xref: /openbmc/linux/fs/debugfs/inode.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  *  file.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 /* uncomment to get debug messages from the debug filesystem, ah the irony. */
17 /* #define DEBUG */
18 
19 #include <linux/config.h>
20 #include <linux/module.h>
21 #include <linux/fs.h>
22 #include <linux/mount.h>
23 #include <linux/pagemap.h>
24 #include <linux/init.h>
25 #include <linux/namei.h>
26 #include <linux/debugfs.h>
27 
28 #define DEBUGFS_MAGIC	0x64626720
29 
30 /* declared over in file.c */
31 extern struct file_operations debugfs_file_operations;
32 
33 static struct vfsmount *debugfs_mount;
34 static int debugfs_mount_count;
35 
36 static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev)
37 {
38 	struct inode *inode = new_inode(sb);
39 
40 	if (inode) {
41 		inode->i_mode = mode;
42 		inode->i_uid = 0;
43 		inode->i_gid = 0;
44 		inode->i_blksize = PAGE_CACHE_SIZE;
45 		inode->i_blocks = 0;
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 = &debugfs_file_operations;
53 			break;
54 		case S_IFDIR:
55 			inode->i_op = &simple_dir_inode_operations;
56 			inode->i_fop = &simple_dir_operations;
57 
58 			/* directory inodes start off with i_nlink == 2 (for "." entry) */
59 			inode->i_nlink++;
60 			break;
61 		}
62 	}
63 	return inode;
64 }
65 
66 /* SMP-safe */
67 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
68 			 int mode, dev_t dev)
69 {
70 	struct inode *inode = debugfs_get_inode(dir->i_sb, mode, dev);
71 	int error = -EPERM;
72 
73 	if (dentry->d_inode)
74 		return -EEXIST;
75 
76 	if (inode) {
77 		d_instantiate(dentry, inode);
78 		dget(dentry);
79 		error = 0;
80 	}
81 	return error;
82 }
83 
84 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
85 {
86 	int res;
87 
88 	mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
89 	res = debugfs_mknod(dir, dentry, mode, 0);
90 	if (!res)
91 		dir->i_nlink++;
92 	return res;
93 }
94 
95 static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode)
96 {
97 	mode = (mode & S_IALLUGO) | S_IFREG;
98 	return debugfs_mknod(dir, dentry, mode, 0);
99 }
100 
101 static inline int debugfs_positive(struct dentry *dentry)
102 {
103 	return dentry->d_inode && !d_unhashed(dentry);
104 }
105 
106 static int debug_fill_super(struct super_block *sb, void *data, int silent)
107 {
108 	static struct tree_descr debug_files[] = {{""}};
109 
110 	return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
111 }
112 
113 static struct super_block *debug_get_sb(struct file_system_type *fs_type,
114 				        int flags, const char *dev_name,
115 					void *data)
116 {
117 	return get_sb_single(fs_type, flags, data, debug_fill_super);
118 }
119 
120 static struct file_system_type debug_fs_type = {
121 	.owner =	THIS_MODULE,
122 	.name =		"debugfs",
123 	.get_sb =	debug_get_sb,
124 	.kill_sb =	kill_litter_super,
125 };
126 
127 static int debugfs_create_by_name(const char *name, mode_t mode,
128 				  struct dentry *parent,
129 				  struct dentry **dentry)
130 {
131 	int error = 0;
132 
133 	/* If the parent is not specified, we create it in the root.
134 	 * We need the root dentry to do this, which is in the super
135 	 * block. A pointer to that is in the struct vfsmount that we
136 	 * have around.
137 	 */
138 	if (!parent ) {
139 		if (debugfs_mount && debugfs_mount->mnt_sb) {
140 			parent = debugfs_mount->mnt_sb->s_root;
141 		}
142 	}
143 	if (!parent) {
144 		pr_debug("debugfs: Ah! can not find a parent!\n");
145 		return -EFAULT;
146 	}
147 
148 	*dentry = NULL;
149 	down(&parent->d_inode->i_sem);
150 	*dentry = lookup_one_len(name, parent, strlen(name));
151 	if (!IS_ERR(dentry)) {
152 		if ((mode & S_IFMT) == S_IFDIR)
153 			error = debugfs_mkdir(parent->d_inode, *dentry, mode);
154 		else
155 			error = debugfs_create(parent->d_inode, *dentry, mode);
156 	} else
157 		error = PTR_ERR(dentry);
158 	up(&parent->d_inode->i_sem);
159 
160 	return error;
161 }
162 
163 /**
164  * debugfs_create_file - create a file in the debugfs filesystem
165  *
166  * @name: a pointer to a string containing the name of the file to create.
167  * @mode: the permission that the file should have
168  * @parent: a pointer to the parent dentry for this file.  This should be a
169  *          directory dentry if set.  If this paramater is NULL, then the
170  *          file will be created in the root of the debugfs filesystem.
171  * @data: a pointer to something that the caller will want to get to later
172  *        on.  The inode.u.generic_ip pointer will point to this value on
173  *        the open() call.
