dosfs.c revision 38451 
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/*
29 * Readonly filesystem for Microsoft FAT12/FAT16/FAT32 filesystems,
30 * also supports VFAT.
31 */
32
33#include <sys/types.h>
34#include <string.h>
35#include <stddef.h>
36
37#include "stand.h"
38
39#if 0
40#include <unistd.h>
41#include <fcntl.h>
42#include <stdlib.h>
43#include <stdio.h>
44#include <errno.h>
45#endif
46
47#include "dosfs.h"
48
49
50static int	dos_open(char *path, struct open_file *fd);
51static int	dos_close(struct open_file *fd);
52static int	dos_read(struct open_file *fd, void *buf, size_t size, size_t *resid);
53static off_t	dos_seek(struct open_file *fd, off_t offset, int whence);
54static int	dos_stat(struct open_file *fd, struct stat *sb);
55
56struct fs_ops dos_fsops = {
57    "dosfs", dos_open, dos_close, dos_read, null_write, dos_seek, dos_stat
58};
59
60#define SECSIZ  512             /* sector size */
61#define SSHIFT    9             /* SECSIZ shift */
62#define DEPSEC   16             /* directory entries per sector */
63#define DSHIFT    4             /* DEPSEC shift */
64#define LOCLUS    2             /* lowest cluster number */
65
66/* DOS "BIOS Parameter Block" */
67typedef struct {
68    u_char secsiz[2];           /* sector size */
69    u_char spc;                 /* sectors per cluster */
70    u_char ressec[2];           /* reserved sectors */
71    u_char fats;                /* FATs */
72    u_char dirents[2];          /* root directory entries */
73    u_char secs[2];             /* total sectors */
74    u_char media;               /* media descriptor */
75    u_char spf[2];              /* sectors per FAT */
76    u_char spt[2];              /* sectors per track */
77    u_char heads[2];            /* drive heads */
78    u_char hidsec[4];           /* hidden sectors */
79    u_char lsecs[4];            /* huge sectors */
80    u_char lspf[4];             /* huge sectors per FAT */
81    u_char xflg[2];             /* flags */
82    u_char vers[2];             /* filesystem version */
83    u_char rdcl[4];             /* root directory start cluster */
84    u_char infs[2];             /* filesystem info sector */
85    u_char bkbs[2];             /* backup boot sector */
86} DOS_BPB;
87
88/* Initial portion of DOS boot sector */
89typedef struct {
90    u_char jmp[3];              /* usually 80x86 'jmp' opcode */
91    u_char oem[8];              /* OEM name and version */
92    DOS_BPB bpb;                /* BPB */
93} DOS_BS;
94
95/* Supply missing "." and ".." root directory entries */
96static const char *const dotstr[2] = {".", ".."};
97static DOS_DE dot[2] = {
98    {".       ", "   ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
99     {0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}},
100    {"..      ", "   ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
101     {0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}}
102};
103
104/* The usual conversion macros to avoid multiplication and division */
105#define bytsec(n)      ((n) >> SSHIFT)
106#define secbyt(s)      ((s) << SSHIFT)
107#define entsec(e)      ((e) >> DSHIFT)
108#define bytblk(fs, n)  ((n) >> (fs)->bshift)
109#define blkbyt(fs, b)  ((b) << (fs)->bshift)
110#define secblk(fs, s)  ((s) >> ((fs)->bshift - SSHIFT))
111#define blksec(fs, b)  ((b) << ((fs)->bshift - SSHIFT))
112
113/* Convert cluster number to offset within filesystem */
114#define blkoff(fs, b) (secbyt((fs)->lsndta) + blkbyt(fs, (b) - LOCLUS))
115
116/* Convert cluster number to logical sector number */
117#define blklsn(fs, b)  ((fs)->lsndta + blksec(fs, (b) - LOCLUS))
