fs/debugfs/inode.c

   1 /*
   2  *  inode.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 #include <linux/module.h>
  17 #include <linux/fs.h>
  18 #include <linux/mount.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/init.h>
  21 #include <linux/kobject.h>
  22 #include <linux/namei.h>
  23 #include <linux/debugfs.h>
  24 #include <linux/fsnotify.h>
  25 #include <linux/string.h>
  26 #include <linux/seq_file.h>
  27 #include <linux/parser.h>
  28 #include <linux/magic.h>
  29 #include <linux/slab.h>
  30
  31 #define DEBUGFS_DEFAULT_MODE    0755
  32
  33 static struct vfsmount *debugfs_mount;
  34 static int debugfs_mount_count;
  35 static bool debugfs_registered;
  36
  37 static struct inode *debugfs_get_inode(struct super_block *sb, umode_t mode, dev_t dev,
  38                                        void *data, const struct file_operations *fops)
  39
  40 {
  41         struct inode *inode = new_inode(sb);
  42
  43         if (inode) {
  44                 inode->i_ino = get_next_ino();
  45                 inode->i_mode = mode;
  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 = fops ? fops : &debugfs_file_operations;
  53                         inode->i_private = data;
  54                         break;
  55                 case S_IFLNK:
  56                         inode->i_op = &debugfs_link_operations;
  57                         inode->i_fop = fops;
  58                         inode->i_private = data;
  59                         break;
  60                 case S_IFDIR:
  61                         inode->i_op = &simple_dir_inode_operations;
  62                         inode->i_fop = fops ? fops : &simple_dir_operations;
  63                         inode->i_private = data;
  64
  65                         /* directory inodes start off with i_nlink == 2
  66                          * (for "." entry) */
  67                         inc_nlink(inode);
  68                         break;
  69                 }
  70         }
  71         return inode;
  72 }
  73
  74 /* SMP-safe */
  75 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
  76                          umode_t mode, dev_t dev, void *data,
  77                          const struct file_operations *fops)
  78 {
  79         struct inode *inode;
  80         int error = -EPERM;
  81
  82         if (dentry->d_inode)
  83                 return -EEXIST;
  84
  85         inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops);
  86         if (inode) {
  87                 d_instantiate(dentry, inode);
  88                 dget(dentry);
  89                 error = 0;
  90         }
  91         return error;
  92 }
  93
  94 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode,
  95                          void *data, const struct file_operations *fops)
  96 {
  97         int res;
  98
  99         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
 100         res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
 101         if (!res) {
 102                 inc_nlink(dir);
 103                 fsnotify_mkdir(dir, dentry);
 104         }
 105         return res;
 106 }
 107
 108 static int debugfs_link(struct inode *dir, struct dentry *dentry, umode_t mode,
 109                         void *data, const struct file_operations *fops)
 110 {
 111         mode = (mode & S_IALLUGO) | S_IFLNK;
 112         return debugfs_mknod(dir, dentry, mode, 0, data, fops);
 113 }
 114
 115 static int debugfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 116                           void *data, const struct file_operations *fops)
 117 {
 118         int res;
 119
 120         mode = (mode & S_IALLUGO) | S_IFREG;
 121         res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
 122         if (!res)
 123                 fsnotify_create(dir, dentry);
 124         return res;
 125 }
 126
 127 static inline int debugfs_positive(struct dentry *dentry)
 128 {
 129         return dentry->d_inode && !d_unhashed(dentry);
 130 }
 131
 132 struct debugfs_mount_opts {
 133         uid_t uid;
 134         gid_t gid;
 135         umode_t mode;
 136 };
 137
 138 enum {
 139         Opt_uid,
 140         Opt_gid,
 141         Opt_mode,
 142         Opt_err
 143 };
 144
 145 static const match_table_t tokens = {
 146         {Opt_uid, "uid=%u"},
 147         {Opt_gid, "gid=%u"},
 148         {Opt_mode, "mode=%o"},
 149         {Opt_err, NULL}
 150 };
 151
 152 struct debugfs_fs_info {
 153         struct debugfs_mount_opts mount_opts;
 154 };
 155
 156 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
 157 {
 158         substring_t args[MAX_OPT_ARGS];
 159         int option;
 160         int token;
 161         char *p;
 162
 163         opts->mode = DEBUGFS_DEFAULT_MODE;
 164
 165         while ((p = strsep(&data, ",")) != NULL) {
