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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) 2004,2019 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;
38
39/*
40 * Don't allow access attributes to be changed whilst the kernel is locked down
41 * so that we can use the file mode as part of a heuristic to determine whether
42 * to lock down individual files.
43 */
44static int debugfs_setattr(struct dentry *dentry, struct iattr *ia)
45{
46 int ret = security_locked_down(LOCKDOWN_DEBUGFS);
47
48 if (ret && (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
49 return ret;
50 return simple_setattr(dentry, ia);
51}
52
53static const struct inode_operations debugfs_file_inode_operations = {
54 .setattr = debugfs_setattr,
55};
56static const struct inode_operations debugfs_dir_inode_operations = {
57 .lookup = simple_lookup,
58 .setattr = debugfs_setattr,
59};
60static const struct inode_operations debugfs_symlink_inode_operations = {
61 .get_link = simple_get_link,
62 .setattr = debugfs_setattr,
63};
64
65static struct inode *debugfs_get_inode(struct super_block *sb)
66{
67 struct inode *inode = new_inode(sb);
68 if (inode) {
69 inode->i_ino = get_next_ino();
70 inode->i_atime = inode->i_mtime =
71 inode->i_ctime = current_time(inode);
72 }
73 return inode;
74}
75
76struct debugfs_mount_opts {
77 kuid_t uid;
78 kgid_t gid;
79 umode_t mode;
80};
81
82enum {
83 Opt_uid,
84 Opt_gid,
85 Opt_mode,
86 Opt_err
87};
88
89static const match_table_t tokens = {
90 {Opt_uid, "uid=%u"},
91 {Opt_gid, "gid=%u"},
92 {Opt_mode, "mode=%o"},
93 {Opt_err, NULL}
94};
95
96struct debugfs_fs_info {
97 struct debugfs_mount_opts mount_opts;
98};
99
100static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
101{
102 substring_t args[MAX_OPT_ARGS];
103 int option;
104 int token;
105 kuid_t uid;
106 kgid_t gid;
107 char *p;
108
109 opts->mode = DEBUGFS_DEFAULT_MODE;
110
111 while ((p = strsep(&data, ",")) != NULL) {
112 if (!*p)
113 continue;
114
115 token = match_token(p, tokens, args);
116 switch (token) {
117 case Opt_uid:
118 if (match_int(&args[0], &option))
119 return -EINVAL;
120 uid = make_kuid(current_user_ns(), option);
121 if (!uid_valid(uid))
122 return -EINVAL;
123 opts->uid = uid;
124 break;
125 case Opt_gid:
126 if (match_int(&args[0], &option))
127 return -EINVAL;
128 gid = make_kgid(current_user_ns(), option);
129 if (!gid_valid(gid))
130 return -EINVAL;
131 opts->gid = gid;
132 break;
133 case Opt_mode:
134 if (match_octal(&args[0], &option))
135 return -EINVAL;
136 opts->mode = option & S_IALLUGO;
137 break;
138 /*
139 * We might like to report bad mount options here;
140 * but traditionally debugfs has ignored all mount options
141 */
142 }
143 }
144
145 return 0;
146}
147
148static int debugfs_apply_options(struct super_block *sb)
149{
150 struct debugfs_fs_info *fsi = sb->s_fs_info;
151 struct inode *inode = d_inode(sb->s_root);
152 struct debugfs_mount_opts *opts = &fsi->mount_opts;
153
154 inode->i_mode &= ~S_IALLUGO;
155 inode->i_mode |= opts->mode;
156
157 inode->i_uid = opts->uid;
158 inode->i_gid = opts->gid;
159
160 return 0;
161}
162
163static int debugfs_remount(struct super_block *sb, int *flags, char *data)
164{
165 int err;
166 struct debugfs_fs_info *fsi = sb->s_fs_info;
167
168 sync_filesystem(sb);
169 err = debugfs_parse_options(data, &fsi->mount_opts);
170 if (err)
171 goto fail;
172
173 debugfs_apply_options(sb);
174
175fail:
176 return err;
177}
178
179static int debugfs_show_options(struct seq_file *m, struct dentry *root)
180{
181 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
182 struct debugfs_mount_opts *opts = &fsi->mount_opts;
183
184 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
185 seq_printf(m, ",uid=%u",
