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freebsd/sbin/fsck_msdosfs/fat.c

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/*
* Copyright (C) 1995, 1996, 1997 Wolfgang Solfrank
* Copyright (c) 1995 Martin Husemann
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Martin Husemann
* and Wolfgang Solfrank.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``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 AUTHORS 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.
*/
#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: fat.c,v 1.12 2000/10/10 20:24:52 is Exp $");
static const char rcsid[] =
"$FreeBSD$";
#endif /* not lint */
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <stdio.h>
#include <unistd.h>
#include "ext.h"
#include "fsutil.h"
static int checkclnum(struct bootblock *, int, cl_t, cl_t *);
static int clustdiffer(cl_t, cl_t *, cl_t *, int);
static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *);
static int _readfat(int, struct bootblock *, int, u_char **);
/*-
* The first 2 FAT entries contain pseudo-cluster numbers with the following
* layout:
*
* 31...... ........ ........ .......0
* rrrr1111 11111111 11111111 mmmmmmmm FAT32 entry 0
* rrrrsh11 11111111 11111111 11111xxx FAT32 entry 1
*
* 11111111 mmmmmmmm FAT16 entry 0
* sh111111 11111xxx FAT16 entry 1
*
* r = reserved
* m = BPB media ID byte
* s = clean flag (1 = dismounted; 0 = still mounted)
* h = hard error flag (1 = ok; 0 = I/O error)
* x = any value ok
*/
int
checkdirty(int fs, struct bootblock *boot)
{
off_t off;
u_char *buffer;
int ret = 0;
if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK)
return 0;
off = boot->ResSectors;
off *= boot->BytesPerSec;
buffer = malloc(boot->BytesPerSec);
if (buffer == NULL) {
perror("No space for FAT");
return 1;
}
if (lseek(fs, off, SEEK_SET) != off) {
perror("Unable to read FAT");
goto err;
}
if (read(fs, buffer, boot->BytesPerSec) != boot->BytesPerSec) {
perror("Unable to read FAT");
goto err;
}
/*
* If we don't understand the FAT, then the file system must be
* assumed to be unclean.
*/
if (buffer[0] != boot->Media || buffer[1] != 0xff)
goto err;
if (boot->ClustMask == CLUST16_MASK) {
if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f)
goto err;
} else {
if (buffer[2] != 0xff || (buffer[3] & 0x0f) != 0x0f
|| (buffer[4] & 0xf8) != 0xf8 || buffer[5] != 0xff
|| buffer[6] != 0xff || (buffer[7] & 0x03) != 0x03)
goto err;
}
/*
* Now check the actual clean flag (and the no-error flag).
*/
if (boot->ClustMask == CLUST16_MASK) {
if ((buffer[3] & 0xc0) == 0xc0)
ret = 1;
} else {
if ((buffer[7] & 0x0c) == 0x0c)
ret = 1;
}
err:
free(buffer);
return ret;
}
/*
* Check a cluster number for valid value
*/
static int
checkclnum(struct bootblock *boot, int fat, cl_t cl, cl_t *next)
{
if (*next >= (CLUST_RSRVD&boot->ClustMask))
*next |= ~boot->ClustMask;
if (*next == CLUST_FREE) {
boot->NumFree++;
return FSOK;
}
if (*next == CLUST_BAD) {
boot->NumBad++;
return FSOK;
}
if (*next < CLUST_FIRST
|| (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n",
cl, fat,
*next < CLUST_RSRVD ? "out of range" : "reserved",
*next&boot->ClustMask);
if (ask(0, "Truncate")) {
*next = CLUST_EOF;
return FSFATMOD;
}
return FSERROR;
}
return FSOK;
}
/*
* Read a FAT from disk. Returns 1 if successful, 0 otherwise.
