2 * volume_id - reads filesystem label and uuid
4 * Copyright (C) 2004-2007 Kay Sievers <kay.sievers@vrfy.org>
5 * Copyright (C) 2007 Ryan Lortie <desrt@desrt.ca>
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License as published by the
9 * Free Software Foundation version 2 of the License.
27 #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 #define VFAT_LFN_SEQ_MASK 0x3f
39 #define VFAT_LFN_SEQ_LAST 0x40
40 #define VFAT_LFN_SEQ_MAX 20
41 #define VFAT_LFN_CHARS_PER_ENTRY (5 + 6 + 2)
42 #define VFAT_LOWERCASE_NAME 0x10
43 #define VFAT_LOWERCASE_EXT 0x08
45 struct vfat_super_block {
49 uint8_t sectors_per_cluster;
61 struct fat_super_block {
69 struct fat32_super_block {
70 uint32_t fat32_length;
73 uint32_t root_cluster;
74 uint16_t fsinfo_sector;
76 uint16_t reserved2[6];
88 uint8_t signature1[4];
89 uint32_t reserved1[120];
90 uint8_t signature2[4];
91 uint32_t free_clusters;
92 uint32_t next_cluster;
93 uint32_t reserved2[4];
96 struct vfat_dir_entry {
100 uint8_t fine_time_creat;
104 uint16_t cluster_high;
107 uint16_t cluster_low;
112 struct vfat_lfn_entry {
123 static uint8_t fat_lfn_checksum(const uint8_t name[11])
128 /* http://en.wikipedia.org/wiki/File_Allocation_Table */
129 for (i = 0; i < 11; i++)
130 cksum = ((cksum & 1) ? 0x80 : 0) + (cksum >> 1) + name[i];
135 static size_t fat_read_lfn(uint8_t *filename, size_t fnsize,
136 struct vfat_dir_entry *dir,
137 struct vfat_dir_entry *entry)
139 uint8_t buffer[VFAT_LFN_SEQ_MAX * VFAT_LFN_CHARS_PER_ENTRY * 2];
140 uint8_t expected_seq = 1;
145 cksum = fat_lfn_checksum(entry->name);
147 while (--entry >= dir) {
148 struct vfat_lfn_entry *lfn = (struct vfat_lfn_entry *) entry;
150 if (expected_seq > VFAT_LFN_SEQ_MAX)
153 if ((lfn->attr & FAT_ATTR_MASK) != FAT_ATTR_LONG_NAME)
156 if (lfn->cksum != cksum)
159 if ((lfn->seq & VFAT_LFN_SEQ_MASK) != expected_seq++)
162 if (lfn->cluster != 0)
165 /* extra paranoia -- should never happen */
166 if (len + sizeof(lfn->name0) + sizeof(lfn->name1) +
167 sizeof(lfn->name2) > sizeof(buffer))
170 memcpy (&buffer[len], lfn->name0, sizeof(lfn->name0));
171 len += sizeof(lfn->name0);
172 memcpy (&buffer[len], lfn->name1, sizeof(lfn->name1));
173 len += sizeof(lfn->name1);
174 memcpy (&buffer[len], lfn->name2, sizeof(lfn->name2));
175 len += sizeof(lfn->name2);
177 if (lfn->seq & VFAT_LFN_SEQ_LAST) {
178 fnlen = volume_id_set_unicode16(filename, fnsize, buffer, LE, len);
186 static size_t fat_read_filename(uint8_t *filename, size_t fnsize,
187 struct vfat_dir_entry *dir, struct vfat_dir_entry *entry)
192 /* check if maybe we have LFN entries */
193 len = fat_read_lfn(filename, fnsize, dir, entry);
197 /* else, read the normal 8.3 name */
198 for (i = 0; i < 11; i++) {
199 if (entry->lowercase & ((i < 8) ? VFAT_LOWERCASE_NAME : VFAT_LOWERCASE_EXT))
200 filename[i] = tolower(entry->name[i]);
202 filename[i] = entry->name[i];
207 filename[len] = '\0';
211 /* fills filename, returns string length */
212 static size_t get_fat_attr_volume_id(uint8_t *filename, size_t fnsize,
213 struct vfat_dir_entry *dir, unsigned int count)
217 for (i = 0; i < count; i++) {
219 if (dir[i].name[0] == 0x00) {
225 if (dir[i].name[0] == FAT_ENTRY_FREE)
229 if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
232 if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
233 /* labels do not have file data */
234 if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
237 dbg("found ATTR_VOLUME_ID id in root dir");
238 return fat_read_filename(filename, fnsize, dir, &dir[i]);
241 dbg("skip dir entry");
247 int volume_id_probe_vfat(struct volume_id *id, uint64_t off, uint64_t size)
249 uint8_t filename[255 * 3];
250 struct vfat_super_block *vs;
251 struct vfat_dir_entry *dir;
252 struct fat32_fsinfo *fsinfo;
253 uint16_t sector_size;
254 uint16_t dir_entries;
258 uint32_t root_cluster;
260 uint32_t cluster_count;
262 uint32_t fat32_length;
264 uint32_t start_data_sect;
265 uint16_t root_dir_entries;
266 uint16_t fsinfo_sect;
273 info("probing at offset 0x%llx", (unsigned long long) off);
275 buf = volume_id_get_buffer(id, off, 0x400);
279 /* check signature */
280 if (buf[510] != 0x55 || buf[511] != 0xaa)
283 vs = (struct vfat_super_block *) buf;
284 if (memcmp(vs->sysid, "NTFS", 4) == 0)
287 /* believe only that's fat, don't trust the version */
288 if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
291 if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
294 if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
297 if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
300 if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
303 /* some old floppies don't have a magic, expect the boot jump address to match */
304 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
