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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 <[email protected]>
6 * Copyright (C) 2004 IBM Inc.
7 * Copyright (C) 2019 Linux Foundation <[email protected]>
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(const 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 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(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(inode->i_link);
235 kmem_cache_free(debugfs_inode_cachep, 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(&fsd->cancellations_mtx);
252 }
253 kfree(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, 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(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_obj(struct debugfs_fs_info);
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(name) || IS_ERR(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(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(-EPERM);
370
371 if (IS_ERR(parent))
372 return parent;
373
374 if (!debugfs_initialized()) {
375 pr_err("Unable to create file '%s', debugfs is not initialized yet\n",
376 name);
377 return ERR_PTR(-ENOENT);
378 }
379
380 pr_debug("creating file '%s'\n", name);
381
382 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
383 &debugfs_mount_count);
384 if (error) {
385 pr_err("Unable to pin filesystem for file '%s'\n", name);
386 return ERR_PTR(error);
387 }
388
389 /* If the parent is not specified, we create it in the root.
390 * We need the root dentry to do this, which is in the super
391 * block. A pointer to that is in the struct vfsmount that we
392 * have around.
393 */
394 if (!parent)
395 parent = debugfs_mount->mnt_root;
396
397 dentry = simple_start_creating(parent, name);
398 if (IS_ERR(dentry)) {
399 if (dentry == ERR_PTR(-EEXIST))
400 pr_err("'%s' already exists in '%pd'\n", name, parent);
401 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
402 }
403 return dentry;
404}
405
406static struct dentry *debugfs_failed_creating(struct dentry *dentry)
407{
408 simple_done_creating(dentry);
409 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
410 return ERR_PTR(-ENOMEM);
411}
412
413static struct dentry *debugfs_end_creating(struct dentry *dentry)
414{
415 simple_done_creating(dentry);
416 return dentry; // borrowed
417}
418
419static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
420 struct dentry *parent, void *data,
421 const void *aux,
422 const struct file_operations *proxy_fops,
423 const void *real_fops)
424{
425 struct dentry *dentry;
426 struct inode *inode;
427
428 if (!(mode & S_IFMT))
429 mode |= S_IFREG;
430 BUG_ON(!S_ISREG(mode));
431 dentry = debugfs_start_creating(name, parent);
432
433 if (IS_ERR(dentry))
434 return dentry;
435
436 inode = debugfs_get_inode(dentry->d_sb);
437 if (unlikely(!inode)) {
438 pr_err("out of free dentries, can not create file '%s'\n",
439 name);
440 return debugfs_failed_creating(dentry);
441 }
442
443 inode->i_mode = mode;
444 inode->i_private = data;
445
446 inode->i_op = &debugfs_file_inode_operations;
447 if (!real_fops)
448 proxy_fops = &debugfs_noop_file_operations;
449 inode->i_fop = proxy_fops;
450 DEBUGFS_I(inode)->raw = real_fops;
451 DEBUGFS_I(inode)->aux = (void *)aux;
452
453 d_make_persistent(dentry, inode);
454 fsnotify_create(d_inode(dentry->d_parent), dentry);
455 return debugfs_end_creating(dentry);
456}
457
458struct dentry *debugfs_create_file_full(const char *name, umode_t mode,
459 struct dentry *parent, void *data,
460 const void *aux,
461 const struct file_operations *fops)
462{
463 return __debugfs_create_file(name, mode, parent, data, aux,
464 &debugfs_full_proxy_file_operations,
465 fops);
466}
467EXPORT_SYMBOL_GPL(debugfs_create_file_full);
468
469struct dentry *debugfs_create_file_short(const char *name, umode_t mode,
470 struct dentry *parent, void *data,
471 const void *aux,
472 const struct debugfs_short_fops *fops)
473{
474 return __debugfs_create_file(name, mode, parent, data, aux,
475 &debugfs_full_short_proxy_file_operations,
476 fops);
477}
478EXPORT_SYMBOL_GPL(debugfs_create_file_short);
479
480/**
481 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
482 * @name: a pointer to a string containing the name of the file to create.
