fat.c revision 123874
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 102231 2002-08-21 18:11:48Z trhodes $"; 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 * Check a cluster number for valid value 57 */ 58static int 59checkclnum(struct bootblock *boot, int fat, cl_t cl, cl_t *next) 60{ 61 if (*next >= (CLUST_RSRVD&boot->ClustMask)) 62 *next |= ~boot->ClustMask; 63 if (*next == CLUST_FREE) { 64 boot->NumFree++; 65 return FSOK; 66 } 67 if (*next == CLUST_BAD) { 68 boot->NumBad++; 69 return FSOK; 70 } 71 if (*next < CLUST_FIRST 72 || (*next >= boot->NumClusters && *next < CLUST_EOFS)) { 73 pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n", 74 cl, fat, 75 *next < CLUST_RSRVD ? "out of range" : "reserved", 76 *next&boot->ClustMask); 77 if (ask(0, "Truncate")) { 78 *next = CLUST_EOF; 79 return FSFATMOD; 80 } 81 return FSERROR; 82 } 83 return FSOK; 84} 85 86/* 87 * Read a FAT from disk. Returns 1 if successful, 0 otherwise. 88 */ 89static int 90_readfat(int fs, struct bootblock *boot, int no, u_char **buffer) 91{ 92 off_t off; 93 94 *buffer = malloc(boot->FATsecs * boot->BytesPerSec); 95 if (*buffer == NULL) { 96 perror("No space for FAT"); 97 return 0; 98 } 99 100 off = boot->ResSectors + no * boot->FATsecs; 101 off *= boot->BytesPerSec; 102 103 if (lseek(fs, off, SEEK_SET) != off) { 104 perror("Unable to read FAT"); 105 goto err; 106 } 107 108 if (read(fs, *buffer, boot->FATsecs * boot->BytesPerSec) 109 != boot->FATsecs * boot->BytesPerSec) { 110 perror("Unable to read FAT"); 111 goto err; 112 } 113 114 return 1; 115 116 err: 117 free(*buffer); 118 return 0; 119} 120 121/* 122 * Read a FAT and decode it into internal format 123 */ 124int 125readfat(int fs, struct bootblock *boot, int no, struct fatEntry **fp) 126{ 127 struct fatEntry *fat; 128 u_char *buffer, *p; 129 cl_t cl; 130 int ret = FSOK; 131 132 boot->NumFree = boot->NumBad = 0; 133 134 if (!_readfat(fs, boot, no, &buffer)) 135 return FSFATAL; 136 137 fat = calloc(boot->NumClusters, sizeof(struct fatEntry)); 138 if (fat == NULL) { 139 perror("No space for FAT"); 140 free(buffer); 141 return FSFATAL; 142 } 143 144 if (buffer[0] != boot->Media 145 || buffer[1] != 0xff || buffer[2] != 0xff 146 || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff) 147 || (boot->ClustMask == CLUST32_MASK 148 && ((buffer[3]&0x0f) != 0x0f 149 || buffer[4] != 0xff || buffer[5] != 0xff 150 || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) { 151 152 /* Windows 95 OSR2 (and possibly any later) changes 153 * the FAT signature to 0xXXffff7f for FAT16 and to 154 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the 155 * file system is dirty if it doesn't reboot cleanly. 156 * Check this special condition before errorring out. 157 */ 158 if (buffer[0] == boot->Media && buffer[1] == 0xff 159 && buffer[2] == 0xff 160 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f) 161 || (boot->ClustMask == CLUST32_MASK 162 && buffer[3] == 0x0f && buffer[4] == 0xff 163 && buffer[5] == 0xff && buffer[6] == 0xff 164 && buffer[7] == 0x07))) 165 ret |= FSDIRTY; 166 else { 167 /* just some odd byte sequence in FAT */ 168 169 switch (boot->ClustMask) { 170 case CLUST32_MASK: 171 pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n", 172 "FAT starts with odd byte sequence", 173 buffer[0], buffer[1], buffer[2], buffer[3], 174 buffer[4], buffer[5], buffer[6], buffer[7]); 175 break; 176 case CLUST16_MASK: 177 pwarn("%s (%02x%02x%02x%02x)\n", 178 "FAT starts with odd byte sequence", 179 buffer[0], buffer[1], buffer[2], buffer[3]); 180 break; 181 default: 182 pwarn("%s (%02x%02x%02x)\n", 183 "FAT starts with odd byte