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98 lines
3 KiB
C
98 lines
3 KiB
C
/*
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* Squashfs - a compressed read only filesystem for Linux
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*
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* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
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* Phillip Lougher <phillip@lougher.demon.co.uk>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2,
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* or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* fragment.c
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*/
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/*
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* This file implements code to handle compressed fragments (tail-end packed
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* datablocks).
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*
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* Regular files contain a fragment index which is mapped to a fragment
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* location on disk and compressed size using a fragment lookup table.
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* Like everything in Squashfs this fragment lookup table is itself stored
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* compressed into metadata blocks. A second index table is used to locate
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* these. This second index table for speed of access (and because it
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* is small) is read at mount time and cached in memory.
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*/
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#include <linux/fs.h>
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#include <linux/vfs.h>
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#include <linux/slab.h>
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#include <linux/zlib.h>
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#include "squashfs_fs.h"
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#include "squashfs_fs_sb.h"
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#include "squashfs_fs_i.h"
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#include "squashfs.h"
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/*
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* Look-up fragment using the fragment index table. Return the on disk
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* location of the fragment and its compressed size
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*/
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int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment,
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u64 *fragment_block)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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int block = SQUASHFS_FRAGMENT_INDEX(fragment);
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int offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment);
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u64 start_block = le64_to_cpu(msblk->fragment_index[block]);
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struct squashfs_fragment_entry fragment_entry;
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int size;
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size = squashfs_read_metadata(sb, &fragment_entry, &start_block,
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&offset, sizeof(fragment_entry));
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if (size < 0)
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return size;
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*fragment_block = le64_to_cpu(fragment_entry.start_block);
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size = le32_to_cpu(fragment_entry.size);
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return size;
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}
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/*
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* Read the uncompressed fragment lookup table indexes off disk into memory
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*/
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__le64 *squashfs_read_fragment_index_table(struct super_block *sb,
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u64 fragment_table_start, unsigned int fragments)
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{
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unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
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__le64 *fragment_index;
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int err;
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/* Allocate fragment lookup table indexes */
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fragment_index = kmalloc(length, GFP_KERNEL);
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if (fragment_index == NULL) {
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ERROR("Failed to allocate fragment index table\n");
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return ERR_PTR(-ENOMEM);
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}
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err = squashfs_read_table(sb, fragment_index, fragment_table_start,
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length);
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if (err < 0) {
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ERROR("unable to read fragment index table\n");
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kfree(fragment_index);
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return ERR_PTR(err);
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}
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return fragment_index;
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}
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