/* * Squashfs - a compressed read only filesystem for Linux * * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 * Phillip Lougher <phillip@squashfs.org.uk> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2, * or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. * * dir.c */ /* * This file implements code to read directories from disk. * * See namei.c for a description of directory organisation on disk. */ #include <linux/fs.h> #include <linux/vfs.h> #include <linux/slab.h> #include "squashfs_fs.h" #include "squashfs_fs_sb.h" #include "squashfs_fs_i.h" #include "squashfs.h" static const unsigned char squashfs_filetype_table[] = { DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK }; /* * Lookup offset (f_pos) in the directory index, returning the * metadata block containing it. * * If we get an error reading the index then return the part of the index * (if any) we have managed to read - the index isn't essential, just * quicker. */ static int get_dir_index_using_offset(struct super_block *sb, u64 *next_block, int *next_offset, u64 index_start, int index_offset, int i_count, u64 f_pos) { struct squashfs_sb_info *msblk = sb->s_fs_info; int err, i, index, length = 0; struct squashfs_dir_index dir_index; TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n", i_count, f_pos); /* * Translate from external f_pos to the internal f_pos. This * is offset by 3 because we invent "." and ".." entries which are * not actually stored in the directory. */ if (f_pos <= 3) return f_pos; f_pos -= 3; for (i = 0; i < i_count; i++) { err = squashfs_read_metadata(sb, &dir_index, &index_start, &index_offset, sizeof(dir_index)); if (err < 0) break; index = le32_to_cpu(dir_index.index); if (index > f_pos) /* * Found the index we're looking for. */ break; err = squashfs_read_metadata(sb, NULL, &index_start, &index_offset, le32_to_cpu(dir_index.size) + 1); if (err < 0) break; length = index; *next_block = le32_to_cpu(dir_index.start_block) + msblk->directory_table; } *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE; /* * Translate back from internal f_pos to external f_pos. */ return length + 3; } static int squashfs_readdir(struct file *file, struct dir_context *ctx) { struct inode *inode = file_inode(file); struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; u64 block = squashfs_i(inode)->start + msblk->directory_table; int offset = squashfs_i(inode)->offset, length, dir_count, size, type, err; unsigned int inode_number; struct squashfs_dir_header dirh; struct squashfs_dir_entry *dire; TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset); dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL); if (dire == NULL) { ERROR("Failed to allocate squashfs_dir_entry\n"); goto finish; } /* * Return "." and ".." entries as the first two filenames in the * directory. To maximise compression these two entries are not * stored in the directory, and so we invent them here. * * It also means that the external f_pos is offset by 3 from the * on-disk directory f_pos. */ while (ctx->pos < 3) { char *name; int i_ino; if (ctx->pos == 0) { name = "."; size = 1; i_ino = inode->i_ino; } else { name = ".."; size = 2; i_ino = squashfs_i(inode)->parent; } if (!dir_emit(ctx, name, size, i_ino, squashfs_filetype_table[1])) goto finish; ctx->pos += size; } length = get_dir_index_using_offset(inode->i_sb, &block, &offset, squashfs_i(inode)->dir_idx_start, squashfs_i(inode)->dir_idx_offset, squashfs_i(inode)->dir_idx_cnt, ctx->pos); while (length < i_size_read(inode)) { /* * Read directory header */ err = squashfs_read_metadata(inode->i_sb, &dirh, &block, &offset, sizeof(dirh)); if (err < 0) goto failed_read; length += sizeof(dirh); dir_count = le32_to_cpu(dirh.count) + 1; if (dir_count > SQUASHFS_DIR_COUNT) goto failed_read; while (dir_count--) { /* * Read directory entry. */ err = squashfs_read_metadata(inode->i_sb, dire, &block, &offset, sizeof(*dire)); if (err < 0) goto failed_read; size = le16_to_cpu(dire->size) + 1; /* size should never be larger than SQUASHFS_NAME_LEN */ if (size > SQUASHFS_NAME_LEN) goto failed_read; err = squashfs_read_metadata(inode->i_sb, dire->name, &block, &offset, size); if (err < 0) goto failed_read; length += sizeof(*dire) + size; if (ctx->pos >= length) continue; dire->name[size] = '\0'; inode_number = le32_to_cpu(dirh.inode_number) + ((short) le16_to_cpu(dire->inode_number)); type = le16_to_cpu(dire->type); if (!dir_emit(ctx, dire->name, size, inode_number, squashfs_filetype_table[type])) goto finish; ctx->pos = length; } } finish: kfree(dire); return 0; failed_read: ERROR("Unable to read directory block [%llx:%x]\n", block, offset); kfree(dire); return 0; } const struct file_operations squashfs_dir_ops = { .read = generic_read_dir, .iterate = squashfs_readdir, .llseek = default_llseek, };