95 lines
2.7 KiB
C
95 lines
2.7 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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* id.c
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*/
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/*
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* This file implements code to handle uids and gids.
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*
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* For space efficiency regular files store uid and gid indexes, which are
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* converted to 32-bit uids/gids using an id look up table. This table is
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* stored compressed into metadata blocks. A second index table is used to
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* locate 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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* Map uid/gid index into real 32-bit uid/gid using the id look up table
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*/
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int squashfs_get_id(struct super_block *sb, unsigned int index,
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unsigned int *id)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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int block = SQUASHFS_ID_BLOCK(index);
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int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
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u64 start_block = le64_to_cpu(msblk->id_table[block]);
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__le32 disk_id;
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int err;
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err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
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sizeof(disk_id));
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if (err < 0)
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return err;
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*id = le32_to_cpu(disk_id);
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return 0;
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}
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/*
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* Read uncompressed id lookup table indexes from disk into memory
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*/
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__le64 *squashfs_read_id_index_table(struct super_block *sb,
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u64 id_table_start, unsigned short no_ids)
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{
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unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
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__le64 *id_table;
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int err;
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TRACE("In read_id_index_table, length %d\n", length);
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/* Allocate id lookup table indexes */
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id_table = kmalloc(length, GFP_KERNEL);
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if (id_table == NULL) {
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ERROR("Failed to allocate id index table\n");
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return ERR_PTR(-ENOMEM);
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}
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err = squashfs_read_table(sb, id_table, id_table_start, length);
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if (err < 0) {
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ERROR("unable to read id index table\n");
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kfree(id_table);
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return ERR_PTR(err);
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}
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return id_table;
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}
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