usr/src/boot/lib/libstand/dosfs.c

   1 /*
   2  * Copyright (c) 1996, 1998 Robert Nordier
   3  * All rights reserved.
   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
  12  *    the documentation and/or other materials provided with the
  13  *    distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS
  16  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  17  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY
  19  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  21  * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  22  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
  23  * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
  25  * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 #include <sys/cdefs.h>
  29 __FBSDID("$FreeBSD$");
  30
  31 /*
  32  * Readonly filesystem for Microsoft FAT12/FAT16/FAT32 filesystems,
  33  * also supports VFAT.
  34  */
  35
  36 #include <sys/types.h>
  37 #include <string.h>
  38 #include <stddef.h>
  39
  40 #include "stand.h"
  41
  42 #include "dosfs.h"
  43
  44
  45 static int      dos_open(const char *path, struct open_file *fd);
  46 static int      dos_close(struct open_file *fd);
  47 static int      dos_read(struct open_file *fd, void *buf, size_t size, size_t *resid);
  48 static off_t    dos_seek(struct open_file *fd, off_t offset, int whence);
  49 static int      dos_stat(struct open_file *fd, struct stat *sb);
  50 static int      dos_readdir(struct open_file *fd, struct dirent *d);
  51
  52 struct fs_ops dosfs_fsops = {
  53         "dosfs",
  54         dos_open,
  55         dos_close,
  56         dos_read,
  57         null_write,
  58         dos_seek,
  59         dos_stat,
  60         dos_readdir
  61 };
  62
  63 #define SECSIZ  512             /* sector size */
  64 #define SSHIFT    9             /* SECSIZ shift */
  65 #define DEPSEC   16             /* directory entries per sector */
  66 #define DSHIFT    4             /* DEPSEC shift */
  67 #define LOCLUS    2             /* lowest cluster number */
  68
  69 /* DOS "BIOS Parameter Block" */
  70 typedef struct {
  71     u_char secsiz[2];           /* sector size */
  72     u_char spc;                 /* sectors per cluster */
  73     u_char ressec[2];           /* reserved sectors */
  74     u_char fats;                /* FATs */
  75     u_char dirents[2];          /* root directory entries */
  76     u_char secs[2];             /* total sectors */
  77     u_char media;               /* media descriptor */
  78     u_char spf[2];              /* sectors per FAT */
  79     u_char spt[2];              /* sectors per track */
  80     u_char heads[2];            /* drive heads */
  81     u_char hidsec[4];           /* hidden sectors */
  82     u_char lsecs[4];            /* huge sectors */
  83     u_char lspf[4];             /* huge sectors per FAT */
  84     u_char xflg[2];             /* flags */
  85     u_char vers[2];             /* filesystem version */
  86     u_char rdcl[4];             /* root directory start cluster */
  87     u_char infs[2];             /* filesystem info sector */
  88     u_char bkbs[2];             /* backup boot sector */
  89 } DOS_BPB;
  90
  91 /* Initial portion of DOS boot sector */
  92 typedef struct {
  93     u_char jmp[3];              /* usually 80x86 'jmp' opcode */
  94     u_char oem[8];              /* OEM name and version */
  95     DOS_BPB bpb;                /* BPB */
  96 } DOS_BS;
  97
  98 /* Supply missing "." and ".." root directory entries */
  99 static const char *const dotstr[2] = {".", ".."};
 100 static DOS_DE dot[2] = {
 101     {".       ", "   ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
 102      {0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}},
 103     {"..      ", "   ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
 104      {0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}}
 105 };
 106
 107 /* The usual conversion macros to avoid multiplication and division */
 108 #define bytsec(n)      ((n) >> SSHIFT)
 109 #define secbyt(s)      ((s) << SSHIFT)
 110 #define entsec(e)      ((e) >> DSHIFT)
 111 #define bytblk(fs, n)  ((n) >> (fs)->bshift)
