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 */
debugfs_setattr(struct mnt_idmap * idmap,struct dentry * dentry,struct iattr * ia)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
debugfs_get_inode(struct super_block * sb)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 };
93
94 static const struct fs_parameter_spec debugfs_param_specs[] = {
95 fsparam_u32 ("gid", Opt_gid),
96 fsparam_u32oct ("mode", Opt_mode),
97 fsparam_u32 ("uid", Opt_uid),
98 {}
99 };
100
debugfs_parse_param(struct fs_context * fc,struct fs_parameter * param)101 static int debugfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
102 {
103 struct debugfs_fs_info *opts = fc->s_fs_info;
104 struct fs_parse_result result;
105 kuid_t uid;
106 kgid_t gid;
107 int opt;
108
109 opt = fs_parse(fc, debugfs_param_specs, param, &result);
110 if (opt < 0)
111 return opt;
112
113 switch (opt) {
114 case Opt_uid:
115 uid = make_kuid(current_user_ns(), result.uint_32);
116 if (!uid_valid(uid))
117 return invalf(fc, "Unknown uid");
118 opts->uid = uid;
119 break;
120 case Opt_gid:
121 gid = make_kgid(current_user_ns(), result.uint_32);
122 if (!gid_valid(gid))
123 return invalf(fc, "Unknown gid");
124 opts->gid = gid;
125 break;
126 case Opt_mode:
127 opts->mode = result.uint_32 & S_IALLUGO;
128 break;
129 /*
130 * We might like to report bad mount options here;
131 * but traditionally debugfs has ignored all mount options
132 */
133 }
134
135 opts->opts |= BIT(opt);
136
137 return 0;
138 }
139
_debugfs_apply_options(struct super_block * sb,bool remount)140 static void _debugfs_apply_options(struct super_block *sb, bool remount)
141 {
142 struct debugfs_fs_info *fsi = sb->s_fs_info;
143 struct inode *inode = d_inode(sb->s_root);
144
145 /*
146 * On remount, only reset mode/uid/gid if they were provided as mount
147 * options.
148 */
149
150 if (!remount || fsi->opts & BIT(Opt_mode)) {
151 inode->i_mode &= ~S_IALLUGO;
152 inode->i_mode |= fsi->mode;
153 }
154
155 if (!remount || fsi->opts & BIT(Opt_uid))
156 inode->i_uid = fsi->uid;
157
158 if (!remount || fsi->opts & BIT(Opt_gid))
159 inode->i_gid = fsi->gid;
160 }
161
debugfs_apply_options(struct super_block * sb)162 static void debugfs_apply_options(struct super_block *sb)
163 {
164 _debugfs_apply_options(sb, false);
165 }
166
debugfs_apply_options_remount(struct super_block * sb)167 static void debugfs_apply_options_remount(struct super_block *sb)
168 {
169 _debugfs_apply_options(sb, true);
170 }
171
debugfs_reconfigure(struct fs_context * fc)172 static int debugfs_reconfigure(struct fs_context *fc)
173 {
174 struct super_block *sb = fc->root->d_sb;
175 struct debugfs_fs_info *sb_opts = sb->s_fs_info;
176 struct debugfs_fs_info *new_opts = fc->s_fs_info;
177
178 sync_filesystem(sb);
179
180 /* structure copy of new mount options to sb */
181 *sb_opts = *new_opts;
182 debugfs_apply_options_remount(sb);
183
184 return 0;
185 }
186
debugfs_show_options(struct seq_file * m,struct dentry * root)187 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
188 {
189 struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
190
191 if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID))
192 seq_printf(m, ",uid=%u",
193 from_kuid_munged(&init_user_ns, fsi->uid));
194 if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))
195 seq_printf(m, ",gid=%u",
196 from_kgid_munged(&init_user_ns, fsi->gid));
197 if (fsi->mode != DEBUGFS_DEFAULT_MODE)
198 seq_printf(m, ",mode=%o", fsi->mode);
199
200 return 0;
201 }
202
debugfs_free_inode(struct inode * inode)203 static void debugfs_free_inode(struct inode *inode)
204 {
205 if (S_ISLNK(inode->i_mode))
206 kfree(inode->i_link);
207 free_inode_nonrcu(inode);
208 }
209
210 static const struct super_operations debugfs_super_operations = {
211 .statfs = simple_statfs,
212 .show_options = debugfs_show_options,
213 .free_inode = debugfs_free_inode,
214 };
215
debugfs_release_dentry(struct dentry * dentry)216 static void debugfs_release_dentry(struct dentry *dentry)
217 {
218 struct debugfs_fsdata *fsd = dentry->d_fsdata;
219
