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freebsd-dev/lib/libstand/dosfs.c
Mike Smith 40fd46f77d Enable the DOS filesystem. This allows reading from various DOS filesystems 
(FAT12/16/32, VFAT).

Make a private copy of strcasecmp, as the "real" one uses the system ctype
header, which introduces locale poisoning.
1998-10-06 19:23:57 +00:00

694 lines
18 KiB
C
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/*
* Copyright (c) 1996, 1998 Robert Nordier
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
* IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
* IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Readonly filesystem for Microsoft FAT12/FAT16/FAT32 filesystems,
* also supports VFAT.
*/
#include <sys/types.h>
#include <string.h>
#include <stddef.h>
#include "stand.h"
#include "dosfs.h"
static int dos_open(const char *path, struct open_file *fd);
static int dos_close(struct open_file *fd);
static int dos_read(struct open_file *fd, void *buf, size_t size, size_t *resid);
static off_t dos_seek(struct open_file *fd, off_t offset, int whence);
static int dos_stat(struct open_file *fd, struct stat *sb);
struct fs_ops dosfs_fsops = {
"dosfs", dos_open, dos_close, dos_read, null_write, dos_seek, dos_stat
};
#define SECSIZ 512 /* sector size */
#define SSHIFT 9 /* SECSIZ shift */
#define DEPSEC 16 /* directory entries per sector */
#define DSHIFT 4 /* DEPSEC shift */
#define LOCLUS 2 /* lowest cluster number */
/* DOS "BIOS Parameter Block" */
typedef struct {
u_char secsiz[2]; /* sector size */
u_char spc; /* sectors per cluster */
u_char ressec[2]; /* reserved sectors */
u_char fats; /* FATs */
u_char dirents[2]; /* root directory entries */
u_char secs[2]; /* total sectors */
u_char media; /* media descriptor */
u_char spf[2]; /* sectors per FAT */
u_char spt[2]; /* sectors per track */
u_char heads[2]; /* drive heads */
u_char hidsec[4]; /* hidden sectors */
u_char lsecs[4]; /* huge sectors */
u_char lspf[4]; /* huge sectors per FAT */
u_char xflg[2]; /* flags */
u_char vers[2]; /* filesystem version */
u_char rdcl[4]; /* root directory start cluster */
u_char infs[2]; /* filesystem info sector */
u_char bkbs[2]; /* backup boot sector */
} DOS_BPB;
/* Initial portion of DOS boot sector */
typedef struct {
u_char jmp[3]; /* usually 80x86 'jmp' opcode */
u_char oem[8]; /* OEM name and version */
DOS_BPB bpb; /* BPB */
} DOS_BS;
/* Supply missing "." and ".." root directory entries */
static const char *const dotstr[2] = {".", ".."};
static DOS_DE dot[2] = {
{". ", " ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
{0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}},
{".. ", " ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
{0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}}
};
/* The usual conversion macros to avoid multiplication and division */
#define bytsec(n) ((n) >> SSHIFT)
#define secbyt(s) ((s) << SSHIFT)
#define entsec(e) ((e) >> DSHIFT)
#define bytblk(fs, n) ((n) >> (fs)->bshift)
#define blkbyt(fs, b) ((b) << (fs)->bshift)
#define secblk(fs, s) ((s) >> ((fs)->bshift - SSHIFT))
#define blksec(fs, b) ((b) << ((fs)->bshift - SSHIFT))
/* Convert cluster number to offset within filesystem */
#define blkoff(fs, b) (secbyt((fs)->lsndta) + blkbyt(fs, (b) - LOCLUS))
/* Convert cluster number to logical sector number */
#define blklsn(fs, b) ((fs)->lsndta + blksec(fs, (b) - LOCLUS))
/* Convert cluster number to offset within FAT */
#define fatoff(sz, c) ((sz) == 12 ? (c) + ((c) >> 1) : \
(sz) == 16 ? (c) << 1 : \
(c) << 2)
/* Does cluster number reference a valid data cluster? */
#define okclus(fs, c) ((c) >= LOCLUS && (c) <= (fs)->xclus)
