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
35 static struct vfsmount *debugfs_mount;
36 static int debugfs_mount_count;
37 static bool debugfs_registered;
38 static 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 */
45 static 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
58 static const struct inode_operations debugfs_file_inode_operations = {
59 .setattr = debugfs_setattr,
60 };
61 static const struct inode_operations debugfs_dir_inode_operations = {
62 .lookup = simple_lookup,
63 .setattr = debugfs_setattr,
64 };
65 static const struct inode_operations debugfs_symlink_inode_operations = {
66 .get_link = simple_get_link,
67 .setattr = debugfs_setattr,
68 };
69
70 static 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
80 struct debugfs_fs_info {
81 kuid_t uid;
82 kgid_t gid;
83 umode_t mode;
84 /* Opt_* bitfield. */
85 unsigned int opts;
86 };
87
88 enum {
89 Opt_uid,
90 Opt_gid,
91 Opt_mode,
92 Opt_source,
93 };
94
95 static 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
103 static 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
148 static 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
170 static void debugfs_apply_options(struct super_block *sb)
171 {
172 _debugfs_apply_options(sb, false);
173 }
174
175 static void debugfs_apply_options_remount(struct super_block *sb)
176 {
177 _debugfs_apply_options(sb, true);
178 }
179
180 static 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
195 static 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
211 static 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
218 static 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
224 static 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) {
233 WARN_ON(!list_empty(&fsd->cancellations));
234 mutex_destroy(&fsd->cancellations_mtx);
235 }
236
237 kfree(fsd);
238 }
239
240 static 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
247 static 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
253 static 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
270 static 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
278 static void debugfs_free_fc(struct fs_context *fc)
279 {
280 kfree(fc->s_fs_info);
281 }
282
283 static 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
290 static 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
305 static 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 };
312 MODULE_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 */
326 struct 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 }
341 EXPORT_SYMBOL_GPL(debugfs_lookup);
342
343 static 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
398 static 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
406 static struct dentry *end_creating(struct dentry *dentry)
407 {
408 inode_unlock(d_inode(dentry->d_parent));
409 return dentry;
410 }
411
412 static 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 struct file_operations *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
453 /**
454 * debugfs_create_file - create a file in the debugfs filesystem
455 * @name: a pointer to a string containing the name of the file to create.
456 * @mode: the permission that the file should have.
457 * @parent: a pointer to the parent dentry for this file. This should be a
458 * directory dentry if set. If this parameter is NULL, then the
459 * file will be created in the root of the debugfs filesystem.
460 * @data: a pointer to something that the caller will want to get to later
461 * on. The inode.i_private pointer will point to this value on
462 * the open() call.
463 * @fops: a pointer to a struct file_operations that should be used for
464 * this file.
465 *
466 * This is the basic "create a file" function for debugfs. It allows for a
467 * wide range of flexibility in creating a file, or a directory (if you want
468 * to create a directory, the debugfs_create_dir() function is
469 * recommended to be used instead.)
470 *
471 * This function will return a pointer to a dentry if it succeeds. This
472 * pointer must be passed to the debugfs_remove() function when the file is
473 * to be removed (no automatic cleanup happens if your module is unloaded,
474 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
475 * returned.
476 *
477 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
478 * returned.
479 *
480 * NOTE: it's expected that most callers should _ignore_ the errors returned
481 * by this function. Other debugfs functions handle the fact that the "dentry"
482 * passed to them could be an error and they don't crash in that case.
483 * Drivers should generally work fine even if debugfs fails to init anyway.
484 */
485 struct dentry *debugfs_create_file(const char *name, umode_t mode,
486 struct dentry *parent, void *data,
487 const struct file_operations *fops)
488 {
489
490 return __debugfs_create_file(name, mode, parent, data,
491 fops ? &debugfs_full_proxy_file_operations :
492 &debugfs_noop_file_operations,
493 fops);
494 }
495 EXPORT_SYMBOL_GPL(debugfs_create_file);
496
497 /**
498 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
499 * @name: a pointer to a string containing the name of the file to create.