 112 #define blkbyt(fs, b)  ((b) << (fs)->bshift)
 113 #define secblk(fs, s)  ((s) >> ((fs)->bshift - SSHIFT))
 114 #define blksec(fs, b)  ((b) << ((fs)->bshift - SSHIFT))
 115
 116 /* Convert cluster number to offset within filesystem */
 117 #define blkoff(fs, b) (secbyt((fs)->lsndta) + blkbyt(fs, (b) - LOCLUS))
 118
 119 /* Convert cluster number to logical sector number */
 120 #define blklsn(fs, b)  ((fs)->lsndta + blksec(fs, (b) - LOCLUS))
 121
 122 /* Convert cluster number to offset within FAT */
 123 #define fatoff(sz, c)  ((sz) == 12 ? (c) + ((c) >> 1) :  \
 124                         (sz) == 16 ? (c) << 1 :          \
 125                         (c) << 2)
 126
 127 /* Does cluster number reference a valid data cluster? */
 128 #define okclus(fs, c)  ((c) >= LOCLUS && (c) <= (fs)->xclus)
 129
 130 /* Get start cluster from directory entry */
 131 #define stclus(sz, de)  ((sz) != 32 ? cv2((de)->clus) :          \
 132                          ((u_int)cv2((de)->dex.h_clus) << 16) |  \
 133                          cv2((de)->clus))
 134
 135 /*
 136  * fat cache metadata
 137  */
 138 struct fatcache {
 139         int unit;       /* disk unit number */
 140         int size;       /* buffer (and fat) size in sectors */
 141         u_char *buf;
 142 };
 143
 144 static struct fatcache fat;
 145
 146 static int dosunmount(DOS_FS *);
 147 static int parsebs(DOS_FS *, DOS_BS *);
 148 static int namede(DOS_FS *, const char *, DOS_DE **);
 149 static int lookup(DOS_FS *, u_int, const char *, DOS_DE **);
 150 static void cp_xdnm(u_char *, DOS_XDE *);
 151 static void cp_sfn(u_char *, DOS_DE *);
 152 static off_t fsize(DOS_FS *, DOS_DE *);
 153 static int fatcnt(DOS_FS *, u_int);
 154 static int fatget(DOS_FS *, u_int *);
 155 static int fatend(u_int, u_int);
 156 static int ioread(DOS_FS *, u_int, void *, u_int);
 157 static int ioget(struct open_file *, daddr_t, size_t, void *, u_int);
 158
 159 static void
 160 dos_read_fat(DOS_FS *fs, struct open_file *fd)
 161 {
 162     struct devdesc *dd = fd->f_devdata;
 163
 164     if (fat.buf != NULL) {              /* can we reuse old buffer? */
 165         if (fat.size != fs->spf) {
 166             free(fat.buf);              /* no, free old buffer */
 167             fat.buf = NULL;
 168         }
 169     }
 170
 171     if (fat.buf == NULL)
 172         fat.buf = malloc(secbyt(fs->spf));
 173
 174     if (fat.buf != NULL) {
 175         if (ioget(fd, fs->lsnfat, 0, fat.buf, secbyt(fs->spf)) == 0) {
 176             fat.size = fs->spf;
 177             fat.unit = dd->d_unit;
 178             return;
 179         }
 180     }
 181     if (fat.buf != NULL)        /* got IO error */
 182         free(fat.buf);
 183     fat.buf = NULL;
 184     fat.unit = -1;      /* impossible unit */
 185     fat.size = 0;
 186 }
 187
 188 /*
 189  * Mount DOS filesystem
 190  */
 191 static int
 192 dos_mount(DOS_FS *fs, struct open_file *fd)
 193 {
 194     int err;
 195     struct devdesc *dd = fd->f_devdata;
 196     u_char *buf;
 197
 198     bzero(fs, sizeof(DOS_FS));
 199     fs->fd = fd;
 200
 201     if ((err = !(buf = malloc(secbyt(1))) ? errno : 0) ||
 202         (err = ioget(fs->fd, 0, 0, buf, secbyt(1))) ||
 203         (err = parsebs(fs, (DOS_BS *)buf))) {
 204         if (buf != NULL)
 205             free(buf);
 206         (void)dosunmount(fs);
 207         return(err);
 208     }
 209     free(buf);
 210
 211     if (fat.buf == NULL || fat.unit != dd->d_unit)
 212         dos_read_fat(fs, fd);
 213
 214     fs->root = dot[0];
 215     fs->root.name[0] = ' ';
 216     if (fs->fatsz == 32) {
 217         fs->root.clus[0] = fs->rdcl & 0xff;
 218         fs->root.clus[1] = (fs->rdcl >> 8) & 0xff;
 219         fs->root.dex.h_clus[0] = (fs->rdcl >> 16) & 0xff;
 220         fs->root.dex.h_clus[1] = (fs->rdcl >> 24) & 0xff;
 221     }
 222     return 0;
 223 }
 224
 225 /*
 226  * Unmount mounted filesystem
 227  */
 228 static int
 229 dos_unmount(DOS_FS *fs)
 230 {
 231     int err;
 232
 233     if (fs->links)
 234         return(EBUSY);
 235     if ((err = dosunmount(fs)))
 236         return(err);
 237     return 0;
 238 }
 239
