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 * 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.
20 *
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.
31 */
32
33
34#include <sys/cdefs.h>
35#ifndef lint
36__RCSID("$NetBSD: fat.c,v 1.12 2000/10/10 20:24:52 is Exp $");
37static const char rcsid[] =
38 "$FreeBSD: head/sbin/fsck_msdosfs/fat.c 125471 2004-02-05 06:55:12Z bde $";
39#endif /* not lint */
40
41#include <stdlib.h>
42#include <string.h>
43#include <ctype.h>
44#include <stdio.h>
45#include <unistd.h>
46
47#include "ext.h"
48#include "fsutil.h"
49
50static int checkclnum(struct bootblock *, int, cl_t, cl_t *);
51static int clustdiffer(cl_t, cl_t *, cl_t *, int);
52static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *);
53static int _readfat(int, struct bootblock *, int, u_char **);
54
55/*-
56 * The first 2 FAT entries contain pseudo-cluster numbers with the following
57 * layout:
58 *
59 * 31...... ........ ........ .......0
60 * rrrr1111 11111111 11111111 mmmmmmmm FAT32 entry 0
61 * rrrrsh11 11111111 11111111 11111xxx FAT32 entry 1
62 *
63 * 11111111 mmmmmmmm FAT16 entry 0
64 * sh111111 11111xxx FAT16 entry 1
65 *
66 * r = reserved
67 * m = BPB media ID byte
68 * s = clean flag (1 = dismounted; 0 = still mounted)
69 * h = hard error flag (1 = ok; 0 = I/O error)
70 * x = any value ok
71 */
72
73int
74checkdirty(int fs, struct bootblock *boot)
75{
76 off_t off;
77 u_char *buffer;
78 int ret = 0;
79
80 if (boot->ClustMask == CLUST12_MASK)
81 return 0;
82
83 off = boot->ResSectors;
84 off *= boot->BytesPerSec;
85
86 buffer = malloc(boot->BytesPerSec);
87 if (buffer == NULL) {
88 perror("No space for FAT");
89 return 1;
90 }
91
92 if (lseek(fs, off, SEEK_SET) != off) {
93 perror("Unable to read FAT");
94 goto err;
95 }
96
97 if (read(fs, buffer, boot->BytesPerSec) != boot->BytesPerSec) {
98 perror("Unable to read FAT");
99 goto err;
100 }
101
102 if (buffer[0] == boot->Media && buffer[1] == 0xff && buffer[2] == 0xff
103 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
104 || (boot->ClustMask == CLUST32_MASK && buffer[3] == 0x0f
105 && buffer[4] == 0xff && buffer[5] == 0xff
106 && buffer[6] == 0xff && buffer[7] == 0x07)))
107 ret = 0;
108 else
109 ret = 1;
110
111err:
112 free(buffer);
113 return ret;
114}
115
116/*
117 * Check a cluster number for valid value
118 */
119static int
120checkclnum(struct bootblock *boot, int fat, cl_t cl, cl_t *next)
121{
122 if (*next >= (CLUST_RSRVD&boot->ClustMask))
123 *next |= ~boot->ClustMask;
124 if (*next == CLUST_FREE) {
125 boot->NumFree++;
126 return FSOK;
127 }
128 if (*next == CLUST_BAD) {
129 boot->NumBad++;
130 return FSOK;
131 }
132 if (*next < CLUST_FIRST
133 || (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
134 pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n",
135 cl, fat,
136 *next < CLUST_RSRVD ? "out of range" : "reserved",
137 *next&boot->ClustMask);
138 if (ask(0, "Truncate")) {
139 *next = CLUST_EOF;
140 return FSFATMOD;
141 }
142 return FSERROR;
143 }
144 return FSOK;
145}
146
147/*
148 * Read a FAT from disk. Returns 1 if successful, 0 otherwise.
149 */
150static int
151_readfat(int fs, struct bootblock *boot, int no, u_char **buffer)
152{
153 off_t off;
154
155 *buffer = malloc(boot->FATsecs * boot->BytesPerSec);
156 if (*buffer == NULL) {
157 perror("No space for FAT");
158 return 0;
159 }
160
161 off = boot->ResSectors + no * boot->FATsecs;
162 off *= boot->BytesPerSec;
163
164 if (lseek(fs, off, SEEK_SET) != off) {
165 perror("Unable to read FAT");
166 goto err;
167 }
168
169 if (read(fs, *buffer, boot->FATsecs * boot->BytesPerSec)
170 != boot->FATsecs * boot->BytesPerSec) {
171 perror("Unable to read FAT");
172 goto err;
173 }
174
175 return 1;
176
177 err:
178 free(*buffer);
179 return 0;
180}
181
182/*
183 * Read a FAT and decode it into internal format
184 */
185int
186readfat(int fs, struct bootblock *boot, int no, struct fatEntry **fp)
187{
188 struct fatEntry *fat;
189 u_char *buffer, *p;
190 cl_t cl;
191 int ret = FSOK;
192
193 boot->NumFree = boot->NumBad = 0;
194
195 if (!_readfat(fs, boot, no, &buffer))
196 return FSFATAL;
197
198 fat = calloc(boot->NumClusters, sizeof(struct fatEntry));
199 if (fat == NULL) {
200 perror("No space for FAT");
201 free(buffer);
202 return FSFATAL;
203 }
204
205 if (buffer[0] != boot->Media
206 || buffer[1] != 0xff || buffer[2] != 0xff
207 || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
208 || (boot->ClustMask == CLUST32_MASK
209 && ((buffer[3]&0x0f) != 0x0f
210 || buffer[4] != 0xff || buffer[5] != 0xff
211 || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
212
213 /* Windows 95 OSR2 (and possibly any later) changes
214 * the FAT signature to 0xXXffff7f for FAT16 and to
215 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
216 * file system is dirty if it doesn't reboot cleanly.
