);
847 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
848 d_is_dir(old_dentry),
849 NULL, old_dentry);
850 release_dentry_name_snapshot(&old_name);
851 unlock_rename(new_dir, old_dir);
852 dput(dentry);
853 return old_dentry;
854exit:
855 if (dentry && !IS_ERR(dentry))
856 dput(dentry);
857 unlock_rename(new_dir, old_dir);
858 if (IS_ERR(dentry))
859 return dentry;
860 return ERR_PTR(-EINVAL);
861}
862EXPORT_SYMBOL_GPL(debugfs_rename);
863
864/**
865 * debugfs_initialized - Tells whether debugfs has been registered
866 */
867bool debugfs_initialized(void)
868{
869 return debugfs_registered;
870}
871EXPORT_SYMBOL_GPL(debugfs_initialized);
872
873static int __init debugfs_kernel(char *str)
874{
875 if (str) {
876 if (!strcmp(str, "on"))
877 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
878 else if (!strcmp(str, "no-mount"))
879 debugfs_allow = DEBUGFS_ALLOW_API;
880 else if (!strcmp(str, "off"))
881 debugfs_allow = 0;
882 }
883
884 return 0;
885}
886early_param("debugfs", debugfs_kernel);
887static int __init debugfs_init(void)
888{
889 int retval;
890
891 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
892 return -EPERM;
893
894 retval = sysfs_create_mount_point(kernel_kobj, "debug");
895 if (retval)
896 return retval;
897
898 retval = register_filesystem(&debug_fs_type);
899 if (retval)
900 sysfs_remove_mount_point(kernel_kobj, "debug");
901 else
902 debugfs_registered = true;
903
904 return retval;
905}
906core_initcall(debugfs_init);
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 Greg Kroah-Hartman <greg@kroah.com>
6 * Copyright (C) 2004 IBM Inc.
7 *
8 * debugfs is for people to use instead of /proc or /sys.
9 * See ./Documentation/core-api/kernel-api.rst for more details.
10 */
11
12#include <linux/module.h>
13#include <linux/fs.h>
14#include <linux/mount.h>
15#include <linux/pagemap.h>
16#include <linux/init.h>
17#include <linux/kobject.h>
18#include <linux/namei.h>
19#include <linux/debugfs.h>
20#include <linux/fsnotify.h>
21#include <linux/string.h>
22#include <linux/seq_file.h>
23#include <linux/parser.h>
24#include <linux/magic.h>
25#include <linux/slab.h>
26
27#include "internal.h"
28
29#define DEBUGFS_DEFAULT_MODE 0700
30
31static struct vfsmount *debugfs_mount;
32static int debugfs_mount_count;
33static bool debugfs_registered;
34
35static struct inode *debugfs_get_inode(struct super_block *sb)
36{
37 struct inode *inode = new_inode(sb);
38 if (inode) {
39 inode->i_ino = get_next_ino();
40 inode->i_atime = inode->i_mtime =
41 inode->i_ctime = current_time(inode);
42 }
43 return inode;
44}
45
46struct debugfs_mount_opts {
47 kuid_t uid;
48 kgid_t gid;
49 umode_t mode;
50};
51
52enum {
53 Opt_uid,
54 Opt_gid,
55 Opt_mode,
56 Opt_err
57};
58
59static const match_table_t tokens = {
60 {Opt_uid, "uid=%u"},
61 {Opt_gid, "gid=%u"},
62 {Opt_mode, "mode=%o"},
63 {Opt_err, NULL}
64};
65
66struct debugfs_fs_info {
67 struct debugfs_mount_opts mount_opts;
68};
69
70static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
71{
72 substring_t args[MAX_OPT_ARGS];
73 int option;
74 int token;
75 kuid_t uid;
76 kgid_t gid;
77 char *p;
78
79 opts->mode = DEBUGFS_DEFAULT_MODE;
80
81 while ((p = strsep(&data, ",")) != NULL) {
82 if (!*p)
83 continue;
84
85 token = match_token(p, tokens, args);
86 switch (token) {
87 case Opt_uid:
88 if (match_int(&args[0], &option))
89 return -EINVAL;
90 uid = make_kuid(current_user_ns(), option);
91 if (!uid_valid(uid))
92 return -EINVAL;
93 opts->uid = uid;
94 break;
95 case Opt_gid:
96 if (match_int(&args[0], &option))
97 return -EINVAL;
98 gid = make_kgid(current_user_ns(), option);
99 if (!gid_valid(gid))
100 return -EINVAL;
101 opts->gid = gid;
102 break;
103 case Opt_mode:
104 if (match_octal(&args[0], &option))
105 return -EINVAL;
106 opts->mode = option & S_IALLUGO;
