2 * Copyright (C) 1999 by Andries Brouwer
3 * Copyright (C) 1999, 2000, 2003 by Theodore Ts'o
4 * Copyright (C) 2001 by Andreas Dilger
5 * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
6 * Copyright (C) 2008 Karel Zak <kzak@redhat.com>
8 * This file may be redistributed under the terms of the
9 * GNU Lesser General Public License.
19 #include "superblocks.h"
21 /* Yucky misaligned values */
22 struct vfat_super_block {
23 /* 00*/ unsigned char vs_ignored[3];
24 /* 03*/ unsigned char vs_sysid[8];
25 /* 0b*/ unsigned char vs_sector_size[2];
26 /* 0d*/ uint8_t vs_cluster_size;
27 /* 0e*/ uint16_t vs_reserved;
28 /* 10*/ uint8_t vs_fats;
29 /* 11*/ unsigned char vs_dir_entries[2];
30 /* 13*/ unsigned char vs_sectors[2];
31 /* 15*/ unsigned char vs_media;
32 /* 16*/ uint16_t vs_fat_length;
33 /* 18*/ uint16_t vs_secs_track;
34 /* 1a*/ uint16_t vs_heads;
35 /* 1c*/ uint32_t vs_hidden;
36 /* 20*/ uint32_t vs_total_sect;
37 /* 24*/ uint32_t vs_fat32_length;
38 /* 28*/ uint16_t vs_flags;
39 /* 2a*/ uint8_t vs_version[2];
40 /* 2c*/ uint32_t vs_root_cluster;
41 /* 30*/ uint16_t vs_fsinfo_sector;
42 /* 32*/ uint16_t vs_backup_boot;
43 /* 34*/ uint16_t vs_reserved2[6];
44 /* 40*/ unsigned char vs_unknown[3];
45 /* 43*/ unsigned char vs_serno[4];
46 /* 47*/ unsigned char vs_label[11];
47 /* 52*/ unsigned char vs_magic[8];
48 /* 5a*/ unsigned char vs_dummy2[0x1fe - 0x5a];
49 /*1fe*/ unsigned char vs_pmagic[2];
50 } __attribute__((packed));
52 /* Yucky misaligned values */
53 struct msdos_super_block {
54 /* 00*/ unsigned char ms_ignored[3];
55 /* 03*/ unsigned char ms_sysid[8];
56 /* 0b*/ unsigned char ms_sector_size[2];
57 /* 0d*/ uint8_t ms_cluster_size;
58 /* 0e*/ uint16_t ms_reserved;
59 /* 10*/ uint8_t ms_fats;
60 /* 11*/ unsigned char ms_dir_entries[2];
61 /* 13*/ unsigned char ms_sectors[2]; /* =0 iff V3 or later */
62 /* 15*/ unsigned char ms_media;
63 /* 16*/ uint16_t ms_fat_length; /* Sectors per FAT */
64 /* 18*/ uint16_t ms_secs_track;
65 /* 1a*/ uint16_t ms_heads;
66 /* 1c*/ uint32_t ms_hidden;
68 /* 20*/ uint32_t ms_total_sect; /* iff ms_sectors == 0 */
70 /* 24*/ unsigned char ms_unknown[3]; /* Phys drive no., resvd, V4 sig (0x29) */
71 /* 27*/ unsigned char ms_serno[4];
72 /* 2b*/ unsigned char ms_label[11];
73 /* 36*/ unsigned char ms_magic[8];
74 /* 3e*/ unsigned char ms_dummy2[0x1fe - 0x3e];
75 /*1fe*/ unsigned char ms_pmagic[2];
76 } __attribute__((packed));
78 struct vfat_dir_entry {
85 uint16_t cluster_high;
90 } __attribute__((packed));
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];
99 } __attribute__((packed));
101 /* maximum number of clusters */
102 #define FAT12_MAX 0xFF4
103 #define FAT16_MAX 0xFFF4
104 #define FAT32_MAX 0x0FFFFFF6
106 #define FAT_ATTR_VOLUME_ID 0x08
107 #define FAT_ATTR_DIR 0x10
108 #define FAT_ATTR_LONG_NAME 0x0f
109 #define FAT_ATTR_MASK 0x3f
110 #define FAT_ENTRY_FREE 0xe5
112 static const char *no_name = "NO NAME ";
114 #define unaligned_le16(x) \
115 (((unsigned char *) x)[0] + (((unsigned char *) x)[1] << 8))
118 * Look for LABEL (name) in the FAT root directory.
120 static unsigned char *search_fat_label(blkid_probe pr,
121 uint64_t offset, uint32_t entries)
123 struct vfat_dir_entry *ent, *dir = NULL;
127 printf("\tlook for label in root-dir "
128 "(entries: %d, offset: %jd)\n", entries, offset));
130 if (!blkid_probe_is_tiny(pr)) {
131 /* large disk, read whole root directory */
132 dir = (struct vfat_dir_entry *)
133 blkid_probe_get_buffer(pr,
135 (blkid_loff_t) entries *
136 sizeof(struct vfat_dir_entry));
141 for (i = 0; i < entries; i++) {
143 * The root directory could be relatively large (4-16kB).
