fat.c revision 1.19
1 /* $NetBSD: fat.c,v 1.19 2006/06/06 16:19:11 christos Exp $ */ 2 3 /* 4 * Copyright (C) 1995, 1996, 1997 Wolfgang Solfrank 5 * Copyright (c) 1995 Martin Husemann 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by Martin Husemann 18 * and Wolfgang Solfrank. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 26 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 28 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 29 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 30 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 31 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 32 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 33 */ 34 35 36 #include <sys/cdefs.h> 37 #ifndef lint 38 __RCSID("$NetBSD: fat.c,v 1.19 2006/06/06 16:19:11 christos Exp $"); 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 50 static int checkclnum(struct bootblock *, int, cl_t, cl_t *); 51 static int clustdiffer(cl_t, cl_t *, cl_t *, int); 52 static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *); 53 static int _readfat(int, struct bootblock *, int, u_char **); 54 55 /* 56 * Check a cluster number for valid value 57 */ 58 static int 59 checkclnum(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 */ 89 static int 90 _readfat(int fs, struct bootblock *boot, int no, u_char **buffer) 91 { 92 off_t off; 93 size_t len; 94 95 *buffer = malloc(len = boot->FATsecs * boot->BytesPerSec); 96 if (*buffer == NULL) { 97 perr("No space for FAT sectors (%zu)", len); 98 return 0; 99 } 100 101 off = boot->ResSectors + no * boot->FATsecs; 102 off *= boot->BytesPerSec; 103 104 if (lseek(fs, off, SEEK_SET) != off) { 105 perr("Unable to read FAT"); 106 goto err; 107 } 108 109 if (read(fs, *buffer, boot->FATsecs * boot->BytesPerSec) 110 != boot->FATsecs * boot->BytesPerSec) { 111 perr("Unable to read FAT"); 112 goto err; 113 } 114 115 return 1; 116 117 err: 118 free(*buffer); 119 return 0; 120 } 121 122 /* 123 * Read a FAT and decode it into internal format 124 */ 125 int 126 readfat(int fs, struct bootblock *boot, int no, struct fatEntry **fp) 127 { 128 struct fatEntry *fat; 129 u_char *buffer, *p; 130 cl_t cl; 131 int ret = FSOK; 132 size_t len; 133 134 boot->NumFree = boot->NumBad = 0; 135 136 if (!_readfat(fs, boot, no, &buffer)) 137 return FSFATAL; 138 139 fat = malloc(len = boot->NumClusters * sizeof(struct fatEntry)); 140 if (fat == NULL) { 141 perr("No space for FAT clusters (%zu)", len); 142 free(buffer); 143 return FSFATAL; 144 } 145 (void)memset(fat, 0, len); 146 147 if (buffer[0] != boot->Media 148 || buffer[1] != 0xff || buffer[2] != 0xff 149 || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff) 150 || (boot->ClustMask == CLUST32_MASK 151 && ((buffer[3]&0x0f) != 0x0f 152 || buffer[4] != 0xff || buffer[5] != 0xff 153 || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) { 154 155 /* Windows 95 OSR2 (and possibly any later) changes 156 * the FAT signature to 0xXXffff7f for FAT16 and to 157 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the 158 * filesystem is dirty if it doesn't reboot cleanly. 159 * Check this special condition before errorring out. 160 */ 161 if (buffer[0] == boot->Media && buffer[1] == 0xff 162 && buffer[2] == 0xff 163 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f) 164 || (boot->ClustMask == CLUST32_MASK 165 && buffer[3] == 0x0f && buffer[4] == 0xff 166 && buffer[5] == 0xff && buffer[6] == 0xff 167 && buffer[7] == 0x07))) 168 ret |= FSDIRTY; 169 else { 170 /* just some odd byte sequence in FAT */ 171 172 switch (boot->ClustMask) { 173 case CLUST32_MASK: 174 pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n", 175 "FAT starts with odd byte sequence", 176 buffer[0], buffer[1], buffer[2], buffer[3], 177 buffer[4], buffer[5], buffer[6], buffer[7]); 