107 break;
108 /*
109 * We might like to report bad mount options here;
110 * but traditionally debugfs has ignored all mount options
111 */
112 }
113 }
114
115 return 0;
116}
117
118static int debugfs_apply_options(struct super_block *sb)
119{
120 struct debugfs_fs_info *fsi = sb->s_fs_info;
121 struct inode *inode = d_inode(sb->s_root);
122 struct debugfs_mount_opts *opts = &fsi->mount_opts;
123
124 inode->i_mode &= ~S_IALLUGO;
125 inode->i_mode |= opts->mode;
126
127 inode->i_uid = opts->uid;
128 inode->i_gid = opts->gid;
129
130 return 0;
131}
132
133static int debugfs_remount(struct super_block *sb, int *flags, char *data)
134{
135 int err;
136 struct debugfs_fs_info *fsi = sb->s_fs_info;
137
138 sync_filesystem(sb);
139 err = debugfs_parse_options(data, &fsi->mount_opts);
140 if (err)
141 goto fail;
142
143 debugfs_apply_options(sb);
144
145fail:
146 return err;
147}
148
149static int debugfs_show_options(struct seq_file *m, struct dentry *root)
150{
151 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
152 struct debugfs_mount_opts *opts = &fsi->mount_opts;
153
154 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
155 seq_printf(m, ",uid=%u",
156 from_kuid_munged(&init_user_ns, opts->uid));
157 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
158 seq_printf(m, ",gid=%u",
159 from_kgid_munged(&init_user_ns, opts->gid));
160 if (opts->mode != DEBUGFS_DEFAULT_MODE)
161 seq_printf(m, ",mode=%o", opts->mode);
162
163 return 0;
164}
165
166static void debugfs_evict_inode(struct inode *inode)
167{
168 truncate_inode_pages_final(&inode->i_data);
169 clear_inode(inode);
170 if (S_ISLNK(inode->i_mode))
171 kfree(inode->i_link);
172}
173
174static const struct super_operations debugfs_super_operations = {
175 .statfs = simple_statfs,
176 .remount_fs = debugfs_remount,
177 .show_options = debugfs_show_options,
178 .evict_inode = debugfs_evict_inode,
179};
180
181static void debugfs_release_dentry(struct dentry *dentry)
182{
183 void *fsd = dentry->d_fsdata;
184
185 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
186 kfree(dentry->d_fsdata);
187}
188
189static struct vfsmount *debugfs_automount(struct path *path)
190{
191 debugfs_automount_t f;
192 f = (debugfs_automount_t)path->dentry->d_fsdata;
193 return f(path->dentry, d_inode(path->dentry)->i_private);
194}
195
196static const struct dentry_operations debugfs_dops = {
197 .d_delete = always_delete_dentry,
198 .d_release = debugfs_release_dentry,
199 .d_automount = debugfs_automount,
200};
201
202static int debug_fill_super(struct super_block *sb, void *data, int silent)
203{
204 static const struct tree_descr debug_files[] = {{""}};
205 struct debugfs_fs_info *fsi;
206 int err;
207
208 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
209 sb->s_fs_info = fsi;
210 if (!fsi) {
211 err = -ENOMEM;
212 goto fail;
213 }
214
215 err = debugfs_parse_options(data, &fsi->mount_opts);
216 if (err)
217 goto fail;
218
219 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
220 if (err)
221 goto fail;
222
223 sb->s_op = &debugfs_super_operations;
224 sb->s_d_op = &debugfs_dops;
225
226 debugfs_apply_options(sb);
227
228 return 0;
229
230fail:
231 kfree(fsi);
232 sb->s_fs_info = NULL;
233 return err;
234}
235
236static struct dentry *debug_mount(struct file_system_type *fs_type,
237 int flags, const char *dev_name,
238 void *data)
239{
240 return mount_single(fs_type, flags, data, debug_fill_super);
241}
242
243static struct file_system_type debug_fs_type = {
244 .owner = THIS_MODULE,
245 .name = "debugfs",
246 .mount = debug_mount,
247 .kill_sb = kill_litter_super,
248};
249MODULE_ALIAS_FS("debugfs");
250
251/**
252 * debugfs_lookup() - look up an existing debugfs file
253 * @name: a pointer to a string containing the name of the file to look up.
