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