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_uid = 0;
  41                 inode->i_gid = 0;
  42                 inode->i_blocks = 0;
  43                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  44                 switch (mode & S_IFMT) {
  45                 default:
  46                         init_special_inode(inode, mode, dev);
  47                         break;
  48                 case S_IFREG:
  49                         inode->i_fop = &debugfs_file_operations;
  50                         break;
  51                 case S_IFLNK:
  52                         inode->i_op = &debugfs_link_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
  59                          * (for "." entry) */
  60                         inc_nlink(inode);
  61                         break;
  62                 }
  63         }
  64         return inode;
  65 }
  66
  67 /* SMP-safe */
  68 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
  69                          int mode, dev_t dev)
  70 {
  71         struct inode *inode;
  72         int error = -EPERM;
  73
  74         if (dentry->d_inode)
  75                 return -EEXIST;
  76
  77         inode = debugfs_get_inode(dir->i_sb, mode, dev);
  78         if (inode) {
  79                 d_instantiate(dentry, inode);
  80                 dget(dentry);
  81                 error = 0;
  82         }
  83         return error;
  84 }
  85
  86 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
  87 {
  88         int res;
  89
  90         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  91         res = debugfs_mknod(dir, dentry, mode, 0);
  92         if (!res) {
  93                 inc_nlink(dir);
  94                 fsnotify_mkdir(dir, dentry);
  95         }
  96         return res;
  97 }
  98
  99 static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode)
 100 {
 101         mode = (mode & S_IALLUGO) | S_IFLNK;
 102         return debugfs_mknod(dir, dentry, mode, 0);
 103 }
 104
 105 static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode)
 106 {
 107         int res;
 108
 109         mode = (mode & S_IALLUGO) | S_IFREG;
 110         res = debugfs_mknod(dir, dentry, mode, 0);
 111         if (!res)
 112                 fsnotify_create(dir, dentry);
 113         return res;
 114 }
 115
 116 static inline int debugfs_positive(struct dentry *dentry)
 117 {
 118         return dentry->d_inode && !d_unhashed(dentry);
 119 }
 120
 121 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 122 {
 123         static struct tree_descr debug_files[] = {{""}};
 124
 125         return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 126 }
 127
 128 static int debug_get_sb(struct file_system_type *fs_type,
 129                         int flags, const char *dev_name,
 130                         void *data, struct vfsmount *mnt)
 131 {
 132         return get_sb_single(fs_type, flags, data, debug_fill_super, mnt);
 133 }
 134
 135 static struct file_system_type debug_fs_type = {
 136         .owner =        THIS_MODULE,
 137         .name =         "debugfs",
 138         .get_sb =       debug_get_sb,
 139         .kill_sb =      kill_litter_super,
 140 };
 141
 142 static int debugfs_create_by_name(const char *name, mode_t mode,
 143                                   struct dentry *parent,
 144                                   struct dentry **dentry)
 145 {
 146         int error = 0;
 147
 148         /* If the parent is not specified, we create it in the root.
 149          * We need the root dentry to do this, which is in the super
 150          * block. A pointer to that is in the struct vfsmount that we
 151          * have around.
 152          */
 153         if (!parent) {
 154                 if (debugfs_mount && debugfs_mount->mnt_sb) {
 155                         parent = debugfs_mount->mnt_sb->s_root;
 156                 }
 157         }
 158         if (!parent) {
 159                 pr_debug("debugfs: Ah! can not find a parent!\n");
 160                 return -EFAULT;
 161         }
 162
 163         *dentry = NULL;
 164         mutex_lock(&parent->d_inode->i_mutex);
 165         *dentry = lookup_one_len(name, parent, strlen(name));
 166         if (!IS_ERR(*dentry)) {
 167                 switch (mode & S_IFMT) {
 168                 case S_IFDIR:
 169                         error = debugfs_mkdir(parent->d_inode, *dentry, mode);
 170                         break;
 171                 case S_IFLNK:
 172                         error = debugfs_link(parent->d_inode, *dentry, mode);
 173                         break;
 174                 default:
 175                         error = debugfs_create(parent->d_inode, *dentry, mode);
 176                         break;
 177                 }
 178                 dput(*dentry);
 179         } else
 180                 error = PTR_ERR(*dentry);
 181         mutex_unlock(&parent->d_inode->i_mutex);
 182
 183         return error;
 184 }
 185
 186 /**
 187  * debugfs_create_file - create a file in the debugfs filesystem
 188  * @name: a pointer to a string containing the name of the file to create.
