busybox/util-linux/volume_id/fat.c
Denys Vlasenko f560422fa0 Big cleanup in config help and description
Redundant help texts (one which only repeats the description)
are deleted.

Descriptions and help texts are trimmed.

Some config options are moved, even across menus.

No config option _names_ are changed.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-01-10 14:58:54 +01:00

346 lines
9.2 KiB
C

/*
* 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
*/
//kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_FAT) += fat.o
//config:config FEATURE_VOLUMEID_FAT
//config: bool "fat filesystem"
//config: default y
//config: depends on VOLUMEID
#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];
} 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];
} PACKED fat32;
} PACKED type;
} 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;
} 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 FAST_FUNC volume_id_probe_vfat(struct volume_id *id /*,uint64_t fat_partition_off*/)
{
#define fat_partition_off ((uint64_t)0)
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 ret;
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 ret;
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) {
uint64_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 = (uint64_t)(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 ret;
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 ret;
/* 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);
ret:
// volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
IF_FEATURE_BLKID_TYPE(id->type = "vfat";)
return 0;
}