1// SPDX-License-Identifier: GPL-2.0
2/*
3 * inode.c - part of debugfs, a tiny little debug file system
4 *
5 * Copyright (C) 2004,2019 Greg Kroah-Hartman <greg@kroah.com>
6 * Copyright (C) 2004 IBM Inc.
7 * Copyright (C) 2019 Linux Foundation <gregkh@linuxfoundation.org>
8 *
9 * debugfs is for people to use instead of /proc or /sys.
10 * See ./Documentation/core-api/kernel-api.rst for more details.
11 */
12
13#define pr_fmt(fmt) "debugfs: " fmt
14
15#include <linux/module.h>
16#include <linux/fs.h>
17#include <linux/mount.h>
18#include <linux/pagemap.h>
19#include <linux/init.h>
20#include <linux/kobject.h>
21#include <linux/namei.h>
22#include <linux/debugfs.h>
23#include <linux/fsnotify.h>
24#include <linux/string.h>
25#include <linux/seq_file.h>
26#include <linux/parser.h>
27#include <linux/magic.h>
28#include <linux/slab.h>
29#include <linux/security.h>
30
31#include "internal.h"
32
33#define DEBUGFS_DEFAULT_MODE 0700
34
35static struct vfsmount *debugfs_mount;
36static int debugfs_mount_count;
37static bool debugfs_registered;
38static unsigned int debugfs_allow __ro_after_init = DEFAULT_DEBUGFS_ALLOW_BITS;
39
40/*
41 * Don't allow access attributes to be changed whilst the kernel is locked down
42 * so that we can use the file mode as part of a heuristic to determine whether
43 * to lock down individual files.
44 */
45static int debugfs_setattr(struct mnt_idmap *idmap,
46 struct dentry *dentry, struct iattr *ia)
47{
48 int ret;
49
50 if (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) {
51 ret = security_locked_down(what: LOCKDOWN_DEBUGFS);
52 if (ret)
53 return ret;
54 }
55 return simple_setattr(&nop_mnt_idmap, dentry, ia);
56}
57
58static const struct inode_operations debugfs_file_inode_operations = {
59 .setattr = debugfs_setattr,
60};
61static const struct inode_operations debugfs_dir_inode_operations = {
62 .lookup = simple_lookup,
63 .setattr = debugfs_setattr,
64};
65static const struct inode_operations debugfs_symlink_inode_operations = {
66 .get_link = simple_get_link,
67 .setattr = debugfs_setattr,
68};
69
70static struct inode *debugfs_get_inode(struct super_block *sb)
71{
72 struct inode *inode = new_inode(sb);
73 if (inode) {
74 inode->i_ino = get_next_ino();
75 simple_inode_init_ts(inode);
76 }
77 return inode;
78}
79
80struct debugfs_mount_opts {
81 kuid_t uid;
82 kgid_t gid;
83 umode_t mode;
84 /* Opt_* bitfield. */
85 unsigned int opts;
86};
87
88enum {
89 Opt_uid,
90 Opt_gid,
91 Opt_mode,
92 Opt_err
93};
94
95static const match_table_t tokens = {
96 {Opt_uid, "uid=%u"},
97 {Opt_gid, "gid=%u"},
98 {Opt_mode, "mode=%o"},
99 {Opt_err, NULL}
100};
101
102struct debugfs_fs_info {
103 struct debugfs_mount_opts mount_opts;
104};
105
106static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
107{
108 substring_t args[MAX_OPT_ARGS];
109 int option;
110 int token;
111 kuid_t uid;
112 kgid_t gid;
113 char *p;
114
115 opts->opts = 0;
116 opts->mode = DEBUGFS_DEFAULT_MODE;
117
118 while ((p = strsep(&data, ",")) != NULL) {
119 if (!*p)
120 continue;
121
122 token = match_token(p, table: tokens, args);
123 switch (token) {
124 case Opt_uid:
125 if (match_int(&args[0], result: &option))
126 return -EINVAL;
127 uid = make_kuid(current_user_ns(), uid: option);
128 if (!uid_valid(uid))
129 return -EINVAL;
130 opts->uid = uid;
131 break;
132 case Opt_gid:
133 if (match_int(&args[0], result: &option))
134 return -EINVAL;
135 gid = make_kgid(current_user_ns(), gid: option);
136 if (!gid_valid(gid))
137 return -EINVAL;
138 opts->gid = gid;
139 break;
140 case Opt_mode:
141 if (match_octal(&args[0], result: &option))
142 return -EINVAL;
143 opts->mode = option & S_IALLUGO;
144 break;
145 /*
146 * We might like to report bad mount options here;
147 * but traditionally debugfs has ignored all mount options
148 */
149 }
150
151 opts->opts |= BIT(token);
152 }
153
154 return 0;
155}
156
157static void _debugfs_apply_options(struct super_block *sb, bool remount)
158{
159 struct debugfs_fs_info *fsi = sb->s_fs_info;
160 struct inode *inode = d_inode(dentry: sb->s_root);
161 struct debugfs_mount_opts *opts = &fsi->mount_opts;
162
163 /*
164 * On remount, only reset mode/uid/gid if they were provided as mount
165 * options.