217 * Check this special condition before errorring out.
218 */
219 if (buffer[0] == boot->Media && buffer[1] == 0xff
220 && buffer[2] == 0xff
221 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
222 || (boot->ClustMask == CLUST32_MASK
223 && buffer[3] == 0x0f && buffer[4] == 0xff
224 && buffer[5] == 0xff && buffer[6] == 0xff
225 && buffer[7] == 0x07)))
226 ret |= FSDIRTY;
227 else {
228 /* just some odd byte sequence in FAT */
229
230 switch (boot->ClustMask) {
231 case CLUST32_MASK:
232 pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
233 "FAT starts with odd byte sequence",
234 buffer[0], buffer[1], buffer[2], buffer[3],
235 buffer[4], buffer[5], buffer[6], buffer[7]);
236 break;
237 case CLUST16_MASK:
238 pwarn("%s (%02x%02x%02x%02x)\n",
239 "FAT starts with odd byte sequence",
240 buffer[0], buffer[1], buffer[2], buffer[3]);
241 break;
242 default:
243 pwarn("%s (%02x%02x%02x)\n",
244 "FAT starts with odd byte sequence",
245 buffer[0], buffer[1], buffer[2]);
246 break;
247 }
248
249
250 if (ask(1, "Correct"))
251 ret |= FSFIXFAT;
252 }
253 }
254 switch (boot->ClustMask) {
255 case CLUST32_MASK:
256 p = buffer + 8;
257 break;
258 case CLUST16_MASK:
259 p = buffer + 4;
260 break;
261 default:
262 p = buffer + 3;
263 break;
264 }
265 for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
266 switch (boot->ClustMask) {
267 case CLUST32_MASK:
268 fat[cl].next = p[0] + (p[1] << 8)
269 + (p[2] << 16) + (p[3] << 24);
270 fat[cl].next &= boot->ClustMask;
271 ret |= checkclnum(boot, no, cl, &fat[cl].next);
272 cl++;
273 p += 4;
274 break;
275 case CLUST16_MASK:
276 fat[cl].next = p[0] + (p[1] << 8);
277 ret |= checkclnum(boot, no, cl, &fat[cl].next);
278 cl++;
279 p += 2;
280 break;
281 default:
282 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
283 ret |= checkclnum(boot, no, cl, &fat[cl].next);
284 cl++;
285 if (cl >= boot->NumClusters)
286 break;
287 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
288 ret |= checkclnum(boot, no, cl, &fat[cl].next);
289 cl++;
290 p += 3;
291 break;
292 }
293 }
294
295 free(buffer);
296 *fp = fat;
297 return ret;
298}
299
300/*
301 * Get type of reserved cluster
302 */
303char *
304rsrvdcltype(cl_t cl)
305{
306 if (cl == CLUST_FREE)
307 return "free";
308 if (cl < CLUST_BAD)
309 return "reserved";
310 if (cl > CLUST_BAD)
311 return "as EOF";
312 return "bad";
313}
314
315static int
316clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, int fatnum)
317{
318 if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) {
319 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
320 if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD
321 && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD)
322 || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
323 pwarn("Cluster %u is marked %s with different indicators, ",
324 cl, rsrvdcltype(*cp1));
325 if (ask(1, "fix")) {
326 *cp2 = *cp1;
327 return FSFATMOD;
328 }
329 return FSFATAL;
330 }
331 pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %d\n",
332 cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
333 if (ask(0, "use FAT 0's entry")) {
334 *cp2 = *cp1;
335 return FSFATMOD;
336 }
337 if (ask(0, "use FAT %d's entry", fatnum)) {
338 *cp1 = *cp2;
339 return FSFATMOD;
340 }
341 return FSFATAL;
342 }
343 pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n",
344 cl, rsrvdcltype(*cp1), *cp2, fatnum);
345 if (ask(0, "Use continuation from FAT %d", fatnum)) {
346 *cp1 = *cp2;
347 return FSFATMOD;
348 }
349 if (ask(0, "Use mark from FAT 0")) {
350 *cp2 = *cp1;
351 return FSFATMOD;
352 }
353 return FSFATAL;
354 }
355 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
356 pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %d\n",
357 cl, *cp1, rsrvdcltype(*cp2), fatnum);
358 if (ask(0, "Use continuation from FAT 0")) {
359 *cp2 = *cp1;
360 return FSFATMOD;
361 }
362 if (ask(0, "Use mark from FAT %d", fatnum)) {
363 *cp1 = *cp2;
364 return FSFATMOD;
365 }
366 return FSERROR;
367 }
368 pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %d\n",
369 cl, *cp1, *cp2, fatnum);
370 if (ask(0, "Use continuation from FAT 0")) {
371 *cp2 = *cp1;
372 return FSFATMOD;
373 }
374 if (ask(0, "Use continuation from FAT %d", fatnum)) {
375 *cp1 = *cp2;
376 return FSFATMOD;
377 }
378 return FSERROR;
379}
380
381/*
382 * Compare two FAT copies in memory. Resolve any conflicts and merge them
383 * into the first one.