178 break; 179 case CLUST16_MASK: 180 pwarn("%s (%02x%02x%02x%02x)\n", 181 "FAT starts with odd byte sequence", 182 buffer[0], buffer[1], buffer[2], buffer[3]); 183 break; 184 default: 185 pwarn("%s (%02x%02x%02x)\n", 186 "FAT starts with odd byte sequence", 187 buffer[0], buffer[1], buffer[2]); 188 break; 189 } 190 191 192 if (ask(1, "Correct")) 193 ret |= FSFIXFAT; 194 } 195 } 196 switch (boot->ClustMask) { 197 case CLUST32_MASK: 198 p = buffer + 8; 199 break; 200 case CLUST16_MASK: 201 p = buffer + 4; 202 break; 203 default: 204 p = buffer + 3; 205 break; 206 } 207 for (cl = CLUST_FIRST; cl < boot->NumClusters;) { 208 switch (boot->ClustMask) { 209 case CLUST32_MASK: 210 fat[cl].next = p[0] + (p[1] << 8) 211 + (p[2] << 16) + (p[3] << 24); 212 fat[cl].next &= boot->ClustMask; 213 ret |= checkclnum(boot, no, cl, &fat[cl].next); 214 cl++; 215 p += 4; 216 break; 217 case CLUST16_MASK: 218 fat[cl].next = p[0] + (p[1] << 8); 219 ret |= checkclnum(boot, no, cl, &fat[cl].next); 220 cl++; 221 p += 2; 222 break; 223 default: 224 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff; 225 ret |= checkclnum(boot, no, cl, &fat[cl].next); 226 cl++; 227 if (cl >= boot->NumClusters) 228 break; 229 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff; 230 ret |= checkclnum(boot, no, cl, &fat[cl].next); 231 cl++; 232 p += 3; 233 break; 234 } 235 } 236 237 free(buffer); 238 if (ret & FSFATAL) { 239 free(fat); 240 *fp = NULL; 241 } else 242 *fp = fat; 243 return ret; 244 } 245 246 /* 247 * Get type of reserved cluster 248 */ 249 const char * 250 rsrvdcltype(cl_t cl) 251 { 252 if (cl == CLUST_FREE) 253 return "free"; 254 if (cl < CLUST_BAD) 255 return "reserved"; 256 if (cl > CLUST_BAD) 257 return "as EOF"; 258 return "bad"; 259 } 260 261 static int 262 clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, int fatnum) 263 { 264 if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) { 265 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) { 266 if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD 267 && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD) 268 || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) { 269 pwarn("Cluster %u is marked %s with different indicators, ", 270 cl, rsrvdcltype(*cp1)); 271 if (ask(1, "fix")) { 272 *cp2 = *cp1; 273 return FSFATMOD; 274 } 275 return FSFATAL; 276 } 277 pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %d\n", 278 cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum); 279 if (ask(0, "use FAT 0's entry")) { 280 *cp2 = *cp1; 281 return FSFATMOD; 282 } 283 if (ask(0, "use FAT %d's entry", fatnum)) { 284 *cp1 = *cp2; 285 return FSFATMOD; 286 } 287 return FSFATAL; 288 } 289 pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n", 290 cl, rsrvdcltype(*cp1), *cp2, fatnum); 291 if (ask(0, "Use continuation from FAT %d", fatnum)) { 292 *cp1 = *cp2; 293 return FSFATMOD; 294 } 295 if (ask(0, "Use mark from FAT 0")) { 296 *cp2 = *cp1; 297 return FSFATMOD; 298 } 299 return FSFATAL; 300 } 301 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) { 302 pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %d\n", 303 cl, *cp1, rsrvdcltype(*cp2), fatnum); 304 if (ask(0, "Use continuation from FAT 0")) { 305 *cp2 = *cp1; 306 return FSFATMOD; 307 } 308 if (ask(0, "Use mark from FAT %d", fatnum)) { 309 *cp1 = *cp2; 310 return FSFATMOD; 311 } 312 return FSERROR; 313 } 314 pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %d\n", 315 cl, *cp1, *cp2, fatnum); 316 if (ask(0, "Use continuation from FAT 0")) { 317 *cp2 = *cp1; 318 return FSFATMOD; 319 } 320 if (ask(0, "Use continuation from FAT %d", fatnum)) { 321 *cp1 = *cp2; 322 return FSFATMOD; 323 } 324 return FSERROR; 325 } 326 327 /* 328 * Compare two FAT copies in memory. Resolve any conflicts and