166 */
167
168 if (!remount || opts->opts & BIT(Opt_mode)) {
169 inode->i_mode &= ~S_IALLUGO;
170 inode->i_mode |= opts->mode;
171 }
172
173 if (!remount || opts->opts & BIT(Opt_uid))
174 inode->i_uid = opts->uid;
175
176 if (!remount || opts->opts & BIT(Opt_gid))
177 inode->i_gid = opts->gid;
178}
179
180static void debugfs_apply_options(struct super_block *sb)
181{
182 _debugfs_apply_options(sb, remount: false);
183}
184
185static void debugfs_apply_options_remount(struct super_block *sb)
186{
187 _debugfs_apply_options(sb, remount: true);
188}
189
190static int debugfs_remount(struct super_block *sb, int *flags, char *data)
191{
192 int err;
193 struct debugfs_fs_info *fsi = sb->s_fs_info;
194
195 sync_filesystem(sb);
196 err = debugfs_parse_options(data, opts: &fsi->mount_opts);
197 if (err)
198 goto fail;
199
200 debugfs_apply_options_remount(sb);
201
202fail:
203 return err;
204}
205
206static int debugfs_show_options(struct seq_file *m, struct dentry *root)
207{
208 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
209 struct debugfs_mount_opts *opts = &fsi->mount_opts;
210
211 if (!uid_eq(left: opts->uid, GLOBAL_ROOT_UID))
212 seq_printf(m, ",uid=%u",
213 from_kuid_munged(&init_user_ns, opts->uid));
214 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
215 seq_printf(m, ",gid=%u",
216 from_kgid_munged(&init_user_ns, opts->gid));
217 if (opts->mode != DEBUGFS_DEFAULT_MODE)
218 seq_printf(m, ",mode=%o", opts->mode);
219
220 return 0;
221}
222
223static void debugfs_free_inode(struct inode *inode)
224{
225 if (S_ISLNK(inode->i_mode))
226 kfree(objp: inode->i_link);
227 free_inode_nonrcu(inode);
228}
229
230static const struct super_operations debugfs_super_operations = {
231 .statfs = simple_statfs,
232 .remount_fs = debugfs_remount,
233 .show_options = debugfs_show_options,
234 .free_inode = debugfs_free_inode,
235};
236
237static void debugfs_release_dentry(struct dentry *dentry)
238{
239 void *fsd = dentry->d_fsdata;
240
241 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
242 kfree(objp: dentry->d_fsdata);
243}
244
245static struct vfsmount *debugfs_automount(struct path *path)
246{
247 debugfs_automount_t f;
248 f = (debugfs_automount_t)path->dentry->d_fsdata;
249 return f(path->dentry, d_inode(dentry: path->dentry)->i_private);
250}
251
252static const struct dentry_operations debugfs_dops = {
253 .d_delete = always_delete_dentry,
254 .d_release = debugfs_release_dentry,
255 .d_automount = debugfs_automount,
256};
257
258static int debug_fill_super(struct super_block *sb, void *data, int silent)
259{
260 static const struct tree_descr debug_files[] = {{""}};
261 struct debugfs_fs_info *fsi;
262 int err;
263
264 fsi = kzalloc(size: sizeof(struct debugfs_fs_info), GFP_KERNEL);
265 sb->s_fs_info = fsi;
266 if (!fsi) {
267 err = -ENOMEM;
268 goto fail;
269 }
270
271 err = debugfs_parse_options(data, opts: &fsi->mount_opts);
272 if (err)
273 goto fail;
274
275 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
276 if (err)
277 goto fail;
278
279 sb->s_op = &debugfs_super_operations;
280 sb->s_d_op = &debugfs_dops;
281
282 debugfs_apply_options(sb);
283
284 return 0;
285
286fail:
287 kfree(objp: fsi);
288 sb->s_fs_info = NULL;
289 return err;
290}
291
292static struct dentry *debug_mount(struct file_system_type *fs_type,
293 int flags, const char *dev_name,
294 void *data)
295{
296 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
297 return ERR_PTR(error: -EPERM);
298
299 return mount_single(fs_type, flags, data, fill_super: debug_fill_super);
300}
301
302static struct file_system_type debug_fs_type = {
303 .owner = THIS_MODULE,
304 .name = "debugfs",
305 .mount = debug_mount,
306 .kill_sb = kill_litter_super,
307};
308MODULE_ALIAS_FS("debugfs");
309
310/**
311 * debugfs_lookup() - look up an existing debugfs file
312 * @name: a pointer to a string containing the name of the file to look up.
