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 #include "volume_id_internal.h"
23 /* linux/msdos_fs.h says: */
24 #define FAT12_MAX 0xff4
25 #define FAT16_MAX 0xfff4
26 #define FAT32_MAX 0x0ffffff6
28 #define FAT_ATTR_VOLUME_ID 0x08
29 #define FAT_ATTR_DIR 0x10
30 #define FAT_ATTR_LONG_NAME 0x0f
31 #define FAT_ATTR_MASK 0x3f
32 #define FAT_ENTRY_FREE 0xe5
34 struct vfat_super_block {
37 uint16_t sector_size_bytes;
38 uint8_t sectors_per_cluster;
39 uint16_t reserved_sct;
50 struct fat_super_block {
57 } __attribute__((__packed__)) fat;
58 struct fat32_super_block {
59 uint32_t fat32_length;
62 uint32_t root_cluster;
63 uint16_t insfo_sector;
65 uint16_t reserved2[6];
72 } __attribute__((__packed__)) fat32;
73 } __attribute__((__packed__)) type;
74 } __attribute__((__packed__));
76 struct vfat_dir_entry {
83 uint16_t cluster_high;
88 } __attribute__((__packed__));
90 static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, int count)
92 for (;--count >= 0; dir++) {
94 if (dir->name[0] == 0x00) {
100 if (dir->name[0] == FAT_ENTRY_FREE)
104 if ((dir->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
107 if ((dir->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
108 /* labels do not have file data */
109 if (dir->cluster_high != 0 || dir->cluster_low != 0)
112 dbg("found ATTR_VOLUME_ID id in root dir");
116 dbg("skip dir entry");
122 int volume_id_probe_vfat(struct volume_id *id, uint64_t fat_partition_off)
124 struct vfat_super_block *vs;
125 struct vfat_dir_entry *dir;
126 uint16_t sector_size_bytes;
127 uint16_t dir_entries;
129 uint16_t reserved_sct;
130 uint32_t fat_size_sct;
131 uint32_t root_cluster;
132 uint32_t dir_size_sct;
133 uint32_t cluster_count;
134 uint64_t root_start_off;
135 uint32_t start_data_sct;
138 uint8_t *label = NULL;
139 uint32_t next_cluster;
142 dbg("probing at offset 0x%llx", (unsigned long long) fat_partition_off);
144 vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
148 /* believe only that's fat, don't trust the version
149 * the cluster_count will tell us
151 if (memcmp(vs->sysid, "NTFS", 4) == 0)
154 if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
157 if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
160 if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
163 if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
166 if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
170 * There are old floppies out there without a magic, so we check
171 * for well known values and guess if it's a fat volume
174 /* boot jump address check */
175 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
176 vs->boot_jump[0] != 0xe9)
183 /* cluster size check */
184 if (vs->sectors_per_cluster == 0 ||
185 (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
189 if (vs->media < 0xf8 && vs->media != 0xf0)
197 /* sector size check */
198 sector_size_bytes = le16_to_cpu(vs->sector_size_bytes);
199 if (sector_size_bytes != 0x200 && sector_size_bytes != 0x400 &&
200 sector_size_bytes != 0x800 && sector_size_bytes != 0x1000)
203 dbg("sector_size_bytes 0x%x", sector_size_bytes);
204 dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
206 reserved_sct = le16_to_cpu(vs->reserved_sct);
207 dbg("reserved_sct 0x%x", reserved_sct);
209 sect_count = le16_to_cpu(vs->sectors);
211 sect_count = le32_to_cpu(vs->total_sect);
212 dbg("sect_count 0x%x", sect_count);
214 fat_size_sct = le16_to_cpu(vs->fat_length);
215 if (fat_size_sct == 0)
216 fat_size_sct = le32_to_cpu(vs->type.fat32.fat32_length);
217 fat_size_sct *= vs->fats;
218 dbg("fat_size_sct 0x%x", fat_size_sct);
220 dir_entries = le16_to_cpu(vs->dir_entries);
221 dir_size_sct = ((dir_entries * sizeof(struct vfat_dir_entry)) +
222 (sector_size_bytes-1)) / sector_size_bytes;
223 dbg("dir_size_sct 0x%x", dir_size_sct);
225 cluster_count = sect_count - (reserved_sct + fat_size_sct + dir_size_sct);
226 cluster_count /= vs->sectors_per_cluster;
227 dbg("cluster_count 0x%x", cluster_count);
229 // if (cluster_count < FAT12_MAX) {
230 // strcpy(id->type_version, "FAT12");
231 // } else if (cluster_count < FAT16_MAX) {
232 // strcpy(id->type_version, "FAT16");
234 // strcpy(id->type_version, "FAT32");
237 if (cluster_count >= FAT16_MAX)
240 /* the label may be an attribute in the root directory */
241 root_start_off = (reserved_sct + fat_size_sct) * sector_size_bytes;
242 dbg("root dir start 0x%llx", (unsigned long long) root_start_off);
243 dbg("expected entries 0x%x", dir_entries);
245 buf_size = dir_entries * sizeof(struct vfat_dir_entry);
246 buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size);
250 label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries);
252 vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
256 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
257 // volume_id_set_label_raw(id, label, 11);
258 volume_id_set_label_string(id, label, 11);
259 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
260 // volume_id_set_label_raw(id, vs->type.fat.label, 11);
261 volume_id_set_label_string(id, vs->type.fat.label, 11);
263 volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
267 /* FAT32 root dir is a cluster chain like any other directory */
268 buf_size = vs->sectors_per_cluster * sector_size_bytes;
269 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
270 start_data_sct = reserved_sct + fat_size_sct;
272 next_cluster = root_cluster;
275 uint64_t next_off_sct;
277 uint64_t fat_entry_off;
280 dbg("next_cluster 0x%x", (unsigned)next_cluster);
281 next_off_sct = (uint64_t)(next_cluster - 2) * vs->sectors_per_cluster;
282 next_off = (start_data_sct + next_off_sct) * sector_size_bytes;
283 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
286 buf = volume_id_get_buffer(id, fat_partition_off + next_off, buf_size);
290 dir = (struct vfat_dir_entry*) buf;
291 count = buf_size / sizeof(struct vfat_dir_entry);
292 dbg("expected entries 0x%x", count);
294 label = get_attr_volume_id(dir, count);
299 fat_entry_off = (reserved_sct * sector_size_bytes) + (next_cluster * sizeof(uint32_t));
300 dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off);
301 buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size);
305 /* set next cluster */
306 next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff;
307 if (next_cluster < 2 || next_cluster > FAT32_MAX)
311 dbg("reached maximum follow count of root cluster chain, give up");
313 vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
317 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
318 // volume_id_set_label_raw(id, label, 11);
319 volume_id_set_label_string(id, label, 11);
320 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
321 // volume_id_set_label_raw(id, vs->type.fat32.label, 11);
322 volume_id_set_label_string(id, vs->type.fat32.label, 11);
324 volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
327 // volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
328 // id->type = "vfat";