254 * @parent: a pointer to the parent dentry of the file.
255 *
256 * This function will return a pointer to a dentry if it succeeds. If the file
257 * doesn't exist or an error occurs, %NULL will be returned. The returned
258 * dentry must be passed to dput() when it is no longer needed.
259 *
260 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
261 * returned.
262 */
263struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
264{
265 struct dentry *dentry;
266
267 if (IS_ERR(parent))
268 return NULL;
269
270 if (!parent)
271 parent = debugfs_mount->mnt_root;
272
273 dentry = lookup_one_len_unlocked(name, parent, strlen(name));
274 if (IS_ERR(dentry))
275 return NULL;
276 if (!d_really_is_positive(dentry)) {
277 dput(dentry);
278 return NULL;
279 }
280 return dentry;
281}
282EXPORT_SYMBOL_GPL(debugfs_lookup);
283
284static struct dentry *start_creating(const char *name, struct dentry *parent)
285{
286 struct dentry *dentry;
287 int error;
288
289 pr_debug("debugfs: creating file '%s'\n",name);
290
291 if (IS_ERR(parent))
292 return parent;
293
294 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
295 &debugfs_mount_count);
296 if (error)
297 return ERR_PTR(error);
298
299 /* If the parent is not specified, we create it in the root.
300 * We need the root dentry to do this, which is in the super
301 * block. A pointer to that is in the struct vfsmount that we
302 * have around.
303 */
304 if (!parent)
305 parent = debugfs_mount->mnt_root;
306
307 inode_lock(d_inode(parent));
308 dentry = lookup_one_len(name, parent, strlen(name));
309 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
310 dput(dentry);
311 dentry = ERR_PTR(-EEXIST);
312 }
313
314 if (IS_ERR(dentry)) {
315 inode_unlock(d_inode(parent));
316 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
317 }
318
319 return dentry;
320}
321
322static struct dentry *failed_creating(struct dentry *dentry)
323{
324 inode_unlock(d_inode(dentry->d_parent));
325 dput(dentry);
326 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
327 return NULL;
328}
329
330static struct dentry *end_creating(struct dentry *dentry)
331{
332 inode_unlock(d_inode(dentry->d_parent));
333 return dentry;
334}
335
336static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
337 struct dentry *parent, void *data,
338 const struct file_operations *proxy_fops,
339 const struct file_operations *real_fops)
340{
341 struct dentry *dentry;
342 struct inode *inode;
343
344 if (!(mode & S_IFMT))
345 mode |= S_IFREG;
346 BUG_ON(!S_ISREG(mode));
347 dentry = start_creating(name, parent);
348
349 if (IS_ERR(dentry))
350 return NULL;
351
352 inode = debugfs_get_inode(dentry->d_sb);
353 if (unlikely(!inode))
354 return failed_creating(dentry);
355
356 inode->i_mode = mode;
357 inode->i_private = data;
358
359 inode->i_fop = proxy_fops;
360 dentry->d_fsdata = (void *)((unsigned long)real_fops |
361 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
362
363 d_instantiate(dentry, inode);
364 fsnotify_create(d_inode(dentry->d_parent), dentry);
365 return end_creating(dentry);
366}
367
368/**
369 * debugfs_create_file - create a file in the debugfs filesystem
370 * @name: a pointer to a string containing the name of the file to create.
