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
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 */
debugfs_setattr(struct user_namespace * mnt_userns,struct dentry * dentry,struct iattr * ia)45 static int debugfs_setattr(struct user_namespace *mnt_userns,
46 struct dentry *dentry, struct iattr *ia)
47 {
48 int ret = security_locked_down(LOCKDOWN_DEBUGFS);
49
50 if (ret && (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
51 return ret;
52 return simple_setattr(&init_user_ns, dentry, ia);
53 }
54
55 static const struct inode_operations debugfs_file_inode_operations = {
56 .setattr = debugfs_setattr,
57 };
58 static const struct inode_operations debugfs_dir_inode_operations = {
59 .lookup = simple_lookup,
60 .setattr = debugfs_setattr,
61 };
62 static const struct inode_operations debugfs_symlink_inode_operations = {
63 .get_link = simple_get_link,
64 .setattr = debugfs_setattr,
65 };
66
debugfs_get_inode(struct super_block * sb)67 static struct inode *debugfs_get_inode(struct super_block *sb)
68 {
69 struct inode *inode = new_inode(sb);
70 if (inode) {
71 inode->i_ino = get_next_ino();
72 inode->i_atime = inode->i_mtime =
73 inode->i_ctime = current_time(inode);
74 }
75 return inode;
76 }
77
78 struct debugfs_mount_opts {
79 kuid_t uid;
80 kgid_t gid;
81 umode_t mode;
82 };
83
84 enum {
85 Opt_uid,
86 Opt_gid,
87 Opt_mode,
88 Opt_err
89 };
90
91 static const match_table_t tokens = {
92 {Opt_uid, "uid=%u"},
93 {Opt_gid, "gid=%u"},
94 {Opt_mode, "mode=%o"},
95 {Opt_err, NULL}
96 };
97
98 struct debugfs_fs_info {
99 struct debugfs_mount_opts mount_opts;
100 };
101
debugfs_parse_options(char * data,struct debugfs_mount_opts * opts)102 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
103 {
104 substring_t args[MAX_OPT_ARGS];
105 int option;
106 int token;
107 kuid_t uid;
108 kgid_t gid;
109 char *p;
110
111 opts->mode = DEBUGFS_DEFAULT_MODE;
112
113 while ((p = strsep(&data, ",")) != NULL) {
114 if (!*p)
115 continue;
116
117 token = match_token(p, tokens, args);
118 switch (token) {
119 case Opt_uid:
120 if (match_int(&args[0], &option))
121 return -EINVAL;
122 uid = make_kuid(current_user_ns(), option);
123 if (!uid_valid(uid))
124 return -EINVAL;
125 opts->uid = uid;
126 break;
127 case Opt_gid:
128 if (match_int(&args[0], &option))
129 return -EINVAL;
130 gid = make_kgid(current_user_ns(), option);
131 if (!gid_valid(gid))
132 return -EINVAL;
133 opts->gid = gid;
134 break;
135 case Opt_mode:
136 if (match_octal(&args[0], &option))
137 return -EINVAL;
138 opts->mode = option & S_IALLUGO;
139 break;
140 /*
141 * We might like to report bad mount options here;
142 * but traditionally debugfs has ignored all mount options
143 */
144 }
145 }
146
147 return 0;
148 }
149
debugfs_apply_options(struct super_block * sb)150 static int debugfs_apply_options(struct super_block *sb)
151 {
152 struct debugfs_fs_info *fsi = sb->s_fs_info;
153 struct inode *inode = d_inode(sb->s_root);
154 struct debugfs_mount_opts *opts = &fsi->mount_opts;
155
156 inode->i_mode &= ~S_IALLUGO;
157 inode->i_mode |= opts->mode;
158
159 inode->i_uid = opts->uid;
160 inode->i_gid = opts->gid;
161
162 return 0;
163 }
164
debugfs_remount(struct super_block * sb,int * flags,char * data)165 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
166 {
167 int err;
168 struct debugfs_fs_info *fsi = sb->s_fs_info;
169
170 sync_filesystem(sb);
171 err = debugfs_parse_options(data, &fsi->mount_opts);
172 if (err)
173 goto fail;
174
175 debugfs_apply_options(sb);
176
177 fail:
178 return err;
179 }
180
debugfs_show_options(struct seq_file * m,struct dentry * root)181 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
182 {
183 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
184 struct debugfs_mount_opts *opts = &fsi->mount_opts;
185
186 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
187 seq_printf(m, ",uid=%u",
188 from_kuid_munged(&init_user_ns, opts->uid));
189 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
190 seq_printf(m, ",gid=%u",
191 from_kgid_munged(&init_user_ns, opts->gid));
192 if (opts->mode != DEBUGFS_DEFAULT_MODE)
193 seq_printf(m, ",mode=%o", opts->mode);
194
195 return 0;
196 }
197