384 */
385int
386comparefat(struct bootblock *boot, struct fatEntry *first,
387 struct fatEntry *second, int fatnum)
388{
389 cl_t cl;
390 int ret = FSOK;
391
392 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
393 if (first[cl].next != second[cl].next)
394 ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
395 return ret;
396}
397
398void
399clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
400{
401 cl_t p, q;
402
403 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
404 if (fat[p].head != head)
405 break;
406 q = fat[p].next;
407 fat[p].next = fat[p].head = CLUST_FREE;
408 fat[p].length = 0;
409 }
410}
411
412int
413tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *trunc)
414{
415 if (ask(0, "Clear chain starting at %u", head)) {
416 clearchain(boot, fat, head);
417 return FSFATMOD;
418 } else if (ask(0, "Truncate")) {
419 *trunc = CLUST_EOF;
420 return FSFATMOD;
421 } else
422 return FSERROR;
423}
424
425/*
426 * Check a complete FAT in-memory for crosslinks
427 */
428int
429checkfat(struct bootblock *boot, struct fatEntry *fat)
430{
431 cl_t head, p, h, n;
432 u_int len;
433 int ret = 0;
434 int conf;
435
436 /*
437 * pass 1: figure out the cluster chains.
438 */
439 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
440 /* find next untravelled chain */
441 if (fat[head].head != 0 /* cluster already belongs to some chain */
442 || fat[head].next == CLUST_FREE
443 || fat[head].next == CLUST_BAD)
444 continue; /* skip it. */
445
446 /* follow the chain and mark all clusters on the way */
447 for (len = 0, p = head;
448 p >= CLUST_FIRST && p < boot->NumClusters;
449 p = fat[p].next) {
450 fat[p].head = head;
451 len++;
452 }
453
454 /* the head record gets the length */
455 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
456 }
457
458 /*
459 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
460 * we didn't know the real start of the chain then - would have treated partial
461 * chains as interlinked with their main chain)
462 */
463 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
464 /* find next untravelled chain */
465 if (fat[head].head != head)
466 continue;
467
468 /* follow the chain to its end (hopefully) */
469 for (p = head;
470 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
471 p = n)
472 if (fat[n].head != head)
473 break;
474 if (n >= CLUST_EOFS)
475 continue;
476
477 if (n == CLUST_FREE || n >= CLUST_RSRVD) {
478 pwarn("Cluster chain starting at %u ends with cluster marked %s\n",
479 head, rsrvdcltype(n));
480 ret |= tryclear(boot, fat, head, &fat[p].next);
481 continue;
482 }
483 if (n < CLUST_FIRST || n >= boot->NumClusters) {
484 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
485 head, n);
486 ret |= tryclear(boot, fat, head, &fat[p].next);
487 continue;
488 }
489 pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n",
490 head, fat[n].head, n);
491 conf = tryclear(boot, fat, head, &fat[p].next);
492 if (ask(0, "Clear chain starting at %u", h = fat[n].head)) {
493 if (conf == FSERROR) {
494 /*
495 * Transfer the common chain to the one not cleared above.
496 */
497 for (p = n;
498 p >= CLUST_FIRST && p < boot->NumClusters;
499 p = fat[p].next) {
500 if (h != fat[p].head) {
501 /*
502 * Have to reexamine this chain.
