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"
28 #include "libvolume_id-private.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 #define VFAT_LFN_SEQ_MASK 0x3f
40 #define VFAT_LFN_SEQ_LAST 0x40
41 #define VFAT_LFN_SEQ_MAX 20
42 #define VFAT_LFN_CHARS_PER_ENTRY (5 + 6 + 2)
43 #define VFAT_LOWERCASE_NAME 0x10
44 #define VFAT_LOWERCASE_EXT 0x08
46 struct vfat_super_block {
50 uint8_t sectors_per_cluster;
62 struct fat_super_block {
70 struct fat32_super_block {
71 uint32_t fat32_length;
74 uint32_t root_cluster;
75 uint16_t fsinfo_sector;
77 uint16_t reserved2[6];
89 uint8_t signature1[4];
90 uint32_t reserved1[120];
91 uint8_t signature2[4];
92 uint32_t free_clusters;
93 uint32_t next_cluster;
94 uint32_t reserved2[4];
97 struct vfat_dir_entry {
101 uint8_t fine_time_creat;
105 uint16_t cluster_high;
108 uint16_t cluster_low;
113 struct vfat_lfn_entry {
124 static uint8_t fat_lfn_checksum(const uint8_t name[11])
129 /* http://en.wikipedia.org/wiki/File_Allocation_Table */
130 for (i = 0; i < 11; i++)
131 cksum = ((cksum & 1) ? 0x80 : 0) + (cksum >> 1) + name[i];
136 static size_t fat_read_lfn(uint8_t *filename, size_t fnsize,
137 struct vfat_dir_entry *dir,
138 struct vfat_dir_entry *entry)
140 uint8_t buffer[VFAT_LFN_SEQ_MAX * VFAT_LFN_CHARS_PER_ENTRY * 2];
141 uint8_t expected_seq = 1;
146 cksum = fat_lfn_checksum(entry->name);
148 while (--entry >= dir) {
149 struct vfat_lfn_entry *lfn = (struct vfat_lfn_entry *) entry;
151 if (expected_seq > VFAT_LFN_SEQ_MAX)
154 if ((lfn->attr & FAT_ATTR_MASK) != FAT_ATTR_LONG_NAME)
157 if (lfn->cksum != cksum)
160 if ((lfn->seq & VFAT_LFN_SEQ_MASK) != expected_seq++)
163 if (lfn->cluster != 0)
166 /* extra paranoia -- should never happen */
167 if (len + sizeof(lfn->name0) + sizeof(lfn->name1) +
168 sizeof(lfn->name2) > sizeof(buffer))
171 memcpy (&buffer[len], lfn->name0, sizeof(lfn->name0));
172 len += sizeof(lfn->name0);
173 memcpy (&buffer[len], lfn->name1, sizeof(lfn->name1));
174 len += sizeof(lfn->name1);
175 memcpy (&buffer[len], lfn->name2, sizeof(lfn->name2));
176 len += sizeof(lfn->name2);
178 if (lfn->seq & VFAT_LFN_SEQ_LAST) {
179 fnlen = volume_id_set_unicode16(filename, fnsize, buffer, LE, len);
187 static size_t fat_read_filename(uint8_t *filename, size_t fnsize,
188 struct vfat_dir_entry *dir, struct vfat_dir_entry *entry)
193 /* check if maybe we have LFN entries */
194 len = fat_read_lfn(filename, fnsize, dir, entry);
198 /* else, read the normal 8.3 name */
199 for (i = 0; i < 11; i++) {
200 if (entry->lowercase & ((i < 8) ? VFAT_LOWERCASE_NAME : VFAT_LOWERCASE_EXT))
201 filename[i] = tolower(entry->name[i]);
203 filename[i] = entry->name[i];
208 filename[len] = '\0';
212 /* fills filename, returns string length */
213 static size_t get_fat_attr_volume_id(uint8_t *filename, size_t fnsize,
214 struct vfat_dir_entry *dir, unsigned int count)
218 for (i = 0; i < count; i++) {
220 if (dir[i].name[0] == 0x00) {
226 if (dir[i].name[0] == FAT_ENTRY_FREE)
230 if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
233 if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
234 /* labels do not have file data */
235 if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
238 dbg("found ATTR_VOLUME_ID id in root dir\n");
239 return fat_read_filename(filename, fnsize, dir, &dir[i]);
242 dbg("skip dir entry\n");
248 int volume_id_probe_vfat(struct volume_id *id, uint64_t off, uint64_t size)
250 uint8_t filename[255 * 3];
251 struct vfat_super_block *vs;
252 struct vfat_dir_entry *dir;
253 struct fat32_fsinfo *fsinfo;
254 uint16_t sector_size;
255 uint16_t dir_entries;
259 uint32_t root_cluster;
261 uint32_t cluster_count;
263 uint32_t fat32_length;
265 uint32_t start_data_sect;
266 uint16_t root_dir_entries;
267 uint16_t fsinfo_sect;
274 info("probing at offset 0x%llx\n", (unsigned long long) off);
276 buf = volume_id_get_buffer(id, off, 0x400);
280 /* check signature */
281 if (buf[510] != 0x55 || buf[511] != 0xaa)
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 /* some old floppies don't have a magic, expect the boot jump address to match */
305 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
306 vs->boot_jump[0] != 0xe9)
310 /* reserverd sector count */
319 if (vs->media < 0xf8 && vs->media != 0xf0)
322 /* cluster size check */
323 if (vs->sectors_per_cluster == 0 ||
324 (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
327 /* sector size check */
328 sector_size = le16_to_cpu(vs->sector_size);