 166                 if (!*p)
 167                         continue;
 168
 169                 token = match_token(p, tokens, args);
 170                 switch (token) {
 171                 case Opt_uid:
 172                         if (match_int(&args[0], &option))
 173                                 return -EINVAL;
 174                         opts->uid = option;
 175                         break;
 176                 case Opt_gid:
 177                         if (match_octal(&args[0], &option))
 178                                 return -EINVAL;
 179                         opts->gid = option;
 180                         break;
 181                 case Opt_mode:
 182                         if (match_octal(&args[0], &option))
 183                                 return -EINVAL;
 184                         opts->mode = option & S_IALLUGO;
 185                         break;
 186                 /*
 187                  * We might like to report bad mount options here;
 188                  * but traditionally debugfs has ignored all mount options
 189                  */
 190                 }
 191         }
 192
 193         return 0;
 194 }
 195
 196 static int debugfs_apply_options(struct super_block *sb)
 197 {
 198         struct debugfs_fs_info *fsi = sb->s_fs_info;
 199         struct inode *inode = sb->s_root->d_inode;
 200         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 201
 202         inode->i_mode &= ~S_IALLUGO;
 203         inode->i_mode |= opts->mode;
 204
 205         inode->i_uid = opts->uid;
 206         inode->i_gid = opts->gid;
 207
 208         return 0;
 209 }
 210
 211 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
 212 {
 213         int err;
 214         struct debugfs_fs_info *fsi = sb->s_fs_info;
 215
 216         err = debugfs_parse_options(data, &fsi->mount_opts);
 217         if (err)
 218                 goto fail;
 219
 220         debugfs_apply_options(sb);
 221
 222 fail:
 223         return err;
 224 }
 225
 226 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
 227 {
 228         struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
 229         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 230
 231         if (opts->uid != 0)
 232                 seq_printf(m, ",uid=%u", opts->uid);
 233         if (opts->gid != 0)
 234                 seq_printf(m, ",gid=%u", opts->gid);
 235         if (opts->mode != DEBUGFS_DEFAULT_MODE)
 236                 seq_printf(m, ",mode=%o", opts->mode);
 237
 238         return 0;
 239 }
 240
 241 static const struct super_operations debugfs_super_operations = {
 242         .statfs         = simple_statfs,
 243         .remount_fs     = debugfs_remount,
 244         .show_options   = debugfs_show_options,
 245 };
 246
 247 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 248 {
 249         static struct tree_descr debug_files[] = {{""}};
 250         struct debugfs_fs_info *fsi;
 251         int err;
 252
 253         save_mount_options(sb, data);
 254
 255         fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
 256         sb->s_fs_info = fsi;
 257         if (!fsi) {
 258                 err = -ENOMEM;
 259                 goto fail;
 260         }
 261
 262         err = debugfs_parse_options(data, &fsi->mount_opts);
 263         if (err)
 264                 goto fail;
 265
 266         err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 267         if (err)
 268                 goto fail;
 269
 270         sb->s_op = &debugfs_super_operations;
 271
 272         debugfs_apply_options(sb);
 273
 274         return 0;
 275
 276 fail:
 277         kfree(fsi);
 278         sb->s_fs_info = NULL;
 279         return err;
 280 }
 281
 282 static struct dentry *debug_mount(struct file_system_type *fs_type,
 283                         int flags, const char *dev_name,
 284                         void *data)
 285 {
 286         return mount_single(fs_type, flags, data, debug_fill_super);
 287 }
 288
 289 static struct file_system_type debug_fs_type = {
 290         .owner =        THIS_MODULE,
 291         .name =         "debugfs",
 292         .mount =        debug_mount,
 293         .kill_sb =      kill_litter_super,
 294 };
 295
 296 static int debugfs_create_by_name(const char *name, umode_t mode,
 297                                   struct dentry *parent,
 298                                   struct dentry **dentry,
 299                                   void *data,
 300                                   const struct file_operations *fops)
 301 {
 302         int error = 0;
 303
 304         /* If the parent is not specified, we create it in the root.
 305          * We need the root dentry to do this, which is in the super
 306          * block. A pointer to that is in the struct vfsmount that we
 307          * have around.