220 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
221 return;
222
223 /* check it wasn't a dir (no fsdata) or automount (no real_fops) */
224 if (fsd && fsd->real_fops) {
225 WARN_ON(!list_empty(&fsd->cancellations));
226 mutex_destroy(&fsd->cancellations_mtx);
227 }
228
229 kfree(fsd);
230 }
231
debugfs_automount(struct path * path)232 static struct vfsmount *debugfs_automount(struct path *path)
233 {
234 struct debugfs_fsdata *fsd = path->dentry->d_fsdata;
235
236 return fsd->automount(path->dentry, d_inode(path->dentry)->i_private);
237 }
238
239 static const struct dentry_operations debugfs_dops = {
240 .d_delete = always_delete_dentry,
241 .d_release = debugfs_release_dentry,
242 .d_automount = debugfs_automount,
243 };
244
debugfs_fill_super(struct super_block * sb,struct fs_context * fc)245 static int debugfs_fill_super(struct super_block *sb, struct fs_context *fc)
246 {
247 static const struct tree_descr debug_files[] = {{""}};
248 int err;
249
250 err = simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
251 if (err)
252 return err;
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
debugfs_get_tree(struct fs_context * fc)262 static int debugfs_get_tree(struct fs_context *fc)
263 {
264 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
265 return -EPERM;
266
267 return get_tree_single(fc, debugfs_fill_super);
268 }
269
debugfs_free_fc(struct fs_context * fc)270 static void debugfs_free_fc(struct fs_context *fc)
271 {
272 kfree(fc->s_fs_info);
273 }
274
275 static const struct fs_context_operations debugfs_context_ops = {
276 .free = debugfs_free_fc,
277 .parse_param = debugfs_parse_param,
278 .get_tree = debugfs_get_tree,
279 .reconfigure = debugfs_reconfigure,
280 };
281
debugfs_init_fs_context(struct fs_context * fc)282 static int debugfs_init_fs_context(struct fs_context *fc)
283 {
284 struct debugfs_fs_info *fsi;
285
286 fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
287 if (!fsi)
288 return -ENOMEM;
289
290 fsi->mode = DEBUGFS_DEFAULT_MODE;
291
292 fc->s_fs_info = fsi;
293 fc->ops = &debugfs_context_ops;
294 return 0;
295 }
296
297 static struct file_system_type debug_fs_type = {
298 .owner = THIS_MODULE,
299 .name = "debugfs",
300 .init_fs_context = debugfs_init_fs_context,
301 .parameters = debugfs_param_specs,
302 .kill_sb = kill_litter_super,
303 };
304 MODULE_ALIAS_FS("debugfs");
305
306 /**
307 * debugfs_lookup() - look up an existing debugfs file
308 * @name: a pointer to a string containing the name of the file to look up.
309 * @parent: a pointer to the parent dentry of the file.
310 *
311 * This function will return a pointer to a dentry if it succeeds. If the file
312 * doesn't exist or an error occurs, %NULL will be returned. The returned
313 * dentry must be passed to dput() when it is no longer needed.
314 *
315 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
316 * returned.
317 */
debugfs_lookup(const char * name,struct dentry * parent)318 struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
319 {
320 struct dentry *dentry;
321
322 if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
323 return NULL;
324
325 if (!parent)
326 parent = debugfs_mount->mnt_root;
327
328 dentry = lookup_positive_unlocked(name, parent, strlen(name));
329 if (IS_ERR(dentry))
330 return NULL;
331 return dentry;
332 }
333 EXPORT_SYMBOL_GPL(debugfs_lookup);
334
start_creating(const char * name,struct dentry * parent)335 static struct dentry *start_creating(const char *name, struct dentry *parent)
336 {
337 struct dentry *dentry;
338 int error;
339
340 if (!(debugfs_allow & DEBUGFS_ALLOW_API))
341 return ERR_PTR(-EPERM);
342
343 if (!debugfs_initialized())
344 return ERR_PTR(-ENOENT);
345
346 pr_debug("creating file '%s'\n", name);
347
348 if (IS_ERR(parent))
349 return parent;
350
351 error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
352 &debugfs_mount_count);
353 if (error) {
354 pr_err("Unable to pin filesystem for file '%s'\n", name);
355 return ERR_PTR(error);
356 }
357
358 /* If the parent is not specified, we create it in the root.