 240 /*
 241  * Common code shared by dos_mount() and dos_unmount()
 242  */
 243 static int
 244 dosunmount(DOS_FS *fs)
 245 {
 246     free(fs);
 247     return(0);
 248 }
 249
 250 /*
 251  * Open DOS file
 252  */
 253 static int
 254 dos_open(const char *path, struct open_file *fd)
 255 {
 256     DOS_DE *de;
 257     DOS_FILE *f;
 258     DOS_FS *fs;
 259     u_int size, clus;
 260     int err = 0;
 261
 262     /* Allocate mount structure, associate with open */
 263     fs = malloc(sizeof(DOS_FS));
 264
 265     if ((err = dos_mount(fs, fd)))
 266         goto out;
 267
 268     if ((err = namede(fs, path, &de)))
 269         goto out;
 270
 271     clus = stclus(fs->fatsz, de);
 272     size = cv4(de->size);
 273
 274     if ((!(de->attr & FA_DIR) && (!clus != !size)) ||
 275         ((de->attr & FA_DIR) && size) ||
 276         (clus && !okclus(fs, clus))) {
 277         err = EINVAL;
 278         goto out;
 279     }
 280     f = malloc(sizeof(DOS_FILE));
 281     bzero(f, sizeof(DOS_FILE));
 282     f->fs = fs;
 283     fs->links++;
 284     f->de = *de;
 285     fd->f_fsdata = (void *)f;
 286
 287  out:
 288     return(err);
 289 }
 290
 291 /*
 292  * Read from file
 293  */
 294 static int
 295 dos_read(struct open_file *fd, void *buf, size_t nbyte, size_t *resid)
 296 {
 297     off_t size;
 298     u_int nb, off, clus, c, cnt, n;
 299     DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
 300     int err = 0;
 301
 302     /*
 303      * as ioget() can be called *a lot*, use twiddle here.
 304      * also 4 seems to be good value not to slow loading down too much:
 305      * with 270MB file (~540k ioget() calls, twiddle can easily waste 4-5sec.
 306      */
 307     twiddle(4);
 308     nb = (u_int)nbyte;
 309     if ((size = fsize(f->fs, &f->de)) == -1)
 310         return EINVAL;
 311     if (nb > (n = size - f->offset))
 312         nb = n;
 313     off = f->offset;
 314     if ((clus = stclus(f->fs->fatsz, &f->de)))
 315         off &= f->fs->bsize - 1;
 316     c = f->c;
 317     cnt = nb;
 318     while (cnt) {
 319         n = 0;
 320         if (!c) {
 321             if ((c = clus))
 322                 n = bytblk(f->fs, f->offset);
 323         } else if (!off)
 324             n++;
 325         while (n--) {
 326             if ((err = fatget(f->fs, &c)))
 327                 goto out;
 328             if (!okclus(f->fs, c)) {
 329                 err = EINVAL;
 330                 goto out;
 331             }
 332         }
 333         if (!clus || (n = f->fs->bsize - off) > cnt)
 334             n = cnt;
 335         if ((err = ioread(f->fs, (c ? blkoff(f->fs, c) :
 336                                       secbyt(f->fs->lsndir)) + off, buf, n)))
 337             goto out;
 338         f->offset += n;
 339         f->c = c;
 340         off = 0;
 341         buf = (char *)buf + n;
 342         cnt -= n;
 343     }
 344  out:
 345     if (resid)
 346         *resid = nbyte - nb + cnt;
 347     return(err);
 348 }
 349
 350 /*
 351  * Reposition within file
 352  */
 353 static off_t
 354 dos_seek(struct open_file *fd, off_t offset, int whence)
 355 {
 356     off_t off;
 357     u_int size;
 358     DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
 359
 360     size = cv4(f->de.size);
 361     switch (whence) {
 362     case SEEK_SET:
 363         off = 0;
 364         break;
 365     case SEEK_CUR:
 366         off = f->offset;
 367         break;
 368     case SEEK_END:
 369         off = size;
 370         break;
 371     default:
 372         errno = EINVAL;
 373         return(-1);
 374     }
 375     off += offset;
 376     if (off < 0 || off > size) {
 377         errno = EINVAL;
 378         return(-1);
 379     }
 380     f->offset = (u_int)off;
 381     f->c = 0;
 382     return(off);
 383 }
 384
 385 /*
 386  * Close open file
 387  */
 388 static int
 389 dos_close(struct open_file *fd)
 390 {
 391     DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
 392     DOS_FS *fs = f->fs;
 393
 394     f->fs->links--;
 395     free(f);
 396     dos_unmount(fs);
 397     return 0;
 398 }
 399
 400 /*
 401  * Return some stat information on a file.
