xref: /openbmc/linux/fs/debugfs/inode.c (revision e23feb16)
1 /*
2  *  inode.c - part of debugfs, a tiny little debug file system
3  *
4  *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
5  *  Copyright (C) 2004 IBM Inc.
6  *
7  *	This program is free software; you can redistribute it and/or
8  *	modify it under the terms of the GNU General Public License version
9  *	2 as published by the Free Software Foundation.
10  *
11  *  debugfs is for people to use instead of /proc or /sys.
12  *  See Documentation/DocBook/kernel-api for more details.
13  *
14  */
15 
16 #include <linux/module.h>
17 #include <linux/fs.h>
18 #include <linux/mount.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/parser.h>
28 #include <linux/magic.h>
29 #include <linux/slab.h>
30 
31 #define DEBUGFS_DEFAULT_MODE	0700
32 
33 static struct vfsmount *debugfs_mount;
34 static int debugfs_mount_count;
35 static bool debugfs_registered;
36 
37 static struct inode *debugfs_get_inode(struct super_block *sb, umode_t mode, dev_t dev,
38 				       void *data, const struct file_operations *fops)
39 
40 {
41 	struct inode *inode = new_inode(sb);
42 
43 	if (inode) {
44 		inode->i_ino = get_next_ino();
45 		inode->i_mode = mode;
46 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
47 		switch (mode & S_IFMT) {
48 		default:
49 			init_special_inode(inode, mode, dev);
50 			break;
51 		case S_IFREG:
52 			inode->i_fop = fops ? fops : &debugfs_file_operations;
53 			inode->i_private = data;
54 			break;
55 		case S_IFLNK:
56 			inode->i_op = &debugfs_link_operations;
57 			inode->i_private = data;
58 			break;
59 		case S_IFDIR:
60 			inode->i_op = &simple_dir_inode_operations;
61 			inode->i_fop = &simple_dir_operations;
62 
63 			/* directory inodes start off with i_nlink == 2
64 			 * (for "." entry) */
65 			inc_nlink(inode);
66 			break;
67 		}
68 	}
69 	return inode;
70 }
71 
72 /* SMP-safe */
73 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
74 			 umode_t mode, dev_t dev, void *data,
75 			 const struct file_operations *fops)
76 {
77 	struct inode *inode;
78 	int error = -EPERM;
79 
80 	if (dentry->d_inode)
81 		return -EEXIST;
82 
83 	inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops);
84 	if (inode) {
85 		d_instantiate(dentry, inode);
86 		dget(dentry);
87 		error = 0;
88 	}
89 	return error;
90 }
91 
92 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
93 {
94 	int res;
95 
96 	mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
97 	res = debugfs_mknod(dir, dentry, mode, 0, NULL, NULL);
98 	if (!res) {
99 		inc_nlink(dir);
100 		fsnotify_mkdir(dir, dentry);
101 	}
102 	return res;
103 }
104 
105 static int debugfs_link(struct inode *dir, struct dentry *dentry, umode_t mode,
106 			void *data)
107 {
108 	mode = (mode & S_IALLUGO) | S_IFLNK;
109 	return debugfs_mknod(dir, dentry, mode, 0, data, NULL);
110 }
111 
112 static int debugfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
113 			  void *data, const struct file_operations *fops)
114 {
115 	int res;
116 
117 	mode = (mode & S_IALLUGO) | S_IFREG;
118 	res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
119 	if (!res)
120 		fsnotify_create(dir, dentry);
121 	return res;
122 }
123 
124 static inline int debugfs_positive(struct dentry *dentry)
125 {
126 	return dentry->d_inode && !d_unhashed(dentry);
127 }
128 
129 struct debugfs_mount_opts {
130 	kuid_t uid;
131 	kgid_t gid;
132 	umode_t mode;
133 };
134 
135 enum {
136 	Opt_uid,
137 	Opt_gid,
138 	Opt_mode,
139 	Opt_err
140 };
141 
142 static const match_table_t tokens = {
143 	{Opt_uid, "uid=%u"},
144 	{Opt_gid, "gid=%u"},
145 	{Opt_mode, "mode=%o"},
146 	{Opt_err, NULL}
147 };
148 
149 struct debugfs_fs_info {
150 	struct debugfs_mount_opts mount_opts;
151 };
152 
153 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
154 {
155 	substring_t args[MAX_OPT_ARGS];
156 	int option;
157 	int token;
158 	kuid_t uid;
159 	kgid_t gid;
160 	char *p;
161 
162 	opts->mode = DEBUGFS_DEFAULT_MODE;
163 
164 	while ((p = strsep(&data, ",")) != NULL) {
165 		if (!*p)