186 from_kuid_munged(&init_user_ns, opts->uid));
187 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
188 seq_printf(m, ",gid=%u",
189 from_kgid_munged(&init_user_ns, opts->gid));
190 if (opts->mode != DEBUGFS_DEFAULT_MODE)
191 seq_printf(m, ",mode=%o", opts->mode);
192
193 return 0;
194}
195
196static void debugfs_free_inode(struct inode *inode)
197{
198 if (S_ISLNK(inode->i_mode))
199 kfree(inode->i_link);
200 free_inode_nonrcu(inode);
201}
202
203static const struct super_operations debugfs_super_operations = {
204 .statfs = simple_statfs,
205 .remount_fs = debugfs_remount,
206 .show_options = debugfs_show_options,
207 .free_inode = debugfs_free_inode,
208};
209
210static void debugfs_release_dentry(struct dentry *dentry)
211{
212 void *fsd = dentry->d_fsdata;
213
214 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
215 kfree(dentry->d_fsdata);
216}
217
218static struct vfsmount *debugfs_automount(struct path *path)
219{
220 debugfs_automount_t f;
221 f = (debugfs_automount_t)path->dentry->d_fsdata;
222 return f(path->dentry, d_inode(path->dentry)->i_private);
223}
224
225static const struct dentry_operations debugfs_dops = {
226 .d_delete = always_delete_dentry,
227 .d_release = debugfs_release_dentry,
228 .d_automount = debugfs_automount,
229};
230
231static int debug_fill_super(struct super_block *sb, void *data, int silent)
232{
233 static const struct tree_descr debug_files[] = {{""}};
234 struct debugfs_fs_info *fsi;
235 int err;
236
237 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
238 sb->s_fs_info = fsi;
239 if (!fsi) {
240 err = -ENOMEM;
241 goto fail;
242 }
243
244 err = debugfs_parse_options(data, &fsi->mount_opts);
245 if (err)
246 goto fail;
247
248 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
249 if (err)
250 goto fail;
251
252 sb->s_op = &debugfs_super_operations;
253 sb->s_d_op = &debugfs_dops;
254
255 debugfs_apply_options(sb);
256
257 return 0;
258
259fail:
260 kfree(fsi);
261 sb->s_fs_info = NULL;
262 return err;
263}
264
265static struct dentry *debug_mount(struct file_system_type *fs_type,
266 int flags, const char *dev_name,
267 void *data)
268{
269 return mount_single(fs_type, flags, data, debug_fill_super);
270}
271
272static struct file_system_type debug_fs_type = {
273 .owner = THIS_MODULE,
274 .name = "debugfs",
275 .mount = debug_mount,
276 .kill_sb = kill_litter_super,
277};
278MODULE_ALIAS_FS("debugfs");
279
280/**
281 * debugfs_lookup() - look up an existing debugfs file
282 * @name: a pointer to a string containing the name of the file to look up.
283 * @parent: a pointer to the parent dentry of the file.
284 *
285 * This function will return a pointer to a dentry if it succeeds. If the file
286 * doesn't exist or an error occurs, %NULL will be returned. The returned
287 * dentry must be passed to dput() when it is no longer needed.
288 *
289 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
290 * returned.
291 */
292struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
293{
294 struct dentry *dentry;
295
296 if (IS_ERR(parent))
297 return NULL;
298
299 if (!parent)
300 parent = debugfs_mount->mnt_root;
301
302 dentry = lookup_one_len_unlocked(name, parent, strlen(name));
303 if (IS_ERR(dentry))
304 return NULL;
305 if (!d_really_is_positive(dentry)) {
306 dput(dentry);
307 return NULL;
308 }
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 pr_debug("creating file '%s'\n", name);
319
320 if (IS_ERR(parent))
321 return parent;
322
323 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
324 &debugfs_mount_count);
325 if (error) {
326 pr_err("Unable to pin filesystem for file '%s'\n", name);
327 return ERR_PTR(error);
328 }
329
330 /* If the parent is not specified, we create it in the root.