 402  */
 403 static int
 404 dos_stat(struct open_file *fd, struct stat *sb)
 405 {
 406     DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
 407
 408     /* only important stuff */
 409     sb->st_mode = f->de.attr & FA_DIR ? S_IFDIR | 0555 : S_IFREG | 0444;
 410     sb->st_nlink = 1;
 411     sb->st_uid = 0;
 412     sb->st_gid = 0;
 413     if ((sb->st_size = fsize(f->fs, &f->de)) == -1)
 414         return EINVAL;
 415     return (0);
 416 }
 417
 418 static int
 419 dos_checksum(char *name, char *ext)
 420 {
 421     int x, i;
 422     char buf[11];
 423
 424     bcopy(name, buf, 8);
 425     bcopy(ext, buf+8, 3);
 426     x = 0;
 427     for (i = 0; i < 11; i++) {
 428         x = ((x & 1) << 7) | (x >> 1);
 429         x += buf[i];
 430         x &= 0xff;
 431     }
 432     return (x);
 433 }
 434
 435 static int
 436 dos_readdir(struct open_file *fd, struct dirent *d)
 437 {
 438     /* DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; */
 439     u_char fn[261];
 440     DOS_DIR dd;
 441     size_t res;
 442     u_int chk, x, xdn;
 443     int err;
 444
 445     x = chk = 0;
 446     while (1) {
 447         xdn = x;
 448         x = 0;
 449         err = dos_read(fd, &dd, sizeof(dd), &res);
 450         if (err)
 451             return (err);
 452         if (res == sizeof(dd))
 453             return (ENOENT);
 454         if (dd.de.name[0] == 0)
 455             return (ENOENT);
 456
 457         /* Skip deleted entries */
 458         if (dd.de.name[0] == 0xe5)
 459             continue;
 460
 461         /* Check if directory entry is volume label */
 462         if (dd.de.attr & FA_LABEL) {
 463             /*
 464              * If volume label set, check if the current entry is
 465              * extended entry (FA_XDE) for long file names.
 466              */
 467             if ((dd.de.attr & FA_MASK) == FA_XDE) {
 468                 /*
 469                  * Read through all following extended entries
 470                  * to get the long file name. 0x40 marks the
 471                  * last entry containing part of long file name.