174  * @fops: a pointer to a struct file_operations that should be used for
175  *        this file.
176  *
177  * This is the basic "create a file" function for debugfs.  It allows for a
178  * wide range of flexibility in createing a file, or a directory (if you
179  * want to create a directory, the debugfs_create_dir() function is
180  * recommended to be used instead.)
181  *
182  * This function will return a pointer to a dentry if it succeeds.  This
183  * pointer must be passed to the debugfs_remove() function when the file is
184  * to be removed (no automatic cleanup happens if your module is unloaded,
185  * you are responsible here.)  If an error occurs, NULL will be returned.
186  *
187  * If debugfs is not enabled in the kernel, the value -ENODEV will be
188  * returned.  It is not wise to check for this value, but rather, check for
189  * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
190  * code.
191  */
192 struct dentry *debugfs_create_file(const char *name, mode_t mode,
193 				   struct dentry *parent, void *data,
194 				   struct file_operations *fops)
195 {
196 	struct dentry *dentry = NULL;
197 	int error;
198 
199 	pr_debug("debugfs: creating file '%s'\n",name);
200 
201 	error = simple_pin_fs("debugfs", &debugfs_mount, &debugfs_mount_count);
202 	if (error)
203 		goto exit;
204 
205 	error = debugfs_create_by_name(name, mode, parent, &dentry);
206 	if (error) {
207 		dentry = NULL;
208 		goto exit;
209 	}
210 
211 	if (dentry->d_inode) {
212 		if (data)
213 			dentry->d_inode->u.generic_ip = data;
214 		if (fops)
215 			dentry->d_inode->i_fop = fops;
216 	}
217 exit:
218 	return dentry;
219 }
220 EXPORT_SYMBOL_GPL(debugfs_create_file);
221 
222 /**
223  * debugfs_create_dir - create a directory in the debugfs filesystem
224  *
225  * @name: a pointer to a string containing the name of the directory to
226  *        create.
227  * @parent: a pointer to the parent dentry for this file.  This should be a
228  *          directory dentry if set.  If this paramater is NULL, then the
229  *          directory will be created in the root of the debugfs filesystem.
230  *
231  * This function creates a directory in debugfs with the given name.
232  *
233  * This function will return a pointer to a dentry if it succeeds.  This
234  * pointer must be passed to the debugfs_remove() function when the file is
235  * to be removed (no automatic cleanup happens if your module is unloaded,
236  * you are responsible here.)  If an error occurs, NULL will be returned.
237  *
238  * If debugfs is not enabled in the kernel, the value -ENODEV will be
239  * returned.  It is not wise to check for this value, but rather, check for
240  * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
241  * code.
242  */
243 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
244 {
245 	return debugfs_create_file(name,
246 				   S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
247 				   parent, NULL, NULL);
248 }
249 EXPORT_SYMBOL_GPL(debugfs_create_dir);
250 
251 /**
252  * debugfs_remove - removes a file or directory from the debugfs filesystem
253  *
254  * @dentry: a pointer to a the dentry of the file or directory to be
255  *          removed.
256  *
257  * This function removes a file or directory in debugfs that was previously
258  * created with a call to another debugfs function (like
259  * debufs_create_file() or variants thereof.)
260  *
261  * This function is required to be called in order for the file to be
262  * removed, no automatic cleanup of files will happen when a module is
263  * removed, you are responsible here.
264  */
265 void debugfs_remove(struct dentry *dentry)
266 {
267 	struct dentry *parent;
268 
269 	if (!dentry)
270 		return;
271 
272 	parent = dentry->d_parent;
273 	if (!parent || !parent->d_inode)
274 		return;
275 
276 	down(&parent->d_inode->i_sem);
277 	if (debugfs_positive(dentry)) {
278 		if (dentry->d_inode) {
279 			if (S_ISDIR(dentry->d_inode->i_mode))
280 				simple_rmdir(parent->d_inode, dentry);
281 			else
282 				simple_unlink(parent->d_inode, dentry);
283 		dput(dentry);
284 		}
285 	}
286 	up(&parent->d_inode->i_sem);
287 	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
288 }
289 EXPORT_SYMBOL_GPL(debugfs_remove);
290 
291 static decl_subsys(debug, NULL, NULL);
292 
293 static int __init debugfs_init(void)
294 {
295 	int retval;
296 
297 	kset_set_kset_s(&debug_subsys, kernel_subsys);
298 	retval = subsystem_register(&debug_subsys);
299 	if (retval)
300 		return retval;
301 
302 	retval = register_filesystem(&debug_fs_type);
303 	if (retval)
304 		subsystem_unregister(&debug_subsys);
305 	return retval;
306 }
307 
308 static void __exit debugfs_exit(void)
309 {
310 	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
311 	unregister_filesystem(&debug_fs_type);
312 	subsystem_unregister(&debug_subsys);
313 }
314 
315 core_initcall(debugfs_init);
316 module_exit(debugfs_exit);
317 MODULE_LICENSE("GPL");
318 
319