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 bool debugfs_enabled __ro_after_init = IS_ENABLED(CONFIG_DEBUG_FS_ALLOW_ALL);
39
40/*
41 * Don't allow access attributes to be changed whilst the kernel is locked down
42 * so that we can use the file mode as part of a heuristic to determine whether
43 * to lock down individual files.
44 */
45static int debugfs_setattr(struct mnt_idmap *idmap,
46 struct dentry *dentry, struct iattr *ia)
47{
48 int ret;
49
50 if (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) {
51 ret = security_locked_down(what: LOCKDOWN_DEBUGFS);
52 if (ret)
53 return ret;
54 }
55 return simple_setattr(&nop_mnt_idmap, dentry, ia);
56}
57
58static const struct inode_operations debugfs_file_inode_operations = {
59 .setattr = debugfs_setattr,
60};
61static const struct inode_operations debugfs_dir_inode_operations = {
62 .lookup = simple_lookup,
63 .setattr = debugfs_setattr,
64};
65static const struct inode_operations debugfs_symlink_inode_operations = {
66 .get_link = simple_get_link,
67 .setattr = debugfs_setattr,
68};
69
70static struct inode *debugfs_get_inode(struct super_block *sb)
71{
72 struct inode *inode = new_inode(sb);
73 if (inode) {
74 inode->i_ino = get_next_ino();
75 simple_inode_init_ts(inode);
76 }
77 return inode;
78}
79
80struct debugfs_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, desc: debugfs_param_specs, param, result: &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(dentry: 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, remount: false);
173}
174
175static void debugfs_apply_options_remount(struct super_block *sb)
176{
177 _debugfs_apply_options(sb, remount: 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 if (!new_opts)
187 return 0;
188
189 sync_filesystem(sb);
190
191 /* structure copy of new mount options to sb */
192 *sb_opts = *new_opts;
193 debugfs_apply_options_remount(sb);
194
195 return 0;
196}
197
198static int debugfs_show_options(struct seq_file *m, struct dentry *root)
199{
200 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
201
202 if (!uid_eq(left: fsi->uid, GLOBAL_ROOT_UID))
203 seq_printf(m, ",uid=%u",
204 from_kuid_munged(&init_user_ns, fsi->uid));
205 if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))
206 seq_printf(m, ",gid=%u",
207 from_kgid_munged(&init_user_ns, fsi->gid));
208 if (fsi->mode != DEBUGFS_DEFAULT_MODE)
209 seq_printf(m, ",mode=%o", fsi->mode);
210
211 return 0;
212}
213
214static struct kmem_cache *debugfs_inode_cachep __ro_after_init;
215
216static void init_once(void *foo)
217{
218 struct debugfs_inode_info *info = foo;
219 inode_init_once(&info->vfs_inode);
220}
221
222static struct inode *debugfs_alloc_inode(struct super_block *sb)
223{
224 struct debugfs_inode_info *info;
225 info = alloc_inode_sb(sb, debugfs_inode_cachep, GFP_KERNEL);
226 if (!info)
227 return NULL;
228 return &info->vfs_inode;
229}
230
231static void debugfs_free_inode(struct inode *inode)
232{
233 if (S_ISLNK(inode->i_mode))
234 kfree(objp: inode->i_link);
235 kmem_cache_free(s: debugfs_inode_cachep, objp: DEBUGFS_I(inode));
236}
237
238static const struct super_operations debugfs_super_operations = {
239 .statfs = simple_statfs,
240 .show_options = debugfs_show_options,
241 .alloc_inode = debugfs_alloc_inode,
242 .free_inode = debugfs_free_inode,
243};
244
245static void debugfs_release_dentry(struct dentry *dentry)
246{
247 struct debugfs_fsdata *fsd = dentry->d_fsdata;
248
249 if (fsd) {
250 WARN_ON(!list_empty(&fsd->cancellations));
251 mutex_destroy(lock: &fsd->cancellations_mtx);
252 }
