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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/fs_context.h>
18#include <linux/fs_parser.h>
19#include <linux/pagemap.h>
20#include <linux/init.h>
21#include <linux/kobject.h>
22#include <linux/namei.h>
23#include <linux/debugfs.h>
24#include <linux/fsnotify.h>
25#include <linux/string.h>
26#include <linux/seq_file.h>
27#include <linux/magic.h>
28#include <linux/slab.h>
29#include <linux/security.h>
30
31#include "internal.h"
32
33#define DEBUGFS_DEFAULT_MODE 0700
34
35static struct vfsmount *debugfs_mount;
36static int debugfs_mount_count;
37static bool debugfs_registered;
38static unsigned int debugfs_allow __ro_after_init = DEFAULT_DEBUGFS_ALLOW_BITS;
39
40/*
41 * Don't allow access attributes to be changed whilst the kernel is locked down
42 * so that we can use the file mode as part of a heuristic to determine whether
43 * to lock down individual files.
44 */
45static int debugfs_setattr(struct mnt_idmap *idmap,
46 struct dentry *dentry, struct iattr *ia)
47{
48 int ret;
49
50 if (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) {
51 ret = security_locked_down(LOCKDOWN_DEBUGFS);
52 if (ret)
53 return ret;
54 }
55 return simple_setattr(&nop_mnt_idmap, dentry, ia);
56}
57
58static const struct inode_operations debugfs_file_inode_operations = {
59 .setattr = debugfs_setattr,
60};
61static const struct inode_operations debugfs_dir_inode_operations = {
62 .lookup = simple_lookup,
63 .setattr = debugfs_setattr,
64};
65static const struct inode_operations debugfs_symlink_inode_operations = {
66 .get_link = simple_get_link,
67 .setattr = debugfs_setattr,
68};
69
70static struct inode *debugfs_get_inode(struct super_block *sb)
71{
72 struct inode *inode = new_inode(sb);
73 if (inode) {
74 inode->i_ino = get_next_ino();
75 simple_inode_init_ts(inode);
76 }
77 return inode;
78}
79
80struct debugfs_fs_info {
81 kuid_t uid;
82 kgid_t gid;
83 umode_t mode;
84 /* Opt_* bitfield. */
85 unsigned int opts;
86};
87
88enum {
89 Opt_uid,
90 Opt_gid,
91 Opt_mode,
92 Opt_source,
93};
94
95static const struct fs_parameter_spec debugfs_param_specs[] = {
96 fsparam_gid ("gid", Opt_gid),
97 fsparam_u32oct ("mode", Opt_mode),
98 fsparam_uid ("uid", Opt_uid),
99 fsparam_string ("source", Opt_source),
100 {}
101};
102
103static int debugfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
104{
105 struct debugfs_fs_info *opts = fc->s_fs_info;
106 struct fs_parse_result result;
107 int opt;
108
109 opt = fs_parse(fc, debugfs_param_specs, param, &result);
110 if (opt < 0) {
111 /*
112 * We might like to report bad mount options here; but
113 * traditionally debugfs has ignored all mount options
114 */
115 if (opt == -ENOPARAM)
116 return 0;
117
118 return opt;
119 }
120
121 switch (opt) {
122 case Opt_uid:
123 opts->uid = result.uid;
124 break;
125 case Opt_gid:
126 opts->gid = result.gid;
127 break;
128 case Opt_mode:
129 opts->mode = result.uint_32 & S_IALLUGO;
130 break;
131 case Opt_source:
132 if (fc->source)
133 return invalfc(fc, "Multiple sources specified");
134 fc->source = param->string;
135 param->string = NULL;
136 break;
137 /*
138 * We might like to report bad mount options here;
139 * but traditionally debugfs has ignored all mount options
140 */
141 }
142
143 opts->opts |= BIT(opt);
144
145 return 0;
146}
147
148static void _debugfs_apply_options(struct super_block *sb, bool remount)
149{
150 struct debugfs_fs_info *fsi = sb->s_fs_info;
151 struct inode *inode = d_inode(sb->s_root);
152
153 /*
154 * On remount, only reset mode/uid/gid if they were provided as mount
155 * options.
156 */
157
158 if (!remount || fsi->opts & BIT(Opt_mode)) {
159 inode->i_mode &= ~S_IALLUGO;
160 inode->i_mode |= fsi->mode;
161 }
162
163 if (!remount || fsi->opts & BIT(Opt_uid))
164 inode->i_uid = fsi->uid;
165
166 if (!remount || fsi->opts & BIT(Opt_gid))
167 inode->i_gid = fsi->gid;
168}
169
170static void debugfs_apply_options(struct super_block *sb)
171{
172 _debugfs_apply_options(sb, false);
173}
174
175static void debugfs_apply_options_remount(struct super_block *sb)
176{
177 _debugfs_apply_options(sb, true);
178}
179
180static int debugfs_reconfigure(struct fs_context *fc)
181{
182 struct super_block *sb = fc->root->d_sb;
183 struct debugfs_fs_info *sb_opts = sb->s_fs_info;
184 struct debugfs_fs_info *new_opts = fc->s_fs_info;
185
186 sync_filesystem(sb);
187
188 /* structure copy of new mount options to sb */
189 *sb_opts = *new_opts;
190 debugfs_apply_options_remount(sb);
191
192 return 0;
193}
194
195static int debugfs_show_options(struct seq_file *m, struct dentry *root)
196{
197 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
198
199 if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID))
200 seq_printf(m, ",uid=%u",
201 from_kuid_munged(&init_user_ns, fsi->uid));
202 if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))
203 seq_printf(m, ",gid=%u",
204 from_kgid_munged(&init_user_ns, fsi->gid));
205 if (fsi->mode != DEBUGFS_DEFAULT_MODE)
206 seq_printf(m, ",mode=%o", fsi->mode);
207
208 return 0;
209}
210
211static void debugfs_free_inode(struct inode *inode)
212{
213 if (S_ISLNK(inode->i_mode))
214 kfree(inode->i_link);
215 free_inode_nonrcu(inode);
216}
217
218static const struct super_operations debugfs_super_operations = {
219 .statfs = simple_statfs,
220 .show_options = debugfs_show_options,
221 .free_inode = debugfs_free_inode,
222};
223
224static void debugfs_release_dentry(struct dentry *dentry)
225{
226 struct debugfs_fsdata *fsd = dentry->d_fsdata;
227
228 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
229 return;
230
231 /* check it wasn't a dir (no fsdata) or automount (no real_fops) */
232 if (fsd && (fsd->real_fops || fsd->short_fops)) {
233 WARN_ON(!list_empty(&fsd->cancellations));
234 mutex_destroy(&fsd->cancellations_mtx);
235 }
236
237 kfree(fsd);
238}
239
240static struct vfsmount *debugfs_automount(struct path *path)
241{
242 struct debugfs_fsdata *fsd = path->dentry->d_fsdata;
243
244 return fsd->automount(path->dentry, d_inode(path->dentry)->i_private);
245}
246
247static const struct dentry_operations debugfs_dops = {
248 .d_delete = always_delete_dentry,
249 .d_release = debugfs_release_dentry,
250 .d_automount = debugfs_automount,
251};
252
253static int debugfs_fill_super(struct super_block *sb, struct fs_context *fc)
254{
255 static const struct tree_descr debug_files[] = {{""}};
256 int err;
257
