1// SPDX-License-Identifier: GPL-2.0
2/*
3 * inode.c - part of debugfs, a tiny little debug file system
4 *
5 * Copyright (C) 2004,2019 Greg Kroah-Hartman <greg@kroah.com>
6 * Copyright (C) 2004 IBM Inc.
7 * Copyright (C) 2019 Linux Foundation <gregkh@linuxfoundation.org>
8 *
9 * debugfs is for people to use instead of /proc or /sys.
10 * See ./Documentation/core-api/kernel-api.rst for more details.
11 */
12
13#define pr_fmt(fmt) "debugfs: " fmt
14
15#include <linux/module.h>
16#include <linux/fs.h>
17#include <linux/mount.h>
18#include <linux/pagemap.h>
19#include <linux/init.h>
20#include <linux/kobject.h>
21#include <linux/namei.h>
22#include <linux/debugfs.h>
23#include <linux/fsnotify.h>
24#include <linux/string.h>
25#include <linux/seq_file.h>
26#include <linux/parser.h>
27#include <linux/magic.h>
28#include <linux/slab.h>
29#include <linux/security.h>
30
31#include "internal.h"
32
33#define DEBUGFS_DEFAULT_MODE 0700
34
35static struct vfsmount *debugfs_mount;
36static int debugfs_mount_count;
37static bool debugfs_registered;
38static unsigned int debugfs_allow __ro_after_init = DEFAULT_DEBUGFS_ALLOW_BITS;
39
40/*
41 * Don't allow access attributes to be changed whilst the kernel is locked down
42 * so that we can use the file mode as part of a heuristic to determine whether
43 * to lock down individual files.
44 */
45static int debugfs_setattr(struct 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_mount_opts {
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_err
93};
94
95static const match_table_t tokens = {
96 {Opt_uid, "uid=%u"},
97 {Opt_gid, "gid=%u"},
98 {Opt_mode, "mode=%o"},
99 {Opt_err, NULL}
100};
101
102struct debugfs_fs_info {
103 struct debugfs_mount_opts mount_opts;
104};
105
106static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
107{
108 substring_t args[MAX_OPT_ARGS];
109 int option;
110 int token;
111 kuid_t uid;
112 kgid_t gid;
113 char *p;
114
115 opts->opts = 0;
116 opts->mode = DEBUGFS_DEFAULT_MODE;
117
118 while ((p = strsep(&data, ",")) != NULL) {
119 if (!*p)
120 continue;
121
122 token = match_token(p, table: tokens, args);
123 switch (token) {
124 case Opt_uid:
125 if (match_int(&args[0], result: &option))
126 return -EINVAL;
127 uid = make_kuid(current_user_ns(), uid: option);
128 if (!uid_valid(uid))
129 return -EINVAL;
130 opts->uid = uid;
131 break;
132 case Opt_gid:
133 if (match_int(&args[0], result: &option))
134 return -EINVAL;
135 gid = make_kgid(current_user_ns(), gid: option);
136 if (!gid_valid(gid))
137 return -EINVAL;
138 opts->gid = gid;
139 break;
140 case Opt_mode:
141 if (match_octal(&args[0], result: &option))
142 return -EINVAL;
143 opts->mode = option & S_IALLUGO;
144 break;
145 /*
146 * We might like to report bad mount options here;
147 * but traditionally debugfs has ignored all mount options
148 */
149 }
150
151 opts->opts |= BIT(token);
152 }
153
154 return 0;
155}
156
157static void _debugfs_apply_options(struct super_block *sb, bool remount)
158{
159 struct debugfs_fs_info *fsi = sb->s_fs_info;
160 struct inode *inode = d_inode(dentry: sb->s_root);
161 struct debugfs_mount_opts *opts = &fsi->mount_opts;
162
163 /*
164 * On remount, only reset mode/uid/gid if they were provided as mount
165 * options.
