1 /*
2 * Copyright (C) 1995, 1996, 1997 Wolfgang Solfrank
3 * Copyright (c) 1995 Martin Husemann
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
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 *
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.
24 */
25
26
27 #include <sys/cdefs.h>
28 #ifndef lint
29 __RCSID("$NetBSD: fat.c,v 1.18 2006/06/05 16:51:18 christos Exp $");
30 static const char rcsid[] =
31 "$FreeBSD: stable/10/sbin/fsck_msdosfs/fat.c 268968 2014-07-21 23:23:20Z pfg $";
32 #endif /* not lint */
33
34 #include <stdlib.h>
35 #include <string.h>
36 #include <ctype.h>
37 #include <stdio.h>
38 #include <unistd.h>
39
40 #include "ext.h"
41 #include "fsutil.h"
42
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 **);
47
48 /*-
49 * The first 2 FAT entries contain pseudo-cluster numbers with the following
50 * layout:
51 *
52 * 31...... ........ ........ .......0
53 * rrrr1111 11111111 11111111 mmmmmmmm FAT32 entry 0
54 * rrrrsh11 11111111 11111111 11111xxx FAT32 entry 1
55 *
56 * 11111111 mmmmmmmm FAT16 entry 0
57 * sh111111 11111xxx FAT16 entry 1
58 *
59 * r = reserved
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)
63 * x = any value ok
64 */
65
66 int
checkdirty(int fs,struct bootblock * boot)67 checkdirty(int fs, struct bootblock *boot)
68 {
69 off_t off;
70 u_char *buffer;
71 int ret = 0;
72 size_t len;
73
74 if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK)
75 return 0;
76
77 off = boot->bpbResSectors;
78 off *= boot->bpbBytesPerSec;
79
80 buffer = malloc(len = boot->bpbBytesPerSec);
81 if (buffer == NULL) {
82 perr("No space for FAT sectors (%zu)", len);
83 return 1;
84 }
85
86 if (lseek(fs, off, SEEK_SET) != off) {
87 perr("Unable to read FAT");
88 goto err;
89 }
90
91 if ((size_t)read(fs, buffer, boot->bpbBytesPerSec) !=
92 boot->bpbBytesPerSec) {
93 perr("Unable to read FAT");
94 goto err;
95 }
96
97 /*
98 * If we don't understand the FAT, then the file system must be
99 * assumed to be unclean.
100 */
101 if (buffer[0] != boot->bpbMedia || buffer[1] != 0xff)
102 goto err;
103 if (boot->ClustMask == CLUST16_MASK) {
104 if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f)
105 goto err;
106 } else {
107 if (buffer[2] != 0xff || (buffer[3] & 0x0f) != 0x0f
108 || (buffer[4] & 0xf8) != 0xf8 || buffer[5] != 0xff
109 || buffer[6] != 0xff || (buffer[7] & 0x03) != 0x03)
110 goto err;
111 }
112
113 /*
114 * Now check the actual clean flag (and the no-error flag).
115 */
116 if (boot->ClustMask == CLUST16_MASK) {
117 if ((buffer[3] & 0xc0) == 0xc0)
118 ret = 1;
119 } else {
120 if ((buffer[7] & 0x0c) == 0x0c)
121 ret = 1;
122 }
123
124 err:
125 free(buffer);
126 return ret;
127 }
128
129 /*
130 * Check a cluster number for valid value
131 */
132 static int
checkclnum(struct bootblock * boot,u_int fat,cl_t cl,cl_t * next)133 checkclnum(struct bootblock *boot, u_int fat, cl_t cl, cl_t *next)
134 {
135 if (*next >= (CLUST_RSRVD&boot->ClustMask))
136 *next |= ~boot->ClustMask;
137 if (*next == CLUST_FREE) {
138 boot->NumFree++;
139 return FSOK;
140 }
141 if (*next == CLUST_BAD) {
142 boot->NumBad++;
143 return FSOK;
144 }
145 if (*next < CLUST_FIRST
146 || (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
147 pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n",
148 cl, fat,
149 *next < CLUST_RSRVD ? "out of range" : "reserved",
150 *next&boot->ClustMask);
151 if (ask(0, "Truncate")) {
152 *next = CLUST_EOF;
153 return FSFATMOD;
154 }
155 return FSERROR;
156 }
157 return FSOK;
158 }
159
160 /*
161 * Read a FAT from disk. Returns 1 if successful, 0 otherwise.