sequence", 184 buffer[0], buffer[1], buffer[2]); 185 break; 186 } 187 188 189 if (ask(1, "Correct")) 190 ret |= FSFIXFAT; 191 } 192 } 193 switch (boot->ClustMask) { 194 case CLUST32_MASK: 195 p = buffer + 8; 196 break; 197 case CLUST16_MASK: 198 p = buffer + 4; 199 break; 200 default: 201 p = buffer + 3; 202 break; 203 } 204 for (cl = CLUST_FIRST; cl < boot->NumClusters;) { 205 switch (boot->ClustMask) { 206 case CLUST32_MASK: 207 fat[cl].next = p[0] + (p[1] << 8) 208 + (p[2] << 16) + (p[3] << 24); 209 fat[cl].next &= boot->ClustMask; 210 ret |= checkclnum(boot, no, cl, &fat[cl].next); 211 cl++; 212 p += 4; 213 break; 214 case CLUST16_MASK: 215 fat[cl].next = p[0] + (p[1] << 8); 216 ret |= checkclnum(boot, no, cl, &fat[cl].next); 217 cl++; 218 p += 2; 219 break; 220 default: 221 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff; 222 ret |= checkclnum(boot, no, cl, &fat[cl].next); 223 cl++; 224 if (cl >= boot->NumClusters) 225 break; 226 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff; 227 ret |= checkclnum(boot, no, cl, &fat[cl].next); 228 cl++; 229 p += 3; 230 break; 231 } 232 } 233 234 free(buffer); 235 *fp = fat; 236 return ret; 237} 238 239/* 240 * Get type of reserved cluster 241 */ 242char * 243rsrvdcltype(cl_t cl) 244{ 245 if (cl == CLUST_FREE) 246 return "free"; 247 if (cl < CLUST_BAD) 248 return "reserved"; 249 if (cl > CLUST_BAD) 250 return "as EOF"; 251 return "bad"; 252} 253 254static int 255clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, int fatnum) 256{ 257 if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) { 258 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) { 259 if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD 260 && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD) 261 || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) { 262 pwarn("Cluster %u is marked %s with different indicators, ", 263 cl, rsrvdcltype(*cp1)); 264 if (ask(1, "fix")) { 265 *cp2 = *cp1; 266 return FSFATMOD; 267 } 268 return FSFATAL; 269 } 270 pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %d\n", 271 cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum); 272 if (ask(0, "use FAT 0's entry")) { 273 *cp2 = *cp1; 274 return FSFATMOD; 275 } 276 if (ask(0, "use FAT %d's entry", fatnum)) { 277 *cp1 = *cp2; 278 return FSFATMOD; 279 } 280 return FSFATAL; 281 } 282 pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n", 283 cl, rsrvdcltype(*cp1), *cp2, fatnum); 284 if (ask(0, "Use continuation from FAT %d", fatnum)) { 285 *cp1 = *cp2; 286 return FSFATMOD; 287 } 288 if (ask(0, "Use mark from FAT 0")) { 289 *cp2 = *cp1; 290 return FSFATMOD; 291 } 292 return FSFATAL; 293 } 294 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) { 295 pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %d\n", 296 cl, *cp1, rsrvdcltype(*cp2), fatnum); 297 if (ask(0, "Use continuation from FAT 0")) { 298 *cp2 = *cp1; 299 return FSFATMOD; 300 } 301 if (ask(0, "Use mark from FAT %d", fatnum)) { 302 *cp1 = *cp2; 303 return FSFATMOD; 304 } 305 return FSERROR; 306 } 307 pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %d\n", 308 cl, *cp1, *cp2, fatnum); 309 if (ask(0, "Use continuation from FAT 0")) { 310 *cp2 = *cp1; 311 return FSFATMOD; 312 } 313 if (ask(0, "Use continuation from FAT %d", fatnum)) { 314 *cp1 = *cp2; 315 return FSFATMOD; 316 } 317 return FSERROR; 318} 319 320/* 321 * Compare two FAT copies in memory. Resolve any conflicts and merge them 322 * into the first one. 323 */ 324int 325comparefat(struct bootblock *boot, struct fatEntry *first, 326 struct fatEntry *second, int fatnum) 327{ 328 cl_t cl; 329 int ret = FSOK; 330 331 