 472                  */
 473                 if (dd.xde.seq & 0x40)
 474                     chk = dd.xde.chk;
 475                 else if (dd.xde.seq != xdn - 1 || dd.xde.chk != chk)
 476                     continue;
 477                 x = dd.xde.seq & ~0x40;
 478                 if (x < 1 || x > 20) {
 479                     x = 0;
 480                     continue;
 481                 }
 482                 cp_xdnm(fn, &dd.xde);
 483             } else {
 484                 /* skip only volume label entries */
 485                 continue;
 486             }
 487         } else {
 488             if (xdn == 1) {
 489                 x = dos_checksum(dd.de.name, dd.de.ext);
 490                 if (x == chk)
 491                     break;
 492             } else {
 493                 cp_sfn(fn, &dd.de);
 494                 break;
 495             }
 496             x = 0;
 497         }
 498     }
 499
 500     d->d_fileno = (dd.de.clus[1] << 8) + dd.de.clus[0];
 501     d->d_reclen = sizeof(*d);
 502     d->d_type = (dd.de.attr & FA_DIR) ? DT_DIR : DT_REG;
 503     memcpy(d->d_name, fn, sizeof(d->d_name));
 504     return(0);
 505 }
 506
 507 /*
 508  * Parse DOS boot sector
 509  */
 510 static int
 511 parsebs(DOS_FS *fs, DOS_BS *bs)
 512 {
 513     u_int sc;
 514
 515     if ((bs->jmp[0] != 0x69 &&
 516          bs->jmp[0] != 0xe9 &&
 517          (bs->jmp[0] != 0xeb || bs->jmp[2] != 0x90)) ||
 518         bs->bpb.media < 0xf0)
 519         return EINVAL;
 520     if (cv2(bs->bpb.secsiz) != SECSIZ)
 521         return EINVAL;
 522     if (!(fs->spc = bs->bpb.spc) || fs->spc & (fs->spc - 1))
 523         return EINVAL;
 524     fs->bsize = secbyt(fs->spc);
 525     fs->bshift = ffs(fs->bsize) - 1;
 526     if ((fs->spf = cv2(bs->bpb.spf))) {
 527         if (bs->bpb.fats != 2)
 528             return EINVAL;
 529         if (!(fs->dirents = cv2(bs->bpb.dirents)))
 530             return EINVAL;
 531     } else {
 532         if (!(fs->spf = cv4(bs->bpb.lspf)))
 533             return EINVAL;
 534         if (!bs->bpb.fats || bs->bpb.fats > 16)
 535             return EINVAL;
 536         if ((fs->rdcl = cv4(bs->bpb.rdcl)) < LOCLUS)
 537             return EINVAL;
 538     }
 539     if (!(fs->lsnfat = cv2(bs->bpb.ressec)))
 540         return EINVAL;
 541     fs->lsndir = fs->lsnfat + fs->spf * bs->bpb.fats;
 542     fs->lsndta = fs->lsndir + entsec(fs->dirents);
 543     if (!(sc = cv2(bs->bpb.secs)) && !(sc = cv4(bs->bpb.lsecs)))
 544         return EINVAL;
 545     if (fs->lsndta > sc)
 546         return EINVAL;
 547     if ((fs->xclus = secblk(fs, sc - fs->lsndta) + 1) < LOCLUS)
 548         return EINVAL;
 549     fs->fatsz = fs->dirents ? fs->xclus < 0xff6 ? 12 : 16 : 32;
 550     sc = (secbyt(fs->spf) << 1) / (fs->fatsz >> 2) - 1;
 551     if (fs->xclus > sc)
 552         fs->xclus = sc;
 553     return 0;
 554 }
 555
 556 /*
 557  * Return directory entry from path
 558  */
 559 static int
 560 namede(DOS_FS *fs, const char *path, DOS_DE **dep)
 561 {
 562     char name[256];
 563     DOS_DE *de;
 564     char *s;
 565     size_t n;
 566     int err;
 567
 568     err = 0;
 569     de = &fs->root;
 570     while (*path) {
 571         while (*path == '/')
 572             path++;
 573         if (*path == '\0')
 574             break;
 575         if (!(s = strchr(path, '/')))
 576             s = strchr(path, 0);
 577         if ((n = s - path) > 255)
 578             return ENAMETOOLONG;
 579         memcpy(name, path, n);
 580         name[n] = 0;
 581         path = s;
 582         if (!(de->attr & FA_DIR))
 583             return ENOTDIR;
 584         if ((err = lookup(fs, stclus(fs->fatsz, de), name, &de)))
 585             return err;
 586     }
 587     *dep = de;
 588     return 0;
 589 }
 590
 591 /*
 592  * Lookup path segment
 593  */
 594 static int
 595 lookup(DOS_FS *fs, u_int clus, const char *name, DOS_DE **dep)
 596 {
 597     static DOS_DIR dir[DEPSEC];
 598     u_char lfn[261];
 599     u_char sfn[13];
 600     u_int nsec, lsec, xdn, chk, sec, ent, x;
 601     int err, ok;
 602
 603     if (!clus)
 604         for (ent = 0; ent < 2; ent++)
 605             if (!strcasecmp(name, dotstr[ent])) {
 606                 *dep = dot + ent;
 607                 return 0;
 608             }
 609     if (!clus && fs->fatsz == 32)
 610         clus = fs->rdcl;
 611     nsec = !clus ? entsec(fs->dirents) : fs->spc;
 612     lsec = 0;
 613     xdn = chk = 0;
 614     for (;;) {
 615         if (!clus && !lsec)
 616             lsec = fs->lsndir;
 617         else if (okclus(fs, clus))
 618             lsec = blklsn(fs, clus);