258 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
259 if (err)
260 return err;
261
262 sb->s_op = &debugfs_super_operations;
263 sb->s_d_op = &debugfs_dops;
264
265 debugfs_apply_options(sb);
266
267 return 0;
268}
269
270static int debugfs_get_tree(struct fs_context *fc)
271{
272 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
273 return -EPERM;
274
275 return get_tree_single(fc, debugfs_fill_super);
276}
277
278static void debugfs_free_fc(struct fs_context *fc)
279{
280 kfree(fc->s_fs_info);
281}
282
283static const struct fs_context_operations debugfs_context_ops = {
284 .free = debugfs_free_fc,
285 .parse_param = debugfs_parse_param,
286 .get_tree = debugfs_get_tree,
287 .reconfigure = debugfs_reconfigure,
288};
289
290static int debugfs_init_fs_context(struct fs_context *fc)
291{
292 struct debugfs_fs_info *fsi;
293
294 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
295 if (!fsi)
296 return -ENOMEM;
297
298 fsi->mode = DEBUGFS_DEFAULT_MODE;
299
300 fc->s_fs_info = fsi;
301 fc->ops = &debugfs_context_ops;
302 return 0;
303}
304
305static struct file_system_type debug_fs_type = {
306 .owner = THIS_MODULE,
307 .name = "debugfs",
308 .init_fs_context = debugfs_init_fs_context,
309 .parameters = debugfs_param_specs,
310 .kill_sb = kill_litter_super,
311};
312MODULE_ALIAS_FS("debugfs");
313
314/**
315 * debugfs_lookup() - look up an existing debugfs file
316 * @name: a pointer to a string containing the name of the file to look up.
317 * @parent: a pointer to the parent dentry of the file.
318 *
319 * This function will return a pointer to a dentry if it succeeds. If the file
320 * doesn't exist or an error occurs, %NULL will be returned. The returned
321 * dentry must be passed to dput() when it is no longer needed.
322 *
323 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
324 * returned.
325 */
326struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
327{
328 struct dentry *dentry;
329
330 if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
331 return NULL;
332
333 if (!parent)
334 parent = debugfs_mount->mnt_root;
335
336 dentry = lookup_positive_unlocked(name, parent, strlen(name));
337 if (IS_ERR(dentry))
338 return NULL;
339 return dentry;
340}
341EXPORT_SYMBOL_GPL(debugfs_lookup);
342
343static struct dentry *start_creating(const char *name, struct dentry *parent)
344{
345 struct dentry *dentry;
346 int error;
347
348 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
349 return ERR_PTR(-EPERM);
350
351 if (!debugfs_initialized())
352 return ERR_PTR(-ENOENT);
353
354 pr_debug("creating file '%s'\n", name);
355
356 if (IS_ERR(parent))
357 return parent;
358
359 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
360 &debugfs_mount_count);
361 if (error) {
362 pr_err("Unable to pin filesystem for file '%s'\n", name);
363 return ERR_PTR(error);
364 }
365
366 /* If the parent is not specified, we create it in the root.
367 * We need the root dentry to do this, which is in the super
368 * block. A pointer to that is in the struct vfsmount that we
369 * have around.
370 */
371 if (!parent)
372 parent = debugfs_mount->mnt_root;
373
374 inode_lock(d_inode(parent));
375 if (unlikely(IS_DEADDIR(d_inode(parent))))
376 dentry = ERR_PTR(-ENOENT);
377 else
378 dentry = lookup_one_len(name, parent, strlen(name));
379 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
380 if (d_is_dir(dentry))
381 pr_err("Directory '%s' with parent '%s' already present!\n",
382 name, parent->d_name.name);
383 else
384 pr_err("File '%s' in directory '%s' already present!\n",
385 name, parent->d_name.name);
386 dput(dentry);
387 dentry = ERR_PTR(-EEXIST);
388 }
389
390 if (IS_ERR(dentry)) {
391 inode_unlock(d_inode(parent));
392 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
393 }
394
395 return dentry;
396}
397
398static struct dentry *failed_creating(struct dentry *dentry)
399{
400 inode_unlock(d_inode(dentry->d_parent));
401 dput(dentry);
402 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
403 return ERR_PTR(-ENOMEM);
404}
405
406static struct dentry *end_creating(struct dentry *dentry)
407{
408 inode_unlock(d_inode(dentry->d_parent));
409 return dentry;
410}
411
412static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
413 struct dentry *parent, void *data,
414 const struct file_operations *proxy_fops,
415 const void *real_fops)
416{
417 struct dentry *dentry;
418 struct inode *inode;
419
420 if (!(mode & S_IFMT))
421 mode |= S_IFREG;
422 BUG_ON(!S_ISREG(mode));
423 dentry = start_creating(name, parent);
424
425 if (IS_ERR(dentry))
426 return dentry;
427
428 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
429 failed_creating(dentry);
430 return ERR_PTR(-EPERM);
431 }
432
433 inode = debugfs_get_inode(dentry->d_sb);
434 if (unlikely(!inode)) {
435 pr_err("out of free dentries, can not create file '%s'\n",
436 name);
437 return failed_creating(dentry);
438 }
439
440 inode->i_mode = mode;
441 inode->i_private = data;
442
443 inode->i_op = &debugfs_file_inode_operations;
444 inode->i_fop = proxy_fops;
445 dentry->d_fsdata = (void *)((unsigned long)real_fops |
446 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
447
448 d_instantiate(dentry, inode);
449 fsnotify_create(d_inode(dentry->d_parent), dentry);
450 return end_creating(dentry);
451}
452
453struct dentry *debugfs_create_file_full(const char *name, umode_t mode,
454 struct dentry *parent, void *data,
455 const struct file_operations *fops)
456{
457 if (WARN_ON((unsigned long)fops &
458 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
459 return ERR_PTR(-EINVAL);
460
461 return __debugfs_create_file(name, mode, parent, data,
462 fops ? &debugfs_full_proxy_file_operations :
463 &debugfs_noop_file_operations,
464 fops);
465}
466EXPORT_SYMBOL_GPL(debugfs_create_file_full);
467
468struct dentry *debugfs_create_file_short(const char *name, umode_t mode,
469 struct dentry *parent, void *data,
470 const struct debugfs_short_fops *fops)
471{
472 if (WARN_ON((unsigned long)fops &
473 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
474 return ERR_PTR(-EINVAL);
475
476 return __debugfs_create_file(name, mode, parent, data,
477 fops ? &debugfs_full_short_proxy_file_operations :
478 &debugfs_noop_file_operations,
479 fops);
480}
481EXPORT_SYMBOL_GPL(debugfs_create_file_short);
482
483/**
484 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
485 * @name: a pointer to a string containing the name of the file to create.