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) 332 if (first[cl].next != second[cl].next) 333 ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum); 334 return ret; 335} 336 337void 338clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head) 339{ 340 cl_t p, q; 341 342 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) { 343 if (fat[p].head != head) 344 break; 345 q = fat[p].next; 346 fat[p].next = fat[p].head = CLUST_FREE; 347 fat[p].length = 0; 348 } 349} 350 351int 352tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *trunc) 353{ 354 if (ask(0, "Clear chain starting at %u", head)) { 355 clearchain(boot, fat, head); 356 return FSFATMOD; 357 } else if (ask(0, "Truncate")) { 358 *trunc = CLUST_EOF; 359 return FSFATMOD; 360 } else 361 return FSERROR; 362} 363 364/* 365 * Check a complete FAT in-memory for crosslinks 366 */ 367int 368checkfat(struct bootblock *boot, struct fatEntry *fat) 369{ 370 cl_t head, p, h, n; 371 u_int len; 372 int ret = 0; 373 int conf; 374 375 /* 376 * pass 1: figure out the cluster chains. 377 */ 378 for (head = CLUST_FIRST; head < boot->NumClusters; head++) { 379 /* find next untravelled chain */ 380 if (fat[head].head != 0 /* cluster already belongs to some chain */ 381 || fat[head].next == CLUST_FREE 382 || fat[head].next == CLUST_BAD) 383 continue; /* skip it. */ 384 385 /* follow the chain and mark all clusters on the way */ 386 for (len = 0, p = head; 387 p >= CLUST_FIRST && p < boot->NumClusters; 388 p = fat[p].next) { 389 fat[p].head = head; 390 len++; 391 } 392 393 /* the head record gets the length */ 394 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len; 395 } 396 397 /* 398 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because 399 * we didn't know the real start of the chain then - would have treated partial 400 * chains as interlinked with their main chain) 401 */ 402 for (head = CLUST_FIRST; head < boot->NumClusters; head++) { 403 /* find next untravelled chain */ 404 if (fat[head].head != head) 405 continue; 406 407 /* follow the chain to its end (hopefully) */ 408 for (p = head; 409 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters; 410 p = n) 411 if (fat[n].head != head) 412 break; 413 if (n >= CLUST_EOFS) 414 continue; 415 416 if (n == CLUST_FREE || n >= CLUST_RSRVD) { 417 pwarn("Cluster chain starting at %u ends with cluster marked %s\n", 418 head, rsrvdcltype(n)); 419 ret |= tryclear(boot, fat, head, &fat[p].next); 420 continue; 421 } 422 if (n < CLUST_FIRST || n >= boot->NumClusters) { 423 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n", 424 head, n); 425 ret |= tryclear(boot, fat, head, &fat[p].next); 426 continue; 427 } 428 pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n", 429 head, fat[n].head, n); 430 conf = tryclear(boot, fat, head, &fat[p].next); 431 if (ask(0, "Clear chain starting at %u", h = fat[n].head)) { 432 if (conf == FSERROR) { 433 /* 434 * Transfer the common chain to the one not cleared above. 435 */ 436 for (p = n; 437 p >= CLUST_FIRST && p < boot->NumClusters; 438 p = fat[p].next) { 439 if (h != fat[p].head) { 440 /* 441 * Have to reexamine this chain. 