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