253 kfree(objp: fsd);
254}
255
256static struct vfsmount *debugfs_automount(struct path *path)
257{
258 struct inode *inode = path->dentry->d_inode;
259
260 return DEBUGFS_I(inode)->automount(path->dentry, inode->i_private);
261}
262
263static const struct dentry_operations debugfs_dops = {
264 .d_release = debugfs_release_dentry,
265 .d_automount = debugfs_automount,
266};
267
268static int debugfs_fill_super(struct super_block *sb, struct fs_context *fc)
269{
270 static const struct tree_descr debug_files[] = {{""}};
271 int err;
272
273 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
274 if (err)
275 return err;
276
277 sb->s_op = &debugfs_super_operations;
278 set_default_d_op(sb, &debugfs_dops);
279 sb->s_d_flags |= DCACHE_DONTCACHE;
280
281 debugfs_apply_options(sb);
282
283 return 0;
284}
285
286static int debugfs_get_tree(struct fs_context *fc)
287{
288 int err;
289
290 err = get_tree_single(fc, fill_super: debugfs_fill_super);
291 if (err)
292 return err;
293
294 return debugfs_reconfigure(fc);
295}
296
297static void debugfs_free_fc(struct fs_context *fc)
298{
299 kfree(objp: fc->s_fs_info);
300}
301
302static const struct fs_context_operations debugfs_context_ops = {
303 .free = debugfs_free_fc,
304 .parse_param = debugfs_parse_param,
305 .get_tree = debugfs_get_tree,
306 .reconfigure = debugfs_reconfigure,
307};
308
309static int debugfs_init_fs_context(struct fs_context *fc)
310{
311 struct debugfs_fs_info *fsi;
312
313 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
314 if (!fsi)
315 return -ENOMEM;
316
317 fsi->mode = DEBUGFS_DEFAULT_MODE;
318
319 fc->s_fs_info = fsi;
320 fc->ops = &debugfs_context_ops;
321 return 0;
322}
323
324static struct file_system_type debug_fs_type = {
325 .owner = THIS_MODULE,
326 .name = "debugfs",
327 .init_fs_context = debugfs_init_fs_context,
328 .parameters = debugfs_param_specs,
329 .kill_sb = kill_anon_super,
330};
331MODULE_ALIAS_FS("debugfs");
332
333/**
334 * debugfs_lookup() - look up an existing debugfs file
335 * @name: a pointer to a string containing the name of the file to look up.
336 * @parent: a pointer to the parent dentry of the file.
337 *
338 * This function will return a pointer to a dentry if it succeeds. If the file
339 * doesn't exist or an error occurs, %NULL will be returned. The returned
340 * dentry must be passed to dput() when it is no longer needed.
341 *
342 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
343 * returned.
344 */
345struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
346{
347 struct dentry *dentry;
348
349 if (!debugfs_initialized() || IS_ERR_OR_NULL(ptr: name) || IS_ERR(ptr: parent))
350 return NULL;
351
352 if (!parent)
353 parent = debugfs_mount->mnt_root;
354
355 dentry = lookup_noperm_positive_unlocked(&QSTR(name), parent);
356 if (IS_ERR(ptr: dentry))
357 return NULL;
358 return dentry;
359}
360EXPORT_SYMBOL_GPL(debugfs_lookup);
361
362static struct dentry *debugfs_start_creating(const char *name,
363 struct dentry *parent)
364{
365 struct dentry *dentry;
366 int error;
367
368 if (!debugfs_enabled)
369 return ERR_PTR(error: -EPERM);
370
371 if (!debugfs_initialized())
372 return ERR_PTR(error: -ENOENT);
373
374 pr_debug("creating file '%s'\n", name);
375
376 if (IS_ERR(ptr: parent))
377 return parent;
378
379 error = simple_pin_fs(&debug_fs_type, mount: &debugfs_mount,
380 count: &debugfs_mount_count);
381 if (error) {
382 pr_err("Unable to pin filesystem for file '%s'\n", name);
383 return ERR_PTR(error);
384 }
385
386 /* If the parent is not specified, we create it in the root.