359 * We need the root dentry to do this, which is in the super
360 * block. A pointer to that is in the struct vfsmount that we
361 * have around.
362 */
363 if (!parent)
364 parent = debugfs_mount->mnt_root;
365
366 inode_lock(d_inode(parent));
367 if (unlikely(IS_DEADDIR(d_inode(parent))))
368 dentry = ERR_PTR(-ENOENT);
369 else
370 dentry = lookup_one_len(name, parent, strlen(name));
371 if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
372 if (d_is_dir(dentry))
373 pr_err("Directory '%s' with parent '%s' already present!\n",
374 name, parent->d_name.name);
375 else
376 pr_err("File '%s' in directory '%s' already present!\n",
377 name, parent->d_name.name);
378 dput(dentry);
379 dentry = ERR_PTR(-EEXIST);
380 }
381
382 if (IS_ERR(dentry)) {
383 inode_unlock(d_inode(parent));
384 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
385 }
386
387 return dentry;
388 }
389
failed_creating(struct dentry * dentry)390 static struct dentry *failed_creating(struct dentry *dentry)
391 {
392 inode_unlock(d_inode(dentry->d_parent));
393 dput(dentry);
394 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
395 return ERR_PTR(-ENOMEM);
396 }
397
end_creating(struct dentry * dentry)398 static struct dentry *end_creating(struct dentry *dentry)
399 {
400 inode_unlock(d_inode(dentry->d_parent));
401 return dentry;
402 }
403
__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)404 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
405 struct dentry *parent, void *data,
406 const struct file_operations *proxy_fops,
407 const struct file_operations *real_fops)
408 {
409 struct dentry *dentry;
410 struct inode *inode;
411
412 if (!(mode & S_IFMT))
413 mode |= S_IFREG;
414 BUG_ON(!S_ISREG(mode));
415 dentry = start_creating(name, parent);
416
417 if (IS_ERR(dentry))
418 return dentry;
419
420 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
421 failed_creating(dentry);
422 return ERR_PTR(-EPERM);
423 }
424
425 inode = debugfs_get_inode(dentry->d_sb);
426 if (unlikely(!inode)) {
427 pr_err("out of free dentries, can not create file '%s'\n",
428 name);
429 return failed_creating(dentry);
430 }
431
432 inode->i_mode = mode;
433 inode->i_private = data;
434
435 inode->i_op = &debugfs_file_inode_operations;
436 inode->i_fop = proxy_fops;
437 dentry->d_fsdata = (void *)((unsigned long)real_fops |
438 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
439
440 d_instantiate(dentry, inode);
441 fsnotify_create(d_inode(dentry->d_parent), dentry);
442 return end_creating(dentry);
443 }
444
445 /**
446 * debugfs_create_file - create a file in the debugfs filesystem
447 * @name: a pointer to a string containing the name of the file to create.
448 * @mode: the permission that the file should have.
449 * @parent: a pointer to the parent dentry for this file. This should be a
450 * directory dentry if set. If this parameter is NULL, then the
451 * file will be created in the root of the debugfs filesystem.
452 * @data: a pointer to something that the caller will want to get to later
453 * on. The inode.i_private pointer will point to this value on
454 * the open() call.
455 * @fops: a pointer to a struct file_operations that should be used for
456 * this file.
457 *
458 * This is the basic "create a file" function for debugfs. It allows for a
459 * wide range of flexibility in creating a file, or a directory (if you want
460 * to create a directory, the debugfs_create_dir() function is
461 * recommended to be used instead.)
462 *
463 * This function will return a pointer to a dentry if it succeeds. This
464 * pointer must be passed to the debugfs_remove() function when the file is
465 * to be removed (no automatic cleanup happens if your module is unloaded,
466 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
467 * returned.
468 *
469 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
470 * returned.
471 *
472 * NOTE: it's expected that most callers should _ignore_ the errors returned
473 * by this function. Other debugfs functions handle the fact that the "dentry"
474 * passed to them could be an error and they don't crash in that case.