486 * @mode: the permission that the file should have.
487 * @parent: a pointer to the parent dentry for this file. This should be a
488 * directory dentry if set. If this parameter is NULL, then the
489 * file will be created in the root of the debugfs filesystem.
490 * @data: a pointer to something that the caller will want to get to later
491 * on. The inode.i_private pointer will point to this value on
492 * the open() call.
493 * @fops: a pointer to a struct file_operations that should be used for
494 * this file.
495 *
496 * debugfs_create_file_unsafe() is completely analogous to
497 * debugfs_create_file(), the only difference being that the fops
498 * handed it will not get protected against file removals by the
499 * debugfs core.
500 *
501 * It is your responsibility to protect your struct file_operation
502 * methods against file removals by means of debugfs_file_get()
503 * and debugfs_file_put(). ->open() is still protected by
504 * debugfs though.
505 *
506 * Any struct file_operations defined by means of
507 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
508 * thus, may be used here.
509 */
510struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
511 struct dentry *parent, void *data,
512 const struct file_operations *fops)
513{
514
515 return __debugfs_create_file(name, mode, parent, data,
516 fops ? &debugfs_open_proxy_file_operations :
517 &debugfs_noop_file_operations,
518 fops);
519}
520EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
521
522/**
523 * debugfs_create_file_size - create a file in the debugfs filesystem
524 * @name: a pointer to a string containing the name of the file to create.
525 * @mode: the permission that the file should have.
526 * @parent: a pointer to the parent dentry for this file. This should be a
527 * directory dentry if set. If this parameter is NULL, then the
528 * file will be created in the root of the debugfs filesystem.
529 * @data: a pointer to something that the caller will want to get to later
530 * on. The inode.i_private pointer will point to this value on
531 * the open() call.
532 * @fops: a pointer to a struct file_operations that should be used for
533 * this file.
534 * @file_size: initial file size
535 *
536 * This is the basic "create a file" function for debugfs. It allows for a
537 * wide range of flexibility in creating a file, or a directory (if you want
538 * to create a directory, the debugfs_create_dir() function is
539 * recommended to be used instead.)
540 */
541void debugfs_create_file_size(const char *name, umode_t mode,
542 struct dentry *parent, void *data,
543 const struct file_operations *fops,
544 loff_t file_size)
545{
546 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
547
548 if (!IS_ERR(de))
549 d_inode(de)->i_size = file_size;
550}
551EXPORT_SYMBOL_GPL(debugfs_create_file_size);
552
553/**
554 * debugfs_create_dir - create a directory in the debugfs filesystem
555 * @name: a pointer to a string containing the name of the directory to
556 * create.
557 * @parent: a pointer to the parent dentry for this file. This should be a
558 * directory dentry if set. If this parameter is NULL, then the
559 * directory will be created in the root of the debugfs filesystem.
560 *
561 * This function creates a directory in debugfs with the given name.
562 *
563 * This function will return a pointer to a dentry if it succeeds. This
564 * pointer must be passed to the debugfs_remove() function when the file is
565 * to be removed (no automatic cleanup happens if your module is unloaded,
566 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
567 * returned.
568 *
569 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
570 * returned.
571 *
572 * NOTE: it's expected that most callers should _ignore_ the errors returned
573 * by this function. Other debugfs functions handle the fact that the "dentry"
574 * passed to them could be an error and they don't crash in that case.
575 * Drivers should generally work fine even if debugfs fails to init anyway.
576 */
577struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
578{
579 struct dentry *dentry = start_creating(name, parent);
580 struct inode *inode;
581
582 if (IS_ERR(dentry))
583 return dentry;
584
585 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
586 failed_creating(dentry);
587 return ERR_PTR(-EPERM);
588 }
589
590 inode = debugfs_get_inode(dentry->d_sb);
591 if (unlikely(!inode)) {
592 pr_err("out of free dentries, can not create directory '%s'\n",
593 name);
594 return failed_creating(dentry);
595 }
596
597 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
598 inode->i_op = &debugfs_dir_inode_operations;
599 inode->i_fop = &simple_dir_operations;
600
601 /* directory inodes start off with i_nlink == 2 (for "." entry) */
602 inc_nlink(inode);
603 d_instantiate(dentry, inode);
604 inc_nlink(d_inode(dentry->d_parent));
605 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
606 return end_creating(dentry);
607}
608EXPORT_SYMBOL_GPL(debugfs_create_dir);
609
610/**
611 * debugfs_create_automount - create automount point in the debugfs filesystem
612 * @name: a pointer to a string containing the name of the file to create.
613 * @parent: a pointer to the parent dentry for this file. This should be a
614 * directory dentry if set. If this parameter is NULL, then the
615 * file will be created in the root of the debugfs filesystem.
616 * @f: function to be called when pathname resolution steps on that one.
617 * @data: opaque argument to pass to f().
618 *
619 * @f should return what ->d_automount() would.
620 */
621struct dentry *debugfs_create_automount(const char *name,
622 struct dentry *parent,
623 debugfs_automount_t f,
624 void *data)
625{
626 struct dentry *dentry = start_creating(name, parent);
627 struct debugfs_fsdata *fsd;
628 struct inode *inode;
629
630 if (IS_ERR(dentry))
631 return dentry;
632
633 fsd = kzalloc(sizeof(*fsd), GFP_KERNEL);
634 if (!fsd) {
635 failed_creating(dentry);
636 return ERR_PTR(-ENOMEM);
637 }
638
639 fsd->automount = f;
640
641 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
642 failed_creating(dentry);
643 kfree(fsd);
644 return ERR_PTR(-EPERM);
645 }
646
647 inode = debugfs_get_inode(dentry->d_sb);
648 if (unlikely(!inode)) {
649 pr_err("out of free dentries, can not create automount '%s'\n",
650 name);
651 kfree(fsd);
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 = fsd;
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
736 /* if this was the last reference, we're done */
737 if (refcount_dec_and_test(&fsd->active_users))
738 return;
739
740 /*
741 * If there's still a reference, the code that obtained it can
742 * be in different states:
743 * - The common case of not using cancellations, or already
744 * after debugfs_leave_cancellation(), where we just need
745 * to wait for debugfs_file_put() which signals the completion;
746 * - inside a cancellation section, i.e. between
747 * debugfs_enter_cancellation() and debugfs_leave_cancellation(),
748 * in which case we need to trigger the ->cancel() function,
749 * and then wait for debugfs_file_put() just like in the
750 * previous case;
751 * - before debugfs_enter_cancellation() (but obviously after
752 * debugfs_file_get()), in which case we may not see the
753 * cancellation in the list on the first round of the loop,
754 * but debugfs_enter_cancellation() signals the completion
755 * after adding it, so this code gets woken up to call the
756 * ->cancel() function.