387 * We need the root dentry to do this, which is in the super
388 * block. A pointer to that is in the struct vfsmount that we
389 * have around.
390 */
391 if (!parent)
392 parent = debugfs_mount->mnt_root;
393
394 dentry = simple_start_creating(parent, name);
395 if (IS_ERR(ptr: dentry)) {
396 if (dentry == ERR_PTR(error: -EEXIST))
397 pr_err("'%s' already exists in '%pd'\n", name, parent);
398 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
399 }
400 return dentry;
401}
402
403static struct dentry *debugfs_failed_creating(struct dentry *dentry)
404{
405 simple_done_creating(dentry);
406 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
407 return ERR_PTR(error: -ENOMEM);
408}
409
410static struct dentry *debugfs_end_creating(struct dentry *dentry)
411{
412 simple_done_creating(dentry);
413 return dentry; // borrowed
414}
415
416static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
417 struct dentry *parent, void *data,
418 const void *aux,
419 const struct file_operations *proxy_fops,
420 const void *real_fops)
421{
422 struct dentry *dentry;
423 struct inode *inode;
424
425 if (!(mode & S_IFMT))
426 mode |= S_IFREG;
427 BUG_ON(!S_ISREG(mode));
428 dentry = debugfs_start_creating(name, parent);
429
430 if (IS_ERR(ptr: dentry))
431 return dentry;
432
433 inode = debugfs_get_inode(sb: dentry->d_sb);
434 if (unlikely(!inode)) {
435 pr_err("out of free dentries, can not create file '%s'\n",
436 name);
437 return debugfs_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 if (!real_fops)
445 proxy_fops = &debugfs_noop_file_operations;
446 inode->i_fop = proxy_fops;
447 DEBUGFS_I(inode)->raw = real_fops;
448 DEBUGFS_I(inode)->aux = (void *)aux;
449
450 d_make_persistent(dentry, inode);
451 fsnotify_create(dir: d_inode(dentry: dentry->d_parent), dentry);
452 return debugfs_end_creating(dentry);
453}
454
455struct dentry *debugfs_create_file_full(const char *name, umode_t mode,
456 struct dentry *parent, void *data,
457 const void *aux,
458 const struct file_operations *fops)
459{
460 return __debugfs_create_file(name, mode, parent, data, aux,
461 proxy_fops: &debugfs_full_proxy_file_operations,
462 real_fops: fops);
463}
464EXPORT_SYMBOL_GPL(debugfs_create_file_full);
465
466struct dentry *debugfs_create_file_short(const char *name, umode_t mode,
467 struct dentry *parent, void *data,
468 const void *aux,
469 const struct debugfs_short_fops *fops)
470{
471 return __debugfs_create_file(name, mode, parent, data, aux,
472 proxy_fops: &debugfs_full_short_proxy_file_operations,
473 real_fops: fops);
474}
475EXPORT_SYMBOL_GPL(debugfs_create_file_short);
476
477/**
478 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
479 * @name: a pointer to a string containing the name of the file to create.
480 * @mode: the permission that the file should have.
481 * @parent: a pointer to the parent dentry for this file. This should be a
482 * directory dentry if set. If this parameter is NULL, then the
483 * file will be created in the root of the debugfs filesystem.
484 * @data: a pointer to something that the caller will want to get to later
485 * on. The inode.i_private pointer will point to this value on
486 * the open() call.
487 * @fops: a pointer to a struct file_operations that should be used for
488 * this file.
489 *
490 * debugfs_create_file_unsafe() is completely analogous to
491 * debugfs_create_file(), the only difference being that the fops
492 * handed it will not get protected against file removals by the
493 * debugfs core.