 189  * @mode: the permission that the file should have
 190  * @parent: a pointer to the parent dentry for this file.  This should be a
 191  *          directory dentry if set.  If this paramater is NULL, then the
 192  *          file will be created in the root of the debugfs filesystem.
 193  * @data: a pointer to something that the caller will want to get to later
 194  *        on.  The inode.i_private pointer will point to this value on
 195  *        the open() call.
 196  * @fops: a pointer to a struct file_operations that should be used for
 197  *        this file.
 198  *
 199  * This is the basic "create a file" function for debugfs.  It allows for a
 200  * wide range of flexibility in createing a file, or a directory (if you
 201  * want to create a directory, the debugfs_create_dir() function is
 202  * recommended to be used instead.)
 203  *
 204  * This function will return a pointer to a dentry if it succeeds.  This
 205  * pointer must be passed to the debugfs_remove() function when the file is
 206  * to be removed (no automatic cleanup happens if your module is unloaded,
 207  * you are responsible here.)  If an error occurs, %NULL will be returned.
 208  *
 209  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 210  * returned.
 211  */
 212 struct dentry *debugfs_create_file(const char *name, mode_t mode,
 213                                    struct dentry *parent, void *data,
 214                                    const struct file_operations *fops)
 215 {
 216         struct dentry *dentry = NULL;
 217         int error;
 218
 219         pr_debug("debugfs: creating file '%s'\n",name);
 220
 221         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 222                               &debugfs_mount_count);
 223         if (error)
 224                 goto exit;
 225
 226         error = debugfs_create_by_name(name, mode, parent, &dentry);
 227         if (error) {
 228                 dentry = NULL;
 229                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 230                 goto exit;
 231         }
 232
 233         if (dentry->d_inode) {
 234                 if (data)
 235                         dentry->d_inode->i_private = data;
 236                 if (fops)
 237                         dentry->d_inode->i_fop = fops;
 238         }
 239 exit:
 240         return dentry;
 241 }
 242 EXPORT_SYMBOL_GPL(debugfs_create_file);
 243
 244 /**
 245  * debugfs_create_dir - create a directory in the debugfs filesystem
 246  * @name: a pointer to a string containing the name of the directory to
 247  *        create.
 248  * @parent: a pointer to the parent dentry for this file.  This should be a
 249  *          directory dentry if set.  If this paramater is NULL, then the
 250  *          directory will be created in the root of the debugfs filesystem.
 251  *
 252  * This function creates a directory in debugfs with the given name.
 253  *
 254  * This function will return a pointer to a dentry if it succeeds.  This
 255  * pointer must be passed to the debugfs_remove() function when the file is
 256  * to be removed (no automatic cleanup happens if your module is unloaded,
 257  * you are responsible here.)  If an error occurs, %NULL will be returned.
 258  *
 259  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 260  * returned.
 261  */
 262 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 263 {
 264         return debugfs_create_file(name,
 265                                    S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 266                                    parent, NULL, NULL);
 267 }
 268 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 269
 270 /**
 271  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 272  * @name: a pointer to a string containing the name of the symbolic link to
 273  *        create.
 274  * @parent: a pointer to the parent dentry for this symbolic link.  This
 275  *          should be a directory dentry if set.  If this paramater is NULL,
 276  *          then the symbolic link will be created in the root of the debugfs
 277  *          filesystem.
 278  * @target: a pointer to a string containing the path to the target of the
 279  *          symbolic link.
 280  *
 281  * This function creates a symbolic link with the given name in debugfs that
 282  * links to the given target path.
