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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 1.12 2000/10/10 20:24:52 is Exp $");
30static const char rcsid[] =
31 "$FreeBSD: head/sbin/fsck_msdosfs/fat.c 203874 2010-02-14 12:31:28Z kib $";
31 "$FreeBSD: head/sbin/fsck_msdosfs/fat.c 209364 2010-06-20 09:40:54Z brian $";
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
43static int checkclnum(struct bootblock *, u_int, cl_t, cl_t *);
44static int clustdiffer(cl_t, cl_t *, cl_t *, u_int);
45static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *);
46static 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
66int
67checkdirty(int fs, struct bootblock *boot)
68{
69 off_t off;
70 u_char *buffer;
71 int ret = 0;
72
73 if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK)
74 return 0;
75
76 off = boot->bpbResSectors;
77 off *= boot->bpbBytesPerSec;
78
79 buffer = malloc(boot->bpbBytesPerSec);
80 if (buffer == NULL) {
81 perror("No space for FAT");
82 return 1;
83 }
84
85 if (lseek(fs, off, SEEK_SET) != off) {
86 perror("Unable to read FAT");
87 goto err;
88 }
89
90 if (read(fs, buffer, boot->bpbBytesPerSec) != boot->bpbBytesPerSec) {
90 if ((size_t)read(fs, buffer, boot->bpbBytesPerSec) !=
91 boot->bpbBytesPerSec) {
92 perror("Unable to read FAT");
93 goto err;
94 }
95
96 /*
97 * If we don't understand the FAT, then the file system must be
98 * assumed to be unclean.
99 */
100 if (buffer[0] != boot->bpbMedia || buffer[1] != 0xff)
101 goto err;
102 if (boot->ClustMask == CLUST16_MASK) {
103 if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f)
104 goto err;
105 } else {
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)
109 goto err;
110 }
111
112 /*
113 * Now check the actual clean flag (and the no-error flag).
114 */
115 if (boot->ClustMask == CLUST16_MASK) {
116 if ((buffer[3] & 0xc0) == 0xc0)
117 ret = 1;
118 } else {
119 if ((buffer[7] & 0x0c) == 0x0c)
120 ret = 1;
121 }
122
123err:
124 free(buffer);
125 return ret;
126}
127
128/*
129 * Check a cluster number for valid value
130 */
131static int
132checkclnum(struct bootblock *boot, u_int fat, cl_t cl, cl_t *next)
133{
134 if (*next >= (CLUST_RSRVD&boot->ClustMask))
135 *next |= ~boot->ClustMask;
136 if (*next == CLUST_FREE) {
137 boot->NumFree++;
138 return FSOK;
139 }
140 if (*next == CLUST_BAD) {
141 boot->NumBad++;
142 return FSOK;
143 }
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",
147 cl, fat,
148 *next < CLUST_RSRVD ? "out of range" : "reserved",
149 *next&boot->ClustMask);
150 if (ask(0, "Truncate")) {
151 *next = CLUST_EOF;
152 return FSFATMOD;
153 }
154 return FSERROR;
155 }
156 return FSOK;
157}
158
159/*
160 * Read a FAT from disk. Returns 1 if successful, 0 otherwise.
161 */
162static int
163_readfat(int fs, struct bootblock *boot, u_int no, u_char **buffer)
164{
165 off_t off;
166
167 *buffer = malloc(boot->FATsecs * boot->bpbBytesPerSec);
168 if (*buffer == NULL) {
169 perror("No space for FAT");
170 return 0;
171 }
172
173 off = boot->bpbResSectors + no * boot->FATsecs;
174 off *= boot->bpbBytesPerSec;
175
176 if (lseek(fs, off, SEEK_SET) != off) {
177 perror("Unable to read FAT");
178 goto err;
179 }
180
181 if ((size_t)read(fs, *buffer, boot->FATsecs * boot->bpbBytesPerSec)
182 != boot->FATsecs * boot->bpbBytesPerSec) {
183 perror("Unable to read FAT");
184 goto err;
185 }
186
187 return 1;
188
189 err:
190 free(*buffer);
191 return 0;
192}
193
194/*
195 * Read a FAT and decode it into internal format
196 */
197int
198readfat(int fs, struct bootblock *boot, u_int no, struct fatEntry **fp)
199{
200 struct fatEntry *fat;
201 u_char *buffer, *p;
202 cl_t cl;
203 int ret = FSOK;
204 size_t len;
205
206 boot->NumFree = boot->NumBad = 0;
207
208 if (!_readfat(fs, boot, no, &buffer))
209 return FSFATAL;
210
211 fat = malloc(len = boot->NumClusters * sizeof(struct fatEntry));
212 if (fat == NULL) {
213 perror("No space for FAT");
214 free(buffer);
215 return FSFATAL;
216 }
217 (void)memset(fat, 0, len);
218
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))) {
226
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.