166 */
167
168 if (!remount || opts->opts & BIT(Opt_mode)) {
169 inode->i_mode &= ~S_IALLUGO;
170 inode->i_mode |= opts->mode;
171 }
172
173 if (!remount || opts->opts & BIT(Opt_uid))
174 inode->i_uid = opts->uid;
175
176 if (!remount || opts->opts & BIT(Opt_gid))
177 inode->i_gid = opts->gid;
178}
179
180static void debugfs_apply_options(struct super_block *sb)
181{
182 _debugfs_apply_options(sb, remount: false);
183}
184
185static void debugfs_apply_options_remount(struct super_block *sb)
186{
187 _debugfs_apply_options(sb, remount: true);
188}
189
190static int debugfs_remount(struct super_block *sb, int *flags, char *data)
191{
192 int err;
193 struct debugfs_fs_info *fsi = sb->s_fs_info;
194
195 sync_filesystem(sb);
196 err = debugfs_parse_options(data, opts: &fsi->mount_opts);
197 if (err)
198 goto fail;
199
200 debugfs_apply_options_remount(sb);
201
202fail:
203 return err;
204}
205
206static int debugfs_show_options(struct seq_file *m, struct dentry *root)
207{
208 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
209 struct debugfs_mount_opts *opts = &fsi->mount_opts;
210
211 if (!uid_eq(left: opts->uid, GLOBAL_ROOT_UID))
212 seq_printf(m, ",uid=%u",
213 from_kuid_munged(&init_user_ns, opts->uid));
214 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
215 seq_printf(m, ",gid=%u",
216 from_kgid_munged(&init_user_ns, opts->gid));
217 if (opts->mode != DEBUGFS_DEFAULT_MODE)
218 seq_printf(m, ",mode=%o", opts->mode);
219
220 return 0;
221}
222
223static void debugfs_free_inode(struct inode *inode)
224{
225 if (S_ISLNK(inode->i_mode))
226 kfree(objp: inode->i_link);
227 free_inode_nonrcu(inode);
228}
229
230static const struct super_operations debugfs_super_operations = {
231 .statfs = simple_statfs,
232 .remount_fs = debugfs_remount,
233 .show_options = debugfs_show_options,
234 .free_inode = debugfs_free_inode,
235};
236
237static void debugfs_release_dentry(struct dentry *dentry)
238{
239 struct debugfs_fsdata *fsd = dentry->d_fsdata;
240
241 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
242 return;
243
244 /* check it wasn't a dir (no fsdata) or automount (no real_fops) */
245 if (fsd && fsd->real_fops) {
246 WARN_ON(!list_empty(&fsd->cancellations));
247 mutex_destroy(lock: &fsd->cancellations_mtx);
248 }
249
250 kfree(objp: fsd);
251}
252
253static struct vfsmount *debugfs_automount(struct path *path)
254{
255 struct debugfs_fsdata *fsd = path->dentry->d_fsdata;
256
257 return fsd->automount(path->dentry, d_inode(dentry: path->dentry)->i_private);
258}
259
260static const struct dentry_operations debugfs_dops = {
261 .d_delete = always_delete_dentry,
262 .d_release = debugfs_release_dentry,
263 .d_automount = debugfs_automount,
264};
265
266static int debug_fill_super(struct super_block *sb, void *data, int silent)
267{
268 static const struct tree_descr debug_files[] = {{""}};
269 struct debugfs_fs_info *fsi;
270 int err;
271
272 fsi = kzalloc(size: sizeof(struct debugfs_fs_info), GFP_KERNEL);
273 sb->s_fs_info = fsi;
274 if (!fsi) {
275 err = -ENOMEM;
276 goto fail;
277 }
278
279 err = debugfs_parse_options(data, opts: &fsi->mount_opts);
280 if (err)
281 goto fail;
282
283 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
284 if (err)
285 goto fail;
286
287 sb->s_op = &debugfs_super_operations;
288 sb->s_d_op = &debugfs_dops;
289
290 debugfs_apply_options(sb);
291
292 return 0;
293
294fail:
295 kfree(objp: fsi);
296 sb->s_fs_info = NULL;
297 return err;
298}
299
300static struct dentry *debug_mount(struct file_system_type *fs_type,
301 int flags, const char *dev_name,
302 void *data)
303{
304 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
305 return ERR_PTR(error: -EPERM);
306
307 return mount_single(fs_type, flags, data, fill_super: debug_fill_super);
308}
309
310static struct file_system_type debug_fs_type = {
311 .owner = THIS_MODULE,
312 .name = "debugfs",
313 .mount = debug_mount,
314 .kill_sb = kill_litter_super,
315};
316MODULE_ALIAS_FS("debugfs");
317
318/**
319 * debugfs_lookup() - look up an existing debugfs file
320 * @name: a pointer to a string containing the name of the file to look up.
