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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@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>
  32 #include <linux/mutex.h>
  33 #include <linux/string.h>
  34 #include <linux/buffer_head.h>
  35 #include <linux/zlib.h>
  36
  37 #include "squashfs_fs.h"
  38 #include "squashfs_fs_sb.h"
  39 #include "squashfs_fs_i.h"
  40 #include "squashfs.h"
  41
  42 /*
  43  * Read the metadata block length, this is stored in the first two
  44  * bytes of the metadata block.
  45  */
  46 static struct buffer_head *get_block_length(struct super_block *sb,
  47                         u64 *cur_index, int *offset, int *length)
  48 {
  49         struct squashfs_sb_info *msblk = sb->s_fs_info;
  50         struct buffer_head *bh;
  51
  52         bh = sb_bread(sb, *cur_index);
  53         if (bh == NULL)
  54                 return NULL;
  55
  56         if (msblk->devblksize - *offset == 1) {
  57                 *length = (unsigned char) bh->b_data[*offset];
  58                 put_bh(bh);
  59                 bh = sb_bread(sb, ++(*cur_index));
  60                 if (bh == NULL)
  61                         return NULL;
  62                 *length |= (unsigned char) bh->b_data[0] << 8;
  63                 *offset = 1;
  64         } else {
  65                 *length = (unsigned char) bh->b_data[*offset] |
  66                         (unsigned char) bh->b_data[*offset + 1] << 8;
  67                 *offset += 2;
  68         }
  69
  70         return bh;
  71 }
  72
  73
  74 /*
  75  * Read and decompress a metadata block or datablock.  Length is non-zero
  76  * if a datablock is being read (the size is stored elsewhere in the
  77  * filesystem), otherwise the length is obtained from the first two bytes of
  78  * the metadata block.  A bit in the length field indicates if the block
  79  * is stored uncompressed in the filesystem (usually because compression
  80  * generated a larger block - this does occasionally happen with zlib).
  81  */
  82 int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
  83                         int length, u64 *next_index, int srclength, int pages)
  84 {
  85         struct squashfs_sb_info *msblk = sb->s_fs_info;
  86         struct buffer_head **bh;
  87         int offset = index & ((1 << msblk->devblksize_log2) - 1);
  88         u64 cur_index = index >> msblk->devblksize_log2;
  89         int bytes, compressed, b = 0, k = 0, page = 0, avail;
  90
  91
  92         bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1,
  93                                 sizeof(*bh), GFP_KERNEL);
  94         if (bh == NULL)
  95                 return -ENOMEM;
  96
  97         if (length) {
  98                 /*
  99                  * Datablock.
 100                  */
 101                 bytes = -offset;
 102                 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
 103                 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
 104                 if (next_index)
 105                         *next_index = index + length;
 106
 107                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
 108                         index, compressed ? "" : "un", length, srclength);
 109
 110                 if (length < 0 || length > srclength ||
 111                                 (index + length) > msblk->bytes_used)
 112                         goto read_failure;
 113
 114                 for (b = 0; bytes < length; b++, cur_index++) {
 115                         bh[b] = sb_getblk(sb, cur_index);
 116                         if (bh[b] == NULL)
 117                                 goto block_release;
 118                         bytes += msblk->devblksize;
 119                 }
 120                 ll_rw_block(READ, b, bh);
 121         } else {
 122                 /*
 123                  * Metadata block.
 124                  */
 125                 if ((index + 2) > msblk->bytes_used)
 126                         goto read_failure;
 127
 128                 bh[0] = get_block_length(sb, &cur_index, &offset, &length);
 129                 if (bh[0] == NULL)
 130                         goto read_failure;
 131                 b = 1;
 132
 133                 bytes = msblk->devblksize - offset;
 134                 compressed = SQUASHFS_COMPRESSED(length);
 135                 length = SQUASHFS_COMPRESSED_SIZE(length);
 136                 if (next_index)
 137                         *next_index = index + length + 2;
 138
 139                 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
 140                                 compressed ? "" : "un", length);
 141
 142                 if (length < 0 || length > srclength ||
 143                                         (index + length) > msblk->bytes_used)
 144                         goto block_release;
 145
 146                 for (; bytes < length; b++) {
 147                         bh[b] = sb_getblk(sb, ++cur_index);
 148                         if (bh[b] == NULL)
 149                                 goto block_release;
 150                         bytes += msblk->devblksize;
 151                 }
 152                 ll_rw_block(READ, b - 1, bh + 1);
 153         }
 154
 155         if (compressed) {
 156                 int zlib_err = 0, zlib_init = 0;
 157
 158                 /*
 159                  * Uncompress block.
