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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 * 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>
32#include <linux/string.h>
33#include <linux/buffer_head.h>
34
35#include "squashfs_fs.h"
36#include "squashfs_fs_sb.h"
37#include "squashfs.h"
38#include "decompressor.h"
39#include "page_actor.h"
40
41/*
42 * Read the metadata block length, this is stored in the first two
43 * bytes of the metadata block.
44 */
45static struct buffer_head *get_block_length(struct super_block *sb,
46 u64 *cur_index, int *offset, int *length)
47{
48 struct squashfs_sb_info *msblk = sb->s_fs_info;
49 struct buffer_head *bh;
50
51 bh = sb_bread(sb, *cur_index);
52 if (bh == NULL)
53 return NULL;
54
55 if (msblk->devblksize - *offset == 1) {
56 *length = (unsigned char) bh->b_data[*offset];
57 put_bh(bh);
58 bh = sb_bread(sb, ++(*cur_index));
59 if (bh == NULL)
60 return NULL;
61 *length |= (unsigned char) bh->b_data[0] << 8;
62 *offset = 1;
63 } else {
64 *length = (unsigned char) bh->b_data[*offset] |
65 (unsigned char) bh->b_data[*offset + 1] << 8;
66 *offset += 2;
67
68 if (*offset == msblk->devblksize) {
69 put_bh(bh);
70 bh = sb_bread(sb, ++(*cur_index));
71 if (bh == NULL)
72 return NULL;
73 *offset = 0;
74 }
75 }
76
77 return bh;
78}
79
80
81/*
82 * Read and decompress a metadata block or datablock. Length is non-zero
83 * if a datablock is being read (the size is stored elsewhere in the
84 * filesystem), otherwise the length is obtained from the first two bytes of
85 * the metadata block. A bit in the length field indicates if the block
86 * is stored uncompressed in the filesystem (usually because compression
87 * generated a larger block - this does occasionally happen with compression
88 * algorithms).
89 */
90int squashfs_read_data(struct super_block *sb, u64 index, int length,
91 u64 *next_index, struct squashfs_page_actor *output)
92{
93 struct squashfs_sb_info *msblk = sb->s_fs_info;
94 struct buffer_head **bh;
95 int offset = index & ((1 << msblk->devblksize_log2) - 1);
96 u64 cur_index = index >> msblk->devblksize_log2;
97 int bytes, compressed, b = 0, k = 0, avail, i;
98
99 bh = kcalloc(((output->length + msblk->devblksize - 1)
100 >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
101 if (bh == NULL)
102 return -ENOMEM;
103
104 if (length) {
105 /*
106 * Datablock.
107 */
108 bytes = -offset;
109 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
110 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
111 if (next_index)
112 *next_index = index + length;
113
114 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
115 index, compressed ? "" : "un", length, output->length);
116
117 if (length < 0 || length > output->length ||
118 (index + length) > msblk->bytes_used)
119 goto read_failure;
120
121 for (b = 0; bytes < length; b++, cur_index++) {
122 bh[b] = sb_getblk(sb, cur_index);
123 if (bh[b] == NULL)
124 goto block_release;
125 bytes += msblk->devblksize;
126 }
127 ll_rw_block(READ, b, bh);
128 } else {
129 /*
130 * Metadata block.
131 */
132 if ((index + 2) > msblk->bytes_used)
133 goto read_failure;
134
135 bh[0] = get_block_length(sb, &cur_index, &offset, &length);
136 if (bh[0] == NULL)
137 goto read_failure;
138 b = 1;
139
140 bytes = msblk->devblksize - offset;
141 compressed = SQUASHFS_COMPRESSED(length);
142 length = SQUASHFS_COMPRESSED_SIZE(length);
143 if (next_index)
144 *next_index = index + length + 2;
145
146 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
147 compressed ? "" : "un", length);
148
149 if (length < 0 || length > output->length ||
150 (index + length) > msblk->bytes_used)
151 goto block_release;
152
153 for (; bytes < length; b++) {
154 bh[b] = sb_getblk(sb, ++cur_index);
155 if (bh[b] == NULL)
156 goto block_release;
157 bytes += msblk->devblksize;
158 }
159 ll_rw_block(READ, b - 1, bh + 1);
160 }
161
162 for (i = 0; i < b; i++) {
163 wait_on_buffer(bh[i]);
164 if (!buffer_uptodate(bh[i]))
165 goto block_release;
166 }
167
168 if (compressed) {
169 length = squashfs_decompress(msblk, bh, b, offset, length,
170 output);
171 if (length < 0)
172 goto read_failure;
173 } else {
174 /*
175 * Block is uncompressed.
176 */
177 int in, pg_offset = 0;
178 void *data = squashfs_first_page(output);
179
180 for (bytes = length; k < b; k++) {
181 in = min(bytes, msblk->devblksize - offset);
182 bytes -= in;
183 while (in) {
184 if (pg_offset == PAGE_SIZE) {
185 data = squashfs_next_page(output);
186 pg_offset = 0;
187 }
188 avail = min_t(int, in, PAGE_SIZE -
189 pg_offset);
190 memcpy(data + pg_offset, bh[k]->b_data + offset,
191 avail);
192 in -= avail;
193 pg_offset += avail;
194 offset += avail;
195 }
196 offset = 0;
197 put_bh(bh[k]);
198 }
199 squashfs_finish_page(output);
200 }
201
202 kfree(bh);
203 return length;
204
205block_release:
206 for (; k < b; k++)
207 put_bh(bh[k]);
208
209read_failure:
210 ERROR("squashfs_read_data failed to read block 0x%llx\n",
211 (unsigned long long) index);
212 kfree(bh);
213 return -EIO;
214}
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 * 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>
32#include <linux/string.h>
33#include <linux/buffer_head.h>
34
35#include "squashfs_fs.h"
36#include "squashfs_fs_sb.h"
37#include "squashfs.h"
38#include "decompressor.h"
39#include "page_actor.h"
40
41/*
42 * Read the metadata block length, this is stored in the first two
43 * bytes of the metadata block.