371 * @mode: the permission that the file should have.
372 * @parent: a pointer to the parent dentry for this file. This should be a
373 * directory dentry if set. If this parameter is NULL, then the
374 * file will be created in the root of the debugfs filesystem.
375 * @data: a pointer to something that the caller will want to get to later
376 * on. The inode.i_private pointer will point to this value on
377 * the open() call.
378 * @fops: a pointer to a struct file_operations that should be used for
379 * this file.
380 *
381 * This is the basic "create a file" function for debugfs. It allows for a
382 * wide range of flexibility in creating a file, or a directory (if you want
383 * to create a directory, the debugfs_create_dir() function is
384 * recommended to be used instead.)
385 *
386 * This function will return a pointer to a dentry if it succeeds. This
387 * pointer must be passed to the debugfs_remove() function when the file is
388 * to be removed (no automatic cleanup happens if your module is unloaded,
389 * you are responsible here.) If an error occurs, %NULL will be returned.
390 *
391 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
392 * returned.
393 */
394struct dentry *debugfs_create_file(const char *name, umode_t mode,
395 struct dentry *parent, void *data,
396 const struct file_operations *fops)
397{
398
399 return __debugfs_create_file(name, mode, parent, data,
400 fops ? &debugfs_full_proxy_file_operations :
401 &debugfs_noop_file_operations,
402 fops);
403}
404EXPORT_SYMBOL_GPL(debugfs_create_file);
405
406/**
407 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
408 * @name: a pointer to a string containing the name of the file to create.
409 * @mode: the permission that the file should have.
410 * @parent: a pointer to the parent dentry for this file. This should be a
411 * directory dentry if set. If this parameter is NULL, then the
412 * file will be created in the root of the debugfs filesystem.
413 * @data: a pointer to something that the caller will want to get to later
414 * on. The inode.i_private pointer will point to this value on
415 * the open() call.
416 * @fops: a pointer to a struct file_operations that should be used for
417 * this file.
418 *
419 * debugfs_create_file_unsafe() is completely analogous to
420 * debugfs_create_file(), the only difference being that the fops
421 * handed it will not get protected against file removals by the
422 * debugfs core.
423 *
424 * It is your responsibility to protect your struct file_operation
425 * methods against file removals by means of debugfs_use_file_start()
426 * and debugfs_use_file_finish(). ->open() is still protected by
427 * debugfs though.
428 *
429 * Any struct file_operations defined by means of
430 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
431 * thus, may be used here.
432 */
433struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
434 struct dentry *parent, void *data,
435 const struct file_operations *fops)
436{
437
438 return __debugfs_create_file(name, mode, parent, data,
439 fops ? &debugfs_open_proxy_file_operations :
440 &debugfs_noop_file_operations,
441 fops);
442}
443EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
444
445/**
446 * debugfs_create_file_size - create a file in the debugfs filesystem
447 * @name: a pointer to a string containing the name of the file to create.
448 * @mode: the permission that the file should have.
449 * @parent: a pointer to the parent dentry for this file. This should be a
450 * directory dentry if set. If this parameter is NULL, then the
451 * file will be created in the root of the debugfs filesystem.
452 * @data: a pointer to something that the caller will want to get to later
453 * on. The inode.i_private pointer will point to this value on
454 * the open() call.
455 * @fops: a pointer to a struct file_operations that should be used for
456 * this file.
457 * @file_size: initial file size
458 *
459 * This is the basic "create a file" function for debugfs. It allows for a
460 * wide range of flexibility in creating a file, or a directory (if you want
461 * to create a directory, the debugfs_create_dir() function is
462 * recommended to be used instead.)
463 *
464 * This function will return a pointer to a dentry if it succeeds. This
465 * pointer must be passed to the debugfs_remove() function when the file is
466 * to be removed (no automatic cleanup happens if your module is unloaded,
467 * you are responsible here.) If an error occurs, %NULL will be returned.
