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333 lines
9.1 KiB
C
333 lines
9.1 KiB
C
/*
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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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/* linux/msdos_fs.h says: */
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#define FAT12_MAX 0xff4
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#define FAT16_MAX 0xfff4
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#define FAT32_MAX 0x0ffffff6
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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_bytes;
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uint8_t sectors_per_cluster;
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uint16_t reserved_sct;
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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, int count)
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{
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for (;--count >= 0; dir++) {
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/* end marker */
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if (dir->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->name[0] == FAT_ENTRY_FREE)
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continue;
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/* long name */
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if ((dir->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
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continue;
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if ((dir->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->cluster_high != 0 || dir->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->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 fat_partition_off*/)
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{
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#define fat_partition_off ((uint64_t)0)
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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_bytes;
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uint16_t dir_entries;
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uint32_t sect_count;
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uint16_t reserved_sct;
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uint32_t fat_size_sct;
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uint32_t root_cluster;
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uint32_t dir_size_sct;
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uint32_t cluster_count;
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uint64_t root_start_off;
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uint32_t start_data_sct;
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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_cluster;
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int maxloop;
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dbg("probing at offset 0x%llx", (unsigned long long) fat_partition_off);
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vs = volume_id_get_buffer(id, fat_partition_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_bytes = le16_to_cpu(vs->sector_size_bytes);
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if (sector_size_bytes != 0x200 && sector_size_bytes != 0x400 &&
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sector_size_bytes != 0x800 && sector_size_bytes != 0x1000)
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return -1;
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dbg("sector_size_bytes 0x%x", sector_size_bytes);
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dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
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reserved_sct = le16_to_cpu(vs->reserved_sct);
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dbg("reserved_sct 0x%x", reserved_sct);
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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_size_sct = le16_to_cpu(vs->fat_length);
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if (fat_size_sct == 0)
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fat_size_sct = le32_to_cpu(vs->type.fat32.fat32_length);
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fat_size_sct *= vs->fats;
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dbg("fat_size_sct 0x%x", fat_size_sct);
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dir_entries = le16_to_cpu(vs->dir_entries);
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dir_size_sct = ((dir_entries * sizeof(struct vfat_dir_entry)) +
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(sector_size_bytes-1)) / sector_size_bytes;
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dbg("dir_size_sct 0x%x", dir_size_sct);
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cluster_count = sect_count - (reserved_sct + fat_size_sct + dir_size_sct);
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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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if (cluster_count >= FAT16_MAX)
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goto fat32;
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/* the label may be an attribute in the root directory */
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root_start_off = (reserved_sct + fat_size_sct) * sector_size_bytes;
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dbg("root dir start 0x%llx", (unsigned long long) root_start_off);
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dbg("expected entries 0x%x", dir_entries);
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buf_size = dir_entries * sizeof(struct vfat_dir_entry);
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buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size);
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if (buf == NULL)
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goto ret;
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label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries);
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vs = volume_id_get_buffer(id, fat_partition_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 ret;
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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_bytes;
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root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
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start_data_sct = reserved_sct + fat_size_sct;
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next_cluster = root_cluster;
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maxloop = 100;
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while (--maxloop) {
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uint64_t next_off_sct;
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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 0x%x", (unsigned)next_cluster);
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next_off_sct = (uint64_t)(next_cluster - 2) * vs->sectors_per_cluster;
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next_off = (start_data_sct + next_off_sct) * sector_size_bytes;
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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, fat_partition_off + next_off, buf_size);
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if (buf == NULL)
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goto ret;
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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_sct * sector_size_bytes) + (next_cluster * sizeof(uint32_t));
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dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off);
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buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size);
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if (buf == NULL)
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goto ret;
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/* set next cluster */
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next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff;
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if (next_cluster < 2 || next_cluster > FAT32_MAX)
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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, fat_partition_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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ret:
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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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