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