 283  *
 284  * This function will return a pointer to a dentry if it succeeds.  This
 285  * pointer must be passed to the debugfs_remove() function when the symbolic
 286  * link is to be removed (no automatic cleanup happens if your module is
 287  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 288  * returned.
 289  *
 290  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 291  * returned.
 292  */
 293 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 294                                       const char *target)
 295 {
 296         struct dentry *result;
 297         char *link;
 298
 299         link = kstrdup(target, GFP_KERNEL);
 300         if (!link)
 301                 return NULL;
 302
 303         result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
 304                                      NULL);
 305         if (!result)
 306                 kfree(link);
 307         return result;
 308 }
 309 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 310
 311 static void __debugfs_remove(struct dentry *dentry, struct dentry *parent)
 312 {
 313         int ret = 0;
 314
 315         if (debugfs_positive(dentry)) {
 316                 if (dentry->d_inode) {
 317                         dget(dentry);
 318                         switch (dentry->d_inode->i_mode & S_IFMT) {
 319                         case S_IFDIR:
 320                                 ret = simple_rmdir(parent->d_inode, dentry);
 321                                 break;
 322                         case S_IFLNK:
 323                                 kfree(dentry->d_inode->i_private);
 324                                 /* fall through */
 325                         default:
 326                                 simple_unlink(parent->d_inode, dentry);
 327                                 break;
 328                         }
 329                         if (!ret)
 330                                 d_delete(dentry);
 331                         dput(dentry);
 332                 }
 333         }
 334 }
 335
 336 /**
 337  * debugfs_remove - removes a file or directory from the debugfs filesystem
 338  * @dentry: a pointer to a the dentry of the file or directory to be
 339  *          removed.
 340  *
 341  * This function removes a file or directory in debugfs that was previously
 342  * created with a call to another debugfs function (like
 343  * debugfs_create_file() or variants thereof.)
 344  *
 345  * This function is required to be called in order for the file to be
 346  * removed, no automatic cleanup of files will happen when a module is
 347  * removed, you are responsible here.
 348  */
 349 void debugfs_remove(struct dentry *dentry)
 350 {
 351         struct dentry *parent;
 352
 353         if (!dentry)
 354                 return;
 355
 356         parent = dentry->d_parent;
 357         if (!parent || !parent->d_inode)
 358                 return;
 359
 360         mutex_lock(&parent->d_inode->i_mutex);
 361         __debugfs_remove(dentry, parent);
 362         mutex_unlock(&parent->d_inode->i_mutex);
 363         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 364 }
 365 EXPORT_SYMBOL_GPL(debugfs_remove);
 366
 367 /**
 368  * debugfs_remove_recursive - recursively removes a directory
 369  * @dentry: a pointer to a the dentry of the directory to be removed.
 370  *
 371  * This function recursively removes a directory tree in debugfs that
 372  * was previously created with a call to another debugfs function
 373  * (like debugfs_create_file() or variants thereof.)
 374  *
 375  * This function is required to be called in order for the file to be
 376  * removed, no automatic cleanup of files will happen when a module is
 377  * removed, you are responsible here.
 378  */
 379 void debugfs_remove_recursive(struct dentry *dentry)
 380 {
 381         struct dentry *child;
 382         struct dentry *parent;
 383
 384         if (!dentry)
 385                 return;
 386
 387         parent = dentry->d_parent;
 388         if (!parent || !parent->d_inode)
 389                 return;
 390
 391         parent = dentry;
 392         mutex_lock(&parent->d_inode->i_mutex);
 393
 394         while (1) {
 395                 /*
 396                  * When all dentries under "parent" has been removed,
 397                  * walk up the tree until we reach our starting point.
 398                  */
 399                 if (list_empty(&parent->d_subdirs)) {
 400                         mutex_unlock(&parent->d_inode->i_mutex);
 401                         if (parent == dentry)
 402                                 break;
 403                         parent = parent->d_parent;
 404                         mutex_lock(&parent->d_inode->i_mutex);
 405                 }
 406                 child = list_entry(parent->d_subdirs.next, struct dentry,
 407                                 d_u.d_child);
 408
 409                 /*
 410                  * If "child" isn't empty, walk down the tree and
 411                  * remove all its descendants first.