313 * @parent: a pointer to the parent dentry of the file.
314 *
315 * This function will return a pointer to a dentry if it succeeds. If the file
316 * doesn't exist or an error occurs, %NULL will be returned. The returned
317 * dentry must be passed to dput() when it is no longer needed.
318 *
319 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
320 * returned.
321 */
322struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
323{
324 struct dentry *dentry;
325
326 if (!debugfs_initialized() || IS_ERR_OR_NULL(ptr: name) || IS_ERR(ptr: parent))
327 return NULL;
328
329 if (!parent)
330 parent = debugfs_mount->mnt_root;
331
332 dentry = lookup_positive_unlocked(name, parent, strlen(name));
333 if (IS_ERR(ptr: dentry))
334 return NULL;
335 return dentry;
336}
337EXPORT_SYMBOL_GPL(debugfs_lookup);
338
339static struct dentry *start_creating(const char *name, struct dentry *parent)
340{
341 struct dentry *dentry;
342 int error;
343
344 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
345 return ERR_PTR(error: -EPERM);
346
347 if (!debugfs_initialized())
348 return ERR_PTR(error: -ENOENT);
349
350 pr_debug("creating file '%s'\n", name);
351
352 if (IS_ERR(ptr: parent))
353 return parent;
354
355 error = simple_pin_fs(&debug_fs_type, mount: &debugfs_mount,
356 count: &debugfs_mount_count);
357 if (error) {
358 pr_err("Unable to pin filesystem for file '%s'\n", name);
359 return ERR_PTR(error);
360 }
361
362 /* If the parent is not specified, we create it in the root.
363 * We need the root dentry to do this, which is in the super
364 * block. A pointer to that is in the struct vfsmount that we
365 * have around.
366 */
367 if (!parent)
368 parent = debugfs_mount->mnt_root;
369
370 inode_lock(inode: d_inode(dentry: parent));
371 if (unlikely(IS_DEADDIR(d_inode(parent))))
372 dentry = ERR_PTR(error: -ENOENT);
373 else
374 dentry = lookup_one_len(name, parent, strlen(name));
375 if (!IS_ERR(ptr: dentry) && d_really_is_positive(dentry)) {
376 if (d_is_dir(dentry))
377 pr_err("Directory '%s' with parent '%s' already present!\n",
378 name, parent->d_name.name);
379 else
380 pr_err("File '%s' in directory '%s' already present!\n",
381 name, parent->d_name.name);
382 dput(dentry);
383 dentry = ERR_PTR(error: -EEXIST);
384 }
385
386 if (IS_ERR(ptr: dentry)) {
387 inode_unlock(inode: d_inode(dentry: parent));
388 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
389 }
390
391 return dentry;
392}
393
394static struct dentry *failed_creating(struct dentry *dentry)
395{
396 inode_unlock(inode: d_inode(dentry: dentry->d_parent));
397 dput(dentry);
398 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
399 return ERR_PTR(error: -ENOMEM);
400}
401
402static struct dentry *end_creating(struct dentry *dentry)
403{
404 inode_unlock(inode: d_inode(dentry: dentry->d_parent));
405 return dentry;
406}
407
408static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
409 struct dentry *parent, void *data,
410 const struct file_operations *proxy_fops,
411 const struct file_operations *real_fops)
412{
413 struct dentry *dentry;
414 struct inode *inode;
415
416 if (!(mode & S_IFMT))
417 mode |= S_IFREG;
418 BUG_ON(!S_ISREG(mode));
419 dentry = start_creating(name, parent);
420
421 if (IS_ERR(ptr: dentry))
422 return dentry;
423
424 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
425 failed_creating(dentry);
426 return ERR_PTR(error: -EPERM);
427 }
428
429 inode = debugfs_get_inode(sb: dentry->d_sb);
430 if (unlikely(!inode)) {
431 pr_err("out of free dentries, can not create file '%s'\n",
432 name);
433 return failed_creating(dentry);
434 }
435
436 inode->i_mode = mode;
437 inode->i_private = data;
438
439 inode->i_op = &debugfs_file_inode_operations;
440 inode->i_fop = proxy_fops;
441 dentry->d_fsdata = (void *)((unsigned long)real_fops |
442 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
443
444 d_instantiate(dentry, inode);
445 fsnotify_create(dir: d_inode(dentry: dentry->d_parent), dentry);
446 return end_creating(dentry);
447}
448
449/**
450 * debugfs_create_file - create a file in the debugfs filesystem
451 * @name: a pointer to a string containing the name of the file to create.