331 * We need the root dentry to do this, which is in the super
332 * block. A pointer to that is in the struct vfsmount that we
333 * have around.
334 */
335 if (!parent)
336 parent = debugfs_mount->mnt_root;
337
338 inode_lock(d_inode(parent));
339 dentry = lookup_one_len(name, parent, strlen(name));
340 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
341 if (d_is_dir(dentry))
342 pr_err("Directory '%s' with parent '%s' already present!\n",
343 name, parent->d_name.name);
344 else
345 pr_err("File '%s' in directory '%s' already present!\n",
346 name, parent->d_name.name);
347 dput(dentry);
348 dentry = ERR_PTR(-EEXIST);
349 }
350
351 if (IS_ERR(dentry)) {
352 inode_unlock(d_inode(parent));
353 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
354 }
355
356 return dentry;
357}
358
359static struct dentry *failed_creating(struct dentry *dentry)
360{
361 inode_unlock(d_inode(dentry->d_parent));
362 dput(dentry);
363 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
364 return ERR_PTR(-ENOMEM);
365}
366
367static struct dentry *end_creating(struct dentry *dentry)
368{
369 inode_unlock(d_inode(dentry->d_parent));
370 return dentry;
371}
372
373static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
374 struct dentry *parent, void *data,
375 const struct file_operations *proxy_fops,
376 const struct file_operations *real_fops)
377{
378 struct dentry *dentry;
379 struct inode *inode;
380
381 if (!(mode & S_IFMT))
382 mode |= S_IFREG;
383 BUG_ON(!S_ISREG(mode));
384 dentry = start_creating(name, parent);
385
386 if (IS_ERR(dentry))
387 return dentry;
388
389 inode = debugfs_get_inode(dentry->d_sb);
390 if (unlikely(!inode)) {
391 pr_err("out of free dentries, can not create file '%s'\n",
392 name);
393 return failed_creating(dentry);
394 }
395
396 inode->i_mode = mode;
397 inode->i_private = data;
398
399 inode->i_op = &debugfs_file_inode_operations;
400 inode->i_fop = proxy_fops;
401 dentry->d_fsdata = (void *)((unsigned long)real_fops |
402 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
403
404 d_instantiate(dentry, inode);
405 fsnotify_create(d_inode(dentry->d_parent), dentry);
406 return end_creating(dentry);
407}
408
409/**
410 * debugfs_create_file - create a file in the debugfs filesystem
411 * @name: a pointer to a string containing the name of the file to create.
412 * @mode: the permission that the file should have.
413 * @parent: a pointer to the parent dentry for this file. This should be a
414 * directory dentry if set. If this parameter is NULL, then the
415 * file will be created in the root of the debugfs filesystem.
416 * @data: a pointer to something that the caller will want to get to later
417 * on. The inode.i_private pointer will point to this value on
418 * the open() call.
419 * @fops: a pointer to a struct file_operations that should be used for
420 * this file.
421 *
422 * This is the basic "create a file" function for debugfs. It allows for a
423 * wide range of flexibility in creating a file, or a directory (if you want
424 * to create a directory, the debugfs_create_dir() function is
425 * recommended to be used instead.)
426 *
427 * This function will return a pointer to a dentry if it succeeds. This
428 * pointer must be passed to the debugfs_remove() function when the file is
429 * to be removed (no automatic cleanup happens if your module is unloaded,
430 * you are responsible here.) If an error occurs, %ERR_PTR(-ERROR) will be
431 * returned.
432 *
433 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
434 * returned.