44 */
45static struct buffer_head *get_block_length(struct super_block *sb,
46 u64 *cur_index, int *offset, int *length)
47{
48 struct squashfs_sb_info *msblk = sb->s_fs_info;
49 struct buffer_head *bh;
50
51 bh = sb_bread(sb, *cur_index);
52 if (bh == NULL)
53 return NULL;
54
55 if (msblk->devblksize - *offset == 1) {
56 *length = (unsigned char) bh->b_data[*offset];
57 put_bh(bh);
58 bh = sb_bread(sb, ++(*cur_index));
59 if (bh == NULL)
60 return NULL;
61 *length |= (unsigned char) bh->b_data[0] << 8;
62 *offset = 1;
63 } else {
64 *length = (unsigned char) bh->b_data[*offset] |
65 (unsigned char) bh->b_data[*offset + 1] << 8;
66 *offset += 2;
67
68 if (*offset == msblk->devblksize) {
69 put_bh(bh);
70 bh = sb_bread(sb, ++(*cur_index));
71 if (bh == NULL)
72 return NULL;
73 *offset = 0;
74 }
75 }
76
77 return bh;
78}
79
80
81/*
82 * Read and decompress a metadata block or datablock. Length is non-zero
83 * if a datablock is being read (the size is stored elsewhere in the
84 * filesystem), otherwise the length is obtained from the first two bytes of
85 * the metadata block. A bit in the length field indicates if the block
86 * is stored uncompressed in the filesystem (usually because compression
87 * generated a larger block - this does occasionally happen with compression
88 * algorithms).
89 */
90int squashfs_read_data(struct super_block *sb, u64 index, int length,
91 u64 *next_index, struct squashfs_page_actor *output)
92{
93 struct squashfs_sb_info *msblk = sb->s_fs_info;
94 struct buffer_head **bh;
95 int offset = index & ((1 << msblk->devblksize_log2) - 1);
96 u64 cur_index = index >> msblk->devblksize_log2;
97 int bytes, compressed, b = 0, k = 0, avail, i;
98
99 bh = kcalloc(((output->length + msblk->devblksize - 1)
100 >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
101 if (bh == NULL)
102 return -ENOMEM;
103
104 if (length) {
105 /*
106 * Datablock.
107 */
108 bytes = -offset;
109 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
110 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
111 if (next_index)
112 *next_index = index + length;
113
114 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
115 index, compressed ? "" : "un", length, output->length);
116
117 if (length < 0 || length > output->length ||
118 (index + length) > msblk->bytes_used)
119 goto read_failure;
120
121 for (b = 0; bytes < length; b++, cur_index++) {
122 bh[b] = sb_getblk(sb, cur_index);
123 if (bh[b] == NULL)
124 goto block_release;
125 bytes += msblk->devblksize;
126 }
127 ll_rw_block(READ, b, bh);
128 } else {
129 /*
130 * Metadata block.
131 */
132 if ((index + 2) > msblk->bytes_used)
133 goto read_failure;
134
135 bh[0] = get_block_length(sb, &cur_index, &offset, &length);
136 if (bh[0] == NULL)
137 goto read_failure;
138 b = 1;
139
140 bytes = msblk->devblksize - offset;
141 compressed = SQUASHFS_COMPRESSED(length);
142 length = SQUASHFS_COMPRESSED_SIZE(length);
143 if (next_index)
144 *next_index = index + length + 2;
145
146 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
147 compressed ? "" : "un", length);
148
149 if (length < 0 || length > output->length ||
150 (index + length) > msblk->bytes_used)
151 goto block_release;
152
153 for (; bytes < length; b++) {
154 bh[b] = sb_getblk(sb, ++cur_index);
155 if (bh[b] == NULL)
156 goto block_release;
157 bytes += msblk->devblksize;
158 }
159 ll_rw_block(READ, b - 1, bh + 1);
160 }
161
162 for (i = 0; i < b; i++) {
163 wait_on_buffer(bh[i]);
164 if (!buffer_uptodate(bh[i]))
165 goto block_release;
166 }
167
168 if (compressed) {
169 length = squashfs_decompress(msblk, bh, b, offset, length,
170 output);
171 if (length < 0)
172 goto read_failure;
173 } else {
174 /*
175 * Block is uncompressed.
176 */
177 int in, pg_offset = 0;
178 void *data = squashfs_first_page(output);
179
180 for (bytes = length; k < b; k++) {
181 in = min(bytes, msblk->devblksize - offset);
182 bytes -= in;
183 while (in) {
184 if (pg_offset == PAGE_CACHE_SIZE) {
185 data = squashfs_next_page(output);
186 pg_offset = 0;
187 }
188 avail = min_t(int, in, PAGE_CACHE_SIZE -
189 pg_offset);
190 memcpy(data + pg_offset, bh[k]->b_data + offset,
191 avail);
192 in -= avail;
193 pg_offset += avail;
194 offset += avail;
195 }
196 offset = 0;
197 put_bh(bh[k]);
198 }
199 squashfs_finish_page(output);
200 }
201
202 kfree(bh);
203 return length;
204
205block_release:
206 for (; k < b; k++)
207 put_bh(bh[k]);
208
209read_failure:
210 ERROR("squashfs_read_data failed to read block 0x%llx\n",
211 (unsigned long long) index);
212 kfree(bh);
213 return -EIO;
214}