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/fs/squashfs/fragment.c

https://bitbucket.org/cyanogenmod/android_kernel_asus_tf300t
C | 99 lines | 37 code | 13 blank | 49 comment | 4 complexity | f60e1ee213a3bf720d1d71d109307de8 MD5 | raw file
Possible License(s): LGPL-2.0, AGPL-1.0, GPL-2.0
 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 */
48int 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 = SQUASHFS_FRAGMENT_INDEX(fragment);
53	int offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment);
54	u64 start_block = le64_to_cpu(msblk->fragment_index[block]);
55	struct squashfs_fragment_entry fragment_entry;
56	int size;
57
58	size = squashfs_read_metadata(sb, &fragment_entry, &start_block,
59					&offset, sizeof(fragment_entry));
60	if (size < 0)
61		return size;
62
63	*fragment_block = le64_to_cpu(fragment_entry.start_block);
64	size = le32_to_cpu(fragment_entry.size);
65
66	return size;
67}
68
69
70/*
71 * Read the uncompressed fragment lookup table indexes off disk into memory
72 */
73__le64 *squashfs_read_fragment_index_table(struct super_block *sb,
74	u64 fragment_table_start, u64 next_table, unsigned int fragments)
75{
76	unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
77	__le64 *table;
78
79	/*
80	 * Sanity check, length bytes should not extend into the next table -
81	 * this check also traps instances where fragment_table_start is
82	 * incorrectly larger than the next table start
83	 */
84	if (fragment_table_start + length > next_table)
85		return ERR_PTR(-EINVAL);
86
87	table = squashfs_read_table(sb, fragment_table_start, length);
88
89	/*
90	 * table[0] points to the first fragment table metadata block, this
91	 * should be less than fragment_table_start
92	 */
93	if (!IS_ERR(table) && le64_to_cpu(table[0]) >= fragment_table_start) {
94		kfree(table);
95		return ERR_PTR(-EINVAL);
96	}
97
98	return table;
99}