435 */
436struct dentry *debugfs_create_file(const char *name, umode_t mode,
437 struct dentry *parent, void *data,
438 const struct file_operations *fops)
439{
440
441 return __debugfs_create_file(name, mode, parent, data,
442 fops ? &debugfs_full_proxy_file_operations :
443 &debugfs_noop_file_operations,
444 fops);
445}
446EXPORT_SYMBOL_GPL(debugfs_create_file);
447
448/**
449 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
450 * @name: a pointer to a string containing the name of the file to create.
451 * @mode: the permission that the file should have.
452 * @parent: a pointer to the parent dentry for this file. This should be a
453 * directory dentry if set. If this parameter is NULL, then the
454 * file will be created in the root of the debugfs filesystem.
455 * @data: a pointer to something that the caller will want to get to later
456 * on. The inode.i_private pointer will point to this value on
457 * the open() call.
458 * @fops: a pointer to a struct file_operations that should be used for
459 * this file.
460 *
461 * debugfs_create_file_unsafe() is completely analogous to
462 * debugfs_create_file(), the only difference being that the fops
463 * handed it will not get protected against file removals by the
464 * debugfs core.
465 *
466 * It is your responsibility to protect your struct file_operation
467 * methods against file removals by means of debugfs_file_get()
468 * and debugfs_file_put(). ->open() is still protected by
469 * debugfs though.
470 *
471 * Any struct file_operations defined by means of
472 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
473 * thus, may be used here.
474 */
475struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
476 struct dentry *parent, void *data,
477 const struct file_operations *fops)
478{
479
480 return __debugfs_create_file(name, mode, parent, data,
481 fops ? &debugfs_open_proxy_file_operations :
482 &debugfs_noop_file_operations,
483 fops);
484}
485EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
486
487/**
488 * debugfs_create_file_size - create a file in the debugfs filesystem
489 * @name: a pointer to a string containing the name of the file to create.
490 * @mode: the permission that the file should have.
491 * @parent: a pointer to the parent dentry for this file. This should be a
492 * directory dentry if set. If this parameter is NULL, then the
493 * file will be created in the root of the debugfs filesystem.
494 * @data: a pointer to something that the caller will want to get to later
495 * on. The inode.i_private pointer will point to this value on
496 * the open() call.
497 * @fops: a pointer to a struct file_operations that should be used for
498 * this file.
499 * @file_size: initial file size
500 *
501 * This is the basic "create a file" function for debugfs. It allows for a
502 * wide range of flexibility in creating a file, or a directory (if you want
503 * to create a directory, the debugfs_create_dir() function is
504 * recommended to be used instead.)
505 *
506 * This function will return a pointer to a dentry if it succeeds. This
507 * pointer must be passed to the debugfs_remove() function when the file is
508 * to be removed (no automatic cleanup happens if your module is unloaded,
509 * you are responsible here.) If an error occurs, %ERR_PTR(-ERROR) will be
510 * returned.
511 *
512 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
513 * returned.
514 */
515struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
516 struct dentry *parent, void *data,
517 const struct file_operations *fops,
518 loff_t file_size)
519{
520 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
521
522 if (de)
523 d_inode(de)->i_size = file_size;
524 return de;
525}
526EXPORT_SYMBOL_GPL(debugfs_create_file_size);
527
528/**
529 * debugfs_create_dir - create a directory in the debugfs filesystem
530 * @name: a pointer to a string containing the name of the directory to
531 * create.
532 * @parent: a pointer to the parent dentry for this file. This should be a
533 * directory dentry if set. If this parameter is NULL, then the
534 * directory will be created in the root of the debugfs filesystem.
535 *
536 * This function creates a directory in debugfs with the given name.
537 *
538 * This function will return a pointer to a dentry if it succeeds. This
539 * pointer must be passed to the debugfs_remove() function when the file is
540 * to be removed (no automatic cleanup happens if your module is unloaded,
541 * you are responsible here.) If an error occurs, %ERR_PTR(-ERROR) will be
542 * returned.
543 *
544 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
545 * returned.