 308          */
 309         if (!parent)
 310                 parent = debugfs_mount->mnt_root;
 311
 312         *dentry = NULL;
 313         mutex_lock(&parent->d_inode->i_mutex);
 314         *dentry = lookup_one_len(name, parent, strlen(name));
 315         if (!IS_ERR(*dentry)) {
 316                 switch (mode & S_IFMT) {
 317                 case S_IFDIR:
 318                         error = debugfs_mkdir(parent->d_inode, *dentry, mode,
 319                                               data, fops);
 320                         break;
 321                 case S_IFLNK:
 322                         error = debugfs_link(parent->d_inode, *dentry, mode,
 323                                              data, fops);
 324                         break;
 325                 default:
 326                         error = debugfs_create(parent->d_inode, *dentry, mode,
 327                                                data, fops);
 328                         break;
 329                 }
 330                 dput(*dentry);
 331         } else
 332                 error = PTR_ERR(*dentry);
 333         mutex_unlock(&parent->d_inode->i_mutex);
 334
 335         return error;
 336 }
 337
 338 /**
 339  * debugfs_create_file - create a file in the debugfs filesystem
 340  * @name: a pointer to a string containing the name of the file to create.
 341  * @mode: the permission that the file should have.
 342  * @parent: a pointer to the parent dentry for this file.  This should be a
 343  *          directory dentry if set.  If this paramater is NULL, then the
 344  *          file will be created in the root of the debugfs filesystem.
 345  * @data: a pointer to something that the caller will want to get to later
 346  *        on.  The inode.i_private pointer will point to this value on
 347  *        the open() call.
 348  * @fops: a pointer to a struct file_operations that should be used for
 349  *        this file.
 350  *
 351  * This is the basic "create a file" function for debugfs.  It allows for a
 352  * wide range of flexibility in creating a file, or a directory (if you want
 353  * to create a directory, the debugfs_create_dir() function is
 354  * recommended to be used instead.)
 355  *
 356  * This function will return a pointer to a dentry if it succeeds.  This
 357  * pointer must be passed to the debugfs_remove() function when the file is
 358  * to be removed (no automatic cleanup happens if your module is unloaded,
 359  * you are responsible here.)  If an error occurs, %NULL will be returned.
 360  *
 361  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 362  * returned.
 363  */
 364 struct dentry *debugfs_create_file(const char *name, umode_t mode,
 365                                    struct dentry *parent, void *data,
 366                                    const struct file_operations *fops)
 367 {
 368         struct dentry *dentry = NULL;
 369         int error;
 370
 371         pr_debug("debugfs: creating file '%s'\n",name);
 372
 373         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 374                               &debugfs_mount_count);
 375         if (error)
 376                 goto exit;
 377
 378         error = debugfs_create_by_name(name, mode, parent, &dentry,
 379                                        data, fops);
 380         if (error) {
 381                 dentry = NULL;
 382                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 383                 goto exit;
 384         }
 385 exit:
 386         return dentry;
 387 }
 388 EXPORT_SYMBOL_GPL(debugfs_create_file);
 389
 390 /**
 391  * debugfs_create_dir - create a directory in the debugfs filesystem
 392  * @name: a pointer to a string containing the name of the directory to
 393  *        create.
 394  * @parent: a pointer to the parent dentry for this file.  This should be a
 395  *          directory dentry if set.  If this paramater is NULL, then the
 396  *          directory will be created in the root of the debugfs filesystem.
 397  *
 398  * This function creates a directory in debugfs with the given name.
 399  *
 400  * This function will return a pointer to a dentry if it succeeds.  This
 401  * pointer must be passed to the debugfs_remove() function when the file is
 402  * to be removed (no automatic cleanup happens if your module is unloaded,
 403  * you are responsible here.)  If an error occurs, %NULL will be returned.
 404  *
 405  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 406  * returned.
 407  */
 408 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 409 {
 410         return debugfs_create_file(name,
 411                                    S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 412                                    parent, NULL, NULL);
 413 }
 414 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 415
 416 /**
 417  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 418  * @name: a pointer to a string containing the name of the symbolic link to
 419  *        create.
 420  * @parent: a pointer to the parent dentry for this symbolic link.  This
 421  *          should be a directory dentry if set.  If this paramater is NULL,
 422  *          then the symbolic link will be created in the root of the debugfs
 423  *          filesystem.
 424  * @target: a pointer to a string containing the path to the target of the
 425  *          symbolic link.