500 * @mode: the permission that the file should have.
501 * @parent: a pointer to the parent dentry for this file. This should be a
502 * directory dentry if set. If this parameter is NULL, then the
503 * file will be created in the root of the debugfs filesystem.
504 * @data: a pointer to something that the caller will want to get to later
505 * on. The inode.i_private pointer will point to this value on
506 * the open() call.
507 * @fops: a pointer to a struct file_operations that should be used for
508 * this file.
509 *
510 * debugfs_create_file_unsafe() is completely analogous to
511 * debugfs_create_file(), the only difference being that the fops
512 * handed it will not get protected against file removals by the
513 * debugfs core.
514 *
515 * It is your responsibility to protect your struct file_operation
516 * methods against file removals by means of debugfs_file_get()
517 * and debugfs_file_put(). ->open() is still protected by
518 * debugfs though.
519 *
520 * Any struct file_operations defined by means of
521 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
522 * thus, may be used here.
523 */
524 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
525 struct dentry *parent, void *data,
526 const struct file_operations *fops)
527 {
528
529 return __debugfs_create_file(name, mode, parent, data,
530 fops ? &debugfs_open_proxy_file_operations :
531 &debugfs_noop_file_operations,
532 fops);
533 }
534 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
535
536 /**
537 * debugfs_create_file_size - create a file in the debugfs filesystem
538 * @name: a pointer to a string containing the name of the file to create.
539 * @mode: the permission that the file should have.
540 * @parent: a pointer to the parent dentry for this file. This should be a
541 * directory dentry if set. If this parameter is NULL, then the
542 * file will be created in the root of the debugfs filesystem.
543 * @data: a pointer to something that the caller will want to get to later
544 * on. The inode.i_private pointer will point to this value on
545 * the open() call.
546 * @fops: a pointer to a struct file_operations that should be used for
547 * this file.
548 * @file_size: initial file size
549 *
550 * This is the basic "create a file" function for debugfs. It allows for a
551 * wide range of flexibility in creating a file, or a directory (if you want
552 * to create a directory, the debugfs_create_dir() function is
553 * recommended to be used instead.)
554 */
555 void debugfs_create_file_size(const char *name, umode_t mode,
556 struct dentry *parent, void *data,
557 const struct file_operations *fops,
558 loff_t file_size)
559 {
560 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
561
562 if (!IS_ERR(de))
563 d_inode(de)->i_size = file_size;
564 }
565 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
566
567 /**
568 * debugfs_create_dir - create a directory in the debugfs filesystem
569 * @name: a pointer to a string containing the name of the directory to
570 * create.
571 * @parent: a pointer to the parent dentry for this file. This should be a
572 * directory dentry if set. If this parameter is NULL, then the
573 * directory will be created in the root of the debugfs filesystem.
574 *
575 * This function creates a directory in debugfs with the given name.
576 *
577 * This function will return a pointer to a dentry if it succeeds. This
578 * pointer must be passed to the debugfs_remove() function when the file is
579 * to be removed (no automatic cleanup happens if your module is unloaded,
580 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
581 * returned.
582 *
583 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
584 * returned.
585 *
586 * NOTE: it's expected that most callers should _ignore_ the errors returned
587 * by this function. Other debugfs functions handle the fact that the "dentry"
588 * passed to them could be an error and they don't crash in that case.
589 * Drivers should generally work fine even if debugfs fails to init anyway.