*/
static int
_readfat(int fs, struct bootblock *boot, int no, u_char **buffer)
{
off_t off;
*buffer = malloc(boot->FATsecs * boot->BytesPerSec);
if (*buffer == NULL) {
perror("No space for FAT");
return 0;
}
off = boot->ResSectors + no * boot->FATsecs;
off *= boot->BytesPerSec;
if (lseek(fs, off, SEEK_SET) != off) {
perror("Unable to read FAT");
goto err;
}
if (read(fs, *buffer, boot->FATsecs * boot->BytesPerSec)
!= boot->FATsecs * boot->BytesPerSec) {
perror("Unable to read FAT");
goto err;
}
return 1;
err:
free(*buffer);
return 0;
}
/*
* Read a FAT and decode it into internal format
*/
int
readfat(int fs, struct bootblock *boot, int no, struct fatEntry **fp)
{
struct fatEntry *fat;
u_char *buffer, *p;
cl_t cl;
int ret = FSOK;
boot->NumFree = boot->NumBad = 0;
if (!_readfat(fs, boot, no, &buffer))
return FSFATAL;
fat = calloc(boot->NumClusters, sizeof(struct fatEntry));
if (fat == NULL) {
perror("No space for FAT");
free(buffer);
return FSFATAL;
}
if (buffer[0] != boot->Media
|| buffer[1] != 0xff || buffer[2] != 0xff
|| (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
|| (boot->ClustMask == CLUST32_MASK
&& ((buffer[3]&0x0f) != 0x0f
|| buffer[4] != 0xff || buffer[5] != 0xff
|| buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
/* Windows 95 OSR2 (and possibly any later) changes
* the FAT signature to 0xXXffff7f for FAT16 and to
* 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
* file system is dirty if it doesn't reboot cleanly.
* Check this special condition before errorring out.
*/
if (buffer[0] == boot->Media && buffer[1] == 0xff
&& buffer[2] == 0xff
&& ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
|| (boot->ClustMask == CLUST32_MASK
&& buffer[3] == 0x0f && buffer[4] == 0xff
&& buffer[5] == 0xff && buffer[6] == 0xff
&& buffer[7] == 0x07)))
ret |= FSDIRTY;
else {
/* just some odd byte sequence in FAT */
switch (boot->ClustMask) {
case CLUST32_MASK:
pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
"FAT starts with odd byte sequence",
buffer[0], buffer[1], buffer[2], buffer[3],
buffer[4], buffer[5], buffer[6], buffer[7]);
break;
case CLUST16_MASK:
pwarn("%s (%02x%02x%02x%02x)\n",
"FAT starts with odd byte sequence",
buffer[0], buffer[1], buffer[2], buffer[3]);
break;
default:
pwarn("%s (%02x%02x%02x)\n",
"FAT starts with odd byte sequence",
buffer[0], buffer[1], buffer[2]);
break;
}
if (ask(1, "Correct"))
ret |= FSFIXFAT;
}
}
switch (boot->ClustMask) {
case CLUST32_MASK:
p = buffer + 8;
break;
case CLUST16_MASK:
p = buffer + 4;
break;
default:
p = buffer + 3;
break;
}
for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
switch (boot->ClustMask) {
case CLUST32_MASK:
fat[cl].next = p[0] + (p[1] << 8)
+ (p[2] << 16) + (p[3] << 24);
fat[cl].next &= boot->ClustMask;
ret |= checkclnum(boot, no, cl, &fat[cl].next);
cl++;
p += 4;
break;
case CLUST16_MASK:
fat[cl].next = p[0] + (p[1] << 8);
ret |= checkclnum(boot, no, cl, &fat[cl].next);
cl++;
p += 2;
break;
default:
fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
ret |= checkclnum(boot, no, cl, &fat[cl].next);
cl++;
if (cl >= boot->NumClusters)
break;
fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
ret |= checkclnum(boot, no, cl, &fat[cl].next);
cl++;
p += 3;
break;
}
}
free(buffer);
*fp = fat;
return ret;
}
/*
* Get type of reserved cluster
*/
char *
rsrvdcltype(cl_t cl)
{
if (cl == CLUST_FREE)
return "free";
if (cl < CLUST_BAD)
return "reserved";
if (cl > CLUST_BAD)
return "as EOF";
return "bad";
}
static int
clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, int fatnum)
{
if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) {
if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD
&& *cp2 != CLUST_FREE && *cp2 < CLUST_BAD)
|| (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
pwarn("Cluster %u is marked %s with different indicators\n",
cl, rsrvdcltype(*cp1));
if (ask(1, "Fix")) {
*cp2 = *cp1;
return FSFATMOD;
}
return FSFATAL;
}
pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %d\n",
cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
if (ask(0, "Use FAT 0's entry")) {
*cp2 = *cp1;
return FSFATMOD;
}
if (ask(0, "Use FAT %d's entry", fatnum)) {
*cp1 = *cp2;
return FSFATMOD;
}
return FSFATAL;
}
pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n",
cl, rsrvdcltype(*cp1), *cp2, fatnum);
if (ask(0, "Use continuation from FAT %d", fatnum)) {
*cp1 = *cp2;
return FSFATMOD;
}
if (ask(0, "Use mark from FAT 0")) {
*cp2 = *cp1;
return FSFATMOD;
}
return FSFATAL;
}
if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %d\n",
cl, *cp1, rsrvdcltype(*cp2), fatnum);
if (ask(0, "Use continuation from FAT 0")) {
*cp2 = *cp1;
return FSFATMOD;
}
if (ask(0, "Use mark from FAT %d", fatnum)) {
*cp1 = *cp2;
return FSFATMOD;
}
return FSERROR;
}
pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %d\n",
cl, *cp1, *cp2, fatnum);
if (ask(0, "Use continuation from FAT 0")) {
*cp2 = *cp1;
return FSFATMOD;
}
if (ask(0, "Use continuation from FAT %d", fatnum)) {
*cp1 = *cp2;
return FSFATMOD;
}
return FSERROR;
}
/*
* Compare two FAT copies in memory. Resolve any conflicts and merge them
* into the first one.
*/
int
comparefat(struct bootblock *boot, struct fatEntry *first,
struct fatEntry *second, int fatnum)
{
cl_t cl;
int ret = FSOK;
for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
if (first[cl].next != second[cl].next)
ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
return ret;
}
void
clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
{
cl_t p, q;
for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
if (fat[p].head != head)
break;
q = fat[p].next;
fat[p].next = fat[p].head = CLUST_FREE;
fat[p].length = 0;
}
}
int
tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *trunc)
{
if (ask(0, "Clear chain starting at %u", head)) {
clearchain(boot, fat, head);
return FSFATMOD;
} else if (ask(0, "Truncate")) {
*trunc = CLUST_EOF;
return FSFATMOD;
} else
return FSERROR;
}
/*
* Check a complete FAT in-memory for crosslinks
*/
int
checkfat(struct bootblock *boot, struct fatEntry *fat)
{
cl_t head, p, h, n;
u_int len;
int ret = 0;
int conf;
/*
* pass 1: figure out the cluster chains.
*/
for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
/* find next untravelled chain */
if (fat[head].head != 0 /* cluster already belongs to some chain */
|| fat[head].next == CLUST_FREE
|| fat[head].next == CLUST_BAD)
continue; /* skip it. */
/* follow the chain and mark all clusters on the way */
for (len = 0, p = head;
p >= CLUST_FIRST && p < boot->NumClusters;
p = fat[p].next) {
fat[p].head = head;
len++;
}
/* the head record gets the length */
fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
}
/*
* pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
* we didn't know the real start of the chain then - would have treated partial
* chains as interlinked with their main chain)
*/
for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
/* find next untravelled chain */
if (fat[head].head != head)
continue;
/* follow the chain to its end (hopefully) */
for (p = head;
(n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
p = n)
if (fat[n].head != head)
break;
if (n >= CLUST_EOFS)
continue;
if (n == CLUST_FREE || n >= CLUST_RSRVD) {
pwarn("Cluster chain starting at %u ends with cluster marked %s\n",
head, rsrvdcltype(n));
ret |= tryclear(boot, fat, head, &fat[p].next);
continue;
}
if (n < CLUST_FIRST || n >= boot->NumClusters) {
pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
head, n);
ret |= tryclear(boot, fat, head, &fat[p].next);
continue;
}
pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n",
head, fat[n].head, n);
conf = tryclear(boot, fat, head, &fat[p].next);
if (ask(0, "Clear chain starting at %u", h = fat[n].head)) {
if (conf == FSERROR) {
/*
* Transfer the common chain to the one not cleared above.
*/
for (p = n;
p >= CLUST_FIRST && p < boot->NumClusters;
p = fat[p].next) {
if (h != fat[p].head) {
/*
* Have to reexamine this chain.
