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 static bool debugfs_registered;
  34
  35 static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev,
  36                                        void *data, const struct file_operations *fops)
  37
  38 {
  39         struct inode *inode = new_inode(sb);
  40
  41         if (inode) {
  42                 inode->i_mode = mode;
  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 = fops ? fops : &debugfs_file_operations;
  50                         inode->i_private = data;
  51                         break;
  52                 case S_IFLNK:
  53                         inode->i_op = &debugfs_link_operations;
  54                         inode->i_fop = fops;
  55                         inode->i_private = data;
  56                         break;
  57                 case S_IFDIR:
  58                         inode->i_op = &simple_dir_inode_operations;
  59                         inode->i_fop = fops ? fops : &simple_dir_operations;
  60                         inode->i_private = data;
  61
  62                         /* directory inodes start off with i_nlink == 2
  63                          * (for "." entry) */
  64                         inc_nlink(inode);
  65                         break;
  66                 }
  67         }
  68         return inode;
  69 }
  70
  71 /* SMP-safe */
  72 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
  73                          int mode, dev_t dev, void *data,
  74                          const struct file_operations *fops)
  75 {
  76         struct inode *inode;
  77         int error = -EPERM;
  78
  79         if (dentry->d_inode)
  80                 return -EEXIST;
  81
  82         inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops);
  83         if (inode) {
  84                 d_instantiate(dentry, inode);
  85                 dget(dentry);
  86                 error = 0;
  87         }
  88         return error;
  89 }
  90
  91 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode,
  92                          void *data, const struct file_operations *fops)
  93 {
  94         int res;
  95
  96         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  97         res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
  98         if (!res) {
  99                 inc_nlink(dir);
 100                 fsnotify_mkdir(dir, dentry);
 101         }
 102         return res;
 103 }
 104
 105 static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode,
 106                         void *data, const struct file_operations *fops)
 107 {
 108         mode = (mode & S_IALLUGO) | S_IFLNK;
 109         return debugfs_mknod(dir, dentry, mode, 0, data, fops);
 110 }
 111
 112 static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode,
 113                           void *data, const struct file_operations *fops)
 114 {
 115         int res;
 116
 117         mode = (mode & S_IALLUGO) | S_IFREG;
 118         res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
 119         if (!res)
 120                 fsnotify_create(dir, dentry);
 121         return res;
 122 }
 123
 124 static inline int debugfs_positive(struct dentry *dentry)
 125 {
 126         return dentry->d_inode && !d_unhashed(dentry);
 127 }
 128
 129 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 130 {
 131         static struct tree_descr debug_files[] = {{""}};
 132
 133         return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 134 }
 135
 136 static int debug_get_sb(struct file_system_type *fs_type,
 137                         int flags, const char *dev_name,
 138                         void *data, struct vfsmount *mnt)
 139 {
 140         return get_sb_single(fs_type, flags, data, debug_fill_super, mnt);
 141 }
 142
 143 static struct file_system_type debug_fs_type = {
 144         .owner =        THIS_MODULE,
 145         .name =         "debugfs",
 146         .get_sb =       debug_get_sb,
 147         .kill_sb =      kill_litter_super,
 148 };
 149
 150 static int debugfs_create_by_name(const char *name, mode_t mode,
 151                                   struct dentry *parent,
 152                                   struct dentry **dentry,
 153                                   void *data,
 154                                   const struct file_operations *fops)
 155 {
 156         int error = 0;
 157
 158         /* If the parent is not specified, we create it in the root.
 159          * We need the root dentry to do this, which is in the super
 160          * block. A pointer to that is in the struct vfsmount that we
 161          * have around.