166 			continue;
167 
168 		token = match_token(p, tokens, args);
169 		switch (token) {
170 		case Opt_uid:
171 			if (match_int(&args[0], &option))
172 				return -EINVAL;
173 			uid = make_kuid(current_user_ns(), option);
174 			if (!uid_valid(uid))
175 				return -EINVAL;
176 			opts->uid = uid;
177 			break;
178 		case Opt_gid:
179 			if (match_int(&args[0], &option))
180 				return -EINVAL;
181 			gid = make_kgid(current_user_ns(), option);
182 			if (!gid_valid(gid))
183 				return -EINVAL;
184 			opts->gid = gid;
185 			break;
186 		case Opt_mode:
187 			if (match_octal(&args[0], &option))
188 				return -EINVAL;
189 			opts->mode = option & S_IALLUGO;
190 			break;
191 		/*
192 		 * We might like to report bad mount options here;
193 		 * but traditionally debugfs has ignored all mount options
194 		 */
195 		}
196 	}
197 
198 	return 0;
199 }
200 
201 static int debugfs_apply_options(struct super_block *sb)
202 {
203 	struct debugfs_fs_info *fsi = sb->s_fs_info;
204 	struct inode *inode = sb->s_root->d_inode;
205 	struct debugfs_mount_opts *opts = &fsi->mount_opts;
206 
207 	inode->i_mode &= ~S_IALLUGO;
208 	inode->i_mode |= opts->mode;
209 
210 	inode->i_uid = opts->uid;
211 	inode->i_gid = opts->gid;
212 
213 	return 0;
214 }
215 
216 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
217 {
218 	int err;
219 	struct debugfs_fs_info *fsi = sb->s_fs_info;
220 
221 	err = debugfs_parse_options(data, &fsi->mount_opts);
222 	if (err)
223 		goto fail;
224 
225 	debugfs_apply_options(sb);
226 
227 fail:
228 	return err;
229 }
230 
231 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
232 {
233 	struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
234 	struct debugfs_mount_opts *opts = &fsi->mount_opts;
235 
236 	if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
237 		seq_printf(m, ",uid=%u",
238 			   from_kuid_munged(&init_user_ns, opts->uid));
239 	if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
240 		seq_printf(m, ",gid=%u",
241 			   from_kgid_munged(&init_user_ns, opts->gid));
242 	if (opts->mode != DEBUGFS_DEFAULT_MODE)
243 		seq_printf(m, ",mode=%o", opts->mode);
244 
245 	return 0;
246 }
247 
248 static const struct super_operations debugfs_super_operations = {
249 	.statfs		= simple_statfs,
250 	.remount_fs	= debugfs_remount,
251 	.show_options	= debugfs_show_options,
252 };
253 
254 static int debug_fill_super(struct super_block *sb, void *data, int silent)
255 {
256 	static struct tree_descr debug_files[] = {{""}};
257 	struct debugfs_fs_info *fsi;
258 	int err;
259 
260 	save_mount_options(sb, data);
261 
262 	fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
263 	sb->s_fs_info = fsi;
264 	if (!fsi) {
265 		err = -ENOMEM;
266 		goto fail;
267 	}
268 
269 	err = debugfs_parse_options(data, &fsi->mount_opts);
270 	if (err)
271 		goto fail;
272 
273 	err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
274 	if (err)
275 		goto fail;
276 
277 	sb->s_op = &debugfs_super_operations;
278 
279 	debugfs_apply_options(sb);
280 
281 	return 0;
282 
283 fail:
284 	kfree(fsi);
285 	sb->s_fs_info = NULL;
286 	return err;
287 }
288 
289 static struct dentry *debug_mount(struct file_system_type *fs_type,
290 			int flags, const char *dev_name,
291 			void *data)
292 {
293 	return mount_single(fs_type, flags, data, debug_fill_super);
294 }
295 
296 static struct file_system_type debug_fs_type = {
297 	.owner =	THIS_MODULE,
298 	.name =		"debugfs",
299 	.mount =	debug_mount,
300 	.kill_sb =	kill_litter_super,
301 };
302 MODULE_ALIAS_FS("debugfs");
303 
304 static struct dentry *__create_file(const char *name, umode_t mode,
305 				    struct dentry *parent, void *data,
306 				    const struct file_operations *fops)
307 {
308 	struct dentry *dentry = NULL;
309 	int error;
310 
311 	pr_debug("debugfs: creating file '%s'\n",name);
312 
313 	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
314 			      &debugfs_mount_count);
315 	if (error)
316 		goto exit;
317 
318 	/* If the parent is not specified, we create it in the root.