757 */
758 while (refcount_read(&fsd->active_users)) {
759 struct debugfs_cancellation *c;
760
761 /*
762 * Lock the cancellations. Note that the cancellations
763 * structs are meant to be on the stack, so we need to
764 * ensure we either use them here or don't touch them,
765 * and debugfs_leave_cancellation() will wait for this
766 * to be finished processing before exiting one. It may
767 * of course win and remove the cancellation, but then
768 * chances are we never even got into this bit, we only
769 * do if the refcount isn't zero already.
770 */
771 mutex_lock(&fsd->cancellations_mtx);
772 while ((c = list_first_entry_or_null(&fsd->cancellations,
773 typeof(*c), list))) {
774 list_del_init(&c->list);
775 c->cancel(dentry, c->cancel_data);
776 }
777 mutex_unlock(&fsd->cancellations_mtx);
778
779 wait_for_completion(&fsd->active_users_drained);
780 }
781}
782
783static void remove_one(struct dentry *victim)
784{
785 if (d_is_reg(victim))
786 __debugfs_file_removed(victim);
787 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
788}
789
790/**
791 * debugfs_remove - recursively removes a directory
792 * @dentry: a pointer to a the dentry of the directory to be removed. If this
793 * parameter is NULL or an error value, nothing will be done.
794 *
795 * This function recursively removes a directory tree in debugfs that
796 * was previously created with a call to another debugfs function
797 * (like debugfs_create_file() or variants thereof.)
798 *
799 * This function is required to be called in order for the file to be
800 * removed, no automatic cleanup of files will happen when a module is
801 * removed, you are responsible here.
802 */
803void debugfs_remove(struct dentry *dentry)
804{
805 if (IS_ERR_OR_NULL(dentry))
806 return;
807
808 simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
809 simple_recursive_removal(dentry, remove_one);
810 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
811}
812EXPORT_SYMBOL_GPL(debugfs_remove);
813
814/**
815 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
816 * @name: a pointer to a string containing the name of the item to look up.
817 * @parent: a pointer to the parent dentry of the item.
818 *
819 * This is the equlivant of doing something like
820 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
821 * handled for the directory being looked up.
822 */
823void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
824{
825 struct dentry *dentry;
826
827 dentry = debugfs_lookup(name, parent);
828 if (!dentry)
829 return;
830
831 debugfs_remove(dentry);
832 dput(dentry);
833}
834EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
835
836/**
837 * debugfs_rename - rename a file/directory in the debugfs filesystem
838 * @old_dir: a pointer to the parent dentry for the renamed object. This
839 * should be a directory dentry.
840 * @old_dentry: dentry of an object to be renamed.
841 * @new_dir: a pointer to the parent dentry where the object should be
842 * moved. This should be a directory dentry.
843 * @new_name: a pointer to a string containing the target name.
844 *
845 * This function renames a file/directory in debugfs. The target must not
846 * exist for rename to succeed.
847 *
848 * This function will return a pointer to old_dentry (which is updated to
849 * reflect renaming) if it succeeds. If an error occurs, ERR_PTR(-ERROR)
850 * will be returned.
851 *
852 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
853 * returned.
854 */
855struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
856 struct dentry *new_dir, const char *new_name)
857{
858 int error;
859 struct dentry *dentry = NULL, *trap;
860 struct name_snapshot old_name;
861
862 if (IS_ERR(old_dir))
863 return old_dir;
864 if (IS_ERR(new_dir))
865 return new_dir;
866 if (IS_ERR_OR_NULL(old_dentry))
867 return old_dentry;
868
869 trap = lock_rename(new_dir, old_dir);
870 /* Source or destination directories don't exist? */
871 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
872 goto exit;
873 /* Source does not exist, cyclic rename, or mountpoint? */
874 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
875 d_mountpoint(old_dentry))
876 goto exit;
877 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
878 /* Lookup failed, cyclic rename or target exists? */
879 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
880 goto exit;
881
882 take_dentry_name_snapshot(&old_name, old_dentry);
883
884 error = simple_rename(&nop_mnt_idmap, d_inode(old_dir), old_dentry,
885 d_inode(new_dir), dentry, 0);
886 if (error) {
887 release_dentry_name_snapshot(&old_name);
888 goto exit;
889 }
890 d_move(old_dentry, dentry);
891 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
892 d_is_dir(old_dentry),
893 NULL, old_dentry);
894 release_dentry_name_snapshot(&old_name);
895 unlock_rename(new_dir, old_dir);
896 dput(dentry);
897 return old_dentry;
898exit:
899 if (dentry && !IS_ERR(dentry))
900 dput(dentry);
901 unlock_rename(new_dir, old_dir);
902 if (IS_ERR(dentry))
903 return dentry;
904 return ERR_PTR(-EINVAL);
905}
906EXPORT_SYMBOL_GPL(debugfs_rename);
907
908/**
909 * debugfs_initialized - Tells whether debugfs has been registered
910 */
911bool debugfs_initialized(void)
912{
913 return debugfs_registered;
914}
915EXPORT_SYMBOL_GPL(debugfs_initialized);
916
917static int __init debugfs_kernel(char *str)
918{
919 if (str) {
920 if (!strcmp(str, "on"))
921 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
922 else if (!strcmp(str, "no-mount"))
923 debugfs_allow = DEBUGFS_ALLOW_API;
924 else if (!strcmp(str, "off"))
925 debugfs_allow = 0;
926 }
927
928 return 0;
929}
930early_param("debugfs", debugfs_kernel);
931static int __init debugfs_init(void)
932{
933 int retval;
934
935 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
936 return -EPERM;
937
938 retval = sysfs_create_mount_point(kernel_kobj, "debug");
939 if (retval)
940 return retval;
941
942 retval = register_filesystem(&debug_fs_type);
943 if (retval)
944 sysfs_remove_mount_point(kernel_kobj, "debug");
945 else
946 debugfs_registered = true;
947
948 return retval;
949}
950core_initcall(debugfs_init);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * inode.c - part of debugfs, a tiny little debug file system
4 *
5 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
6 * Copyright (C) 2004 IBM Inc.