118
119/* Convert cluster number to offset within FAT */
120#define fatoff(sz, c)  ((sz) == 12 ? (c) + ((c) >> 1) :  \
121                        (sz) == 16 ? (c) << 1 :          \
122			(c) << 2)
123
124/* Does cluster number reference a valid data cluster? */
125#define okclus(fs, c)  ((c) >= LOCLUS && (c) <= (fs)->xclus)
126
127/* Get start cluster from directory entry */
128#define stclus(sz, de)  ((sz) != 32 ? cv2((de)->clus) :          \
129                         ((u_int)cv2((de)->dex.h_clus) << 16) |  \
130			 cv2((de)->clus))
131
132static int dosunmount(DOS_FS *);
133static int parsebs(DOS_FS *, DOS_BS *);
134static int namede(DOS_FS *, const char *, DOS_DE **);
135static int lookup(DOS_FS *, u_int, const char *, DOS_DE **);
136static void cp_xdnm(u_char *, DOS_XDE *);
137static void cp_sfn(u_char *, DOS_DE *);
138static int fatget(DOS_FS *, u_int *);
139static int fatend(u_int, u_int);
140static int ioread(DOS_FS *, u_int, void *, u_int);
141static int iobuf(DOS_FS *, u_int);
142static int ioget(struct open_file *, u_int, void *, u_int);
143
144/*
145 * Mount DOS filesystem
146 */
147static int
148dos_mount(DOS_FS *fs, struct open_file *fd)
149{
150    int err;
151
152    bzero(fs, sizeof(DOS_FS));
153    fs->fd = fd;
154    if ((err = !(fs->buf = alloc(SECSIZ)) ? errno : 0) ||
155        (err = ioget(fs->fd, 0, fs->buf, 1)) ||
156        (err = parsebs(fs, (DOS_BS *)fs->buf))) {
157        (void)dosunmount(fs);
158        return(err);
159    }
160    return 0;
161}
162
163/*
164 * Unmount mounted filesystem
165 */
166static int
167dos_unmount(DOS_FS *fs)
168{
169    int err;
170
171    if (fs->links)
172        return(EBUSY);
173    if ((err = dosunmount(fs)))
174        return(err);
175    return 0;
176}
177
178/*
179 * Common code shared by dos_mount() and dos_unmount()
180 */
181static int
182dosunmount(DOS_FS *fs)
183{
184    if (fs->buf)
185        free(fs->buf, 0);
186    free(fs, 0);
187    return(0);
188}
189
190/*
191 * Open DOS file
192 */
193static int
194dos_open(char *path, struct open_file *fd)
195{
196    DOS_DE *de;
197    DOS_FILE *f;
198    DOS_FS *fs;
199    u_int size, clus;
200    int err = 0;
201
202    /* Allocate mount structure, associate with open */
203    fs = alloc(sizeof(DOS_FS));
204
205    if ((err = dos_mount(fs, fd)))
206	goto out;
207
208    if ((err = namede(fs, path, &de)))
209	goto out;
210
211    /* XXX we need to be able to open directories */
212    if (de->attr & FA_DIR) {
213        err = EISDIR;
214	goto out;
215    }
216    clus = stclus(fs->fatsz, de);
217    size = cv4(de->size);
218    if (!clus ^ !size || (clus && !okclus(fs, clus))) {
219        err = EINVAL;
220	goto out;
221    }
222    f = alloc(sizeof(DOS_FILE));
223    bzero(f, sizeof(DOS_FILE));
224    f->fs = fs;
225    fs->links++;
226    f->de = *de;
227    fd->f_fsdata = (void *)f;
228
229 out:
230    return(err);
231}
232
233/*
234 * Read from file
235 */
236static int
237dos_read(struct open_file *fd, void *buf, size_t nbyte, size_t *resid)
238{
239    u_int nb, off, clus, c, cnt, n;
240    DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
241    int err = 0;
242
243    nb = (u_int)nbyte;
244    if (nb > (n = cv4(f->de.size) - f->offset))
245        nb = n;
246    off = f->offset;
247    if ((clus = stclus(f->fs->fatsz, &f->de)))
248        off &= f->fs->bsize - 1;
249    c = f->c;
250    cnt = nb;
251    while (cnt) {
252        n = 0;
253        if (!c) {
254            if ((c = clus))
255                n = bytblk(f->fs, f->offset);
256        } else if (!off)
257            n++;
258        while (n--) {