144 * Fortunately, the LABEL is usually the first entry in the
145 * directory. On tiny disks we call read() per entry.
148 ent = (struct vfat_dir_entry *)
149 blkid_probe_get_buffer(pr,
150 (blkid_loff_t) offset + (i *
151 sizeof(struct vfat_dir_entry)),
152 sizeof(struct vfat_dir_entry));
156 if (!ent || ent->name[0] == 0x00)
159 if ((ent->name[0] == FAT_ENTRY_FREE) ||
160 (ent->cluster_high != 0 || ent->cluster_low != 0) ||
161 ((ent->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME))
164 if ((ent->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) ==
165 FAT_ATTR_VOLUME_ID) {
167 printf("\tfound fs LABEL at entry %d\n", i));
174 static int fat_valid_superblock(const struct blkid_idmag *mag,
175 struct msdos_super_block *ms,
176 struct vfat_super_block *vs,
177 uint32_t *cluster_count, uint32_t *fat_size)
179 uint16_t sector_size, dir_entries, reserved;
180 uint32_t sect_count, __fat_size, dir_size, __cluster_count, fat_length;
183 /* extra check for FATs without magic strings */
185 /* Old floppies have a valid MBR signature */
186 if (ms->ms_pmagic[0] != 0x55 || ms->ms_pmagic[1] != 0xAA)
190 * OS/2 and apparently DFSee will place a FAT12/16-like
191 * pseudo-superblock in the first 512 bytes of non-FAT
192 * filesystems --- at least JFS and HPFS, and possibly others.
193 * So we explicitly check for those filesystems at the
194 * FAT12/16 filesystem magic field identifier, and if they are
195 * present, we rule this out as a FAT filesystem, despite the
196 * FAT-like pseudo-header.
198 if ((memcmp(ms->ms_magic, "JFS ", 8) == 0) ||
199 (memcmp(ms->ms_magic, "HPFS ", 8) == 0))
203 /* fat counts(Linux kernel expects at least 1 FAT table) */
206 if (!ms->ms_reserved)
208 if (!(0xf8 <= ms->ms_media || ms->ms_media == 0xf0))
210 if (!is_power_of_2(ms->ms_cluster_size))
213 sector_size = unaligned_le16(&ms->ms_sector_size);
214 if (!is_power_of_2(sector_size) ||
215 sector_size < 512 || sector_size > 4096)
218 dir_entries = unaligned_le16(&ms->ms_dir_entries);
219 reserved = le16_to_cpu(ms->ms_reserved);
220 sect_count = unaligned_le16(&ms->ms_sectors);
223 sect_count = le32_to_cpu(ms->ms_total_sect);
225 fat_length = le16_to_cpu(ms->ms_fat_length);
227 fat_length = le32_to_cpu(vs->vs_fat32_length);
229 __fat_size = fat_length * ms->ms_fats;
230 dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
231 (sector_size-1)) / sector_size;
233 __cluster_count = (sect_count - (reserved + __fat_size + dir_size)) /
235 if (!ms->ms_fat_length && vs->vs_fat32_length)
236 max_count = FAT32_MAX;
238 max_count = __cluster_count > FAT12_MAX ? FAT16_MAX : FAT12_MAX;
240 if (__cluster_count > max_count)
244 *fat_size = __fat_size;
246 *cluster_count = __cluster_count;
248 return 1; /* valid */
252 * This function is used by MBR partition table parser to avoid
253 * misinterpretation of FAT filesystem.
