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.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by Martin Husemann
16 * and Wolfgang Solfrank.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 * $NetBSD: fat.c,v 1.12 2000/10/10 20:24:52 is Exp $
33 * $FreeBSD: src/sbin/fsck_msdosfs/fat.c,v 1.1.2.1 2001/08/01 05:47:56 obrien Exp $
45 static int checkclnum(struct bootblock *, int, cl_t, cl_t *);
46 static int clustdiffer(cl_t, cl_t *, cl_t *, int);
47 static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *);
48 static int _readfat(int, struct bootblock *, int, u_char **);
51 * Check a cluster number for valid value
54 checkclnum(struct bootblock *boot, int fat, cl_t cl, cl_t *next)
56 if (*next >= (CLUST_RSRVD&boot->ClustMask))
57 *next |= ~boot->ClustMask;
58 if (*next == CLUST_FREE) {
62 if (*next == CLUST_BAD) {
66 if (*next < CLUST_FIRST
67 || (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
68 pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n",
70 *next < CLUST_RSRVD ? "out of range" : "reserved",
71 *next&boot->ClustMask);
72 if (ask(0, "Truncate")) {
82 * Read a FAT from disk. Returns 1 if successful, 0 otherwise.
85 _readfat(int fs, struct bootblock *boot, int no, u_char **buffer)
89 *buffer = malloc(boot->FATsecs * boot->BytesPerSec);
90 if (*buffer == NULL) {
91 perror("No space for FAT");
95 off = boot->ResSectors + no * boot->FATsecs;
96 off *= boot->BytesPerSec;
98 if (lseek(fs, off, SEEK_SET) != off) {
99 perror("Unable to read FAT");
103 if (read(fs, *buffer, boot->FATsecs * boot->BytesPerSec)
104 != boot->FATsecs * boot->BytesPerSec) {
105 perror("Unable to read FAT");
117 * Read a FAT and decode it into internal format
120 readfat(int fs, struct bootblock *boot, int no, struct fatEntry **fp)
122 struct fatEntry *fat;
127 boot->NumFree = boot->NumBad = 0;
129 if (!_readfat(fs, boot, no, &buffer))
132 fat = calloc(boot->NumClusters, sizeof(struct fatEntry));
134 perror("No space for FAT");
139 if (buffer[0] != boot->Media
140 || buffer[1] != 0xff || buffer[2] != 0xff
141 || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
142 || (boot->ClustMask == CLUST32_MASK
143 && ((buffer[3]&0x0f) != 0x0f
144 || buffer[4] != 0xff || buffer[5] != 0xff
145 || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
147 /* Windows 95 OSR2 (and possibly any later) changes
148 * the FAT signature to 0xXXffff7f for FAT16 and to
149 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
150 * filesystem is dirty if it doesn't reboot cleanly.
151 * Check this special condition before errorring out.
153 if (buffer[0] == boot->Media && buffer[1] == 0xff
155 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
156 || (boot->ClustMask == CLUST32_MASK
157 && buffer[3] == 0x0f && buffer[4] == 0xff
158 && buffer[5] == 0xff && buffer[6] == 0xff
159 && buffer[7] == 0x07)))
162 /* just some odd byte sequence in FAT */
164 switch (boot->ClustMask) {
166 pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
167 "FAT starts with odd byte sequence",
168 buffer[0], buffer[1], buffer[2], buffer[3],
169 buffer[4], buffer[5], buffer[6], buffer[7]);
172 pwarn("%s (%02x%02x%02x%02x)\n",
173 "FAT starts with odd byte sequence",
174 buffer[0], buffer[1], buffer[2], buffer[3]);
177 pwarn("%s (%02x%02x%02x)\n",
178 "FAT starts with odd byte sequence",
179 buffer[0], buffer[1], buffer[2]);
184 if (ask(1, "Correct"))
188 switch (boot->ClustMask) {
199 for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
200 switch (boot->ClustMask) {
202 fat[cl].next = p[0] + (p[1] << 8)
203 + (p[2] << 16) + (p[3] << 24);
204 fat[cl].next &= boot->ClustMask;
205 ret |= checkclnum(boot, no, cl, &fat[cl].next);
210 fat[cl].next = p[0] + (p[1] << 8);
211 ret |= checkclnum(boot, no, cl, &fat[cl].next);
216 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
217 ret |= checkclnum(boot, no, cl, &fat[cl].next);
219 if (cl >= boot->NumClusters)
221 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
222 ret |= checkclnum(boot, no, cl, &fat[cl].next);
235 * Get type of reserved cluster
240 if (cl == CLUST_FREE)
250 clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, int fatnum)
252 if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) {
253 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
254 if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD
255 && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD)
256 || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
257 pwarn("Cluster %u is marked %s with different indicators, ",
258 cl, rsrvdcltype(*cp1));
265 pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %d\n",
266 cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
267 if (ask(0, "use FAT 0's entry")) {
271 if (ask(0, "use FAT %d's entry", fatnum)) {
277 pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n",
278 cl, rsrvdcltype(*cp1), *cp2, fatnum);
279 if (ask(0, "Use continuation from FAT %d", fatnum)) {
283 if (ask(0, "Use mark from FAT 0")) {
289 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
290 pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %d\n",
291 cl, *cp1, rsrvdcltype(*cp2), fatnum);
292 if (ask(0, "Use continuation from FAT 0")) {
296 if (ask(0, "Use mark from FAT %d", fatnum)) {
302 pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %d\n",
303 cl, *cp1, *cp2, fatnum);
304 if (ask(0, "Use continuation from FAT 0")) {
308 if (ask(0, "Use continuation from FAT %d", fatnum)) {
316 * Compare two FAT copies in memory. Resolve any conflicts and merge them
317 * into the first one.