494 *
495 * It is your responsibility to protect your struct file_operation
496 * methods against file removals by means of debugfs_file_get()
497 * and debugfs_file_put(). ->open() is still protected by
498 * debugfs though.
499 *
500 * Any struct file_operations defined by means of
501 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
502 * thus, may be used here.
503 */
504struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
505 struct dentry *parent, void *data,
506 const struct file_operations *fops)
507{
508
509 return __debugfs_create_file(name, mode, parent, data, NULL,
510 proxy_fops: &debugfs_open_proxy_file_operations,
511 real_fops: fops);
512}
513EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
514
515/**
516 * debugfs_create_file_size - create a file in the debugfs filesystem
517 * @name: a pointer to a string containing the name of the file to create.
518 * @mode: the permission that the file should have.
519 * @parent: a pointer to the parent dentry for this file. This should be a
520 * directory dentry if set. If this parameter is NULL, then the
521 * file will be created in the root of the debugfs filesystem.
522 * @data: a pointer to something that the caller will want to get to later
523 * on. The inode.i_private pointer will point to this value on
524 * the open() call.
525 * @fops: a pointer to a struct file_operations that should be used for
526 * this file.
527 * @file_size: initial file size
528 *
529 * This is the basic "create a file" function for debugfs. It allows for a
530 * wide range of flexibility in creating a file, or a directory (if you want
531 * to create a directory, the debugfs_create_dir() function is
532 * recommended to be used instead.)
533 */
534void debugfs_create_file_size(const char *name, umode_t mode,
535 struct dentry *parent, void *data,
536 const struct file_operations *fops,
537 loff_t file_size)
538{
539 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
540
541 if (!IS_ERR(ptr: de))
542 d_inode(dentry: de)->i_size = file_size;
543}
544EXPORT_SYMBOL_GPL(debugfs_create_file_size);
545
546/**
547 * debugfs_create_dir - create a directory in the debugfs filesystem
548 * @name: a pointer to a string containing the name of the directory to
549 * create.
550 * @parent: a pointer to the parent dentry for this file. This should be a
551 * directory dentry if set. If this parameter is NULL, then the
552 * directory will be created in the root of the debugfs filesystem.
553 *
554 * This function creates a directory in debugfs with the given name.
555 *
556 * This function will return a pointer to a dentry if it succeeds. This
557 * pointer must be passed to the debugfs_remove() function when the file is
558 * to be removed (no automatic cleanup happens if your module is unloaded,
559 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
560 * returned.
561 *
562 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
563 * returned.
564 *
565 * NOTE: it's expected that most callers should _ignore_ the errors returned
566 * by this function. Other debugfs functions handle the fact that the "dentry"
567 * passed to them could be an error and they don't crash in that case.
568 * Drivers should generally work fine even if debugfs fails to init anyway.
569 */
570struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
571{
572 struct dentry *dentry = debugfs_start_creating(name, parent);
573 struct inode *inode;
574
575 if (IS_ERR(ptr: dentry))
576 return dentry;
577
578 inode = debugfs_get_inode(sb: dentry->d_sb);
579 if (unlikely(!inode)) {
580 pr_err("out of free dentries, can not create directory '%s'\n",
581 name);
582 return debugfs_failed_creating(dentry);
583 }
584
585 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
586 inode->i_op = &debugfs_dir_inode_operations;
587 inode->i_fop = &simple_dir_operations;
588
589 /* directory inodes start off with i_nlink == 2 (for "." entry) */
590 inc_nlink(inode);
591 d_make_persistent(dentry, inode);
592 inc_nlink(inode: d_inode(dentry: dentry->d_parent));
593 fsnotify_mkdir(dir: d_inode(dentry: dentry->d_parent), dentry);
594 return debugfs_end_creating(dentry);
595}
596EXPORT_SYMBOL_GPL(debugfs_create_dir);
597
598/**
599 * debugfs_create_automount - create automount point in the debugfs filesystem
600 * @name: a pointer to a string containing the name of the file to create.