452 * @mode: the permission that the file should have.
453 * @parent: a pointer to the parent dentry for this file. This should be a
454 * directory dentry if set. If this parameter is NULL, then the
455 * file will be created in the root of the debugfs filesystem.
456 * @data: a pointer to something that the caller will want to get to later
457 * on. The inode.i_private pointer will point to this value on
458 * the open() call.
459 * @fops: a pointer to a struct file_operations that should be used for
460 * this file.
461 *
462 * This is the basic "create a file" function for debugfs. It allows for a
463 * wide range of flexibility in creating a file, or a directory (if you want
464 * to create a directory, the debugfs_create_dir() function is
465 * recommended to be used instead.)
466 *
467 * This function will return a pointer to a dentry if it succeeds. This
468 * pointer must be passed to the debugfs_remove() function when the file is
469 * to be removed (no automatic cleanup happens if your module is unloaded,
470 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
471 * returned.
472 *
473 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
474 * returned.
475 *
476 * NOTE: it's expected that most callers should _ignore_ the errors returned
477 * by this function. Other debugfs functions handle the fact that the "dentry"
478 * passed to them could be an error and they don't crash in that case.
479 * Drivers should generally work fine even if debugfs fails to init anyway.
480 */
481struct dentry *debugfs_create_file(const char *name, umode_t mode,
482 struct dentry *parent, void *data,
483 const struct file_operations *fops)
484{
485
486 return __debugfs_create_file(name, mode, parent, data,
487 proxy_fops: fops ? &debugfs_full_proxy_file_operations :
488 &debugfs_noop_file_operations,
489 real_fops: fops);
490}
491EXPORT_SYMBOL_GPL(debugfs_create_file);
492
493/**
494 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
495 * @name: a pointer to a string containing the name of the file to create.
496 * @mode: the permission that the file should have.
497 * @parent: a pointer to the parent dentry for this file. This should be a
498 * directory dentry if set. If this parameter is NULL, then the
499 * file will be created in the root of the debugfs filesystem.
500 * @data: a pointer to something that the caller will want to get to later
501 * on. The inode.i_private pointer will point to this value on
502 * the open() call.
503 * @fops: a pointer to a struct file_operations that should be used for
504 * this file.
505 *
506 * debugfs_create_file_unsafe() is completely analogous to
507 * debugfs_create_file(), the only difference being that the fops
508 * handed it will not get protected against file removals by the
509 * debugfs core.
510 *
511 * It is your responsibility to protect your struct file_operation
512 * methods against file removals by means of debugfs_file_get()
513 * and debugfs_file_put(). ->open() is still protected by
514 * debugfs though.
515 *
516 * Any struct file_operations defined by means of
517 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
518 * thus, may be used here.
519 */
520struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
521 struct dentry *parent, void *data,
522 const struct file_operations *fops)
523{
524
525 return __debugfs_create_file(name, mode, parent, data,
526 proxy_fops: fops ? &debugfs_open_proxy_file_operations :
527 &debugfs_noop_file_operations,
528 real_fops: fops);
529}
530EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
531
532/**
533 * debugfs_create_file_size - create a file in the debugfs filesystem
534 * @name: a pointer to a string containing the name of the file to create.
535 * @mode: the permission that the file should have.