546 */
547struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
548{
549 struct dentry *dentry = start_creating(name, parent);
550 struct inode *inode;
551
552 if (IS_ERR(dentry))
553 return dentry;
554
555 inode = debugfs_get_inode(dentry->d_sb);
556 if (unlikely(!inode)) {
557 pr_err("out of free dentries, can not create directory '%s'\n",
558 name);
559 return failed_creating(dentry);
560 }
561
562 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
563 inode->i_op = &debugfs_dir_inode_operations;
564 inode->i_fop = &simple_dir_operations;
565
566 /* directory inodes start off with i_nlink == 2 (for "." entry) */
567 inc_nlink(inode);
568 d_instantiate(dentry, inode);
569 inc_nlink(d_inode(dentry->d_parent));
570 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
571 return end_creating(dentry);
572}
573EXPORT_SYMBOL_GPL(debugfs_create_dir);
574
575/**
576 * debugfs_create_automount - create automount point in the debugfs filesystem
577 * @name: a pointer to a string containing the name of the file to create.
578 * @parent: a pointer to the parent dentry for this file. This should be a
579 * directory dentry if set. If this parameter is NULL, then the
580 * file will be created in the root of the debugfs filesystem.
581 * @f: function to be called when pathname resolution steps on that one.
582 * @data: opaque argument to pass to f().
583 *
584 * @f should return what ->d_automount() would.
585 */
586struct dentry *debugfs_create_automount(const char *name,
587 struct dentry *parent,
588 debugfs_automount_t f,
589 void *data)
590{
591 struct dentry *dentry = start_creating(name, parent);
592 struct inode *inode;
593
594 if (IS_ERR(dentry))
595 return dentry;
596
597 inode = debugfs_get_inode(dentry->d_sb);
598 if (unlikely(!inode)) {
599 pr_err("out of free dentries, can not create automount '%s'\n",
600 name);
601 return failed_creating(dentry);
602 }
603
604 make_empty_dir_inode(inode);
605 inode->i_flags |= S_AUTOMOUNT;
606 inode->i_private = data;
607 dentry->d_fsdata = (void *)f;
608 /* directory inodes start off with i_nlink == 2 (for "." entry) */
609 inc_nlink(inode);
610 d_instantiate(dentry, inode);
611 inc_nlink(d_inode(dentry->d_parent));
612 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
613 return end_creating(dentry);
614}
615EXPORT_SYMBOL(debugfs_create_automount);
616
617/**
618 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
619 * @name: a pointer to a string containing the name of the symbolic link to
620 * create.
621 * @parent: a pointer to the parent dentry for this symbolic link. This
622 * should be a directory dentry if set. If this parameter is NULL,
623 * then the symbolic link will be created in the root of the debugfs
624 * filesystem.
625 * @target: a pointer to a string containing the path to the target of the
626 * symbolic link.
627 *
628 * This function creates a symbolic link with the given name in debugfs that
629 * links to the given target path.
630 *
631 * This function will return a pointer to a dentry if it succeeds. This
632 * pointer must be passed to the debugfs_remove() function when the symbolic
633 * link is to be removed (no automatic cleanup happens if your module is
634 * unloaded, you are responsible here.) If an error occurs, %ERR_PTR(-ERROR)
635 * will be returned.
636 *
637 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
638 * returned.
