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/*
* Squashfs - a compressed read only filesystem for Linux
*
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
* Phillip Lougher <phillip@squashfs.org.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.
*
* block.c
*/
/*
* This file implements the low-level routines to read and decompress
* datablocks and metadata blocks.
*/
#include <linux/fs.h>
#include <linux/string.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs.h"
#include "decompressor.h"
#include "page_actor.h"
/*
* Read the metadata block length, this is stored in the first two
* bytes of the metadata block.
*/
static char *get_block_length(struct super_block *sb,
u64 *cur_index, int *offset, int *length)
{
struct squashfs_sb_info *msblk = sb->s_fs_info;
char *buf;
buf = squashfs_devread(msblk,
*cur_index * msblk->devblksize,
msblk->devblksize);
if (buf == NULL)
return NULL;
if (msblk->devblksize - *offset == 1) {
*length = (unsigned char) buf[*offset];
free(buf);
buf = squashfs_devread(msblk,
++(*cur_index) * msblk->devblksize,
msblk->devblksize);
if (buf == NULL)
return NULL;
*length |= (unsigned char) buf[0] << 8;
*offset = 1;
} else {
*length = (unsigned char) buf[*offset] |
(unsigned char) buf[*offset + 1] << 8;
*offset += 2;
if (*offset == msblk->devblksize) {
free(buf);
buf = squashfs_devread(msblk,
++(*cur_index) * msblk->devblksize,
msblk->devblksize);
if (buf == NULL)
return NULL;
*offset = 0;
}
}
return buf;
}
/*
* 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 compression
* algorithms).
*/
int squashfs_read_data(struct super_block *sb, u64 index, int length,
u64 *next_index, struct squashfs_page_actor *output)
{
struct squashfs_sb_info *msblk = sb->s_fs_info;
char **buf;
int offset = index & ((1 << msblk->devblksize_log2) - 1);
u64 cur_index = index >> msblk->devblksize_log2;
int bytes, compressed, b = 0, k = 0, avail;
buf = calloc(((output->length + msblk->devblksize - 1)
>> msblk->devblksize_log2) + 1, sizeof(*buf));
if (buf == 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, output->length);
if (length < 0 || length > output->length ||
(index + length) > msblk->bytes_used) {
goto read_failure;
}
for (b = 0; bytes < length; b++, cur_index++) {
buf[b] = squashfs_devread(msblk,
cur_index * msblk->devblksize,
msblk->devblksize);
if (buf[b] == NULL)
goto block_release;
bytes += msblk->devblksize;
}
} else {
/*
* Metadata block.
*/
if ((index + 2) > msblk->bytes_used)
goto read_failure;
buf[0] = get_block_length(sb, &cur_index, &offset, &length);
if (buf[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 Meta @ 0x%llx, %scompressed size %d\n", index,
compressed ? "" : "un", length);
if (length < 0 || length > output->length ||
(index + length) > msblk->bytes_used)
goto block_release;
for (; bytes < length; b++) {
buf[b] = squashfs_devread(msblk,
++cur_index * msblk->devblksize,
msblk->devblksize);
if (buf[b] == NULL)
goto block_release;
bytes += msblk->devblksize;
}
}
if (compressed) {
length = squashfs_decompress(msblk, buf, b, offset, length,
output);
if (length < 0)
goto read_failure;
} else {
/*
* Block is uncompressed.
*/
int pg_offset = 0;
void *data = squashfs_first_page(output);
for (bytes = length; k < b; k++) {
int in = min(bytes, msblk->devblksize - offset);
bytes -= in;
while (in) {
if (pg_offset == PAGE_CACHE_SIZE) {
data = squashfs_next_page(output);
pg_offset = 0;
}
avail = min_t(int, in, PAGE_CACHE_SIZE -
pg_offset);
memcpy(data + pg_offset, buf[k] + offset,
avail);
in -= avail;
pg_offset += avail;
offset += avail;
}
offset = 0;
kfree(buf[k]);
}
squashfs_finish_page(output);
}
kfree(buf);
return length;
block_release:
for (; k < b; k++)
kfree(buf[k]);
read_failure:
ERROR("squashfs_read_data failed to read block 0x%llx\n",
(unsigned long long) index);
kfree(buf);
return -EIO;
}
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