503 */
504 head--;
505 break;
506 }
507 fat[p].head = head;
508 }
509 }
510 clearchain(boot, fat, h);
511 conf |= FSFATMOD;
512 }
513 ret |= conf;
514 }
515
516 return ret;
517}
518
519/*
520 * Write out FATs encoding them from the internal format
521 */
522int
523writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
524{
525 u_char *buffer, *p;
526 cl_t cl;
527 int i;
528 u_int32_t fatsz;
529 off_t off;
530 int ret = FSOK;
531
532 buffer = malloc(fatsz = boot->FATsecs * boot->BytesPerSec);
533 if (buffer == NULL) {
534 perror("No space for FAT");
535 return FSFATAL;
536 }
537 memset(buffer, 0, fatsz);
538 boot->NumFree = 0;
539 p = buffer;
540 if (correct_fat) {
541 *p++ = (u_char)boot->Media;
542 *p++ = 0xff;
543 *p++ = 0xff;
544 switch (boot->ClustMask) {
545 case CLUST16_MASK:
546 *p++ = 0xff;
547 break;
548 case CLUST32_MASK:
549 *p++ = 0x0f;
550 *p++ = 0xff;
551 *p++ = 0xff;
552 *p++ = 0xff;
553 *p++ = 0x0f;
554 break;
555 }
556 } else {
557 /* use same FAT signature as the old FAT has */
558 int count;
559 u_char *old_fat;
560
561 switch (boot->ClustMask) {
562 case CLUST32_MASK:
563 count = 8;
564 break;
565 case CLUST16_MASK:
566 count = 4;
567 break;
568 default:
569 count = 3;
570 break;
571 }
572
573 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
574 &old_fat)) {
575 free(buffer);
576 return FSFATAL;
577 }
578
579 memcpy(p, old_fat, count);
580 free(old_fat);
581 p += count;
582 }
583
584 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
585 switch (boot->ClustMask) {
586 case CLUST32_MASK:
587 if (fat[cl].next == CLUST_FREE)
588 boot->NumFree++;
589 *p++ = (u_char)fat[cl].next;
590 *p++ = (u_char)(fat[cl].next >> 8);
591 *p++ = (u_char)(fat[cl].next >> 16);
592 *p &= 0xf0;
593 *p++ |= (fat[cl].next >> 24)&0x0f;
594 break;
595 case CLUST16_MASK:
596 if (fat[cl].next == CLUST_FREE)
597 boot->NumFree++;
598 *p++ = (u_char)fat[cl].next;
599 *p++ = (u_char)(fat[cl].next >> 8);
600 break;
601 default:
602 if (fat[cl].next == CLUST_FREE)
603 boot->NumFree++;
604 if (cl + 1 < boot->NumClusters
605 && fat[cl + 1].next == CLUST_FREE)
606 boot->NumFree++;
607 *p++ = (u_char)fat[cl].next;
608 *p++ = (u_char)((fat[cl].next >> 8) & 0xf)
609 |(u_char)(fat[cl+1].next << 4);
610 *p++ = (u_char)(fat[++cl].next >> 4);
611 break;
612 }
613 }
614 for (i = 0; i < boot->FATs; i++) {
615 off = boot->ResSectors + i * boot->FATsecs;
616 off *= boot->BytesPerSec;
617 if (lseek(fs, off, SEEK_SET) != off
618 || write(fs, buffer, fatsz) != fatsz) {
619 perror("Unable to write FAT");
620 ret = FSFATAL; /* Return immediately? XXX */
621 }
622 }
623 free(buffer);
624 return ret;
625}
626
627/*
628 * Check a complete in-memory FAT for lost cluster chains
629 */
630int
631checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
632{
633 cl_t head;
634 int mod = FSOK;
635 int ret;
636
637 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
638 /* find next untravelled chain */
639 if (fat[head].head != head
640 || fat[head].next == CLUST_FREE
641 || (fat[head].next >= CLUST_RSRVD
642 && fat[head].next < CLUST_EOFS)
643 || (fat[head].flags & FAT_USED))
644 continue;
645
646 pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n",
647 head, fat[head].length);
648 mod |= ret = reconnect(dosfs, boot, fat, head);
649 if (mod & FSFATAL)
650 break;
651 if (ret == FSERROR && ask(0, "Clear")) {
652 clearchain(boot, fat, head);
653 mod |= FSFATMOD;
654 }
655 }
656 finishlf();
657
658 if (boot->FSInfo) {
659 ret = 0;
660 if (boot->FSFree != boot->NumFree) {
661 pwarn("Free space in FSInfo block (%d) not correct (%d)\n",
662 boot->FSFree, boot->NumFree);
663 if (ask(1, "fix")) {
664 boot->FSFree = boot->NumFree;
665 ret = 1;
666 }
667 }
668 if (boot->NumFree && fat[boot->FSNext].next != CLUST_FREE) {
669 pwarn("Next free cluster in FSInfo block (%u) not free\n",
670 boot->FSNext);
671 if (ask(1, "fix"))
672 for (head = CLUST_FIRST; head < boot->NumClusters; head++)
673 if (fat[head].next == CLUST_FREE) {
674 boot->FSNext = head;
675 ret = 1;
676 break;
677 }
678 }
679 if (ret)
680 mod |= writefsinfo(dosfs, boot);
681 }
682
683 return mod;
684}
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 * 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.