475 * Drivers should generally work fine even if debugfs fails to init anyway.
476 */
debugfs_create_file(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * fops)477 struct dentry *debugfs_create_file(const char *name, umode_t mode,
478 struct dentry *parent, void *data,
479 const struct file_operations *fops)
480 {
481
482 return __debugfs_create_file(name, mode, parent, data,
483 fops ? &debugfs_full_proxy_file_operations :
484 &debugfs_noop_file_operations,
485 fops);
486 }
487 EXPORT_SYMBOL_GPL(debugfs_create_file);
488
489 /**
490 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
491 * @name: a pointer to a string containing the name of the file to create.
492 * @mode: the permission that the file should have.
493 * @parent: a pointer to the parent dentry for this file. This should be a
494 * directory dentry if set. If this parameter is NULL, then the
495 * file will be created in the root of the debugfs filesystem.
496 * @data: a pointer to something that the caller will want to get to later
497 * on. The inode.i_private pointer will point to this value on
498 * the open() call.
499 * @fops: a pointer to a struct file_operations that should be used for
500 * this file.
501 *
502 * debugfs_create_file_unsafe() is completely analogous to
503 * debugfs_create_file(), the only difference being that the fops
504 * handed it will not get protected against file removals by the
505 * debugfs core.
506 *
507 * It is your responsibility to protect your struct file_operation
508 * methods against file removals by means of debugfs_file_get()
509 * and debugfs_file_put(). ->open() is still protected by
510 * debugfs though.
511 *
512 * Any struct file_operations defined by means of
513 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
514 * thus, may be used here.
515 */
debugfs_create_file_unsafe(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * fops)516 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
517 struct dentry *parent, void *data,
518 const struct file_operations *fops)
519 {
520
521 return __debugfs_create_file(name, mode, parent, data,
522 fops ? &debugfs_open_proxy_file_operations :
523 &debugfs_noop_file_operations,
524 fops);
525 }
526 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
527
528 /**
529 * debugfs_create_file_size - create a file in the debugfs filesystem
530 * @name: a pointer to a string containing the name of the file to create.
531 * @mode: the permission that the file should have.
532 * @parent: a pointer to the parent dentry for this file. This should be a
533 * directory dentry if set. If this parameter is NULL, then the
534 * file will be created in the root of the debugfs filesystem.
535 * @data: a pointer to something that the caller will want to get to later
536 * on. The inode.i_private pointer will point to this value on
537 * the open() call.
538 * @fops: a pointer to a struct file_operations that should be used for
539 * this file.
540 * @file_size: initial file size
541 *
542 * This is the basic "create a file" function for debugfs. It allows for a
543 * wide range of flexibility in creating a file, or a directory (if you want
544 * to create a directory, the debugfs_create_dir() function is
545 * recommended to be used instead.)
546 */
debugfs_create_file_size(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * fops,loff_t file_size)547 void debugfs_create_file_size(const char *name, umode_t mode,
548 struct dentry *parent, void *data,
549 const struct file_operations *fops,
550 loff_t file_size)
551 {
552 struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
553
554 if (!IS_ERR(de))
555 d_inode(de)->i_size = file_size;
556 }
557 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
558
559 /**
560 * debugfs_create_dir - create a directory in the debugfs filesystem
561 * @name: a pointer to a string containing the name of the directory to
562 * create.
563 * @parent: a pointer to the parent dentry for this file. This should be a
564 * directory dentry if set. If this parameter is NULL, then the
565 * directory will be created in the root of the debugfs filesystem.
566 *
567 * This function creates a directory in debugfs with the given name.
568 *
569 * This function will return a pointer to a dentry if it succeeds. This
570 * pointer must be passed to the debugfs_remove() function when the file is
571 * to be removed (no automatic cleanup happens if your module is unloaded,
572 * you are responsible here.) If an error occurs, ERR_PTR(-ERROR) will be
573 * returned.
574 *
575 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
576 * returned.
577 *
578 * NOTE: it's expected that most callers should _ignore_ the errors returned
579 * by this function. Other debugfs functions handle the fact that the "dentry"
580 * passed to them could be an error and they don't crash in that case.
581 * Drivers should generally work fine even if debugfs fails to init anyway.