468 *
469 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
470 * returned.
471 */
472struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
473 struct dentry *parent, void *data,
474 const struct file_operations *fops,
475 loff_t file_size)
476{
477 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
478
479 if (de)
480 d_inode(de)->i_size = file_size;
481 return de;
482}
483EXPORT_SYMBOL_GPL(debugfs_create_file_size);
484
485/**
486 * debugfs_create_dir - create a directory in the debugfs filesystem
487 * @name: a pointer to a string containing the name of the directory to
488 * create.
489 * @parent: a pointer to the parent dentry for this file. This should be a
490 * directory dentry if set. If this parameter is NULL, then the
491 * directory will be created in the root of the debugfs filesystem.
492 *
493 * This function creates a directory in debugfs with the given name.
494 *
495 * This function will return a pointer to a dentry if it succeeds. This
496 * pointer must be passed to the debugfs_remove() function when the file is
497 * to be removed (no automatic cleanup happens if your module is unloaded,
498 * you are responsible here.) If an error occurs, %NULL will be returned.
499 *
500 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
501 * returned.
502 */
503struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
504{
505 struct dentry *dentry = start_creating(name, parent);
506 struct inode *inode;
507
508 if (IS_ERR(dentry))
509 return NULL;
510
511 inode = debugfs_get_inode(dentry->d_sb);
512 if (unlikely(!inode))
513 return failed_creating(dentry);
514
515 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
516 inode->i_op = &simple_dir_inode_operations;
517 inode->i_fop = &simple_dir_operations;
518
519 /* directory inodes start off with i_nlink == 2 (for "." entry) */
520 inc_nlink(inode);
521 d_instantiate(dentry, inode);
522 inc_nlink(d_inode(dentry->d_parent));
523 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
524 return end_creating(dentry);
525}
526EXPORT_SYMBOL_GPL(debugfs_create_dir);
527
528/**
529 * debugfs_create_automount - create automount point in the debugfs filesystem
530 * @name: a pointer to a string containing the name of the file to create.
531 * @parent: a pointer to the parent dentry for this file. This should be a
532 * directory dentry if set. If this parameter is NULL, then the
533 * file will be created in the root of the debugfs filesystem.
534 * @f: function to be called when pathname resolution steps on that one.
535 * @data: opaque argument to pass to f().
536 *
537 * @f should return what ->d_automount() would.
538 */
539struct dentry *debugfs_create_automount(const char *name,
540 struct dentry *parent,
541 debugfs_automount_t f,
542 void *data)
543{
544 struct dentry *dentry = start_creating(name, parent);
545 struct inode *inode;
546
547 if (IS_ERR(dentry))
548 return NULL;
549
550 inode = debugfs_get_inode(dentry->d_sb);
551 if (unlikely(!inode))
552 return failed_creating(dentry);
553
554 make_empty_dir_inode(inode);
555 inode->i_flags |= S_AUTOMOUNT;
556 inode->i_private = data;
557 dentry->d_fsdata = (void *)f;
558 /* directory inodes start off with i_nlink == 2 (for "." entry) */
559 inc_nlink(inode);
560 d_instantiate(dentry, inode);
561 inc_nlink(d_inode(dentry->d_parent));
562 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
563 return end_creating(dentry);
564}
565EXPORT_SYMBOL(debugfs_create_automount);
566
567/**
568 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
569 * @name: a pointer to a string containing the name of the symbolic link to
570 * create.
571 * @parent: a pointer to the parent dentry for this symbolic link. This
572 * should be a directory dentry if set. If this parameter is NULL,
573 * then the symbolic link will be created in the root of the debugfs
574 * filesystem.
575 * @target: a pointer to a string containing the path to the target of the
576 * symbolic link.
577 *
578 * This function creates a symbolic link with the given name in debugfs that
579 * links to the given target path.
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 symbolic
583 * link is to be removed (no automatic cleanup happens if your module is
584 * unloaded, you are responsible here.) If an error occurs, %NULL will be
585 * returned.
586 *
587 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
588 * returned.
