1 /*
2 * Squashfs - a compressed read only filesystem for Linux
3 *
4 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5 * Phillip Lougher <phillip@squashfs.org.uk>
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
9 * as published by the Free Software Foundation; either version 2,
10 * or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20 *
21 * fragment.c
22 */
23
24 /*
25 * This file implements code to handle compressed fragments (tail-end packed
26 * datablocks).
27 *
28 * Regular files contain a fragment index which is mapped to a fragment
29 * location on disk and compressed size using a fragment lookup table.
30 * Like everything in Squashfs this fragment lookup table is itself stored
31 * compressed into metadata blocks. A second index table is used to locate
32 * these. This second index table for speed of access (and because it
33 * is small) is read at mount time and cached in memory.
34 */
35
36 #include <linux/fs.h>
37 #include <linux/vfs.h>
38 #include <linux/slab.h>
39
40 #include "squashfs_fs.h"
41 #include "squashfs_fs_sb.h"
42 #include "squashfs.h"
43
44 /*
45 * Look-up fragment using the fragment index table. Return the on disk
46 * location of the fragment and its compressed size
47 */
squashfs_frag_lookup(struct super_block * sb,unsigned int fragment,u64 * fragment_block)48 int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment,
49 u64 *fragment_block)
50 {
51 struct squashfs_sb_info *msblk = sb->s_fs_info;
52 int block, offset, size;
53 struct squashfs_fragment_entry fragment_entry;
54 u64 start_block;
55
56 if (fragment >= msblk->fragments)
57 return -EIO;
58 block = SQUASHFS_FRAGMENT_INDEX(fragment);
59 offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment);
60
61 start_block = le64_to_cpu(msblk->fragment_index[block]);
62
63 size = squashfs_read_metadata(sb, &fragment_entry, &start_block,
64 &offset, sizeof(fragment_entry));
65 if (size < 0)
66 return size;
67
68 *fragment_block = le64_to_cpu(fragment_entry.start_block);
69 return squashfs_block_size(fragment_entry.size);
70 }
71
72
73 /*
74 * Read the uncompressed fragment lookup table indexes off disk into memory
75 */
squashfs_read_fragment_index_table(struct super_block * sb,u64 fragment_table_start,u64 next_table,unsigned int fragments)76 __le64 *squashfs_read_fragment_index_table(struct super_block *sb,
77 u64 fragment_table_start, u64 next_table, unsigned int fragments)
78 {
79 unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
80 __le64 *table;
81
82 /*
83 * Sanity check, length bytes should not extend into the next table -
84 * this check also traps instances where fragment_table_start is
85 * incorrectly larger than the next table start
86 */
87 if (fragment_table_start + length > next_table)
88 return ERR_PTR(-EINVAL);
89
90 table = squashfs_read_table(sb, fragment_table_start, length);
91
92 /*
93 * table[0] points to the first fragment table metadata block, this
94 * should be less than fragment_table_start
95 */
96 if (!IS_ERR(table) && le64_to_cpu(table[0]) >= fragment_table_start) {
97 kfree(table);
98 return ERR_PTR(-EINVAL);
99 }
100
101 return table;
102 }
103