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
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 2 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program. If not, see <http://www.gnu.org/licenses/>.
32 #include "libvolume_id.h"
33 #include "libvolume_id-private.h"
35 #define FAT12_MAX 0xff5
36 #define FAT16_MAX 0xfff5
37 #define FAT_ATTR_VOLUME_ID 0x08
38 #define FAT_ATTR_DIR 0x10
39 #define FAT_ATTR_LONG_NAME 0x0f
40 #define FAT_ATTR_MASK 0x3f
41 #define FAT_ENTRY_FREE 0xe5
43 #define VFAT_LFN_SEQ_MASK 0x3f
44 #define VFAT_LFN_SEQ_LAST 0x40
45 #define VFAT_LFN_SEQ_MAX 20
46 #define VFAT_LFN_CHARS_PER_ENTRY (5 + 6 + 2)
47 #define VFAT_LOWERCASE_NAME 0x10
48 #define VFAT_LOWERCASE_EXT 0x08
50 struct vfat_super_block {
54 uint8_t sectors_per_cluster;
66 struct fat_super_block {
74 struct fat32_super_block {
75 uint32_t fat32_length;
78 uint32_t root_cluster;
79 uint16_t fsinfo_sector;
81 uint16_t reserved2[6];
93 uint8_t signature1[4];
94 uint32_t reserved1[120];
95 uint8_t signature2[4];
96 uint32_t free_clusters;
97 uint32_t next_cluster;
98 uint32_t reserved2[4];
101 struct vfat_dir_entry {
105 uint8_t fine_time_creat;
109 uint16_t cluster_high;
112 uint16_t cluster_low;
117 struct vfat_lfn_entry {
128 static uint8_t fat_lfn_checksum(const uint8_t name[11])
133 /* http://en.wikipedia.org/wiki/File_Allocation_Table */
134 for (i = 0; i < 11; i++)
135 cksum = ((cksum & 1) ? 0x80 : 0) + (cksum >> 1) + name[i];
140 static size_t fat_read_lfn(uint8_t *filename, size_t fnsize,
141 struct vfat_dir_entry *dir,
142 struct vfat_dir_entry *entry)
144 uint8_t buffer[VFAT_LFN_SEQ_MAX * VFAT_LFN_CHARS_PER_ENTRY * 2];
145 uint8_t expected_seq = 1;
150 cksum = fat_lfn_checksum(entry->name);
152 while (--entry >= dir) {
153 struct vfat_lfn_entry *lfn = (struct vfat_lfn_entry *) entry;
155 if (expected_seq > VFAT_LFN_SEQ_MAX)
158 if ((lfn->attr & FAT_ATTR_MASK) != FAT_ATTR_LONG_NAME)
161 if (lfn->cksum != cksum)
164 if ((lfn->seq & VFAT_LFN_SEQ_MASK) != expected_seq++)
167 if (lfn->cluster != 0)
170 /* extra paranoia -- should never happen */
171 if (len + sizeof(lfn->name0) + sizeof(lfn->name1) +
172 sizeof(lfn->name2) > sizeof(buffer))
175 memcpy (&buffer[len], lfn->name0, sizeof(lfn->name0));
176 len += sizeof(lfn->name0);
177 memcpy (&buffer[len], lfn->name1, sizeof(lfn->name1));
178 len += sizeof(lfn->name1);
179 memcpy (&buffer[len], lfn->name2, sizeof(lfn->name2));
180 len += sizeof(lfn->name2);
182 if (lfn->seq & VFAT_LFN_SEQ_LAST) {
183 fnlen = volume_id_set_unicode16(filename, fnsize, buffer, LE, len);
191 static size_t fat_read_filename(uint8_t *filename, size_t fnsize,
192 struct vfat_dir_entry *dir, struct vfat_dir_entry *entry)
197 /* check if maybe we have LFN entries */
198 len = fat_read_lfn(filename, fnsize, dir, entry);
202 /* else, read the normal 8.3 name */
203 for (i = 0; i < 11; i++) {
204 if (entry->lowercase & ((i < 8) ? VFAT_LOWERCASE_NAME : VFAT_LOWERCASE_EXT))
205 filename[i] = tolower(entry->name[i]);
207 filename[i] = entry->name[i];
212 filename[len] = '\0';
216 /* fills filename, returns string length */
217 static size_t get_fat_attr_volume_id(uint8_t *filename, size_t fnsize,
218 struct vfat_dir_entry *dir, unsigned int count)
222 for (i = 0; i < count; i++) {
224 if (dir[i].name[0] == 0x00) {
230 if (dir[i].name[0] == FAT_ENTRY_FREE)
234 if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
237 if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
238 /* labels do not have file data */
239 if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
242 dbg("found ATTR_VOLUME_ID id in root dir\n");
243 return fat_read_filename(filename, fnsize, dir, &dir[i]);
246 dbg("skip dir entry\n");
252 int volume_id_probe_vfat(struct volume_id *id, uint64_t off, uint64_t size)
254 uint8_t filename[255 * 3];
255 struct vfat_super_block *vs;
256 struct vfat_dir_entry *dir;