 426  *
 427  * This function creates a symbolic link with the given name in debugfs that
 428  * links to the given target path.
 429  *
 430  * This function will return a pointer to a dentry if it succeeds.  This
 431  * pointer must be passed to the debugfs_remove() function when the symbolic
 432  * link is to be removed (no automatic cleanup happens if your module is
 433  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 434  * returned.
 435  *
 436  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 437  * returned.
 438  */
 439 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 440                                       const char *target)
 441 {
 442         struct dentry *result;
 443         char *link;
 444
 445         link = kstrdup(target, GFP_KERNEL);
 446         if (!link)
 447                 return NULL;
 448
 449         result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
 450                                      NULL);
 451         if (!result)
 452                 kfree(link);
 453         return result;
 454 }
 455 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 456
 457 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
 458 {
 459         int ret = 0;
 460
 461         if (debugfs_positive(dentry)) {
 462                 if (dentry->d_inode) {
 463                         dget(dentry);
 464                         switch (dentry->d_inode->i_mode & S_IFMT) {
 465                         case S_IFDIR:
 466                                 ret = simple_rmdir(parent->d_inode, dentry);
 467                                 break;
 468                         case S_IFLNK:
 469                                 kfree(dentry->d_inode->i_private);
 470                                 /* fall through */
 471                         default:
 472                                 simple_unlink(parent->d_inode, dentry);
 473                                 break;
 474                         }
 475                         if (!ret)
 476                                 d_delete(dentry);
 477                         dput(dentry);
 478                 }
 479         }
 480         return ret;
 481 }
 482
 483 /**
 484  * debugfs_remove - removes a file or directory from the debugfs filesystem
 485  * @dentry: a pointer to a the dentry of the file or directory to be
 486  *          removed.
 487  *
 488  * This function removes a file or directory in debugfs that was previously
 489  * created with a call to another debugfs function (like
 490  * debugfs_create_file() or variants thereof.)
 491  *
 492  * This function is required to be called in order for the file to be
 493  * removed, no automatic cleanup of files will happen when a module is
 494  * removed, you are responsible here.
 495  */
 496 void debugfs_remove(struct dentry *dentry)
 497 {
 498         struct dentry *parent;
 499         int ret;
 500
 501         if (!dentry)
 502                 return;
 503
 504         parent = dentry->d_parent;
 505         if (!parent || !parent->d_inode)
 506                 return;
 507
 508         mutex_lock(&parent->d_inode->i_mutex);
 509         ret = __debugfs_remove(dentry, parent);
 510         mutex_unlock(&parent->d_inode->i_mutex);
 511         if (!ret)
 512                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 513 }
 514 EXPORT_SYMBOL_GPL(debugfs_remove);
 515
 516 /**
 517  * debugfs_remove_recursive - recursively removes a directory
 518  * @dentry: a pointer to a the dentry of the directory to be removed.
 519  *
 520  * This function recursively removes a directory tree in debugfs that
 521  * was previously created with a call to another debugfs function
 522  * (like debugfs_create_file() or variants thereof.)
 523  *
 524  * This function is required to be called in order for the file to be
 525  * removed, no automatic cleanup of files will happen when a module is
 526  * removed, you are responsible here.
 527  */
 528 void debugfs_remove_recursive(struct dentry *dentry)
 529 {
 530         struct dentry *child;
 531         struct dentry *parent;
 532
 533         if (!dentry)
 534                 return;
 535
 536         parent = dentry->d_parent;
 537         if (!parent || !parent->d_inode)
 538                 return;
 539
 540         parent = dentry;
 541         mutex_lock(&parent->d_inode->i_mutex);
 542
 543         while (1) {
 544                 /*
 545                  * When all dentries under "parent" has been removed,
 546                  * walk up the tree until we reach our starting point.
 547                  */
 548                 if (list_empty(&parent->d_subdirs)) {
 549                         mutex_unlock(&parent->d_inode->i_mutex);
 550                         if (parent == dentry)
 551                                 break;
 552                         parent = parent->d_parent;
 553                         mutex_lock(&parent->d_inode->i_mutex);
 554                 }
 555                 child = list_entry(parent->d_subdirs.next, struct dentry,
 556                                 d_u.d_child);
 557  next_sibling:
 558
 559                 /*
 560                  * If "child" isn't empty, walk down the tree and
 561                  * remove all its descendants first.