483 * @mode: the permission that the file should have.
484 * @parent: a pointer to the parent dentry for this file. This should be a
485 * directory dentry if set. If this parameter is NULL, then the
486 * file will be created in the root of the debugfs filesystem.
487 * @data: a pointer to something that the caller will want to get to later
488 * on. The inode.i_private pointer will point to this value on
489 * the open() call.
490 * @fops: a pointer to a struct file_operations that should be used for
491 * this file.
492 *
493 * debugfs_create_file_unsafe() is completely analogous to
494 * debugfs_create_file(), the only difference being that the fops
495 * handed it will not get protected against file removals by the
496 * debugfs core.
497 *
498 * It is your responsibility to protect your struct file_operation
499 * methods against file removals by means of debugfs_file_get()
500 * and debugfs_file_put(). ->open() is still protected by
501 * debugfs though.
502 *
503 * Any struct file_operations defined by means of
504 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
505 * thus, may be used here.
506 */
507struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
508 struct dentry *parent, void *data,
509 const struct file_operations *fops)
510{
511
512 return __debugfs_create_file(name, mode, parent, data, NULL,
513 &debugfs_open_proxy_file_operations,
514 fops);
515}
516EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
517
518/**
519 * debugfs_create_file_size - create a file in the debugfs filesystem
520 * @name: a pointer to a string containing the name of the file to create.
521 * @mode: the permission that the file should have.
522 * @parent: a pointer to the parent dentry for this file. This should be a
523 * directory dentry if set. If this parameter is NULL, then the
524 * file will be created in the root of the debugfs filesystem.
525 * @data: a pointer to something that the caller will want to get to later
526 * on. The inode.i_private pointer will point to this value on
527 * the open() call.
528 * @fops: a pointer to a struct file_operations that should be used for
529 * this file.
530 * @file_size: initial file size
531 *
532 * This is the basic "create a file" function for debugfs. It allows for a
533 * wide range of flexibility in creating a file, or a directory (if you want
534 * to create a directory, the debugfs_create_dir() function is
535 * recommended to be used instead.)
536 */
537void debugfs_create_file_size(const char *name, umode_t mode,
538 struct dentry *parent, void *data,
539 const struct file_operations *fops,
540 loff_t file_size)
541{
542 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
543
544 if (!IS_ERR(de))
545 d_inode(de)->i_size = file_size;
546}
547EXPORT_SYMBOL_GPL(debugfs_create_file_size);
548
549/**
550 * debugfs_create_dir - create a directory in the debugfs filesystem
551 * @name: a pointer to a string containing the name of the directory to
552 * create.
553 * @parent: a pointer to the parent dentry for this file. This should be a
554 * directory dentry if set. If this parameter is NULL, then the
555 * directory will be created in the root of the debugfs filesystem.
556 *
557 * This function creates a directory in debugfs with the given name.
558 *
559 * This function will return a pointer to a dentry if it succeeds. This
560 * pointer must be passed to the debugfs_remove() function when the file is
561 * to be removed (no automatic cleanup happens if your module is unloaded,
562 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
563 * returned.
564 *
565 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
566 * returned.
567 *
568 * NOTE: it's expected that most callers should _ignore_ the errors returned
569 * by this function. Other debugfs functions handle the fact that the "dentry"
570 * passed to them could be an error and they don't crash in that case.
571 * Drivers should generally work fine even if debugfs fails to init anyway.
