[3233] | 1 | /*
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| 2 | * volume_id - reads filesystem label and uuid
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| 3 | *
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| 4 | * Copyright (C) 2012 S-G Bergh <sgb@systemasis.org>
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| 5 | *
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| 6 | * This library is free software; you can redistribute it and/or
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| 7 | * modify it under the terms of the GNU Lesser General Public
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| 8 | * License as published by the Free Software Foundation; either
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| 9 | * version 2.1 of the License, or (at your option) any later version.
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| 10 | *
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| 11 | * This library is distributed in the hope that it will be useful,
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| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 14 | * Lesser General Public License for more details.
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| 15 | *
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| 16 | * You should have received a copy of the GNU Lesser General Public
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| 17 | * License along with this library; if not, write to the Free Software
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| 18 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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| 19 | */
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| 20 |
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| 21 | #include "volume_id_internal.h"
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| 22 |
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| 23 | #define EXFAT_SB_OFFSET 0
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| 24 | #define EXFAT_DIR_ENTRY_SZ 32
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| 25 | #define EXFAT_MAX_DIR_ENTRIES 100
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| 26 |
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| 27 | struct exfat_super_block {
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| 28 | /* 0x00 */ uint8_t boot_jump[3];
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| 29 | /* 0x03 */ uint8_t fs_name[8];
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| 30 | /* 0x0B */ uint8_t must_be_zero[53];
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| 31 | /* 0x40 */ uint64_t partition_offset;
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| 32 | /* 0x48 */ uint64_t volume_length;
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| 33 | /* 0x50 */ uint32_t fat_offset; // Sector address of 1st FAT
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| 34 | /* 0x54 */ uint32_t fat_size; // In sectors
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| 35 | /* 0x58 */ uint32_t cluster_heap_offset; // Sector address of Data Region
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| 36 | /* 0x5C */ uint32_t cluster_count;
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| 37 | /* 0x60 */ uint32_t root_dir; // Cluster address of Root Directory
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| 38 | /* 0x64 */ uint8_t vol_serial_nr[4]; // Volume ID
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| 39 | /* 0x68 */ uint16_t fs_revision; // VV.MM
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| 40 | /* 0x6A */ uint16_t vol_flags;
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| 41 | /* 0x6C */ uint8_t bytes_per_sector; // Power of 2: 9 => 512, 12 => 4096
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| 42 | /* 0x6D */ uint8_t sectors_per_cluster; // Power of 2
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| 43 | /* 0x6E */ uint8_t nr_of_fats; // 2 for TexFAT
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| 44 | /* 0x6F */ // ...
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| 45 | } PACKED;
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| 46 |
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| 47 | struct exfat_dir_entry {
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| 48 | /* 0x00 */ uint8_t entry_type;
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| 49 | union {
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| 50 | struct volume_label {
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| 51 | /* 0x01 */ uint8_t char_count; // Length of label
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| 52 | /* 0x02 */ uint16_t vol_label[11]; // UTF16 string without null termination
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| 53 | /* 0x18 */ uint8_t reserved[8];
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| 54 | /* 0x20 */ } PACKED label;
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| 55 | struct volume_guid {
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| 56 | /* 0x01 */ uint8_t sec_count;
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| 57 | /* 0x02 */ uint16_t set_checksum;
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| 58 | /* 0x04 */ uint16_t flags;
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| 59 | /* 0x06 */ uint8_t vol_guid[16];
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| 60 | /* 0x16 */ uint8_t reserved[10];
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| 61 | /* 0x20 */ } PACKED guid;
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| 62 | } PACKED type;
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| 63 | } PACKED;
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| 64 |
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| 65 | int FAST_FUNC volume_id_probe_exfat(struct volume_id *id /*,uint64_t off*/)
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| 66 | {
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| 67 | struct exfat_super_block *sb;
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| 68 | struct exfat_dir_entry *de;
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| 69 | unsigned sector_sz;
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| 70 | unsigned cluster_sz;
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| 71 | uint64_t root_dir_off;
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| 72 | unsigned count;
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| 73 | unsigned need_lbl_guid;
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| 74 |
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| 75 | // Primary super block
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| 76 | dbg("exFAT: probing at offset 0x%x", EXFAT_SB_OFFSET);
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| 77 | sb = volume_id_get_buffer(id, EXFAT_SB_OFFSET, sizeof(*sb));
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| 78 |
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| 79 | if (!sb)
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| 80 | return -1;
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| 81 |
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| 82 | if (memcmp(sb->fs_name, "EXFAT ", 8) != 0)
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| 83 | return -1;
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| 84 |
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| 85 | sector_sz = 1 << sb->bytes_per_sector;
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| 86 | cluster_sz = sector_sz << sb->sectors_per_cluster;
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| 87 | // There are no clusters 0 and 1, so the first cluster is 2.
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| 88 | root_dir_off = (uint64_t)EXFAT_SB_OFFSET +
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| 89 | // Hmm... should we cast sector_sz/cluster_sz to uint64_t?
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| 90 | (le32_to_cpu(sb->cluster_heap_offset)) * sector_sz +
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| 91 | (le32_to_cpu(sb->root_dir) - 2) * cluster_sz;
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| 92 | dbg("exFAT: sector size 0x%x bytes", sector_sz);
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| 93 | dbg("exFAT: cluster size 0x%x bytes", cluster_sz);
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| 94 | dbg("exFAT: root dir is at 0x%llx", (long long)root_dir_off);
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| 95 |
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| 96 | // Use DOS uuid as fallback, if no GUID set
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| 97 | volume_id_set_uuid(id, sb->vol_serial_nr, UUID_DOS);
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| 98 |
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| 99 | // EXFAT_MAX_DIR_ENTRIES is used as a safety belt.
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| 100 | // The Root Directory may hold an unlimited number of entries,
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| 101 | // so we do not want to check all. Usually label and GUID
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| 102 | // are in the beginning, but there are no guarantees.
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| 103 | need_lbl_guid = (1 << 0) | (1 << 1);
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| 104 | for (count = 0; count < EXFAT_MAX_DIR_ENTRIES; count++) {
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| 105 | de = volume_id_get_buffer(id, root_dir_off + (count * EXFAT_DIR_ENTRY_SZ), EXFAT_DIR_ENTRY_SZ);
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| 106 | if (de == NULL)
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| 107 | break;
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| 108 | if (de->entry_type == 0x00) {
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| 109 | // End of Directory Marker
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| 110 | dbg("exFAT: End of root directory reached after %u entries", count);
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| 111 | break;
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| 112 | }
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| 113 | if (de->entry_type == 0x83) {
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| 114 | // Volume Label Directory Entry
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| 115 | volume_id_set_label_unicode16(id, (uint8_t *)de->type.label.vol_label,
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| 116 | LE, 2 * de->type.label.char_count);
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| 117 | need_lbl_guid &= ~(1 << 0);
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| 118 | }
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| 119 | if (de->entry_type == 0xA0) {
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| 120 | // Volume GUID Directory Entry
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| 121 | volume_id_set_uuid(id, de->type.guid.vol_guid, UUID_DCE);
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| 122 | need_lbl_guid &= ~(1 << 1);
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| 123 | }
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| 124 | if (!need_lbl_guid)
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| 125 | break;
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| 126 | }
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| 127 |
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| 128 | IF_FEATURE_BLKID_TYPE(id->type = "exfat";)
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| 129 | return 0;
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| 130 | }
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