7 *
8 * debugfs is for people to use instead of /proc or /sys.
9 * See ./Documentation/core-api/kernel-api.rst for more details.
10 */
11
12#include <linux/module.h>
13#include <linux/fs.h>
14#include <linux/mount.h>
15#include <linux/pagemap.h>
16#include <linux/init.h>
17#include <linux/kobject.h>
18#include <linux/namei.h>
19#include <linux/debugfs.h>
20#include <linux/fsnotify.h>
21#include <linux/string.h>
22#include <linux/seq_file.h>
23#include <linux/parser.h>
24#include <linux/magic.h>
25#include <linux/slab.h>
26
27#include "internal.h"
28
29#define DEBUGFS_DEFAULT_MODE 0700
30
31static struct vfsmount *debugfs_mount;
32static int debugfs_mount_count;
33static bool debugfs_registered;
34
35static struct inode *debugfs_get_inode(struct super_block *sb)
36{
37 struct inode *inode = new_inode(sb);
38 if (inode) {
39 inode->i_ino = get_next_ino();
40 inode->i_atime = inode->i_mtime =
41 inode->i_ctime = current_time(inode);
42 }
43 return inode;
44}
45
46struct debugfs_mount_opts {
47 kuid_t uid;
48 kgid_t gid;
49 umode_t mode;
50};
51
52enum {
53 Opt_uid,
54 Opt_gid,
55 Opt_mode,
56 Opt_err
57};
58
59static const match_table_t tokens = {
60 {Opt_uid, "uid=%u"},
61 {Opt_gid, "gid=%u"},
62 {Opt_mode, "mode=%o"},
63 {Opt_err, NULL}
64};
65
66struct debugfs_fs_info {
67 struct debugfs_mount_opts mount_opts;
68};
69
70static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
71{
72 substring_t args[MAX_OPT_ARGS];
73 int option;
74 int token;
75 kuid_t uid;
76 kgid_t gid;
77 char *p;
78
79 opts->mode = DEBUGFS_DEFAULT_MODE;
80
81 while ((p = strsep(&data, ",")) != NULL) {
82 if (!*p)
83 continue;
84
85 token = match_token(p, tokens, args);
86 switch (token) {
87 case Opt_uid:
88 if (match_int(&args[0], &option))
89 return -EINVAL;
90 uid = make_kuid(current_user_ns(), option);
91 if (!uid_valid(uid))
92 return -EINVAL;
93 opts->uid = uid;
94 break;
95 case Opt_gid:
96 if (match_int(&args[0], &option))
97 return -EINVAL;
98 gid = make_kgid(current_user_ns(), option);
99 if (!gid_valid(gid))
100 return -EINVAL;
101 opts->gid = gid;
102 break;
103 case Opt_mode:
104 if (match_octal(&args[0], &option))
105 return -EINVAL;
106 opts->mode = option & S_IALLUGO;
107 break;
108 /*
109 * We might like to report bad mount options here;
110 * but traditionally debugfs has ignored all mount options
111 */
112 }
113 }
114
115 return 0;
116}
117
118static int debugfs_apply_options(struct super_block *sb)
119{
120 struct debugfs_fs_info *fsi = sb->s_fs_info;
121 struct inode *inode = d_inode(sb->s_root);
122 struct debugfs_mount_opts *opts = &fsi->mount_opts;
123
124 inode->i_mode &= ~S_IALLUGO;
125 inode->i_mode |= opts->mode;
126
127 inode->i_uid = opts->uid;
128 inode->i_gid = opts->gid;
129
130 return 0;
131}
132
133static int debugfs_remount(struct super_block *sb, int *flags, char *data)
134{
135 int err;
136 struct debugfs_fs_info *fsi = sb->s_fs_info;
137
138 sync_filesystem(sb);
139 err = debugfs_parse_options(data, &fsi->mount_opts);
140 if (err)
141 goto fail;
142
143 debugfs_apply_options(sb);
144
145fail:
146 return err;
147}
148
149static int debugfs_show_options(struct seq_file *m, struct dentry *root)
150{
151 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
152 struct debugfs_mount_opts *opts = &fsi->mount_opts;
153
154 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
155 seq_printf(m, ",uid=%u",
156 from_kuid_munged(&init_user_ns, opts->uid));
157 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
158 seq_printf(m, ",gid=%u",
159 from_kgid_munged(&init_user_ns, opts->gid));
160 if (opts->mode != DEBUGFS_DEFAULT_MODE)
161 seq_printf(m, ",mode=%o", opts->mode);
162
163 return 0;
164}
165
166static void debugfs_evict_inode(struct inode *inode)
167{
168 truncate_inode_pages_final(&inode->i_data);
169 clear_inode(inode);
170 if (S_ISLNK(inode->i_mode))
171 kfree(inode->i_link);
172}
173
174static const struct super_operations debugfs_super_operations = {
175 .statfs = simple_statfs,
176 .remount_fs = debugfs_remount,
177 .show_options = debugfs_show_options,
178 .evict_inode = debugfs_evict_inode,
179};
180
181static void debugfs_release_dentry(struct dentry *dentry)
182{
183 void *fsd = dentry->d_fsdata;
184
185 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
186 kfree(dentry->d_fsdata);
187}
188
189static struct vfsmount *debugfs_automount(struct path *path)
190{
191 debugfs_automount_t f;
192 f = (debugfs_automount_t)path->dentry->d_fsdata;
193 return f(path->dentry, d_inode(path->dentry)->i_private);
194}
195
196static const struct dentry_operations debugfs_dops = {
197 .d_delete = always_delete_dentry,
198 .d_release = debugfs_release_dentry,
199 .d_automount = debugfs_automount,
200};
201
202static int debug_fill_super(struct super_block *sb, void *data, int silent)
203{
204 static const struct tree_descr debug_files[] = {{""}};
205 struct debugfs_fs_info *fsi;
206 int err;
207
208 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
209 sb->s_fs_info = fsi;
210 if (!fsi) {
211 err = -ENOMEM;
212 goto fail;
213 }
214
215 err = debugfs_parse_options(data, &fsi->mount_opts);
216 if (err)
217 goto fail;
218
219 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
220 if (err)
221 goto fail;
222
223 sb->s_op = &debugfs_super_operations;
224 sb->s_d_op = &debugfs_dops;
225
226 debugfs_apply_options(sb);
227
228 return 0;
229
230fail:
231 kfree(fsi);
232 sb->s_fs_info = NULL;
233 return err;
234}
235
236static struct dentry *debug_mount(struct file_system_type *fs_type,
237 int flags, const char *dev_name,
238 void *data)
239{
240 return mount_single(fs_type, flags, data, debug_fill_super);
241}
242
243static struct file_system_type debug_fs_type = {
244 .owner = THIS_MODULE,
245 .name = "debugfs",
246 .mount = debug_mount,
247 .kill_sb = kill_litter_super,
248};
249MODULE_ALIAS_FS("debugfs");
250
251/**
252 * debugfs_lookup() - look up an existing debugfs file
253 * @name: a pointer to a string containing the name of the file to look up.