20 *
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.
31 */
32
33
34#include <sys/cdefs.h>
35#ifndef lint
36__RCSID("$NetBSD: fat.c,v 1.12 2000/10/10 20:24:52 is Exp $");
37static const char rcsid[] =
38 "$FreeBSD: head/sbin/fsck_msdosfs/fat.c 125471 2004-02-05 06:55:12Z bde $";
39#endif /* not lint */
40
41#include <stdlib.h>
42#include <string.h>
43#include <ctype.h>
44#include <stdio.h>
45#include <unistd.h>
46
47#include "ext.h"
48#include "fsutil.h"
49
50static int checkclnum(struct bootblock *, int, cl_t, cl_t *);
51static int clustdiffer(cl_t, cl_t *, cl_t *, int);
52static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *);
53static int _readfat(int, struct bootblock *, int, u_char **);
54
55/*-
56 * The first 2 FAT entries contain pseudo-cluster numbers with the following
57 * layout:
58 *
59 * 31...... ........ ........ .......0
60 * rrrr1111 11111111 11111111 mmmmmmmm FAT32 entry 0
61 * rrrrsh11 11111111 11111111 11111xxx FAT32 entry 1
62 *
63 * 11111111 mmmmmmmm FAT16 entry 0
64 * sh111111 11111xxx FAT16 entry 1
65 *
66 * r = reserved
67 * m = BPB media ID byte
68 * s = clean flag (1 = dismounted; 0 = still mounted)
69 * h = hard error flag (1 = ok; 0 = I/O error)
70 * x = any value ok
71 */
72
73int
74checkdirty(int fs, struct bootblock *boot)
75{
76 off_t off;
77 u_char *buffer;
78 int ret = 0;
79
80 if (boot->ClustMask == CLUST12_MASK)
81 return 0;
82
83 off = boot->ResSectors;
84 off *= boot->BytesPerSec;
85
86 buffer = malloc(boot->BytesPerSec);
87 if (buffer == NULL) {
88 perror("No space for FAT");
89 return 1;
90 }
91
92 if (lseek(fs, off, SEEK_SET) != off) {
93 perror("Unable to read FAT");
94 goto err;
95 }
96
97 if (read(fs, buffer, boot->BytesPerSec) != boot->BytesPerSec) {
98 perror("Unable to read FAT");
99 goto err;
100 }
101
102 if (buffer[0] == boot->Media && buffer[1] == 0xff && buffer[2] == 0xff
103 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
104 || (boot->ClustMask == CLUST32_MASK && buffer[3] == 0x0f
105 && buffer[4] == 0xff && buffer[5] == 0xff
106 && buffer[6] == 0xff && buffer[7] == 0x07)))
107 ret = 0;
108 else
109 ret = 1;
110
111err:
112 free(buffer);
113 return ret;
114}
115
116/*
117 * Check a cluster number for valid value
118 */
119static int
120checkclnum(struct bootblock *boot, int fat, cl_t cl, cl_t *next)
121{
122 if (*next >= (CLUST_RSRVD&boot->ClustMask))
123 *next |= ~boot->ClustMask;
124 if (*next == CLUST_FREE) {
125 boot->NumFree++;
126 return FSOK;
127 }
128 if (*next == CLUST_BAD) {
129 boot->NumBad++;
130 return FSOK;
131 }
132 if (*next < CLUST_FIRST
133 || (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
134 pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n",
135 cl, fat,
136 *next < CLUST_RSRVD ? "out of range" : "reserved",
137 *next&boot->ClustMask);
138 if (ask(0, "Truncate")) {
139 *next = CLUST_EOF;
140 return FSFATMOD;
141 }
142 return FSERROR;
143 }
144 return FSOK;
145}
146
147/*
148 * Read a FAT from disk. Returns 1 if successful, 0 otherwise.
149 */
150static int
151_readfat(int fs, struct bootblock *boot, int no, u_char **buffer)
152{
153 off_t off;
154
155 *buffer = malloc(boot->FATsecs * boot->BytesPerSec);
156 if (*buffer == NULL) {
157 perror("No space for FAT");
158 return 0;
159 }
160
161 off = boot->ResSectors + no * boot->FATsecs;
162 off *= boot->BytesPerSec;
163
164 if (lseek(fs, off, SEEK_SET) != off) {
165 perror("Unable to read FAT");
166 goto err;
167 }
168
169 if (read(fs, *buffer, boot->FATsecs * boot->BytesPerSec)
170 != boot->FATsecs * boot->BytesPerSec) {
171 perror("Unable to read FAT");
172 goto err;
173 }
174
175 return 1;
176
177 err:
178 free(*buffer);
179 return 0;
180}
181
182/*
183 * Read a FAT and decode it into internal format
184 */
185int
186readfat(int fs, struct bootblock *boot, int no, struct fatEntry **fp)
187{
188 struct fatEntry *fat;
189 u_char *buffer, *p;
190 cl_t cl;
191 int ret = FSOK;
192
193 boot->NumFree = boot->NumBad = 0;
194
195 if (!_readfat(fs, boot, no, &buffer))
196 return FSFATAL;
197
198 fat = calloc(boot->NumClusters, sizeof(struct fatEntry));
199 if (fat == NULL) {
200 perror("No space for FAT");
201 free(buffer);
202 return FSFATAL;
203 }
204
205 if (buffer[0] != boot->Media
206 || buffer[1] != 0xff || buffer[2] != 0xff
207 || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
208 || (boot->ClustMask == CLUST32_MASK
209 && ((buffer[3]&0x0f) != 0x0f
210 || buffer[4] != 0xff || buffer[5] != 0xff
211 || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
212
213 /* Windows 95 OSR2 (and possibly any later) changes
214 * the FAT signature to 0xXXffff7f for FAT16 and to
215 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
216 * file system is dirty if it doesn't reboot cleanly.