debugfs_free_inode(struct inode * inode)198 static void debugfs_free_inode(struct inode *inode)
199 {
200 if (S_ISLNK(inode->i_mode))
201 kfree(inode->i_link);
202 free_inode_nonrcu(inode);
203 }
204
205 static const struct super_operations debugfs_super_operations = {
206 .statfs = simple_statfs,
207 .remount_fs = debugfs_remount,
208 .show_options = debugfs_show_options,
209 .free_inode = debugfs_free_inode,
210 };
211
debugfs_release_dentry(struct dentry * dentry)212 static void debugfs_release_dentry(struct dentry *dentry)
213 {
214 void *fsd = dentry->d_fsdata;
215
216 if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
217 kfree(dentry->d_fsdata);
218 }
219
debugfs_automount(struct path * path)220 static struct vfsmount *debugfs_automount(struct path *path)
221 {
222 debugfs_automount_t f;
223 f = (debugfs_automount_t)path->dentry->d_fsdata;
224 return f(path->dentry, d_inode(path->dentry)->i_private);
225 }
226
227 static const struct dentry_operations debugfs_dops = {
228 .d_delete = always_delete_dentry,
229 .d_release = debugfs_release_dentry,
230 .d_automount = debugfs_automount,
231 };
232
debug_fill_super(struct super_block * sb,void * data,int silent)233 static int debug_fill_super(struct super_block *sb, void *data, int silent)
234 {
235 static const struct tree_descr debug_files[] = {{""}};
236 struct debugfs_fs_info *fsi;
237 int err;
238
239 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
240 sb->s_fs_info = fsi;
241 if (!fsi) {
242 err = -ENOMEM;
243 goto fail;
244 }
245
246 err = debugfs_parse_options(data, &fsi->mount_opts);
247 if (err)
248 goto fail;
249
250 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
251 if (err)
252 goto fail;
253
254 sb->s_op = &debugfs_super_operations;
255 sb->s_d_op = &debugfs_dops;
256
257 debugfs_apply_options(sb);
258
259 return 0;
260
261 fail:
262 kfree(fsi);
263 sb->s_fs_info = NULL;
264 return err;
265 }
266
debug_mount(struct file_system_type * fs_type,int flags,const char * dev_name,void * data)267 static struct dentry *debug_mount(struct file_system_type *fs_type,
268 int flags, const char *dev_name,
269 void *data)
270 {
271 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
272 return ERR_PTR(-EPERM);
273
274 return mount_single(fs_type, flags, data, debug_fill_super);
275 }
276
277 static struct file_system_type debug_fs_type = {
278 .owner = THIS_MODULE,
279 .name = "debugfs",
280 .mount = debug_mount,
281 .kill_sb = kill_litter_super,
282 };
283 MODULE_ALIAS_FS("debugfs");
284
285 /**
286 * debugfs_lookup() - look up an existing debugfs file
287 * @name: a pointer to a string containing the name of the file to look up.
288 * @parent: a pointer to the parent dentry of the file.
289 *
290 * This function will return a pointer to a dentry if it succeeds. If the file
291 * doesn't exist or an error occurs, %NULL will be returned. The returned
292 * dentry must be passed to dput() when it is no longer needed.
293 *
294 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
295 * returned.
296 */
debugfs_lookup(const char * name,struct dentry * parent)297 struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
298 {
299 struct dentry *dentry;
300
301 if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
302 return NULL;
303
304 if (!parent)
305 parent = debugfs_mount->mnt_root;
306
307 dentry = lookup_positive_unlocked(name, parent, strlen(name));
308 if (IS_ERR(dentry))
309 return NULL;
310 return dentry;
311 }
312 EXPORT_SYMBOL_GPL(debugfs_lookup);
313
start_creating(const char * name,struct dentry * parent)314 static struct dentry *start_creating(const char *name, struct dentry *parent)
315 {
316 struct dentry *dentry;
317 int error;
318
319 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
320 return ERR_PTR(-EPERM);
321
322 if (!debugfs_initialized())
323 return ERR_PTR(-ENOENT);
324
325 pr_debug("creating file '%s'\n", name);
326
327 if (IS_ERR(parent))
328 return parent;
329
330 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
331 &debugfs_mount_count);
332 if (error) {
333 pr_err("Unable to pin filesystem for file '%s'\n", name);
334 return ERR_PTR(error);
335 }
336
337 /* If the parent is not specified, we create it in the root.