254 * @parent: a pointer to the parent dentry of the file.
255 *
256 * This function will return a pointer to a dentry if it succeeds. If the file
257 * doesn't exist or an error occurs, %NULL will be returned. The returned
258 * dentry must be passed to dput() when it is no longer needed.
259 *
260 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
261 * returned.
262 */
263struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
264{
265 struct dentry *dentry;
266
267 if (IS_ERR(parent))
268 return NULL;
269
270 if (!parent)
271 parent = debugfs_mount->mnt_root;
272
273 dentry = lookup_one_len_unlocked(name, parent, strlen(name));
274 if (IS_ERR(dentry))
275 return NULL;
276 if (!d_really_is_positive(dentry)) {
277 dput(dentry);
278 return NULL;
279 }
280 return dentry;
281}
282EXPORT_SYMBOL_GPL(debugfs_lookup);
283
284static struct dentry *start_creating(const char *name, struct dentry *parent)
285{
286 struct dentry *dentry;
287 int error;
288
289 pr_debug("debugfs: creating file '%s'\n",name);
290
291 if (IS_ERR(parent))
292 return parent;
293
294 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
295 &debugfs_mount_count);
296 if (error)
297 return ERR_PTR(error);
298
299 /* If the parent is not specified, we create it in the root.
300 * We need the root dentry to do this, which is in the super
301 * block. A pointer to that is in the struct vfsmount that we
302 * have around.
303 */
304 if (!parent)
305 parent = debugfs_mount->mnt_root;
306
307 inode_lock(d_inode(parent));
308 dentry = lookup_one_len(name, parent, strlen(name));
309 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
310 dput(dentry);
311 dentry = ERR_PTR(-EEXIST);
312 }
313
314 if (IS_ERR(dentry)) {
315 inode_unlock(d_inode(parent));
316 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
317 }
318
319 return dentry;
320}
321
322static struct dentry *failed_creating(struct dentry *dentry)
323{
324 inode_unlock(d_inode(dentry->d_parent));
325 dput(dentry);
326 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
327 return NULL;
328}
329
330static struct dentry *end_creating(struct dentry *dentry)
331{
332 inode_unlock(d_inode(dentry->d_parent));
333 return dentry;
334}
335
336static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
337 struct dentry *parent, void *data,
338 const struct file_operations *proxy_fops,
339 const struct file_operations *real_fops)
340{
341 struct dentry *dentry;
342 struct inode *inode;
343
344 if (!(mode & S_IFMT))
345 mode |= S_IFREG;
346 BUG_ON(!S_ISREG(mode));
347 dentry = start_creating(name, parent);
348
349 if (IS_ERR(dentry))
350 return NULL;
351
352 inode = debugfs_get_inode(dentry->d_sb);
353 if (unlikely(!inode))
354 return failed_creating(dentry);
355
356 inode->i_mode = mode;
357 inode->i_private = data;
358
359 inode->i_fop = proxy_fops;
360 dentry->d_fsdata = (void *)((unsigned long)real_fops |
361 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
362
363 d_instantiate(dentry, inode);
364 fsnotify_create(d_inode(dentry->d_parent), dentry);
365 return end_creating(dentry);
366}
367
368/**
369 * debugfs_create_file - create a file in the debugfs filesystem
370 * @name: a pointer to a string containing the name of the file to create.
371 * @mode: the permission that the file should have.
372 * @parent: a pointer to the parent dentry for this file. This should be a
373 * directory dentry if set. If this parameter is NULL, then the
374 * file will be created in the root of the debugfs filesystem.
375 * @data: a pointer to something that the caller will want to get to later
376 * on. The inode.i_private pointer will point to this value on
377 * the open() call.
378 * @fops: a pointer to a struct file_operations that should be used for
379 * this file.
380 *
381 * This is the basic "create a file" function for debugfs. It allows for a
382 * wide range of flexibility in creating a file, or a directory (if you want
383 * to create a directory, the debugfs_create_dir() function is
384 * recommended to be used instead.)
385 *
386 * This function will return a pointer to a dentry if it succeeds. This
387 * pointer must be passed to the debugfs_remove() function when the file is
388 * to be removed (no automatic cleanup happens if your module is unloaded,
389 * you are responsible here.) If an error occurs, %NULL will be returned.
390 *
391 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
392 * returned.
393 */
394struct dentry *debugfs_create_file(const char *name, umode_t mode,
395 struct dentry *parent, void *data,
396 const struct file_operations *fops)
397{
398
399 return __debugfs_create_file(name, mode, parent, data,
400 fops ? &debugfs_full_proxy_file_operations :
401 &debugfs_noop_file_operations,
402 fops);
403}
404EXPORT_SYMBOL_GPL(debugfs_create_file);
405
406/**
407 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
408 * @name: a pointer to a string containing the name of the file to create.
409 * @mode: the permission that the file should have.
410 * @parent: a pointer to the parent dentry for this file. This should be a
411 * directory dentry if set. If this parameter is NULL, then the
412 * file will be created in the root of the debugfs filesystem.
413 * @data: a pointer to something that the caller will want to get to later
414 * on. The inode.i_private pointer will point to this value on
415 * the open() call.
416 * @fops: a pointer to a struct file_operations that should be used for
417 * this file.
418 *
419 * debugfs_create_file_unsafe() is completely analogous to
420 * debugfs_create_file(), the only difference being that the fops
421 * handed it will not get protected against file removals by the
422 * debugfs core.
423 *
424 * It is your responsibility to protect your struct file_operation
425 * methods against file removals by means of debugfs_use_file_start()
426 * and debugfs_use_file_finish(). ->open() is still protected by
427 * debugfs though.
428 *
429 * Any struct file_operations defined by means of
430 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
431 * thus, may be used here.
432 */
433struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
434 struct dentry *parent, void *data,
435 const struct file_operations *fops)
436{
437
438 return __debugfs_create_file(name, mode, parent, data,
439 fops ? &debugfs_open_proxy_file_operations :
440 &debugfs_noop_file_operations,
441 fops);
442}
443EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
444
445/**
446 * debugfs_create_file_size - create a file in the debugfs filesystem
447 * @name: a pointer to a string containing the name of the file to create.