 412                  */
 413                 if (!list_empty(&child->d_subdirs)) {
 414                         mutex_unlock(&parent->d_inode->i_mutex);
 415                         parent = child;
 416                         mutex_lock(&parent->d_inode->i_mutex);
 417                         continue;
 418                 }
 419                 __debugfs_remove(child, parent);
 420                 if (parent->d_subdirs.next == &child->d_u.d_child) {
 421                         /*
 422                          * Avoid infinite loop if we fail to remove
 423                          * one dentry.
 424                          */
 425                         mutex_unlock(&parent->d_inode->i_mutex);
 426                         break;
 427                 }
 428                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 429         }
 430
 431         parent = dentry->d_parent;
 432         mutex_lock(&parent->d_inode->i_mutex);
 433         __debugfs_remove(dentry, parent);
 434         mutex_unlock(&parent->d_inode->i_mutex);
 435         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 436 }
 437 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
 438
 439 /**
 440  * debugfs_rename - rename a file/directory in the debugfs filesystem
 441  * @old_dir: a pointer to the parent dentry for the renamed object. This
 442  *          should be a directory dentry.
 443  * @old_dentry: dentry of an object to be renamed.
 444  * @new_dir: a pointer to the parent dentry where the object should be
 445  *          moved. This should be a directory dentry.
 446  * @new_name: a pointer to a string containing the target name.
 447  *
 448  * This function renames a file/directory in debugfs.  The target must not
 449  * exist for rename to succeed.
 450  *
 451  * This function will return a pointer to old_dentry (which is updated to
 452  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 453  * returned.
 454  *
 455  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 456  * returned.
 457  */
 458 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 459                 struct dentry *new_dir, const char *new_name)
 460 {
 461         int error;
 462         struct dentry *dentry = NULL, *trap;
 463         const char *old_name;
 464
 465         trap = lock_rename(new_dir, old_dir);
 466         /* Source or destination directories don't exist? */
 467         if (!old_dir->d_inode || !new_dir->d_inode)
 468                 goto exit;
 469         /* Source does not exist, cyclic rename, or mountpoint? */
 470         if (!old_dentry->d_inode || old_dentry == trap ||
 471             d_mountpoint(old_dentry))
 472                 goto exit;
 473         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 474         /* Lookup failed, cyclic rename or target exists? */
 475         if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
 476                 goto exit;
 477
 478         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
 479
 480         error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
 481                 dentry);
 482         if (error) {
 483                 fsnotify_oldname_free(old_name);
 484                 goto exit;
 485         }
 486         d_move(old_dentry, dentry);
 487         fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
 488                 old_dentry->d_name.name, S_ISDIR(old_dentry->d_inode->i_mode),
 489                 NULL, old_dentry);
 490         fsnotify_oldname_free(old_name);
 491         unlock_rename(new_dir, old_dir);
 492         dput(dentry);
 493         return old_dentry;
 494 exit:
 495         if (dentry && !IS_ERR(dentry))
 496                 dput(dentry);
 497         unlock_rename(new_dir, old_dir);
 498         return NULL;
 499 }
 500 EXPORT_SYMBOL_GPL(debugfs_rename);
 501
 502 static struct kobject *debug_kobj;
 503
 504 static int __init debugfs_init(void)
 505 {
 506         int retval;
 507
 508         debug_kobj = kobject_create_and_add("debug", kernel_kobj);
 509         if (!debug_kobj)
 510                 return -EINVAL;
 511
 512         retval = register_filesystem(&debug_fs_type);
 513         if (retval)
 514                 kobject_put(debug_kobj);
 515         return retval;
 516 }
 517
 518 static void __exit debugfs_exit(void)
 519 {
 520         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 521         unregister_filesystem(&debug_fs_type);
 522         kobject_put(debug_kobj);
 523 }
 524
 525 core_initcall(debugfs_init);
 526 module_exit(debugfs_exit);
 527 MODULE_LICENSE("GPL");
 528