536 * @parent: a pointer to the parent dentry for this file. This should be a
537 * directory dentry if set. If this parameter is NULL, then the
538 * file will be created in the root of the debugfs filesystem.
539 * @data: a pointer to something that the caller will want to get to later
540 * on. The inode.i_private pointer will point to this value on
541 * the open() call.
542 * @fops: a pointer to a struct file_operations that should be used for
543 * this file.
544 * @file_size: initial file size
545 *
546 * This is the basic "create a file" function for debugfs. It allows for a
547 * wide range of flexibility in creating a file, or a directory (if you want
548 * to create a directory, the debugfs_create_dir() function is
549 * recommended to be used instead.)
550 */
551void debugfs_create_file_size(const char *name, umode_t mode,
552 struct dentry *parent, void *data,
553 const struct file_operations *fops,
554 loff_t file_size)
555{
556 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
557
558 if (!IS_ERR(ptr: de))
559 d_inode(dentry: de)->i_size = file_size;
560}
561EXPORT_SYMBOL_GPL(debugfs_create_file_size);
562
563/**
564 * debugfs_create_dir - create a directory in the debugfs filesystem
565 * @name: a pointer to a string containing the name of the directory to
566 * create.
567 * @parent: a pointer to the parent dentry for this file. This should be a
568 * directory dentry if set. If this parameter is NULL, then the
569 * directory will be created in the root of the debugfs filesystem.
570 *
571 * This function creates a directory in debugfs with the given name.
572 *
573 * This function will return a pointer to a dentry if it succeeds. This
574 * pointer must be passed to the debugfs_remove() function when the file is
575 * to be removed (no automatic cleanup happens if your module is unloaded,
576 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
577 * returned.
578 *
579 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
580 * returned.
581 *
582 * NOTE: it's expected that most callers should _ignore_ the errors returned
583 * by this function. Other debugfs functions handle the fact that the "dentry"
584 * passed to them could be an error and they don't crash in that case.
585 * Drivers should generally work fine even if debugfs fails to init anyway.
586 */
587struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
588{
589 struct dentry *dentry = start_creating(name, parent);
590 struct inode *inode;
591
592 if (IS_ERR(ptr: dentry))
593 return dentry;
594
595 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
596 failed_creating(dentry);
597 return ERR_PTR(error: -EPERM);
598 }
599
600 inode = debugfs_get_inode(sb: dentry->d_sb);
601 if (unlikely(!inode)) {
602 pr_err("out of free dentries, can not create directory '%s'\n",
603 name);
604 return failed_creating(dentry);
605 }
606
607 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
608 inode->i_op = &debugfs_dir_inode_operations;
609 inode->i_fop = &simple_dir_operations;
610
611 /* directory inodes start off with i_nlink == 2 (for "." entry) */
612 inc_nlink(inode);
613 d_instantiate(dentry, inode);
614 inc_nlink(inode: d_inode(dentry: dentry->d_parent));
615 fsnotify_mkdir(dir: d_inode(dentry: dentry->d_parent), dentry);
616 return end_creating(dentry);
617}
618EXPORT_SYMBOL_GPL(debugfs_create_dir);
619
620/**
621 * debugfs_create_automount - create automount point in the debugfs filesystem
622 * @name: a pointer to a string containing the name of the file to create.
623 * @parent: a pointer to the parent dentry for this file. This should be a
624 * directory dentry if set. If this parameter is NULL, then the
625 * file will be created in the root of the debugfs filesystem.
626 * @f: function to be called when pathname resolution steps on that one.
627 * @data: opaque argument to pass to f().
628 *
629 * @f should return what ->d_automount() would.
630 */
631struct dentry *debugfs_create_automount(const char *name,
632 struct dentry *parent,
633 debugfs_automount_t f,
634 void *data)
635{
636 struct dentry *dentry = start_creating(name, parent);
637 struct inode *inode;
638
639 if (IS_ERR(ptr: dentry))
640 return dentry;
641
642 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
643 failed_creating(dentry);
644 return ERR_PTR(error: -EPERM);
645 }
646
647 inode = debugfs_get_inode(sb: dentry->d_sb);
648 if (unlikely(!inode)) {
649 pr_err("out of free dentries, can not create automount '%s'\n",
650 name);
651 return failed_creating(dentry);
652 }
653
654 make_empty_dir_inode(inode);
655 inode->i_flags |= S_AUTOMOUNT;
656 inode->i_private = data;
657 dentry->d_fsdata = (void *)f;
658 /* directory inodes start off with i_nlink == 2 (for "." entry) */
659 inc_nlink(inode);
660 d_instantiate(dentry, inode);
661 inc_nlink(inode: d_inode(dentry: dentry->d_parent));
662 fsnotify_mkdir(dir: d_inode(dentry: dentry->d_parent), dentry);
663 return end_creating(dentry);
664}
665EXPORT_SYMBOL(debugfs_create_automount);
666
667/**
668 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
669 * @name: a pointer to a string containing the name of the symbolic link to
670 * create.
