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 dentry * get_dentry(struct dentry *parent, const char *name)
114 {
115 struct qstr qstr;
116
117 qstr.name = name;
118 qstr.len = strlen(name);
119 qstr.hash = full_name_hash(name,qstr.len);
120 return lookup_hash(&qstr,parent);
121 }
122
123 static struct super_block *debug_get_sb(struct file_system_type *fs_type,
124 int flags, const char *dev_name,
125 void *data)
126 {
127 return get_sb_single(fs_type, flags, data, debug_fill_super);
128 }
129
130 static struct file_system_type debug_fs_type = {
131 .owner = THIS_MODULE,
132 .name = "debugfs",
133 .get_sb = debug_get_sb,
134 .kill_sb = kill_litter_super,
135 };
136
137 static int debugfs_create_by_name(const char *name, mode_t mode,
138 struct dentry *parent,
139 struct dentry **dentry)
140 {
141 int error = 0;
142
143 /* If the parent is not specified, we create it in the root.
144 * We need the root dentry to do this, which is in the super
145 * block. A pointer to that is in the struct vfsmount that we
146 * have around.
147 */
148 if (!parent ) {
149 if (debugfs_mount && debugfs_mount->mnt_sb) {
150 parent = debugfs_mount->mnt_sb->s_root;
151 }
152 }
153 if (!parent) {
154 pr_debug("debugfs: Ah! can not find a parent!\n");
155 return -EFAULT;
156 }
157
158 *dentry = NULL;
159 down(&parent->d_inode->i_sem);
160 *dentry = get_dentry (parent, name);
161 if (!IS_ERR(dentry)) {
162 if ((mode & S_IFMT) == S_IFDIR)
163 error = debugfs_mkdir(parent->d_inode, *dentry, mode);
164 else
165 error = debugfs_create(parent->d_inode, *dentry, mode);
166 } else
167 error = PTR_ERR(dentry);
168 up(&parent->d_inode->i_sem);
169
170 return error;
171 }
172
173 /**
174 * debugfs_create_file - create a file in the debugfs filesystem
175 *
176 * @name: a pointer to a string containing the name of the file to create.
177 * @mode: the permission that the file should have
178 * @parent: a pointer to the parent dentry for this file. This should be a
179 * directory dentry if set. If this paramater is NULL, then the
180 * file will be created in the root of the debugfs filesystem.
181 * @data: a pointer to something that the caller will want to get to later
182 * on. The inode.u.generic_ip pointer will point to this value on
183 * the open() call.
184 * @fops: a pointer to a struct file_operations that should be used for
185 * this file.
186 *
187 * This is the basic "create a file" function for debugfs. It allows for a
188 * wide range of flexibility in createing a file, or a directory (if you
189 * want to create a directory, the debugfs_create_dir() function is
190 * recommended to be used instead.)
191 *
192 * This function will return a pointer to a dentry if it succeeds. This
193 * pointer must be passed to the debugfs_remove() function when the file is
194 * to be removed (no automatic cleanup happens if your module is unloaded,
195 * you are responsible here.) If an error occurs, NULL will be returned.
196 *
197 * If debugfs is not enabled in the kernel, the value -ENODEV will be
198 * returned. It is not wise to check for this value, but rather, check for
199 * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
200 * code.
201 */
202 struct dentry *debugfs_create_file(const char *name, mode_t mode,
203 struct dentry *parent, void *data,
204 struct file_operations *fops)
205 {
206 struct dentry *dentry = NULL;
207 int error;
208
209 pr_debug("debugfs: creating file '%s'\n",name);
210
211 error = simple_pin_fs("debugfs", &debugfs_mount, &debugfs_mount_count);
212 if (error)
213 goto exit;
214
215 error = debugfs_create_by_name(name, mode, parent, &dentry);
216 if (error) {
217 dentry = NULL;
218 goto exit;
219 }
220
221 if (dentry->d_inode) {
222 if (data)
223 dentry->d_inode->u.generic_ip = data;
224 if (fops)
225 dentry->d_inode->i_fop = fops;
226 }
227 exit:
228 return dentry;
229 }
230 EXPORT_SYMBOL_GPL(debugfs_create_file);
231
232 /**
233 * debugfs_create_dir - create a directory in the debugfs filesystem
234 *
235 * @name: a pointer to a string containing the name of the directory to
236 * create.
237 * @parent: a pointer to the parent dentry for this file. This should be a
238 * directory dentry if set. If this paramater is NULL, then the
239 * directory will be created in the root of the debugfs filesystem.
240 *
241 * This function creates a directory in debugfs with the given name.
242 *
243 * This function will return a pointer to a dentry if it succeeds. This
244 * pointer must be passed to the debugfs_remove() function when the file is
245 * to be removed (no automatic cleanup happens if your module is unloaded,
246 * you are responsible here.) If an error occurs, NULL will be returned.
247 *
248 * If debugfs is not enabled in the kernel, the value -ENODEV will be
249 * returned. It is not wise to check for this value, but rather, check for
250 * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
251 * code.
252 */
253 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
254 {
255 return debugfs_create_file(name,
256 S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
257 parent, NULL, NULL);
258 }
259 EXPORT_SYMBOL_GPL(debugfs_create_dir);
260
261 /**
262 * debugfs_remove - removes a file or directory from the debugfs filesystem
263 *
264 * @dentry: a pointer to a the dentry of the file or directory to be
265 * removed.
266 *
267 * This function removes a file or directory in debugfs that was previously
268 * created with a call to another debugfs function (like
269 * debufs_create_file() or variants thereof.)
270 *
271 * This function is required to be called in order for the file to be
272 * removed, no automatic cleanup of files will happen when a module is
273 * removed, you are responsible here.
274 */
275 void debugfs_remove(struct dentry *dentry)
276 {
277 struct dentry *parent;
278
279 if (!dentry)
280 return;
281
282 parent = dentry->d_parent;
283 if (!parent || !parent->d_inode)
284 return;
285
286 down(&parent->d_inode->i_sem);
287 if (debugfs_positive(dentry)) {
288 if (dentry->d_inode) {
289 if (S_ISDIR(dentry->d_inode->i_mode))
290 simple_rmdir(parent->d_inode, dentry);
291 else
292 simple_unlink(parent->d_inode, dentry);
293 dput(dentry);
294 }
295 }
296 up(&parent->d_inode->i_sem);
297 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
298 }
299 EXPORT_SYMBOL_GPL(debugfs_remove);
300
301 static decl_subsys(debug, NULL, NULL);
302
303 static int __init debugfs_init(void)
304 {
305 int retval;
306
307 kset_set_kset_s(&debug_subsys, kernel_subsys);
308 retval = subsystem_register(&debug_subsys);
309 if (retval)
310 return retval;
311
312 retval = register_filesystem(&debug_fs_type);
313 if (retval)
314 subsystem_unregister(&debug_subsys);
315 return retval;
316 }
317
318 static void __exit debugfs_exit(void)
319 {
320 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
321 unregister_filesystem(&debug_fs_type);
322 subsystem_unregister(&debug_subsys);
323 }
324
325 core_initcall(debugfs_init);
326 module_exit(debugfs_exit);
327 MODULE_LICENSE("GPL");
328
329
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