merge them 329 * into the first one. 330 */ 331 int 332 comparefat(struct bootblock *boot, struct fatEntry *first, 333 struct fatEntry *second, int fatnum) 334 { 335 cl_t cl; 336 int ret = FSOK; 337 338 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) 339 if (first[cl].next != second[cl].next) 340 ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum); 341 return ret; 342 } 343 344 void 345 clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head) 346 { 347 cl_t p, q; 348 349 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) { 350 if (fat[p].head != head) 351 break; 352 q = fat[p].next; 353 fat[p].next = fat[p].head = CLUST_FREE; 354 fat[p].length = 0; 355 } 356 } 357 358 int 359 tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *truncp) 360 { 361 if (ask(0, "Clear chain starting at %u", head)) { 362 clearchain(boot, fat, head); 363 return FSFATMOD; 364 } else if (ask(0, "Truncate")) { 365 *truncp = CLUST_EOF; 366 return FSFATMOD; 367 } else 368 return FSERROR; 369 } 370 371 /* 372 * Check a complete FAT in-memory for crosslinks 373 */ 374 int 375 checkfat(struct bootblock *boot, struct fatEntry *fat) 376 { 377 cl_t head, p, h, n; 378 u_int len; 379 int ret = 0; 380 int conf; 381 382 /* 383 * pass 1: figure out the cluster chains. 384 */ 385 for (head = CLUST_FIRST; head < boot->NumClusters; head++) { 386 /* find next untravelled chain */ 387 if (fat[head].head != 0 /* cluster already belongs to some chain */ 388 || fat[head].next == CLUST_FREE 389 || fat[head].next == CLUST_BAD) 390 continue; /* skip it. */ 391 392 /* follow the chain and mark all clusters on the way */ 393 for (len = 0, p = head; 394 p >= CLUST_FIRST && p < boot->NumClusters; 395 p = fat[p].next) { 396 fat[p].head = head; 397 len++; 398 } 399 400 /* the head record gets the length */ 401 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len; 402 } 403 404 /* 405 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because 406 * we didn't know the real start of the chain then - would have treated partial 407 * chains as interlinked with their main chain) 408 */ 409 for (head = CLUST_FIRST; head < boot->NumClusters; head++) { 410 /* find next untravelled chain */ 411 if (fat[head].head != head) 412 continue; 413 414 /* follow the chain to its end (hopefully) */ 415 for (p = head; 416 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters; 417 p = n) 418 if (fat[n].head != head) 419 break; 420 if (n >= CLUST_EOFS) 421 continue; 422 423 if (n == CLUST_FREE || n >= CLUST_RSRVD) { 424 pwarn("Cluster chain starting at %u ends with cluster marked %s\n", 425 head, rsrvdcltype(n)); 426 ret |= tryclear(boot, fat, head, &fat[p].next); 427 continue; 428 } 429 if (n < CLUST_FIRST || n >= boot->NumClusters) { 430 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n", 431 head, n); 432 ret |= tryclear(boot, fat, head, &fat[p].next); 433 continue; 434 } 435 pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n", 436 head, fat[n].head, n); 437 conf = tryclear(boot, fat, head, &fat[p].next); 438 if (ask(0, "Clear chain starting at %u", h = fat[n].head)) { 439 if (conf == FSERROR) { 440 /* 441 * Transfer the common chain to the one not cleared above. 442 */ 443 for (p = n; 444 p >= CLUST_FIRST && p < boot->NumClusters; 445 p = fat[p].next) { 446 if (h != fat[p].head) { 447 /* 448 * Have to reexamine this chain. 