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 */
47 int 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
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