448 * @mode: the permission that the file should have.
449 * @parent: a pointer to the parent dentry for this file. This should be a
450 * directory dentry if set. If this parameter is NULL, then the
451 * file will be created in the root of the debugfs filesystem.
452 * @data: a pointer to something that the caller will want to get to later
453 * on. The inode.i_private pointer will point to this value on
454 * the open() call.
455 * @fops: a pointer to a struct file_operations that should be used for
456 * this file.
457 * @file_size: initial file size
458 *
459 * This is the basic "create a file" function for debugfs. It allows for a
460 * wide range of flexibility in creating a file, or a directory (if you want
461 * to create a directory, the debugfs_create_dir() function is
462 * recommended to be used instead.)
463 *
464 * This function will return a pointer to a dentry if it succeeds. This
465 * pointer must be passed to the debugfs_remove() function when the file is
466 * to be removed (no automatic cleanup happens if your module is unloaded,
467 * you are responsible here.) If an error occurs, %NULL will be returned.
468 *
469 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
470 * returned.
471 */
472struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
473 struct dentry *parent, void *data,
474 const struct file_operations *fops,
475 loff_t file_size)
476{
477 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
478
479 if (de)
480 d_inode(de)->i_size = file_size;
481 return de;
482}
483EXPORT_SYMBOL_GPL(debugfs_create_file_size);
484
485/**
486 * debugfs_create_dir - create a directory in the debugfs filesystem
487 * @name: a pointer to a string containing the name of the directory to
488 * create.
489 * @parent: a pointer to the parent dentry for this file. This should be a
490 * directory dentry if set. If this parameter is NULL, then the
491 * directory will be created in the root of the debugfs filesystem.
492 *
493 * This function creates a directory in debugfs with the given name.
494 *
495 * This function will return a pointer to a dentry if it succeeds. This
496 * pointer must be passed to the debugfs_remove() function when the file is
497 * to be removed (no automatic cleanup happens if your module is unloaded,
498 * you are responsible here.) If an error occurs, %NULL will be returned.
499 *
500 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
501 * returned.
502 */
503struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
504{
505 struct dentry *dentry = start_creating(name, parent);
506 struct inode *inode;
507
508 if (IS_ERR(dentry))
509 return NULL;
510
511 inode = debugfs_get_inode(dentry->d_sb);
512 if (unlikely(!inode))
513 return failed_creating(dentry);
514
515 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
516 inode->i_op = &simple_dir_inode_operations;
517 inode->i_fop = &simple_dir_operations;
518
519 /* directory inodes start off with i_nlink == 2 (for "." entry) */
520 inc_nlink(inode);
521 d_instantiate(dentry, inode);
522 inc_nlink(d_inode(dentry->d_parent));
523 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
524 return end_creating(dentry);
525}
526EXPORT_SYMBOL_GPL(debugfs_create_dir);
527
528/**
529 * debugfs_create_automount - create automount point in the debugfs filesystem
530 * @name: a pointer to a string containing the name of the file to create.
531 * @parent: a pointer to the parent dentry for this file. This should be a
532 * directory dentry if set. If this parameter is NULL, then the
533 * file will be created in the root of the debugfs filesystem.
534 * @f: function to be called when pathname resolution steps on that one.
535 * @data: opaque argument to pass to f().
536 *
537 * @f should return what ->d_automount() would.
538 */
539struct dentry *debugfs_create_automount(const char *name,
540 struct dentry *parent,
541 debugfs_automount_t f,
542 void *data)
543{
544 struct dentry *dentry = start_creating(name, parent);
545 struct inode *inode;
546
547 if (IS_ERR(dentry))
548 return NULL;
549
550 inode = debugfs_get_inode(dentry->d_sb);
551 if (unlikely(!inode))
552 return failed_creating(dentry);
553
554 make_empty_dir_inode(inode);
555 inode->i_flags |= S_AUTOMOUNT;
556 inode->i_private = data;
557 dentry->d_fsdata = (void *)f;
558 /* directory inodes start off with i_nlink == 2 (for "." entry) */
559 inc_nlink(inode);
560 d_instantiate(dentry, inode);
561 inc_nlink(d_inode(dentry->d_parent));
562 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
563 return end_creating(dentry);
564}
565EXPORT_SYMBOL(debugfs_create_automount);
566
567/**
568 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
569 * @name: a pointer to a string containing the name of the symbolic link to
570 * create.
571 * @parent: a pointer to the parent dentry for this symbolic link. This
572 * should be a directory dentry if set. If this parameter is NULL,
573 * then the symbolic link will be created in the root of the debugfs
574 * filesystem.
575 * @target: a pointer to a string containing the path to the target of the
576 * symbolic link.
577 *
578 * This function creates a symbolic link with the given name in debugfs that
579 * links to the given target path.
580 *
581 * This function will return a pointer to a dentry if it succeeds. This
582 * pointer must be passed to the debugfs_remove() function when the symbolic
583 * link is to be removed (no automatic cleanup happens if your module is
584 * unloaded, you are responsible here.) If an error occurs, %NULL will be
585 * returned.
586 *
587 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
588 * returned.
589 */
590struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
591 const char *target)
592{
593 struct dentry *dentry;
594 struct inode *inode;
595 char *link = kstrdup(target, GFP_KERNEL);
596 if (!link)
597 return NULL;
598
599 dentry = start_creating(name, parent);
600 if (IS_ERR(dentry)) {
601 kfree(link);
602 return NULL;
603 }
604
605 inode = debugfs_get_inode(dentry->d_sb);
606 if (unlikely(!inode)) {
607 kfree(link);
608 return failed_creating(dentry);
609 }
610 inode->i_mode = S_IFLNK | S_IRWXUGO;
611 inode->i_op = &simple_symlink_inode_operations;
612 inode->i_link = link;
613 d_instantiate(dentry, inode);
614 return end_creating(dentry);
615}
616EXPORT_SYMBOL_GPL(debugfs_create_symlink);
617
618static void __debugfs_remove_file(struct dentry *dentry, struct dentry *parent)
619{
620 struct debugfs_fsdata *fsd;
621
622 simple_unlink(d_inode(parent), dentry);
623 d_delete(dentry);
624
625 /*
626 * Paired with the closing smp_mb() implied by a successful
627 * cmpxchg() in debugfs_file_get(): either
628 * debugfs_file_get() must see a dead dentry or we must see a
629 * debugfs_fsdata instance at ->d_fsdata here (or both).