217 * Check this special condition before errorring out.
218 */
219 if (buffer[0] == boot->Media && buffer[1] == 0xff
220 && buffer[2] == 0xff
221 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
222 || (boot->ClustMask == CLUST32_MASK
223 && buffer[3] == 0x0f && buffer[4] == 0xff
224 && buffer[5] == 0xff && buffer[6] == 0xff
225 && buffer[7] == 0x07)))
226 ret |= FSDIRTY;
227 else {
228 /* just some odd byte sequence in FAT */
229
230 switch (boot->ClustMask) {
231 case CLUST32_MASK:
232 pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
233 "FAT starts with odd byte sequence",
234 buffer[0], buffer[1], buffer[2], buffer[3],
235 buffer[4], buffer[5], buffer[6], buffer[7]);
236 break;
237 case CLUST16_MASK:
238 pwarn("%s (%02x%02x%02x%02x)\n",
239 "FAT starts with odd byte sequence",
240 buffer[0], buffer[1], buffer[2], buffer[3]);
241 break;
242 default:
243 pwarn("%s (%02x%02x%02x)\n",
244 "FAT starts with odd byte sequence",
245 buffer[0], buffer[1], buffer[2]);
246 break;
247 }
248
249
250 if (ask(1, "Correct"))
251 ret |= FSFIXFAT;
252 }
253 }
254 switch (boot->ClustMask) {
255 case CLUST32_MASK:
256 p = buffer + 8;
257 break;
258 case CLUST16_MASK:
259 p = buffer + 4;
260 break;
261 default:
262 p = buffer + 3;
263 break;
264 }
265 for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
266 switch (boot->ClustMask) {
267 case CLUST32_MASK:
268 fat[cl].next = p[0] + (p[1] << 8)
269 + (p[2] << 16) + (p[3] << 24);
270 fat[cl].next &= boot->ClustMask;
271 ret |= checkclnum(boot, no, cl, &fat[cl].next);
272 cl++;
273 p += 4;
274 break;
275 case CLUST16_MASK:
276 fat[cl].next = p[0] + (p[1] << 8);
277 ret |= checkclnum(boot, no, cl, &fat[cl].next);
278 cl++;
279 p += 2;
280 break;
281 default:
282 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
283 ret |= checkclnum(boot, no, cl, &fat[cl].next);
284 cl++;
285 if (cl >= boot->NumClusters)
286 break;
287 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
288 ret |= checkclnum(boot, no, cl, &fat[cl].next);
289 cl++;
290 p += 3;
291 break;
292 }
293 }
294
295 free(buffer);
296 *fp = fat;
297 return ret;
298}
299
300/*
301 * Get type of reserved cluster
302 */
303char *
304rsrvdcltype(cl_t cl)
305{
306 if (cl == CLUST_FREE)
307 return "free";
308 if (cl < CLUST_BAD)
309 return "reserved";
310 if (cl > CLUST_BAD)
311 return "as EOF";
312 return "bad";
313}
314
315static int
316clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, int fatnum)
317{
318 if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) {
319 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
320 if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD
321 && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD)
322 || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
323 pwarn("Cluster %u is marked %s with different indicators, ",
324 cl, rsrvdcltype(*cp1));
325 if (ask(1, "fix")) {
326 *cp2 = *cp1;
327 return FSFATMOD;
328 }
329 return FSFATAL;
330 }
331 pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %d\n",
332 cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
333 if (ask(0, "use FAT 0's entry")) {
334 *cp2 = *cp1;
335 return FSFATMOD;
336 }
337 if (ask(0, "use FAT %d's entry", fatnum)) {
338 *cp1 = *cp2;
339 return FSFATMOD;
340 }
341 return FSFATAL;
342 }
343 pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n",
344 cl, rsrvdcltype(*cp1), *cp2, fatnum);
345 if (ask(0, "Use continuation from FAT %d", fatnum)) {
346 *cp1 = *cp2;
347 return FSFATMOD;
348 }
349 if (ask(0, "Use mark from FAT 0")) {
350 *cp2 = *cp1;
351 return FSFATMOD;
352 }
353 return FSFATAL;
354 }
355 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
356 pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %d\n",
357 cl, *cp1, rsrvdcltype(*cp2), fatnum);
358 if (ask(0, "Use continuation from FAT 0")) {
359 *cp2 = *cp1;
360 return FSFATMOD;
361 }
362 if (ask(0, "Use mark from FAT %d", fatnum)) {
363 *cp1 = *cp2;
364 return FSFATMOD;
365 }
366 return FSERROR;
367 }
368 pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %d\n",
369 cl, *cp1, *cp2, fatnum);
370 if (ask(0, "Use continuation from FAT 0")) {
371 *cp2 = *cp1;
372 return FSFATMOD;
373 }
374 if (ask(0, "Use continuation from FAT %d", fatnum)) {
375 *cp1 = *cp2;
376 return FSFATMOD;
377 }
378 return FSERROR;
379}
380
381/*
382 * Compare two FAT copies in memory. Resolve any conflicts and merge them
383 * into the first one.