162 */
163 static int
_readfat(int fs,struct bootblock * boot,u_int no,u_char ** buffer)164 _readfat(int fs, struct bootblock *boot, u_int no, u_char **buffer)
165 {
166 off_t off;
167 size_t len;
168
169 *buffer = malloc(len = boot->FATsecs * boot->bpbBytesPerSec);
170 if (*buffer == NULL) {
171 perr("No space for FAT sectors (%zu)", len);
172 return 0;
173 }
174
175 off = boot->bpbResSectors + no * boot->FATsecs;
176 off *= boot->bpbBytesPerSec;
177
178 if (lseek(fs, off, SEEK_SET) != off) {
179 perr("Unable to read FAT");
180 goto err;
181 }
182
183 if ((size_t)read(fs, *buffer, boot->FATsecs * boot->bpbBytesPerSec)
184 != boot->FATsecs * boot->bpbBytesPerSec) {
185 perr("Unable to read FAT");
186 goto err;
187 }
188
189 return 1;
190
191 err:
192 free(*buffer);
193 return 0;
194 }
195
196 /*
197 * Read a FAT and decode it into internal format
198 */
199 int
readfat(int fs,struct bootblock * boot,u_int no,struct fatEntry ** fp)200 readfat(int fs, struct bootblock *boot, u_int no, struct fatEntry **fp)
201 {
202 struct fatEntry *fat;
203 u_char *buffer, *p;
204 cl_t cl;
205 int ret = FSOK;
206 size_t len;
207
208 boot->NumFree = boot->NumBad = 0;
209
210 if (!_readfat(fs, boot, no, &buffer))
211 return FSFATAL;
212
213 fat = malloc(len = boot->NumClusters * sizeof(struct fatEntry));
214 if (fat == NULL) {
215 perr("No space for FAT clusters (%zu)", len);
216 free(buffer);
217 return FSFATAL;
218 }
219 (void)memset(fat, 0, len);
220
221 if (buffer[0] != boot->bpbMedia
222 || buffer[1] != 0xff || buffer[2] != 0xff
223 || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
224 || (boot->ClustMask == CLUST32_MASK
225 && ((buffer[3]&0x0f) != 0x0f
226 || buffer[4] != 0xff || buffer[5] != 0xff
227 || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
228
229 /* Windows 95 OSR2 (and possibly any later) changes
230 * the FAT signature to 0xXXffff7f for FAT16 and to
231 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
232 * file system is dirty if it doesn't reboot cleanly.
233 * Check this special condition before errorring out.
234 */
235 if (buffer[0] == boot->bpbMedia && buffer[1] == 0xff
236 && buffer[2] == 0xff
237 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
238 || (boot->ClustMask == CLUST32_MASK
239 && buffer[3] == 0x0f && buffer[4] == 0xff
240 && buffer[5] == 0xff && buffer[6] == 0xff
241 && buffer[7] == 0x07)))
242 ret |= FSDIRTY;
243 else {
244 /* just some odd byte sequence in FAT */
245
246 switch (boot->ClustMask) {
247 case CLUST32_MASK:
248 pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
249 "FAT starts with odd byte sequence",
250 buffer[0], buffer[1], buffer[2], buffer[3],
251 buffer[4], buffer[5], buffer[6], buffer[7]);
252 break;
253 case CLUST16_MASK:
254 pwarn("%s (%02x%02x%02x%02x)\n",
255 "FAT starts with odd byte sequence",
256 buffer[0], buffer[1], buffer[2], buffer[3]);
257 break;
258 default:
259 pwarn("%s (%02x%02x%02x)\n",
260 "FAT starts with odd byte sequence",
261 buffer[0], buffer[1], buffer[2]);
262 break;
263 }
264
265
266 if (ask(1, "Correct"))
267 ret |= FSFIXFAT;
268 }
269 }
270 switch (boot->ClustMask) {
271 case CLUST32_MASK:
272 p = buffer + 8;
273 break;
274 case CLUST16_MASK:
275 p = buffer + 4;
276 break;
277 default:
278 p = buffer + 3;
279 break;
280 }