338 * We need the root dentry to do this, which is in the super
339 * block. A pointer to that is in the struct vfsmount that we
340 * have around.
341 */
342 if (!parent)
343 parent = debugfs_mount->mnt_root;
344
345 inode_lock(d_inode(parent));
346 if (unlikely(IS_DEADDIR(d_inode(parent))))
347 dentry = ERR_PTR(-ENOENT);
348 else
349 dentry = lookup_one_len(name, parent, strlen(name));
350 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
351 if (d_is_dir(dentry))
352 pr_err("Directory '%s' with parent '%s' already present!\n",
353 name, parent->d_name.name);
354 else
355 pr_err("File '%s' in directory '%s' already present!\n",
356 name, parent->d_name.name);
357 dput(dentry);
358 dentry = ERR_PTR(-EEXIST);
359 }
360
361 if (IS_ERR(dentry)) {
362 inode_unlock(d_inode(parent));
363 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
364 }
365
366 return dentry;
367 }
368
failed_creating(struct dentry * dentry)369 static struct dentry *failed_creating(struct dentry *dentry)
370 {
371 inode_unlock(d_inode(dentry->d_parent));
372 dput(dentry);
373 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
374 return ERR_PTR(-ENOMEM);
375 }
376
end_creating(struct dentry * dentry)377 static struct dentry *end_creating(struct dentry *dentry)
378 {
379 inode_unlock(d_inode(dentry->d_parent));
380 return dentry;
381 }
382
__debugfs_create_file(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * proxy_fops,const struct file_operations * real_fops)383 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
384 struct dentry *parent, void *data,
385 const struct file_operations *proxy_fops,
386 const struct file_operations *real_fops)
387 {
388 struct dentry *dentry;
389 struct inode *inode;
390
391 if (!(mode & S_IFMT))
392 mode |= S_IFREG;
393 BUG_ON(!S_ISREG(mode));
394 dentry = start_creating(name, parent);
395
396 if (IS_ERR(dentry))
397 return dentry;
398
399 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
400 failed_creating(dentry);
401 return ERR_PTR(-EPERM);
402 }
403
404 inode = debugfs_get_inode(dentry->d_sb);
405 if (unlikely(!inode)) {
406 pr_err("out of free dentries, can not create file '%s'\n",
407 name);
408 return failed_creating(dentry);
409 }
410
411 inode->i_mode = mode;
412 inode->i_private = data;
413
414 inode->i_op = &debugfs_file_inode_operations;
415 inode->i_fop = proxy_fops;
416 dentry->d_fsdata = (void *)((unsigned long)real_fops |
417 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
418
419 d_instantiate(dentry, inode);
420 fsnotify_create(d_inode(dentry->d_parent), dentry);
421 return end_creating(dentry);
422 }
423
424 /**
425 * debugfs_create_file - create a file in the debugfs filesystem
426 * @name: a pointer to a string containing the name of the file to create.
427 * @mode: the permission that the file should have.
428 * @parent: a pointer to the parent dentry for this file. This should be a
429 * directory dentry if set. If this parameter is NULL, then the
430 * file will be created in the root of the debugfs filesystem.
431 * @data: a pointer to something that the caller will want to get to later
432 * on. The inode.i_private pointer will point to this value on
433 * the open() call.
434 * @fops: a pointer to a struct file_operations that should be used for
435 * this file.
436 *
437 * This is the basic "create a file" function for debugfs. It allows for a
438 * wide range of flexibility in creating a file, or a directory (if you want
439 * to create a directory, the debugfs_create_dir() function is
440 * recommended to be used instead.)
441 *
442 * This function will return a pointer to a dentry if it succeeds. This
443 * pointer must be passed to the debugfs_remove() function when the file is
444 * to be removed (no automatic cleanup happens if your module is unloaded,
445 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
446 * returned.
447 *
448 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
449 * returned.
450 */
debugfs_create_file(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * fops)451 struct dentry *debugfs_create_file(const char *name, umode_t mode,
452 struct dentry *parent, void *data,
453 const struct file_operations *fops)
454 {
455
456 return __debugfs_create_file(name, mode, parent, data,
457 fops ? &debugfs_full_proxy_file_operations :
458 &debugfs_noop_file_operations,
459 fops);
460 }
461 EXPORT_SYMBOL_GPL(debugfs_create_file);
462
463 /**
464 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
465 * @name: a pointer to a string containing the name of the file to create.