 160                  */
 161
 162                 mutex_lock(&msblk->read_data_mutex);
 163
 164                 msblk->stream.avail_out = 0;
 165                 msblk->stream.avail_in = 0;
 166
 167                 bytes = length;
 168                 do {
 169                         if (msblk->stream.avail_in == 0 && k < b) {
 170                                 avail = min(bytes, msblk->devblksize - offset);
 171                                 bytes -= avail;
 172                                 wait_on_buffer(bh[k]);
 173                                 if (!buffer_uptodate(bh[k]))
 174                                         goto release_mutex;
 175
 176                                 if (avail == 0) {
 177                                         offset = 0;
 178                                         put_bh(bh[k++]);
 179                                         continue;
 180                                 }
 181
 182                                 msblk->stream.next_in = bh[k]->b_data + offset;
 183                                 msblk->stream.avail_in = avail;
 184                                 offset = 0;
 185                         }
 186
 187                         if (msblk->stream.avail_out == 0 && page < pages) {
 188                                 msblk->stream.next_out = buffer[page++];
 189                                 msblk->stream.avail_out = PAGE_CACHE_SIZE;
 190                         }
 191
 192                         if (!zlib_init) {
 193                                 zlib_err = zlib_inflateInit(&msblk->stream);
 194                                 if (zlib_err != Z_OK) {
 195                                         ERROR("zlib_inflateInit returned"
 196                                                 " unexpected result 0x%x,"
 197                                                 " srclength %d\n", zlib_err,
 198                                                 srclength);
 199                                         goto release_mutex;
 200                                 }
 201                                 zlib_init = 1;
 202                         }
 203
 204                         zlib_err = zlib_inflate(&msblk->stream, Z_SYNC_FLUSH);
 205
 206                         if (msblk->stream.avail_in == 0 && k < b)
 207                                 put_bh(bh[k++]);
 208                 } while (zlib_err == Z_OK);
 209
 210                 if (zlib_err != Z_STREAM_END) {
 211                         ERROR("zlib_inflate error, data probably corrupt\n");
 212                         goto release_mutex;
 213                 }
 214
 215                 zlib_err = zlib_inflateEnd(&msblk->stream);
 216                 if (zlib_err != Z_OK) {
 217                         ERROR("zlib_inflate error, data probably corrupt\n");
 218                         goto release_mutex;
 219                 }
 220                 length = msblk->stream.total_out;
 221                 mutex_unlock(&msblk->read_data_mutex);
 222         } else {
 223                 /*
 224                  * Block is uncompressed.
 225                  */
 226                 int i, in, pg_offset = 0;
 227
 228                 for (i = 0; i < b; i++) {
 229                         wait_on_buffer(bh[i]);
 230                         if (!buffer_uptodate(bh[i]))
 231                                 goto block_release;
 232                 }
 233
 234                 for (bytes = length; k < b; k++) {
 235                         in = min(bytes, msblk->devblksize - offset);
 236                         bytes -= in;
 237                         while (in) {
 238                                 if (pg_offset == PAGE_CACHE_SIZE) {
 239                                         page++;
 240                                         pg_offset = 0;
 241                                 }
 242                                 avail = min_t(int, in, PAGE_CACHE_SIZE -
 243                                                 pg_offset);
 244                                 memcpy(buffer[page] + pg_offset,
 245                                                 bh[k]->b_data + offset, avail);
 246                                 in -= avail;
 247                                 pg_offset += avail;
 248                                 offset += avail;
 249                         }
 250                         offset = 0;
 251                         put_bh(bh[k]);
 252                 }
 253         }
 254
 255         kfree(bh);
 256         return length;
 257
 258 release_mutex:
 259         mutex_unlock(&msblk->read_data_mutex);
 260
 261 block_release:
 262         for (; k < b; k++)
 263                 put_bh(bh[k]);
 264
 265 read_failure:
 266         ERROR("squashfs_read_data failed to read block 0x%llx\n",
 267                                         (unsigned long long) index);
 268         kfree(bh);
 269         return -EIO;
 270 }