259            if ((err = fatget(f->fs, &c)))
260		goto out;
261            if (!okclus(f->fs, c)) {
262		err = EINVAL;
263		goto out;
264	    }
265        }
266        if (!clus || (n = f->fs->bsize - off) > cnt)
267            n = cnt;
268        if ((err = ioread(f->fs, blkoff(f->fs, c) + off, buf, n)))
269	    goto out;
270        f->offset += n;
271        f->c = c;
272        off = 0;
273        buf += n;
274        cnt -= n;
275    }
276 out:
277    if (resid)
278	*resid = cnt;
279    return(err);
280}
281
282/*
283 * Reposition within file
284 */
285static off_t
286dos_seek(struct open_file *fd, off_t offset, int whence)
287{
288    off_t off;
289    u_int size;
290    DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
291
292    size = cv4(f->de.size);
293    switch (whence) {
294    case SEEK_SET:
295        off = 0;
296        break;
297    case SEEK_CUR:
298        off = f->offset;
299        break;
300    case SEEK_END:
301        off = size;
302        break;
303    default:
304	return(-1);
305    }
306    off += offset;
307    if (off < 0 || off > size)
308        return(-1);
309    f->offset = (u_int)off;
310    f->c = 0;
311    return(off);
312}
313
314/*
315 * Close open file
316 */
317static int
318dos_close(struct open_file *fd)
319{
320    DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
321    DOS_FS *fs = f->fs;
322
323    f->fs->links--;
324    free(f, 0);
325    dos_unmount(fs);
326    return 0;
327}
328
329/*
330 * Return some stat information on a file.
331 */
332static int
333dos_stat(struct open_file *fd, struct stat *sb)
334{
335    DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
336
337    /* only important stuff */
338    sb->st_mode = 0444;
339    sb->st_nlink = 1;
340    sb->st_uid = 0;
341    sb->st_gid = 0;
342    sb->st_size = cv4(f->de.size);
343    return (0);
344}
345
346/*
347 * Parse DOS boot sector
348 */
349static int
350parsebs(DOS_FS *fs, DOS_BS *bs)
351{
352    u_int sc;
353
354    if ((bs->jmp[0] != 0x69 &&
355         bs->jmp[0] != 0xe9 &&
356         (bs->jmp[0] != 0xeb || bs->jmp[2] != 0x90)) ||
357        bs->bpb.media < 0xf0)
358        return EINVAL;
359    if (cv2(bs->bpb.secsiz) != SECSIZ)
360        return EINVAL;
361    if (!(fs->spc = bs->bpb.spc) || fs->spc & (fs->spc - 1))
362        return EINVAL;
363    fs->bsize = secbyt(fs->spc);
364    fs->bshift = ffs(fs->bsize) - 1;
365    if ((fs->spf = cv2(bs->bpb.spf))) {
366        if (bs->bpb.fats != 2)
367            return EINVAL;
368        if (!(fs->dirents = cv2(bs->bpb.dirents)))
369            return EINVAL;
370    } else {
371        if (!(fs->spf = cv4(bs->bpb.lspf)))
372            return EINVAL;
373        if (!bs->bpb.fats || bs->bpb.fats > 16)
374            return EINVAL;
375        if ((fs->rdcl = cv4(bs->bpb.rdcl)) < LOCLUS)
376            return EINVAL;
377    }
378    if (!(fs->lsnfat = cv2(bs->bpb.ressec)))
379        return EINVAL;
380    fs->lsndir = fs->lsnfat + fs->spf * bs->bpb.fats;
381    fs->lsndta = fs->lsndir + entsec(fs->dirents);
382    if (!(sc = cv2(bs->bpb.secs)) && !(sc = cv4(bs->bpb.lsecs)))
383        return EINVAL;
384    if (fs->lsndta > sc)
385        return EINVAL;
386    if ((fs->xclus = secblk(fs, sc - fs->lsndta) + 1) < LOCLUS)
387        return EINVAL;
388    fs->fatsz = fs->dirents ? fs->xclus < 0xff6 ? 12 : 16 : 32;
389    sc = (secbyt(fs->spf) << 1) / (fs->fatsz >> 2) - 1;
390    if (fs->xclus > sc)
391        fs->xclus = sc;
392    return 0;
393}
394
395/*
396 * Return directory entry from path
397 */
398static int
399namede(DOS_FS *fs, const char *path, DOS_DE **dep)
400{
401    char name[256];
