Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 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> |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 32 | #include <linux/string.h> |
| 33 | #include <linux/buffer_head.h> |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 34 | |
| 35 | #include "squashfs_fs.h" |
| 36 | #include "squashfs_fs_sb.h" |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 37 | #include "squashfs.h" |
Phillip Lougher | 4c0f0bb | 2009-10-06 04:04:15 +0100 | [diff] [blame] | 38 | #include "decompressor.h" |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 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; |
Phillip Lougher | 3689456 | 2011-01-25 15:07:34 -0800 | [diff] [blame] | 66 | |
| 67 | if (*offset == msblk->devblksize) { |
| 68 | put_bh(bh); |
| 69 | bh = sb_bread(sb, ++(*cur_index)); |
| 70 | if (bh == NULL) |
| 71 | return NULL; |
| 72 | *offset = 0; |
| 73 | } |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 74 | } |
| 75 | |
| 76 | return bh; |
| 77 | } |
| 78 | |
| 79 | |
| 80 | /* |
| 81 | * Read and decompress a metadata block or datablock. Length is non-zero |
| 82 | * if a datablock is being read (the size is stored elsewhere in the |
| 83 | * filesystem), otherwise the length is obtained from the first two bytes of |
| 84 | * the metadata block. A bit in the length field indicates if the block |
| 85 | * is stored uncompressed in the filesystem (usually because compression |
| 86 | * generated a larger block - this does occasionally happen with zlib). |
| 87 | */ |
| 88 | int squashfs_read_data(struct super_block *sb, void **buffer, u64 index, |
Phillip Lougher | 118e1ef | 2009-03-05 00:31:12 +0000 | [diff] [blame] | 89 | int length, u64 *next_index, int srclength, int pages) |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 90 | { |
| 91 | struct squashfs_sb_info *msblk = sb->s_fs_info; |
| 92 | struct buffer_head **bh; |
| 93 | int offset = index & ((1 << msblk->devblksize_log2) - 1); |
| 94 | u64 cur_index = index >> msblk->devblksize_log2; |
| 95 | int bytes, compressed, b = 0, k = 0, page = 0, avail; |
| 96 | |
Phillip Lougher | e0d1f70 | 2010-04-23 02:32:02 +0100 | [diff] [blame] | 97 | bh = kcalloc(((srclength + msblk->devblksize - 1) |
| 98 | >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL); |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 99 | if (bh == NULL) |
| 100 | return -ENOMEM; |
| 101 | |
| 102 | if (length) { |
| 103 | /* |
| 104 | * Datablock. |
| 105 | */ |
| 106 | bytes = -offset; |
| 107 | compressed = SQUASHFS_COMPRESSED_BLOCK(length); |
| 108 | length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); |
| 109 | if (next_index) |
| 110 | *next_index = index + length; |
| 111 | |
| 112 | TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", |
| 113 | index, compressed ? "" : "un", length, srclength); |
| 114 | |
| 115 | if (length < 0 || length > srclength || |
| 116 | (index + length) > msblk->bytes_used) |
| 117 | goto read_failure; |
| 118 | |
| 119 | for (b = 0; bytes < length; b++, cur_index++) { |
| 120 | bh[b] = sb_getblk(sb, cur_index); |
| 121 | if (bh[b] == NULL) |
| 122 | goto block_release; |
| 123 | bytes += msblk->devblksize; |
| 124 | } |
| 125 | ll_rw_block(READ, b, bh); |
| 126 | } else { |
| 127 | /* |
| 128 | * Metadata block. |
| 129 | */ |
| 130 | if ((index + 2) > msblk->bytes_used) |
| 131 | goto read_failure; |
| 132 | |
| 133 | bh[0] = get_block_length(sb, &cur_index, &offset, &length); |
| 134 | if (bh[0] == NULL) |
| 135 | goto read_failure; |
| 136 | b = 1; |
| 137 | |
| 138 | bytes = msblk->devblksize - offset; |
| 139 | compressed = SQUASHFS_COMPRESSED(length); |
| 140 | length = SQUASHFS_COMPRESSED_SIZE(length); |
| 141 | if (next_index) |
| 142 | *next_index = index + length + 2; |
| 143 | |
| 144 | TRACE("Block @ 0x%llx, %scompressed size %d\n", index, |
| 145 | compressed ? "" : "un", length); |
| 146 | |
| 147 | if (length < 0 || length > srclength || |
| 148 | (index + length) > msblk->bytes_used) |
| 149 | goto block_release; |
| 150 | |
| 151 | for (; bytes < length; b++) { |
| 152 | bh[b] = sb_getblk(sb, ++cur_index); |
| 153 | if (bh[b] == NULL) |
| 154 | goto block_release; |
| 155 | bytes += msblk->devblksize; |
| 156 | } |
| 157 | ll_rw_block(READ, b - 1, bh + 1); |
| 158 | } |
| 159 | |
| 160 | if (compressed) { |
Phillip Lougher | 4c0f0bb | 2009-10-06 04:04:15 +0100 | [diff] [blame] | 161 | length = squashfs_decompress(msblk, buffer, bh, b, offset, |
Phillip Lougher | e6a6d37 | 2009-09-22 19:25:24 +0100 | [diff] [blame] | 162 | length, srclength, pages); |
| 163 | if (length < 0) |
| 164 | goto read_failure; |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 165 | } else { |
| 166 | /* |
| 167 | * Block is uncompressed. |
| 168 | */ |
| 169 | int i, in, pg_offset = 0; |
| 170 | |
| 171 | for (i = 0; i < b; i++) { |
| 172 | wait_on_buffer(bh[i]); |
| 173 | if (!buffer_uptodate(bh[i])) |
| 174 | goto block_release; |
| 175 | } |
| 176 | |
| 177 | for (bytes = length; k < b; k++) { |
| 178 | in = min(bytes, msblk->devblksize - offset); |
| 179 | bytes -= in; |
| 180 | while (in) { |
| 181 | if (pg_offset == PAGE_CACHE_SIZE) { |
| 182 | page++; |
| 183 | pg_offset = 0; |
| 184 | } |
| 185 | avail = min_t(int, in, PAGE_CACHE_SIZE - |
| 186 | pg_offset); |
| 187 | memcpy(buffer[page] + pg_offset, |
| 188 | bh[k]->b_data + offset, avail); |
| 189 | in -= avail; |
| 190 | pg_offset += avail; |
| 191 | offset += avail; |
| 192 | } |
| 193 | offset = 0; |
| 194 | put_bh(bh[k]); |
| 195 | } |
| 196 | } |
| 197 | |
| 198 | kfree(bh); |
| 199 | return length; |
| 200 | |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 201 | block_release: |
| 202 | for (; k < b; k++) |
| 203 | put_bh(bh[k]); |
| 204 | |
| 205 | read_failure: |
Phillip Lougher | 118e1ef | 2009-03-05 00:31:12 +0000 | [diff] [blame] | 206 | ERROR("squashfs_read_data failed to read block 0x%llx\n", |
| 207 | (unsigned long long) index); |
Phillip Lougher | e2780ab | 2009-01-05 08:46:27 +0000 | [diff] [blame] | 208 | kfree(bh); |
| 209 | return -EIO; |
| 210 | } |