590 */
591 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
592 {
593 struct dentry *dentry = start_creating(name, parent);
594 struct inode *inode;
595
596 if (IS_ERR(dentry))
597 return dentry;
598
599 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
600 failed_creating(dentry);
601 return ERR_PTR(-EPERM);
602 }
603
604 inode = debugfs_get_inode(dentry->d_sb);
605 if (unlikely(!inode)) {
606 pr_err("out of free dentries, can not create directory '%s'\n",
607 name);
608 return failed_creating(dentry);
609 }
610
611 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
612 inode->i_op = &debugfs_dir_inode_operations;
613 inode->i_fop = &simple_dir_operations;
614
615 /* directory inodes start off with i_nlink == 2 (for "." entry) */
616 inc_nlink(inode);
617 d_instantiate(dentry, inode);
618 inc_nlink(d_inode(dentry->d_parent));
619 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
620 return end_creating(dentry);
621 }
622 EXPORT_SYMBOL_GPL(debugfs_create_dir);
623
624 /**
625 * debugfs_create_automount - create automount point in the debugfs filesystem
626 * @name: a pointer to a string containing the name of the file to create.
627 * @parent: a pointer to the parent dentry for this file. This should be a
628 * directory dentry if set. If this parameter is NULL, then the
629 * file will be created in the root of the debugfs filesystem.
630 * @f: function to be called when pathname resolution steps on that one.
631 * @data: opaque argument to pass to f().
632 *
633 * @f should return what ->d_automount() would.
634 */
635 struct dentry *debugfs_create_automount(const char *name,
636 struct dentry *parent,
637 debugfs_automount_t f,
638 void *data)
639 {
640 struct dentry *dentry = start_creating(name, parent);
641 struct debugfs_fsdata *fsd;
642 struct inode *inode;
643
644 if (IS_ERR(dentry))
645 return dentry;
646
647 fsd = kzalloc(sizeof(*fsd), GFP_KERNEL);
648 if (!fsd) {
649 failed_creating(dentry);
650 return ERR_PTR(-ENOMEM);
651 }
652
653 fsd->automount = f;
654
655 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
656 failed_creating(dentry);
657 kfree(fsd);
658 return ERR_PTR(-EPERM);
659 }
660
661 inode = debugfs_get_inode(dentry->d_sb);
662 if (unlikely(!inode)) {
663 pr_err("out of free dentries, can not create automount '%s'\n",
664 name);
665 kfree(fsd);
666 return failed_creating(dentry);
667 }
668
669 make_empty_dir_inode(inode);
670 inode->i_flags |= S_AUTOMOUNT;
671 inode->i_private = data;
672 dentry->d_fsdata = fsd;
673 /* directory inodes start off with i_nlink == 2 (for "." entry) */
674 inc_nlink(inode);
675 d_instantiate(dentry, inode);
676 inc_nlink(d_inode(dentry->d_parent));
677 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
678 return end_creating(dentry);
679 }
680 EXPORT_SYMBOL(debugfs_create_automount);
681
682 /**
683 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
684 * @name: a pointer to a string containing the name of the symbolic link to
685 * create.
686 * @parent: a pointer to the parent dentry for this symbolic link. This
687 * should be a directory dentry if set. If this parameter is NULL,
688 * then the symbolic link will be created in the root of the debugfs
689 * filesystem.
690 * @target: a pointer to a string containing the path to the target of the
691 * symbolic link.
692 *
693 * This function creates a symbolic link with the given name in debugfs that
694 * links to the given target path.
695 *
696 * This function will return a pointer to a dentry if it succeeds. This
697 * pointer must be passed to the debugfs_remove() function when the symbolic
698 * link is to be removed (no automatic cleanup happens if your module is
699 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
700 * will be returned.
701 *
702 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
703 * returned.