321 * @parent: a pointer to the parent dentry of the file.
322 *
323 * This function will return a pointer to a dentry if it succeeds. If the file
324 * doesn't exist or an error occurs, %NULL will be returned. The returned
325 * dentry must be passed to dput() when it is no longer needed.
326 *
327 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
328 * returned.
329 */
330struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
331{
332 struct dentry *dentry;
333
334 if (!debugfs_initialized() || IS_ERR_OR_NULL(ptr: name) || IS_ERR(ptr: parent))
335 return NULL;
336
337 if (!parent)
338 parent = debugfs_mount->mnt_root;
339
340 dentry = lookup_positive_unlocked(name, parent, strlen(name));
341 if (IS_ERR(ptr: dentry))
342 return NULL;
343 return dentry;
344}
345EXPORT_SYMBOL_GPL(debugfs_lookup);
346
347static struct dentry *start_creating(const char *name, struct dentry *parent)
348{
349 struct dentry *dentry;
350 int error;
351
352 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
353 return ERR_PTR(error: -EPERM);
354
355 if (!debugfs_initialized())
356 return ERR_PTR(error: -ENOENT);
357
358 pr_debug("creating file '%s'\n", name);
359
360 if (IS_ERR(ptr: parent))
361 return parent;
362
363 error = simple_pin_fs(&debug_fs_type, mount: &debugfs_mount,
364 count: &debugfs_mount_count);
365 if (error) {
366 pr_err("Unable to pin filesystem for file '%s'\n", name);
367 return ERR_PTR(error);
368 }
369
370 /* If the parent is not specified, we create it in the root.
371 * We need the root dentry to do this, which is in the super
372 * block. A pointer to that is in the struct vfsmount that we
373 * have around.
374 */
375 if (!parent)
376 parent = debugfs_mount->mnt_root;
377
378 inode_lock(inode: d_inode(dentry: parent));
379 if (unlikely(IS_DEADDIR(d_inode(parent))))
380 dentry = ERR_PTR(error: -ENOENT);
381 else
382 dentry = lookup_one_len(name, parent, strlen(name));
383 if (!IS_ERR(ptr: dentry) && d_really_is_positive(dentry)) {
384 if (d_is_dir(dentry))
385 pr_err("Directory '%s' with parent '%s' already present!\n",
386 name, parent->d_name.name);
387 else
388 pr_err("File '%s' in directory '%s' already present!\n",
389 name, parent->d_name.name);
390 dput(dentry);
391 dentry = ERR_PTR(error: -EEXIST);
392 }
393
394 if (IS_ERR(ptr: dentry)) {
395 inode_unlock(inode: d_inode(dentry: parent));
396 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
397 }
398
399 return dentry;
400}
401
402static struct dentry *failed_creating(struct dentry *dentry)
403{
404 inode_unlock(inode: d_inode(dentry: dentry->d_parent));
405 dput(dentry);
406 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
407 return ERR_PTR(error: -ENOMEM);
408}
409
410static struct dentry *end_creating(struct dentry *dentry)
411{
412 inode_unlock(inode: d_inode(dentry: dentry->d_parent));
413 return dentry;
414}
415
416static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
417 struct dentry *parent, void *data,
418 const struct file_operations *proxy_fops,
419 const struct file_operations *real_fops)
420{
421 struct dentry *dentry;
422 struct inode *inode;
423
424 if (!(mode & S_IFMT))
425 mode |= S_IFREG;
426 BUG_ON(!S_ISREG(mode));
427 dentry = start_creating(name, parent);
428
429 if (IS_ERR(ptr: dentry))
430 return dentry;
431
432 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
433 failed_creating(dentry);
434 return ERR_PTR(error: -EPERM);
435 }
436
437 inode = debugfs_get_inode(sb: dentry->d_sb);
438 if (unlikely(!inode)) {
439 pr_err("out of free dentries, can not create file '%s'\n",
440 name);
441 return failed_creating(dentry);