281 for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
282 switch (boot->ClustMask) {
283 case CLUST32_MASK:
284 fat[cl].next = p[0] + (p[1] << 8)
285 + (p[2] << 16) + (p[3] << 24);
286 fat[cl].next &= boot->ClustMask;
287 ret |= checkclnum(boot, no, cl, &fat[cl].next);
288 cl++;
289 p += 4;
290 break;
291 case CLUST16_MASK:
292 fat[cl].next = p[0] + (p[1] << 8);
293 ret |= checkclnum(boot, no, cl, &fat[cl].next);
294 cl++;
295 p += 2;
296 break;
297 default:
298 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
299 ret |= checkclnum(boot, no, cl, &fat[cl].next);
300 cl++;
301 if (cl >= boot->NumClusters)
302 break;
303 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
304 ret |= checkclnum(boot, no, cl, &fat[cl].next);
305 cl++;
306 p += 3;
307 break;
308 }
309 }
310
311 free(buffer);
312 if (ret & FSFATAL) {
313 free(fat);
314 *fp = NULL;
315 } else
316 *fp = fat;
317 return ret;
318 }
319
320 /*
321 * Get type of reserved cluster
322 */
323 const char *
rsrvdcltype(cl_t cl)324 rsrvdcltype(cl_t cl)
325 {
326 if (cl == CLUST_FREE)
327 return "free";
328 if (cl < CLUST_BAD)
329 return "reserved";
330 if (cl > CLUST_BAD)
331 return "as EOF";
332 return "bad";
333 }
334
335 static int
clustdiffer(cl_t cl,cl_t * cp1,cl_t * cp2,u_int fatnum)336 clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, u_int fatnum)
337 {
338 if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) {
339 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
340 if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD
341 && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD)
342 || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
343 pwarn("Cluster %u is marked %s with different indicators\n",
344 cl, rsrvdcltype(*cp1));
345 if (ask(1, "Fix")) {
346 *cp2 = *cp1;
347 return FSFATMOD;
348 }
349 return FSFATAL;
350 }
351 pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %u\n",
352 cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
353 if (ask(0, "Use FAT 0's entry")) {
354 *cp2 = *cp1;
355 return FSFATMOD;
356 }
357 if (ask(0, "Use FAT %u's entry", fatnum)) {
358 *cp1 = *cp2;
359 return FSFATMOD;
360 }
361 return FSFATAL;
362 }
363 pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n",
364 cl, rsrvdcltype(*cp1), *cp2, fatnum);
365 if (ask(0, "Use continuation from FAT %u", fatnum)) {
366 *cp1 = *cp2;
367 return FSFATMOD;
368 }
369 if (ask(0, "Use mark from FAT 0")) {
370 *cp2 = *cp1;
371 return FSFATMOD;
372 }
373 return FSFATAL;
374 }
375 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
376 pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %u\n",
377 cl, *cp1, rsrvdcltype(*cp2), fatnum);
378 if (ask(0, "Use continuation from FAT 0")) {
379 *cp2 = *cp1;
380 return FSFATMOD;
381 }
382 if (ask(0, "Use mark from FAT %d", fatnum)) {
383 *cp1 = *cp2;
384 return FSFATMOD;
385 }
386 return FSERROR;
387 }
388 pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %u\n",
389 cl, *cp1, *cp2, fatnum);
390 if (ask(0, "Use continuation from FAT 0")) {
391 *cp2 = *cp1;
392 return FSFATMOD;
393 }
394 if (ask(0, "Use continuation from FAT %u", fatnum)) {
395 *cp1 = *cp2;
396 return FSFATMOD;
397 }
398 return FSERROR;
399 }
400
401 /*
402 * Compare two FAT copies in memory. Resolve any conflicts and merge them
403 * into the first one.