319 	 * We need the root dentry to do this, which is in the super
320 	 * block. A pointer to that is in the struct vfsmount that we
321 	 * have around.
322 	 */
323 	if (!parent)
324 		parent = debugfs_mount->mnt_root;
325 
326 	mutex_lock(&parent->d_inode->i_mutex);
327 	dentry = lookup_one_len(name, parent, strlen(name));
328 	if (!IS_ERR(dentry)) {
329 		switch (mode & S_IFMT) {
330 		case S_IFDIR:
331 			error = debugfs_mkdir(parent->d_inode, dentry, mode);
332 
333 			break;
334 		case S_IFLNK:
335 			error = debugfs_link(parent->d_inode, dentry, mode,
336 					     data);
337 			break;
338 		default:
339 			error = debugfs_create(parent->d_inode, dentry, mode,
340 					       data, fops);
341 			break;
342 		}
343 		dput(dentry);
344 	} else
345 		error = PTR_ERR(dentry);
346 	mutex_unlock(&parent->d_inode->i_mutex);
347 
348 	if (error) {
349 		dentry = NULL;
350 		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
351 	}
352 exit:
353 	return dentry;
354 }
355 
356 /**
357  * debugfs_create_file - create a file in the debugfs filesystem
358  * @name: a pointer to a string containing the name of the file to create.
359  * @mode: the permission that the file should have.
360  * @parent: a pointer to the parent dentry for this file.  This should be a
361  *          directory dentry if set.  If this paramater is NULL, then the
362  *          file will be created in the root of the debugfs filesystem.
363  * @data: a pointer to something that the caller will want to get to later
364  *        on.  The inode.i_private pointer will point to this value on
365  *        the open() call.
366  * @fops: a pointer to a struct file_operations that should be used for
367  *        this file.
368  *
369  * This is the basic "create a file" function for debugfs.  It allows for a
370  * wide range of flexibility in creating a file, or a directory (if you want
371  * to create a directory, the debugfs_create_dir() function is
372  * recommended to be used instead.)
373  *
374  * This function will return a pointer to a dentry if it succeeds.  This
375  * pointer must be passed to the debugfs_remove() function when the file is
376  * to be removed (no automatic cleanup happens if your module is unloaded,
377  * you are responsible here.)  If an error occurs, %NULL will be returned.
378  *
379  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
380  * returned.
381  */
382 struct dentry *debugfs_create_file(const char *name, umode_t mode,
383 				   struct dentry *parent, void *data,
384 				   const struct file_operations *fops)
385 {
386 	switch (mode & S_IFMT) {
387 	case S_IFREG:
388 	case 0:
389 		break;
390 	default:
391 		BUG();
392 	}
393 
394 	return __create_file(name, mode, parent, data, fops);
395 }
396 EXPORT_SYMBOL_GPL(debugfs_create_file);
397 
398 /**
399  * debugfs_create_dir - create a directory in the debugfs filesystem
400  * @name: a pointer to a string containing the name of the directory to
401  *        create.
402  * @parent: a pointer to the parent dentry for this file.  This should be a
403  *          directory dentry if set.  If this paramater is NULL, then the
404  *          directory will be created in the root of the debugfs filesystem.
405  *
406  * This function creates a directory in debugfs with the given name.
407  *
408  * This function will return a pointer to a dentry if it succeeds.  This
409  * pointer must be passed to the debugfs_remove() function when the file is
410  * to be removed (no automatic cleanup happens if your module is unloaded,
411  * you are responsible here.)  If an error occurs, %NULL will be returned.
