/* fat.c - Read/write access to the FAT
Copyright (C) 1993 Werner Almesberger <werner.almesberger@lrc.di.epfl.ch>
Copyright (C) 1998 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
On Debian systems, the complete text of the GNU General Public License
can be found in /usr/share/common-licenses/GPL-3 file.
*/
/* FAT32, VFAT, Atari format support, and various fixes additions May 1998
* by Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de> */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "common.h"
#include "dosfsck.h"
#include "io.h"
#include "check.h"
#include "fat.h"
static void get_fat(FAT_ENTRY *entry,void *fat,unsigned long cluster,DOS_FS *fs)
{
unsigned char *ptr;
switch(fs->fat_bits) {
case 12:
ptr = &((unsigned char *) fat)[cluster*3/2];
entry->value = 0xfff & (cluster & 1 ? (ptr[0] >> 4) | (ptr[1] << 4) :
(ptr[0] | ptr[1] << 8));
break;
case 16:
entry->value = CF_LE_W(((unsigned short *) fat)[cluster]);
break;
case 32:
/* According to M$, the high 4 bits of a FAT32 entry are reserved and
* are not part of the cluster number. So we cut them off. */
{
unsigned long e = CF_LE_L(((unsigned int *) fat)[cluster]);
entry->value = e & 0xfffffff;
entry->reserved = e >> 28;
}
break;
default:
die("Bad FAT entry size: %d bits.",fs->fat_bits);
}
entry->owner = NULL;
}
void read_fat(DOS_FS *fs)
{
int eff_size;
unsigned long i;
void *first,*second = NULL;
int first_ok,second_ok;
eff_size = ((fs->clusters+2ULL)*fs->fat_bits+7)/8ULL;
first = alloc(eff_size);
fs_read(fs->fat_start,eff_size,first);
if (fs->nfats > 1) {
second = alloc(eff_size);
fs_read(fs->fat_start+fs->fat_size,eff_size,second);
}
if (second && memcmp(first,second,eff_size) != 0) {
FAT_ENTRY first_media, second_media;
get_fat(&first_media,first,0,fs);
get_fat(&second_media,second,0,fs);
first_ok = (first_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
second_ok = (second_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
if (first_ok && !second_ok) {
printf("FATs differ - using first FAT.\n");
fs_write(fs->fat_start+fs->fat_size,eff_size,first);
}
if (!first_ok && second_ok) {
printf("FATs differ - using second FAT.\n");
fs_write(fs->fat_start,eff_size,second);
memcpy(first,second,eff_size);
}
if (first_ok && second_ok) {
if (interactive) {
printf("FATs differ but appear to be intact. Use which FAT ?\n"
"1) Use first FAT\n2) Use second FAT\n");
if (get_key("12","?") == '1') {
fs_write(fs->fat_start+fs->fat_size,eff_size,first);
} else {
fs_write(fs->fat_start,eff_size,second);
memcpy(first,second,eff_size);
}
}
else {
printf("FATs differ but appear to be intact. Using first "
"FAT.\n");
fs_write(fs->fat_start+fs->fat_size,eff_size,first);
}
}
if (!first_ok && !second_ok) {
printf("Both FATs appear to be corrupt. Giving up.\n");
exit(1);
}
}
if (second) {
free(second);
}
fs->fat = qalloc(&mem_queue,sizeof(FAT_ENTRY)*(fs->clusters+2ULL));
for (i = 2; i < fs->clusters+2; i++) get_fat(&fs->fat[i],first,i,fs);
for (i = 2; i < fs->clusters+2; i++)
if (fs->fat[i].value >= fs->clusters+2 &&
(fs->fat[i].value < FAT_MIN_BAD(fs))) {
printf("Cluster %ld out of range (%ld > %ld). Setting to EOF.\n",
i-2,fs->fat[i].value,fs->clusters+2-1);
set_fat(fs,i,-1);
}
free(first);
}
void set_fat(DOS_FS *fs,unsigned long cluster,unsigned long new)
{
unsigned char data[4];
int size;
loff_t offs;
if ((long)new == -1)
new = FAT_EOF(fs);
else if ((long)new == -2)
new = FAT_BAD(fs);
switch( fs->fat_bits ) {
case 12:
offs = fs->fat_start+cluster*3/2;
if (cluster & 1) {
data[0] = ((new & 0xf) << 4) | (fs->fat[cluster-1].value >> 8);
data[1] = new >> 4;
}
else {
data[0] = new & 0xff;
