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e2780ab1 PL |
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@lougher.demon.co.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 | * block.c | |
22 | */ | |
23 | ||
24 | /* | |
25 | * This file implements the low-level routines to read and decompress | |
26 | * datablocks and metadata blocks. | |
27 | */ | |
28 | ||
29 | #include <linux/fs.h> | |
30 | #include <linux/vfs.h> | |
31 | #include <linux/slab.h> | |
e2780ab1 PL |
32 | #include <linux/string.h> |
33 | #include <linux/buffer_head.h> | |
e2780ab1 PL |
34 | |
35 | #include "squashfs_fs.h" | |
36 | #include "squashfs_fs_sb.h" | |
37 | #include "squashfs_fs_i.h" | |
38 | #include "squashfs.h" | |
39 | ||
40 | /* | |
41 | * Read the metadata block length, this is stored in the first two | |
42 | * bytes of the metadata block. | |
43 | */ | |
44 | static struct buffer_head *get_block_length(struct super_block *sb, | |
45 | u64 *cur_index, int *offset, int *length) | |
46 | { | |
47 | struct squashfs_sb_info *msblk = sb->s_fs_info; | |
48 | struct buffer_head *bh; | |
49 | ||
50 | bh = sb_bread(sb, *cur_index); | |
51 | if (bh == NULL) | |
52 | return NULL; | |
53 | ||
54 | if (msblk->devblksize - *offset == 1) { | |
55 | *length = (unsigned char) bh->b_data[*offset]; | |
56 | put_bh(bh); | |
57 | bh = sb_bread(sb, ++(*cur_index)); | |
58 | if (bh == NULL) | |
59 | return NULL; | |
60 | *length |= (unsigned char) bh->b_data[0] << 8; | |
61 | *offset = 1; | |
62 | } else { | |
63 | *length = (unsigned char) bh->b_data[*offset] | | |
64 | (unsigned char) bh->b_data[*offset + 1] << 8; | |
65 | *offset += 2; | |
66 | } | |
67 | ||
68 | return bh; | |
69 | } | |
70 | ||
71 | ||
72 | /* | |
73 | * Read and decompress a metadata block or datablock. Length is non-zero | |
74 | * if a datablock is being read (the size is stored elsewhere in the | |
75 | * filesystem), otherwise the length is obtained from the first two bytes of | |
76 | * the metadata block. A bit in the length field indicates if the block | |
77 | * is stored uncompressed in the filesystem (usually because compression | |
78 | * generated a larger block - this does occasionally happen with zlib). | |
79 | */ | |
80 | int squashfs_read_data(struct super_block *sb, void **buffer, u64 index, | |
118e1ef6 | 81 | int length, u64 *next_index, int srclength, int pages) |
e2780ab1 PL |
82 | { |
83 | struct squashfs_sb_info *msblk = sb->s_fs_info; | |
84 | struct buffer_head **bh; | |
85 | int offset = index & ((1 << msblk->devblksize_log2) - 1); | |
86 | u64 cur_index = index >> msblk->devblksize_log2; | |
87 | int bytes, compressed, b = 0, k = 0, page = 0, avail; | |
88 | ||
89 | ||
90 | bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1, | |
91 | sizeof(*bh), GFP_KERNEL); | |
92 | if (bh == NULL) | |
93 | return -ENOMEM; | |
94 | ||
95 | if (length) { | |
96 | /* | |
97 | * Datablock. | |
98 | */ | |
99 | bytes = -offset; | |
100 | compressed = SQUASHFS_COMPRESSED_BLOCK(length); | |
101 | length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); | |
102 | if (next_index) | |
103 | *next_index = index + length; | |
104 | ||
105 | TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", | |
106 | index, compressed ? "" : "un", length, srclength); | |
107 | ||
108 | if (length < 0 || length > srclength || | |
109 | (index + length) > msblk->bytes_used) | |
110 | goto read_failure; | |
111 | ||
112 | for (b = 0; bytes < length; b++, cur_index++) { | |
113 | bh[b] = sb_getblk(sb, cur_index); | |
114 | if (bh[b] == NULL) | |
115 | goto block_release; | |
116 | bytes += msblk->devblksize; | |
117 | } | |
118 | ll_rw_block(READ, b, bh); | |
119 | } else { | |
120 | /* | |
121 | * Metadata block. | |
122 | */ | |
123 | if ((index + 2) > msblk->bytes_used) | |
124 | goto read_failure; | |
125 | ||
126 | bh[0] = get_block_length(sb, &cur_index, &offset, &length); | |
127 | if (bh[0] == NULL) | |
128 | goto read_failure; | |
129 | b = 1; | |
130 | ||
131 | bytes = msblk->devblksize - offset; | |
132 | compressed = SQUASHFS_COMPRESSED(length); | |
133 | length = SQUASHFS_COMPRESSED_SIZE(length); | |
134 | if (next_index) | |
135 | *next_index = index + length + 2; | |
136 | ||
137 | TRACE("Block @ 0x%llx, %scompressed size %d\n", index, | |
138 | compressed ? "" : "un", length); | |
139 | ||
140 | if (length < 0 || length > srclength || | |
141 | (index + length) > msblk->bytes_used) | |
142 | goto block_release; | |
143 | ||
144 | for (; bytes < length; b++) { | |
145 | bh[b] = sb_getblk(sb, ++cur_index); | |
146 | if (bh[b] == NULL) | |
147 | goto block_release; | |
148 | bytes += msblk->devblksize; | |
149 | } | |
150 | ll_rw_block(READ, b - 1, bh + 1); | |
151 | } | |
152 | ||
153 | if (compressed) { | |
e6a6d379 PL |
154 | length = squashfs_zlib_uncompress(msblk, buffer, bh, b, offset, |
155 | length, srclength, pages); | |
156 | if (length < 0) | |
157 | goto read_failure; | |
e2780ab1 PL |
158 | } else { |
159 | /* | |
160 | * Block is uncompressed. | |
161 | */ | |
162 | int i, in, pg_offset = 0; | |
163 | ||
164 | for (i = 0; i < b; i++) { | |
165 | wait_on_buffer(bh[i]); | |
166 | if (!buffer_uptodate(bh[i])) | |
167 | goto block_release; | |
168 | } | |
169 | ||
170 | for (bytes = length; k < b; k++) { | |
171 | in = min(bytes, msblk->devblksize - offset); | |
172 | bytes -= in; | |
173 | while (in) { | |
174 | if (pg_offset == PAGE_CACHE_SIZE) { | |
175 | page++; | |
176 | pg_offset = 0; | |
177 | } | |
178 | avail = min_t(int, in, PAGE_CACHE_SIZE - | |
179 | pg_offset); | |
180 | memcpy(buffer[page] + pg_offset, | |
181 | bh[k]->b_data + offset, avail); | |
182 | in -= avail; | |
183 | pg_offset += avail; | |
184 | offset += avail; | |
185 | } | |
186 | offset = 0; | |
187 | put_bh(bh[k]); | |
188 | } | |
189 | } | |
190 | ||
191 | kfree(bh); | |
192 | return length; | |
193 | ||
e2780ab1 PL |
194 | block_release: |
195 | for (; k < b; k++) | |
196 | put_bh(bh[k]); | |
197 | ||
198 | read_failure: | |
118e1ef6 PL |
199 | ERROR("squashfs_read_data failed to read block 0x%llx\n", |
200 | (unsigned long long) index); | |
e2780ab1 PL |
201 | kfree(bh); |
202 | return -EIO; | |
203 | } |