639 */
640struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
641 const char *target)
642{
643 struct dentry *dentry;
644 struct inode *inode;
645 char *link = kstrdup(target, GFP_KERNEL);
646 if (!link)
647 return ERR_PTR(-ENOMEM);
648
649 dentry = start_creating(name, parent);
650 if (IS_ERR(dentry)) {
651 kfree(link);
652 return dentry;
653 }
654
655 inode = debugfs_get_inode(dentry->d_sb);
656 if (unlikely(!inode)) {
657 pr_err("out of free dentries, can not create symlink '%s'\n",
658 name);
659 kfree(link);
660 return failed_creating(dentry);
661 }
662 inode->i_mode = S_IFLNK | S_IRWXUGO;
663 inode->i_op = &debugfs_symlink_inode_operations;
664 inode->i_link = link;
665 d_instantiate(dentry, inode);
666 return end_creating(dentry);
667}
668EXPORT_SYMBOL_GPL(debugfs_create_symlink);
669
670static void __debugfs_file_removed(struct dentry *dentry)
671{
672 struct debugfs_fsdata *fsd;
673
674 /*
675 * Paired with the closing smp_mb() implied by a successful
676 * cmpxchg() in debugfs_file_get(): either
677 * debugfs_file_get() must see a dead dentry or we must see a
678 * debugfs_fsdata instance at ->d_fsdata here (or both).
679 */
680 smp_mb();
681 fsd = READ_ONCE(dentry->d_fsdata);
682 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
683 return;
684 if (!refcount_dec_and_test(&fsd->active_users))
685 wait_for_completion(&fsd->active_users_drained);
686}
687
688static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
689{
690 int ret = 0;
691
692 if (simple_positive(dentry)) {
693 dget(dentry);
694 if (d_is_dir(dentry)) {
695 ret = simple_rmdir(d_inode(parent), dentry);
696 if (!ret)
697 fsnotify_rmdir(d_inode(parent), dentry);
698 } else {
699 simple_unlink(d_inode(parent), dentry);
700 fsnotify_unlink(d_inode(parent), dentry);
701 }
702 if (!ret)
703 d_delete(dentry);
704 if (d_is_reg(dentry))
705 __debugfs_file_removed(dentry);
706 dput(dentry);
707 }
708 return ret;
709}
710
711/**
712 * debugfs_remove - removes a file or directory from the debugfs filesystem
713 * @dentry: a pointer to a the dentry of the file or directory to be
714 * removed. If this parameter is NULL or an error value, nothing
715 * will be done.
716 *
717 * This function removes a file or directory in debugfs that was previously
718 * created with a call to another debugfs function (like
719 * debugfs_create_file() or variants thereof.)
720 *
721 * This function is required to be called in order for the file to be
722 * removed, no automatic cleanup of files will happen when a module is
723 * removed, you are responsible here.
724 */
725void debugfs_remove(struct dentry *dentry)
726{
727 struct dentry *parent;
728 int ret;
729
730 if (IS_ERR_OR_NULL(dentry))
731 return;
732
733 parent = dentry->d_parent;
734 inode_lock(d_inode(parent));
735 ret = __debugfs_remove(dentry, parent);
736 inode_unlock(d_inode(parent));
737 if (!ret)
738 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
739}
740EXPORT_SYMBOL_GPL(debugfs_remove);
741
742/**
743 * debugfs_remove_recursive - recursively removes a directory
744 * @dentry: a pointer to a the dentry of the directory to be removed. If this
745 * parameter is NULL or an error value, nothing will be done.
746 *
747 * This function recursively removes a directory tree in debugfs that
748 * was previously created with a call to another debugfs function
749 * (like debugfs_create_file() or variants thereof.)
750 *
751 * This function is required to be called in order for the file to be
752 * removed, no automatic cleanup of files will happen when a module is
753 * removed, you are responsible here.
754 */
755void debugfs_remove_recursive(struct dentry *dentry)
756{
757 struct dentry *child, *parent;
758
759 if (IS_ERR_OR_NULL(dentry))
760 return;
761
762 parent = dentry;
763 down:
764 inode_lock(d_inode(parent));
765 loop:
766 /*
767 * The parent->d_subdirs is protected by the d_lock. Outside that
768 * lock, the child can be unlinked and set to be freed which can
769 * use the d_u.d_child as the rcu head and corrupt this list.
