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 #include <linux/magic.h>
  30
  31 static struct vfsmount *debugfs_mount;
  32 static int debugfs_mount_count;
  33
  34 static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev)
  35 {
  36         struct inode *inode = new_inode(sb);
  37
  38         if (inode) {
  39                 inode->i_mode = mode;
  40                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  41                 switch (mode & S_IFMT) {
  42                 default:
  43                         init_special_inode(inode, mode, dev);
  44                         break;
  45                 case S_IFREG:
  46                         inode->i_fop = &debugfs_file_operations;
  47                         break;
  48                 case S_IFLNK:
  49                         inode->i_op = &debugfs_link_operations;
  50                         break;
  51                 case S_IFDIR:
  52                         inode->i_op = &simple_dir_inode_operations;
  53                         inode->i_fop = &simple_dir_operations;
  54
  55                         /* directory inodes start off with i_nlink == 2
  56                          * (for "." entry) */
  57                         inc_nlink(inode);
  58                         break;
  59                 }
  60         }
  61         return inode;
  62 }
  63
  64 /* SMP-safe */
  65 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
  66                          int mode, dev_t dev)
  67 {
  68         struct inode *inode;
  69         int error = -EPERM;
  70
  71         if (dentry->d_inode)
  72                 return -EEXIST;
  73
  74         inode = debugfs_get_inode(dir->i_sb, mode, dev);
  75         if (inode) {
  76                 d_instantiate(dentry, inode);
  77                 dget(dentry);
  78                 error = 0;
  79         }
  80         return error;
  81 }
  82
  83 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
  84 {
  85         int res;
  86
  87         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  88         res = debugfs_mknod(dir, dentry, mode, 0);
  89         if (!res) {
  90                 inc_nlink(dir);
  91                 fsnotify_mkdir(dir, dentry);
  92         }
  93         return res;
  94 }
  95
  96 static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode)
  97 {
  98         mode = (mode & S_IALLUGO) | S_IFLNK;
  99         return debugfs_mknod(dir, dentry, mode, 0);
 100 }
 101
 102 static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode)
 103 {
 104         int res;
 105
 106         mode = (mode & S_IALLUGO) | S_IFREG;
 107         res = debugfs_mknod(dir, dentry, mode, 0);
 108         if (!res)
 109                 fsnotify_create(dir, dentry);
 110         return res;
 111 }
 112
 113 static inline int debugfs_positive(struct dentry *dentry)
 114 {
 115         return dentry->d_inode && !d_unhashed(dentry);
 116 }
 117
 118 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 119 {
 120         static struct tree_descr debug_files[] = {{""}};
 121
 122         return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 123 }
 124
 125 static int debug_get_sb(struct file_system_type *fs_type,
 126                         int flags, const char *dev_name,
 127                         void *data, struct vfsmount *mnt)
 128 {
 129         return get_sb_single(fs_type, flags, data, debug_fill_super, mnt);
 130 }
 131
 132 static struct file_system_type debug_fs_type = {
 133         .owner =        THIS_MODULE,
 134         .name =         "debugfs",
 135         .get_sb =       debug_get_sb,
 136         .kill_sb =      kill_litter_super,
 137 };
 138
 139 static int debugfs_create_by_name(const char *name, mode_t mode,
 140                                   struct dentry *parent,
 141                                   struct dentry **dentry)
 142 {
 143         int error = 0;
 144
 145         /* If the parent is not specified, we create it in the root.
 146          * We need the root dentry to do this, which is in the super
 147          * block. A pointer to that is in the struct vfsmount that we
 148          * have around.