 619         else
 620             return EINVAL;
 621         for (sec = 0; sec < nsec; sec++) {
 622             if ((err = ioget(fs->fd, lsec + sec, 0, dir, secbyt(1))))
 623                 return err;
 624             for (ent = 0; ent < DEPSEC; ent++) {
 625                 if (!*dir[ent].de.name)
 626                     return ENOENT;
 627                 if (*dir[ent].de.name != 0xe5) {
 628                     if ((dir[ent].de.attr & FA_MASK) == FA_XDE) {
 629                         x = dir[ent].xde.seq;
 630                         if (x & 0x40 || (x + 1 == xdn &&
 631                                          dir[ent].xde.chk == chk)) {
 632                             if (x & 0x40) {
 633                                 chk = dir[ent].xde.chk;
 634                                 x &= ~0x40;
 635                             }
 636                             if (x >= 1 && x <= 20) {
 637                                 cp_xdnm(lfn, &dir[ent].xde);
 638                                 xdn = x;
 639                                 continue;
 640                             }
 641                         }
 642                     } else if (!(dir[ent].de.attr & FA_LABEL)) {
 643                         if ((ok = xdn == 1)) {
 644                             x = dos_checksum(dir[ent].de.name, dir[ent].de.ext);
 645                             ok = chk == x &&
 646                                 !strcasecmp(name, (const char *)lfn);
 647                         }
 648                         if (!ok) {
 649                             cp_sfn(sfn, &dir[ent].de);
 650                             ok = !strcasecmp(name, (const char *)sfn);
 651                         }
 652                         if (ok) {
 653                             *dep = &dir[ent].de;
 654                             return 0;
 655                         }
 656                     }
 657                 }
 658                 xdn = 0;
 659             }
 660         }
 661         if (!clus)
 662             break;
 663         if ((err = fatget(fs, &clus)))
 664             return err;
 665         if (fatend(fs->fatsz, clus))
 666             break;
 667     }
 668     return ENOENT;
 669 }
 670
 671 /*
 672  * Copy name from extended directory entry
 673  */
 674 static void
 675 cp_xdnm(u_char *lfn, DOS_XDE *xde)
 676 {
 677     static struct {
 678         u_int off;
 679         u_int dim;
 680     } ix[3] = {
 681         {offsetof(DOS_XDE, name1), sizeof(xde->name1) / 2},
 682         {offsetof(DOS_XDE, name2), sizeof(xde->name2) / 2},
 683         {offsetof(DOS_XDE, name3), sizeof(xde->name3) / 2}
 684     };
 685     u_char *p;
 686     u_int n, x, c;
 687
 688     lfn += 13 * ((xde->seq & ~0x40) - 1);
 689     for (n = 0; n < 3; n++)
 690         for (p = (u_char *)xde + ix[n].off, x = ix[n].dim; x;
 691              p += 2, x--) {
 692             if ((c = cv2(p)) && (c < 32 || c > 127))
 693                 c = '?';
 694             if (!(*lfn++ = c))
 695                 return;
 696         }
 697     if (xde->seq & 0x40)
 698         *lfn = 0;
 699 }
 700
 701 /*
 702  * Copy short filename
 703  */
 704 static void
 705 cp_sfn(u_char *sfn, DOS_DE *de)
 706 {
 707     u_char *p;
 708     int j, i;
 709
 710     p = sfn;
 711     if (*de->name != ' ') {
 712         for (j = 7; de->name[j] == ' '; j--);
 713         for (i = 0; i <= j; i++)
 714             *p++ = de->name[i];
 715         if (*de->ext != ' ') {
 716             *p++ = '.';
 717             for (j = 2; de->ext[j] == ' '; j--);
 718             for (i = 0; i <= j; i++)
 719                 *p++ = de->ext[i];
 720         }
 721     }
 722     *p = 0;
 723     if (*sfn == 5)
 724         *sfn = 0xe5;
 725 }
 726
 727 /*
 728  * Return size of file in bytes
 729  */
 730 static off_t
 731 fsize(DOS_FS *fs, DOS_DE *de)
 732 {
 733    u_long size;
 734    u_int c;
 735    int n;
 736
 737    if (!(size = cv4(de->size)) && de->attr & FA_DIR) {
 738       if (!(c = cv2(de->clus)))
 739          size = fs->dirents * sizeof(DOS_DE);
 740       else {
 741          if ((n = fatcnt(fs, c)) == -1)
 742             return n;
 743          size = blkbyt(fs, n);
 744       }
 745    }
 746    return size;
 747 }
 748
 749 /*
 750  * Count number of clusters in chain
 751  */
 752 static int
 753 fatcnt(DOS_FS *fs, u_int c)
 754 {
 755    int n;
 756
 757    for (n = 0; okclus(fs, c); n++)
 758       if (fatget(fs, &c))
 759           return -1;
 760    return fatend(fs->fatsz, c) ? n : -1;
 761 }
 762
 763 /*
 764  * Get next cluster in cluster chain. Use in core fat cache unless another
 765  * device replaced it.
