2 * Copyright (C) 1995, 1996, 1997 Wolfgang Solfrank
3 * Copyright (c) 1995 Martin Husemann
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 #include <sys/cdefs.h>
29 __RCSID("$NetBSD: fat.c,v 1.12 2000/10/10 20:24:52 is Exp $");
30 static const char rcsid[] =
43 static int checkclnum(struct bootblock *, u_int, cl_t, cl_t *);
44 static int clustdiffer(cl_t, cl_t *, cl_t *, u_int);
45 static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *);
46 static int _readfat(int, struct bootblock *, u_int, u_char **);
49 * The first 2 FAT entries contain pseudo-cluster numbers with the following
52 * 31...... ........ ........ .......0
53 * rrrr1111 11111111 11111111 mmmmmmmm FAT32 entry 0
54 * rrrrsh11 11111111 11111111 11111xxx FAT32 entry 1
56 * 11111111 mmmmmmmm FAT16 entry 0
57 * sh111111 11111xxx FAT16 entry 1
60 * m = BPB media ID byte
61 * s = clean flag (1 = dismounted; 0 = still mounted)
62 * h = hard error flag (1 = ok; 0 = I/O error)
67 checkdirty(int fs, struct bootblock *boot)
73 if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK)
76 off = boot->bpbResSectors;
77 off *= boot->bpbBytesPerSec;
79 buffer = malloc(boot->bpbBytesPerSec);
81 perror("No space for FAT");
85 if (lseek(fs, off, SEEK_SET) != off) {
86 perror("Unable to read FAT");
90 if ((size_t)read(fs, buffer, boot->bpbBytesPerSec) !=
91 boot->bpbBytesPerSec) {
92 perror("Unable to read FAT");
97 * If we don't understand the FAT, then the file system must be
98 * assumed to be unclean.
100 if (buffer[0] != boot->bpbMedia || buffer[1] != 0xff)
102 if (boot->ClustMask == CLUST16_MASK) {
103 if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f)
106 if (buffer[2] != 0xff || (buffer[3] & 0x0f) != 0x0f
107 || (buffer[4] & 0xf8) != 0xf8 || buffer[5] != 0xff
108 || buffer[6] != 0xff || (buffer[7] & 0x03) != 0x03)
113 * Now check the actual clean flag (and the no-error flag).
115 if (boot->ClustMask == CLUST16_MASK) {
116 if ((buffer[3] & 0xc0) == 0xc0)
119 if ((buffer[7] & 0x0c) == 0x0c)
129 * Check a cluster number for valid value
132 checkclnum(struct bootblock *boot, u_int fat, cl_t cl, cl_t *next)
134 if (*next >= (CLUST_RSRVD&boot->ClustMask))
135 *next |= ~boot->ClustMask;
136 if (*next == CLUST_FREE) {
140 if (*next == CLUST_BAD) {
144 if (*next < CLUST_FIRST
145 || (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
146 pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n",
148 *next < CLUST_RSRVD ? "out of range" : "reserved",
149 *next&boot->ClustMask);
150 if (ask(0, "Truncate")) {
160 * Read a FAT from disk. Returns 1 if successful, 0 otherwise.
163 _readfat(int fs, struct bootblock *boot, u_int no, u_char **buffer)
167 *buffer = malloc(boot->FATsecs * boot->bpbBytesPerSec);
168 if (*buffer == NULL) {
169 perror("No space for FAT");
173 off = boot->bpbResSectors + no * boot->FATsecs;
174 off *= boot->bpbBytesPerSec;
176 if (lseek(fs, off, SEEK_SET) != off) {
177 perror("Unable to read FAT");
181 if ((size_t)read(fs, *buffer, boot->FATsecs * boot->bpbBytesPerSec)
182 != boot->FATsecs * boot->bpbBytesPerSec) {
183 perror("Unable to read FAT");
195 * Read a FAT and decode it into internal format
198 readfat(int fs, struct bootblock *boot, u_int no, struct fatEntry **fp)
200 struct fatEntry *fat;
206 boot->NumFree = boot->NumBad = 0;
208 if (!_readfat(fs, boot, no, &buffer))
211 fat = malloc(len = boot->NumClusters * sizeof(struct fatEntry));
213 perror("No space for FAT");
217 (void)memset(fat, 0, len);
219 if (buffer[0] != boot->bpbMedia
220 || buffer[1] != 0xff || buffer[2] != 0xff
221 || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
222 || (boot->ClustMask == CLUST32_MASK
223 && ((buffer[3]&0x0f) != 0x0f
224 || buffer[4] != 0xff || buffer[5] != 0xff
225 || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
227 /* Windows 95 OSR2 (and possibly any later) changes
228 * the FAT signature to 0xXXffff7f for FAT16 and to
229 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
230 * file system is dirty if it doesn't reboot cleanly.