589 */
590struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
591 const char *target)
592{
593 struct dentry *dentry;
594 struct inode *inode;
595 char *link = kstrdup(target, GFP_KERNEL);
596 if (!link)
597 return NULL;
598
599 dentry = start_creating(name, parent);
600 if (IS_ERR(dentry)) {
601 kfree(link);
602 return NULL;
603 }
604
605 inode = debugfs_get_inode(dentry->d_sb);
606 if (unlikely(!inode)) {
607 kfree(link);
608 return failed_creating(dentry);
609 }
610 inode->i_mode = S_IFLNK | S_IRWXUGO;
611 inode->i_op = &simple_symlink_inode_operations;
612 inode->i_link = link;
613 d_instantiate(dentry, inode);
614 return end_creating(dentry);
615}
616EXPORT_SYMBOL_GPL(debugfs_create_symlink);
617
618static void __debugfs_remove_file(struct dentry *dentry, struct dentry *parent)
619{
620 struct debugfs_fsdata *fsd;
621
622 simple_unlink(d_inode(parent), dentry);
623 d_delete(dentry);
624
625 /*
626 * Paired with the closing smp_mb() implied by a successful
627 * cmpxchg() in debugfs_file_get(): either
628 * debugfs_file_get() must see a dead dentry or we must see a
629 * debugfs_fsdata instance at ->d_fsdata here (or both).
630 */
631 smp_mb();
632 fsd = READ_ONCE(dentry->d_fsdata);
633 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
634 return;
635 if (!refcount_dec_and_test(&fsd->active_users))
636 wait_for_completion(&fsd->active_users_drained);
637}
638
639static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
640{
641 int ret = 0;
642
643 if (simple_positive(dentry)) {
644 dget(dentry);
645 if (!d_is_reg(dentry)) {
646 if (d_is_dir(dentry))
647 ret = simple_rmdir(d_inode(parent), dentry);
648 else
649 simple_unlink(d_inode(parent), dentry);
650 if (!ret)
651 d_delete(dentry);
652 } else {
653 __debugfs_remove_file(dentry, parent);
654 }
655 dput(dentry);
656 }
657 return ret;
658}
659
660/**
661 * debugfs_remove - removes a file or directory from the debugfs filesystem
662 * @dentry: a pointer to a the dentry of the file or directory to be
663 * removed. If this parameter is NULL or an error value, nothing
664 * will be done.
665 *
666 * This function removes a file or directory in debugfs that was previously
667 * created with a call to another debugfs function (like
668 * debugfs_create_file() or variants thereof.)
669 *
670 * This function is required to be called in order for the file to be
671 * removed, no automatic cleanup of files will happen when a module is
672 * removed, you are responsible here.
673 */
674void debugfs_remove(struct dentry *dentry)
675{
676 struct dentry *parent;
677 int ret;
678
679 if (IS_ERR_OR_NULL(dentry))
680 return;
681
682 parent = dentry->d_parent;
683 inode_lock(d_inode(parent));
684 ret = __debugfs_remove(dentry, parent);
685 inode_unlock(d_inode(parent));
686 if (!ret)
687 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
688}
689EXPORT_SYMBOL_GPL(debugfs_remove);
690
691/**
692 * debugfs_remove_recursive - recursively removes a directory
693 * @dentry: a pointer to a the dentry of the directory to be removed. If this
694 * parameter is NULL or an error value, nothing will be done.
695 *
696 * This function recursively removes a directory tree in debugfs that
697 * was previously created with a call to another debugfs function
698 * (like debugfs_create_file() or variants thereof.)
699 *
700 * This function is required to be called in order for the file to be
701 * removed, no automatic cleanup of files will happen when a module is
702 * removed, you are responsible here.
703 */
704void debugfs_remove_recursive(struct dentry *dentry)
705{
706 struct dentry *child, *parent;
707
708 if (IS_ERR_OR_NULL(dentry))
709 return;
710
711 parent = dentry;
712 down:
713 inode_lock(d_inode(parent));
714 loop:
715 /*
716 * The parent->d_subdirs is protected by the d_lock. Outside that
717 * lock, the child can be unlinked and set to be freed which can
718 * use the d_u.d_child as the rcu head and corrupt this list.