 162          */
 163         if (!parent) {
 164                 if (debugfs_mount && debugfs_mount->mnt_sb) {
 165                         parent = debugfs_mount->mnt_sb->s_root;
 166                 }
 167         }
 168         if (!parent) {
 169                 pr_debug("debugfs: Ah! can not find a parent!\n");
 170                 return -EFAULT;
 171         }
 172
 173         *dentry = NULL;
 174         mutex_lock(&parent->d_inode->i_mutex);
 175         *dentry = lookup_one_len(name, parent, strlen(name));
 176         if (!IS_ERR(*dentry)) {
 177                 switch (mode & S_IFMT) {
 178                 case S_IFDIR:
 179                         error = debugfs_mkdir(parent->d_inode, *dentry, mode,
 180                                               data, fops);
 181                         break;
 182                 case S_IFLNK:
 183                         error = debugfs_link(parent->d_inode, *dentry, mode,
 184                                              data, fops);
 185                         break;
 186                 default:
 187                         error = debugfs_create(parent->d_inode, *dentry, mode,
 188                                                data, fops);
 189                         break;
 190                 }
 191                 dput(*dentry);
 192         } else
 193                 error = PTR_ERR(*dentry);
 194         mutex_unlock(&parent->d_inode->i_mutex);
 195
 196         return error;
 197 }
 198
 199 /**
 200  * debugfs_create_file - create a file in the debugfs filesystem
 201  * @name: a pointer to a string containing the name of the file to create.
 202  * @mode: the permission that the file should have.
 203  * @parent: a pointer to the parent dentry for this file.  This should be a
 204  *          directory dentry if set.  If this paramater is NULL, then the
 205  *          file will be created in the root of the debugfs filesystem.
 206  * @data: a pointer to something that the caller will want to get to later
 207  *        on.  The inode.i_private pointer will point to this value on
 208  *        the open() call.
 209  * @fops: a pointer to a struct file_operations that should be used for
 210  *        this file.
 211  *
 212  * This is the basic "create a file" function for debugfs.  It allows for a
 213  * wide range of flexibility in creating a file, or a directory (if you want
 214  * to create a directory, the debugfs_create_dir() function is
 215  * recommended to be used instead.)
 216  *
 217  * This function will return a pointer to a dentry if it succeeds.  This
 218  * pointer must be passed to the debugfs_remove() function when the file is
 219  * to be removed (no automatic cleanup happens if your module is unloaded,
 220  * you are responsible here.)  If an error occurs, %NULL will be returned.
 221  *
 222  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 223  * returned.
 224  */
 225 struct dentry *debugfs_create_file(const char *name, mode_t mode,
 226                                    struct dentry *parent, void *data,
 227                                    const struct file_operations *fops)
 228 {
 229         struct dentry *dentry = NULL;
 230         int error;
 231
 232         pr_debug("debugfs: creating file '%s'\n",name);
 233
 234         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 235                               &debugfs_mount_count);
 236         if (error)
 237                 goto exit;
 238
 239         error = debugfs_create_by_name(name, mode, parent, &dentry,
 240                                        data, fops);
 241         if (error) {
 242                 dentry = NULL;
 243                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 244                 goto exit;
 245         }
 246 exit:
 247         return dentry;
 248 }
 249 EXPORT_SYMBOL_GPL(debugfs_create_file);
 250
 251 /**
 252  * debugfs_create_dir - create a directory in the debugfs filesystem
 253  * @name: a pointer to a string containing the name of the directory to
 254  *        create.
 255  * @parent: a pointer to the parent dentry for this file.  This should be a
 256  *          directory dentry if set.  If this paramater is NULL, then the
 257  *          directory will be created in the root of the debugfs filesystem.
 258  *
 259  * This function creates a directory in debugfs with the given name.
 260  *
 261  * This function will return a pointer to a dentry if it succeeds.  This
 262  * pointer must be passed to the debugfs_remove() function when the file is
 263  * to be removed (no automatic cleanup happens if your module is unloaded,
 264  * you are responsible here.)  If an error occurs, %NULL will be returned.
 265  *
 266  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 267  * returned.
 268  */
 269 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 270 {
 271         return debugfs_create_file(name,
 272                                    S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 273                                    parent, NULL, NULL);
 274 }
 275 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 276
 277 /**
 278  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 279  * @name: a pointer to a string containing the name of the symbolic link to
 280  *        create.
 281  * @parent: a pointer to the parent dentry for this symbolic link.  This
 282  *          should be a directory dentry if set.  If this paramater is NULL,
 283  *          then the symbolic link will be created in the root of the debugfs
 284  *          filesystem.
 285  * @target: a pointer to a string containing the path to the target of the
 286  *          symbolic link.
 287  *
 288  * This function creates a symbolic link with the given name in debugfs that
 289  * links to the given target path.
 290  *
 291  * This function will return a pointer to a dentry if it succeeds.  This
 292  * pointer must be passed to the debugfs_remove() function when the symbolic
 293  * link is to be removed (no automatic cleanup happens if your module is
 294  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 295  * returned.