/* Get start cluster from directory entry */
#define stclus(sz, de) ((sz) != 32 ? cv2((de)->clus) : \
((u_int)cv2((de)->dex.h_clus) << 16) | \
cv2((de)->clus))
static int dosunmount(DOS_FS *);
static int parsebs(DOS_FS *, DOS_BS *);
static int namede(DOS_FS *, const char *, DOS_DE **);
static int lookup(DOS_FS *, u_int, const char *, DOS_DE **);
static void cp_xdnm(u_char *, DOS_XDE *);
static void cp_sfn(u_char *, DOS_DE *);
static off_t fsize(DOS_FS *, DOS_DE *);
static int fatcnt(DOS_FS *, u_int);
static int fatget(DOS_FS *, u_int *);
static int fatend(u_int, u_int);
static int ioread(DOS_FS *, u_int, void *, u_int);
static int iobuf(DOS_FS *, u_int);
static int ioget(struct open_file *, u_int, void *, u_int);
/*
* Mount DOS filesystem
*/
static int
dos_mount(DOS_FS *fs, struct open_file *fd)
{
int err;
bzero(fs, sizeof(DOS_FS));
fs->fd = fd;
if ((err = !(fs->buf = malloc(SECSIZ)) ? errno : 0) ||
(err = ioget(fs->fd, 0, fs->buf, 1)) ||
(err = parsebs(fs, (DOS_BS *)fs->buf))) {
(void)dosunmount(fs);
return(err);
}
return 0;
}
/*
* Unmount mounted filesystem
*/
static int
dos_unmount(DOS_FS *fs)
{
int err;
if (fs->links)
return(EBUSY);
if ((err = dosunmount(fs)))
return(err);
return 0;
}
/*
* Common code shared by dos_mount() and dos_unmount()
*/
static int
dosunmount(DOS_FS *fs)
{
if (fs->buf)
free(fs->buf);
free(fs);
return(0);
}
/*
* Open DOS file
*/
static int
dos_open(const char *path, struct open_file *fd)
{
DOS_DE *de;
DOS_FILE *f;
DOS_FS *fs;
u_int size, clus;
int err = 0;
/* Allocate mount structure, associate with open */
fs = malloc(sizeof(DOS_FS));
if ((err = dos_mount(fs, fd)))
goto out;
if ((err = namede(fs, path, &de)))
goto out;
clus = stclus(fs->fatsz, de);
size = cv4(de->size);
if ((!(de->attr & FA_DIR) && (!clus != !size)) ||
((de->attr & FA_DIR) && size) ||
(clus && !okclus(fs, clus))) {
err = EINVAL;
goto out;
}
f = malloc(sizeof(DOS_FILE));
bzero(f, sizeof(DOS_FILE));
f->fs = fs;
fs->links++;
f->de = *de;
fd->f_fsdata = (void *)f;
out:
return(err);
}
/*
* Read from file
*/
static int
dos_read(struct open_file *fd, void *buf, size_t nbyte, size_t *resid)
{
off_t size;
u_int nb, off, clus, c, cnt, n;
DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
int err = 0;
nb = (u_int)nbyte;
if ((size = fsize(f->fs, &f->de)) == -1)
return EINVAL;
if (nb > (n = size - f->offset))
nb = n;
off = f->offset;
if ((clus = stclus(f->fs->fatsz, &f->de)))
off &= f->fs->bsize - 1;
c = f->c;
cnt = nb;
while (cnt) {
n = 0;
if (!c) {
if ((c = clus))
n = bytblk(f->fs, f->offset);
} else if (!off)
n++;
while (n--) {
if ((err = fatget(f->fs, &c)))
goto out;
if (!okclus(f->fs, c)) {
err = EINVAL;
goto out;
}
}
if (!clus || (n = f->fs->bsize - off) > cnt)
n = cnt;
if ((err = ioread(f->fs, (c ? blkoff(f->fs, c) :
secbyt(f->fs->lsndir)) + off,
buf, n)))
goto out;
f->offset += n;
f->c = c;
off = 0;
buf += n;
cnt -= n;
}
out:
if (resid)
*resid = nbyte - nb + cnt;
return(err);
}
/*
* Reposition within file
*/
static off_t
dos_seek(struct open_file *fd, off_t offset, int whence)
{
off_t off;
u_int size;
DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
size = cv4(f->de.size);
switch (whence) {
case SEEK_SET:
off = 0;
break;
case SEEK_CUR:
off = f->offset;
break;
case SEEK_END:
off = size;
break;
default:
return(-1);
}
off += offset;
if (off < 0 || off > size)
return(-1);
f->offset = (u_int)off;
f->c = 0;
return(off);
}
/*
* Close open file
*/
static int
dos_close(struct open_file *fd)
{
DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
DOS_FS *fs = f->fs;
f->fs->links--;
free(f);
dos_unmount(fs);
return 0;
}
/*
* Return some stat information on a file.
