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8256c8f6 PL |
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 | } |