2 * Copyright (c) 1996, 1998 Robert Nordier
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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
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.
27 * $FreeBSD: src/lib/libstand/dosfs.c,v 1.4.2.1 2000/05/04 13:47:49 ps Exp $
31 * Readonly filesystem for Microsoft FAT12/FAT16/FAT32 filesystems,
35 #include <sys/types.h>
44 static int dos_open(const char *path, struct open_file *fd);
45 static int dos_close(struct open_file *fd);
46 static int dos_read(struct open_file *fd, void *buf, size_t size, size_t *resid);
47 static off_t dos_seek(struct open_file *fd, off_t offset, int whence);
48 static int dos_stat(struct open_file *fd, struct stat *sb);
50 struct fs_ops dosfs_fsops = {
61 #define SECSIZ 512 /* sector size */
62 #define SSHIFT 9 /* SECSIZ shift */
63 #define DEPSEC 16 /* directory entries per sector */
64 #define DSHIFT 4 /* DEPSEC shift */
65 #define LOCLUS 2 /* lowest cluster number */
67 /* DOS "BIOS Parameter Block" */
69 u_char secsiz[2]; /* sector size */
70 u_char spc; /* sectors per cluster */
71 u_char ressec[2]; /* reserved sectors */
72 u_char fats; /* FATs */
73 u_char dirents[2]; /* root directory entries */
74 u_char secs[2]; /* total sectors */
75 u_char media; /* media descriptor */
76 u_char spf[2]; /* sectors per FAT */
77 u_char spt[2]; /* sectors per track */
78 u_char heads[2]; /* drive heads */
79 u_char hidsec[4]; /* hidden sectors */
80 u_char lsecs[4]; /* huge sectors */
81 u_char lspf[4]; /* huge sectors per FAT */
82 u_char xflg[2]; /* flags */
83 u_char vers[2]; /* filesystem version */
84 u_char rdcl[4]; /* root directory start cluster */
85 u_char infs[2]; /* filesystem info sector */
86 u_char bkbs[2]; /* backup boot sector */
89 /* Initial portion of DOS boot sector */
91 u_char jmp[3]; /* usually 80x86 'jmp' opcode */
92 u_char oem[8]; /* OEM name and version */
93 DOS_BPB bpb; /* BPB */
96 /* Supply missing "." and ".." root directory entries */
97 static const char *const dotstr[2] = {".", ".."};
98 static DOS_DE dot[2] = {
99 {". ", " ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
100 {0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}},
101 {".. ", " ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
102 {0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}}
105 /* The usual conversion macros to avoid multiplication and division */
106 #define bytsec(n) ((n) >> SSHIFT)
107 #define secbyt(s) ((s) << SSHIFT)
108 #define entsec(e) ((e) >> DSHIFT)
109 #define bytblk(fs, n) ((n) >> (fs)->bshift)
110 #define blkbyt(fs, b) ((b) << (fs)->bshift)
111 #define secblk(fs, s) ((s) >> ((fs)->bshift - SSHIFT))
112 #define blksec(fs, b) ((b) << ((fs)->bshift - SSHIFT))
114 /* Convert cluster number to offset within filesystem */
115 #define blkoff(fs, b) (secbyt((fs)->lsndta) + blkbyt(fs, (b) - LOCLUS))
117 /* Convert cluster number to logical sector number */
118 #define blklsn(fs, b) ((fs)->lsndta + blksec(fs, (b) - LOCLUS))
120 /* Convert cluster number to offset within FAT */
121 #define fatoff(sz, c) ((sz) == 12 ? (c) + ((c) >> 1) : \
122 (sz) == 16 ? (c) << 1 : \
125 /* Does cluster number reference a valid data cluster? */
126 #define okclus(fs, c) ((c) >= LOCLUS && (c) <= (fs)->xclus)
128 /* Get start cluster from directory entry */
129 #define stclus(sz, de) ((sz) != 32 ? cv2((de)->clus) : \
130 ((u_int)cv2((de)->dex.h_clus) << 16) | \
133 static int dosunmount(DOS_FS *);
134 static int parsebs(DOS_FS *, DOS_BS *);
135 static int namede(DOS_FS *, const char *, DOS_DE **);
136 static int lookup(DOS_FS *, u_int, const char *, DOS_DE **);
137 static void cp_xdnm(u_char *, DOS_XDE *);