*/
static int
dos_stat(struct open_file *fd, struct stat *sb)
{
DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
/* only important stuff */
sb->st_mode = f->de.attr & FA_DIR ? S_IFDIR | 0555 : S_IFREG | 0444;
sb->st_nlink = 1;
sb->st_uid = 0;
sb->st_gid = 0;
if ((sb->st_size = fsize(f->fs, &f->de)) == -1)
return EINVAL;
return (0);
}
/*
* Parse DOS boot sector
*/
static int
parsebs(DOS_FS *fs, DOS_BS *bs)
{
u_int sc;
if ((bs->jmp[0] != 0x69 &&
bs->jmp[0] != 0xe9 &&
(bs->jmp[0] != 0xeb || bs->jmp[2] != 0x90)) ||
bs->bpb.media < 0xf0)
return EINVAL;
if (cv2(bs->bpb.secsiz) != SECSIZ)
return EINVAL;
if (!(fs->spc = bs->bpb.spc) || fs->spc & (fs->spc - 1))
return EINVAL;
fs->bsize = secbyt(fs->spc);
fs->bshift = ffs(fs->bsize) - 1;
if ((fs->spf = cv2(bs->bpb.spf))) {
if (bs->bpb.fats != 2)
return EINVAL;
if (!(fs->dirents = cv2(bs->bpb.dirents)))
return EINVAL;
} else {
if (!(fs->spf = cv4(bs->bpb.lspf)))
return EINVAL;
if (!bs->bpb.fats || bs->bpb.fats > 16)
return EINVAL;
if ((fs->rdcl = cv4(bs->bpb.rdcl)) < LOCLUS)
return EINVAL;
}
if (!(fs->lsnfat = cv2(bs->bpb.ressec)))
return EINVAL;
fs->lsndir = fs->lsnfat + fs->spf * bs->bpb.fats;
fs->lsndta = fs->lsndir + entsec(fs->dirents);
if (!(sc = cv2(bs->bpb.secs)) && !(sc = cv4(bs->bpb.lsecs)))
return EINVAL;
if (fs->lsndta > sc)
return EINVAL;
if ((fs->xclus = secblk(fs, sc - fs->lsndta) + 1) < LOCLUS)
return EINVAL;
fs->fatsz = fs->dirents ? fs->xclus < 0xff6 ? 12 : 16 : 32;
sc = (secbyt(fs->spf) << 1) / (fs->fatsz >> 2) - 1;
if (fs->xclus > sc)
fs->xclus = sc;
return 0;
}
/*
* Return directory entry from path
*/
static int
namede(DOS_FS *fs, const char *path, DOS_DE **dep)
{
char name[256];
DOS_DE *de;
char *s;
size_t n;
int err;
err = 0;
de = dot;
if (*path == '/')
path++;
while (*path) {
if (!(s = strchr(path, '/')))
s = strchr(path, 0);
if ((n = s - path) > 255)
return ENAMETOOLONG;
memcpy(name, path, n);
name[n] = 0;
path = s;
if (!(de->attr & FA_DIR))
return ENOTDIR;
if ((err = lookup(fs, stclus(fs->fatsz, de), name, &de)))
return err;
if (*path == '/')
path++;
}
*dep = de;
return 0;
}
/*
* Lookup path segment
*/
static int
lookup(DOS_FS *fs, u_int clus, const char *name, DOS_DE **dep)
{
static DOS_DIR dir[DEPSEC];
u_char lfn[261];
u_char sfn[13];
u_int nsec, lsec, xdn, chk, sec, ent, x;
int err, ok, i;
if (!clus)
for (ent = 0; ent < 2; ent++)
if (!strcasecmp(name, dotstr[ent])) {
*dep = dot + ent;
return 0;
}
if (!clus && fs->fatsz == 32)
clus = fs->rdcl;
nsec = !clus ? entsec(fs->dirents) : fs->spc;
lsec = 0;
xdn = chk = 0;
for (;;) {
if (!clus && !lsec)
lsec = fs->lsndir;
else if (okclus(fs, clus))
lsec = blklsn(fs, clus);
else
return EINVAL;
for (sec = 0; sec < nsec; sec++) {
if ((err = ioget(fs->fd, lsec + sec, dir, 1)))
return err;
for (ent = 0; ent < DEPSEC; ent++) {
if (!*dir[ent].de.name)
return ENOENT;
if (*dir[ent].de.name != 0xe5)
if ((dir[ent].de.attr & FA_MASK) == FA_XDE) {
x = dir[ent].xde.seq;
if (x & 0x40 || (x + 1 == xdn &&
dir[ent].xde.chk == chk)) {
if (x & 0x40) {
chk = dir[ent].xde.chk;
x &= ~0x40;
}
if (x >= 1 && x <= 20) {
cp_xdnm(lfn, &dir[ent].xde);
xdn = x;
continue;
}
}
} else if (!(dir[ent].de.attr & FA_LABEL)) {
if ((ok = xdn == 1)) {
for (x = 0, i = 0; i < 11; i++)
x = ((((x & 1) << 7) | (x >> 1)) +
dir[ent].de.name[i]) & 0xff;
ok = chk == x &&
!strcasecmp(name, (const char *)lfn);