257 struct fat32_fsinfo *fsinfo;
258 uint16_t sector_size;
259 uint16_t dir_entries;
263 uint32_t root_cluster;
265 uint32_t cluster_count;
267 uint32_t fat32_length;
269 uint32_t start_data_sect;
270 uint16_t root_dir_entries;
271 uint16_t fsinfo_sect;
278 info("probing at offset 0x%" PRIx64 "\n", off);
280 buf = volume_id_get_buffer(id, off, 0x400);
284 vs = (struct vfat_super_block *) buf;
285 if (memcmp(vs->sysid, "NTFS", 4) == 0)
288 /* believe only that's fat, don't trust the version */
289 if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
292 if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
295 if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
298 if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
301 if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
304 /* check signature */
305 if (buf[510] != 0x55 || buf[511] != 0xaa)
308 /* some old floppies don't have a magic, expect the boot jump address to match */
309 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
310 vs->boot_jump[0] != 0xe9)
314 info("magic found\n");
315 /* reserverd sector count */
324 if (vs->media < 0xf8 && vs->media != 0xf0)
327 /* cluster size check */
328 if (vs->sectors_per_cluster == 0 ||
329 (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
332 /* sector size check */
333 sector_size = le16_to_cpu(vs->sector_size);
334 if (sector_size == 0 || ((sector_size & (sector_size-1)) != 0))
337 info("checks passed\n");
338 dbg("sector_size 0x%x\n", sector_size);
339 dbg("sectors_per_cluster 0x%x\n", vs->sectors_per_cluster);
341 dir_entries = le16_to_cpu(vs->dir_entries);
342 reserved = le16_to_cpu(vs->reserved);
343 dbg("reserved 0x%x\n", reserved);
345 sect_count = le16_to_cpu(vs->sectors);
347 sect_count = le32_to_cpu(vs->total_sect);
348 dbg("sect_count 0x%x\n", sect_count);
350 fat_length = le16_to_cpu(vs->fat_length);
351 info("fat_length 0x%x\n", fat_length);
352 fat32_length = le32_to_cpu(vs->type.fat32.fat32_length);
353 info("fat32_length 0x%x\n", fat32_length);
356 fat_size = fat_length * vs->fats;
357 else if (fat32_length)
358 fat_size = fat32_length * vs->fats;
361 info("fat_size 0x%x\n", fat_size);
363 dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
364 (sector_size-1)) / sector_size;
365 info("dir_size 0x%x\n", dir_size);
367 cluster_count = sect_count - (reserved + fat_size + dir_size);
368 cluster_count /= vs->sectors_per_cluster;
369 info("cluster_count 0x%x\n", cluster_count);
372 if (!fat_length && fat32_length)
375 /* cluster_count tells us the format */
376 if (cluster_count < FAT12_MAX)
377 strcpy(id->type_version, "FAT12");
378 else if (cluster_count < FAT16_MAX)
379 strcpy(id->type_version, "FAT16");
383 /* the label may be an attribute in the root directory */
384 root_start = (reserved + fat_size) * sector_size;
385 dbg("root dir start 0x%" PRIx64 "\n", root_start);
386 root_dir_entries = le16_to_cpu(vs->dir_entries);
387 dbg("expected entries 0x%x\n", root_dir_entries);
389 buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
390 buf = volume_id_get_buffer(id, off + root_start, buf_size);
394 dir = (struct vfat_dir_entry*) buf;
396 fnlen = get_fat_attr_volume_id(filename, sizeof(filename), dir, root_dir_entries);
398 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
402 if (fnlen > 0 && memcmp(filename, "NO NAME ", 11) != 0) {
403 volume_id_set_label_raw(id, filename, fnlen);
404 volume_id_set_label_string(id, filename, fnlen);
405 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
406 volume_id_set_label_raw(id, vs->type.fat.label, 11);
407 volume_id_set_label_string(id, vs->type.fat.label, 11);
409 volume_id_set_uuid(id, vs->type.fat.serno, 0, UUID_DOS);
413 info("looking for FAT32\n");
415 * FAT32 should have a valid signature in the fsinfo block,
416 * but also allow all bytes set to '\0', because some volumes
417 * do not set the signature at all.