704 */
705 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
706 const char *target)
707 {
708 struct dentry *dentry;
709 struct inode *inode;
710 char *link = kstrdup(target, GFP_KERNEL);
711 if (!link)
712 return ERR_PTR(-ENOMEM);
713
714 dentry = start_creating(name, parent);
715 if (IS_ERR(dentry)) {
716 kfree(link);
717 return dentry;
718 }
719
720 inode = debugfs_get_inode(dentry->d_sb);
721 if (unlikely(!inode)) {
722 pr_err("out of free dentries, can not create symlink '%s'\n",
723 name);
724 kfree(link);
725 return failed_creating(dentry);
726 }
727 inode->i_mode = S_IFLNK | S_IRWXUGO;
728 inode->i_op = &debugfs_symlink_inode_operations;
729 inode->i_link = link;
730 d_instantiate(dentry, inode);
731 return end_creating(dentry);
732 }
733 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
734
735 static void __debugfs_file_removed(struct dentry *dentry)
736 {
737 struct debugfs_fsdata *fsd;
738
739 /*
740 * Paired with the closing smp_mb() implied by a successful
741 * cmpxchg() in debugfs_file_get(): either
742 * debugfs_file_get() must see a dead dentry or we must see a
743 * debugfs_fsdata instance at ->d_fsdata here (or both).
744 */
745 smp_mb();
746 fsd = READ_ONCE(dentry->d_fsdata);
747 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
748 return;
749
750 /* if this was the last reference, we're done */
751 if (refcount_dec_and_test(&fsd->active_users))
752 return;
753
754 /*
755 * If there's still a reference, the code that obtained it can
756 * be in different states:
757 * - The common case of not using cancellations, or already
758 * after debugfs_leave_cancellation(), where we just need
759 * to wait for debugfs_file_put() which signals the completion;
760 * - inside a cancellation section, i.e. between
761 * debugfs_enter_cancellation() and debugfs_leave_cancellation(),
762 * in which case we need to trigger the ->cancel() function,
763 * and then wait for debugfs_file_put() just like in the
764 * previous case;
765 * - before debugfs_enter_cancellation() (but obviously after
766 * debugfs_file_get()), in which case we may not see the
767 * cancellation in the list on the first round of the loop,
768 * but debugfs_enter_cancellation() signals the completion
769 * after adding it, so this code gets woken up to call the
770 * ->cancel() function.
771 */
772 while (refcount_read(&fsd->active_users)) {
773 struct debugfs_cancellation *c;
774
775 /*
776 * Lock the cancellations. Note that the cancellations
777 * structs are meant to be on the stack, so we need to
778 * ensure we either use them here or don't touch them,
779 * and debugfs_leave_cancellation() will wait for this
780 * to be finished processing before exiting one. It may
781 * of course win and remove the cancellation, but then
782 * chances are we never even got into this bit, we only
783 * do if the refcount isn't zero already.
784 */
785 mutex_lock(&fsd->cancellations_mtx);
786 while ((c = list_first_entry_or_null(&fsd->cancellations,
787 typeof(*c), list))) {
788 list_del_init(&c->list);
789 c->cancel(dentry, c->cancel_data);
790 }
791 mutex_unlock(&fsd->cancellations_mtx);
792
793 wait_for_completion(&fsd->active_users_drained);
794 }
795 }
796
797 static void remove_one(struct dentry *victim)
798 {
799 if (d_is_reg(victim))
800 __debugfs_file_removed(victim);
801 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
802 }
803
804 /**
805 * debugfs_remove - recursively removes a directory
806 * @dentry: a pointer to a the dentry of the directory to be removed. If this
807 * parameter is NULL or an error value, nothing will be done.
808 *
809 * This function recursively removes a directory tree in debugfs that
810 * was previously created with a call to another debugfs function
811 * (like debugfs_create_file() or variants thereof.)
812 *
813 * This function is required to be called in order for the file to be
814 * removed, no automatic cleanup of files will happen when a module is
815 * removed, you are responsible here.
816 */
817 void debugfs_remove(struct dentry *dentry)
818 {
819 if (IS_ERR_OR_NULL(dentry))
820 return;
821
822 simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
823 simple_recursive_removal(dentry, remove_one);
824 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
825 }
826 EXPORT_SYMBOL_GPL(debugfs_remove);
827
828 /**
829 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
830 * @name: a pointer to a string containing the name of the item to look up.
831 * @parent: a pointer to the parent dentry of the item.
832 *
833 * This is the equlivant of doing something like
834 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
835 * handled for the directory being looked up.