138 static void cp_sfn(u_char *, DOS_DE *);
139 static off_t fsize(DOS_FS *, DOS_DE *);
140 static int fatcnt(DOS_FS *, u_int);
141 static int fatget(DOS_FS *, u_int *);
142 static int fatend(u_int, u_int);
143 static int ioread(DOS_FS *, u_int, void *, u_int);
144 static int iobuf(DOS_FS *, u_int);
145 static int ioget(struct open_file *, u_int, void *, u_int);
148 * Mount DOS filesystem
151 dos_mount(DOS_FS *fs, struct open_file *fd)
155 bzero(fs, sizeof(DOS_FS));
157 if ((err = !(fs->buf = malloc(SECSIZ)) ? errno : 0) ||
158 (err = ioget(fs->fd, 0, fs->buf, 1)) ||
159 (err = parsebs(fs, (DOS_BS *)fs->buf))) {
160 (void)dosunmount(fs);
167 * Unmount mounted filesystem
170 dos_unmount(DOS_FS *fs)
176 if ((err = dosunmount(fs)))
182 * Common code shared by dos_mount() and dos_unmount()
185 dosunmount(DOS_FS *fs)
197 dos_open(const char *path, struct open_file *fd)
205 /* Allocate mount structure, associate with open */
206 fs = malloc(sizeof(DOS_FS));
208 if ((err = dos_mount(fs, fd)))
211 if ((err = namede(fs, path, &de)))
214 clus = stclus(fs->fatsz, de);
215 size = cv4(de->size);
217 if ((!(de->attr & FA_DIR) && (!clus != !size)) ||
218 ((de->attr & FA_DIR) && size) ||
219 (clus && !okclus(fs, clus))) {
223 f = malloc(sizeof(DOS_FILE));
224 bzero(f, sizeof(DOS_FILE));
228 fd->f_fsdata = (void *)f;
238 dos_read(struct open_file *fd, void *buf, size_t nbyte, size_t *resid)
241 u_int nb, off, clus, c, cnt, n;
242 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
246 if ((size = fsize(f->fs, &f->de)) == -1)
248 if (nb > (n = size - f->offset))
251 if ((clus = stclus(f->fs->fatsz, &f->de)))
252 off &= f->fs->bsize - 1;
259 n = bytblk(f->fs, f->offset);
263 if ((err = fatget(f->fs, &c)))
265 if (!okclus(f->fs, c)) {
270 if (!clus || (n = f->fs->bsize - off) > cnt)
272 if ((err = ioread(f->fs, (c ? blkoff(f->fs, c) :
273 secbyt(f->fs->lsndir)) + off,
284 *resid = nbyte - nb + cnt;
289 * Reposition within file
292 dos_seek(struct open_file *fd, off_t offset, int whence)
296 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
298 size = cv4(f->de.size);
313 if (off < 0 || off > size)
315 f->offset = (u_int)off;
324 dos_close(struct open_file *fd)
326 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
336 * Return some stat information on a file.
339 dos_stat(struct open_file *fd, struct stat *sb)
341 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
343 /* only important stuff */
344 sb->st_mode = f->de.attr & FA_DIR ? S_IFDIR | 0555 : S_IFREG | 0444;
348 if ((sb->st_size = fsize(f->fs, &f->de)) == -1)
354 * Parse DOS boot sector
357 parsebs(DOS_FS *fs, DOS_BS *bs)
361 if ((bs->jmp[0] != 0x69 &&
362 bs->jmp[0] != 0xe9 &&
363 (bs->jmp[0] != 0xeb || bs->jmp[2] != 0x90)) ||
364 bs->bpb.media < 0xf0)
366 if (cv2(bs->bpb.secsiz) != SECSIZ)
368 if (!(fs->spc = bs->bpb.spc) || fs->spc & (fs->spc - 1))
370 fs->bsize = secbyt(fs->spc);
371 fs->bshift = ffs(fs->bsize) - 1;
372 if ((fs->spf = cv2(bs->bpb.spf))) {
373 if (bs->bpb.fats != 2)
375 if (!(fs->dirents = cv2(bs->bpb.dirents)))
378 if (!(fs->spf = cv4(bs->bpb.lspf)))
380 if (!bs->bpb.fats || bs->bpb.fats > 16)
382 if ((fs->rdcl = cv4(bs->bpb.rdcl)) < LOCLUS)
385 if (!(fs->lsnfat = cv2(bs->bpb.ressec)))
387 fs->lsndir = fs->lsnfat + fs->spf * bs->bpb.fats;
388 fs->lsndta = fs->lsndir + entsec(fs->dirents);
389 if (!(sc = cv2(bs->bpb.secs)) && !(sc = cv4(bs->bpb.lsecs)))
393 if ((fs->xclus = secblk(fs, sc - fs->lsndta) + 1) < LOCLUS)
395 fs->fatsz = fs->dirents ? fs->xclus < 0xff6 ? 12 : 16 : 32;
396 sc = (secbyt(fs->spf) << 1) / (fs->fatsz >> 2) - 1;
403 * Return directory entry from path
406 namede(DOS_FS *fs, const char *path, DOS_DE **dep)