671 * @parent: a pointer to the parent dentry for this symbolic link. This
672 * should be a directory dentry if set. If this parameter is NULL,
673 * then the symbolic link will be created in the root of the debugfs
674 * filesystem.
675 * @target: a pointer to a string containing the path to the target of the
676 * symbolic link.
677 *
678 * This function creates a symbolic link with the given name in debugfs that
679 * links to the given target path.
680 *
681 * This function will return a pointer to a dentry if it succeeds. This
682 * pointer must be passed to the debugfs_remove() function when the symbolic
683 * link is to be removed (no automatic cleanup happens if your module is
684 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
685 * will be returned.
686 *
687 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
688 * returned.
689 */
690struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
691 const char *target)
692{
693 struct dentry *dentry;
694 struct inode *inode;
695 char *link = kstrdup(s: target, GFP_KERNEL);
696 if (!link)
697 return ERR_PTR(error: -ENOMEM);
698
699 dentry = start_creating(name, parent);
700 if (IS_ERR(ptr: dentry)) {
701 kfree(objp: link);
702 return dentry;
703 }
704
705 inode = debugfs_get_inode(sb: dentry->d_sb);
706 if (unlikely(!inode)) {
707 pr_err("out of free dentries, can not create symlink '%s'\n",
708 name);
709 kfree(objp: link);
710 return failed_creating(dentry);
711 }
712 inode->i_mode = S_IFLNK | S_IRWXUGO;
713 inode->i_op = &debugfs_symlink_inode_operations;
714 inode->i_link = link;
715 d_instantiate(dentry, inode);
716 return end_creating(dentry);
717}
718EXPORT_SYMBOL_GPL(debugfs_create_symlink);
719
720static void __debugfs_file_removed(struct dentry *dentry)
721{
722 struct debugfs_fsdata *fsd;
723
724 /*
725 * Paired with the closing smp_mb() implied by a successful
726 * cmpxchg() in debugfs_file_get(): either
727 * debugfs_file_get() must see a dead dentry or we must see a
728 * debugfs_fsdata instance at ->d_fsdata here (or both).
729 */
730 smp_mb();
731 fsd = READ_ONCE(dentry->d_fsdata);
732 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
733 return;
734 if (!refcount_dec_and_test(r: &fsd->active_users))
735 wait_for_completion(&fsd->active_users_drained);
736}
737
738static void remove_one(struct dentry *victim)
739{
740 if (d_is_reg(dentry: victim))
741 __debugfs_file_removed(dentry: victim);
742 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
743}
744
745/**
746 * debugfs_remove - recursively removes a directory
747 * @dentry: a pointer to a the dentry of the directory to be removed. If this
748 * parameter is NULL or an error value, nothing will be done.
749 *
750 * This function recursively removes a directory tree in debugfs that
751 * was previously created with a call to another debugfs function
752 * (like debugfs_create_file() or variants thereof.)
753 *
754 * This function is required to be called in order for the file to be
755 * removed, no automatic cleanup of files will happen when a module is
756 * removed, you are responsible here.
757 */
758void debugfs_remove(struct dentry *dentry)
759{
760 if (IS_ERR_OR_NULL(ptr: dentry))
761 return;
762
763 simple_pin_fs(&debug_fs_type, mount: &debugfs_mount, count: &debugfs_mount_count);
764 simple_recursive_removal(dentry, callback: remove_one);
765 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
766}
767EXPORT_SYMBOL_GPL(debugfs_remove);
768
769/**
770 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
771 * @name: a pointer to a string containing the name of the item to look up.
772 * @parent: a pointer to the parent dentry of the item.
773 *
774 * This is the equlivant of doing something like
775 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
776 * handled for the directory being looked up.