 562                  */
 563                 if (!list_empty(&child->d_subdirs)) {
 564                         mutex_unlock(&parent->d_inode->i_mutex);
 565                         parent = child;
 566                         mutex_lock(&parent->d_inode->i_mutex);
 567                         continue;
 568                 }
 569                 __debugfs_remove(child, parent);
 570                 if (parent->d_subdirs.next == &child->d_u.d_child) {
 571                         /*
 572                          * Try the next sibling.
 573                          */
 574                         if (child->d_u.d_child.next != &parent->d_subdirs) {
 575                                 child = list_entry(child->d_u.d_child.next,
 576                                                    struct dentry,
 577                                                    d_u.d_child);
 578                                 goto next_sibling;
 579                         }
 580
 581                         /*
 582                          * Avoid infinite loop if we fail to remove
 583                          * one dentry.
 584                          */
 585                         mutex_unlock(&parent->d_inode->i_mutex);
 586                         break;
 587                 }
 588                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 589         }
 590
 591         parent = dentry->d_parent;
 592         mutex_lock(&parent->d_inode->i_mutex);
 593         __debugfs_remove(dentry, parent);
 594         mutex_unlock(&parent->d_inode->i_mutex);
 595         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 596 }
 597 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
 598
 599 /**
 600  * debugfs_rename - rename a file/directory in the debugfs filesystem
 601  * @old_dir: a pointer to the parent dentry for the renamed object. This
 602  *          should be a directory dentry.
 603  * @old_dentry: dentry of an object to be renamed.
 604  * @new_dir: a pointer to the parent dentry where the object should be
 605  *          moved. This should be a directory dentry.
 606  * @new_name: a pointer to a string containing the target name.
 607  *
 608  * This function renames a file/directory in debugfs.  The target must not
 609  * exist for rename to succeed.
 610  *
 611  * This function will return a pointer to old_dentry (which is updated to
 612  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 613  * returned.
 614  *
 615  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 616  * returned.
 617  */
 618 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 619                 struct dentry *new_dir, const char *new_name)
 620 {
 621         int error;
 622         struct dentry *dentry = NULL, *trap;
 623         const char *old_name;
 624
 625         trap = lock_rename(new_dir, old_dir);
 626         /* Source or destination directories don't exist? */
 627         if (!old_dir->d_inode || !new_dir->d_inode)
 628                 goto exit;
 629         /* Source does not exist, cyclic rename, or mountpoint? */
 630         if (!old_dentry->d_inode || old_dentry == trap ||
 631             d_mountpoint(old_dentry))
 632                 goto exit;
 633         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 634         /* Lookup failed, cyclic rename or target exists? */
 635         if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
 636                 goto exit;
 637
 638         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
 639
 640         error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
 641                 dentry);
 642         if (error) {
 643                 fsnotify_oldname_free(old_name);
 644                 goto exit;
 645         }
 646         d_move(old_dentry, dentry);
 647         fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
 648                 S_ISDIR(old_dentry->d_inode->i_mode),
 649                 NULL, old_dentry);
 650         fsnotify_oldname_free(old_name);
 651         unlock_rename(new_dir, old_dir);
 652         dput(dentry);
 653         return old_dentry;
 654 exit:
 655         if (dentry && !IS_ERR(dentry))
 656                 dput(dentry);
 657         unlock_rename(new_dir, old_dir);
 658         return NULL;
 659 }
 660 EXPORT_SYMBOL_GPL(debugfs_rename);
 661
 662 /**
 663  * debugfs_initialized - Tells whether debugfs has been registered
 664  */
 665 bool debugfs_initialized(void)
 666 {
 667         return debugfs_registered;
 668 }
 669 EXPORT_SYMBOL_GPL(debugfs_initialized);
 670
 671
 672 static struct kobject *debug_kobj;
 673
 674 static int __init debugfs_init(void)
 675 {
 676         int retval;
 677
 678         debug_kobj = kobject_create_and_add("debug", kernel_kobj);
 679         if (!debug_kobj)
 680                 return -EINVAL;
 681
 682         retval = register_filesystem(&debug_fs_type);
 683         if (retval)
 684                 kobject_put(debug_kobj);
 685         else
 686                 debugfs_registered = true;
 687
 688         return retval;
 689 }
 690 core_initcall(debugfs_init);
 691