442 }
443
444 inode->i_mode = mode;
445 inode->i_private = data;
446
447 inode->i_op = &debugfs_file_inode_operations;
448 inode->i_fop = proxy_fops;
449 dentry->d_fsdata = (void *)((unsigned long)real_fops |
450 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
451
452 d_instantiate(dentry, inode);
453 fsnotify_create(dir: d_inode(dentry: dentry->d_parent), dentry);
454 return end_creating(dentry);
455}
456
457/**
458 * debugfs_create_file - create a file in the debugfs filesystem
459 * @name: a pointer to a string containing the name of the file to create.
460 * @mode: the permission that the file should have.
461 * @parent: a pointer to the parent dentry for this file. This should be a
462 * directory dentry if set. If this parameter is NULL, then the
463 * file will be created in the root of the debugfs filesystem.
464 * @data: a pointer to something that the caller will want to get to later
465 * on. The inode.i_private pointer will point to this value on
466 * the open() call.
467 * @fops: a pointer to a struct file_operations that should be used for
468 * this file.
469 *
470 * This is the basic "create a file" function for debugfs. It allows for a
471 * wide range of flexibility in creating a file, or a directory (if you want
472 * to create a directory, the debugfs_create_dir() function is
473 * recommended to be used instead.)
474 *
475 * This function will return a pointer to a dentry if it succeeds. This
476 * pointer must be passed to the debugfs_remove() function when the file is
477 * to be removed (no automatic cleanup happens if your module is unloaded,
478 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
479 * returned.
480 *
481 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
482 * returned.
483 *
484 * NOTE: it's expected that most callers should _ignore_ the errors returned
485 * by this function. Other debugfs functions handle the fact that the "dentry"
486 * passed to them could be an error and they don't crash in that case.
487 * Drivers should generally work fine even if debugfs fails to init anyway.
488 */
489struct dentry *debugfs_create_file(const char *name, umode_t mode,
490 struct dentry *parent, void *data,
491 const struct file_operations *fops)
492{
493
494 return __debugfs_create_file(name, mode, parent, data,
495 proxy_fops: fops ? &debugfs_full_proxy_file_operations :
496 &debugfs_noop_file_operations,
497 real_fops: fops);
498}
499EXPORT_SYMBOL_GPL(debugfs_create_file);
500
501/**
502 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
503 * @name: a pointer to a string containing the name of the file to create.
504 * @mode: the permission that the file should have.
505 * @parent: a pointer to the parent dentry for this file. This should be a
506 * directory dentry if set. If this parameter is NULL, then the
507 * file will be created in the root of the debugfs filesystem.
508 * @data: a pointer to something that the caller will want to get to later
509 * on. The inode.i_private pointer will point to this value on
510 * the open() call.
511 * @fops: a pointer to a struct file_operations that should be used for
512 * this file.
513 *
514 * debugfs_create_file_unsafe() is completely analogous to
515 * debugfs_create_file(), the only difference being that the fops
516 * handed it will not get protected against file removals by the
517 * debugfs core.
518 *
519 * It is your responsibility to protect your struct file_operation
520 * methods against file removals by means of debugfs_file_get()
521 * and debugfs_file_put(). ->open() is still protected by
522 * debugfs though.