770 */
771 spin_lock(&parent->d_lock);
772 list_for_each_entry(child, &parent->d_subdirs, d_child) {
773 if (!simple_positive(child))
774 continue;
775
776 /* perhaps simple_empty(child) makes more sense */
777 if (!list_empty(&child->d_subdirs)) {
778 spin_unlock(&parent->d_lock);
779 inode_unlock(d_inode(parent));
780 parent = child;
781 goto down;
782 }
783
784 spin_unlock(&parent->d_lock);
785
786 if (!__debugfs_remove(child, parent))
787 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
788
789 /*
790 * The parent->d_lock protects agaist child from unlinking
791 * from d_subdirs. When releasing the parent->d_lock we can
792 * no longer trust that the next pointer is valid.
793 * Restart the loop. We'll skip this one with the
794 * simple_positive() check.
795 */
796 goto loop;
797 }
798 spin_unlock(&parent->d_lock);
799
800 inode_unlock(d_inode(parent));
801 child = parent;
802 parent = parent->d_parent;
803 inode_lock(d_inode(parent));
804
805 if (child != dentry)
806 /* go up */
807 goto loop;
808
809 if (!__debugfs_remove(child, parent))
810 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
811 inode_unlock(d_inode(parent));
812}
813EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
814
815/**
816 * debugfs_rename - rename a file/directory in the debugfs filesystem
817 * @old_dir: a pointer to the parent dentry for the renamed object. This
818 * should be a directory dentry.
819 * @old_dentry: dentry of an object to be renamed.
820 * @new_dir: a pointer to the parent dentry where the object should be
821 * moved. This should be a directory dentry.
822 * @new_name: a pointer to a string containing the target name.
823 *
824 * This function renames a file/directory in debugfs. The target must not
825 * exist for rename to succeed.
826 *
827 * This function will return a pointer to old_dentry (which is updated to
828 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
829 * returned.
830 *
831 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
832 * returned.
833 */
834struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
835 struct dentry *new_dir, const char *new_name)
836{
837 int error;
838 struct dentry *dentry = NULL, *trap;
839 struct name_snapshot old_name;
840
841 if (IS_ERR(old_dir))
842 return old_dir;
843 if (IS_ERR(new_dir))
844 return new_dir;
845 if (IS_ERR_OR_NULL(old_dentry))
846 return old_dentry;
847
848 trap = lock_rename(new_dir, old_dir);
849 /* Source or destination directories don't exist? */
850 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
851 goto exit;
852 /* Source does not exist, cyclic rename, or mountpoint? */
853 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
854 d_mountpoint(old_dentry))
855 goto exit;
856 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
857 /* Lookup failed, cyclic rename or target exists? */
858 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
859 goto exit;
860
861 take_dentry_name_snapshot(&old_name, old_dentry);
862
863 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
864 dentry, 0);
865 if (error) {
866 release_dentry_name_snapshot(&old_name);
867 goto exit;
868 }
869 d_move(old_dentry, dentry);
870 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
871 d_is_dir(old_dentry),
872 NULL, old_dentry);
873 release_dentry_name_snapshot(&old_name);
874 unlock_rename(new_dir, old_dir);
875 dput(dentry);
876 return old_dentry;
877exit:
878 if (dentry && !IS_ERR(dentry))
879 dput(dentry);
880 unlock_rename(new_dir, old_dir);
881 if (IS_ERR(dentry))
882 return dentry;
883 return ERR_PTR(-EINVAL);
884}
885EXPORT_SYMBOL_GPL(debugfs_rename);
886
887/**
888 * debugfs_initialized - Tells whether debugfs has been registered
889 */
890bool debugfs_initialized(void)
891{
892 return debugfs_registered;
893}
894EXPORT_SYMBOL_GPL(debugfs_initialized);
895
896static int __init debugfs_init(void)
897{
898 int retval;
899
900 retval = sysfs_create_mount_point(kernel_kobj, "debug");
901 if (retval)
902 return retval;
903
904 retval = register_filesystem(&debug_fs_type);
905 if (retval)
906 sysfs_remove_mount_point(kernel_kobj, "debug");
907 else
908 debugfs_registered = true;
909
910 return retval;
911}
912core_initcall(debugfs_init);
913