 296  *
 297  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 298  * returned.
 299  */
 300 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 301                                       const char *target)
 302 {
 303         struct dentry *result;
 304         char *link;
 305
 306         link = kstrdup(target, GFP_KERNEL);
 307         if (!link)
 308                 return NULL;
 309
 310         result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
 311                                      NULL);
 312         if (!result)
 313                 kfree(link);
 314         return result;
 315 }
 316 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 317
 318 static void __debugfs_remove(struct dentry *dentry, struct dentry *parent)
 319 {
 320         int ret = 0;
 321
 322         if (debugfs_positive(dentry)) {
 323                 if (dentry->d_inode) {
 324                         dget(dentry);
 325                         switch (dentry->d_inode->i_mode & S_IFMT) {
 326                         case S_IFDIR:
 327                                 ret = simple_rmdir(parent->d_inode, dentry);
 328                                 break;
 329                         case S_IFLNK:
 330                                 kfree(dentry->d_inode->i_private);
 331                                 /* fall through */
 332                         default:
 333                                 simple_unlink(parent->d_inode, dentry);
 334                                 break;
 335                         }
 336                         if (!ret)
 337                                 d_delete(dentry);
 338                         dput(dentry);
 339                 }
 340         }
 341 }
 342
 343 /**
 344  * debugfs_remove - removes a file or directory from the debugfs filesystem
 345  * @dentry: a pointer to a the dentry of the file or directory to be
 346  *          removed.
 347  *
 348  * This function removes a file or directory in debugfs that was previously
 349  * created with a call to another debugfs function (like
 350  * debugfs_create_file() or variants thereof.)
 351  *
 352  * This function is required to be called in order for the file to be
 353  * removed, no automatic cleanup of files will happen when a module is
 354  * removed, you are responsible here.
 355  */
 356 void debugfs_remove(struct dentry *dentry)
 357 {
 358         struct dentry *parent;
 359
 360         if (!dentry)
 361                 return;
 362
 363         parent = dentry->d_parent;
 364         if (!parent || !parent->d_inode)
 365                 return;
 366
 367         mutex_lock(&parent->d_inode->i_mutex);
 368         __debugfs_remove(dentry, parent);
 369         mutex_unlock(&parent->d_inode->i_mutex);
 370         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 371 }
 372 EXPORT_SYMBOL_GPL(debugfs_remove);
 373
 374 /**
 375  * debugfs_remove_recursive - recursively removes a directory
 376  * @dentry: a pointer to a the dentry of the directory to be removed.
 377  *
 378  * This function recursively removes a directory tree in debugfs that
 379  * was previously created with a call to another debugfs function
 380  * (like debugfs_create_file() or variants thereof.)
 381  *
 382  * This function is required to be called in order for the file to be
 383  * removed, no automatic cleanup of files will happen when a module is
 384  * removed, you are responsible here.
 385  */
 386 void debugfs_remove_recursive(struct dentry *dentry)
 387 {
 388         struct dentry *child;
 389         struct dentry *parent;
 390
 391         if (!dentry)
 392                 return;
 393
 394         parent = dentry->d_parent;
 395         if (!parent || !parent->d_inode)
 396                 return;
 397
 398         parent = dentry;
 399         mutex_lock(&parent->d_inode->i_mutex);
 400
 401         while (1) {
 402                 /*
 403                  * When all dentries under "parent" has been removed,
 404                  * walk up the tree until we reach our starting point.
 405                  */
 406                 if (list_empty(&parent->d_subdirs)) {
 407                         mutex_unlock(&parent->d_inode->i_mutex);
 408                         if (parent == dentry)
 409                                 break;
 410                         parent = parent->d_parent;
 411                         mutex_lock(&parent->d_inode->i_mutex);
 412                 }
 413                 child = list_entry(parent->d_subdirs.next, struct dentry,
 414                                 d_u.d_child);
 415  next_sibling:
 416
 417                 /*
 418                  * If "child" isn't empty, walk down the tree and
 419                  * remove all its descendants first.
 420                  */
 421                 if (!list_empty(&child->d_subdirs)) {
 422                         mutex_unlock(&parent->d_inode->i_mutex);
 423                         parent = child;
 424                         mutex_lock(&parent->d_inode->i_mutex);
 425                         continue;
 426                 }
 427                 __debugfs_remove(child, parent);
 428                 if (parent->d_subdirs.next == &child->d_u.d_child) {
 429                         /*
 430                          * Try the next sibling.
