fs/debugfs/inode.c

   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/module.h>
  20 #include <linux/fs.h>
  21 #include <linux/mount.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/init.h>
  24 #include <linux/kobject.h>
  25 #include <linux/namei.h>
  26 #include <linux/debugfs.h>
  27 #include <linux/fsnotify.h>
  28 #include <linux/string.h>
  29
  30 #define DEBUGFS_MAGIC   0x64626720
  31
  32 static struct vfsmount *debugfs_mount;
  33 static int debugfs_mount_count;
  34
  35 static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev)
  36 {
  37         struct inode *inode = new_inode(sb);
  38
  39         if (inode) {
  40                 inode->i_mode = mode;
  41                 inode->i_uid = 0;
  42                 inode->i_gid = 0;
  43                 inode->i_blocks = 0;
  44                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  45                 switch (mode & S_IFMT) {
  46                 default:
  47                         init_special_inode(inode, mode, dev);
  48                         break;
  49                 case S_IFREG:
  50                         inode->i_fop = &debugfs_file_operations;
  51                         break;
  52                 case S_IFLNK:
  53                         inode->i_op = &debugfs_link_operations;
  54                         break;
  55                 case S_IFDIR:
  56                         inode->i_op = &simple_dir_inode_operations;
  57                         inode->i_fop = &simple_dir_operations;
  58
  59                         /* directory inodes start off with i_nlink == 2
  60                          * (for "." entry) */
  61                         inc_nlink(inode);
  62                         break;
  63                 }
  64         }
  65         return inode;
  66 }
  67
  68 /* SMP-safe */
  69 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
  70                          int mode, dev_t dev)
  71 {
  72         struct inode *inode;
  73         int error = -EPERM;
  74
  75         if (dentry->d_inode)
  76                 return -EEXIST;
  77
  78         inode = debugfs_get_inode(dir->i_sb, mode, dev);
  79         if (inode) {
  80                 d_instantiate(dentry, inode);
  81                 dget(dentry);
  82                 error = 0;
  83         }
  84         return error;
  85 }
  86
  87 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
  88 {
  89         int res;
  90
  91         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  92         res = debugfs_mknod(dir, dentry, mode, 0);
  93         if (!res) {
  94                 inc_nlink(dir);
  95                 fsnotify_mkdir(dir, dentry);
  96         }
  97         return res;
  98 }
  99
 100 static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode)
 101 {
 102         mode = (mode & S_IALLUGO) | S_IFLNK;
 103         return debugfs_mknod(dir, dentry, mode, 0);
 104 }
 105
 106 static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode)
 107 {
 108         int res;
 109
 110         mode = (mode & S_IALLUGO) | S_IFREG;
 111         res = debugfs_mknod(dir, dentry, mode, 0);
 112         if (!res)
 113                 fsnotify_create(dir, dentry);
 114         return res;
 115 }
 116
 117 static inline int debugfs_positive(struct dentry *dentry)
 118 {
 119         return dentry->d_inode && !d_unhashed(dentry);
 120 }
 121
 122 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 123 {
 124         static struct tree_descr debug_files[] = {{""}};
 125
 126         return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 127 }
 128
 129 static int debug_get_sb(struct file_system_type *fs_type,
 130                         int flags, const char *dev_name,
 131                         void *data, struct vfsmount *mnt)
 132 {
 133         return get_sb_single(fs_type, flags, data, debug_fill_super, mnt);
 134 }
 135
 136 static struct file_system_type debug_fs_type = {
 137         .owner =        THIS_MODULE,
 138         .name =         "debugfs",
 139         .get_sb =       debug_get_sb,
 140         .kill_sb =      kill_litter_super,
 141 };
 142
 143 static int debugfs_create_by_name(const char *name, mode_t mode,
 144                                   struct dentry *parent,
 145                                   struct dentry **dentry)
 146 {
 147         int error = 0;
 148
 149         /* If the parent is not specified, we create it in the root.
 150          * We need the root dentry to do this, which is in the super
 151          * block. A pointer to that is in the struct vfsmount that we
 152          * have around.
 153          */
 154         if (!parent) {
 155                 if (debugfs_mount && debugfs_mount->mnt_sb) {
 156                         parent = debugfs_mount->mnt_sb->s_root;
 157                 }
 158         }
 159         if (!parent) {
 160                 pr_debug("debugfs: Ah! can not find a parent!\n");
 161                 return -EFAULT;
 162         }
 163
 164         *dentry = NULL;
 165         mutex_lock(&parent->d_inode->i_mutex);
 166         *dentry = lookup_one_len(name, parent, strlen(name));
 167         if (!IS_ERR(*dentry)) {
 168                 switch (mode & S_IFMT) {
 169                 case S_IFDIR:
 170                         error = debugfs_mkdir(parent->d_inode, *dentry, mode);
 171                         break;
 172                 case S_IFLNK:
 173                         error = debugfs_link(parent->d_inode, *dentry, mode);
 174                         break;
 175                 default:
 176                         error = debugfs_create(parent->d_inode, *dentry, mode);
 177                         break;
 178                 }
 179                 dput(*dentry);
 180         } else
 181                 error = PTR_ERR(*dentry);
 182         mutex_unlock(&parent->d_inode->i_mutex);
 183
 184         return error;
 185 }
 186
 187 /**
 188  * debugfs_create_file - create a file in the debugfs filesystem
 189  * @name: a pointer to a string containing the name of the file to create.