231 * Check this special condition before errorring out.
233 if (buffer[0] == boot->bpbMedia && buffer[1] == 0xff
235 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
236 || (boot->ClustMask == CLUST32_MASK
237 && buffer[3] == 0x0f && buffer[4] == 0xff
238 && buffer[5] == 0xff && buffer[6] == 0xff
239 && buffer[7] == 0x07)))
242 /* just some odd byte sequence in FAT */
244 switch (boot->ClustMask) {
246 pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
247 "FAT starts with odd byte sequence",
248 buffer[0], buffer[1], buffer[2], buffer[3],
249 buffer[4], buffer[5], buffer[6], buffer[7]);
252 pwarn("%s (%02x%02x%02x%02x)\n",
253 "FAT starts with odd byte sequence",
254 buffer[0], buffer[1], buffer[2], buffer[3]);
257 pwarn("%s (%02x%02x%02x)\n",
258 "FAT starts with odd byte sequence",
259 buffer[0], buffer[1], buffer[2]);
264 if (ask(1, "Correct"))
268 switch (boot->ClustMask) {
279 for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
280 switch (boot->ClustMask) {
282 fat[cl].next = p[0] + (p[1] << 8)
283 + (p[2] << 16) + (p[3] << 24);
284 fat[cl].next &= boot->ClustMask;
285 ret |= checkclnum(boot, no, cl, &fat[cl].next);
290 fat[cl].next = p[0] + (p[1] << 8);
291 ret |= checkclnum(boot, no, cl, &fat[cl].next);
296 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
297 ret |= checkclnum(boot, no, cl, &fat[cl].next);
299 if (cl >= boot->NumClusters)
301 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
302 ret |= checkclnum(boot, no, cl, &fat[cl].next);
319 * Get type of reserved cluster
324 if (cl == CLUST_FREE)
334 clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, u_int fatnum)
336 if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) {
337 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
338 if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD
339 && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD)
340 || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
341 pwarn("Cluster %u is marked %s with different indicators\n",
342 cl, rsrvdcltype(*cp1));
349 pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %u\n",
350 cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
351 if (ask(0, "Use FAT 0's entry")) {
355 if (ask(0, "Use FAT %u's entry", fatnum)) {
361 pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n",
362 cl, rsrvdcltype(*cp1), *cp2, fatnum);
363 if (ask(0, "Use continuation from FAT %u", fatnum)) {
367 if (ask(0, "Use mark from FAT 0")) {
373 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
374 pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %u\n",
375 cl, *cp1, rsrvdcltype(*cp2), fatnum);
376 if (ask(0, "Use continuation from FAT 0")) {
380 if (ask(0, "Use mark from FAT %d", fatnum)) {
386 pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %u\n",
387 cl, *cp1, *cp2, fatnum);
388 if (ask(0, "Use continuation from FAT 0")) {
392 if (ask(0, "Use continuation from FAT %u", fatnum)) {
400 * Compare two FAT copies in memory. Resolve any conflicts and merge them
401 * into the first one.
404 comparefat(struct bootblock *boot, struct fatEntry *first,
405 struct fatEntry *second, u_int fatnum)
410 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
411 if (first[cl].next != second[cl].next)
412 ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
417 clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
421 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
422 if (fat[p].head != head)
425 fat[p].next = fat[p].head = CLUST_FREE;
431 tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *trunc)
433 if (ask(0, "Clear chain starting at %u", head)) {
434 clearchain(boot, fat, head);
436 } else if (ask(0, "Truncate")) {
444 * Check a complete FAT in-memory for crosslinks
447 checkfat(struct bootblock *boot, struct fatEntry *fat)
455 * pass 1: figure out the cluster chains.
