/* * Squashfs - a compressed read only filesystem for Linux * * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 * Phillip Lougher <phillip@lougher.demon.co.uk> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2, * or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. * * block.c */ /* * This file implements the low-level routines to read and decompress * datablocks and metadata blocks. */ #include <linux/fs.h> #include <linux/vfs.h> #include <linux/slab.h> #include <linux/mutex.h> #include <linux/string.h> #include <linux/buffer_head.h> #include <linux/zlib.h> #include "squashfs_fs.h" #include "squashfs_fs_sb.h" #include "squashfs_fs_i.h" #include "squashfs.h" /* * Read the metadata block length, this is stored in the first two * bytes of the metadata block. */ static struct buffer_head *get_block_length(struct super_block *sb, u64 *cur_index, int *offset, int *length) { struct squashfs_sb_info *msblk = sb->s_fs_info; struct buffer_head *bh; bh = sb_bread(sb, *cur_index); if (bh == NULL) return NULL; if (msblk->devblksize - *offset == 1) { *length = (unsigned char) bh->b_data[*offset]; put_bh(bh); bh = sb_bread(sb, ++(*cur_index)); if (bh == NULL) return NULL; *length |= (unsigned char) bh->b_data[0] << 8; *offset = 1; } else { *length = (unsigned char) bh->b_data[*offset] | (unsigned char) bh->b_data[*offset + 1] << 8; *offset += 2; } return bh; } /* * Read and decompress a metadata block or datablock. Length is non-zero * if a datablock is being read (the size is stored elsewhere in the * filesystem), otherwise the length is obtained from the first two bytes of * the metadata block. A bit in the length field indicates if the block * is stored uncompressed in the filesystem (usually because compression * generated a larger block - this does occasionally happen with zlib). */ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index, int length, u64 *next_index, int srclength, int pages) { struct squashfs_sb_info *msblk = sb->s_fs_info; struct buffer_head **bh; int offset = index & ((1 << msblk->devblksize_log2) - 1); u64 cur_index = index >> msblk->devblksize_log2; int bytes, compressed, b = 0, k = 0, page = 0, avail; bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL); if (bh == NULL) return -ENOMEM; if (length) { /* * Datablock. */ bytes = -offset; compressed = SQUASHFS_COMPRESSED_BLOCK(length); length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); if (next_index) *next_index = index + length; TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", index, compressed ? "" : "un", length, srclength); if (length < 0 || length > srclength || (index + length) > msblk->bytes_used) goto read_failure; for (b = 0; bytes < length; b++, cur_index++) { bh[b] = sb_getblk(sb, cur_index); if (bh[b] == NULL) goto block_release; bytes += msblk->devblksize; } ll_rw_block(READ, b, bh); } else { /* * Metadata block. */ if ((index + 2) > msblk->bytes_used) goto read_failure; bh[0] = get_block_length(sb, &cur_index, &offset, &length); if (bh[0] == NULL) goto read_failure; b = 1; bytes = msblk->devblksize - offset; compressed = SQUASHFS_COMPRESSED(length); length = SQUASHFS_COMPRESSED_SIZE(length); if (next_index) *next_index = index + length + 2; TRACE("Block @ 0x%llx, %scompressed size %d\n", index, compressed ? "" : "un", length); if (length < 0 || length > srclength || (index + length) > msblk->bytes_used) goto block_release; for (; bytes < length; b++) { bh[b] = sb_getblk(sb, ++cur_index); if (bh[b] == NULL) goto block_release; bytes += msblk->devblksize; } ll_rw_block(READ, b - 1, bh + 1); } if (compressed) { int zlib_err = 0, zlib_init = 0; /* * Uncompress block. */ mutex_lock(&msblk->read_data_mutex); msblk->stream.avail_out = 0; msblk->stream.avail_in = 0; bytes = length; do { if (msblk->stream.avail_in == 0 && k < b) { avail = min(bytes, msblk->devblksize - offset); bytes -= avail; wait_on_buffer(bh[k]); if (!buffer_uptodate(bh[k])) goto release_mutex; if (avail == 0) { offset = 0; put_bh(bh[k++]); continue; } msblk->stream.next_in = bh[k]->b_data + offset; msblk->stream.avail_in = avail; offset = 0; } if (msblk->stream.avail_out == 0 && page < pages) { msblk->stream.next_out = buffer[page++]; msblk->stream.avail_out = PAGE_CACHE_SIZE; } if (!zlib_init) { zlib_err = zlib_inflateInit(&msblk->stream); if (zlib_err != Z_OK) { ERROR("zlib_inflateInit returned" " unexpected result 0x%x," " srclength %d\n", zlib_err, srclength); goto release_mutex; } zlib_init = 1; } zlib_err = zlib_inflate(&msblk->stream, Z_SYNC_FLUSH); if (msblk->stream.avail_in == 0 && k < b) put_bh(bh[k++]); } while (zlib_err == Z_OK); if (zlib_err != Z_STREAM_END) { ERROR("zlib_inflate error, data probably corrupt\n"); goto release_mutex; } zlib_err = zlib_inflateEnd(&msblk->stream); if (zlib_err != Z_OK) { ERROR("zlib_inflate error, data probably corrupt\n"); goto release_mutex; } length = msblk->stream.total_out; mutex_unlock(&msblk->read_data_mutex); } else { /* * Block is uncompressed. */ int i, in, pg_offset = 0; for (i = 0; i < b; i++) { wait_on_buffer(bh[i]); if (!buffer_uptodate(bh[i])) goto block_release; } for (bytes = length; k < b; k++) { in = min(bytes, msblk->devblksize - offset); bytes -= in; while (in) { if (pg_offset == PAGE_CACHE_SIZE) { page++; pg_offset = 0; } avail = min_t(int, in, PAGE_CACHE_SIZE - pg_offset); memcpy(buffer[page] + pg_offset, bh[k]->b_data + offset, avail); in -= avail; pg_offset += avail; offset += avail; } offset = 0; put_bh(bh[k]); } } kfree(bh); return length; release_mutex: mutex_unlock(&msblk->read_data_mutex); block_release: for (; k < b; k++) put_bh(bh[k]); read_failure: ERROR("squashfs_read_data failed to read block 0x%llx\n", (unsigned long long) index); kfree(bh); return -EIO; }