582 */
debugfs_create_dir(const char * name,struct dentry * parent)583 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
584 {
585 struct dentry *dentry = start_creating(name, parent);
586 struct inode *inode;
587
588 if (IS_ERR(dentry))
589 return dentry;
590
591 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
592 failed_creating(dentry);
593 return ERR_PTR(-EPERM);
594 }
595
596 inode = debugfs_get_inode(dentry->d_sb);
597 if (unlikely(!inode)) {
598 pr_err("out of free dentries, can not create directory '%s'\n",
599 name);
600 return failed_creating(dentry);
601 }
602
603 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
604 inode->i_op = &debugfs_dir_inode_operations;
605 inode->i_fop = &simple_dir_operations;
606
607 /* directory inodes start off with i_nlink == 2 (for "." entry) */
608 inc_nlink(inode);
609 d_instantiate(dentry, inode);
610 inc_nlink(d_inode(dentry->d_parent));
611 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
612 return end_creating(dentry);
613 }
614 EXPORT_SYMBOL_GPL(debugfs_create_dir);
615
616 /**
617 * debugfs_create_automount - create automount point in the debugfs filesystem
618 * @name: a pointer to a string containing the name of the file to create.
619 * @parent: a pointer to the parent dentry for this file. This should be a
620 * directory dentry if set. If this parameter is NULL, then the
621 * file will be created in the root of the debugfs filesystem.
622 * @f: function to be called when pathname resolution steps on that one.
623 * @data: opaque argument to pass to f().
624 *
625 * @f should return what ->d_automount() would.
626 */
debugfs_create_automount(const char * name,struct dentry * parent,debugfs_automount_t f,void * data)627 struct dentry *debugfs_create_automount(const char *name,
628 struct dentry *parent,
629 debugfs_automount_t f,
630 void *data)
631 {
632 struct dentry *dentry = start_creating(name, parent);
633 struct debugfs_fsdata *fsd;
634 struct inode *inode;
635
636 if (IS_ERR(dentry))
637 return dentry;
638
639 fsd = kzalloc(sizeof(*fsd), GFP_KERNEL);
640 if (!fsd) {
641 failed_creating(dentry);
642 return ERR_PTR(-ENOMEM);
643 }
644
645 fsd->automount = f;
646
647 if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
648 failed_creating(dentry);
649 kfree(fsd);
650 return ERR_PTR(-EPERM);
651 }
652
653 inode = debugfs_get_inode(dentry->d_sb);
654 if (unlikely(!inode)) {
655 pr_err("out of free dentries, can not create automount '%s'\n",
656 name);
657 kfree(fsd);
658 return failed_creating(dentry);
659 }
660
661 make_empty_dir_inode(inode);
662 inode->i_flags |= S_AUTOMOUNT;
663 inode->i_private = data;
664 dentry->d_fsdata = fsd;
665 /* directory inodes start off with i_nlink == 2 (for "." entry) */
666 inc_nlink(inode);
667 d_instantiate(dentry, inode);
668 inc_nlink(d_inode(dentry->d_parent));
669 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
670 return end_creating(dentry);
671 }
672 EXPORT_SYMBOL(debugfs_create_automount);
673
674 /**
675 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
676 * @name: a pointer to a string containing the name of the symbolic link to
677 * create.
678 * @parent: a pointer to the parent dentry for this symbolic link. This
679 * should be a directory dentry if set. If this parameter is NULL,
680 * then the symbolic link will be created in the root of the debugfs
681 * filesystem.
682 * @target: a pointer to a string containing the path to the target of the
683 * symbolic link.
684 *
685 * This function creates a symbolic link with the given name in debugfs that
686 * links to the given target path.
687 *
688 * This function will return a pointer to a dentry if it succeeds. This
689 * pointer must be passed to the debugfs_remove() function when the symbolic
690 * link is to be removed (no automatic cleanup happens if your module is
691 * unloaded, you are responsible here.) If an error occurs, ERR_PTR(-ERROR)
692 * will be returned.
693 *
694 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
695 * returned.