320 comparefat(struct bootblock *boot, struct fatEntry *first,
321 struct fatEntry *second, int fatnum)
326 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
327 if (first[cl].next != second[cl].next)
328 ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
333 clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
337 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
338 if (fat[p].head != head)
341 fat[p].next = fat[p].head = CLUST_FREE;
347 tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *trunc)
349 if (ask(0, "Clear chain starting at %u", head)) {
350 clearchain(boot, fat, head);
352 } else if (ask(0, "Truncate")) {
360 * Check a complete FAT in-memory for crosslinks
363 checkfat(struct bootblock *boot, struct fatEntry *fat)
371 * pass 1: figure out the cluster chains.
373 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
374 /* find next untravelled chain */
375 if (fat[head].head != 0 /* cluster already belongs to some chain */
376 || fat[head].next == CLUST_FREE
377 || fat[head].next == CLUST_BAD)
378 continue; /* skip it. */
380 /* follow the chain and mark all clusters on the way */
381 for (len = 0, p = head;
382 p >= CLUST_FIRST && p < boot->NumClusters;
388 /* the head record gets the length */
389 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
393 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
394 * we didn't know the real start of the chain then - would have treated partial
395 * chains as interlinked with their main chain)
397 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
398 /* find next untravelled chain */
399 if (fat[head].head != head)
402 /* follow the chain to its end (hopefully) */
404 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
406 if (fat[n].head != head)
411 if (n == CLUST_FREE || n >= CLUST_RSRVD) {
412 pwarn("Cluster chain starting at %u ends with cluster marked %s\n",
413 head, rsrvdcltype(n));
414 ret |= tryclear(boot, fat, head, &fat[p].next);
417 if (n < CLUST_FIRST || n >= boot->NumClusters) {
418 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
420 ret |= tryclear(boot, fat, head, &fat[p].next);
423 pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n",
424 head, fat[n].head, n);
425 conf = tryclear(boot, fat, head, &fat[p].next);
426 if (ask(0, "Clear chain starting at %u", h = fat[n].head)) {
427 if (conf == FSERROR) {
429 * Transfer the common chain to the one not cleared above.
432 p >= CLUST_FIRST && p < boot->NumClusters;
434 if (h != fat[p].head) {
436 * Have to reexamine this chain.
444 clearchain(boot, fat, h);
454 * Write out FATs encoding them from the internal format
457 writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
466 buffer = malloc(fatsz = boot->FATsecs * boot->BytesPerSec);
467 if (buffer == NULL) {
468 perror("No space for FAT");
471 memset(buffer, 0, fatsz);
475 *p++ = (u_char)boot->Media;
478 switch (boot->ClustMask) {
491 /* use same FAT signature as the old FAT has */
495 switch (boot->ClustMask) {
507 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
513 memcpy(p, old_fat, count);
518 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
519 switch (boot->ClustMask) {
521 if (fat[cl].next == CLUST_FREE)
523 *p++ = (u_char)fat[cl].next;
524 *p++ = (u_char)(fat[cl].next >> 8);
525 *p++ = (u_char)(fat[cl].next >> 16);
527 *p++ |= (fat[cl].next >> 24)&0x0f;
530 if (fat[cl].next == CLUST_FREE)
532 *p++ = (u_char)fat[cl].next;
533 *p++ = (u_char)(fat[cl].next >> 8);
536 if (fat[cl].next == CLUST_FREE)
538 if (cl + 1 < boot->NumClusters
539 && fat[cl + 1].next == CLUST_FREE)
541 *p++ = (u_char)fat[cl].next;
542 *p++ = (u_char)((fat[cl].next >> 8) & 0xf)
543 |(u_char)(fat[cl+1].next << 4);
544 *p++ = (u_char)(fat[++cl].next >> 4);
548 for (i = 0; i < boot->FATs; i++) {
549 off = boot->ResSectors + i * boot->FATsecs;
550 off *= boot->BytesPerSec;
551 if (lseek(fs, off, SEEK_SET) != off
552 || write(fs, buffer, fatsz) != fatsz) {
553 perror("Unable to write FAT");
554 ret = FSFATAL; /* Return immediately? XXX */
562 * Check a complete in-memory FAT for lost cluster chains
565 checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
571 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
572 /* find next untravelled chain */
573 if (fat[head].head != head
574 || fat[head].next == CLUST_FREE
575 || (fat[head].next >= CLUST_RSRVD
576 && fat[head].next < CLUST_EOFS)
577 || (fat[head].flags & FAT_USED))
580 pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n",
581 head, fat[head].length);
582 mod |= ret = reconnect(dosfs, boot, fat, head);
585 if (ret == FSERROR && ask(0, "Clear")) {
586 clearchain(boot, fat, head);
594 if (boot->FSFree != boot->NumFree) {
595 pwarn("Free space in FSInfo block (%d) not correct (%d)\n",
596 boot->FSFree, boot->NumFree);
598 boot->FSFree = boot->NumFree;
602 if (boot->NumFree && (boot->FSNext >= boot->NumClusters ||
603 fat[boot->FSNext].next != CLUST_FREE)) {
604 pwarn("Next free cluster in FSInfo block (%u) not free\n",
607 for (head = CLUST_FIRST; head < boot->NumClusters; head++)
608 if (fat[head].next == CLUST_FREE) {
615 mod |= writefsinfo(dosfs, boot);