}
if (!ok) {
cp_sfn(sfn, &dir[ent].de);
ok = !strcasecmp(name, (const char *)sfn);
}
if (ok) {
*dep = &dir[ent].de;
return 0;
}
}
xdn = 0;
}
}
if (!clus)
break;
if ((err = fatget(fs, &clus)))
return err;
if (fatend(fs->fatsz, clus))
break;
}
return ENOENT;
}
/*
* Copy name from extended directory entry
*/
static void
cp_xdnm(u_char *lfn, DOS_XDE *xde)
{
static struct {
u_int off;
u_int dim;
} ix[3] = {
{offsetof(DOS_XDE, name1), sizeof(xde->name1) / 2},
{offsetof(DOS_XDE, name2), sizeof(xde->name2) / 2},
{offsetof(DOS_XDE, name3), sizeof(xde->name3) / 2}
};
u_char *p;
u_int n, x, c;
lfn += 13 * ((xde->seq & ~0x40) - 1);
for (n = 0; n < 3; n++)
for (p = (u_char *)xde + ix[n].off, x = ix[n].dim; x;
p += 2, x--) {
if ((c = cv2(p)) && (c < 32 || c > 127))
c = '?';
if (!(*lfn++ = c))
return;
}
if (xde->seq & 0x40)
*lfn = 0;
}
/*
* Copy short filename
*/
static void
cp_sfn(u_char *sfn, DOS_DE *de)
{
u_char *p;
int j, i;
p = sfn;
if (*de->name != ' ') {
for (j = 7; de->name[j] == ' '; j--);
for (i = 0; i <= j; i++)
*p++ = de->name[i];
if (*de->ext != ' ') {
*p++ = '.';
for (j = 2; de->ext[j] == ' '; j--);
for (i = 0; i <= j; i++)
*p++ = de->ext[i];
}
}
*p = 0;
if (*sfn == 5)
*sfn = 0xe5;
}
/*
* Return size of file in bytes
*/
static off_t
fsize(DOS_FS *fs, DOS_DE *de)
{
u_long size;
u_int c;
int n;
if (!(size = cv4(de->size)) && de->attr & FA_DIR)
if (!(c = cv2(de->clus)))
size = fs->dirents * sizeof(DOS_DE);
else {
if ((n = fatcnt(fs, c)) == -1)
return n;
size = blkbyt(fs, n);
}
return size;
}
/*
* Count number of clusters in chain
*/
static int
fatcnt(DOS_FS *fs, u_int c)
{
int n;
for (n = 0; okclus(fs, c); n++)
if (fatget(fs, &c))
return -1;
return fatend(fs->fatsz, c) ? n : -1;
}
/*
* Get next cluster in cluster chain
*/
static int
fatget(DOS_FS *fs, u_int *c)
{
u_char buf[4];
u_int x;
int err;
err = ioread(fs, secbyt(fs->lsnfat) + fatoff(fs->fatsz, *c), buf,
fs->fatsz != 32 ? 2 : 4);
if (err)
return err;
x = fs->fatsz != 32 ? cv2(buf) : cv4(buf);
*c = fs->fatsz == 12 ? *c & 1 ? x >> 4 : x & 0xfff : x;
return 0;
}
/*
* Is cluster an end-of-chain marker?
*/
static int
fatend(u_int sz, u_int c)
{
return c > (sz == 12 ? 0xff7U : sz == 16 ? 0xfff7U : 0xffffff7);
}
/*
* Offset-based I/O primitive
*/
static int
ioread(DOS_FS *fs, u_int offset, void *buf, u_int nbyte)
{
char *s;
u_int off, n;
int err;
s = buf;
if ((off = offset & (SECSIZ - 1))) {
offset -= off;
if ((err = iobuf(fs, bytsec(offset))))
return err;
offset += SECSIZ;
if ((n = SECSIZ - off) > nbyte)
n = nbyte;
memcpy(s, fs->buf + off, n);
s += n;
nbyte -= n;
}
n = nbyte & (SECSIZ - 1);
if (nbyte -= n) {
if ((err = ioget(fs->fd, bytsec(offset), s, bytsec(nbyte))))
return err;
offset += nbyte;
s += nbyte;
}
if (n) {
if ((err = iobuf(fs, bytsec(offset))))
return err;
memcpy(s, fs->buf, n);
}
return 0;
}
/*
* Buffered sector-based I/O primitive
*/
static int
iobuf(DOS_FS *fs, u_int lsec)
{
int err;
if (fs->bufsec != lsec) {
if ((err = ioget(fs->fd, lsec, fs->buf, 1)))
return err;
fs->bufsec = lsec;
}
return 0;
}
/*
* Sector-based I/O primitive
*/
static int
ioget(struct open_file *fd, u_int lsec, void *buf, u_int nsec)
{
int err;
if ((err = (fd->f_dev->dv_strategy)(fd->f_devdata, F_READ, lsec,
secbyt(nsec), buf, NULL)))
return(err);
return(0);
}
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