255 /*static int blkid_probe_is_vfat(blkid_probe pr)
257 struct vfat_super_block *vs;
258 struct msdos_super_block *ms;
259 const struct blkid_idmag *mag = NULL;
261 if (blkid_probe_get_idmag(pr, &vfat_idinfo, NULL, &mag) || !mag)
264 ms = blkid_probe_get_sb(pr, mag, struct msdos_super_block);
267 vs = blkid_probe_get_sb(pr, mag, struct vfat_super_block);
271 return fat_valid_superblock(mag, ms, vs, NULL, NULL);
273 static struct vfat_super_block vs;
274 static struct msdos_super_block ms;
276 static int set_label(blkid_probe pr, unsigned char *vol_label)
280 for (c = vol_label + 10; c >= vol_label && *c == ' '; c--)
286 return blkid_probe_set_label(pr, vol_label, 11);
289 /* FAT label extraction from the root directory taken from Kay
290 * Sievers's volume_id library */
291 static int probe_vfat(blkid_probe pr, const struct blkid_idmag *mag)
293 struct vfat_super_block *_vs;
294 struct msdos_super_block *_ms;
295 const unsigned char *vol_label = 0;
296 unsigned char *vol_serno = NULL, vol_label_buf[11];
297 uint16_t sector_size = 0, reserved;
298 uint32_t cluster_count, fat_size;
299 const char *version = NULL;
301 _ms = blkid_probe_get_sb(pr, mag, struct msdos_super_block);
304 _vs = blkid_probe_get_sb(pr, mag, struct vfat_super_block);
307 memcpy(&ms, _ms, sizeof(struct vfat_super_block));
308 memcpy(&vs, _vs, sizeof(struct msdos_super_block));
309 if (!fat_valid_superblock(mag, &ms, &vs, &cluster_count, &fat_size))
312 sector_size = unaligned_le16(&ms.ms_sector_size);
313 reserved = le16_to_cpu(ms.ms_reserved);
315 if (ms.ms_fat_length) {
316 /* the label may be an attribute in the root directory */
317 uint32_t root_start = (reserved + fat_size) * sector_size;
318 uint32_t root_dir_entries = unaligned_le16(&vs.vs_dir_entries);
320 vol_label = search_fat_label(pr, root_start, root_dir_entries);
322 memcpy(vol_label_buf, vol_label, 11);
323 vol_label = vol_label_buf;
326 if (!vol_label || !memcmp(vol_label, no_name, 11))
327 vol_label = ms.ms_label;
328 vol_serno = ms.ms_serno;
330 blkid_probe_set_value(pr, "SEC_TYPE", (unsigned char *) "msdos",
333 if (cluster_count < FAT12_MAX)
335 else if (cluster_count < FAT16_MAX)
338 } else if (vs.vs_fat32_length) {
340 uint16_t fsinfo_sect;
343 /* Search the FAT32 root dir for the label attribute */
344 uint32_t buf_size = vs.vs_cluster_size * sector_size;
345 uint32_t start_data_sect = reserved + fat_size;
346 uint32_t entries = le32_to_cpu(vs.vs_fat32_length) *
347 sector_size / sizeof(uint32_t);
348 uint32_t next = le32_to_cpu(vs.vs_root_cluster);
350 while (next && next < entries && --maxloop) {
351 uint32_t next_sect_off;
352 uint64_t next_off, fat_entry_off;
355 next_sect_off = (next - 2) * le32_to_cpu(vs.vs_cluster_size);
356 next_off = (uint64_t)(start_data_sect + next_sect_off) *
359 count = buf_size / sizeof(struct vfat_dir_entry);
361 vol_label = search_fat_label(pr, next_off, count);
363 memcpy(vol_label_buf, vol_label, 11);
364 vol_label = vol_label_buf;
369 fat_entry_off = ((uint64_t) reserved * sector_size) +
370 (next * sizeof(uint32_t));
371 buf = blkid_probe_get_buffer(pr, fat_entry_off, buf_size);
375 /* set next cluster */
376 next = le32_to_cpu(*((uint32_t *) buf)) & 0x0fffffff;
381 if (!vol_label || !memcmp(vol_label, no_name, 11))
383 vol_serno = vs.vs_serno;
386 * FAT32 should have a valid signature in the fsinfo block,
387 * but also allow all bytes set to '\0', because some volumes
388 * do not set the signature at all.
390 fsinfo_sect = le16_to_cpu(vs.vs_fsinfo_sector);
392 struct fat32_fsinfo *fsinfo;
394 buf = blkid_probe_get_buffer(pr,
395 (blkid_loff_t) fsinfo_sect * sector_size,
396 sizeof(struct fat32_fsinfo));
400 fsinfo = (struct fat32_fsinfo *) buf;
401 if (memcmp(fsinfo->signature1, "\x52\x52\x61\x41", 4) != 0 &&
402 memcmp(fsinfo->signature1, "\x52\x52\x64\x41", 4) != 0 &&
403 memcmp(fsinfo->signature1, "\x00\x00\x00\x00", 4) != 0)
405 if (memcmp(fsinfo->signature2, "\x72\x72\x41\x61", 4) != 0 &&
406 memcmp(fsinfo->signature2, "\x00\x00\x00\x00", 4) != 0)
411 if (vol_label && memcmp(vol_label, no_name, 11))
412 set_label(pr, (unsigned char *) vol_label);
414 /* We can't just print them as %04X, because they are unaligned */
416 blkid_probe_sprintf_uuid(pr, vol_serno, 4, "%02x%02x-%02x%02x",
417 vol_serno[3], vol_serno[2], vol_serno[1], vol_serno[0]);
419 blkid_probe_set_version(pr, version);
425 const struct blkid_idinfo vfat_idinfo =
428 .usage = BLKID_USAGE_FILESYSTEM,
429 .probefunc = probe_vfat,
432 { .magic = "MSWIN", .len = 5, .sboff = 0x52 },
433 { .magic = "FAT32 ", .len = 8, .sboff = 0x52 },
434 { .magic = "MSDOS", .len = 5, .sboff = 0x36 },
435 { .magic = "FAT16 ", .len = 8, .sboff = 0x36 },
436 { .magic = "FAT12 ", .len = 8, .sboff = 0x36 },
437 { .magic = "FAT ", .len = 8, .sboff = 0x36 },
438 { .magic = "\353", .len = 1, },
439 { .magic = "\351", .len = 1, },
440 { .magic = "\125\252", .len = 2, .sboff = 0x1fe },