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
36 #include "volume_id.h"
41 #define FAT12_MAX 0xff5
42 #define FAT16_MAX 0xfff5
43 #define FAT_ATTR_VOLUME_ID 0x08
44 #define FAT_ATTR_DIR 0x10
45 #define FAT_ATTR_LONG_NAME 0x0f
46 #define FAT_ATTR_MASK 0x3f
47 #define FAT_ENTRY_FREE 0xe5
49 struct vfat_super_block {
53 uint8_t sectors_per_cluster;
65 struct fat_super_block {
72 } __attribute__((__packed__)) fat;
73 struct fat32_super_block {
74 uint32_t fat32_length;
77 uint32_t root_cluster;
78 uint16_t insfo_sector;
80 uint16_t reserved2[6];
87 } __attribute__((__packed__)) fat32;
88 } __attribute__((__packed__)) type;
89 } __attribute__((__packed__));
91 struct vfat_dir_entry {
98 uint16_t cluster_high;
101 uint16_t cluster_low;
103 } __attribute__((__packed__));
105 static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned int count)
109 for (i = 0; i < count; i++) {
111 if (dir[i].name[0] == 0x00) {
117 if (dir[i].name[0] == FAT_ENTRY_FREE)
121 if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
124 if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
125 /* labels do not have file data */
126 if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
129 dbg("found ATTR_VOLUME_ID id in root dir");
133 dbg("skip dir entry");
139 int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
141 struct vfat_super_block *vs;
142 struct vfat_dir_entry *dir;
143 uint16_t sector_size;
144 uint16_t dir_entries;
148 uint32_t root_cluster;
150 uint32_t cluster_count;
153 uint32_t start_data_sect;
154 uint16_t root_dir_entries;
157 uint8_t *label = NULL;
161 dbg("probing at offset 0x%llx", (unsigned long long) off);
163 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
167 /* believe only that's fat, don't trust the version
168 * the cluster_count will tell us
170 if (memcmp(vs->sysid, "NTFS", 4) == 0)
173 if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
176 if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
179 if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
182 if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
185 if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
189 * There are old floppies out there without a magic, so we check
190 * for well known values and guess if it's a fat volume
193 /* boot jump address check */
194 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
195 vs->boot_jump[0] != 0xe9)
202 /* cluster size check*/
203 if (vs->sectors_per_cluster == 0 ||
204 (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
208 if (vs->media < 0xf8 && vs->media != 0xf0)
216 /* sector size check */
217 sector_size = le16_to_cpu(vs->sector_size);
218 if (sector_size != 0x200 && sector_size != 0x400 &&
219 sector_size != 0x800 && sector_size != 0x1000)
222 dbg("sector_size 0x%x", sector_size);
223 dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
225 dir_entries = le16_to_cpu(vs->dir_entries);
226 reserved = le16_to_cpu(vs->reserved);
227 dbg("reserved 0x%x", reserved);
229 sect_count = le16_to_cpu(vs->sectors);
231 sect_count = le32_to_cpu(vs->total_sect);
232 dbg("sect_count 0x%x", sect_count);
234 fat_length = le16_to_cpu(vs->fat_length);
236 fat_length = le32_to_cpu(vs->type.fat32.fat32_length);
237 dbg("fat_length 0x%x", fat_length);
239 fat_size = fat_length * vs->fats;
240 dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
241 (sector_size-1)) / sector_size;
242 dbg("dir_size 0x%x", dir_size);
244 cluster_count = sect_count - (reserved + fat_size + dir_size);
245 cluster_count /= vs->sectors_per_cluster;
246 dbg("cluster_count 0x%x", cluster_count);
248 if (cluster_count < FAT12_MAX) {
249 strcpy(id->type_version, "FAT12");
250 } else if (cluster_count < FAT16_MAX) {
251 strcpy(id->type_version, "FAT16");
253 strcpy(id->type_version, "FAT32");
257 /* the label may be an attribute in the root directory */
258 root_start = (reserved + fat_size) * sector_size;
259 dbg("root dir start 0x%llx", (unsigned long long) root_start);
260 root_dir_entries = le16_to_cpu(vs->dir_entries);
261 dbg("expected entries 0x%x", root_dir_entries);
263 buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
264 buf = volume_id_get_buffer(id, off + root_start, buf_size);
268 dir = (struct vfat_dir_entry*) buf;
270 label = get_attr_volume_id(dir, root_dir_entries);
272 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
276 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
277 volume_id_set_label_raw(id, label, 11);
278 volume_id_set_label_string(id, label, 11);
279 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
280 volume_id_set_label_raw(id, vs->type.fat.label, 11);
281 volume_id_set_label_string(id, vs->type.fat.label, 11);
283 volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
287 /* FAT32 root dir is a cluster chain like any other directory */
288 buf_size = vs->sectors_per_cluster * sector_size;
289 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
290 dbg("root dir cluster %u", root_cluster);
291 start_data_sect = reserved + fat_size;
296 uint32_t next_sect_off;
298 uint64_t fat_entry_off;
301 dbg("next cluster %u", next);
302 next_sect_off = (next - 2) * vs->sectors_per_cluster;
303 next_off = (start_data_sect + next_sect_off) * sector_size;
304 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
307 buf = volume_id_get_buffer(id, off + next_off, buf_size);
311 dir = (struct vfat_dir_entry*) buf;
312 count = buf_size / sizeof(struct vfat_dir_entry);
313 dbg("expected entries 0x%x", count);
315 label = get_attr_volume_id(dir, count);
320 fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
321 buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
325 /* set next cluster */
326 next = le32_to_cpu(*((uint32_t *) buf) & 0x0fffffff);
331 dbg("reached maximum follow count of root cluster chain, give up");
333 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
337 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
338 volume_id_set_label_raw(id, label, 11);
339 volume_id_set_label_string(id, label, 11);
340 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
341 volume_id_set_label_raw(id, vs->type.fat32.label, 11);
342 volume_id_set_label_string(id, vs->type.fat32.label, 11);
344 volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
347 volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);