696 */
debugfs_create_symlink(const char * name,struct dentry * parent,const char * target)697 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
698 const char *target)
699 {
700 struct dentry *dentry;
701 struct inode *inode;
702 char *link = kstrdup(target, GFP_KERNEL);
703 if (!link)
704 return ERR_PTR(-ENOMEM);
705
706 dentry = start_creating(name, parent);
707 if (IS_ERR(dentry)) {
708 kfree(link);
709 return dentry;
710 }
711
712 inode = debugfs_get_inode(dentry->d_sb);
713 if (unlikely(!inode)) {
714 pr_err("out of free dentries, can not create symlink '%s'\n",
715 name);
716 kfree(link);
717 return failed_creating(dentry);
718 }
719 inode->i_mode = S_IFLNK | S_IRWXUGO;
720 inode->i_op = &debugfs_symlink_inode_operations;
721 inode->i_link = link;
722 d_instantiate(dentry, inode);
723 return end_creating(dentry);
724 }
725 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
726
__debugfs_file_removed(struct dentry * dentry)727 static void __debugfs_file_removed(struct dentry *dentry)
728 {
729 struct debugfs_fsdata *fsd;
730
731 /*
732 * Paired with the closing smp_mb() implied by a successful
733 * cmpxchg() in debugfs_file_get(): either
734 * debugfs_file_get() must see a dead dentry or we must see a
735 * debugfs_fsdata instance at ->d_fsdata here (or both).
736 */
737 smp_mb();
738 fsd = READ_ONCE(dentry->d_fsdata);
739 if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
740 return;
741
742 /* if this was the last reference, we're done */
743 if (refcount_dec_and_test(&fsd->active_users))
744 return;
745
746 /*
747 * If there's still a reference, the code that obtained it can
748 * be in different states:
749 * - The common case of not using cancellations, or already
750 * after debugfs_leave_cancellation(), where we just need
751 * to wait for debugfs_file_put() which signals the completion;
752 * - inside a cancellation section, i.e. between
753 * debugfs_enter_cancellation() and debugfs_leave_cancellation(),
754 * in which case we need to trigger the ->cancel() function,
755 * and then wait for debugfs_file_put() just like in the
756 * previous case;
757 * - before debugfs_enter_cancellation() (but obviously after
758 * debugfs_file_get()), in which case we may not see the
759 * cancellation in the list on the first round of the loop,
760 * but debugfs_enter_cancellation() signals the completion
761 * after adding it, so this code gets woken up to call the
762 * ->cancel() function.
763 */
764 while (refcount_read(&fsd->active_users)) {
765 struct debugfs_cancellation *c;
766
767 /*
768 * Lock the cancellations. Note that the cancellations
769 * structs are meant to be on the stack, so we need to
770 * ensure we either use them here or don't touch them,
771 * and debugfs_leave_cancellation() will wait for this
772 * to be finished processing before exiting one. It may
773 * of course win and remove the cancellation, but then
774 * chances are we never even got into this bit, we only
775 * do if the refcount isn't zero already.
776 */
777 mutex_lock(&fsd->cancellations_mtx);
778 while ((c = list_first_entry_or_null(&fsd->cancellations,
779 typeof(*c), list))) {
780 list_del_init(&c->list);
781 c->cancel(dentry, c->cancel_data);
782 }
783 mutex_unlock(&fsd->cancellations_mtx);
784
785 wait_for_completion(&fsd->active_users_drained);
786 }
787 }
788
remove_one(struct dentry * victim)789 static void remove_one(struct dentry *victim)
790 {
791 if (d_is_reg(victim))
792 __debugfs_file_removed(victim);
793 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
794 }
795
796 /**
797 * debugfs_remove - recursively removes a directory
798 * @dentry: a pointer to a the dentry of the directory to be removed. If this
799 * parameter is NULL or an error value, nothing will be done.
800 *
801 * This function recursively removes a directory tree in debugfs that
802 * was previously created with a call to another debugfs function
803 * (like debugfs_create_file() or variants thereof.)
804 *
805 * This function is required to be called in order for the file to be
806 * removed, no automatic cleanup of files will happen when a module is
807 * removed, you are responsible here.
808 */
debugfs_remove(struct dentry * dentry)809 void debugfs_remove(struct dentry *dentry)
810 {
811 if (IS_ERR_OR_NULL(dentry))
812 return;
813
814 simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
815 simple_recursive_removal(dentry, remove_one);
816 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
817 }
818 EXPORT_SYMBOL_GPL(debugfs_remove);
819
820 /**
821 * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
822 * @name: a pointer to a string containing the name of the item to look up.
823 * @parent: a pointer to the parent dentry of the item.
824 *
825 * This is the equlivant of doing something like
826 * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
827 * handled for the directory being looked up.