 149          */
 150         if (!parent) {
 151                 if (debugfs_mount && debugfs_mount->mnt_sb) {
 152                         parent = debugfs_mount->mnt_sb->s_root;
 153                 }
 154         }
 155         if (!parent) {
 156                 pr_debug("debugfs: Ah! can not find a parent!\n");
 157                 return -EFAULT;
 158         }
 159
 160         *dentry = NULL;
 161         mutex_lock(&parent->d_inode->i_mutex);
 162         *dentry = lookup_one_len(name, parent, strlen(name));
 163         if (!IS_ERR(*dentry)) {
 164                 switch (mode & S_IFMT) {
 165                 case S_IFDIR:
 166                         error = debugfs_mkdir(parent->d_inode, *dentry, mode);
 167                         break;
 168                 case S_IFLNK:
 169                         error = debugfs_link(parent->d_inode, *dentry, mode);
 170                         break;
 171                 default:
 172                         error = debugfs_create(parent->d_inode, *dentry, mode);
 173                         break;
 174                 }
 175                 dput(*dentry);
 176         } else
 177                 error = PTR_ERR(*dentry);
 178         mutex_unlock(&parent->d_inode->i_mutex);
 179
 180         return error;
 181 }
 182
 183 /**
 184  * debugfs_create_file - create a file in the debugfs filesystem
 185  * @name: a pointer to a string containing the name of the file to create.
 186  * @mode: the permission that the file should have
 187  * @parent: a pointer to the parent dentry for this file.  This should be a
 188  *          directory dentry if set.  If this paramater is NULL, then the
 189  *          file will be created in the root of the debugfs filesystem.
 190  * @data: a pointer to something that the caller will want to get to later
 191  *        on.  The inode.i_private pointer will point to this value on
 192  *        the open() call.
 193  * @fops: a pointer to a struct file_operations that should be used for
 194  *        this file.
 195  *
 196  * This is the basic "create a file" function for debugfs.  It allows for a
 197  * wide range of flexibility in createing a file, or a directory (if you
 198  * want to create a directory, the debugfs_create_dir() function is
 199  * recommended to be used instead.)
 200  *
 201  * This function will return a pointer to a dentry if it succeeds.  This
 202  * pointer must be passed to the debugfs_remove() function when the file is
 203  * to be removed (no automatic cleanup happens if your module is unloaded,
 204  * you are responsible here.)  If an error occurs, %NULL will be returned.
 205  *
 206  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 207  * returned.
 208  */
 209 struct dentry *debugfs_create_file(const char *name, mode_t mode,
 210                                    struct dentry *parent, void *data,
 211                                    const struct file_operations *fops)
 212 {
 213         struct dentry *dentry = NULL;
 214         int error;
 215
 216         pr_debug("debugfs: creating file '%s'\n",name);
 217
 218         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 219                               &debugfs_mount_count);
 220         if (error)
 221                 goto exit;
 222
 223         error = debugfs_create_by_name(name, mode, parent, &dentry);
 224         if (error) {
 225                 dentry = NULL;
 226                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 227                 goto exit;
 228         }
 229
 230         if (dentry->d_inode) {
 231                 if (data)
 232                         dentry->d_inode->i_private = data;
 233                 if (fops)
 234                         dentry->d_inode->i_fop = fops;
 235         }
 236 exit:
 237         return dentry;
 238 }
 239 EXPORT_SYMBOL_GPL(debugfs_create_file);
 240
 241 /**
 242  * debugfs_create_dir - create a directory in the debugfs filesystem
 243  * @name: a pointer to a string containing the name of the directory to
 244  *        create.
 245  * @parent: a pointer to the parent dentry for this file.  This should be a
 246  *          directory dentry if set.  If this paramater is NULL, then the
 247  *          directory will be created in the root of the debugfs filesystem.
 248  *
 249  * This function creates a directory in debugfs with the given name.
 250  *
 251  * This function will return a pointer to a dentry if it succeeds.  This
 252  * pointer must be passed to the debugfs_remove() function when the file is
 253  * to be removed (no automatic cleanup happens if your module is unloaded,
 254  * you are responsible here.)  If an error occurs, %NULL will be returned.
 255  *
 256  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 257  * returned.
 258  */
 259 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 260 {
 261         return debugfs_create_file(name,
 262                                    S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 263                                    parent, NULL, NULL);
 264 }
 265 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 266
 267 /**
 268  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 269  * @name: a pointer to a string containing the name of the symbolic link to
 270  *        create.
 271  * @parent: a pointer to the parent dentry for this symbolic link.  This
 272  *          should be a directory dentry if set.  If this paramater is NULL,
 273  *          then the symbolic link will be created in the root of the debugfs
 274  *          filesystem.