 190  * @mode: the permission that the file should have
 191  * @parent: a pointer to the parent dentry for this file.  This should be a
 192  *          directory dentry if set.  If this paramater is NULL, then the
 193  *          file will be created in the root of the debugfs filesystem.
 194  * @data: a pointer to something that the caller will want to get to later
 195  *        on.  The inode.i_private pointer will point to this value on
 196  *        the open() call.
 197  * @fops: a pointer to a struct file_operations that should be used for
 198  *        this file.
 199  *
 200  * This is the basic "create a file" function for debugfs.  It allows for a
 201  * wide range of flexibility in createing a file, or a directory (if you
 202  * want to create a directory, the debugfs_create_dir() function is
 203  * recommended to be used instead.)
 204  *
 205  * This function will return a pointer to a dentry if it succeeds.  This
 206  * pointer must be passed to the debugfs_remove() function when the file is
 207  * to be removed (no automatic cleanup happens if your module is unloaded,
 208  * you are responsible here.)  If an error occurs, %NULL will be returned.
 209  *
 210  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 211  * returned.
 212  */
 213 struct dentry *debugfs_create_file(const char *name, mode_t mode,
 214                                    struct dentry *parent, void *data,
 215                                    const struct file_operations *fops)
 216 {
 217         struct dentry *dentry = NULL;
 218         int error;
 219
 220         pr_debug("debugfs: creating file '%s'\n",name);
 221
 222         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 223                               &debugfs_mount_count);
 224         if (error)
 225                 goto exit;
 226
 227         error = debugfs_create_by_name(name, mode, parent, &dentry);
 228         if (error) {
 229                 dentry = NULL;
 230                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 231                 goto exit;
 232         }
 233
 234         if (dentry->d_inode) {
 235                 if (data)
 236                         dentry->d_inode->i_private = data;
 237                 if (fops)
 238                         dentry->d_inode->i_fop = fops;
 239         }
 240 exit:
 241         return dentry;
 242 }
 243 EXPORT_SYMBOL_GPL(debugfs_create_file);
 244
 245 /**
 246  * debugfs_create_dir - create a directory in the debugfs filesystem
 247  * @name: a pointer to a string containing the name of the directory to
 248  *        create.
 249  * @parent: a pointer to the parent dentry for this file.  This should be a
 250  *          directory dentry if set.  If this paramater is NULL, then the
 251  *          directory will be created in the root of the debugfs filesystem.
 252  *
 253  * This function creates a directory in debugfs with the given name.
 254  *
 255  * This function will return a pointer to a dentry if it succeeds.  This
 256  * pointer must be passed to the debugfs_remove() function when the file is
 257  * to be removed (no automatic cleanup happens if your module is unloaded,
 258  * you are responsible here.)  If an error occurs, %NULL will be returned.
 259  *
 260  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 261  * returned.
 262  */
 263 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 264 {
 265         return debugfs_create_file(name,
 266                                    S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 267                                    parent, NULL, NULL);
 268 }
 269 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 270
 271 /**
 272  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 273  * @name: a pointer to a string containing the name of the symbolic link to
 274  *        create.
 275  * @parent: a pointer to the parent dentry for this symbolic link.  This
 276  *          should be a directory dentry if set.  If this paramater is NULL,
 277  *          then the symbolic link will be created in the root of the debugfs
 278  *          filesystem.
 279  * @target: a pointer to a string containing the path to the target of the
 280  *          symbolic link.
 281  *
 282  * This function creates a symbolic link with the given name in debugfs that
 283  * links to the given target path.
 284  *
 285  * This function will return a pointer to a dentry if it succeeds.  This
 286  * pointer must be passed to the debugfs_remove() function when the symbolic
 287  * link is to be removed (no automatic cleanup happens if your module is
 288  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 289  * returned.
 290  *
 291  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 292  * returned.
 293  */
 294 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 295                                       const char *target)
 296 {
 297         struct dentry *result;
 298         char *link;
 299
 300         link = kstrdup(target, GFP_KERNEL);
 301         if (!link)
 302                 return NULL;
 303
 304         result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
 305                                      NULL);
 306         if (!result)
 307                 kfree(link);
 308         return result;
 309 }
 310 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 311
 312 /**
 313  * debugfs_remove - removes a file or directory from the debugfs filesystem
 314  * @dentry: a pointer to a the dentry of the file or directory to be
 315  *          removed.