232 */
233 if (buffer[0] == boot->bpbMedia && buffer[1] == 0xff
234 && buffer[2] == 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)))
240 ret |= FSDIRTY;
241 else {
242 /* just some odd byte sequence in FAT */
243
244 switch (boot->ClustMask) {
245 case CLUST32_MASK:
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]);
250 break;
251 case CLUST16_MASK:
252 pwarn("%s (%02x%02x%02x%02x)\n",
253 "FAT starts with odd byte sequence",
254 buffer[0], buffer[1], buffer[2], buffer[3]);
255 break;
256 default:
257 pwarn("%s (%02x%02x%02x)\n",
258 "FAT starts with odd byte sequence",
259 buffer[0], buffer[1], buffer[2]);
260 break;
261 }
262
263
264 if (ask(1, "Correct"))
265 ret |= FSFIXFAT;
266 }
267 }
268 switch (boot->ClustMask) {
269 case CLUST32_MASK:
270 p = buffer + 8;
271 break;
272 case CLUST16_MASK:
273 p = buffer + 4;
274 break;
275 default:
276 p = buffer + 3;
277 break;
278 }
279 for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
280 switch (boot->ClustMask) {
281 case CLUST32_MASK:
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);
286 cl++;
287 p += 4;
288 break;
289 case CLUST16_MASK:
290 fat[cl].next = p[0] + (p[1] << 8);
291 ret |= checkclnum(boot, no, cl, &fat[cl].next);
292 cl++;
293 p += 2;
294 break;
295 default:
296 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
297 ret |= checkclnum(boot, no, cl, &fat[cl].next);
298 cl++;
299 if (cl >= boot->NumClusters)
300 break;
301 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
302 ret |= checkclnum(boot, no, cl, &fat[cl].next);
303 cl++;
304 p += 3;
305 break;
306 }
307 }
308
309 free(buffer);
310 if (ret & FSFATAL) {
311 free(fat);
312 *fp = NULL;
313 } else
314 *fp = fat;
315 return ret;
316}
317
318/*
319 * Get type of reserved cluster
320 */
321char *
322rsrvdcltype(cl_t cl)
323{
324 if (cl == CLUST_FREE)
325 return "free";
326 if (cl < CLUST_BAD)
327 return "reserved";
328 if (cl > CLUST_BAD)
329 return "as EOF";
330 return "bad";
331}
332
333static int
334clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, u_int fatnum)
335{
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));
343 if (ask(1, "Fix")) {
344 *cp2 = *cp1;
345 return FSFATMOD;
346 }
347 return FSFATAL;
348 }
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")) {
352 *cp2 = *cp1;
353 return FSFATMOD;
354 }
355 if (ask(0, "Use FAT %u's entry", fatnum)) {
356 *cp1 = *cp2;
357 return FSFATMOD;
358 }
359 return FSFATAL;
360 }
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)) {
364 *cp1 = *cp2;
365 return FSFATMOD;
366 }
367 if (ask(0, "Use mark from FAT 0")) {
368 *cp2 = *cp1;
369 return FSFATMOD;
370 }
371 return FSFATAL;
372 }
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")) {
377 *cp2 = *cp1;
378 return FSFATMOD;
379 }
380 if (ask(0, "Use mark from FAT %d", fatnum)) {
381 *cp1 = *cp2;
382 return FSFATMOD;
383 }
384 return FSERROR;
385 }
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")) {
389 *cp2 = *cp1;
390 return FSFATMOD;
391 }
392 if (ask(0, "Use continuation from FAT %u", fatnum)) {
393 *cp1 = *cp2;
394 return FSFATMOD;
395 }
396 return FSERROR;
397}
398
399/*
400 * Compare two FAT copies in memory. Resolve any conflicts and merge them
401 * into the first one.
402 */
403int
404comparefat(struct bootblock *boot, struct fatEntry *first,
405 struct fatEntry *second, u_int fatnum)
406{
407 cl_t cl;
408 int ret = FSOK;
409
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);
413 return ret;
414}
415
416void
417clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
418{
419 cl_t p, q;
420
421 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
422 if (fat[p].head != head)
423 break;
424 q = fat[p].next;
425 fat[p].next = fat[p].head = CLUST_FREE;
426 fat[p].length = 0;
427 }
428}
429
430int
431tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *trunc)
432{
433 if (ask(0, "Clear chain starting at %u", head)) {
434 clearchain(boot, fat, head);
435 return FSFATMOD;
436 } else if (ask(0, "Truncate")) {
437 *trunc = CLUST_EOF;
438 return FSFATMOD;
439 } else
440 return FSERROR;
441}
442
443/*
444 * Check a complete FAT in-memory for crosslinks
445 */
446int
447checkfat(struct bootblock *boot, struct fatEntry *fat)
448{
449 cl_t head, p, h, n;
450 u_int len;
451 int ret = 0;
452 int conf;
453
454 /*
455 * pass 1: figure out the cluster chains.