523 *
524 * Any struct file_operations defined by means of
525 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
526 * thus, may be used here.
527 */
528struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
529 struct dentry *parent, void *data,
530 const struct file_operations *fops)
531{
532
533 return __debugfs_create_file(name, mode, parent, data,
534 proxy_fops: fops ? &debugfs_open_proxy_file_operations :
535 &debugfs_noop_file_operations,
536 real_fops: fops);
537}
538EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
539
540/**
541 * debugfs_create_file_size - create a file in the debugfs filesystem
542 * @name: a pointer to a string containing the name of the file to create.
543 * @mode: the permission that the file should have.
544 * @parent: a pointer to the parent dentry for this file. This should be a
545 * directory dentry if set. If this parameter is NULL, then the
546 * file will be created in the root of the debugfs filesystem.
547 * @data: a pointer to something that the caller will want to get to later
548 * on. The inode.i_private pointer will point to this value on
549 * the open() call.
550 * @fops: a pointer to a struct file_operations that should be used for
551 * this file.
552 * @file_size: initial file size
553 *
554 * This is the basic "create a file" function for debugfs. It allows for a
555 * wide range of flexibility in creating a file, or a directory (if you want
556 * to create a directory, the debugfs_create_dir() function is
557 * recommended to be used instead.)
558 */
559void debugfs_create_file_size(const char *name, umode_t mode,
560 struct dentry *parent, void *data,
561 const struct file_operations *fops,
562 loff_t file_size)
563{
564 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
565
566 if (!IS_ERR(ptr: de))
567 d_inode(dentry: de)->i_size = file_size;
568}
569EXPORT_SYMBOL_GPL(debugfs_create_file_size);
570
571/**
572 * debugfs_create_dir - create a directory in the debugfs filesystem
573 * @name: a pointer to a string containing the name of the directory to
574 * create.
575 * @parent: a pointer to the parent dentry for this file. This should be a
576 * directory dentry if set. If this parameter is NULL, then the
577 * directory will be created in the root of the debugfs filesystem.
578 *
579 * This function creates a directory in debugfs with the given name.
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 file is
583 * to be removed (no automatic cleanup happens if your module is unloaded,
584 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
585 * returned.
586 *
587 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
588 * returned.
589 *
590 * NOTE: it's expected that most callers should _ignore_ the errors returned
591 * by this function. Other debugfs functions handle the fact that the "dentry"
592 * passed to them could be an error and they don't crash in that case.
593 * Drivers should generally work fine even if debugfs fails to init anyway.
594 */
595struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
596{
597 struct dentry *dentry = start_creating(name, parent);
598 struct inode *inode;
599
600 if (IS_ERR(ptr: dentry))
601 return dentry;
602
603 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
604 failed_creating(dentry);
605 return ERR_PTR(error: -EPERM);
606 }
607
608 inode = debugfs_get_inode(sb: dentry->d_sb);
609 if (unlikely(!inode)) {
610 pr_err("out of free dentries, can not create directory '%s'\n",
611 name);
612 return failed_creating(dentry);
613 }
614
615 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
616 inode->i_op = &debugfs_dir_inode_operations;
617 inode->i_fop = &simple_dir_operations;
618
619 /* directory inodes start off with i_nlink == 2 (for "." entry) */
620 inc_nlink(inode);
621 d_instantiate(dentry, inode);
622 inc_nlink(inode: d_inode(dentry: dentry->d_parent));
623 fsnotify_mkdir(dir: d_inode(dentry: dentry->d_parent), dentry);
624 return end_creating(dentry);
625}
626EXPORT_SYMBOL_GPL(debugfs_create_dir);
627
628/**
629 * debugfs_create_automount - create automount point in the debugfs filesystem
630 * @name: a pointer to a string containing the name of the file to create.
631 * @parent: a pointer to the parent dentry for this file. This should be a
632 * directory dentry if set. If this parameter is NULL, then the
633 * file will be created in the root of the debugfs filesystem.