466 * @mode: the permission that the file should have.
467 * @parent: a pointer to the parent dentry for this file. This should be a
468 * directory dentry if set. If this parameter is NULL, then the
469 * file will be created in the root of the debugfs filesystem.
470 * @data: a pointer to something that the caller will want to get to later
471 * on. The inode.i_private pointer will point to this value on
472 * the open() call.
473 * @fops: a pointer to a struct file_operations that should be used for
474 * this file.
475 *
476 * debugfs_create_file_unsafe() is completely analogous to
477 * debugfs_create_file(), the only difference being that the fops
478 * handed it will not get protected against file removals by the
479 * debugfs core.
480 *
481 * It is your responsibility to protect your struct file_operation
482 * methods against file removals by means of debugfs_file_get()
483 * and debugfs_file_put(). ->open() is still protected by
484 * debugfs though.
485 *
486 * Any struct file_operations defined by means of
487 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
488 * thus, may be used here.
489 */
debugfs_create_file_unsafe(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * fops)490 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
491 struct dentry *parent, void *data,
492 const struct file_operations *fops)
493 {
494
495 return __debugfs_create_file(name, mode, parent, data,
496 fops ? &debugfs_open_proxy_file_operations :
497 &debugfs_noop_file_operations,
498 fops);
499 }
500 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
501
502 /**
503 * debugfs_create_file_size - create a file in the debugfs filesystem
504 * @name: a pointer to a string containing the name of the file to create.
505 * @mode: the permission that the file should have.
506 * @parent: a pointer to the parent dentry for this file. This should be a
507 * directory dentry if set. If this parameter is NULL, then the
508 * file will be created in the root of the debugfs filesystem.
509 * @data: a pointer to something that the caller will want to get to later
510 * on. The inode.i_private pointer will point to this value on
511 * the open() call.
512 * @fops: a pointer to a struct file_operations that should be used for
513 * this file.
514 * @file_size: initial file size
515 *
516 * This is the basic "create a file" function for debugfs. It allows for a
517 * wide range of flexibility in creating a file, or a directory (if you want
518 * to create a directory, the debugfs_create_dir() function is
519 * recommended to be used instead.)
520 */
debugfs_create_file_size(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * fops,loff_t file_size)521 void debugfs_create_file_size(const char *name, umode_t mode,
522 struct dentry *parent, void *data,
523 const struct file_operations *fops,
524 loff_t file_size)
525 {
526 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
527
528 if (de)
529 d_inode(de)->i_size = file_size;
530 }
531 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
532
533 /**
534 * debugfs_create_dir - create a directory in the debugfs filesystem
535 * @name: a pointer to a string containing the name of the directory to
536 * create.
537 * @parent: a pointer to the parent dentry for this file. This should be a
538 * directory dentry if set. If this parameter is NULL, then the
539 * directory will be created in the root of the debugfs filesystem.
540 *
541 * This function creates a directory in debugfs with the given name.
542 *
543 * This function will return a pointer to a dentry if it succeeds. This
544 * pointer must be passed to the debugfs_remove() function when the file is
545 * to be removed (no automatic cleanup happens if your module is unloaded,
546 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
547 * returned.
548 *
549 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
550 * returned.
551 */
debugfs_create_dir(const char * name,struct dentry * parent)552 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
553 {
554 struct dentry *dentry = start_creating(name, parent);
555 struct inode *inode;
556
557 if (IS_ERR(dentry))
558 return dentry;
559
560 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
561 failed_creating(dentry);
562 return ERR_PTR(-EPERM);
563 }
564
565 inode = debugfs_get_inode(dentry->d_sb);
566 if (unlikely(!inode)) {
567 pr_err("out of free dentries, can not create directory '%s'\n",
568 name);
569 return failed_creating(dentry);
570 }
571
572 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
573 inode->i_op = &debugfs_dir_inode_operations;
574 inode->i_fop = &simple_dir_operations;
575
576 /* directory inodes start off with i_nlink == 2 (for "." entry) */
577 inc_nlink(inode);
578 d_instantiate(dentry, inode);
579 inc_nlink(d_inode(dentry->d_parent));
580 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
581 return end_creating(dentry);
582 }
583 EXPORT_SYMBOL_GPL(debugfs_create_dir);
584
585 /**
586 * debugfs_create_automount - create automount point in the debugfs filesystem
587 * @name: a pointer to a string containing the name of the file to create.