412  *
413  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
414  * returned.
415  */
416 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
417 {
418 	return __create_file(name, S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
419 				   parent, NULL, NULL);
420 }
421 EXPORT_SYMBOL_GPL(debugfs_create_dir);
422 
423 /**
424  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
425  * @name: a pointer to a string containing the name of the symbolic link to
426  *        create.
427  * @parent: a pointer to the parent dentry for this symbolic link.  This
428  *          should be a directory dentry if set.  If this paramater is NULL,
429  *          then the symbolic link will be created in the root of the debugfs
430  *          filesystem.
431  * @target: a pointer to a string containing the path to the target of the
432  *          symbolic link.
433  *
434  * This function creates a symbolic link with the given name in debugfs that
435  * links to the given target path.
436  *
437  * This function will return a pointer to a dentry if it succeeds.  This
438  * pointer must be passed to the debugfs_remove() function when the symbolic
439  * link is to be removed (no automatic cleanup happens if your module is
440  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
441  * returned.
442  *
443  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
444  * returned.
445  */
446 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
447 				      const char *target)
448 {
449 	struct dentry *result;
450 	char *link;
451 
452 	link = kstrdup(target, GFP_KERNEL);
453 	if (!link)
454 		return NULL;
455 
456 	result = __create_file(name, S_IFLNK | S_IRWXUGO, parent, link, NULL);
457 	if (!result)
458 		kfree(link);
459 	return result;
460 }
461 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
462 
463 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
464 {
465 	int ret = 0;
466 
467 	if (debugfs_positive(dentry)) {
468 		if (dentry->d_inode) {
469 			dget(dentry);
470 			switch (dentry->d_inode->i_mode & S_IFMT) {
471 			case S_IFDIR:
472 				ret = simple_rmdir(parent->d_inode, dentry);
473 				break;
474 			case S_IFLNK:
475 				kfree(dentry->d_inode->i_private);
476 				/* fall through */
477 			default:
478 				simple_unlink(parent->d_inode, dentry);
479 				break;
480 			}
481 			if (!ret)
482 				d_delete(dentry);
483 			dput(dentry);
484 		}
485 	}
486 	return ret;
487 }
488 
489 /**
490  * debugfs_remove - removes a file or directory from the debugfs filesystem
491  * @dentry: a pointer to a the dentry of the file or directory to be
492  *          removed.
493  *
494  * This function removes a file or directory in debugfs that was previously
495  * created with a call to another debugfs function (like
496  * debugfs_create_file() or variants thereof.)
497  *
498  * This function is required to be called in order for the file to be
499  * removed, no automatic cleanup of files will happen when a module is
500  * removed, you are responsible here.
501  */
502 void debugfs_remove(struct dentry *dentry)
503 {
504 	struct dentry *parent;
505 	int ret;
506 
507 	if (IS_ERR_OR_NULL(dentry))
508 		return;
509 
510 	parent = dentry->d_parent;
511 	if (!parent || !parent->d_inode)
512 		return;
513 
514 	mutex_lock(&parent->d_inode->i_mutex);
515 	ret = __debugfs_remove(dentry, parent);
516 	mutex_unlock(&parent->d_inode->i_mutex);
517 	if (!ret)
518 		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
519 }
520 EXPORT_SYMBOL_GPL(debugfs_remove);
521 
522 /**
523  * debugfs_remove_recursive - recursively removes a directory
524  * @dentry: a pointer to a the dentry of the directory to be removed.
525  *
526  * This function recursively removes a directory tree in debugfs that
527  * was previously created with a call to another debugfs function
528  * (like debugfs_create_file() or variants thereof.)
529  *
530  * This function is required to be called in order for the file to be
531  * removed, no automatic cleanup of files will happen when a module is
532  * removed, you are responsible here.