634 * @f: function to be called when pathname resolution steps on that one.
635 * @data: opaque argument to pass to f().
636 *
637 * @f should return what ->d_automount() would.
638 */
639struct dentry *debugfs_create_automount(const char *name,
640 struct dentry *parent,
641 debugfs_automount_t f,
642 void *data)
643{
644 struct dentry *dentry = start_creating(name, parent);
645 struct debugfs_fsdata *fsd;
646 struct inode *inode;
647
648 if (IS_ERR(ptr: dentry))
649 return dentry;
650
651 fsd = kzalloc(size: sizeof(*fsd), GFP_KERNEL);
652 if (!fsd) {
653 failed_creating(dentry);
654 return ERR_PTR(error: -ENOMEM);
655 }
656
657 fsd->automount = f;
658
659 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
660 failed_creating(dentry);
661 kfree(objp: fsd);
662 return ERR_PTR(error: -EPERM);
663 }
664
665 inode = debugfs_get_inode(sb: dentry->d_sb);
666 if (unlikely(!inode)) {
667 pr_err("out of free dentries, can not create automount '%s'\n",
668 name);
669 kfree(objp: fsd);
670 return failed_creating(dentry);
671 }
672
673 make_empty_dir_inode(inode);
674 inode->i_flags |= S_AUTOMOUNT;
675 inode->i_private = data;
676 dentry->d_fsdata = fsd;
677 /* directory inodes start off with i_nlink == 2 (for "." entry) */
678 inc_nlink(inode);
679 d_instantiate(dentry, inode);
680 inc_nlink(inode: d_inode(dentry: dentry->d_parent));
681 fsnotify_mkdir(dir: d_inode(dentry: dentry->d_parent), dentry);
682 return end_creating(dentry);
683}
684EXPORT_SYMBOL(debugfs_create_automount);
685
686/**
687 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
688 * @name: a pointer to a string containing the name of the symbolic link to
689 * create.
690 * @parent: a pointer to the parent dentry for this symbolic link. This
691 * should be a directory dentry if set. If this parameter is NULL,
692 * then the symbolic link will be created in the root of the debugfs
693 * filesystem.
694 * @target: a pointer to a string containing the path to the target of the
695 * symbolic link.
696 *
697 * This function creates a symbolic link with the given name in debugfs that
698 * links to the given target path.
699 *
700 * This function will return a pointer to a dentry if it succeeds. This
701 * pointer must be passed to the debugfs_remove() function when the symbolic
702 * link is to be removed (no automatic cleanup happens if your module is
703 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
704 * will be returned.
705 *
706 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
707 * returned.
708 */
709struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
710 const char *target)
711{
712 struct dentry *dentry;
713 struct inode *inode;
714 char *link = kstrdup(s: target, GFP_KERNEL);
715 if (!link)
716 return ERR_PTR(error: -ENOMEM);
717
718 dentry = start_creating(name, parent);
719 if (IS_ERR(ptr: dentry)) {
720 kfree(objp: link);
721 return dentry;
722 }
723
724 inode = debugfs_get_inode(sb: dentry->d_sb);
725 if (unlikely(!inode)) {
726 pr_err("out of free dentries, can not create symlink '%s'\n",
727 name);
728 kfree(objp: link);
729 return failed_creating(dentry);
730 }
731 inode->i_mode = S_IFLNK | S_IRWXUGO;
732 inode->i_op = &debugfs_symlink_inode_operations;
733 inode->i_link = link;
734 d_instantiate(dentry, inode);
735 return end_creating(dentry);
736}
737EXPORT_SYMBOL_GPL(debugfs_create_symlink);
738
739static void __debugfs_file_removed(struct dentry *dentry)
740{
741 struct debugfs_fsdata *fsd;
742
743 /*
744 * Paired with the closing smp_mb() implied by a successful
745 * cmpxchg() in debugfs_file_get(): either
746 * debugfs_file_get() must see a dead dentry or we must see a
747 * debugfs_fsdata instance at ->d_fsdata here (or both).