384 */
385int
386comparefat(struct bootblock *boot, struct fatEntry *first,
387 struct fatEntry *second, int fatnum)
388{
389 cl_t cl;
390 int ret = FSOK;
391
392 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
393 if (first[cl].next != second[cl].next)
394 ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
395 return ret;
396}
397
398void
399clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
400{
401 cl_t p, q;
402
403 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
404 if (fat[p].head != head)
405 break;
406 q = fat[p].next;
407 fat[p].next = fat[p].head = CLUST_FREE;
408 fat[p].length = 0;
409 }
410}
411
412int
413tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *trunc)
414{
415 if (ask(0, "Clear chain starting at %u", head)) {
416 clearchain(boot, fat, head);
417 return FSFATMOD;
418 } else if (ask(0, "Truncate")) {
419 *trunc = CLUST_EOF;
420 return FSFATMOD;
421 } else
422 return FSERROR;
423}
424
425/*
426 * Check a complete FAT in-memory for crosslinks
427 */
428int
429checkfat(struct bootblock *boot, struct fatEntry *fat)
430{
431 cl_t head, p, h, n;
432 u_int len;
433 int ret = 0;
434 int conf;
435
436 /*
437 * pass 1: figure out the cluster chains.
438 */
439 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
440 /* find next untravelled chain */
441 if (fat[head].head != 0 /* cluster already belongs to some chain */
442 || fat[head].next == CLUST_FREE
443 || fat[head].next == CLUST_BAD)
444 continue; /* skip it. */
445
446 /* follow the chain and mark all clusters on the way */
447 for (len = 0, p = head;
448 p >= CLUST_FIRST && p < boot->NumClusters;
449 p = fat[p].next) {
450 fat[p].head = head;
451 len++;
452 }
453
454 /* the head record gets the length */
455 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
456 }
457
458 /*
459 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
460 * we didn't know the real start of the chain then - would have treated partial
461 * chains as interlinked with their main chain)
462 */
463 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
464 /* find next untravelled chain */
465 if (fat[head].head != head)
466 continue;
467
468 /* follow the chain to its end (hopefully) */
469 for (p = head;
470 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
471 p = n)
472 if (fat[n].head != head)
473 break;
474 if (n >= CLUST_EOFS)
475 continue;
476
477 if (n == CLUST_FREE || n >= CLUST_RSRVD) {
478 pwarn("Cluster chain starting at %u ends with cluster marked %s\n",
479 head, rsrvdcltype(n));
480 ret |= tryclear(boot, fat, head, &fat[p].next);
481 continue;
482 }
483 if (n < CLUST_FIRST || n >= boot->NumClusters) {
484 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
485 head, n);
486 ret |= tryclear(boot, fat, head, &fat[p].next);
487 continue;
488 }
489 pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n",
490 head, fat[n].head, n);
491 conf = tryclear(boot, fat, head, &fat[p].next);
492 if (ask(0, "Clear chain starting at %u", h = fat[n].head)) {
493 if (conf == FSERROR) {
494 /*
495 * Transfer the common chain to the one not cleared above.
496 */
497 for (p = n;
498 p >= CLUST_FIRST && p < boot->NumClusters;
499 p = fat[p].next) {
500 if (h != fat[p].head) {
501 /*
502 * Have to reexamine this chain.