719 */
720 spin_lock(&parent->d_lock);
721 list_for_each_entry(child, &parent->d_subdirs, d_child) {
722 if (!simple_positive(child))
723 continue;
724
725 /* perhaps simple_empty(child) makes more sense */
726 if (!list_empty(&child->d_subdirs)) {
727 spin_unlock(&parent->d_lock);
728 inode_unlock(d_inode(parent));
729 parent = child;
730 goto down;
731 }
732
733 spin_unlock(&parent->d_lock);
734
735 if (!__debugfs_remove(child, parent))
736 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
737
738 /*
739 * The parent->d_lock protects agaist child from unlinking
740 * from d_subdirs. When releasing the parent->d_lock we can
741 * no longer trust that the next pointer is valid.
742 * Restart the loop. We'll skip this one with the
743 * simple_positive() check.
744 */
745 goto loop;
746 }
747 spin_unlock(&parent->d_lock);
748
749 inode_unlock(d_inode(parent));
750 child = parent;
751 parent = parent->d_parent;
752 inode_lock(d_inode(parent));
753
754 if (child != dentry)
755 /* go up */
756 goto loop;
757
758 if (!__debugfs_remove(child, parent))
759 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
760 inode_unlock(d_inode(parent));
761}
762EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
763
764/**
765 * debugfs_rename - rename a file/directory in the debugfs filesystem
766 * @old_dir: a pointer to the parent dentry for the renamed object. This
767 * should be a directory dentry.
768 * @old_dentry: dentry of an object to be renamed.
769 * @new_dir: a pointer to the parent dentry where the object should be
770 * moved. This should be a directory dentry.
771 * @new_name: a pointer to a string containing the target name.
772 *
773 * This function renames a file/directory in debugfs. The target must not
774 * exist for rename to succeed.
775 *
776 * This function will return a pointer to old_dentry (which is updated to
777 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
778 * returned.
779 *
780 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
781 * returned.
782 */
783struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
784 struct dentry *new_dir, const char *new_name)
785{
786 int error;
787 struct dentry *dentry = NULL, *trap;
788 struct name_snapshot old_name;
789
790 trap = lock_rename(new_dir, old_dir);
791 /* Source or destination directories don't exist? */
792 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
793 goto exit;
794 /* Source does not exist, cyclic rename, or mountpoint? */
795 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
796 d_mountpoint(old_dentry))
797 goto exit;
798 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
799 /* Lookup failed, cyclic rename or target exists? */
800 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
801 goto exit;
802
803 take_dentry_name_snapshot(&old_name, old_dentry);
804
805 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
806 dentry, 0);
807 if (error) {
808 release_dentry_name_snapshot(&old_name);
809 goto exit;
810 }
811 d_move(old_dentry, dentry);
812 fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name.name,
813 d_is_dir(old_dentry),
814 NULL, old_dentry);
815 release_dentry_name_snapshot(&old_name);
816 unlock_rename(new_dir, old_dir);
817 dput(dentry);
818 return old_dentry;
819exit:
820 if (dentry && !IS_ERR(dentry))
821 dput(dentry);
822 unlock_rename(new_dir, old_dir);
823 return NULL;
824}
825EXPORT_SYMBOL_GPL(debugfs_rename);
826
827/**
828 * debugfs_initialized - Tells whether debugfs has been registered
829 */
830bool debugfs_initialized(void)
831{
832 return debugfs_registered;
833}
834EXPORT_SYMBOL_GPL(debugfs_initialized);
835
836static int __init debugfs_init(void)
837{
838 int retval;
839
840 retval = sysfs_create_mount_point(kernel_kobj, "debug");
841 if (retval)
842 return retval;
843
844 retval = register_filesystem(&debug_fs_type);
845 if (retval)
846 sysfs_remove_mount_point(kernel_kobj, "debug");
847 else
848 debugfs_registered = true;
849
850 return retval;
851}
852core_initcall(debugfs_init);
853