828 */
debugfs_lookup_and_remove(const char * name,struct dentry * parent)829 void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
830 {
831 struct dentry *dentry;
832
833 dentry = debugfs_lookup(name, parent);
834 if (!dentry)
835 return;
836
837 debugfs_remove(dentry);
838 dput(dentry);
839 }
840 EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
841
842 /**
843 * debugfs_rename - rename a file/directory in the debugfs filesystem
844 * @old_dir: a pointer to the parent dentry for the renamed object. This
845 * should be a directory dentry.
846 * @old_dentry: dentry of an object to be renamed.
847 * @new_dir: a pointer to the parent dentry where the object should be
848 * moved. This should be a directory dentry.
849 * @new_name: a pointer to a string containing the target name.
850 *
851 * This function renames a file/directory in debugfs. The target must not
852 * exist for rename to succeed.
853 *
854 * This function will return a pointer to old_dentry (which is updated to
855 * reflect renaming) if it succeeds. If an error occurs, ERR_PTR(-ERROR)
856 * will be returned.
857 *
858 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
859 * returned.
860 */
debugfs_rename(struct dentry * old_dir,struct dentry * old_dentry,struct dentry * new_dir,const char * new_name)861 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
862 struct dentry *new_dir, const char *new_name)
863 {
864 int error;
865 struct dentry *dentry = NULL, *trap;
866 struct name_snapshot old_name;
867
868 if (IS_ERR(old_dir))
869 return old_dir;
870 if (IS_ERR(new_dir))
871 return new_dir;
872 if (IS_ERR_OR_NULL(old_dentry))
873 return old_dentry;
874
875 trap = lock_rename(new_dir, old_dir);
876 /* Source or destination directories don't exist? */
877 if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
878 goto exit;
879 /* Source does not exist, cyclic rename, or mountpoint? */
880 if (d_really_is_negative(old_dentry) || old_dentry == trap ||
881 d_mountpoint(old_dentry))
882 goto exit;
883 dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
884 /* Lookup failed, cyclic rename or target exists? */
885 if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
886 goto exit;
887
888 take_dentry_name_snapshot(&old_name, old_dentry);
889
890 error = simple_rename(&nop_mnt_idmap, d_inode(old_dir), old_dentry,
891 d_inode(new_dir), dentry, 0);
892 if (error) {
893 release_dentry_name_snapshot(&old_name);
894 goto exit;
895 }
896 d_move(old_dentry, dentry);
897 fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
898 d_is_dir(old_dentry),
899 NULL, old_dentry);
900 release_dentry_name_snapshot(&old_name);
901 unlock_rename(new_dir, old_dir);
902 dput(dentry);
903 return old_dentry;
904 exit:
905 if (dentry && !IS_ERR(dentry))
906 dput(dentry);
907 unlock_rename(new_dir, old_dir);
908 if (IS_ERR(dentry))
909 return dentry;
910 return ERR_PTR(-EINVAL);
911 }
912 EXPORT_SYMBOL_GPL(debugfs_rename);
913
914 /**
915 * debugfs_initialized - Tells whether debugfs has been registered
916 */
debugfs_initialized(void)917 bool debugfs_initialized(void)
918 {
919 return debugfs_registered;
920 }
921 EXPORT_SYMBOL_GPL(debugfs_initialized);
922
debugfs_kernel(char * str)923 static int __init debugfs_kernel(char *str)
924 {
925 if (str) {
926 if (!strcmp(str, "on"))
927 debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
928 else if (!strcmp(str, "no-mount"))
929 debugfs_allow = DEBUGFS_ALLOW_API;
930 else if (!strcmp(str, "off"))
931 debugfs_allow = 0;
932 }
933
934 return 0;
935 }
936 early_param("debugfs", debugfs_kernel);
debugfs_init(void)937 static int __init debugfs_init(void)
938 {
939 int retval;
940
941 if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
942 return -EPERM;
943
944 retval = sysfs_create_mount_point(kernel_kobj, "debug");
945 if (retval)
946 return retval;
947
948 retval = register_filesystem(&debug_fs_type);
949 if (retval)
950 sysfs_remove_mount_point(kernel_kobj, "debug");
951 else
952 debugfs_registered = true;
953
954 return retval;
955 }
956 core_initcall(debugfs_init);
957