diff options
Diffstat (limited to 'util-linux/volume_id/fat.c')
| -rw-r--r-- | util-linux/volume_id/fat.c | 331 |
1 files changed, 331 insertions, 0 deletions
diff --git a/util-linux/volume_id/fat.c b/util-linux/volume_id/fat.c new file mode 100644 index 0000000..816d69d --- /dev/null +++ b/util-linux/volume_id/fat.c @@ -0,0 +1,331 @@ +/* + * volume_id - reads filesystem label and uuid + * + * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.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 + */ + +#include "volume_id_internal.h" + +/* linux/msdos_fs.h says: */ +#define FAT12_MAX 0xff4 +#define FAT16_MAX 0xfff4 +#define FAT32_MAX 0x0ffffff6 + +#define FAT_ATTR_VOLUME_ID 0x08 +#define FAT_ATTR_DIR 0x10 +#define FAT_ATTR_LONG_NAME 0x0f +#define FAT_ATTR_MASK 0x3f +#define FAT_ENTRY_FREE 0xe5 + +struct vfat_super_block { + uint8_t boot_jump[3]; + uint8_t sysid[8]; + uint16_t sector_size_bytes; + uint8_t sectors_per_cluster; + uint16_t reserved_sct; + uint8_t fats; + uint16_t dir_entries; + uint16_t sectors; + uint8_t media; + uint16_t fat_length; + uint16_t secs_track; + uint16_t heads; + uint32_t hidden; + uint32_t total_sect; + union { + struct fat_super_block { + uint8_t unknown[3]; + uint8_t serno[4]; + uint8_t label[11]; + uint8_t magic[8]; + uint8_t dummy2[192]; + uint8_t pmagic[2]; + } __attribute__((__packed__)) fat; + struct fat32_super_block { + uint32_t fat32_length; + uint16_t flags; + uint8_t version[2]; + uint32_t root_cluster; + uint16_t insfo_sector; + uint16_t backup_boot; + uint16_t reserved2[6]; + uint8_t unknown[3]; + uint8_t serno[4]; + uint8_t label[11]; + uint8_t magic[8]; + uint8_t dummy2[164]; + uint8_t pmagic[2]; + } __attribute__((__packed__)) fat32; + } __attribute__((__packed__)) type; +} __attribute__((__packed__)); + +struct vfat_dir_entry { + uint8_t name[11]; + uint8_t attr; + uint16_t time_creat; + uint16_t date_creat; + uint16_t time_acc; + uint16_t date_acc; + uint16_t cluster_high; + uint16_t time_write; + uint16_t date_write; + uint16_t cluster_low; + uint32_t size; +} __attribute__((__packed__)); + +static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, int count) +{ + for (;--count >= 0; dir++) { + /* end marker */ + if (dir->name[0] == 0x00) { + dbg("end of dir"); + break; + } + + /* empty entry */ + if (dir->name[0] == FAT_ENTRY_FREE) + continue; + + /* long name */ + if ((dir->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME) + continue; + + if ((dir->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) { + /* labels do not have file data */ + if (dir->cluster_high != 0 || dir->cluster_low != 0) + continue; + + dbg("found ATTR_VOLUME_ID id in root dir"); + return dir->name; + } + + dbg("skip dir entry"); + } + + return NULL; +} + +int volume_id_probe_vfat(struct volume_id *id, uint64_t fat_partition_off) +{ + struct vfat_super_block *vs; + struct vfat_dir_entry *dir; + uint16_t sector_size_bytes; + uint16_t dir_entries; + uint32_t sect_count; + uint16_t reserved_sct; + uint32_t fat_size_sct; + uint32_t root_cluster; + uint32_t dir_size_sct; + uint32_t cluster_count; + uint64_t root_start_off; + uint32_t start_data_sct; + uint8_t *buf; + uint32_t buf_size; + uint8_t *label = NULL; + uint32_t next_cluster; + int maxloop; + + dbg("probing at offset 0x%llx", (unsigned long long) fat_partition_off); + + vs = volume_id_get_buffer(id, fat_partition_off, 0x200); + if (vs == NULL) + return -1; + + /* believe only that's fat, don't trust the version + * the cluster_count will tell us + */ + if (memcmp(vs->sysid, "NTFS", 4) == 0) + return -1; + + if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0) + goto valid; + + if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0) + goto valid; + + if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0) + goto valid; + + if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0) + goto valid; + + if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0) + goto valid; + + /* + * There are old floppies out there without a magic, so we check + * for well known values and guess if it's a fat volume + */ + + /* boot jump address check */ + if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) && + vs->boot_jump[0] != 0xe9) + return -1; + + /* heads check */ + if (vs->heads == 0) + return -1; + + /* cluster size check */ + if (vs->sectors_per_cluster == 0 || + (vs->sectors_per_cluster & (vs->sectors_per_cluster-1))) + return -1; + + /* media check */ + if (vs->media < 0xf8 && vs->media != 0xf0) + return -1; + + /* fat count*/ + if (vs->fats != 2) + return -1; + + valid: + /* sector size check */ + sector_size_bytes = le16_to_cpu(vs->sector_size_bytes); + if (sector_size_bytes != 0x200 && sector_size_bytes != 0x400 && + sector_size_bytes != 0x800 && sector_size_bytes != 0x1000) + return -1; + + dbg("sector_size_bytes 0x%x", sector_size_bytes); + dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster); + + reserved_sct = le16_to_cpu(vs->reserved_sct); + dbg("reserved_sct 0x%x", reserved_sct); + + sect_count = le16_to_cpu(vs->sectors); + if (sect_count == 0) + sect_count = le32_to_cpu(vs->total_sect); + dbg("sect_count 0x%x", sect_count); + + fat_size_sct = le16_to_cpu(vs->fat_length); + if (fat_size_sct == 0) + fat_size_sct = le32_to_cpu(vs->type.fat32.fat32_length); + fat_size_sct *= vs->fats; + dbg("fat_size_sct 0x%x", fat_size_sct); + + dir_entries = le16_to_cpu(vs->dir_entries); + dir_size_sct = ((dir_entries * sizeof(struct vfat_dir_entry)) + + (sector_size_bytes-1)) / sector_size_bytes; + dbg("dir_size_sct 0x%x", dir_size_sct); + + cluster_count = sect_count - (reserved_sct + fat_size_sct + dir_size_sct); + cluster_count /= vs->sectors_per_cluster; + dbg("cluster_count 0x%x", cluster_count); + +// if (cluster_count < FAT12_MAX) { +// strcpy(id->type_version, "FAT12"); +// } else if (cluster_count < FAT16_MAX) { +// strcpy(id->type_version, "FAT16"); +// } else { +// strcpy(id->type_version, "FAT32"); +// goto fat32; +// } + if (cluster_count >= FAT16_MAX) + goto fat32; + + /* the label may be an attribute in the root directory */ + root_start_off = (reserved_sct + fat_size_sct) * sector_size_bytes; + dbg("root dir start 0x%llx", (unsigned long long) root_start_off); + dbg("expected entries 0x%x", dir_entries); + + buf_size = dir_entries * sizeof(struct vfat_dir_entry); + buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size); + if (buf == NULL) + goto found; + + label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries); + + vs = volume_id_get_buffer(id, fat_partition_off, 0x200); + if (vs == NULL) + return -1; + + if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) { +// volume_id_set_label_raw(id, label, 11); + volume_id_set_label_string(id, label, 11); + } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) { +// volume_id_set_label_raw(id, vs->type.fat.label, 11); + volume_id_set_label_string(id, vs->type.fat.label, 11); + } + volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS); + goto found; + + fat32: + /* FAT32 root dir is a cluster chain like any other directory */ + buf_size = vs->sectors_per_cluster * sector_size_bytes; + root_cluster = le32_to_cpu(vs->type.fat32.root_cluster); + start_data_sct = reserved_sct + fat_size_sct; + + next_cluster = root_cluster; + maxloop = 100; + while (--maxloop) { + uint32_t next_off_sct; + uint64_t next_off; + uint64_t fat_entry_off; + int count; + + dbg("next_cluster 0x%x", (unsigned)next_cluster); + next_off_sct = (next_cluster - 2) * vs->sectors_per_cluster; + next_off = (start_data_sct + next_off_sct) * sector_size_bytes; + dbg("cluster offset 0x%llx", (unsigned long long) next_off); + + /* get cluster */ + buf = volume_id_get_buffer(id, fat_partition_off + next_off, buf_size); + if (buf == NULL) + goto found; + + dir = (struct vfat_dir_entry*) buf; + count = buf_size / sizeof(struct vfat_dir_entry); + dbg("expected entries 0x%x", count); + + label = get_attr_volume_id(dir, count); + if (label) + break; + + /* get FAT entry */ + fat_entry_off = (reserved_sct * sector_size_bytes) + (next_cluster * sizeof(uint32_t)); + dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off); + buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size); + if (buf == NULL) + goto found; + + /* set next cluster */ + next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff; + if (next_cluster < 2 || next_cluster > FAT32_MAX) + break; + } + if (maxloop == 0) + dbg("reached maximum follow count of root cluster chain, give up"); + + vs = volume_id_get_buffer(id, fat_partition_off, 0x200); + if (vs == NULL) + return -1; + + if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) { +// volume_id_set_label_raw(id, label, 11); + volume_id_set_label_string(id, label, 11); + } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) { +// volume_id_set_label_raw(id, vs->type.fat32.label, 11); + volume_id_set_label_string(id, vs->type.fat32.label, 11); + } + volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS); + + found: +// volume_id_set_usage(id, VOLUME_ID_FILESYSTEM); +// id->type = "vfat"; + + return 0; +} |