404 */
405 int
comparefat(struct bootblock * boot,struct fatEntry * first,struct fatEntry * second,u_int fatnum)406 comparefat(struct bootblock *boot, struct fatEntry *first,
407 struct fatEntry *second, u_int fatnum)
408 {
409 cl_t cl;
410 int ret = FSOK;
411
412 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
413 if (first[cl].next != second[cl].next)
414 ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
415 return ret;
416 }
417
418 void
clearchain(struct bootblock * boot,struct fatEntry * fat,cl_t head)419 clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
420 {
421 cl_t p, q;
422
423 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
424 if (fat[p].head != head)
425 break;
426 q = fat[p].next;
427 fat[p].next = fat[p].head = CLUST_FREE;
428 fat[p].length = 0;
429 }
430 }
431
432 int
tryclear(struct bootblock * boot,struct fatEntry * fat,cl_t head,cl_t * truncp)433 tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *truncp)
434 {
435 if (ask(0, "Clear chain starting at %u", head)) {
436 clearchain(boot, fat, head);
437 return FSFATMOD;
438 } else if (ask(0, "Truncate")) {
439 uint32_t len;
440 cl_t p;
441
442 for (p = head, len = 0;
443 p >= CLUST_FIRST && p < boot->NumClusters;
444 p = fat[p].next, len++)
445 continue;
446 *truncp = CLUST_EOF;
447 fat[head].length = len;
448 return FSFATMOD;
449 } else
450 return FSERROR;
451 }
452
453 /*
454 * Check a complete FAT in-memory for crosslinks
455 */
456 int
checkfat(struct bootblock * boot,struct fatEntry * fat)457 checkfat(struct bootblock *boot, struct fatEntry *fat)
458 {
459 cl_t head, p, h, n;
460 u_int len;
461 int ret = 0;
462 int conf;
463
464 /*
465 * pass 1: figure out the cluster chains.
466 */
467 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
468 /* find next untravelled chain */
469 if (fat[head].head != 0 /* cluster already belongs to some chain */
470 || fat[head].next == CLUST_FREE
471 || fat[head].next == CLUST_BAD)
472 continue; /* skip it. */
473
474 /* follow the chain and mark all clusters on the way */
475 for (len = 0, p = head;
476 p >= CLUST_FIRST && p < boot->NumClusters &&
477 fat[p].head != head;
478 p = fat[p].next) {
479 fat[p].head = head;
480 len++;
481 }
482
483 /* the head record gets the length */
484 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
485 }
486
487 /*
488 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
489 * we didn't know the real start of the chain then - would have treated partial
490 * chains as interlinked with their main chain)
491 */
492 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
493 /* find next untravelled chain */
494 if (fat[head].head != head)
495 continue;
496
497 /* follow the chain to its end (hopefully) */
498 for (len = fat[head].length, p = head;
499 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
500 p = n)
501 if (fat[n].head != head || len-- < 2)
502 break;
503 if (n >= CLUST_EOFS)
504 continue;
505
506 if (n == CLUST_FREE || n >= CLUST_RSRVD) {
507 pwarn("Cluster chain starting at %u ends with cluster marked %s\n",
508 head, rsrvdcltype(n));
509 clear:
510 ret |= tryclear(boot, fat, head, &fat[p].next);
511 continue;
512 }
513 if (n < CLUST_FIRST || n >= boot->NumClusters) {
514 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
515 head, n);
516 goto clear;
517 }
518 if (head == fat[n].head) {
519 pwarn("Cluster chain starting at %u loops at cluster %u\n",
520
521 head, p);
522 goto clear;
523 }
524 pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n",
525 head, fat[n].head, n);
526 conf = tryclear(boot, fat, head, &fat[p].next);
527 if (ask(0, "Clear chain starting at %u", h = fat[n].head)) {
528 if (conf == FSERROR) {
529 /*
530 * Transfer the common chain to the one not cleared above.
531 */
532 for (p = n;
533 p >= CLUST_FIRST && p < boot->NumClusters;
534 p = fat[p].next) {
535 if (h != fat[p].head) {
536 /*
537 * Have to reexamine this chain.
