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 * id.c
22 */
23
24/*
25 * This file implements code to handle uids and gids.
26 *
27 * For space efficiency regular files store uid and gid indexes, which are
28 * converted to 32-bit uids/gids using an id look up table.  This table is
29 * stored compressed into metadata blocks.  A second index table is used to
30 * locate these.  This second index table for speed of access (and because it
31 * is small) is read at mount time and cached in memory.
32 */
33
34#include <linux/fs.h>
35#include <linux/vfs.h>
36#include <linux/slab.h>
37#include <linux/zlib.h>
38
39#include "squashfs_fs.h"
40#include "squashfs_fs_sb.h"
41#include "squashfs_fs_i.h"
42#include "squashfs.h"
43
44/*
45 * Map uid/gid index into real 32-bit uid/gid using the id look up table
46 */
47int squashfs_get_id(struct super_block *sb, unsigned int index,
48					unsigned int *id)
49{
50	struct squashfs_sb_info *msblk = sb->s_fs_info;
51	int block = SQUASHFS_ID_BLOCK(index);
52	int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
53	u64 start_block = le64_to_cpu(msblk->id_table[block]);
54	__le32 disk_id;
55	int err;
56
57	err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
58							sizeof(disk_id));
59	if (err < 0)
60		return err;
61
62	*id = le32_to_cpu(disk_id);
63	return 0;
64}
65
66
67/*
68 * Read uncompressed id lookup table indexes from disk into memory
69 */
70__le64 *squashfs_read_id_index_table(struct super_block *sb,
71			u64 id_table_start, unsigned short no_ids)
72{
73	unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
74	__le64 *id_table;
75	int err;
76
77	TRACE("In read_id_index_table, length %d\n", length);
78
79	/* Allocate id lookup table indexes */
80	id_table = kmalloc(length, GFP_KERNEL);
81	if (id_table == NULL) {
82		ERROR("Failed to allocate id index table\n");
83		return ERR_PTR(-ENOMEM);
84	}
85
86	err = squashfs_read_table(sb, id_table, id_table_start, length);
87	if (err < 0) {
88		ERROR("unable to read id index table\n");
89		kfree(id_table);
90		return ERR_PTR(err);
91	}
92
93	return id_table;
94}
95