457 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
458 /* find next untravelled chain */
459 if (fat[head].head != 0 /* cluster already belongs to some chain */
460 || fat[head].next == CLUST_FREE
461 || fat[head].next == CLUST_BAD)
462 continue; /* skip it. */
464 /* follow the chain and mark all clusters on the way */
465 for (len = 0, p = head;
466 p >= CLUST_FIRST && p < boot->NumClusters;
472 /* the head record gets the length */
473 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
477 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
478 * we didn't know the real start of the chain then - would have treated partial
479 * chains as interlinked with their main chain)
481 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
482 /* find next untravelled chain */
483 if (fat[head].head != head)
486 /* follow the chain to its end (hopefully) */
488 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
490 if (fat[n].head != head)
495 if (n == CLUST_FREE || n >= CLUST_RSRVD) {
496 pwarn("Cluster chain starting at %u ends with cluster marked %s\n",
497 head, rsrvdcltype(n));
498 ret |= tryclear(boot, fat, head, &fat[p].next);
501 if (n < CLUST_FIRST || n >= boot->NumClusters) {
502 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
504 ret |= tryclear(boot, fat, head, &fat[p].next);
507 pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n",
508 head, fat[n].head, n);
509 conf = tryclear(boot, fat, head, &fat[p].next);
510 if (ask(0, "Clear chain starting at %u", h = fat[n].head)) {
511 if (conf == FSERROR) {
513 * Transfer the common chain to the one not cleared above.
516 p >= CLUST_FIRST && p < boot->NumClusters;
518 if (h != fat[p].head) {
520 * Have to reexamine this chain.
528 clearchain(boot, fat, h);
538 * Write out FATs encoding them from the internal format
541 writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
550 buffer = malloc(fatsz = boot->FATsecs * boot->bpbBytesPerSec);
551 if (buffer == NULL) {
552 perror("No space for FAT");
555 memset(buffer, 0, fatsz);
559 *p++ = (u_char)boot->bpbMedia;
562 switch (boot->ClustMask) {
575 /* use same FAT signature as the old FAT has */
579 switch (boot->ClustMask) {
591 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
597 memcpy(p, old_fat, count);
602 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
603 switch (boot->ClustMask) {
605 if (fat[cl].next == CLUST_FREE)
607 *p++ = (u_char)fat[cl].next;
608 *p++ = (u_char)(fat[cl].next >> 8);
609 *p++ = (u_char)(fat[cl].next >> 16);
611 *p++ |= (fat[cl].next >> 24)&0x0f;
614 if (fat[cl].next == CLUST_FREE)
616 *p++ = (u_char)fat[cl].next;
617 *p++ = (u_char)(fat[cl].next >> 8);
620 if (fat[cl].next == CLUST_FREE)
622 if (cl + 1 < boot->NumClusters
623 && fat[cl + 1].next == CLUST_FREE)
625 *p++ = (u_char)fat[cl].next;
626 *p++ = (u_char)((fat[cl].next >> 8) & 0xf)
627 |(u_char)(fat[cl+1].next << 4);
628 *p++ = (u_char)(fat[++cl].next >> 4);
632 for (i = 0; i < boot->bpbFATs; i++) {
633 off = boot->bpbResSectors + i * boot->FATsecs;
634 off *= boot->bpbBytesPerSec;
635 if (lseek(fs, off, SEEK_SET) != off
636 || (size_t)write(fs, buffer, fatsz) != fatsz) {
637 perror("Unable to write FAT");
638 ret = FSFATAL; /* Return immediately? XXX */
646 * Check a complete in-memory FAT for lost cluster chains
649 checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
655 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
656 /* find next untravelled chain */
657 if (fat[head].head != head
658 || fat[head].next == CLUST_FREE
659 || (fat[head].next >= CLUST_RSRVD
660 && fat[head].next < CLUST_EOFS)
661 || (fat[head].flags & FAT_USED))
664 pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n",
665 head, fat[head].length);
666 mod |= ret = reconnect(dosfs, boot, fat, head);
669 if (ret == FSERROR && ask(0, "Clear")) {
670 clearchain(boot, fat, head);
676 if (boot->bpbFSInfo) {
678 if (boot->FSFree != 0xffffffffU &&
679 boot->FSFree != boot->NumFree) {
680 pwarn("Free space in FSInfo block (%u) not correct (%u)\n",
681 boot->FSFree, boot->NumFree);
683 boot->FSFree = boot->NumFree;
688 mod |= writefsinfo(dosfs, boot);