334 lines
8.7 KiB
C
334 lines
8.7 KiB
C
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/*
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* volume_id - reads filesystem label and uuid
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*
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* Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include "volume_id_internal.h"
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#define FAT12_MAX 0xff5
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#define FAT16_MAX 0xfff5
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#define FAT_ATTR_VOLUME_ID 0x08
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#define FAT_ATTR_DIR 0x10
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#define FAT_ATTR_LONG_NAME 0x0f
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#define FAT_ATTR_MASK 0x3f
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#define FAT_ENTRY_FREE 0xe5
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struct vfat_super_block {
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uint8_t boot_jump[3];
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uint8_t sysid[8];
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uint16_t sector_size;
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uint8_t sectors_per_cluster;
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uint16_t reserved;
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uint8_t fats;
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uint16_t dir_entries;
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uint16_t sectors;
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uint8_t media;
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uint16_t fat_length;
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uint16_t secs_track;
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uint16_t heads;
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uint32_t hidden;
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uint32_t total_sect;
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union {
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struct fat_super_block {
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uint8_t unknown[3];
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uint8_t serno[4];
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uint8_t label[11];
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uint8_t magic[8];
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uint8_t dummy2[192];
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uint8_t pmagic[2];
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} __attribute__((__packed__)) fat;
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struct fat32_super_block {
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uint32_t fat32_length;
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uint16_t flags;
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uint8_t version[2];
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uint32_t root_cluster;
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uint16_t insfo_sector;
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uint16_t backup_boot;
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uint16_t reserved2[6];
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uint8_t unknown[3];
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uint8_t serno[4];
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uint8_t label[11];
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uint8_t magic[8];
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uint8_t dummy2[164];
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uint8_t pmagic[2];
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} __attribute__((__packed__)) fat32;
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} __attribute__((__packed__)) type;
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} __attribute__((__packed__));
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struct vfat_dir_entry {
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uint8_t name[11];
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uint8_t attr;
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uint16_t time_creat;
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uint16_t date_creat;
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uint16_t time_acc;
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uint16_t date_acc;
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uint16_t cluster_high;
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uint16_t time_write;
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uint16_t date_write;
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uint16_t cluster_low;
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uint32_t size;
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} __attribute__((__packed__));
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static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned count)
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{
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unsigned i;
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for (i = 0; i < count; i++) {
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/* end marker */
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if (dir[i].name[0] == 0x00) {
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dbg("end of dir");
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break;
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}
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/* empty entry */
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if (dir[i].name[0] == FAT_ENTRY_FREE)
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continue;
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/* long name */
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if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
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continue;
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if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
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/* labels do not have file data */
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if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
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continue;
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dbg("found ATTR_VOLUME_ID id in root dir");
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return dir[i].name;
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}
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dbg("skip dir entry");
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}
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return NULL;
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}
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int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
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{
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struct vfat_super_block *vs;
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struct vfat_dir_entry *dir;
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uint16_t sector_size;
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uint16_t dir_entries;
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uint32_t sect_count;
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uint16_t reserved;
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uint32_t fat_size;
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uint32_t root_cluster;
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uint32_t dir_size;
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uint32_t cluster_count;
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uint32_t fat_length;
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uint64_t root_start;
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uint32_t start_data_sect;
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uint16_t root_dir_entries;
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uint8_t *buf;
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uint32_t buf_size;
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uint8_t *label = NULL;
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uint32_t next;
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int maxloop;
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dbg("probing at offset 0x%llx", (unsigned long long) off);
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vs = volume_id_get_buffer(id, off, 0x200);
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if (vs == NULL)
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return -1;
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/* believe only that's fat, don't trust the version
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* the cluster_count will tell us
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*/
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if (memcmp(vs->sysid, "NTFS", 4) == 0)
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return -1;
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if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
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goto valid;
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if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
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goto valid;
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if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
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goto valid;
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if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
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goto valid;
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if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
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goto valid;
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/*
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* There are old floppies out there without a magic, so we check
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* for well known values and guess if it's a fat volume
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*/
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/* boot jump address check */
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if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
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vs->boot_jump[0] != 0xe9)
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return -1;
