LXR busybox/util-linux/volume

   1/*
   2 * volume_id - reads filesystem label and uuid
   3 *
   4 * Copyright (C) 2012 S-G Bergh <sgb@systemasis.org>
   5 *
   6 *      This library is free software; you can redistribute it and/or
   7 *      modify it under the terms of the GNU Lesser General Public
   8 *      License as published by the Free Software Foundation; either
   9 *      version 2.1 of the License, or (at your option) any later version.
  10 *
  11 *      This library is distributed in the hope that it will be useful,
  12 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14 *      Lesser General Public License for more details.
  15 *
  16 *      You should have received a copy of the GNU Lesser General Public
  17 *      License along with this library; if not, write to the Free Software
  18 *      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  19 */
  20
  21#include "volume_id_internal.h"
  22
  23#define EXFAT_SB_OFFSET         0
  24#define EXFAT_DIR_ENTRY_SZ      32
  25#define EXFAT_MAX_DIR_ENTRIES   100
  26
  27struct exfat_super_block {
  28/* 0x00 */      uint8_t         boot_jump[3];
  29/* 0x03 */      uint8_t         fs_name[8];
  30/* 0x0B */      uint8_t         must_be_zero[53];
  31/* 0x40 */      uint64_t        partition_offset;
  32/* 0x48 */      uint64_t        volume_length;
  33/* 0x50 */      uint32_t        fat_offset;             // Sector address of 1st FAT
  34/* 0x54 */      uint32_t        fat_size;               // In sectors
  35/* 0x58 */      uint32_t        cluster_heap_offset;    // Sector address of Data Region
  36/* 0x5C */      uint32_t        cluster_count;
  37/* 0x60 */      uint32_t        root_dir;               // Cluster address of Root Directory
  38/* 0x64 */      uint8_t         vol_serial_nr[4];       // Volume ID
  39/* 0x68 */      uint16_t        fs_revision;            // VV.MM
  40/* 0x6A */      uint16_t        vol_flags;
  41/* 0x6C */      uint8_t         bytes_per_sector;       // Power of 2: 9 => 512, 12 => 4096
  42/* 0x6D */      uint8_t         sectors_per_cluster;    // Power of 2
  43/* 0x6E */      uint8_t         nr_of_fats;             // 2 for TexFAT
  44/* 0x6F */      // ...
  45} PACKED;
  46
  47struct exfat_dir_entry {
  48/* 0x00 */      uint8_t         entry_type;
  49                union {
  50                        struct volume_label {
  51/* 0x01 */                      uint8_t         char_count;             // Length of label
  52/* 0x02 */                      uint16_t        vol_label[11];          // UTF16 string without null termination
  53/* 0x18 */                      uint8_t         reserved[8];
  54/* 0x20 */              } PACKED label;
  55                        struct volume_guid {
  56/* 0x01 */                      uint8_t         sec_count;
  57/* 0x02 */                      uint16_t        set_checksum;
  58/* 0x04 */                      uint16_t        flags;
  59/* 0x06 */                      uint8_t         vol_guid[16];
  60/* 0x16 */                      uint8_t         reserved[10];
  61/* 0x20 */              } PACKED guid;
  62                } PACKED type;
  63} PACKED;
  64
  65int FAST_FUNC volume_id_probe_exfat(struct volume_id *id /*,uint64_t off*/)
  66{
  67        struct exfat_super_block *sb;
  68        struct exfat_dir_entry *de;
  69        unsigned        sector_sz;
  70        unsigned        cluster_sz;
  71        uint64_t        root_dir_off;
  72        unsigned        count;
  73        unsigned        need_lbl_guid;
  74
  75        // Primary super block
  76        dbg("exFAT: probing at offset 0x%x", EXFAT_SB_OFFSET);
  77        sb = volume_id_get_buffer(id, EXFAT_SB_OFFSET, sizeof(*sb));
  78
  79        if (!sb)
  80                return -1;
  81
  82        if (memcmp(sb->fs_name, "EXFAT   ", 8) != 0)
  83                return -1;
  84
  85        sector_sz = 1 << sb->bytes_per_sector;
  86        cluster_sz = sector_sz << sb->sectors_per_cluster;
  87        // There are no clusters 0 and 1, so the first cluster is 2.
  88        root_dir_off = (uint64_t)EXFAT_SB_OFFSET +
  89                // Hmm... should we cast sector_sz/cluster_sz to uint64_t?
  90                (le32_to_cpu(sb->cluster_heap_offset)) * sector_sz +
  91                (le32_to_cpu(sb->root_dir) - 2) * cluster_sz;
  92        dbg("exFAT: sector size 0x%x bytes", sector_sz);
  93        dbg("exFAT: cluster size 0x%x bytes", cluster_sz);
  94        dbg("exFAT: root dir is at 0x%llx", (long long)root_dir_off);
  95
  96        // Use DOS uuid as fallback, if no GUID set
  97        volume_id_set_uuid(id, sb->vol_serial_nr, UUID_DOS);
  98
  99        // EXFAT_MAX_DIR_ENTRIES is used as a safety belt.
 100        // The Root Directory may hold an unlimited number of entries,
 101        // so we do not want to check all. Usually label and GUID
 102        // are in the beginning, but there are no guarantees.
 103        need_lbl_guid = (1 << 0) | (1 << 1);
 104        for (count = 0; count < EXFAT_MAX_DIR_ENTRIES; count++) {
 105                de = volume_id_get_buffer(id, root_dir_off + (count * EXFAT_DIR_ENTRY_SZ), EXFAT_DIR_ENTRY_SZ);
 106                if (de == NULL)
 107                        break;
 108                if (de->entry_type == 0x00) {
 109                        // End of Directory Marker
 110                        dbg("exFAT: End of root directory reached after %u entries", count);
 111                        break;
 112                }
 113                if (de->entry_type == 0x83) {
 114                        // Volume Label Directory Entry
 115                        volume_id_set_label_unicode16(id, (uint8_t *)de->type.label.vol_label,
 116                                                LE, 2 * de->type.label.char_count);
 117                        need_lbl_guid &= ~(1 << 0);
 118                }
 119                if (de->entry_type == 0xA0) {
 120                        // Volume GUID Directory Entry
 121                        volume_id_set_uuid(id, de->type.guid.vol_guid, UUID_DCE);
 122                        need_lbl_guid &= ~(1 << 1);
 123                }
 124                if (!need_lbl_guid)
 125                        break;
 126        }
 127
 128        IF_FEATURE_BLKID_TYPE(id->type = "exfat";)
 129        return 0;
 130}
 131