419 fsinfo_sect = le16_to_cpu(vs->type.fat32.fsinfo_sector);
420 buf = volume_id_get_buffer(id, off + (fsinfo_sect * sector_size), 0x200);
423 fsinfo = (struct fat32_fsinfo *) buf;
424 info("signature1: 0x%02x%02x%02x%02x\n",
425 fsinfo->signature1[0], fsinfo->signature1[1],
426 fsinfo->signature1[2], fsinfo->signature1[3]);
427 info("signature2: 0x%02x%02x%02x%02x\n",
428 fsinfo->signature2[0], fsinfo->signature2[1],
429 fsinfo->signature2[2], fsinfo->signature2[3]);
430 if (memcmp(fsinfo->signature1, "\x52\x52\x61\x41", 4) != 0 &&
431 memcmp(fsinfo->signature1, "\x00\x00\x00\x00", 4) != 0)
433 if (memcmp(fsinfo->signature2, "\x72\x72\x41\x61", 4) != 0 &&
434 memcmp(fsinfo->signature2, "\x00\x00\x00\x00", 4) != 0)
436 info("FAT32 signatures ok\n");
438 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
442 strcpy(id->type_version, "FAT32");
444 /* FAT32 root dir is a cluster chain like any other directory */
445 buf_size = vs->sectors_per_cluster * sector_size;
446 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
447 dbg("root dir cluster %u\n", root_cluster);
448 start_data_sect = reserved + fat_size;
453 uint32_t next_sect_off;
455 uint64_t fat_entry_off;
458 dbg("next cluster %u\n", next);
459 next_sect_off = (next - 2) * vs->sectors_per_cluster;
460 next_off = (start_data_sect + next_sect_off) * sector_size;
461 dbg("cluster offset 0x%" PRIx64 "\n", next_off);
464 buf = volume_id_get_buffer(id, off + next_off, buf_size);
468 dir = (struct vfat_dir_entry*) buf;
469 count = buf_size / sizeof(struct vfat_dir_entry);
470 dbg("expected entries 0x%x\n", count);
472 fnlen = get_fat_attr_volume_id(filename, sizeof(filename), dir, count);
477 fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
478 buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
482 /* set next cluster */
483 next = le32_to_cpu(*((uint32_t *) buf)) & 0x0fffffff;
484 if (next < 2 || next >= 0x0ffffff0)
488 dbg("reached maximum follow count of root cluster chain, give up\n");
490 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
494 if (fnlen > 0 && memcmp(filename, "NO NAME ", 11) != 0) {
495 volume_id_set_label_raw(id, filename, fnlen);
496 volume_id_set_label_string(id, filename, fnlen);
497 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
498 volume_id_set_label_raw(id, vs->type.fat32.label, 11);
499 volume_id_set_label_string(id, vs->type.fat32.label, 11);
501 volume_id_set_uuid(id, vs->type.fat32.serno, 0, UUID_DOS);
504 volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
506 /* we think this is fat, but we make sure no other signatures are found */
507 id->force_unique_result = 1;