533  */
534 void debugfs_remove_recursive(struct dentry *dentry)
535 {
536 	struct dentry *child, *next, *parent;
537 
538 	if (IS_ERR_OR_NULL(dentry))
539 		return;
540 
541 	parent = dentry->d_parent;
542 	if (!parent || !parent->d_inode)
543 		return;
544 
545 	parent = dentry;
546  down:
547 	mutex_lock(&parent->d_inode->i_mutex);
548 	list_for_each_entry_safe(child, next, &parent->d_subdirs, d_u.d_child) {
549 		if (!debugfs_positive(child))
550 			continue;
551 
552 		/* perhaps simple_empty(child) makes more sense */
553 		if (!list_empty(&child->d_subdirs)) {
554 			mutex_unlock(&parent->d_inode->i_mutex);
555 			parent = child;
556 			goto down;
557 		}
558  up:
559 		if (!__debugfs_remove(child, parent))
560 			simple_release_fs(&debugfs_mount, &debugfs_mount_count);
561 	}
562 
563 	mutex_unlock(&parent->d_inode->i_mutex);
564 	child = parent;
565 	parent = parent->d_parent;
566 	mutex_lock(&parent->d_inode->i_mutex);
567 
568 	if (child != dentry) {
569 		next = list_entry(child->d_u.d_child.next, struct dentry,
570 					d_u.d_child);
571 		goto up;
572 	}
573 
574 	if (!__debugfs_remove(child, parent))
575 		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
576 	mutex_unlock(&parent->d_inode->i_mutex);
577 }
578 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
579 
580 /**
581  * debugfs_rename - rename a file/directory in the debugfs filesystem
582  * @old_dir: a pointer to the parent dentry for the renamed object. This
583  *          should be a directory dentry.
584  * @old_dentry: dentry of an object to be renamed.
585  * @new_dir: a pointer to the parent dentry where the object should be
586  *          moved. This should be a directory dentry.
587  * @new_name: a pointer to a string containing the target name.
588  *
589  * This function renames a file/directory in debugfs.  The target must not
590  * exist for rename to succeed.
591  *
592  * This function will return a pointer to old_dentry (which is updated to
593  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
594  * returned.
595  *
596  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
597  * returned.
598  */
599 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
600 		struct dentry *new_dir, const char *new_name)
601 {
602 	int error;
603 	struct dentry *dentry = NULL, *trap;
604 	const char *old_name;
605 
606 	trap = lock_rename(new_dir, old_dir);
607 	/* Source or destination directories don't exist? */
608 	if (!old_dir->d_inode || !new_dir->d_inode)
609 		goto exit;
610 	/* Source does not exist, cyclic rename, or mountpoint? */
611 	if (!old_dentry->d_inode || old_dentry == trap ||
612 	    d_mountpoint(old_dentry))
613 		goto exit;
614 	dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
615 	/* Lookup failed, cyclic rename or target exists? */
616 	if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
617 		goto exit;
618 
619 	old_name = fsnotify_oldname_init(old_dentry->d_name.name);
620 
621 	error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
622 		dentry);
623 	if (error) {
624 		fsnotify_oldname_free(old_name);
625 		goto exit;
626 	}
627 	d_move(old_dentry, dentry);
628 	fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
629 		S_ISDIR(old_dentry->d_inode->i_mode),
630 		NULL, old_dentry);
631 	fsnotify_oldname_free(old_name);
632 	unlock_rename(new_dir, old_dir);
633 	dput(dentry);
634 	return old_dentry;
635 exit:
636 	if (dentry && !IS_ERR(dentry))
637 		dput(dentry);
638 	unlock_rename(new_dir, old_dir);
639 	return NULL;
640 }
641 EXPORT_SYMBOL_GPL(debugfs_rename);
642 
643 /**
644  * debugfs_initialized - Tells whether debugfs has been registered
645  */
646 bool debugfs_initialized(void)
647 {
648 	return debugfs_registered;
649 }
650 EXPORT_SYMBOL_GPL(debugfs_initialized);
651 
652 
653 static struct kobject *debug_kobj;
654 
655 static int __init debugfs_init(void)
656 {
657 	int retval;
658 
659 	debug_kobj = kobject_create_and_add("debug", kernel_kobj);
660 	if (!debug_kobj)
661 		return -EINVAL;
662 
663 	retval = register_filesystem(&debug_fs_type);
664 	if (retval)
665 		kobject_put(debug_kobj);
666 	else
667 		debugfs_registered = true;
668 
669 	return retval;
670 }
671 core_initcall(debugfs_init);
672 
673