572 */
573struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
574{
575 struct dentry *dentry = debugfs_start_creating(name, parent);
576 struct inode *inode;
577
578 if (IS_ERR(dentry))
579 return dentry;
580
581 inode = debugfs_get_inode(dentry->d_sb);
582 if (unlikely(!inode)) {
583 pr_err("out of free dentries, can not create directory '%s'\n",
584 name);
585 return debugfs_failed_creating(dentry);
586 }
587
588 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
589 inode->i_op = &debugfs_dir_inode_operations;
590 inode->i_fop = &simple_dir_operations;
591
592 /* directory inodes start off with i_nlink == 2 (for "." entry) */
593 inc_nlink(inode);
594 d_make_persistent(dentry, inode);
595 inc_nlink(d_inode(dentry->d_parent));
596 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
597 return debugfs_end_creating(dentry);
598}
599EXPORT_SYMBOL_GPL(debugfs_create_dir);
600
601/**
602 * debugfs_create_automount - create automount point in the debugfs filesystem
603 * @name: a pointer to a string containing the name of the file to create.
604 * @parent: a pointer to the parent dentry for this file. This should be a
605 * directory dentry if set. If this parameter is NULL, then the
606 * file will be created in the root of the debugfs filesystem.
607 * @f: function to be called when pathname resolution steps on that one.
608 * @data: opaque argument to pass to f().
609 *
610 * @f should return what ->d_automount() would.
611 */
612struct dentry *debugfs_create_automount(const char *name,
613 struct dentry *parent,
614 debugfs_automount_t f,
615 void *data)
616{
617 struct dentry *dentry = debugfs_start_creating(name, parent);
618 struct inode *inode;
619
620 if (IS_ERR(dentry))
621 return dentry;
622
623 inode = debugfs_get_inode(dentry->d_sb);
624 if (unlikely(!inode)) {
625 pr_err("out of free dentries, can not create automount '%s'\n",
626 name);
627 return debugfs_failed_creating(dentry);
628 }
629
630 make_empty_dir_inode(inode);
631 inode->i_flags |= S_AUTOMOUNT;
632 inode->i_private = data;
633 DEBUGFS_I(inode)->automount = f;
634 /* directory inodes start off with i_nlink == 2 (for "." entry) */
635 inc_nlink(inode);
636 d_make_persistent(dentry, inode);
637 inc_nlink(d_inode(dentry->d_parent));
638 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
639 return debugfs_end_creating(dentry);
640}
641EXPORT_SYMBOL(debugfs_create_automount);
642
643/**
644 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
645 * @name: a pointer to a string containing the name of the symbolic link to
646 * create.
647 * @parent: a pointer to the parent dentry for this symbolic link. This
648 * should be a directory dentry if set. If this parameter is NULL,
649 * then the symbolic link will be created in the root of the debugfs
650 * filesystem.
651 * @target: a pointer to a string containing the path to the target of the
652 * symbolic link.
653 *
654 * This function creates a symbolic link with the given name in debugfs that
655 * links to the given target path.
656 *
657 * This function will return a pointer to a dentry if it succeeds. This
658 * pointer must be passed to the debugfs_remove() function when the symbolic
659 * link is to be removed (no automatic cleanup happens if your module is
660 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
661 * will be returned.
662 *
663 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
664 * returned.
665 */
666struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
667 const char *target)
668{
669 struct dentry *dentry;
670 struct inode *inode;
671 char *link = kstrdup(target, GFP_KERNEL);
672 if (!link)
673 return ERR_PTR(-ENOMEM);
674
675 dentry = debugfs_start_creating(name, parent);
676 if (IS_ERR(dentry)) {
677 kfree(link);
678 return dentry;
679 }
680
681 inode = debugfs_get_inode(dentry->d_sb);
682 if (unlikely(!inode)) {
683 pr_err("out of free dentries, can not create symlink '%s'\n",
684 name);
685 kfree(link);
686 return debugfs_failed_creating(dentry);
687 }
688 inode->i_mode = S_IFLNK | S_IRWXUGO;
689 inode->i_op = &debugfs_symlink_inode_operations;
690 inode->i_link = link;
691 d_make_persistent(dentry, inode);
692 return debugfs_end_creating(dentry);
693}
694EXPORT_SYMBOL_GPL(debugfs_create_symlink);
695
696static void __debugfs_file_removed(struct dentry *dentry)
697{
698 struct debugfs_fsdata *fsd;
699
700 /*
701 * Paired with the closing smp_mb() implied by a successful
702 * cmpxchg() in debugfs_file_get(): either
703 * debugfs_file_get() must see a dead dentry or we must see a
704 * debugfs_fsdata instance at ->d_fsdata here (or both).