 275  * @target: a pointer to a string containing the path to the target of the
 276  *          symbolic link.
 277  *
 278  * This function creates a symbolic link with the given name in debugfs that
 279  * links to the given target path.
 280  *
 281  * This function will return a pointer to a dentry if it succeeds.  This
 282  * pointer must be passed to the debugfs_remove() function when the symbolic
 283  * link is to be removed (no automatic cleanup happens if your module is
 284  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 285  * returned.
 286  *
 287  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 288  * returned.
 289  */
 290 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 291                                       const char *target)
 292 {
 293         struct dentry *result;
 294         char *link;
 295
 296         link = kstrdup(target, GFP_KERNEL);
 297         if (!link)
 298                 return NULL;
 299
 300         result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
 301                                      NULL);
 302         if (!result)
 303                 kfree(link);
 304         return result;
 305 }
 306 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 307
 308 static void __debugfs_remove(struct dentry *dentry, struct dentry *parent)
 309 {
 310         int ret = 0;
 311
 312         if (debugfs_positive(dentry)) {
 313                 if (dentry->d_inode) {
 314                         dget(dentry);
 315                         switch (dentry->d_inode->i_mode & S_IFMT) {
 316                         case S_IFDIR:
 317                                 ret = simple_rmdir(parent->d_inode, dentry);
 318                                 break;
 319                         case S_IFLNK:
 320                                 kfree(dentry->d_inode->i_private);
 321                                 /* fall through */
 322                         default:
 323                                 simple_unlink(parent->d_inode, dentry);
 324                                 break;
 325                         }
 326                         if (!ret)
 327                                 d_delete(dentry);
 328                         dput(dentry);
 329                 }
 330         }
 331 }
 332
 333 /**
 334  * debugfs_remove - removes a file or directory from the debugfs filesystem
 335  * @dentry: a pointer to a the dentry of the file or directory to be
 336  *          removed.
 337  *
 338  * This function removes a file or directory in debugfs that was previously
 339  * created with a call to another debugfs function (like
 340  * debugfs_create_file() or variants thereof.)
 341  *
 342  * This function is required to be called in order for the file to be
 343  * removed, no automatic cleanup of files will happen when a module is
 344  * removed, you are responsible here.
 345  */
 346 void debugfs_remove(struct dentry *dentry)
 347 {
 348         struct dentry *parent;
 349
 350         if (!dentry)
 351                 return;
 352
 353         parent = dentry->d_parent;
 354         if (!parent || !parent->d_inode)
 355                 return;
 356
 357         mutex_lock(&parent->d_inode->i_mutex);
 358         __debugfs_remove(dentry, parent);
 359         mutex_unlock(&parent->d_inode->i_mutex);
 360         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 361 }
 362 EXPORT_SYMBOL_GPL(debugfs_remove);
 363
 364 /**
 365  * debugfs_remove_recursive - recursively removes a directory
 366  * @dentry: a pointer to a the dentry of the directory to be removed.
 367  *
 368  * This function recursively removes a directory tree in debugfs that
 369  * was previously created with a call to another debugfs function
 370  * (like debugfs_create_file() or variants thereof.)
 371  *
 372  * This function is required to be called in order for the file to be
 373  * removed, no automatic cleanup of files will happen when a module is
 374  * removed, you are responsible here.
 375  */
 376 void debugfs_remove_recursive(struct dentry *dentry)
 377 {
 378         struct dentry *child;
 379         struct dentry *parent;
 380
 381         if (!dentry)
 382                 return;
 383
 384         parent = dentry->d_parent;
 385         if (!parent || !parent->d_inode)
 386                 return;
 387
 388         parent = dentry;
 389         mutex_lock(&parent->d_inode->i_mutex);
 390
 391         while (1) {
 392                 /*
 393                  * When all dentries under "parent" has been removed,
 394                  * walk up the tree until we reach our starting point.
 395                  */
 396                 if (list_empty(&parent->d_subdirs)) {
 397                         mutex_unlock(&parent->d_inode->i_mutex);
 398                         if (parent == dentry)
 399                                 break;
 400                         parent = parent->d_parent;
 401                         mutex_lock(&parent->d_inode->i_mutex);
 402                 }
 403                 child = list_entry(parent->d_subdirs.next, struct dentry,
 404                                 d_u.d_child);
 405
 406                 /*
 407                  * If "child" isn't empty, walk down the tree and
 408                  * remove all its descendants first.
