2 * volume_id - reads filesystem label and uuid
4 * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 //kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_FAT) += fat.o
23 //config:config FEATURE_VOLUMEID_FAT
24 //config: bool "fat filesystem"
26 //config: depends on VOLUMEID
28 #include "volume_id_internal.h"
30 /* linux/msdos_fs.h says: */
31 #define FAT12_MAX 0xff4
32 #define FAT16_MAX 0xfff4
33 #define FAT32_MAX 0x0ffffff6
35 #define FAT_ATTR_VOLUME_ID 0x08
36 #define FAT_ATTR_DIR 0x10
37 #define FAT_ATTR_LONG_NAME 0x0f
38 #define FAT_ATTR_MASK 0x3f
39 #define FAT_ENTRY_FREE 0xe5
41 struct vfat_super_block {
44 uint16_t sector_size_bytes;
45 uint8_t sectors_per_cluster;
46 uint16_t reserved_sct;
57 struct fat_super_block {
65 struct fat32_super_block {
66 uint32_t fat32_length;
69 uint32_t root_cluster;
70 uint16_t insfo_sector;
72 uint16_t reserved2[6];
83 struct vfat_dir_entry {
90 uint16_t cluster_high;
97 static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, int count)
99 for (;--count >= 0; dir++) {
101 if (dir->name[0] == 0x00) {
107 if (dir->name[0] == FAT_ENTRY_FREE)
111 if ((dir->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
114 if ((dir->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
115 /* labels do not have file data */
116 if (dir->cluster_high != 0 || dir->cluster_low != 0)
119 dbg("found ATTR_VOLUME_ID id in root dir");
123 dbg("skip dir entry");
129 int FAST_FUNC volume_id_probe_vfat(struct volume_id *id /*,uint64_t fat_partition_off*/)
131 #define fat_partition_off ((uint64_t)0)
132 struct vfat_super_block *vs;
133 struct vfat_dir_entry *dir;
134 uint16_t sector_size_bytes;
135 uint16_t dir_entries;
137 uint16_t reserved_sct;
138 uint32_t fat_size_sct;
139 uint32_t root_cluster;
140 uint32_t dir_size_sct;
141 uint32_t cluster_count;
142 uint64_t root_start_off;
143 uint32_t start_data_sct;
146 uint8_t *label = NULL;
147 uint32_t next_cluster;
150 dbg("probing at offset 0x%llx", (unsigned long long) fat_partition_off);
152 vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
156 /* believe only that's fat, don't trust the version
157 * the cluster_count will tell us
159 if (memcmp(vs->sysid, "NTFS", 4) == 0)
162 if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
165 if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
168 if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
171 if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
174 if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
178 * There are old floppies out there without a magic, so we check
179 * for well known values and guess if it's a fat volume
182 /* boot jump address check */
183 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90)
184 && vs->boot_jump[0] != 0xe9
193 /* cluster size check */
194 if (vs->sectors_per_cluster == 0
195 || (vs->sectors_per_cluster & (vs->sectors_per_cluster-1))
201 if (vs->media < 0xf8 && vs->media != 0xf0)
209 /* sector size check */
210 sector_size_bytes = le16_to_cpu(vs->sector_size_bytes);
211 if (sector_size_bytes != 0x200 && sector_size_bytes != 0x400
212 && sector_size_bytes != 0x800 && sector_size_bytes != 0x1000
217 dbg("sector_size_bytes 0x%x", sector_size_bytes);
218 dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
220 reserved_sct = le16_to_cpu(vs->reserved_sct);
221 dbg("reserved_sct 0x%x", reserved_sct);
223 sect_count = le16_to_cpu(vs->sectors);
225 sect_count = le32_to_cpu(vs->total_sect);
226 dbg("sect_count 0x%x", sect_count);
228 fat_size_sct = le16_to_cpu(vs->fat_length);
229 if (fat_size_sct == 0)
230 fat_size_sct = le32_to_cpu(vs->type.fat32.fat32_length);
231 fat_size_sct *= vs->fats;
232 dbg("fat_size_sct 0x%x", fat_size_sct);
234 dir_entries = le16_to_cpu(vs->dir_entries);
235 dir_size_sct = ((dir_entries * sizeof(struct vfat_dir_entry)) +
236 (sector_size_bytes-1)) / sector_size_bytes;
237 dbg("dir_size_sct 0x%x", dir_size_sct);
239 cluster_count = sect_count - (reserved_sct + fat_size_sct + dir_size_sct);
240 cluster_count /= vs->sectors_per_cluster;
241 dbg("cluster_count 0x%x", cluster_count);
243 // if (cluster_count < FAT12_MAX) {
244 // strcpy(id->type_version, "FAT12");
245 // } else if (cluster_count < FAT16_MAX) {
246 // strcpy(id->type_version, "FAT16");
248 // strcpy(id->type_version, "FAT32");
251 if (cluster_count >= FAT16_MAX)
254 /* the label may be an attribute in the root directory */
255 root_start_off = (reserved_sct + fat_size_sct) * sector_size_bytes;
256 dbg("root dir start 0x%llx", (unsigned long long) root_start_off);
257 dbg("expected entries 0x%x", dir_entries);
259 buf_size = dir_entries * sizeof(struct vfat_dir_entry);
260 buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size);
264 label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries);
266 vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
270 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
271 // volume_id_set_label_raw(id, label, 11);
272 volume_id_set_label_string(id, label, 11);
273 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
274 // volume_id_set_label_raw(id, vs->type.fat.label, 11);
275 volume_id_set_label_string(id, vs->type.fat.label, 11);
277 volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
281 /* FAT32 root dir is a cluster chain like any other directory */
282 buf_size = vs->sectors_per_cluster * sector_size_bytes;
283 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
284 start_data_sct = reserved_sct + fat_size_sct;
286 next_cluster = root_cluster;
289 uint64_t next_off_sct;
291 uint64_t fat_entry_off;
294 dbg("next_cluster 0x%x", (unsigned)next_cluster);
295 next_off_sct = (uint64_t)(next_cluster - 2) * vs->sectors_per_cluster;
296 next_off = (start_data_sct + next_off_sct) * sector_size_bytes;
297 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
300 buf = volume_id_get_buffer(id, fat_partition_off + next_off, buf_size);
304 dir = (struct vfat_dir_entry*) buf;
305 count = buf_size / sizeof(struct vfat_dir_entry);
306 dbg("expected entries 0x%x", count);
308 label = get_attr_volume_id(dir, count);
313 fat_entry_off = (reserved_sct * sector_size_bytes) + (next_cluster * sizeof(uint32_t));
314 dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off);
315 buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size);
319 /* set next cluster */
320 next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff;
321 if (next_cluster < 2 || next_cluster > FAT32_MAX)
325 dbg("reached maximum follow count of root cluster chain, give up");
327 vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
331 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
332 // volume_id_set_label_raw(id, label, 11);
333 volume_id_set_label_string(id, label, 11);
334 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
335 // volume_id_set_label_raw(id, vs->type.fat32.label, 11);
336 volume_id_set_label_string(id, vs->type.fat32.label, 11);
338 volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
341 // volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
342 IF_FEATURE_BLKID_TYPE(id->type = "vfat";)