456 */
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. */
463
464 /* follow the chain and mark all clusters on the way */
465 for (len = 0, p = head;
466 p >= CLUST_FIRST && p < boot->NumClusters;
467 p = fat[p].next) {
468 fat[p].head = head;
469 len++;
470 }
471
472 /* the head record gets the length */
473 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
474 }
475
476 /*
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)
480 */
481 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
482 /* find next untravelled chain */
483 if (fat[head].head != head)
484 continue;
485
486 /* follow the chain to its end (hopefully) */
487 for (p = head;
488 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
489 p = n)
490 if (fat[n].head != head)
491 break;
492 if (n >= CLUST_EOFS)
493 continue;
494
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);
499 continue;
500 }
501 if (n < CLUST_FIRST || n >= boot->NumClusters) {
502 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
503 head, n);
504 ret |= tryclear(boot, fat, head, &fat[p].next);
505 continue;
506 }
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) {
512 /*
513 * Transfer the common chain to the one not cleared above.
514 */
515 for (p = n;
516 p >= CLUST_FIRST && p < boot->NumClusters;
517 p = fat[p].next) {
518 if (h != fat[p].head) {
519 /*
520 * Have to reexamine this chain.
521 */
522 head--;
523 break;
524 }
525 fat[p].head = head;
526 }
527 }
528 clearchain(boot, fat, h);
529 conf |= FSFATMOD;
530 }
531 ret |= conf;
532 }
533
534 return ret;
535}
536
537/*
538 * Write out FATs encoding them from the internal format
539 */
540int
541writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
542{
543 u_char *buffer, *p;
544 cl_t cl;
545 u_int i;
546 size_t fatsz;
547 off_t off;
548 int ret = FSOK;
549
550 buffer = malloc(fatsz = boot->FATsecs * boot->bpbBytesPerSec);
551 if (buffer == NULL) {
552 perror("No space for FAT");
553 return FSFATAL;
554 }
555 memset(buffer, 0, fatsz);
556 boot->NumFree = 0;
557 p = buffer;
558 if (correct_fat) {
559 *p++ = (u_char)boot->bpbMedia;
560 *p++ = 0xff;
561 *p++ = 0xff;
562 switch (boot->ClustMask) {
563 case CLUST16_MASK:
564 *p++ = 0xff;
565 break;
566 case CLUST32_MASK:
567 *p++ = 0x0f;
568 *p++ = 0xff;
569 *p++ = 0xff;
570 *p++ = 0xff;
571 *p++ = 0x0f;
572 break;
573 }
574 } else {
575 /* use same FAT signature as the old FAT has */
576 int count;
577 u_char *old_fat;
578
579 switch (boot->ClustMask) {
580 case CLUST32_MASK:
581 count = 8;
582 break;
583 case CLUST16_MASK:
584 count = 4;
585 break;
586 default:
587 count = 3;
588 break;
589 }
590
591 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
592 &old_fat)) {
593 free(buffer);
594 return FSFATAL;
595 }
596
597 memcpy(p, old_fat, count);
598 free(old_fat);
599 p += count;
600 }
601
602 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
603 switch (boot->ClustMask) {
604 case CLUST32_MASK:
605 if (fat[cl].next == CLUST_FREE)
606 boot->NumFree++;
607 *p++ = (u_char)fat[cl].next;
608 *p++ = (u_char)(fat[cl].next >> 8);
609 *p++ = (u_char)(fat[cl].next >> 16);
610 *p &= 0xf0;
611 *p++ |= (fat[cl].next >> 24)&0x0f;
612 break;
613 case CLUST16_MASK:
614 if (fat[cl].next == CLUST_FREE)
615 boot->NumFree++;
616 *p++ = (u_char)fat[cl].next;
617 *p++ = (u_char)(fat[cl].next >> 8);
618 break;
619 default:
620 if (fat[cl].next == CLUST_FREE)
621 boot->NumFree++;
622 if (cl + 1 < boot->NumClusters
623 && fat[cl + 1].next == CLUST_FREE)
624 boot->NumFree++;
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);
629 break;
630 }
631 }
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 */
639 }
640 }
641 free(buffer);
642 return ret;
643}
644
645/*
646 * Check a complete in-memory FAT for lost cluster chains
647 */
648int
649checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
650{
651 cl_t head;
652 int mod = FSOK;
653 int ret;
654
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))
662 continue;
663
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);
667 if (mod & FSFATAL)
668 break;
669 if (ret == FSERROR && ask(0, "Clear")) {
670 clearchain(boot, fat, head);
671 mod |= FSFATMOD;
672 }
673 }
674 finishlf();
675
676 if (boot->bpbFSInfo) {
677 ret = 0;
678 if (boot->FSFree != boot->NumFree) {
679 pwarn("Free space in FSInfo block (%d) not correct (%d)\n",
680 boot->FSFree, boot->NumFree);
681 if (ask(1, "Fix")) {
682 boot->FSFree = boot->NumFree;
683 ret = 1;
684 }
685 }
686 if (ret)
687 mod |= writefsinfo(dosfs, boot);
688 }
689
690 return mod;
691}