1122edd15SPhillip Lougher /* 2122edd15SPhillip Lougher * Squashfs - a compressed read only filesystem for Linux 3122edd15SPhillip Lougher * 4122edd15SPhillip Lougher * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 5d7f2ff67SPhillip Lougher * Phillip Lougher <phillip@squashfs.org.uk> 6122edd15SPhillip Lougher * 7122edd15SPhillip Lougher * This program is free software; you can redistribute it and/or 8122edd15SPhillip Lougher * modify it under the terms of the GNU General Public License 9122edd15SPhillip Lougher * as published by the Free Software Foundation; either version 2, 10122edd15SPhillip Lougher * or (at your option) any later version. 11122edd15SPhillip Lougher * 12122edd15SPhillip Lougher * This program is distributed in the hope that it will be useful, 13122edd15SPhillip Lougher * but WITHOUT ANY WARRANTY; without even the implied warranty of 14122edd15SPhillip Lougher * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15122edd15SPhillip Lougher * GNU General Public License for more details. 16122edd15SPhillip Lougher * 17122edd15SPhillip Lougher * You should have received a copy of the GNU General Public License 18122edd15SPhillip Lougher * along with this program; if not, write to the Free Software 19122edd15SPhillip Lougher * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. 20122edd15SPhillip Lougher * 21122edd15SPhillip Lougher * fragment.c 22122edd15SPhillip Lougher */ 23122edd15SPhillip Lougher 24122edd15SPhillip Lougher /* 25122edd15SPhillip Lougher * This file implements code to handle compressed fragments (tail-end packed 26122edd15SPhillip Lougher * datablocks). 27122edd15SPhillip Lougher * 28122edd15SPhillip Lougher * Regular files contain a fragment index which is mapped to a fragment 29122edd15SPhillip Lougher * location on disk and compressed size using a fragment lookup table. 30122edd15SPhillip Lougher * Like everything in Squashfs this fragment lookup table is itself stored 31122edd15SPhillip Lougher * compressed into metadata blocks. A second index table is used to locate 32122edd15SPhillip Lougher * these. This second index table for speed of access (and because it 33122edd15SPhillip Lougher * is small) is read at mount time and cached in memory. 34122edd15SPhillip Lougher */ 35122edd15SPhillip Lougher 36122edd15SPhillip Lougher #include <linux/fs.h> 37122edd15SPhillip Lougher #include <linux/vfs.h> 38122edd15SPhillip Lougher #include <linux/slab.h> 39122edd15SPhillip Lougher 40122edd15SPhillip Lougher #include "squashfs_fs.h" 41122edd15SPhillip Lougher #include "squashfs_fs_sb.h" 42122edd15SPhillip Lougher #include "squashfs.h" 43122edd15SPhillip Lougher 44122edd15SPhillip Lougher /* 45122edd15SPhillip Lougher * Look-up fragment using the fragment index table. Return the on disk 46122edd15SPhillip Lougher * location of the fragment and its compressed size 47122edd15SPhillip Lougher */ 48122edd15SPhillip Lougher int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment, 49122edd15SPhillip Lougher u64 *fragment_block) 50122edd15SPhillip Lougher { 51122edd15SPhillip Lougher struct squashfs_sb_info *msblk = sb->s_fs_info; 5271755ee5SLinus Torvalds int block, offset, size; 53122edd15SPhillip Lougher struct squashfs_fragment_entry fragment_entry; 5471755ee5SLinus Torvalds u64 start_block; 5571755ee5SLinus Torvalds 5671755ee5SLinus Torvalds if (fragment >= msblk->fragments) 5771755ee5SLinus Torvalds return -EIO; 5871755ee5SLinus Torvalds block = SQUASHFS_FRAGMENT_INDEX(fragment); 5971755ee5SLinus Torvalds offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment); 6071755ee5SLinus Torvalds 6171755ee5SLinus Torvalds start_block = le64_to_cpu(msblk->fragment_index[block]); 62122edd15SPhillip Lougher 63122edd15SPhillip Lougher size = squashfs_read_metadata(sb, &fragment_entry, &start_block, 64122edd15SPhillip Lougher &offset, sizeof(fragment_entry)); 65122edd15SPhillip Lougher if (size < 0) 66122edd15SPhillip Lougher return size; 67122edd15SPhillip Lougher 68122edd15SPhillip Lougher *fragment_block = le64_to_cpu(fragment_entry.start_block); 6901cfb793SLinus Torvalds return squashfs_block_size(fragment_entry.size); 70122edd15SPhillip Lougher } 71122edd15SPhillip Lougher 72122edd15SPhillip Lougher 73122edd15SPhillip Lougher /* 74122edd15SPhillip Lougher * Read the uncompressed fragment lookup table indexes off disk into memory 75122edd15SPhillip Lougher */ 76122edd15SPhillip Lougher __le64 *squashfs_read_fragment_index_table(struct super_block *sb, 771cac63ccSPhillip Lougher u64 fragment_table_start, u64 next_table, unsigned int fragments) 78122edd15SPhillip Lougher { 79122edd15SPhillip Lougher unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments); 801cac63ccSPhillip Lougher __le64 *table; 81122edd15SPhillip Lougher 821cac63ccSPhillip Lougher /* 831cac63ccSPhillip Lougher * Sanity check, length bytes should not extend into the next table - 841cac63ccSPhillip Lougher * this check also traps instances where fragment_table_start is 851cac63ccSPhillip Lougher * incorrectly larger than the next table start 861cac63ccSPhillip Lougher */ 871cac63ccSPhillip Lougher if (fragment_table_start + length > next_table) 881cac63ccSPhillip Lougher return ERR_PTR(-EINVAL); 891cac63ccSPhillip Lougher 901cac63ccSPhillip Lougher table = squashfs_read_table(sb, fragment_table_start, length); 911cac63ccSPhillip Lougher 921cac63ccSPhillip Lougher /* 931cac63ccSPhillip Lougher * table[0] points to the first fragment table metadata block, this 941cac63ccSPhillip Lougher * should be less than fragment_table_start 951cac63ccSPhillip Lougher */ 96d5b72ce1SPhillip Lougher if (!IS_ERR(table) && le64_to_cpu(table[0]) >= fragment_table_start) { 971cac63ccSPhillip Lougher kfree(table); 981cac63ccSPhillip Lougher return ERR_PTR(-EINVAL); 991cac63ccSPhillip Lougher } 1001cac63ccSPhillip Lougher 1011cac63ccSPhillip Lougher return table; 102122edd15SPhillip Lougher } 103