*/
head--;
break;
}
fat[p].head = head;
}
}
clearchain(boot, fat, h);
conf |= FSFATMOD;
}
ret |= conf;
}
return ret;
}
/*
* Write out FATs encoding them from the internal format
*/
int
writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
{
u_char *buffer, *p;
cl_t cl;
int i;
u_int32_t fatsz;
off_t off;
int ret = FSOK;
buffer = malloc(fatsz = boot->FATsecs * boot->BytesPerSec);
if (buffer == NULL) {
perror("No space for FAT");
return FSFATAL;
}
memset(buffer, 0, fatsz);
boot->NumFree = 0;
p = buffer;
if (correct_fat) {
*p++ = (u_char)boot->Media;
*p++ = 0xff;
*p++ = 0xff;
switch (boot->ClustMask) {
case CLUST16_MASK:
*p++ = 0xff;
break;
case CLUST32_MASK:
*p++ = 0x0f;
*p++ = 0xff;
*p++ = 0xff;
*p++ = 0xff;
*p++ = 0x0f;
break;
}
} else {
/* use same FAT signature as the old FAT has */
int count;
u_char *old_fat;
switch (boot->ClustMask) {
case CLUST32_MASK:
count = 8;
break;
case CLUST16_MASK:
count = 4;
break;
default:
count = 3;
break;
}
if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
&old_fat)) {
free(buffer);
return FSFATAL;
}
memcpy(p, old_fat, count);
free(old_fat);
p += count;
}
for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
switch (boot->ClustMask) {
case CLUST32_MASK:
if (fat[cl].next == CLUST_FREE)
boot->NumFree++;
*p++ = (u_char)fat[cl].next;
*p++ = (u_char)(fat[cl].next >> 8);
*p++ = (u_char)(fat[cl].next >> 16);
*p &= 0xf0;
*p++ |= (fat[cl].next >> 24)&0x0f;
break;
case CLUST16_MASK:
if (fat[cl].next == CLUST_FREE)
boot->NumFree++;
*p++ = (u_char)fat[cl].next;
*p++ = (u_char)(fat[cl].next >> 8);
break;
default:
if (fat[cl].next == CLUST_FREE)
boot->NumFree++;
if (cl + 1 < boot->NumClusters
&& fat[cl + 1].next == CLUST_FREE)
boot->NumFree++;
*p++ = (u_char)fat[cl].next;
*p++ = (u_char)((fat[cl].next >> 8) & 0xf)
|(u_char)(fat[cl+1].next << 4);
*p++ = (u_char)(fat[++cl].next >> 4);
break;
}
}
for (i = 0; i < boot->FATs; i++) {
off = boot->ResSectors + i * boot->FATsecs;
off *= boot->BytesPerSec;
if (lseek(fs, off, SEEK_SET) != off
|| write(fs, buffer, fatsz) != fatsz) {
perror("Unable to write FAT");
ret = FSFATAL; /* Return immediately? XXX */
}
}
free(buffer);
return ret;
}
/*
* Check a complete in-memory FAT for lost cluster chains
*/
int
checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
{
cl_t head;
int mod = FSOK;
int ret;
for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
/* find next untravelled chain */
if (fat[head].head != head
|| fat[head].next == CLUST_FREE
|| (fat[head].next >= CLUST_RSRVD
&& fat[head].next < CLUST_EOFS)
|| (fat[head].flags & FAT_USED))
continue;
pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n",
head, fat[head].length);
mod |= ret = reconnect(dosfs, boot, fat, head);
if (mod & FSFATAL)
break;
if (ret == FSERROR && ask(0, "Clear")) {
clearchain(boot, fat, head);
mod |= FSFATMOD;
}
}
finishlf();
if (boot->FSInfo) {
ret = 0;
if (boot->FSFree != boot->NumFree) {
pwarn("Free space in FSInfo block (%d) not correct (%d)\n",
boot->FSFree, boot->NumFree);
if (ask(1, "Fix")) {
boot->FSFree = boot->NumFree;
ret = 1;
}
}
if (boot->NumFree && fat[boot->FSNext].next != CLUST_FREE) {
pwarn("Next free cluster in FSInfo block (%u) not free\n",
boot->FSNext);
if (ask(1, "Fix"))
for (head = CLUST_FIRST; head < boot->NumClusters; head++)
if (fat[head].next == CLUST_FREE) {
boot->FSNext = head;
ret = 1;
break;
}
}
if (ret)
mod |= writefsinfo(dosfs, boot);
}
return mod;
}
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