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 "volume_id.h"
31 #define FAT12_MAX 0xff5
32 #define FAT16_MAX 0xfff5
33 #define FAT_ATTR_VOLUME_ID 0x08
34 #define FAT_ATTR_DIR 0x10
35 #define FAT_ATTR_LONG_NAME 0x0f
36 #define FAT_ATTR_MASK 0x3f
37 #define FAT_ENTRY_FREE 0xe5
39 struct vfat_super_block {
43 uint8_t sectors_per_cluster;
55 struct fat_super_block {
62 } __attribute__((__packed__)) fat;
63 struct fat32_super_block {
64 uint32_t fat32_length;
67 uint32_t root_cluster;
68 uint16_t insfo_sector;
70 uint16_t reserved2[6];
77 } __attribute__((__packed__)) fat32;
78 } __attribute__((__packed__)) type;
79 } __attribute__((__packed__));
81 struct vfat_dir_entry {
88 uint16_t cluster_high;
93 } __attribute__((__packed__));
95 static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned int count)
99 for (i = 0; i < count; i++) {
101 if (dir[i].name[0] == 0x00) {
107 if (dir[i].name[0] == FAT_ENTRY_FREE)
111 if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
114 if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
115 /* labels do not have file data */
116 if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
119 dbg("found ATTR_VOLUME_ID id in root dir");
123 dbg("skip dir entry");
129 int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
131 struct vfat_super_block *vs;
132 struct vfat_dir_entry *dir;
133 uint16_t sector_size;
134 uint16_t dir_entries;
138 uint32_t root_cluster;
140 uint32_t cluster_count;
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)
179 * There are old floppies out there without a magic, so we check
180 * for well known values and guess if it's a fat volume
183 /* boot jump address check */
184 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
185 vs->boot_jump[0] != 0xe9)
192 /* cluster size check*/
193 if (vs->sectors_per_cluster == 0 ||
194 (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
198 if (vs->media < 0xf8 && vs->media != 0xf0)
206 /* sector size check */
207 sector_size = le16_to_cpu(vs->sector_size);
208 if (sector_size != 0x200 && sector_size != 0x400 &&
209 sector_size != 0x800 && sector_size != 0x1000)
212 dbg("sector_size 0x%x", sector_size);
213 dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
215 dir_entries = le16_to_cpu(vs->dir_entries);
216 reserved = le16_to_cpu(vs->reserved);
217 dbg("reserved 0x%x", reserved);
219 sect_count = le16_to_cpu(vs->sectors);
221 sect_count = le32_to_cpu(vs->total_sect);
222 dbg("sect_count 0x%x", sect_count);
224 fat_length = le16_to_cpu(vs->fat_length);
226 fat_length = le32_to_cpu(vs->type.fat32.fat32_length);
227 dbg("fat_length 0x%x", fat_length);
229 fat_size = fat_length * vs->fats;
230 dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
231 (sector_size-1)) / sector_size;
232 dbg("dir_size 0x%x", dir_size);
234 cluster_count = sect_count - (reserved + fat_size + dir_size);
235 cluster_count /= vs->sectors_per_cluster;
236 dbg("cluster_count 0x%x", cluster_count);
238 if (cluster_count < FAT12_MAX) {
239 strcpy(id->type_version, "FAT12");
240 } else if (cluster_count < FAT16_MAX) {
241 strcpy(id->type_version, "FAT16");
243 strcpy(id->type_version, "FAT32");
247 /* the label may be an attribute in the root directory */
248 root_start = (reserved + fat_size) * sector_size;
249 dbg("root dir start 0x%llx", (unsigned long long) root_start);
250 root_dir_entries = le16_to_cpu(vs->dir_entries);
251 dbg("expected entries 0x%x", root_dir_entries);
253 buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
254 buf = volume_id_get_buffer(id, off + root_start, buf_size);
258 dir = (struct vfat_dir_entry*) buf;
260 label = get_attr_volume_id(dir, root_dir_entries);
262 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
266 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
267 volume_id_set_label_raw(id, label, 11);
268 volume_id_set_label_string(id, label, 11);
269 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
270 volume_id_set_label_raw(id, vs->type.fat.label, 11);
271 volume_id_set_label_string(id, vs->type.fat.label, 11);
273 volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
277 /* FAT32 root dir is a cluster chain like any other directory */
278 buf_size = vs->sectors_per_cluster * sector_size;
279 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
280 dbg("root dir cluster %u", root_cluster);
281 start_data_sect = reserved + fat_size;
286 uint32_t next_sect_off;
288 uint64_t fat_entry_off;
291 dbg("next cluster %u", next);
292 next_sect_off = (next - 2) * vs->sectors_per_cluster;
293 next_off = (start_data_sect + next_sect_off) * sector_size;
294 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
297 buf = volume_id_get_buffer(id, off + next_off, buf_size);
301 dir = (struct vfat_dir_entry*) buf;
302 count = buf_size / sizeof(struct vfat_dir_entry);
303 dbg("expected entries 0x%x", count);
305 label = get_attr_volume_id(dir, count);
310 fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
311 buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
315 /* set next cluster */
316 next = le32_to_cpu(*((uint32_t *) buf) & 0x0fffffff);
321 dbg("reached maximum follow count of root cluster chain, give up");
323 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
327 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
328 volume_id_set_label_raw(id, label, 11);
329 volume_id_set_label_string(id, label, 11);
330 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
331 volume_id_set_label_raw(id, vs->type.fat32.label, 11);
332 volume_id_set_label_string(id, vs->type.fat32.label, 11);
334 volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
337 volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);