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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;
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
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);