402    DOS_DE *de;
403    char *s;
404    size_t n;
405    int err;
406
407    err = 0;
408    de = dot;
409    if (*path == '/')
410        path++;
411    while (*path) {
412        if (!(s = strchr(path, '/')))
413            s = strchr(path, 0);
414        if ((n = s - path) > 255)
415            return ENAMETOOLONG;
416        memcpy(name, path, n);
417        name[n] = 0;
418        path = s;
419        if (!(de->attr & FA_DIR))
420            return ENOTDIR;
421        if ((err = lookup(fs, stclus(fs->fatsz, de), name, &de)))
422            return err;
423        if (*path == '/')
424            path++;
425    }
426    *dep = de;
427    return 0;
428}
429
430/*
431 * Lookup path segment
432 */
433static int
434lookup(DOS_FS *fs, u_int clus, const char *name, DOS_DE **dep)
435{
436    static DOS_DIR dir[DEPSEC];
437    u_char lfn[261];
438    u_char sfn[13];
439    u_int nsec, lsec, xdn, chk, sec, ent, x;
440    int err, ok, i;
441
442    if (!clus)
443        for (ent = 0; ent < 2; ent++)
444            if (!strcasecmp(name, dotstr[ent])) {
445                *dep = dot + ent;
446                return 0;
447            }
448    if (!clus && fs->fatsz == 32)
449        clus = fs->rdcl;
450    nsec = !clus ? entsec(fs->dirents) : fs->spc;
451    lsec = 0;
452    xdn = chk = 0;
453    for (;;) {
454        if (!clus && !lsec)
455            lsec = fs->lsndir;
456        else if (okclus(fs, clus))
457            lsec = blklsn(fs, clus);
458        else
459            return EINVAL;
460        for (sec = 0; sec < nsec; sec++) {
461            if ((err = ioget(fs->fd, lsec + sec, dir, 1)))
462                return err;
463            for (ent = 0; ent < DEPSEC; ent++) {
464                if (!*dir[ent].de.name)
465                    return ENOENT;
466                if (*dir[ent].de.name != 0xe5)
467                    if ((dir[ent].de.attr & FA_MASK) == FA_XDE) {
468                        x = dir[ent].xde.seq;
469                        if (x & 0x40 || (x + 1 == xdn &&
470                                         dir[ent].xde.chk == chk)) {
471                            if (x & 0x40) {
472                                chk = dir[ent].xde.chk;
473                                x &= ~0x40;
474                            }
475                            if (x >= 1 && x <= 20) {
476                                cp_xdnm(lfn, &dir[ent].xde);
477                                xdn = x;
478                                continue;
479                            }
480                        }
481                    } else if (!(dir[ent].de.attr & FA_LABEL)) {
482                        if ((ok = xdn == 1)) {
483                            for (x = 0, i = 0; i < 11; i++)
484                                x = ((((x & 1) << 7) | (x >> 1)) +
485                                     dir[ent].de.name[i]) & 0xff;
486                            ok = chk == x &&
487                                !strcasecmp(name, (const char *)lfn);
488                        }
489                        if (!ok) {
490                            cp_sfn(sfn, &dir[ent].de);
491                            ok = !strcasecmp(name, (const char *)sfn);
492                        }
493                        if (ok) {
494                            *dep = &dir[ent].de;
495                            return 0;
496                        }
497                    }
498                xdn = 0;
499            }
500        }
501        if (!clus)
502            break;
503        if ((err = fatget(fs, &clus)))
504            return err;
505        if (fatend(fs->fatsz, clus))
506            break;