419 if (!(s = strchr(path, '/')))
421 if ((n = s - path) > 255)
423 memcpy(name, path, n);
426 if (!(de->attr & FA_DIR))
428 if ((err = lookup(fs, stclus(fs->fatsz, de), name, &de)))
438 * Lookup path segment
441 lookup(DOS_FS *fs, u_int clus, const char *name, DOS_DE **dep)
443 static DOS_DIR dir[DEPSEC];
446 u_int nsec, lsec, xdn, chk, sec, ent, x;
450 for (ent = 0; ent < 2; ent++)
451 if (!strcasecmp(name, dotstr[ent])) {
455 if (!clus && fs->fatsz == 32)
457 nsec = !clus ? entsec(fs->dirents) : fs->spc;
463 else if (okclus(fs, clus))
464 lsec = blklsn(fs, clus);
467 for (sec = 0; sec < nsec; sec++) {
468 if ((err = ioget(fs->fd, lsec + sec, dir, 1)))
470 for (ent = 0; ent < DEPSEC; ent++) {
471 if (!*dir[ent].de.name)
473 if (*dir[ent].de.name != 0xe5) {
474 if ((dir[ent].de.attr & FA_MASK) == FA_XDE) {
475 x = dir[ent].xde.seq;
476 if (x & 0x40 || (x + 1 == xdn &&
477 dir[ent].xde.chk == chk)) {
479 chk = dir[ent].xde.chk;
482 if (x >= 1 && x <= 20) {
483 cp_xdnm(lfn, &dir[ent].xde);
488 } else if (!(dir[ent].de.attr & FA_LABEL)) {
489 if ((ok = xdn == 1)) {
490 for (x = 0, i = 0; i < 11; i++)
491 x = ((((x & 1) << 7) | (x >> 1)) +
492 dir[ent].de.name[i]) & 0xff;
494 !strcasecmp(name, (const char *)lfn);
497 cp_sfn(sfn, &dir[ent].de);
498 ok = !strcasecmp(name, (const char *)sfn);
511 if ((err = fatget(fs, &clus)))
513 if (fatend(fs->fatsz, clus))
520 * Copy name from extended directory entry
523 cp_xdnm(u_char *lfn, DOS_XDE *xde)
529 {offsetof(DOS_XDE, name1), sizeof(xde->name1) / 2},
530 {offsetof(DOS_XDE, name2), sizeof(xde->name2) / 2},
531 {offsetof(DOS_XDE, name3), sizeof(xde->name3) / 2}
536 lfn += 13 * ((xde->seq & ~0x40) - 1);
537 for (n = 0; n < 3; n++)
538 for (p = (u_char *)xde + ix[n].off, x = ix[n].dim; x;
540 if ((c = cv2(p)) && (c < 32 || c > 127))
550 * Copy short filename
553 cp_sfn(u_char *sfn, DOS_DE *de)
559 if (*de->name != ' ') {
560 for (j = 7; de->name[j] == ' '; j--);
561 for (i = 0; i <= j; i++)
563 if (*de->ext != ' ') {
565 for (j = 2; de->ext[j] == ' '; j--);
566 for (i = 0; i <= j; i++)
576 * Return size of file in bytes
579 fsize(DOS_FS *fs, DOS_DE *de)
585 if (!(size = cv4(de->size)) && de->attr & FA_DIR) {
586 if (!(c = cv2(de->clus)))
587 size = fs->dirents * sizeof(DOS_DE);
589 if ((n = fatcnt(fs, c)) == -1)
591 size = blkbyt(fs, n);
598 * Count number of clusters in chain
601 fatcnt(DOS_FS *fs, u_int c)
605 for (n = 0; okclus(fs, c); n++)
608 return fatend(fs->fatsz, c) ? n : -1;
612 * Get next cluster in cluster chain
615 fatget(DOS_FS *fs, u_int *c)
621 err = ioread(fs, secbyt(fs->lsnfat) + fatoff(fs->fatsz, *c), buf,
622 fs->fatsz != 32 ? 2 : 4);
625 x = fs->fatsz != 32 ? cv2(buf) : cv4(buf);
626 *c = fs->fatsz == 12 ? *c & 1 ? x >> 4 : x & 0xfff : x;
631 * Is cluster an end-of-chain marker?
634 fatend(u_int sz, u_int c)
636 return c > (sz == 12 ? 0xff7U : sz == 16 ? 0xfff7U : 0xffffff7);
640 * Offset-based I/O primitive
643 ioread(DOS_FS *fs, u_int offset, void *buf, u_int nbyte)
650 if ((off = offset & (SECSIZ - 1))) {
652 if ((err = iobuf(fs, bytsec(offset))))
655 if ((n = SECSIZ - off) > nbyte)
657 memcpy(s, fs->buf + off, n);
661 n = nbyte & (SECSIZ - 1);
663 if ((err = ioget(fs->fd, bytsec(offset), s, bytsec(nbyte))))
669 if ((err = iobuf(fs, bytsec(offset))))
671 memcpy(s, fs->buf, n);
677 * Buffered sector-based I/O primitive
680 iobuf(DOS_FS *fs, u_int lsec)
684 if (fs->bufsec != lsec) {
685 if ((err = ioget(fs->fd, lsec, fs->buf, 1)))
693 * Sector-based I/O primitive
696 ioget(struct open_file *fd, u_int lsec, void *buf, u_int nsec)
700 if ((err = (fd->f_dev->dv_strategy)(fd->f_devdata, F_READ, lsec,
701 secbyt(nsec), buf, NULL)))