503 */
504 head--;
505 break;
506 }
507 fat[p].head = head;
508 }
509 }
510 clearchain(boot, fat, h);
511 conf |= FSFATMOD;
512 }
513 ret |= conf;
514 }
515
516 return ret;
517}
518
519/*
520 * Write out FATs encoding them from the internal format
521 */
522int
523writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
524{
525 u_char *buffer, *p;
526 cl_t cl;
527 int i;
528 u_int32_t fatsz;
529 off_t off;
530 int ret = FSOK;
531
532 buffer = malloc(fatsz = boot->FATsecs * boot->BytesPerSec);
533 if (buffer == NULL) {
534 perror("No space for FAT");
535 return FSFATAL;
536 }
537 memset(buffer, 0, fatsz);
538 boot->NumFree = 0;
539 p = buffer;
540 if (correct_fat) {
541 *p++ = (u_char)boot->Media;
542 *p++ = 0xff;
543 *p++ = 0xff;
544 switch (boot->ClustMask) {
545 case CLUST16_MASK:
546 *p++ = 0xff;
547 break;
548 case CLUST32_MASK:
549 *p++ = 0x0f;
550 *p++ = 0xff;
551 *p++ = 0xff;
552 *p++ = 0xff;
553 *p++ = 0x0f;
554 break;
555 }
556 } else {
557 /* use same FAT signature as the old FAT has */
558 int count;
559 u_char *old_fat;
560
561 switch (boot->ClustMask) {
562 case CLUST32_MASK:
563 count = 8;
564 break;
565 case CLUST16_MASK:
566 count = 4;
567 break;
568 default:
569 count = 3;
570 break;
571 }
572
573 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
574 &old_fat)) {
575 free(buffer);
576 return FSFATAL;
577 }
578
579 memcpy(p, old_fat, count);
580 free(old_fat);
581 p += count;
582 }
583
584 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
585 switch (boot->ClustMask) {
586 case CLUST32_MASK:
587 if (fat[cl].next == CLUST_FREE)
588 boot->NumFree++;
589 *p++ = (u_char)fat[cl].next;
590 *p++ = (u_char)(fat[cl].next >> 8);
591 *p++ = (u_char)(fat[cl].next >> 16);
592 *p &= 0xf0;
593 *p++ |= (fat[cl].next >> 24)&0x0f;
594 break;
595 case CLUST16_MASK:
596 if (fat[cl].next == CLUST_FREE)
597 boot->NumFree++;
598 *p++ = (u_char)fat[cl].next;
599 *p++ = (u_char)(fat[cl].next >> 8);
600 break;
601 default:
602 if (fat[cl].next == CLUST_FREE)
603 boot->NumFree++;
604 if (cl + 1 < boot->NumClusters
605 && fat[cl + 1].next == CLUST_FREE)
606 boot->NumFree++;
607 *p++ = (u_char)fat[cl].next;
608 *p++ = (u_char)((fat[cl].next >> 8) & 0xf)
609 |(u_char)(fat[cl+1].next << 4);
610 *p++ = (u_char)(fat[++cl].next >> 4);
611 break;
612 }
613 }
614 for (i = 0; i < boot->FATs; i++) {
615 off = boot->ResSectors + i * boot->FATsecs;
616 off *= boot->BytesPerSec;
617 if (lseek(fs, off, SEEK_SET) != off
618 || write(fs, buffer, fatsz) != fatsz) {
619 perror("Unable to write FAT");
620 ret = FSFATAL; /* Return immediately? XXX */
621 }
622 }
623 free(buffer);
624 return ret;
625}
626
627/*
628 * Check a complete in-memory FAT for lost cluster chains
629 */
630int
631checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
632{
633 cl_t head;
634 int mod = FSOK;
635 int ret;
636
637 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
638 /* find next untravelled chain */
639 if (fat[head].head != head
640 || fat[head].next == CLUST_FREE
641 || (fat[head].next >= CLUST_RSRVD
642 && fat[head].next < CLUST_EOFS)
643 || (fat[head].flags & FAT_USED))
644 continue;
645
646 pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n",
647 head, fat[head].length);
648 mod |= ret = reconnect(dosfs, boot, fat, head);
649 if (mod & FSFATAL)
650 break;
651 if (ret == FSERROR && ask(0, "Clear")) {
652 clearchain(boot, fat, head);
653 mod |= FSFATMOD;
654 }
655 }
656 finishlf();
657
658 if (boot->FSInfo) {
659 ret = 0;
660 if (boot->FSFree != boot->NumFree) {
661 pwarn("Free space in FSInfo block (%d) not correct (%d)\n",
662 boot->FSFree, boot->NumFree);
663 if (ask(1, "fix")) {
664 boot->FSFree = boot->NumFree;
665 ret = 1;
666 }
667 }
668 if (boot->NumFree && fat[boot->FSNext].next != CLUST_FREE) {
669 pwarn("Next free cluster in FSInfo block (%u) not free\n",
670 boot->FSNext);
671 if (ask(1, "fix"))
672 for (head = CLUST_FIRST; head < boot->NumClusters; head++)
673 if (fat[head].next == CLUST_FREE) {
674 boot->FSNext = head;
675 ret = 1;
676 break;
677 }
678 }
679 if (ret)
680 mod |= writefsinfo(dosfs, boot);
681 }
682
683 return mod;
684}