/* * volume_id - reads filesystem label and uuid * * Copyright (C) 2012 S-G Bergh <sgb@systemasis.org> * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ //kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_EXFAT) += exfat.o //config: //config:config FEATURE_VOLUMEID_EXFAT //config: bool "exFAT filesystem" //config: default y //config: depends on VOLUMEID //config: help //config: exFAT (extended FAT) is a proprietary file system designed especially //config: for flash drives. It has many features from NTFS, but with less //config: overhead. exFAT is used on most SDXC cards for consumer electronics. //config: #include "volume_id_internal.h" #define EXFAT_SB_OFFSET 0 #define EXFAT_DIR_ENTRY_SZ 32 #define EXFAT_MAX_DIR_ENTRIES 100 struct exfat_super_block { /* 0x00 */ uint8_t boot_jump[3]; /* 0x03 */ uint8_t fs_name[8]; /* 0x0B */ uint8_t must_be_zero[53]; /* 0x40 */ uint64_t partition_offset; /* 0x48 */ uint64_t volume_length; /* 0x50 */ uint32_t fat_offset; // Sector address of 1st FAT /* 0x54 */ uint32_t fat_size; // In sectors /* 0x58 */ uint32_t cluster_heap_offset; // Sector address of Data Region /* 0x5C */ uint32_t cluster_count; /* 0x60 */ uint32_t root_dir; // Cluster address of Root Directory /* 0x64 */ uint8_t vol_serial_nr[4]; // Volume ID /* 0x68 */ uint16_t fs_revision; // VV.MM /* 0x6A */ uint16_t vol_flags; /* 0x6C */ uint8_t bytes_per_sector; // Power of 2: 9 => 512, 12 => 4096 /* 0x6D */ uint8_t sectors_per_cluster; // Power of 2 /* 0x6E */ uint8_t nr_of_fats; // 2 for TexFAT /* 0x6F */ // ... } PACKED; struct exfat_dir_entry { /* 0x00 */ uint8_t entry_type; union { struct volume_label { /* 0x01 */ uint8_t char_count; // Length of label /* 0x02 */ uint16_t vol_label[11]; // UTF16 string without null termination /* 0x18 */ uint8_t reserved[8]; /* 0x20 */ } PACKED label; struct volume_guid { /* 0x01 */ uint8_t sec_count; /* 0x02 */ uint16_t set_checksum; /* 0x04 */ uint16_t flags; /* 0x06 */ uint8_t vol_guid[16]; /* 0x16 */ uint8_t reserved[10]; /* 0x20 */ } PACKED guid; } PACKED type; } PACKED; int FAST_FUNC volume_id_probe_exfat(struct volume_id *id /*,uint64_t off*/) { struct exfat_super_block *sb; struct exfat_dir_entry *de; unsigned sector_sz; unsigned cluster_sz; uint64_t root_dir_off; unsigned count; unsigned need_lbl_guid; // Primary super block dbg("exFAT: probing at offset 0x%x", EXFAT_SB_OFFSET); sb = volume_id_get_buffer(id, EXFAT_SB_OFFSET, sizeof(*sb)); if (!sb) return -1; if (memcmp(sb->fs_name, "EXFAT ", 8) != 0) return -1; sector_sz = 1 << sb->bytes_per_sector; cluster_sz = sector_sz << sb->sectors_per_cluster; // There are no clusters 0 and 1, so the first cluster is 2. root_dir_off = (uint64_t)EXFAT_SB_OFFSET + // Hmm... should we cast sector_sz/cluster_sz to uint64_t? (le32_to_cpu(sb->cluster_heap_offset)) * sector_sz + (le32_to_cpu(sb->root_dir) - 2) * cluster_sz; dbg("exFAT: sector size 0x%x bytes", sector_sz); dbg("exFAT: cluster size 0x%x bytes", cluster_sz); dbg("exFAT: root dir is at 0x%llx", (long long)root_dir_off); // Use DOS uuid as fallback, if no GUID set volume_id_set_uuid(id, sb->vol_serial_nr, UUID_DOS); // EXFAT_MAX_DIR_ENTRIES is used as a safety belt. // The Root Directory may hold an unlimited number of entries, // so we do not want to check all. Usually label and GUID // are in the beginning, but there are no guarantees. need_lbl_guid = (1 << 0) | (1 << 1); for (count = 0; count < EXFAT_MAX_DIR_ENTRIES; count++) { de = volume_id_get_buffer(id, root_dir_off + (count * EXFAT_DIR_ENTRY_SZ), EXFAT_DIR_ENTRY_SZ); if (de == NULL) break; if (de->entry_type == 0x00) { // End of Directory Marker dbg("exFAT: End of root directory reached after %u entries", count); break; } if (de->entry_type == 0x83) { // Volume Label Directory Entry volume_id_set_label_unicode16(id, (uint8_t *)de->type.label.vol_label, LE, 2 * de->type.label.char_count); need_lbl_guid &= ~(1 << 0); } if (de->entry_type == 0xA0) { // Volume GUID Directory Entry volume_id_set_uuid(id, de->type.guid.vol_guid, UUID_DCE); need_lbl_guid &= ~(1 << 1); } if (!need_lbl_guid) break; } IF_FEATURE_BLKID_TYPE(id->type = "exfat";) return 0; }