601 * @parent: a pointer to the parent dentry for this file. This should be a
602 * directory dentry if set. If this parameter is NULL, then the
603 * file will be created in the root of the debugfs filesystem.
604 * @f: function to be called when pathname resolution steps on that one.
605 * @data: opaque argument to pass to f().
606 *
607 * @f should return what ->d_automount() would.
608 */
609struct dentry *debugfs_create_automount(const char *name,
610 struct dentry *parent,
611 debugfs_automount_t f,
612 void *data)
613{
614 struct dentry *dentry = debugfs_start_creating(name, parent);
615 struct inode *inode;
616
617 if (IS_ERR(ptr: dentry))
618 return dentry;
619
620 inode = debugfs_get_inode(sb: dentry->d_sb);
621 if (unlikely(!inode)) {
622 pr_err("out of free dentries, can not create automount '%s'\n",
623 name);
624 return debugfs_failed_creating(dentry);
625 }
626
627 make_empty_dir_inode(inode);
628 inode->i_flags |= S_AUTOMOUNT;
629 inode->i_private = data;
630 DEBUGFS_I(inode)->automount = f;
631 /* directory inodes start off with i_nlink == 2 (for "." entry) */
632 inc_nlink(inode);
633 d_make_persistent(dentry, inode);
634 inc_nlink(inode: d_inode(dentry: dentry->d_parent));
635 fsnotify_mkdir(dir: d_inode(dentry: dentry->d_parent), dentry);
636 return debugfs_end_creating(dentry);
637}
638EXPORT_SYMBOL(debugfs_create_automount);
639
640/**
641 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
642 * @name: a pointer to a string containing the name of the symbolic link to
643 * create.
644 * @parent: a pointer to the parent dentry for this symbolic link. This
645 * should be a directory dentry if set. If this parameter is NULL,
646 * then the symbolic link will be created in the root of the debugfs
647 * filesystem.
648 * @target: a pointer to a string containing the path to the target of the
649 * symbolic link.
650 *
651 * This function creates a symbolic link with the given name in debugfs that
652 * links to the given target path.
653 *
654 * This function will return a pointer to a dentry if it succeeds. This
655 * pointer must be passed to the debugfs_remove() function when the symbolic
656 * link is to be removed (no automatic cleanup happens if your module is
657 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
658 * will be returned.
659 *
660 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
661 * returned.
662 */
663struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
664 const char *target)
665{
666 struct dentry *dentry;
667 struct inode *inode;
668 char *link = kstrdup(s: target, GFP_KERNEL);
669 if (!link)
670 return ERR_PTR(error: -ENOMEM);
671
672 dentry = debugfs_start_creating(name, parent);
673 if (IS_ERR(ptr: dentry)) {
674 kfree(objp: link);
675 return dentry;
676 }
677
678 inode = debugfs_get_inode(sb: dentry->d_sb);
679 if (unlikely(!inode)) {
680 pr_err("out of free dentries, can not create symlink '%s'\n",
681 name);
682 kfree(objp: link);
683 return debugfs_failed_creating(dentry);
684 }
685 inode->i_mode = S_IFLNK | S_IRWXUGO;
686 inode->i_op = &debugfs_symlink_inode_operations;
687 inode->i_link = link;
688 d_make_persistent(dentry, inode);
689 return debugfs_end_creating(dentry);
690}
691EXPORT_SYMBOL_GPL(debugfs_create_symlink);
692
693static void __debugfs_file_removed(struct dentry *dentry)
694{
695 struct debugfs_fsdata *fsd;
696
697 /*
698 * Paired with the closing smp_mb() implied by a successful
699 * cmpxchg() in debugfs_file_get(): either
700 * debugfs_file_get() must see a dead dentry or we must see a
701 * debugfs_fsdata instance at ->d_fsdata here (or both).