538 */
539 head--;
540 break;
541 }
542 fat[p].head = head;
543 }
544 }
545 clearchain(boot, fat, h);
546 conf |= FSFATMOD;
547 }
548 ret |= conf;
549 }
550
551 return ret;
552 }
553
554 /*
555 * Write out FATs encoding them from the internal format
556 */
557 int
writefat(int fs,struct bootblock * boot,struct fatEntry * fat,int correct_fat)558 writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
559 {
560 u_char *buffer, *p;
561 cl_t cl;
562 u_int i;
563 size_t fatsz;
564 off_t off;
565 int ret = FSOK;
566
567 buffer = malloc(fatsz = boot->FATsecs * boot->bpbBytesPerSec);
568 if (buffer == NULL) {
569 perr("No space for FAT sectors (%zu)", fatsz);
570 return FSFATAL;
571 }
572 memset(buffer, 0, fatsz);
573 boot->NumFree = 0;
574 p = buffer;
575 if (correct_fat) {
576 *p++ = (u_char)boot->bpbMedia;
577 *p++ = 0xff;
578 *p++ = 0xff;
579 switch (boot->ClustMask) {
580 case CLUST16_MASK:
581 *p++ = 0xff;
582 break;
583 case CLUST32_MASK:
584 *p++ = 0x0f;
585 *p++ = 0xff;
586 *p++ = 0xff;
587 *p++ = 0xff;
588 *p++ = 0x0f;
589 break;
590 }
591 } else {
592 /* use same FAT signature as the old FAT has */
593 int count;
594 u_char *old_fat;
595
596 switch (boot->ClustMask) {
597 case CLUST32_MASK:
598 count = 8;
599 break;
600 case CLUST16_MASK:
601 count = 4;
602 break;
603 default:
604 count = 3;
605 break;
606 }
607
608 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
609 &old_fat)) {
610 free(buffer);
611 return FSFATAL;
612 }
613
614 memcpy(p, old_fat, count);
615 free(old_fat);
616 p += count;
617 }
618
619 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
620 switch (boot->ClustMask) {
621 case CLUST32_MASK:
622 if (fat[cl].next == CLUST_FREE)
623 boot->NumFree++;
624 *p++ = (u_char)fat[cl].next;
625 *p++ = (u_char)(fat[cl].next >> 8);
626 *p++ = (u_char)(fat[cl].next >> 16);
627 *p &= 0xf0;
628 *p++ |= (fat[cl].next >> 24)&0x0f;
629 break;
630 case CLUST16_MASK:
631 if (fat[cl].next == CLUST_FREE)
632 boot->NumFree++;
633 *p++ = (u_char)fat[cl].next;
634 *p++ = (u_char)(fat[cl].next >> 8);
635 break;
636 default:
637 if (fat[cl].next == CLUST_FREE)
638 boot->NumFree++;
639 *p++ = (u_char)fat[cl].next;
640 *p = (u_char)((fat[cl].next >> 8) & 0xf);
641 cl++;
642 if (cl >= boot->NumClusters)
643 break;
644 if (fat[cl].next == CLUST_FREE)
645 boot->NumFree++;
646 *p++ |= (u_char)(fat[cl + 1].next << 4);
647 *p++ = (u_char)(fat[cl + 1].next >> 4);
648 break;
649 }
650 }
651 for (i = 0; i < boot->bpbFATs; i++) {
652 off = boot->bpbResSectors + i * boot->FATsecs;
653 off *= boot->bpbBytesPerSec;
654 if (lseek(fs, off, SEEK_SET) != off
655 || (size_t)write(fs, buffer, fatsz) != fatsz) {
656 perr("Unable to write FAT");
657 ret = FSFATAL; /* Return immediately? XXX */
658 }
659 }
660 free(buffer);
661 return ret;
662 }
663
664 /*
665 * Check a complete in-memory FAT for lost cluster chains
666 */
667 int
checklost(int dosfs,struct bootblock * boot,struct fatEntry * fat)668 checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
669 {
670 cl_t head;
671 int mod = FSOK;
672 int ret;
673
674 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
675 /* find next untravelled chain */
676 if (fat[head].head != head
677 || fat[head].next == CLUST_FREE
678 || (fat[head].next >= CLUST_RSRVD
679 && fat[head].next < CLUST_EOFS)
680 || (fat[head].flags & FAT_USED))
681 continue;
682
683 pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n",
684 head, fat[head].length);
685 mod |= ret = reconnect(dosfs, boot, fat, head);
686 if (mod & FSFATAL)
687 break;
688 if (ret == FSERROR && ask(0, "Clear")) {
689 clearchain(boot, fat, head);
690 mod |= FSFATMOD;
691 }
692 }
693 finishlf();
694
695 if (boot->bpbFSInfo) {
696 ret = 0;
697 if (boot->FSFree != 0xffffffffU &&
698 boot->FSFree != boot->NumFree) {
699 pwarn("Free space in FSInfo block (%u) not correct (%u)\n",
700 boot->FSFree, boot->NumFree);
701 if (ask(1, "Fix")) {
702 boot->FSFree = boot->NumFree;
703 ret = 1;
704 }
705 }
706 if (ret)
707 mod |= writefsinfo(dosfs, boot);
708 }
709
710 return mod;
711 }
712