 766  */
 767 static int
 768 fatget(DOS_FS *fs, u_int *c)
 769 {
 770     u_char buf[4];
 771     u_char *s;
 772     u_int x, offset, off, n, nbyte, lsec;
 773     struct devdesc *dd = fs->fd->f_devdata;
 774     int err = 0;
 775
 776     if (fat.unit != dd->d_unit) {
 777         /* fat cache was changed to another device, don't use it */
 778         err = ioread(fs, secbyt(fs->lsnfat) + fatoff(fs->fatsz, *c), buf,
 779             fs->fatsz != 32 ? 2 : 4);
 780         if (err)
 781             return (err);
 782     } else {
 783         offset = fatoff(fs->fatsz, *c);
 784         nbyte = fs->fatsz != 32 ? 2 : 4;
 785
 786         s = buf;
 787         if ((off = offset & (SECSIZ - 1))) {
 788             offset -= off;
 789             lsec = bytsec(offset);
 790             offset += SECSIZ;
 791             if ((n = SECSIZ - off) > nbyte)
 792                 n = nbyte;
 793             memcpy(s, fat.buf + secbyt(lsec) + off, n);
 794             s += n;
 795             nbyte -= n;
 796         }
 797         n = nbyte & (SECSIZ - 1);
 798         if (nbyte -= n) {
 799             memcpy(s, fat.buf + secbyt(bytsec(offset)), nbyte);
 800             offset += nbyte;
 801             s += nbyte;
 802         }
 803         if (n)
 804             memcpy(s, fat.buf + secbyt(bytsec(offset)), n);
 805     }
 806
 807     x = fs->fatsz != 32 ? cv2(buf) : cv4(buf);
 808     *c = fs->fatsz == 12 ? *c & 1 ? x >> 4 : x & 0xfff : x;
 809     return (0);
 810 }
 811
 812 /*
 813  * Is cluster an end-of-chain marker?
 814  */
 815 static int
 816 fatend(u_int sz, u_int c)
 817 {
 818     return c > (sz == 12 ? 0xff7U : sz == 16 ? 0xfff7U : 0xffffff7);
 819 }
 820
 821 /*
 822  * Offset-based I/O primitive
 823  */
 824 static int
 825 ioread(DOS_FS *fs, u_int offset, void *buf, u_int nbyte)
 826 {
 827     char *s;
 828     u_int off, n;
 829     int err;
 830
 831     s = buf;
 832     if ((off = offset & (SECSIZ - 1))) {
 833         offset -= off;
 834         if ((n = SECSIZ - off) > nbyte)
 835             n = nbyte;
 836         if ((err = ioget(fs->fd, bytsec(offset), off, s, n)))
 837             return err;
 838         offset += SECSIZ;
 839         s += n;
 840         nbyte -= n;
 841     }
 842     n = nbyte & (SECSIZ - 1);
 843     if (nbyte -= n) {
 844         if ((err = ioget(fs->fd, bytsec(offset), 0, s, nbyte)))
 845             return err;
 846         offset += nbyte;
 847         s += nbyte;
 848     }
 849     if (n) {
 850         if ((err = ioget(fs->fd, bytsec(offset), 0, s, n)))
 851             return err;
 852     }
 853     return 0;
 854 }
 855
 856 /*
 857  * Sector-based I/O primitive
 858  */
 859 static int
 860 ioget(struct open_file *fd, daddr_t lsec, size_t offset, void *buf, u_int size)
 861 {
 862     return ((fd->f_dev->dv_strategy)(fd->f_devdata, F_READ, lsec, offset,
 863         size, buf, NULL));
 864 }