705 */
706 smp_mb();
707 fsd = READ_ONCE(dentry->d_fsdata);
708 if (!fsd)
709 return;
710
711 /* if this was the last reference, we're done */
712 if (refcount_dec_and_test(&fsd->active_users))
713 return;
714
715 /*
716 * If there's still a reference, the code that obtained it can
717 * be in different states:
718 * - The common case of not using cancellations, or already
719 * after debugfs_leave_cancellation(), where we just need
720 * to wait for debugfs_file_put() which signals the completion;
721 * - inside a cancellation section, i.e. between
722 * debugfs_enter_cancellation() and debugfs_leave_cancellation(),
723 * in which case we need to trigger the ->cancel() function,
724 * and then wait for debugfs_file_put() just like in the
725 * previous case;
726 * - before debugfs_enter_cancellation() (but obviously after
727 * debugfs_file_get()), in which case we may not see the
728 * cancellation in the list on the first round of the loop,
729 * but debugfs_enter_cancellation() signals the completion
730 * after adding it, so this code gets woken up to call the
731 * ->cancel() function.
732 */
733 while (refcount_read(&fsd->active_users)) {
734 struct debugfs_cancellation *c;
735
736 /*
737 * Lock the cancellations. Note that the cancellations
738 * structs are meant to be on the stack, so we need to
739 * ensure we either use them here or don't touch them,
740 * and debugfs_leave_cancellation() will wait for this
741 * to be finished processing before exiting one. It may
742 * of course win and remove the cancellation, but then
743 * chances are we never even got into this bit, we only
744 * do if the refcount isn't zero already.
745 */
746 mutex_lock(&fsd->cancellations_mtx);
747 while ((c = list_first_entry_or_null(&fsd->cancellations,
748 typeof(*c), list))) {
749 list_del_init(&c->list);
750 c->cancel(dentry, c->cancel_data);
751 }
752 mutex_unlock(&fsd->cancellations_mtx);
753
754 wait_for_completion(&fsd->active_users_drained);
755 }
756}
757
758static void remove_one(struct dentry *victim)
759{
760 if (d_is_reg(victim))
761 __debugfs_file_removed(victim);
762 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
763}
764
765/**
766 * debugfs_remove - recursively removes a directory
767 * @dentry: a pointer to a the dentry of the directory to be removed. If this
768 * parameter is NULL or an error value, nothing will be done.
769 *
770 * This function recursively removes a directory tree in debugfs that
771 * was previously created with a call to another debugfs function
772 * (like debugfs_create_file() or variants thereof.)
773 *
774 * This function is required to be called in order for the file to be
775 * removed, no automatic cleanup of files will happen when a module is
776 * removed, you are responsible here.
777 */
778void debugfs_remove(struct dentry *dentry)
779{
780 if (IS_ERR_OR_NULL(dentry))
781 return;
782
783 simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
784 simple_recursive_removal(dentry, remove_one);
785 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
786}
787EXPORT_SYMBOL_GPL(debugfs_remove);
788
789/**
790 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
791 * @name: a pointer to a string containing the name of the item to look up.
792 * @parent: a pointer to the parent dentry of the item.
793 *
794 * This is the equlivant of doing something like
795 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
796 * handled for the directory being looked up.
797 */
798void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
799{
800 struct dentry *dentry;
801
802 dentry = debugfs_lookup(name, parent);
803 if (!dentry)
804 return;
805
806 debugfs_remove(dentry);
807 dput(dentry);
808}
809EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
810
811/**
812 * debugfs_change_name - rename a file/directory in the debugfs filesystem
813 * @dentry: dentry of an object to be renamed.
