2 * volume_id - reads filesystem label and uuid
4 * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the
8 * Free Software Foundation version 2 of the License.
26 #include "libvolume_id.h"
30 #define FAT12_MAX 0xff5
31 #define FAT16_MAX 0xfff5
32 #define FAT_ATTR_VOLUME_ID 0x08
33 #define FAT_ATTR_DIR 0x10
34 #define FAT_ATTR_LONG_NAME 0x0f
35 #define FAT_ATTR_MASK 0x3f
36 #define FAT_ENTRY_FREE 0xe5
38 struct vfat_super_block {
42 uint8_t sectors_per_cluster;
54 struct fat_super_block {
62 struct fat32_super_block {
63 uint32_t fat32_length;
66 uint32_t root_cluster;
67 uint16_t insfo_sector;
69 uint16_t reserved2[6];
80 struct vfat_dir_entry {
87 uint16_t cluster_high;
94 static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned int count)
98 for (i = 0; i < count; i++) {
100 if (dir[i].name[0] == 0x00) {
106 if (dir[i].name[0] == FAT_ENTRY_FREE)
110 if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
113 if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
114 /* labels do not have file data */
115 if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
118 dbg("found ATTR_VOLUME_ID id in root dir");
122 dbg("skip dir entry");
128 int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
130 struct vfat_super_block *vs;
131 struct vfat_dir_entry *dir;
132 uint16_t sector_size;
133 uint16_t dir_entries;
137 uint32_t root_cluster;
139 uint32_t cluster_count;
141 uint32_t fat32_length;
143 uint32_t start_data_sect;
144 uint16_t root_dir_entries;
147 uint8_t *label = NULL;
151 dbg("probing at offset 0x%llx", (unsigned long long) off);
153 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
157 /* believe only that's fat, don't trust the version
158 * the cluster_count will tell us
160 if (memcmp(vs->sysid, "NTFS", 4) == 0)
163 if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
166 if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
169 if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
172 if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
175 if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
178 /* some old floppies don't have a magic, so we expect the boot code to match */
180 /* boot jump address check */
181 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
182 vs->boot_jump[0] != 0xe9)
186 /* reserverd sector count */
195 if (vs->media < 0xf8 && vs->media != 0xf0)
198 /* cluster size check*/
199 if (vs->sectors_per_cluster == 0 ||
200 (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
203 /* sector size check */
204 sector_size = le16_to_cpu(vs->sector_size);
205 if (sector_size != 0x200 && sector_size != 0x400 &&
206 sector_size != 0x800 && sector_size != 0x1000)
209 dbg("sector_size 0x%x", sector_size);
210 dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
212 dir_entries = le16_to_cpu(vs->dir_entries);
213 reserved = le16_to_cpu(vs->reserved);
214 dbg("reserved 0x%x", reserved);
216 sect_count = le16_to_cpu(vs->sectors);
218 sect_count = le32_to_cpu(vs->total_sect);
219 dbg("sect_count 0x%x", sect_count);
221 fat_length = le16_to_cpu(vs->fat_length);
222 dbg("fat_length 0x%x", fat_length);
223 fat32_length = le32_to_cpu(vs->type.fat32.fat32_length);
224 dbg("fat32_length 0x%x", fat32_length);
227 fat_size = fat_length * vs->fats;
228 else if (fat32_length)
229 fat_size = fat32_length * vs->fats;
232 dbg("fat_size 0x%x", fat_size);
234 dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
235 (sector_size-1)) / sector_size;
236 dbg("dir_size 0x%x", dir_size);
238 cluster_count = sect_count - (reserved + fat_size + dir_size);
239 cluster_count /= vs->sectors_per_cluster;
240 dbg("cluster_count 0x%x", cluster_count);
243 if (!fat_length && fat32_length)
246 /* cluster_count tells us the format */
247 if (cluster_count < FAT12_MAX)
248 strcpy(id->type_version, "FAT12");
249 else if (cluster_count < FAT16_MAX)
250 strcpy(id->type_version, "FAT16");
254 /* the label may be an attribute in the root directory */
255 root_start = (reserved + fat_size) * sector_size;
256 dbg("root dir start 0x%llx", (unsigned long long) root_start);
257 root_dir_entries = le16_to_cpu(vs->dir_entries);
258 dbg("expected entries 0x%x", root_dir_entries);
260 buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
261 buf = volume_id_get_buffer(id, off + root_start, buf_size);
265 dir = (struct vfat_dir_entry*) buf;
267 label = get_attr_volume_id(dir, root_dir_entries);
269 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
273 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
274 volume_id_set_label_raw(id, label, 11);
275 volume_id_set_label_string(id, label, 11);
276 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
277 volume_id_set_label_raw(id, vs->type.fat.label, 11);
278 volume_id_set_label_string(id, vs->type.fat.label, 11);
280 volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
284 strcpy(id->type_version, "FAT32");
286 /* FAT32 root dir is a cluster chain like any other directory */
287 buf_size = vs->sectors_per_cluster * sector_size;
288 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
289 dbg("root dir cluster %u", root_cluster);
290 start_data_sect = reserved + fat_size;
295 uint32_t next_sect_off;
297 uint64_t fat_entry_off;
300 dbg("next cluster %u", next);
301 next_sect_off = (next - 2) * vs->sectors_per_cluster;
302 next_off = (start_data_sect + next_sect_off) * sector_size;
303 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
306 buf = volume_id_get_buffer(id, off + next_off, buf_size);
310 dir = (struct vfat_dir_entry*) buf;
311 count = buf_size / sizeof(struct vfat_dir_entry);
312 dbg("expected entries 0x%x", count);
314 label = get_attr_volume_id(dir, count);
319 fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
320 buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
324 /* set next cluster */
325 next = le32_to_cpu(*((uint32_t *) buf) & 0x0fffffff);
330 dbg("reached maximum follow count of root cluster chain, give up");
332 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
336 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
337 volume_id_set_label_raw(id, label, 11);
338 volume_id_set_label_string(id, label, 11);
339 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
340 volume_id_set_label_raw(id, vs->type.fat32.label, 11);
341 volume_id_set_label_string(id, vs->type.fat32.label, 11);
343 volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
346 volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);