507    }
508    return ENOENT;
509}
510
511/*
512 * Copy name from extended directory entry
513 */
514static void
515cp_xdnm(u_char *lfn, DOS_XDE *xde)
516{
517    static struct {
518        u_int off;
519        u_int dim;
520    } ix[3] = {
521        {offsetof(DOS_XDE, name1), sizeof(xde->name1) / 2},
522        {offsetof(DOS_XDE, name2), sizeof(xde->name2) / 2},
523        {offsetof(DOS_XDE, name3), sizeof(xde->name3) / 2}
524    };
525    u_char *p;
526    u_int n, x, c;
527
528    lfn += 13 * ((xde->seq & ~0x40) - 1);
529    for (n = 0; n < 3; n++)
530        for (p = (u_char *)xde + ix[n].off, x = ix[n].dim; x;
531	     p += 2, x--) {
532            if ((c = cv2(p)) && (c < 32 || c > 127))
533                c = '?';
534            if (!(*lfn++ = c))
535                return;
536        }
537    if (xde->seq & 0x40)
538        *lfn = 0;
539}
540
541/*
542 * Copy short filename
543 */
544static void
545cp_sfn(u_char *sfn, DOS_DE *de)
546{
547    u_char *p;
548    int j, i;
549
550    p = sfn;
551    if (*de->name != ' ') {
552        for (j = 7; de->name[j] == ' '; j--);
553        for (i = 0; i <= j; i++)
554            *p++ = de->name[i];
555        if (*de->ext != ' ') {
556            *p++ = '.';
557            for (j = 2; de->ext[j] == ' '; j--);
558            for (i = 0; i <= j; i++)
559                *p++ = de->ext[i];
560        }
561    }
562    *p = 0;
563    if (*sfn == 5)
564        *sfn = 0xe5;
565}
566
567/*
568 * Get next cluster in cluster chain
569 */
570static int
571fatget(DOS_FS *fs, u_int *c)
572{
573    u_char buf[4];
574    u_int x;
575    int err;
576
577    err = ioread(fs, secbyt(fs->lsnfat) + fatoff(fs->fatsz, *c), buf,
578                 fs->fatsz != 32 ? 2 : 4);
579    if (err)
580        return err;
581    x = fs->fatsz != 32 ? cv2(buf) : cv4(buf);
582    *c = fs->fatsz == 12 ? *c & 1 ? x >> 4 : x & 0xfff : x;
583    return 0;
584}
585
586/*
587 * Is cluster an end-of-chain marker?
588 */
589static int
590fatend(u_int sz, u_int c)
591{
592    return c > (sz == 12 ? 0xff7U : sz == 16 ? 0xfff7U : 0xffffff7);
593}
594
595/*
596 * Offset-based I/O primitive
597 */
598static int
599ioread(DOS_FS *fs, u_int offset, void *buf, u_int nbyte)
600{
601    char *s;
602    u_int off, n;
603    int err;
604
605    s = buf;
606    if ((off = offset & (SECSIZ - 1))) {
607        offset -= off;
608        if ((err = iobuf(fs, bytsec(offset))))
609            return err;
610        offset += SECSIZ;
611        if ((n = SECSIZ - off) > nbyte)
612            n = nbyte;
613        memcpy(s, fs->buf + off, n);
614        s += n;
615        nbyte -= n;
616    }
617    n = nbyte & (SECSIZ - 1);
618    if (nbyte -= n) {
619        if ((err = ioget(fs->fd, bytsec(offset), s, bytsec(nbyte))))
620            return err;
621        offset += nbyte;
622        s += nbyte;
623    }
624    if (n) {
625        if ((err = iobuf(fs, bytsec(offset))))
626            return err;
627        memcpy(s, fs->buf, n);
628    }
629    return 0;
630}
631
632/*
633 * Buffered sector-based I/O primitive
634 */
635static int
636iobuf(DOS_FS *fs, u_int lsec)
637{
638    int err;
639
640    if (fs->bufsec != lsec) {
641        if ((err = ioget(fs->fd, lsec, fs->buf, 1)))
642            return err;
643        fs->bufsec = lsec;
644    }
645    return 0;
646}
647
648/*
649 * Sector-based I/O primitive
650 */
651static int
652ioget(struct open_file *fd, u_int lsec, void *buf, u_int nsec)
653{
654    int	err;
655
656    if ((err = (fd->f_dev->dv_strategy)(fd->f_devdata, F_READ, lsec,
657					secbyt(nsec), buf, NULL)))
658	return(err);
659    return(0);
660}
661