 409                  */
 410                 if (!list_empty(&child->d_subdirs)) {
 411                         mutex_unlock(&parent->d_inode->i_mutex);
 412                         parent = child;
 413                         mutex_lock(&parent->d_inode->i_mutex);
 414                         continue;
 415                 }
 416                 __debugfs_remove(child, parent);
 417                 if (parent->d_subdirs.next == &child->d_u.d_child) {
 418                         /*
 419                          * Avoid infinite loop if we fail to remove
 420                          * one dentry.
 421                          */
 422                         mutex_unlock(&parent->d_inode->i_mutex);
 423                         break;
 424                 }
 425                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 426         }
 427
 428         parent = dentry->d_parent;
 429         mutex_lock(&parent->d_inode->i_mutex);
 430         __debugfs_remove(dentry, parent);
 431         mutex_unlock(&parent->d_inode->i_mutex);
 432         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 433 }
 434 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
 435
 436 /**
 437  * debugfs_rename - rename a file/directory in the debugfs filesystem
 438  * @old_dir: a pointer to the parent dentry for the renamed object. This
 439  *          should be a directory dentry.
 440  * @old_dentry: dentry of an object to be renamed.
 441  * @new_dir: a pointer to the parent dentry where the object should be
 442  *          moved. This should be a directory dentry.
 443  * @new_name: a pointer to a string containing the target name.
 444  *
 445  * This function renames a file/directory in debugfs.  The target must not
 446  * exist for rename to succeed.
 447  *
 448  * This function will return a pointer to old_dentry (which is updated to
 449  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 450  * returned.
 451  *
 452  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 453  * returned.
 454  */
 455 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 456                 struct dentry *new_dir, const char *new_name)
 457 {
 458         int error;
 459         struct dentry *dentry = NULL, *trap;
 460         const char *old_name;
 461
 462         trap = lock_rename(new_dir, old_dir);
 463         /* Source or destination directories don't exist? */
 464         if (!old_dir->d_inode || !new_dir->d_inode)
 465                 goto exit;
 466         /* Source does not exist, cyclic rename, or mountpoint? */
 467         if (!old_dentry->d_inode || old_dentry == trap ||
 468             d_mountpoint(old_dentry))
 469                 goto exit;
 470         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 471         /* Lookup failed, cyclic rename or target exists? */
 472         if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
 473                 goto exit;
 474
 475         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
 476
 477         error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
 478                 dentry);
 479         if (error) {
 480                 fsnotify_oldname_free(old_name);
 481                 goto exit;
 482         }
 483         d_move(old_dentry, dentry);
 484         fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
 485                 old_dentry->d_name.name, S_ISDIR(old_dentry->d_inode->i_mode),
 486                 NULL, old_dentry);
 487         fsnotify_oldname_free(old_name);
 488         unlock_rename(new_dir, old_dir);
 489         dput(dentry);
 490         return old_dentry;
 491 exit:
 492         if (dentry && !IS_ERR(dentry))
 493                 dput(dentry);
 494         unlock_rename(new_dir, old_dir);
 495         return NULL;
 496 }
 497 EXPORT_SYMBOL_GPL(debugfs_rename);
 498
 499 static struct kobject *debug_kobj;
 500
 501 static int __init debugfs_init(void)
 502 {
 503         int retval;
 504
 505         debug_kobj = kobject_create_and_add("debug", kernel_kobj);
 506         if (!debug_kobj)
 507                 return -EINVAL;
 508
 509         retval = register_filesystem(&debug_fs_type);
 510         if (retval)
 511                 kobject_put(debug_kobj);
 512         return retval;
 513 }
 514
 515 static void __exit debugfs_exit(void)
 516 {
 517         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 518         unregister_filesystem(&debug_fs_type);
 519         kobject_put(debug_kobj);
 520 }
 521
 522 core_initcall(debugfs_init);
 523 module_exit(debugfs_exit);
 524 MODULE_LICENSE("GPL");
 525