630 */
631 smp_mb();
632 fsd = READ_ONCE(dentry->d_fsdata);
633 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
634 return;
635 if (!refcount_dec_and_test(&fsd->active_users))
636 wait_for_completion(&fsd->active_users_drained);
637}
638
639static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
640{
641 int ret = 0;
642
643 if (simple_positive(dentry)) {
644 dget(dentry);
645 if (!d_is_reg(dentry)) {
646 if (d_is_dir(dentry))
647 ret = simple_rmdir(d_inode(parent), dentry);
648 else
649 simple_unlink(d_inode(parent), dentry);
650 if (!ret)
651 d_delete(dentry);
652 } else {
653 __debugfs_remove_file(dentry, parent);
654 }
655 dput(dentry);
656 }
657 return ret;
658}
659
660/**
661 * debugfs_remove - removes a file or directory from the debugfs filesystem
662 * @dentry: a pointer to a the dentry of the file or directory to be
663 * removed. If this parameter is NULL or an error value, nothing
664 * will be done.
665 *
666 * This function removes a file or directory in debugfs that was previously
667 * created with a call to another debugfs function (like
668 * debugfs_create_file() or variants thereof.)
669 *
670 * This function is required to be called in order for the file to be
671 * removed, no automatic cleanup of files will happen when a module is
672 * removed, you are responsible here.
673 */
674void debugfs_remove(struct dentry *dentry)
675{
676 struct dentry *parent;
677 int ret;
678
679 if (IS_ERR_OR_NULL(dentry))
680 return;
681
682 parent = dentry->d_parent;
683 inode_lock(d_inode(parent));
684 ret = __debugfs_remove(dentry, parent);
685 inode_unlock(d_inode(parent));
686 if (!ret)
687 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
688}
689EXPORT_SYMBOL_GPL(debugfs_remove);
690
691/**
692 * debugfs_remove_recursive - recursively removes a directory
693 * @dentry: a pointer to a the dentry of the directory to be removed. If this
694 * parameter is NULL or an error value, nothing will be done.
695 *
696 * This function recursively removes a directory tree in debugfs that
697 * was previously created with a call to another debugfs function
698 * (like debugfs_create_file() or variants thereof.)
699 *
700 * This function is required to be called in order for the file to be
701 * removed, no automatic cleanup of files will happen when a module is
702 * removed, you are responsible here.
703 */
704void debugfs_remove_recursive(struct dentry *dentry)
705{
706 struct dentry *child, *parent;
707
708 if (IS_ERR_OR_NULL(dentry))
709 return;
710
711 parent = dentry;
712 down:
713 inode_lock(d_inode(parent));
714 loop:
715 /*
716 * The parent->d_subdirs is protected by the d_lock. Outside that
717 * lock, the child can be unlinked and set to be freed which can
718 * use the d_u.d_child as the rcu head and corrupt this list.
719 */
720 spin_lock(&parent->d_lock);
721 list_for_each_entry(child, &parent->d_subdirs, d_child) {
722 if (!simple_positive(child))
723 continue;
724
725 /* perhaps simple_empty(child) makes more sense */
726 if (!list_empty(&child->d_subdirs)) {
727 spin_unlock(&parent->d_lock);
728 inode_unlock(d_inode(parent));
729 parent = child;
730 goto down;
731 }
732
733 spin_unlock(&parent->d_lock);
734
735 if (!__debugfs_remove(child, parent))
736 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
737
738 /*
739 * The parent->d_lock protects agaist child from unlinking
740 * from d_subdirs. When releasing the parent->d_lock we can
741 * no longer trust that the next pointer is valid.
742 * Restart the loop. We'll skip this one with the
743 * simple_positive() check.
744 */
745 goto loop;
746 }
747 spin_unlock(&parent->d_lock);
748
749 inode_unlock(d_inode(parent));
750 child = parent;
751 parent = parent->d_parent;
752 inode_lock(d_inode(parent));
753
754 if (child != dentry)
755 /* go up */
756 goto loop;
757
758 if (!__debugfs_remove(child, parent))
759 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
760 inode_unlock(d_inode(parent));
761}
762EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
763
764/**
765 * debugfs_rename - rename a file/directory in the debugfs filesystem
766 * @old_dir: a pointer to the parent dentry for the renamed object. This
767 * should be a directory dentry.
768 * @old_dentry: dentry of an object to be renamed.
769 * @new_dir: a pointer to the parent dentry where the object should be
770 * moved. This should be a directory dentry.
771 * @new_name: a pointer to a string containing the target name.
772 *
773 * This function renames a file/directory in debugfs. The target must not
774 * exist for rename to succeed.
775 *
776 * This function will return a pointer to old_dentry (which is updated to
777 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
778 * returned.
779 *
780 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
781 * returned.
782 */
783struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
784 struct dentry *new_dir, const char *new_name)
785{
786 int error;
787 struct dentry *dentry = NULL, *trap;
788 struct name_snapshot old_name;
789
790 trap = lock_rename(new_dir, old_dir);
791 /* Source or destination directories don't exist? */
792 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
793 goto exit;
794 /* Source does not exist, cyclic rename, or mountpoint? */
795 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
796 d_mountpoint(old_dentry))
797 goto exit;
798 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
799 /* Lookup failed, cyclic rename or target exists? */
800 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
801 goto exit;
802
803 take_dentry_name_snapshot(&old_name, old_dentry);
804
805 error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
806 dentry, 0);
807 if (error) {
808 release_dentry_name_snapshot(&old_name);
809 goto exit;
810 }
811 d_move(old_dentry, dentry);
812 fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name.name,
813 d_is_dir(old_dentry),
814 NULL, old_dentry);
815 release_dentry_name_snapshot(&old_name);
816 unlock_rename(new_dir, old_dir);
817 dput(dentry);
818 return old_dentry;
819exit:
820 if (dentry && !IS_ERR(dentry))
821 dput(dentry);
822 unlock_rename(new_dir, old_dir);
823 return NULL;
824}
825EXPORT_SYMBOL_GPL(debugfs_rename);
826
827/**
828 * debugfs_initialized - Tells whether debugfs has been registered
829 */
830bool debugfs_initialized(void)
831{
832 return debugfs_registered;
833}
834EXPORT_SYMBOL_GPL(debugfs_initialized);
835
836static int __init debugfs_init(void)
837{
838 int retval;
839
840 retval = sysfs_create_mount_point(kernel_kobj, "debug");
841 if (retval)
842 return retval;
843
844 retval = register_filesystem(&debug_fs_type);
845 if (retval)
846 sysfs_remove_mount_point(kernel_kobj, "debug");
847 else
848 debugfs_registered = true;
849
850 return retval;
851}
852core_initcall(debugfs_init);
853