449 */ 450 head--; 451 break; 452 } 453 fat[p].head = head; 454 } 455 } 456 clearchain(boot, fat, h); 457 conf |= FSFATMOD; 458 } 459 ret |= conf; 460 } 461 462 return ret; 463 } 464 465 /* 466 * Write out FATs encoding them from the internal format 467 */ 468 int 469 writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat) 470 { 471 u_char *buffer, *p; 472 cl_t cl; 473 int i; 474 size_t fatsz; 475 off_t off; 476 int ret = FSOK; 477 478 buffer = malloc(fatsz = boot->FATsecs * boot->BytesPerSec); 479 if (buffer == NULL) { 480 perr("No space for FAT sectors (%zu)", fatsz); 481 return FSFATAL; 482 } 483 memset(buffer, 0, fatsz); 484 boot->NumFree = 0; 485 p = buffer; 486 if (correct_fat) { 487 *p++ = (u_char)boot->Media; 488 *p++ = 0xff; 489 *p++ = 0xff; 490 switch (boot->ClustMask) { 491 case CLUST16_MASK: 492 *p++ = 0xff; 493 break; 494 case CLUST32_MASK: 495 *p++ = 0x0f; 496 *p++ = 0xff; 497 *p++ = 0xff; 498 *p++ = 0xff; 499 *p++ = 0x0f; 500 break; 501 } 502 } else { 503 /* use same FAT signature as the old FAT has */ 504 int count; 505 u_char *old_fat; 506 507 switch (boot->ClustMask) { 508 case CLUST32_MASK: 509 count = 8; 510 break; 511 case CLUST16_MASK: 512 count = 4; 513 break; 514 default: 515 count = 3; 516 break; 517 } 518 519 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0, 520 &old_fat)) { 521 free(buffer); 522 return FSFATAL; 523 } 524 525 memcpy(p, old_fat, count); 526 free(old_fat); 527 p += count; 528 } 529 530 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) { 531 switch (boot->ClustMask) { 532 case CLUST32_MASK: 533 if (fat[cl].next == CLUST_FREE) 534 boot->NumFree++; 535 *p++ = (u_char)fat[cl].next; 536 *p++ = (u_char)(fat[cl].next >> 8); 537 *p++ = (u_char)(fat[cl].next >> 16); 538 *p &= 0xf0; 539 *p++ |= (fat[cl].next >> 24)&0x0f; 540 break; 541 case CLUST16_MASK: 542 if (fat[cl].next == CLUST_FREE) 543 boot->NumFree++; 544 *p++ = (u_char)fat[cl].next; 545 *p++ = (u_char)(fat[cl].next >> 8); 546 break; 547 default: 548 if (fat[cl].next == CLUST_FREE) 549 boot->NumFree++; 550 if (cl + 1 < boot->NumClusters 551 && fat[cl + 1].next == CLUST_FREE) 552 boot->NumFree++; 553 *p++ = (u_char)fat[cl].next; 554 *p++ = (u_char)((fat[cl].next >> 8) & 0xf) 555 |(u_char)(fat[cl+1].next << 4); 556 *p++ = (u_char)(fat[++cl].next >> 4); 557 break; 558 } 559 } 560 for (i = 0; i < boot->FATs; i++) { 561 off = boot->ResSectors + i * boot->FATsecs; 562 off *= boot->BytesPerSec; 563 if (lseek(fs, off, SEEK_SET) != off 564 || write(fs, buffer, fatsz) != fatsz) { 565 perr("Unable to write FAT"); 566 ret = FSFATAL; /* Return immediately? XXX */ 567 } 568 } 569 free(buffer); 570 return ret; 571 } 572 573 /* 574 * Check a complete in-memory FAT for lost cluster chains 575 */ 576 int 577 checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat) 578 { 579 cl_t head; 580 int mod = FSOK; 581 int ret; 582 583 for (head = CLUST_FIRST; head < boot->NumClusters; head++) { 584 /* find next untravelled chain */ 585 if (fat[head].head != head 586 || fat[head].next == CLUST_FREE 587 || (fat[head].next >= CLUST_RSRVD 588 && fat[head].next < CLUST_EOFS) 589 || (fat[head].flags & FAT_USED)) 590 continue; 591 592 pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n", 593 head, fat[head].length); 594 mod |= ret = reconnect(dosfs, boot, fat, head); 595 if (mod & FSFATAL) 596 break; 597 if (ret == FSERROR && ask(0, "Clear")) { 598 clearchain(boot, fat, head); 599 mod |= FSFATMOD; 600 } 601 } 602 finishlf(); 603 604 if (boot->FSInfo) { 605 ret = 0; 606 if (boot->FSFree != boot->NumFree) { 607 pwarn("Free space in FSInfo block (%d) not correct (%d)\n", 608 boot->FSFree, boot->NumFree); 609 if (ask(1, "fix")) { 610 boot->FSFree = boot->NumFree; 611 ret = 1; 612 } 613 } 614 if (boot->NumFree && fat[boot->FSNext].next != CLUST_FREE) { 615 pwarn("Next free cluster in FSInfo block (%u) not free\n", 616 boot->FSNext); 617 if (ask(1, "fix")) 618 for (head = CLUST_FIRST; head < boot->NumClusters; head++) 619 if (fat[head].next == CLUST_FREE) { 620 boot->FSNext = head; 621 ret = 1; 622 break; 623 } 624 } 625 if (ret) 626 mod |= writefsinfo(dosfs, boot); 627 } 628 629 return mod; 630 } 631
Indexes created Thu Sep 25 16:09:42 GMT 2025