814 * @fmt: format for new name
815 *
816 * This function renames a file/directory in debugfs. The target must not
817 * exist for rename to succeed.
818 *
819 * This function will return 0 on success and -E... on failure.
820 *
821 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
822 * returned.
823 */
824int __printf(2, 3) debugfs_change_name(struct dentry *dentry, const char *fmt, ...)
825{
826 int error = 0;
827 const char *new_name;
828 struct name_snapshot old_name;
829 struct dentry *target;
830 struct renamedata rd = {};
831 struct inode *dir;
832 va_list ap;
833
834 if (IS_ERR_OR_NULL(dentry))
835 return 0;
836
837 va_start(ap, fmt);
838 new_name = kvasprintf_const(GFP_KERNEL, fmt, ap);
839 va_end(ap);
840 if (!new_name)
841 return -ENOMEM;
842
843 rd.old_parent = dget_parent(dentry);
844 rd.new_parent = rd.old_parent;
845 rd.flags = RENAME_NOREPLACE;
846 target = lookup_noperm_unlocked(&QSTR(new_name), rd.new_parent);
847 if (IS_ERR(target)) {
848 error = PTR_ERR(target);
849 goto out_free;
850 }
851
852 error = start_renaming_two_dentries(&rd, dentry, target);
853 if (error) {
854 if (error == -EEXIST && target == dentry)
855 /* it isn't an error to rename a thing to itself */
856 error = 0;
857 goto out;
858 }
859
860 dir = d_inode(rd.old_parent);
861 take_dentry_name_snapshot(&old_name, dentry);
862 simple_rename_timestamp(dir, dentry, dir, rd.new_dentry);
863 d_move(dentry, rd.new_dentry);
864 fsnotify_move(dir, dir, &old_name.name, d_is_dir(dentry), NULL, dentry);
865 release_dentry_name_snapshot(&old_name);
866 end_renaming(&rd);
867out:
868 dput(rd.old_parent);
869 dput(target);
870out_free:
871 kfree_const(new_name);
872 return error;
873}
874EXPORT_SYMBOL_GPL(debugfs_change_name);
875
876/**
877 * debugfs_initialized - Tells whether debugfs has been registered
878 */
879bool debugfs_initialized(void)
880{
881 return debugfs_registered;
882}
883EXPORT_SYMBOL_GPL(debugfs_initialized);
884
885static int __init debugfs_kernel(char *str)
886{
887 if (str) {
888 if (!strcmp(str, "on"))
889 debugfs_enabled = true;
890 else if (!strcmp(str, "off"))
891 debugfs_enabled = false;
892 else if (!strcmp(str, "no-mount")) {
893 pr_notice("debugfs=no-mount is a deprecated alias "
894 "for debugfs=off\n");
895 debugfs_enabled = false;
896 }
897 }
898
899 return 0;
900}
901early_param("debugfs", debugfs_kernel);
902
903static int __init debugfs_init(void)
904{
905 int retval;
906
907 if (!debugfs_enabled)
908 return -EPERM;
909
910 retval = sysfs_create_mount_point(kernel_kobj, "debug");
911 if (retval)
912 return retval;
913
914 debugfs_inode_cachep = kmem_cache_create("debugfs_inode_cache",
915 sizeof(struct debugfs_inode_info), 0,
916 SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
917 init_once);
918 if (debugfs_inode_cachep == NULL) {
919 sysfs_remove_mount_point(kernel_kobj, "debug");
920 return -ENOMEM;
921 }
922
923 retval = register_filesystem(&debug_fs_type);
924 if (retval) { // Really not going to happen
925 sysfs_remove_mount_point(kernel_kobj, "debug");
926 kmem_cache_destroy(debugfs_inode_cachep);
927 return retval;
928 }
929 debugfs_registered = true;
930 return 0;
931}
932core_initcall(debugfs_init);