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 #define FAT12_MAX 0xff5
24 #define FAT16_MAX 0xfff5
25 #define FAT_ATTR_VOLUME_ID 0x08
26 #define FAT_ATTR_DIR 0x10
27 #define FAT_ATTR_LONG_NAME 0x0f
28 #define FAT_ATTR_MASK 0x3f
29 #define FAT_ENTRY_FREE 0xe5
31 struct vfat_super_block {
35 uint8_t sectors_per_cluster;
47 struct fat_super_block {
54 } __attribute__((__packed__)) fat;
55 struct fat32_super_block {
56 uint32_t fat32_length;
59 uint32_t root_cluster;
60 uint16_t insfo_sector;
62 uint16_t reserved2[6];
69 } __attribute__((__packed__)) fat32;
70 } __attribute__((__packed__)) type;
71 } __attribute__((__packed__));
73 struct vfat_dir_entry {
80 uint16_t cluster_high;
85 } __attribute__((__packed__));
87 static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned count)
91 for (i = 0; i < count; i++) {
93 if (dir[i].name[0] == 0x00) {
99 if (dir[i].name[0] == FAT_ENTRY_FREE)
103 if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
106 if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
107 /* labels do not have file data */
108 if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
111 dbg("found ATTR_VOLUME_ID id in root dir");
115 dbg("skip dir entry");
121 int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
123 struct vfat_super_block *vs;
124 struct vfat_dir_entry *dir;
125 uint16_t sector_size;
126 uint16_t dir_entries;
130 uint32_t root_cluster;
132 uint32_t cluster_count;
135 uint32_t start_data_sect;
136 uint16_t root_dir_entries;
139 uint8_t *label = NULL;
143 dbg("probing at offset 0x%llx", (unsigned long long) off);
145 vs = volume_id_get_buffer(id, off, 0x200);
149 /* believe only that's fat, don't trust the version
150 * the cluster_count will tell us
152 if (memcmp(vs->sysid, "NTFS", 4) == 0)
155 if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
158 if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
161 if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
164 if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
167 if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
171 * There are old floppies out there without a magic, so we check
172 * for well known values and guess if it's a fat volume
175 /* boot jump address check */
176 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
177 vs->boot_jump[0] != 0xe9)
184 /* cluster size check */
185 if (vs->sectors_per_cluster == 0 ||
186 (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
190 if (vs->media < 0xf8 && vs->media != 0xf0)
198 /* sector size check */
199 sector_size = le16_to_cpu(vs->sector_size);
200 if (sector_size != 0x200 && sector_size != 0x400 &&
201 sector_size != 0x800 && sector_size != 0x1000)
204 dbg("sector_size 0x%x", sector_size);
205 dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
207 dir_entries = le16_to_cpu(vs->dir_entries);
208 reserved = le16_to_cpu(vs->reserved);
209 dbg("reserved 0x%x", reserved);
211 sect_count = le16_to_cpu(vs->sectors);
213 sect_count = le32_to_cpu(vs->total_sect);
214 dbg("sect_count 0x%x", sect_count);
216 fat_length = le16_to_cpu(vs->fat_length);
218 fat_length = le32_to_cpu(vs->type.fat32.fat32_length);
219 dbg("fat_length 0x%x", fat_length);
221 fat_size = fat_length * vs->fats;
222 dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
223 (sector_size-1)) / sector_size;
224 dbg("dir_size 0x%x", dir_size);
226 cluster_count = sect_count - (reserved + fat_size + dir_size);
227 cluster_count /= vs->sectors_per_cluster;
228 dbg("cluster_count 0x%x", cluster_count);
230 // if (cluster_count < FAT12_MAX) {
231 // strcpy(id->type_version, "FAT12");
232 // } else if (cluster_count < FAT16_MAX) {
233 // strcpy(id->type_version, "FAT16");
235 // strcpy(id->type_version, "FAT32");
238 if (cluster_count >= FAT16_MAX)
241 /* the label may be an attribute in the root directory */
242 root_start = (reserved + fat_size) * sector_size;
243 dbg("root dir start 0x%llx", (unsigned long long) root_start);
244 root_dir_entries = le16_to_cpu(vs->dir_entries);
245 dbg("expected entries 0x%x", root_dir_entries);
247 buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
248 buf = volume_id_get_buffer(id, off + root_start, buf_size);
252 dir = (struct vfat_dir_entry*) buf;
254 label = get_attr_volume_id(dir, root_dir_entries);
256 vs = volume_id_get_buffer(id, off, 0x200);
260 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
261 // volume_id_set_label_raw(id, label, 11);
262 volume_id_set_label_string(id, label, 11);
263 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
264 // volume_id_set_label_raw(id, vs->type.fat.label, 11);
265 volume_id_set_label_string(id, vs->type.fat.label, 11);
267 volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
271 /* FAT32 root dir is a cluster chain like any other directory */
272 buf_size = vs->sectors_per_cluster * sector_size;
273 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
274 dbg("root dir cluster %u", root_cluster);
275 start_data_sect = reserved + fat_size;
280 uint32_t next_sect_off;
282 uint64_t fat_entry_off;
285 dbg("next cluster %u", next);
286 next_sect_off = (next - 2) * vs->sectors_per_cluster;
287 next_off = (start_data_sect + next_sect_off) * sector_size;
288 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
291 buf = volume_id_get_buffer(id, off + next_off, buf_size);
295 dir = (struct vfat_dir_entry*) buf;
296 count = buf_size / sizeof(struct vfat_dir_entry);
297 dbg("expected entries 0x%x", count);
299 label = get_attr_volume_id(dir, count);
304 fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
305 buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
309 /* set next cluster */
310 next = le32_to_cpu(*((uint32_t *) buf) & 0x0fffffff);
315 dbg("reached maximum follow count of root cluster chain, give up");
317 vs = volume_id_get_buffer(id, off, 0x200);
321 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
322 // volume_id_set_label_raw(id, label, 11);
323 volume_id_set_label_string(id, label, 11);
324 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
325 // volume_id_set_label_raw(id, vs->type.fat32.label, 11);
326 volume_id_set_label_string(id, vs->type.fat32.label, 11);
328 volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
331 // volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
332 // id->type = "vfat";