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