442 */ 443 head--; 444 break; 445 } 446 fat[p].head = head; 447 } 448 } 449 clearchain(boot, fat, h); 450 conf |= FSFATMOD; 451 } 452 ret |= conf; 453 } 454 455 return ret; 456} 457 458/* 459 * Write out FATs encoding them from the internal format 460 */ 461int 462writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat) 463{ 464 u_char *buffer, *p; 465 cl_t cl; 466 int i; 467 u_int32_t fatsz; 468 off_t off; 469 int ret = FSOK; 470 471 buffer = malloc(fatsz = boot->FATsecs * boot->BytesPerSec); 472 if (buffer == NULL) { 473 perror("No space for FAT"); 474 return FSFATAL; 475 } 476 memset(buffer, 0, fatsz); 477 boot->NumFree = 0; 478 p = buffer; 479 if (correct_fat) { 480 *p++ = (u_char)boot->Media; 481 *p++ = 0xff; 482 *p++ = 0xff; 483 switch (boot->ClustMask) { 484 case CLUST16_MASK: 485 *p++ = 0xff; 486 break; 487 case CLUST32_MASK: 488 *p++ = 0x0f; 489 *p++ = 0xff; 490 *p++ = 0xff; 491 *p++ = 0xff; 492 *p++ = 0x0f; 493 break; 494 } 495 } else { 496 /* use same FAT signature as the old FAT has */ 497 int count; 498 u_char *old_fat; 499 500 switch (boot->ClustMask) { 501 case CLUST32_MASK: 502 count = 8; 503 break; 504 case CLUST16_MASK: 505 count = 4; 506 break; 507 default: 508 count = 3; 509 break; 510 } 511 512 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0, 513 &old_fat)) { 514 free(buffer); 515 return FSFATAL; 516 } 517 518 memcpy(p, old_fat, count); 519 free(old_fat); 520 p += count; 521 } 522 523 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) { 524 switch (boot->ClustMask) { 525 case CLUST32_MASK: 526 if (fat[cl].next == CLUST_FREE) 527 boot->NumFree++; 528 *p++ = (u_char)fat[cl].next; 529 *p++ = (u_char)(fat[cl].next >> 8); 530 *p++ = (u_char)(fat[cl].next >> 16); 531 *p &= 0xf0; 532 *p++ |= (fat[cl].next >> 24)&0x0f; 533 break; 534 case CLUST16_MASK: 535 if (fat[cl].next == CLUST_FREE) 536 boot->NumFree++; 537 *p++ = (u_char)fat[cl].next; 538 *p++ = (u_char)(fat[cl].next >> 8); 539 break; 540 default: 541 if (fat[cl].next == CLUST_FREE) 542 boot->NumFree++; 543 if (cl + 1 < boot->NumClusters 544 && fat[cl + 1].next == CLUST_FREE) 545 boot->NumFree++; 546 *p++ = (u_char)fat[cl].next; 547 *p++ = (u_char)((fat[cl].next >> 8) & 0xf) 548 |(u_char)(fat[cl+1].next << 4); 549 *p++ = (u_char)(fat[++cl].next >> 4); 550 break; 551 } 552 } 553 for (i = 0; i < boot->FATs; i++) { 554 off = boot->ResSectors + i * boot->FATsecs; 555 off *= boot->BytesPerSec; 556 if (lseek(fs, off, SEEK_SET) != off 557 || write(fs, buffer, fatsz) != fatsz) { 558 perror("Unable to write FAT"); 559 ret = FSFATAL; /* Return immediately? XXX */ 560 } 561 } 562 free(buffer); 563 return ret; 564} 565 566/* 567 * Check a complete in-memory FAT for lost cluster chains 568 */ 569int 570checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat) 571{ 572 cl_t head; 573 int mod = FSOK; 574 int ret; 575 576 for (head = CLUST_FIRST; head < boot->NumClusters; head++) { 577 /* find next untravelled chain */ 578 if (fat[head].head != head 579 || fat[head].next == CLUST_FREE 580 || (fat[head].next >= CLUST_RSRVD 581 && fat[head].next < CLUST_EOFS) 582 || (fat[head].flags & FAT_USED)) 583 continue; 584 585 pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n", 586 head, fat[head].length); 587 mod |= ret = reconnect(dosfs, boot, fat, head); 588 if (mod & FSFATAL) 589 break; 590 if (ret == FSERROR && ask(0, "Clear")) { 591 clearchain(boot, fat, head); 592 mod |= FSFATMOD; 593 } 594 } 595 finishlf(); 596 597 if (boot->FSInfo) { 598 ret = 0; 599 if (boot->FSFree != boot->NumFree) { 600 pwarn("Free space in FSInfo block (%d) not correct (%d)\n", 601 boot->FSFree, boot->NumFree); 602 if (ask(1, "fix")) { 603 boot->FSFree = boot->NumFree; 604 ret = 1; 605 } 606 } 607 if (boot->NumFree && fat[boot->FSNext].next != CLUST_FREE) { 608 pwarn("Next free cluster in FSInfo block (%u) not free\n", 609 boot->FSNext); 610 if (ask(1, "fix")) 611 for (head = CLUST_FIRST; head < boot->NumClusters; head++) 612 if (fat[head].next == CLUST_FREE) { 613 boot->FSNext = head; 614 ret = 1; 615 break; 616 } 617 } 618 if (ret) 619 mod |= writefsinfo(dosfs, boot); 620 } 621 622 return mod; 623} 624