702 */
703 smp_mb();
704 fsd = READ_ONCE(dentry->d_fsdata);
705 if (!fsd)
706 return;
707
708 /* if this was the last reference, we're done */
709 if (refcount_dec_and_test(r: &fsd->active_users))
710 return;
711
712 /*
713 * If there's still a reference, the code that obtained it can
714 * be in different states:
715 * - The common case of not using cancellations, or already
716 * after debugfs_leave_cancellation(), where we just need
717 * to wait for debugfs_file_put() which signals the completion;
718 * - inside a cancellation section, i.e. between
719 * debugfs_enter_cancellation() and debugfs_leave_cancellation(),
720 * in which case we need to trigger the ->cancel() function,
721 * and then wait for debugfs_file_put() just like in the
722 * previous case;
723 * - before debugfs_enter_cancellation() (but obviously after
724 * debugfs_file_get()), in which case we may not see the
725 * cancellation in the list on the first round of the loop,
726 * but debugfs_enter_cancellation() signals the completion
727 * after adding it, so this code gets woken up to call the
728 * ->cancel() function.
729 */
730 while (refcount_read(r: &fsd->active_users)) {
731 struct debugfs_cancellation *c;
732
733 /*
734 * Lock the cancellations. Note that the cancellations
735 * structs are meant to be on the stack, so we need to
736 * ensure we either use them here or don't touch them,
737 * and debugfs_leave_cancellation() will wait for this
738 * to be finished processing before exiting one. It may
739 * of course win and remove the cancellation, but then
740 * chances are we never even got into this bit, we only
741 * do if the refcount isn't zero already.
742 */
743 mutex_lock(&fsd->cancellations_mtx);
744 while ((c = list_first_entry_or_null(&fsd->cancellations,
745 typeof(*c), list))) {
746 list_del_init(entry: &c->list);
747 c->cancel(dentry, c->cancel_data);
748 }
749 mutex_unlock(lock: &fsd->cancellations_mtx);
750
751 wait_for_completion(&fsd->active_users_drained);
752 }
753}
754
755static void remove_one(struct dentry *victim)
756{
757 if (d_is_reg(dentry: victim))
758 __debugfs_file_removed(dentry: victim);
759 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
760}
761
762/**
763 * debugfs_remove - recursively removes a directory
764 * @dentry: a pointer to a the dentry of the directory to be removed. If this
765 * parameter is NULL or an error value, nothing will be done.
766 *
767 * This function recursively removes a directory tree in debugfs that
768 * was previously created with a call to another debugfs function
769 * (like debugfs_create_file() or variants thereof.)
770 *
771 * This function is required to be called in order for the file to be
772 * removed, no automatic cleanup of files will happen when a module is
773 * removed, you are responsible here.
774 */
775void debugfs_remove(struct dentry *dentry)
776{
777 if (IS_ERR_OR_NULL(ptr: dentry))
778 return;
779
780 simple_pin_fs(&debug_fs_type, mount: &debugfs_mount, count: &debugfs_mount_count);
781 simple_recursive_removal(dentry, callback: remove_one);
782 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
783}
784EXPORT_SYMBOL_GPL(debugfs_remove);
785
786/**
787 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
788 * @name: a pointer to a string containing the name of the item to look up.
789 * @parent: a pointer to the parent dentry of the item.
790 *
791 * This is the equlivant of doing something like
792 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
793 * handled for the directory being looked up.
794 */
795void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
796{
797 struct dentry *dentry;
798
799 dentry = debugfs_lookup(name, parent);
800 if (!dentry)
801 return;
802
803 debugfs_remove(dentry);
804 dput(dentry);
805}
806EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
807
808/**
809 * debugfs_change_name - rename a file/directory in the debugfs filesystem
810 * @dentry: dentry of an object to be renamed.
811 * @fmt: format for new name
812 *
813 * This function renames a file/directory in debugfs. The target must not
814 * exist for rename to succeed.
815 *
816 * This function will return 0 on success and -E... on failure.