 431                          */
 432                         if (child->d_u.d_child.next != &parent->d_subdirs) {
 433                                 child = list_entry(child->d_u.d_child.next,
 434                                                    struct dentry,
 435                                                    d_u.d_child);
 436                                 goto next_sibling;
 437                         }
 438
 439                         /*
 440                          * Avoid infinite loop if we fail to remove
 441                          * one dentry.
 442                          */
 443                         mutex_unlock(&parent->d_inode->i_mutex);
 444                         break;
 445                 }
 446                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 447         }
 448
 449         parent = dentry->d_parent;
 450         mutex_lock(&parent->d_inode->i_mutex);
 451         __debugfs_remove(dentry, parent);
 452         mutex_unlock(&parent->d_inode->i_mutex);
 453         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 454 }
 455 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
 456
 457 /**
 458  * debugfs_rename - rename a file/directory in the debugfs filesystem
 459  * @old_dir: a pointer to the parent dentry for the renamed object. This
 460  *          should be a directory dentry.
 461  * @old_dentry: dentry of an object to be renamed.
 462  * @new_dir: a pointer to the parent dentry where the object should be
 463  *          moved. This should be a directory dentry.
 464  * @new_name: a pointer to a string containing the target name.
 465  *
 466  * This function renames a file/directory in debugfs.  The target must not
 467  * exist for rename to succeed.
 468  *
 469  * This function will return a pointer to old_dentry (which is updated to
 470  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 471  * returned.
 472  *
 473  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 474  * returned.
 475  */
 476 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 477                 struct dentry *new_dir, const char *new_name)
 478 {
 479         int error;
 480         struct dentry *dentry = NULL, *trap;
 481         const char *old_name;
 482
 483         trap = lock_rename(new_dir, old_dir);
 484         /* Source or destination directories don't exist? */
 485         if (!old_dir->d_inode || !new_dir->d_inode)
 486                 goto exit;
 487         /* Source does not exist, cyclic rename, or mountpoint? */
 488         if (!old_dentry->d_inode || old_dentry == trap ||
 489             d_mountpoint(old_dentry))
 490                 goto exit;
 491         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 492         /* Lookup failed, cyclic rename or target exists? */
 493         if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
 494                 goto exit;
 495
 496         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
 497
 498         error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
 499                 dentry);
 500         if (error) {
 501                 fsnotify_oldname_free(old_name);
 502                 goto exit;
 503         }
 504         d_move(old_dentry, dentry);
 505         fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
 506                 old_dentry->d_name.name, S_ISDIR(old_dentry->d_inode->i_mode),
 507                 NULL, old_dentry);
 508         fsnotify_oldname_free(old_name);
 509         unlock_rename(new_dir, old_dir);
 510         dput(dentry);
 511         return old_dentry;
 512 exit:
 513         if (dentry && !IS_ERR(dentry))
 514                 dput(dentry);
 515         unlock_rename(new_dir, old_dir);
 516         return NULL;
 517 }
 518 EXPORT_SYMBOL_GPL(debugfs_rename);
 519
 520 /**
 521  * debugfs_initialized - Tells whether debugfs has been registered
 522  */
 523 bool debugfs_initialized(void)
 524 {
 525         return debugfs_registered;
 526 }
 527 EXPORT_SYMBOL_GPL(debugfs_initialized);
 528
 529
 530 static struct kobject *debug_kobj;
 531
 532 static int __init debugfs_init(void)
 533 {
 534         int retval;
 535
 536         debug_kobj = kobject_create_and_add("debug", kernel_kobj);
 537         if (!debug_kobj)
 538                 return -EINVAL;
 539
 540         retval = register_filesystem(&debug_fs_type);
 541         if (retval)
 542                 kobject_put(debug_kobj);
 543         else
 544                 debugfs_registered = true;
 545
 546         return retval;
 547 }
 548
 549 static void __exit debugfs_exit(void)
 550 {
 551         debugfs_registered = false;
 552
 553         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 554         unregister_filesystem(&debug_fs_type);
 555         kobject_put(debug_kobj);
 556 }
 557
 558 core_initcall(debugfs_init);
 559 module_exit(debugfs_exit);
 560 MODULE_LICENSE("GPL");
 561