329 if (sector_size == 0 || ((sector_size & (sector_size-1)) != 0))
332 dbg("sector_size 0x%x\n", sector_size);
333 dbg("sectors_per_cluster 0x%x\n", vs->sectors_per_cluster);
335 dir_entries = le16_to_cpu(vs->dir_entries);
336 reserved = le16_to_cpu(vs->reserved);
337 dbg("reserved 0x%x\n", reserved);
339 sect_count = le16_to_cpu(vs->sectors);
341 sect_count = le32_to_cpu(vs->total_sect);
342 dbg("sect_count 0x%x\n", sect_count);
344 fat_length = le16_to_cpu(vs->fat_length);
345 dbg("fat_length 0x%x\n", fat_length);
346 fat32_length = le32_to_cpu(vs->type.fat32.fat32_length);
347 dbg("fat32_length 0x%x\n", fat32_length);
350 fat_size = fat_length * vs->fats;
351 else if (fat32_length)
352 fat_size = fat32_length * vs->fats;
355 dbg("fat_size 0x%x\n", fat_size);
357 dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
358 (sector_size-1)) / sector_size;
359 dbg("dir_size 0x%x\n", dir_size);
361 cluster_count = sect_count - (reserved + fat_size + dir_size);
362 cluster_count /= vs->sectors_per_cluster;
363 dbg("cluster_count 0x%x\n", cluster_count);
366 if (!fat_length && fat32_length)
369 /* cluster_count tells us the format */
370 if (cluster_count < FAT12_MAX)
371 strcpy(id->type_version, "FAT12");
372 else if (cluster_count < FAT16_MAX)
373 strcpy(id->type_version, "FAT16");
377 /* the label may be an attribute in the root directory */
378 root_start = (reserved + fat_size) * sector_size;
379 dbg("root dir start 0x%llx\n", (unsigned long long) root_start);
380 root_dir_entries = le16_to_cpu(vs->dir_entries);
381 dbg("expected entries 0x%x\n", root_dir_entries);
383 buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
384 buf = volume_id_get_buffer(id, off + root_start, buf_size);
388 dir = (struct vfat_dir_entry*) buf;
390 fnlen = get_fat_attr_volume_id(filename, sizeof(filename), dir, root_dir_entries);
392 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
396 if (fnlen > 0 && memcmp(filename, "NO NAME ", 11) != 0) {
397 volume_id_set_label_raw(id, filename, fnlen);
398 volume_id_set_label_string(id, filename, fnlen);
399 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
400 volume_id_set_label_raw(id, vs->type.fat.label, 11);
401 volume_id_set_label_string(id, vs->type.fat.label, 11);
403 volume_id_set_uuid(id, vs->type.fat.serno, 0, UUID_DOS);
407 /* FAT32 should have a valid signature in the fsinfo block */
408 fsinfo_sect = le16_to_cpu(vs->type.fat32.fsinfo_sector);
409 buf = volume_id_get_buffer(id, off + (fsinfo_sect * sector_size), 0x200);
412 fsinfo = (struct fat32_fsinfo *) buf;
413 if (memcmp(fsinfo->signature1, "\x52\x52\x61\x41", 4) != 0)
415 if (memcmp(fsinfo->signature2, "\x72\x72\x41\x61", 4) != 0)
418 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
422 strcpy(id->type_version, "FAT32");
424 /* FAT32 root dir is a cluster chain like any other directory */
425 buf_size = vs->sectors_per_cluster * sector_size;
426 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
427 dbg("root dir cluster %u\n", root_cluster);
428 start_data_sect = reserved + fat_size;
433 uint32_t next_sect_off;
435 uint64_t fat_entry_off;
438 dbg("next cluster %u\n", next);
439 next_sect_off = (next - 2) * vs->sectors_per_cluster;
440 next_off = (start_data_sect + next_sect_off) * sector_size;
441 dbg("cluster offset 0x%llx\n", (unsigned long long) next_off);
444 buf = volume_id_get_buffer(id, off + next_off, buf_size);
448 dir = (struct vfat_dir_entry*) buf;
449 count = buf_size / sizeof(struct vfat_dir_entry);
450 dbg("expected entries 0x%x\n", count);
452 fnlen = get_fat_attr_volume_id(filename, sizeof(filename), dir, count);
457 fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
458 buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
462 /* set next cluster */
463 next = le32_to_cpu(*((uint32_t *) buf)) & 0x0fffffff;
464 if (next < 2 || next >= 0x0ffffff0)
468 dbg("reached maximum follow count of root cluster chain, give up\n");
470 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
474 if (fnlen > 0 && memcmp(filename, "NO NAME ", 11) != 0) {
475 volume_id_set_label_raw(id, filename, fnlen);
476 volume_id_set_label_string(id, filename, fnlen);
477 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
478 volume_id_set_label_raw(id, vs->type.fat32.label, 11);
479 volume_id_set_label_string(id, vs->type.fat32.label, 11);
481 volume_id_set_uuid(id, vs->type.fat32.serno, 0, UUID_DOS);
484 volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);