588 * @parent: a pointer to the parent dentry for this file. This should be a
589 * directory dentry if set. If this parameter is NULL, then the
590 * file will be created in the root of the debugfs filesystem.
591 * @f: function to be called when pathname resolution steps on that one.
592 * @data: opaque argument to pass to f().
593 *
594 * @f should return what ->d_automount() would.
595 */
debugfs_create_automount(const char * name,struct dentry * parent,debugfs_automount_t f,void * data)596 struct dentry *debugfs_create_automount(const char *name,
597 struct dentry *parent,
598 debugfs_automount_t f,
599 void *data)
600 {
601 struct dentry *dentry = start_creating(name, parent);
602 struct inode *inode;
603
604 if (IS_ERR(dentry))
605 return dentry;
606
607 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
608 failed_creating(dentry);
609 return ERR_PTR(-EPERM);
610 }
611
612 inode = debugfs_get_inode(dentry->d_sb);
613 if (unlikely(!inode)) {
614 pr_err("out of free dentries, can not create automount '%s'\n",
615 name);
616 return failed_creating(dentry);
617 }
618
619 make_empty_dir_inode(inode);
620 inode->i_flags |= S_AUTOMOUNT;
621 inode->i_private = data;
622 dentry->d_fsdata = (void *)f;
623 /* directory inodes start off with i_nlink == 2 (for "." entry) */
624 inc_nlink(inode);
625 d_instantiate(dentry, inode);
626 inc_nlink(d_inode(dentry->d_parent));
627 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
628 return end_creating(dentry);
629 }
630 EXPORT_SYMBOL(debugfs_create_automount);
631
632 /**
633 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
634 * @name: a pointer to a string containing the name of the symbolic link to
635 * create.
636 * @parent: a pointer to the parent dentry for this symbolic link. This
637 * should be a directory dentry if set. If this parameter is NULL,
638 * then the symbolic link will be created in the root of the debugfs
639 * filesystem.
640 * @target: a pointer to a string containing the path to the target of the
641 * symbolic link.
642 *
643 * This function creates a symbolic link with the given name in debugfs that
644 * links to the given target path.
645 *
646 * This function will return a pointer to a dentry if it succeeds. This
647 * pointer must be passed to the debugfs_remove() function when the symbolic
648 * link is to be removed (no automatic cleanup happens if your module is
649 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
650 * will be returned.
651 *
652 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
653 * returned.
654 */
debugfs_create_symlink(const char * name,struct dentry * parent,const char * target)655 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
656 const char *target)
657 {
658 struct dentry *dentry;
659 struct inode *inode;
660 char *link = kstrdup(target, GFP_KERNEL);
661 if (!link)
662 return ERR_PTR(-ENOMEM);
663
664 dentry = start_creating(name, parent);
665 if (IS_ERR(dentry)) {
666 kfree(link);
667 return dentry;
668 }
669
670 inode = debugfs_get_inode(dentry->d_sb);
671 if (unlikely(!inode)) {
672 pr_err("out of free dentries, can not create symlink '%s'\n",
673 name);
674 kfree(link);
675 return failed_creating(dentry);
676 }
677 inode->i_mode = S_IFLNK | S_IRWXUGO;
678 inode->i_op = &debugfs_symlink_inode_operations;
679 inode->i_link = link;
680 d_instantiate(dentry, inode);
681 return end_creating(dentry);
682 }
683 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
684
__debugfs_file_removed(struct dentry * dentry)685 static void __debugfs_file_removed(struct dentry *dentry)
686 {
687 struct debugfs_fsdata *fsd;
688
689 /*
690 * Paired with the closing smp_mb() implied by a successful
691 * cmpxchg() in debugfs_file_get(): either
692 * debugfs_file_get() must see a dead dentry or we must see a
693 * debugfs_fsdata instance at ->d_fsdata here (or both).
694 */
695 smp_mb();
696 fsd = READ_ONCE(dentry->d_fsdata);
697 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
698 return;
699 if (!refcount_dec_and_test(&fsd->active_users))
700 wait_for_completion(&fsd->active_users_drained);
701 }
702
remove_one(struct dentry * victim)703 static void remove_one(struct dentry *victim)
704 {
705 if (d_is_reg(victim))
706 __debugfs_file_removed(victim);
707 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
708 }
709
710 /**
711 * debugfs_remove - recursively removes a directory
712 * @dentry: a pointer to a the dentry of the directory to be removed. If this
713 * parameter is NULL or an error value, nothing will be done.