748 */
749 smp_mb();
750 fsd = READ_ONCE(dentry->d_fsdata);
751 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
752 return;
753
754 /* if this was the last reference, we're done */
755 if (refcount_dec_and_test(r: &fsd->active_users))
756 return;
757
758 /*
759 * If there's still a reference, the code that obtained it can
760 * be in different states:
761 * - The common case of not using cancellations, or already
762 * after debugfs_leave_cancellation(), where we just need
763 * to wait for debugfs_file_put() which signals the completion;
764 * - inside a cancellation section, i.e. between
765 * debugfs_enter_cancellation() and debugfs_leave_cancellation(),
766 * in which case we need to trigger the ->cancel() function,
767 * and then wait for debugfs_file_put() just like in the
768 * previous case;
769 * - before debugfs_enter_cancellation() (but obviously after
770 * debugfs_file_get()), in which case we may not see the
771 * cancellation in the list on the first round of the loop,
772 * but debugfs_enter_cancellation() signals the completion
773 * after adding it, so this code gets woken up to call the
774 * ->cancel() function.
775 */
776 while (refcount_read(r: &fsd->active_users)) {
777 struct debugfs_cancellation *c;
778
779 /*
780 * Lock the cancellations. Note that the cancellations
781 * structs are meant to be on the stack, so we need to
782 * ensure we either use them here or don't touch them,
783 * and debugfs_leave_cancellation() will wait for this
784 * to be finished processing before exiting one. It may
785 * of course win and remove the cancellation, but then
786 * chances are we never even got into this bit, we only
787 * do if the refcount isn't zero already.
788 */
789 mutex_lock(&fsd->cancellations_mtx);
790 while ((c = list_first_entry_or_null(&fsd->cancellations,
791 typeof(*c), list))) {
792 list_del_init(entry: &c->list);
793 c->cancel(dentry, c->cancel_data);
794 }
795 mutex_unlock(lock: &fsd->cancellations_mtx);
796
797 wait_for_completion(&fsd->active_users_drained);
798 }
799}
800
801static void remove_one(struct dentry *victim)
802{
803 if (d_is_reg(dentry: victim))
804 __debugfs_file_removed(dentry: victim);
805 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
806}
807
808/**
809 * debugfs_remove - recursively removes a directory
810 * @dentry: a pointer to a the dentry of the directory to be removed. If this
811 * parameter is NULL or an error value, nothing will be done.
812 *
813 * This function recursively removes a directory tree in debugfs that
814 * was previously created with a call to another debugfs function
815 * (like debugfs_create_file() or variants thereof.)
816 *
817 * This function is required to be called in order for the file to be
818 * removed, no automatic cleanup of files will happen when a module is
819 * removed, you are responsible here.
820 */
821void debugfs_remove(struct dentry *dentry)
822{
823 if (IS_ERR_OR_NULL(ptr: dentry))
824 return;
825
826 simple_pin_fs(&debug_fs_type, mount: &debugfs_mount, count: &debugfs_mount_count);
827 simple_recursive_removal(dentry, callback: remove_one);
828 simple_release_fs(mount: &debugfs_mount, count: &debugfs_mount_count);
829}
830EXPORT_SYMBOL_GPL(debugfs_remove);
831
832/**
833 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
834 * @name: a pointer to a string containing the name of the item to look up.
835 * @parent: a pointer to the parent dentry of the item.
836 *
837 * This is the equlivant of doing something like
838 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
839 * handled for the directory being looked up.
840 */
841void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
842{
843 struct dentry *dentry;
844
845 dentry = debugfs_lookup(name, parent);
846 if (!dentry)
847 return;
848
849 debugfs_remove(dentry);
850 dput(dentry);
851}
852EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
853
854/**
855 * debugfs_rename - rename a file/directory in the debugfs filesystem
856 * @old_dir: a pointer to the parent dentry for the renamed object. This
857 * should be a directory dentry.
858 * @old_dentry: dentry of an object to be renamed.