777 */
778void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
779{
780 struct dentry *dentry;
781
782 dentry = debugfs_lookup(name, parent);
783 if (!dentry)
784 return;
785
786 debugfs_remove(dentry);
787 dput(dentry);
788}
789EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
790
791/**
792 * debugfs_rename - rename a file/directory in the debugfs filesystem
793 * @old_dir: a pointer to the parent dentry for the renamed object. This
794 * should be a directory dentry.
795 * @old_dentry: dentry of an object to be renamed.
796 * @new_dir: a pointer to the parent dentry where the object should be
797 * moved. This should be a directory dentry.
798 * @new_name: a pointer to a string containing the target name.
799 *
800 * This function renames a file/directory in debugfs. The target must not
801 * exist for rename to succeed.
802 *
803 * This function will return a pointer to old_dentry (which is updated to
804 * reflect renaming) if it succeeds. If an error occurs, ERR_PTR(-ERROR)
805 * will be returned.
806 *
807 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
808 * returned.
809 */
810struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
811 struct dentry *new_dir, const char *new_name)
812{
813 int error;
814 struct dentry *dentry = NULL, *trap;
815 struct name_snapshot old_name;
816
817 if (IS_ERR(ptr: old_dir))
818 return old_dir;
819 if (IS_ERR(ptr: new_dir))
820 return new_dir;
821 if (IS_ERR_OR_NULL(ptr: old_dentry))
822 return old_dentry;
823
824 trap = lock_rename(new_dir, old_dir);
825 /* Source or destination directories don't exist? */
826 if (d_really_is_negative(dentry: old_dir) || d_really_is_negative(dentry: new_dir))
827 goto exit;
828 /* Source does not exist, cyclic rename, or mountpoint? */
829 if (d_really_is_negative(dentry: old_dentry) || old_dentry == trap ||
830 d_mountpoint(dentry: old_dentry))
831 goto exit;
832 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
833 /* Lookup failed, cyclic rename or target exists? */
834 if (IS_ERR(ptr: dentry) || dentry == trap || d_really_is_positive(dentry))
835 goto exit;
836
837 take_dentry_name_snapshot(&old_name, old_dentry);
838
839 error = simple_rename(&nop_mnt_idmap, d_inode(dentry: old_dir), old_dentry,
840 d_inode(dentry: new_dir), dentry, 0);
841 if (error) {
842 release_dentry_name_snapshot(&old_name);
843 goto exit;
844 }
845 d_move(old_dentry, dentry);
846 fsnotify_move(old_dir: d_inode(dentry: old_dir), new_dir: d_inode(dentry: new_dir), old_name: &old_name.name,
847 isdir: d_is_dir(dentry: old_dentry),
848 NULL, moved: old_dentry);
849 release_dentry_name_snapshot(&old_name);
850 unlock_rename(new_dir, old_dir);
851 dput(dentry);
852 return old_dentry;
853exit:
854 if (dentry && !IS_ERR(ptr: dentry))
855 dput(dentry);
856 unlock_rename(new_dir, old_dir);
857 if (IS_ERR(ptr: dentry))
858 return dentry;
859 return ERR_PTR(error: -EINVAL);
860}
861EXPORT_SYMBOL_GPL(debugfs_rename);
862
863/**
864 * debugfs_initialized - Tells whether debugfs has been registered
865 */
866bool debugfs_initialized(void)
867{
868 return debugfs_registered;
869}
870EXPORT_SYMBOL_GPL(debugfs_initialized);
871
872static int __init debugfs_kernel(char *str)
873{
874 if (str) {
875 if (!strcmp(str, "on"))
876 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
877 else if (!strcmp(str, "no-mount"))
878 debugfs_allow = DEBUGFS_ALLOW_API;
879 else if (!strcmp(str, "off"))
880 debugfs_allow = 0;
881 }
882
883 return 0;
884}
885early_param("debugfs", debugfs_kernel);
886static int __init debugfs_init(void)
887{
888 int retval;
889
890 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
891 return -EPERM;
892
893 retval = sysfs_create_mount_point(parent_kobj: kernel_kobj, name: "debug");
894 if (retval)
895 return retval;
896
897 retval = register_filesystem(&debug_fs_type);
898 if (retval)
899 sysfs_remove_mount_point(parent_kobj: kernel_kobj, name: "debug");
900 else
901 debugfs_registered = true;
902
903 return retval;
904}
905core_initcall(debugfs_init);
906

source code of linux/fs/debugfs/inode.c