714 *
715 * This function recursively removes a directory tree in debugfs that
716 * was previously created with a call to another debugfs function
717 * (like debugfs_create_file() or variants thereof.)
718 *
719 * This function is required to be called in order for the file to be
720 * removed, no automatic cleanup of files will happen when a module is
721 * removed, you are responsible here.
722 */
debugfs_remove(struct dentry * dentry)723 void debugfs_remove(struct dentry *dentry)
724 {
725 if (IS_ERR_OR_NULL(dentry))
726 return;
727
728 simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
729 simple_recursive_removal(dentry, remove_one);
730 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
731 }
732 EXPORT_SYMBOL_GPL(debugfs_remove);
733
734 /**
735 * debugfs_rename - rename a file/directory in the debugfs filesystem
736 * @old_dir: a pointer to the parent dentry for the renamed object. This
737 * should be a directory dentry.
738 * @old_dentry: dentry of an object to be renamed.
739 * @new_dir: a pointer to the parent dentry where the object should be
740 * moved. This should be a directory dentry.
741 * @new_name: a pointer to a string containing the target name.
742 *
743 * This function renames a file/directory in debugfs. The target must not
744 * exist for rename to succeed.
745 *
746 * This function will return a pointer to old_dentry (which is updated to
747 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
748 * returned.
749 *
750 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
751 * returned.
752 */
debugfs_rename(struct dentry * old_dir,struct dentry * old_dentry,struct dentry * new_dir,const char * new_name)753 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
754 struct dentry *new_dir, const char *new_name)
755 {
756 int error;
757 struct dentry *dentry = NULL, *trap;
758 struct name_snapshot old_name;
759
760 if (IS_ERR(old_dir))
761 return old_dir;
762 if (IS_ERR(new_dir))
763 return new_dir;
764 if (IS_ERR_OR_NULL(old_dentry))
765 return old_dentry;
766
767 trap = lock_rename(new_dir, old_dir);
768 /* Source or destination directories don't exist? */
769 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
770 goto exit;
771 /* Source does not exist, cyclic rename, or mountpoint? */
772 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
773 d_mountpoint(old_dentry))
774 goto exit;
775 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
776 /* Lookup failed, cyclic rename or target exists? */
777 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
778 goto exit;
779
780 take_dentry_name_snapshot(&old_name, old_dentry);
781
782 error = simple_rename(&init_user_ns, d_inode(old_dir), old_dentry,
783 d_inode(new_dir), dentry, 0);
784 if (error) {
785 release_dentry_name_snapshot(&old_name);
786 goto exit;
787 }
788 d_move(old_dentry, dentry);
789 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
790 d_is_dir(old_dentry),
791 NULL, old_dentry);
792 release_dentry_name_snapshot(&old_name);
793 unlock_rename(new_dir, old_dir);
794 dput(dentry);
795 return old_dentry;
796 exit:
797 if (dentry && !IS_ERR(dentry))
798 dput(dentry);
799 unlock_rename(new_dir, old_dir);
800 if (IS_ERR(dentry))
801 return dentry;
802 return ERR_PTR(-EINVAL);
803 }
804 EXPORT_SYMBOL_GPL(debugfs_rename);
805
806 /**
807 * debugfs_initialized - Tells whether debugfs has been registered
808 */
debugfs_initialized(void)809 bool debugfs_initialized(void)
810 {
811 return debugfs_registered;
812 }
813 EXPORT_SYMBOL_GPL(debugfs_initialized);
814
debugfs_kernel(char * str)815 static int __init debugfs_kernel(char *str)
816 {
817 if (str) {
818 if (!strcmp(str, "on"))
819 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
820 else if (!strcmp(str, "no-mount"))
821 debugfs_allow = DEBUGFS_ALLOW_API;
822 else if (!strcmp(str, "off"))
823 debugfs_allow = 0;
824 }
825
826 return 0;
827 }
828 early_param("debugfs", debugfs_kernel);
debugfs_init(void)829 static int __init debugfs_init(void)
830 {
831 int retval;
832
833 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
834 return -EPERM;
835
836 retval = sysfs_create_mount_point(kernel_kobj, "debug");
837 if (retval)
838 return retval;
839
840 retval = register_filesystem(&debug_fs_type);
841 if (retval)
842 sysfs_remove_mount_point(kernel_kobj, "debug");
843 else
844 debugfs_registered = true;
845
846 return retval;
847 }
848 core_initcall(debugfs_init);
849