859 * @new_dir: a pointer to the parent dentry where the object should be
860 * moved. This should be a directory dentry.
861 * @new_name: a pointer to a string containing the target name.
862 *
863 * This function renames a file/directory in debugfs. The target must not
864 * exist for rename to succeed.
865 *
866 * This function will return a pointer to old_dentry (which is updated to
867 * reflect renaming) if it succeeds. If an error occurs, ERR_PTR(-ERROR)
868 * will be returned.
869 *
870 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
871 * returned.
872 */
873struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
874 struct dentry *new_dir, const char *new_name)
875{
876 int error;
877 struct dentry *dentry = NULL, *trap;
878 struct name_snapshot old_name;
879
880 if (IS_ERR(ptr: old_dir))
881 return old_dir;
882 if (IS_ERR(ptr: new_dir))
883 return new_dir;
884 if (IS_ERR_OR_NULL(ptr: old_dentry))
885 return old_dentry;
886
887 trap = lock_rename(new_dir, old_dir);
888 /* Source or destination directories don't exist? */
889 if (d_really_is_negative(dentry: old_dir) || d_really_is_negative(dentry: new_dir))
890 goto exit;
891 /* Source does not exist, cyclic rename, or mountpoint? */
892 if (d_really_is_negative(dentry: old_dentry) || old_dentry == trap ||
893 d_mountpoint(dentry: old_dentry))
894 goto exit;
895 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
896 /* Lookup failed, cyclic rename or target exists? */
897 if (IS_ERR(ptr: dentry) || dentry == trap || d_really_is_positive(dentry))
898 goto exit;
899
900 take_dentry_name_snapshot(&old_name, old_dentry);
901
902 error = simple_rename(&nop_mnt_idmap, d_inode(dentry: old_dir), old_dentry,
903 d_inode(dentry: new_dir), dentry, 0);
904 if (error) {
905 release_dentry_name_snapshot(&old_name);
906 goto exit;
907 }
908 d_move(old_dentry, dentry);
909 fsnotify_move(old_dir: d_inode(dentry: old_dir), new_dir: d_inode(dentry: new_dir), old_name: &old_name.name,
910 isdir: d_is_dir(dentry: old_dentry),
911 NULL, moved: old_dentry);
912 release_dentry_name_snapshot(&old_name);
913 unlock_rename(new_dir, old_dir);
914 dput(dentry);
915 return old_dentry;
916exit:
917 if (dentry && !IS_ERR(ptr: dentry))
918 dput(dentry);
919 unlock_rename(new_dir, old_dir);
920 if (IS_ERR(ptr: dentry))
921 return dentry;
922 return ERR_PTR(error: -EINVAL);
923}
924EXPORT_SYMBOL_GPL(debugfs_rename);
925
926/**
927 * debugfs_initialized - Tells whether debugfs has been registered
928 */
929bool debugfs_initialized(void)
930{
931 return debugfs_registered;
932}
933EXPORT_SYMBOL_GPL(debugfs_initialized);
934
935static int __init debugfs_kernel(char *str)
936{
937 if (str) {
938 if (!strcmp(str, "on"))
939 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
940 else if (!strcmp(str, "no-mount"))
941 debugfs_allow = DEBUGFS_ALLOW_API;
942 else if (!strcmp(str, "off"))
943 debugfs_allow = 0;
944 }
945
946 return 0;
947}
948early_param("debugfs", debugfs_kernel);
949static int __init debugfs_init(void)
950{
951 int retval;
952
953 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
954 return -EPERM;
955
956 retval = sysfs_create_mount_point(parent_kobj: kernel_kobj, name: "debug");
957 if (retval)
958 return retval;
959
960 retval = register_filesystem(&debug_fs_type);
961 if (retval)
962 sysfs_remove_mount_point(parent_kobj: kernel_kobj, name: "debug");
963 else
964 debugfs_registered = true;
965
966 return retval;
967}
968core_initcall(debugfs_init);
969

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