836 */
837 void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
838 {
839 struct dentry *dentry;
840
841 dentry = debugfs_lookup(name, parent);
842 if (!dentry)
843 return;
844
845 debugfs_remove(dentry);
846 dput(dentry);
847 }
848 EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
849
850 /**
851 * debugfs_rename - rename a file/directory in the debugfs filesystem
852 * @old_dir: a pointer to the parent dentry for the renamed object. This
853 * should be a directory dentry.
854 * @old_dentry: dentry of an object to be renamed.
855 * @new_dir: a pointer to the parent dentry where the object should be
856 * moved. This should be a directory dentry.
857 * @new_name: a pointer to a string containing the target name.
858 *
859 * This function renames a file/directory in debugfs. The target must not
860 * exist for rename to succeed.
861 *
862 * This function will return a pointer to old_dentry (which is updated to
863 * reflect renaming) if it succeeds. If an error occurs, ERR_PTR(-ERROR)
864 * will be returned.
865 *
866 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
867 * returned.
868 */
869 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
870 struct dentry *new_dir, const char *new_name)
871 {
872 int error;
873 struct dentry *dentry = NULL, *trap;
874 struct name_snapshot old_name;
875
876 if (IS_ERR(old_dir))
877 return old_dir;
878 if (IS_ERR(new_dir))
879 return new_dir;
880 if (IS_ERR_OR_NULL(old_dentry))
881 return old_dentry;
882
883 trap = lock_rename(new_dir, old_dir);
884 /* Source or destination directories don't exist? */
885 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
886 goto exit;
887 /* Source does not exist, cyclic rename, or mountpoint? */
888 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
889 d_mountpoint(old_dentry))
890 goto exit;
891 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
892 /* Lookup failed, cyclic rename or target exists? */
893 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
894 goto exit;
895
896 take_dentry_name_snapshot(&old_name, old_dentry);
897
898 error = simple_rename(&nop_mnt_idmap, d_inode(old_dir), old_dentry,
899 d_inode(new_dir), dentry, 0);
900 if (error) {
901 release_dentry_name_snapshot(&old_name);
902 goto exit;
903 }
904 d_move(old_dentry, dentry);
905 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
906 d_is_dir(old_dentry),
907 NULL, old_dentry);
908 release_dentry_name_snapshot(&old_name);
909 unlock_rename(new_dir, old_dir);
910 dput(dentry);
911 return old_dentry;
912 exit:
913 if (dentry && !IS_ERR(dentry))
914 dput(dentry);
915 unlock_rename(new_dir, old_dir);
916 if (IS_ERR(dentry))
917 return dentry;
918 return ERR_PTR(-EINVAL);
919 }
920 EXPORT_SYMBOL_GPL(debugfs_rename);
921
922 /**
923 * debugfs_initialized - Tells whether debugfs has been registered
924 */
925 bool debugfs_initialized(void)
926 {
927 return debugfs_registered;
928 }
929 EXPORT_SYMBOL_GPL(debugfs_initialized);
930
931 static int __init debugfs_kernel(char *str)
932 {
933 if (str) {
934 if (!strcmp(str, "on"))
935 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
936 else if (!strcmp(str, "no-mount"))
937 debugfs_allow = DEBUGFS_ALLOW_API;
938 else if (!strcmp(str, "off"))
939 debugfs_allow = 0;
940 }
941
942 return 0;
943 }
944 early_param("debugfs", debugfs_kernel);
945 static int __init debugfs_init(void)
946 {
947 int retval;
948
949 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
950 return -EPERM;
951
952 retval = sysfs_create_mount_point(kernel_kobj, "debug");
953 if (retval)
954 return retval;
955
956 retval = register_filesystem(&debug_fs_type);
957 if (retval)
958 sysfs_remove_mount_point(kernel_kobj, "debug");
959 else
960 debugfs_registered = true;
961
962 return retval;
963 }
964 core_initcall(debugfs_init);
965
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