 316  *
 317  * This function removes a file or directory in debugfs that was previously
 318  * created with a call to another debugfs function (like
 319  * debugfs_create_file() or variants thereof.)
 320  *
 321  * This function is required to be called in order for the file to be
 322  * removed, no automatic cleanup of files will happen when a module is
 323  * removed, you are responsible here.
 324  */
 325 void debugfs_remove(struct dentry *dentry)
 326 {
 327         struct dentry *parent;
 328         int ret = 0;
 329
 330         if (!dentry)
 331                 return;
 332
 333         parent = dentry->d_parent;
 334         if (!parent || !parent->d_inode)
 335                 return;
 336
 337         mutex_lock(&parent->d_inode->i_mutex);
 338         if (debugfs_positive(dentry)) {
 339                 if (dentry->d_inode) {
 340                         dget(dentry);
 341                         switch (dentry->d_inode->i_mode & S_IFMT) {
 342                         case S_IFDIR:
 343                                 ret = simple_rmdir(parent->d_inode, dentry);
 344                                 break;
 345                         case S_IFLNK:
 346                                 kfree(dentry->d_inode->i_private);
 347                                 /* fall through */
 348                         default:
 349                                 simple_unlink(parent->d_inode, dentry);
 350                                 break;
 351                         }
 352                         if (!ret)
 353                                 d_delete(dentry);
 354                         dput(dentry);
 355                 }
 356         }
 357         mutex_unlock(&parent->d_inode->i_mutex);
 358         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 359 }
 360 EXPORT_SYMBOL_GPL(debugfs_remove);
 361
 362 /**
 363  * debugfs_rename - rename a file/directory in the debugfs filesystem
 364  * @old_dir: a pointer to the parent dentry for the renamed object. This
 365  *          should be a directory dentry.
 366  * @old_dentry: dentry of an object to be renamed.
 367  * @new_dir: a pointer to the parent dentry where the object should be
 368  *          moved. This should be a directory dentry.
 369  * @new_name: a pointer to a string containing the target name.
 370  *
 371  * This function renames a file/directory in debugfs.  The target must not
 372  * exist for rename to succeed.
 373  *
 374  * This function will return a pointer to old_dentry (which is updated to
 375  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 376  * returned.
 377  *
 378  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 379  * returned.
 380  */
 381 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 382                 struct dentry *new_dir, const char *new_name)
 383 {
 384         int error;
 385         struct dentry *dentry = NULL, *trap;
 386         const char *old_name;
 387
 388         trap = lock_rename(new_dir, old_dir);
 389         /* Source or destination directories don't exist? */
 390         if (!old_dir->d_inode || !new_dir->d_inode)
 391                 goto exit;
 392         /* Source does not exist, cyclic rename, or mountpoint? */
 393         if (!old_dentry->d_inode || old_dentry == trap ||
 394             d_mountpoint(old_dentry))
 395                 goto exit;
 396         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 397         /* Lookup failed, cyclic rename or target exists? */
 398         if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
 399                 goto exit;
 400
 401         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
 402
 403         error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
 404                 dentry);
 405         if (error) {
 406                 fsnotify_oldname_free(old_name);
 407                 goto exit;
 408         }
 409         d_move(old_dentry, dentry);
 410         fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
 411                 old_dentry->d_name.name, S_ISDIR(old_dentry->d_inode->i_mode),
 412                 NULL, old_dentry);
 413         fsnotify_oldname_free(old_name);
 414         unlock_rename(new_dir, old_dir);
 415         dput(dentry);
 416         return old_dentry;
 417 exit:
 418         if (dentry && !IS_ERR(dentry))
 419                 dput(dentry);
 420         unlock_rename(new_dir, old_dir);
 421         return NULL;
 422 }
 423 EXPORT_SYMBOL_GPL(debugfs_rename);
 424
 425 static struct kobject *debug_kobj;
 426
 427 static int __init debugfs_init(void)
 428 {
 429         int retval;
 430
 431         debug_kobj = kobject_create_and_add("debug", kernel_kobj);
 432         if (!debug_kobj)
 433                 return -EINVAL;
 434
 435         retval = register_filesystem(&debug_fs_type);
 436         if (retval)
 437                 kobject_put(debug_kobj);
 438         return retval;
 439 }
 440
 441 static void __exit debugfs_exit(void)
 442 {
 443         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 444         unregister_filesystem(&debug_fs_type);
 445         kobject_put(debug_kobj);
 446 }
 447
 448 core_initcall(debugfs_init);
 449 module_exit(debugfs_exit);
 450 MODULE_LICENSE("GPL");
 451