305 vs->boot_jump[0] != 0xe9)
309 /* reserverd sector count */
318 if (vs->media < 0xf8 && vs->media != 0xf0)
321 /* cluster size check */
322 if (vs->sectors_per_cluster == 0 ||
323 (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
326 /* sector size check */
327 sector_size = le16_to_cpu(vs->sector_size);
328 if (sector_size == 0 || ((sector_size & (sector_size-1)) != 0))
331 dbg("sector_size 0x%x", sector_size);
332 dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
334 dir_entries = le16_to_cpu(vs->dir_entries);
335 reserved = le16_to_cpu(vs->reserved);
336 dbg("reserved 0x%x", reserved);
338 sect_count = le16_to_cpu(vs->sectors);
340 sect_count = le32_to_cpu(vs->total_sect);
341 dbg("sect_count 0x%x", sect_count);
343 fat_length = le16_to_cpu(vs->fat_length);
344 dbg("fat_length 0x%x", fat_length);
345 fat32_length = le32_to_cpu(vs->type.fat32.fat32_length);
346 dbg("fat32_length 0x%x", fat32_length);
349 fat_size = fat_length * vs->fats;
350 else if (fat32_length)
351 fat_size = fat32_length * vs->fats;
354 dbg("fat_size 0x%x", fat_size);
356 dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
357 (sector_size-1)) / sector_size;
358 dbg("dir_size 0x%x", dir_size);
360 cluster_count = sect_count - (reserved + fat_size + dir_size);
361 cluster_count /= vs->sectors_per_cluster;
362 dbg("cluster_count 0x%x", cluster_count);
365 if (!fat_length && fat32_length)
368 /* cluster_count tells us the format */
369 if (cluster_count < FAT12_MAX)
370 strcpy(id->type_version, "FAT12");
371 else if (cluster_count < FAT16_MAX)
372 strcpy(id->type_version, "FAT16");
376 /* the label may be an attribute in the root directory */
377 root_start = (reserved + fat_size) * sector_size;
378 dbg("root dir start 0x%llx", (unsigned long long) root_start);
379 root_dir_entries = le16_to_cpu(vs->dir_entries);
380 dbg("expected entries 0x%x", root_dir_entries);
382 buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
383 buf = volume_id_get_buffer(id, off + root_start, buf_size);
387 dir = (struct vfat_dir_entry*) buf;
389 fnlen = get_fat_attr_volume_id(filename, sizeof(filename), dir, root_dir_entries);
391 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
395 if (fnlen > 0 && memcmp(filename, "NO NAME ", 11) != 0) {
396 volume_id_set_label_raw(id, filename, fnlen);
397 volume_id_set_label_string(id, filename, fnlen);
398 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
399 volume_id_set_label_raw(id, vs->type.fat.label, 11);
400 volume_id_set_label_string(id, vs->type.fat.label, 11);
402 volume_id_set_uuid(id, vs->type.fat.serno, 0, UUID_DOS);
406 /* FAT32 should have a valid signature in the fsinfo block */
407 fsinfo_sect = le16_to_cpu(vs->type.fat32.fsinfo_sector);
408 buf = volume_id_get_buffer(id, off + (fsinfo_sect * sector_size), 0x200);
411 fsinfo = (struct fat32_fsinfo *) buf;
412 if (memcmp(fsinfo->signature1, "\x52\x52\x61\x41", 4) != 0)
414 if (memcmp(fsinfo->signature2, "\x72\x72\x41\x61", 4) != 0)
417 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
421 strcpy(id->type_version, "FAT32");
423 /* FAT32 root dir is a cluster chain like any other directory */
424 buf_size = vs->sectors_per_cluster * sector_size;
425 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
426 dbg("root dir cluster %u", root_cluster);
427 start_data_sect = reserved + fat_size;
432 uint32_t next_sect_off;
434 uint64_t fat_entry_off;
437 dbg("next cluster %u", next);
438 next_sect_off = (next - 2) * vs->sectors_per_cluster;
439 next_off = (start_data_sect + next_sect_off) * sector_size;
440 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
443 buf = volume_id_get_buffer(id, off + next_off, buf_size);
447 dir = (struct vfat_dir_entry*) buf;
448 count = buf_size / sizeof(struct vfat_dir_entry);
449 dbg("expected entries 0x%x", count);
451 fnlen = get_fat_attr_volume_id(filename, sizeof(filename), dir, count);
456 fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
457 buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
461 /* set next cluster */
462 next = le32_to_cpu(*((uint32_t *) buf)) & 0x0fffffff;
463 if (next < 2 || next >= 0x0ffffff0)
467 dbg("reached maximum follow count of root cluster chain, give up");
469 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
473 if (fnlen > 0 && memcmp(filename, "NO NAME ", 11) != 0) {
474 volume_id_set_label_raw(id, filename, fnlen);
475 volume_id_set_label_string(id, filename, fnlen);
476 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
477 volume_id_set_label_raw(id, vs->type.fat32.label, 11);
478 volume_id_set_label_string(id, vs->type.fat32.label, 11);
480 volume_id_set_uuid(id, vs->type.fat32.serno, 0, UUID_DOS);
483 volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);