817 *
818 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
819 * returned.
820 */
821int __printf(2, 3) debugfs_change_name(struct dentry *dentry, const char *fmt, ...)
822{
823 int error = 0;
824 const char *new_name;
825 struct name_snapshot old_name;
826 struct dentry *target;
827 struct renamedata rd = {};
828 struct inode *dir;
829 va_list ap;
830
831 if (IS_ERR_OR_NULL(ptr: dentry))
832 return 0;
833
834 va_start(ap, fmt);
835 new_name = kvasprintf_const(GFP_KERNEL, fmt, args: ap);
836 va_end(ap);
837 if (!new_name)
838 return -ENOMEM;
839
840 rd.old_parent = dget_parent(dentry);
841 rd.new_parent = rd.old_parent;
842 rd.flags = RENAME_NOREPLACE;
843 target = lookup_noperm_unlocked(&QSTR(new_name), rd.new_parent);
844 if (IS_ERR(ptr: target)) {
845 error = PTR_ERR(ptr: target);
846 goto out_free;
847 }
848
849 error = start_renaming_two_dentries(rd: &rd, old_dentry: dentry, new_dentry: target);
850 if (error) {
851 if (error == -EEXIST && target == dentry)
852 /* it isn't an error to rename a thing to itself */
853 error = 0;
854 goto out;
855 }
856
857 dir = d_inode(dentry: rd.old_parent);
858 take_dentry_name_snapshot(&old_name, dentry);
859 simple_rename_timestamp(old_dir: dir, old_dentry: dentry, new_dir: dir, new_dentry: rd.new_dentry);
860 d_move(dentry, rd.new_dentry);
861 fsnotify_move(old_dir: dir, new_dir: dir, old_name: &old_name.name, isdir: d_is_dir(dentry), NULL, moved: dentry);
862 release_dentry_name_snapshot(&old_name);
863 end_renaming(rd: &rd);
864out:
865 dput(rd.old_parent);
866 dput(target);
867out_free:
868 kfree_const(x: new_name);
869 return error;
870}
871EXPORT_SYMBOL_GPL(debugfs_change_name);
872
873/**
874 * debugfs_initialized - Tells whether debugfs has been registered
875 */
876bool debugfs_initialized(void)
877{
878 return debugfs_registered;
879}
880EXPORT_SYMBOL_GPL(debugfs_initialized);
881
882static int __init debugfs_kernel(char *str)
883{
884 if (str) {
885 if (!strcmp(str, "on"))
886 debugfs_enabled = true;
887 else if (!strcmp(str, "off"))
888 debugfs_enabled = false;
889 else if (!strcmp(str, "no-mount")) {
890 pr_notice("debugfs=no-mount is a deprecated alias "
891 "for debugfs=off\n");
892 debugfs_enabled = false;
893 }
894 }
895
896 return 0;
897}
898early_param("debugfs", debugfs_kernel);
899
900static int __init debugfs_init(void)
901{
902 int retval;
903
904 if (!debugfs_enabled)
905 return -EPERM;
906
907 retval = sysfs_create_mount_point(parent_kobj: kernel_kobj, name: "debug");
908 if (retval)
909 return retval;
910
911 debugfs_inode_cachep = kmem_cache_create("debugfs_inode_cache",
912 sizeof(struct debugfs_inode_info), 0,
913 SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
914 init_once);
915 if (debugfs_inode_cachep == NULL) {
916 sysfs_remove_mount_point(parent_kobj: kernel_kobj, name: "debug");
917 return -ENOMEM;
918 }
919
920 retval = register_filesystem(&debug_fs_type);
921 if (retval) { // Really not going to happen
922 sysfs_remove_mount_point(parent_kobj: kernel_kobj, name: "debug");
923 kmem_cache_destroy(s: debugfs_inode_cachep);
924 return retval;
925 }
926 debugfs_registered = true;
927 return 0;
928}
929core_initcall(debugfs_init);
930

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