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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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 */
31extern struct file_operations debugfs_file_operations;
32
33static struct vfsmount *debugfs_mount;
34static int debugfs_mount_count;
35
36static 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 */
67static 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
84static 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
95static 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
101static inline int debugfs_positive(struct dentry *dentry)
102{
103 return dentry->d_inode && !d_unhashed(dentry);
104}
105
106static 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
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113static 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
120static 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
127static 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);
Christoph Hellwig5f45f1a2005-06-23 00:09:12 -0700150 *dentry = lookup_one_len(name, parent, strlen(name));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151 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 */
192struct 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 }
217exit:
218 return dentry;
219}
220EXPORT_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 */
243struct 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}
249EXPORT_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 */
265void 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}
289EXPORT_SYMBOL_GPL(debugfs_remove);
290
291static decl_subsys(debug, NULL, NULL);
292
293static 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
308static 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
315core_initcall(debugfs_init);
316module_exit(debugfs_exit);
317MODULE_LICENSE("GPL");
318