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/* heads check */
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if (vs->heads == 0)
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return -1;
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/* cluster size check*/
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if (vs->sectors_per_cluster == 0 ||
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(vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
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return -1;
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/* media check */
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if (vs->media < 0xf8 && vs->media != 0xf0)
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return -1;
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/* fat count*/
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if (vs->fats != 2)
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return -1;
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valid:
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/* sector size check */
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sector_size = le16_to_cpu(vs->sector_size);
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if (sector_size != 0x200 && sector_size != 0x400 &&
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sector_size != 0x800 && sector_size != 0x1000)
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return -1;
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dbg("sector_size 0x%x", sector_size);
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dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
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dir_entries = le16_to_cpu(vs->dir_entries);
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reserved = le16_to_cpu(vs->reserved);
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dbg("reserved 0x%x", reserved);
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sect_count = le16_to_cpu(vs->sectors);
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if (sect_count == 0)
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sect_count = le32_to_cpu(vs->total_sect);
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dbg("sect_count 0x%x", sect_count);
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fat_length = le16_to_cpu(vs->fat_length);
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if (fat_length == 0)
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fat_length = le32_to_cpu(vs->type.fat32.fat32_length);
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dbg("fat_length 0x%x", fat_length);
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fat_size = fat_length * vs->fats;
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dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
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(sector_size-1)) / sector_size;
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dbg("dir_size 0x%x", dir_size);
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cluster_count = sect_count - (reserved + fat_size + dir_size);
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cluster_count /= vs->sectors_per_cluster;
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dbg("cluster_count 0x%x", cluster_count);
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if (cluster_count < FAT12_MAX) {
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strcpy(id->type_version, "FAT12");
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} else if (cluster_count < FAT16_MAX) {
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strcpy(id->type_version, "FAT16");
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} else {
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strcpy(id->type_version, "FAT32");
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goto fat32;
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}
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/* the label may be an attribute in the root directory */
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root_start = (reserved + fat_size) * sector_size;
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dbg("root dir start 0x%llx", (unsigned long long) root_start);
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root_dir_entries = le16_to_cpu(vs->dir_entries);
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dbg("expected entries 0x%x", root_dir_entries);
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buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
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buf = volume_id_get_buffer(id, off + root_start, buf_size);
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if (buf == NULL)
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goto found;
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dir = (struct vfat_dir_entry*) buf;
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label = get_attr_volume_id(dir, root_dir_entries);
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vs = volume_id_get_buffer(id, off, 0x200);
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if (vs == NULL)
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return -1;
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if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
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volume_id_set_label_raw(id, label, 11);
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volume_id_set_label_string(id, label, 11);
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} else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
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volume_id_set_label_raw(id, vs->type.fat.label, 11);
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volume_id_set_label_string(id, vs->type.fat.label, 11);
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}
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volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
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goto found;
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fat32:
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/* FAT32 root dir is a cluster chain like any other directory */
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buf_size = vs->sectors_per_cluster * sector_size;
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root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
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dbg("root dir cluster %u", root_cluster);
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start_data_sect = reserved + fat_size;
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next = root_cluster;
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maxloop = 100;
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while (--maxloop) {
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uint32_t next_sect_off;
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uint64_t next_off;
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uint64_t fat_entry_off;
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int count;
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dbg("next cluster %u", next);
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next_sect_off = (next - 2) * vs->sectors_per_cluster;
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next_off = (start_data_sect + next_sect_off) * sector_size;
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dbg("cluster offset 0x%llx", (unsigned long long) next_off);
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/* get cluster */
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buf = volume_id_get_buffer(id, off + next_off, buf_size);
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if (buf == NULL)
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goto found;
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dir = (struct vfat_dir_entry*) buf;
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count = buf_size / sizeof(struct vfat_dir_entry);
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dbg("expected entries 0x%x", count);
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label = get_attr_volume_id(dir, count);
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if (label)
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break;
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/* get FAT entry */
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fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
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buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
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if (buf == NULL)
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goto found;
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/* set next cluster */
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next = le32_to_cpu(*((uint32_t *) buf) & 0x0fffffff);
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if (next == 0)
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break;
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}
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if (maxloop == 0)
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dbg("reached maximum follow count of root cluster chain, give up");
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vs = volume_id_get_buffer(id, off, 0x200);
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if (vs == NULL)
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return -1;
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if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
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volume_id_set_label_raw(id, label, 11);
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volume_id_set_label_string(id, label, 11);
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} else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
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volume_id_set_label_raw(id, vs->type.fat32.label, 11);
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volume_id_set_label_string(id, vs->type.fat32.label, 11);
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}
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volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
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found:
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volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
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id->type = "vfat";
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return 0;
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}
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