data[1] = (new >> 8) | (cluster == fs->clusters-1 ? 0 :
(0xff & fs->fat[cluster+1].value) << 4);
}
size = 2;
break;
case 16:
offs = fs->fat_start+cluster*2;
*(unsigned short *) data = CT_LE_W(new);
size = 2;
break;
case 32:
offs = fs->fat_start+cluster*4;
/* According to M$, the high 4 bits of a FAT32 entry are reserved and
* are not part of the cluster number. So we never touch them. */
*(unsigned long *) data = CT_LE_L( (new & 0xfffffff) |
(fs->fat[cluster].reserved << 28) );
size = 4;
break;
default:
die("Bad FAT entry size: %d bits.",fs->fat_bits);
}
fs->fat[cluster].value = new;
fs_write(offs,size,&data);
fs_write(offs+fs->fat_size,size,&data);
}
int bad_cluster(DOS_FS *fs,unsigned long cluster)
{
return FAT_IS_BAD(fs,fs->fat[cluster].value);
}
unsigned long next_cluster(DOS_FS *fs,unsigned long cluster)
{
unsigned long value;
value = fs->fat[cluster].value;
if (FAT_IS_BAD(fs,value))
die("Internal error: next_cluster on bad cluster");
return FAT_IS_EOF(fs,value) ? -1 : value;
}
loff_t cluster_start(DOS_FS *fs,unsigned long cluster)
{
return fs->data_start+((loff_t)cluster-2)*(unsigned long long)fs->cluster_size;
}
void set_owner(DOS_FS *fs,unsigned long cluster,DOS_FILE *owner)
{
if (owner && fs->fat[cluster].owner)
die("Internal error: attempt to change file owner");
fs->fat[cluster].owner = owner;
}
DOS_FILE *get_owner(DOS_FS *fs,unsigned long cluster)
{
return fs->fat[cluster].owner;
}
void fix_bad(DOS_FS *fs)
{
unsigned long i;
if (verbose)
printf("Checking for bad clusters.\n");
for (i = 2; i < fs->clusters+2; i++)
if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
if (!fs_test(cluster_start(fs,i),fs->cluster_size)) {
printf("Cluster %lu is unreadable.\n",i);
set_fat(fs,i,-2);
}
}
void reclaim_free(DOS_FS *fs)
{
int reclaimed;
unsigned long i;
if (verbose)
printf("Checking for unused clusters.\n");
reclaimed = 0;
for (i = 2; i < fs->clusters+2; i++)
if (!get_owner(fs,i) && fs->fat[i].value &&
!FAT_IS_BAD(fs,fs->fat[i].value)) {
set_fat(fs,i,0);
reclaimed++;
}
if (reclaimed)
printf("Reclaimed %d unused cluster%s (%llu bytes).\n",reclaimed,
reclaimed == 1 ? "" : "s",(unsigned long long)reclaimed*fs->cluster_size);
}
static void tag_free(DOS_FS *fs,DOS_FILE *ptr)
{
DOS_FILE *owner;
int prev;
unsigned long i,walk;
for (i = 2; i < fs->clusters+2; i++)
if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
!get_owner(fs,i) && !fs->fat[i].prev) {
prev = 0;
for (walk = i; walk > 0 && walk != -1;
walk = next_cluster(fs,walk)) {
if (!(owner = get_owner(fs,walk))) set_owner(fs,walk,ptr);
else if (owner != ptr)
die("Internal error: free chain collides with file");
else {
set_fat(fs,prev,-1);
break;
}
prev = walk;
}
}
}
void reclaim_file(DOS_FS *fs)
{
DOS_FILE dummy;
int reclaimed,files,changed;
unsigned long i,next,walk;
if (verbose)
printf("Reclaiming unconnected clusters.\n");
for (i = 2; i < fs->clusters+2; i++) fs->fat[i].prev = 0;
for (i = 2; i < fs->clusters+2; i++) {
next = fs->fat[i].value;
if (!get_owner(fs,i) && next && next < fs->clusters+2) {
if (get_owner(fs,next) || !fs->fat[next].value ||
FAT_IS_BAD(fs,fs->fat[next].value)) set_fat(fs,i,-1);
else fs->fat[next].prev++;
}
}
do {
tag_free(fs,&dummy);
changed = 0;
for (i = 2; i < fs->clusters+2; i++)
if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
!get_owner(fs, i)) {
if (!fs->fat[fs->fat[i].value].prev--)
die("Internal error: prev going below zero");
set_fat(fs,i,-1);
changed = 1;
printf("Broke cycle at cluster %lu in free chain.\n",i);
break;
}
}
while (changed);
files = reclaimed = 0;
for (i = 2; i < fs->clusters+2; i++)
if (get_owner(fs,i) == &dummy && !fs->fat[i].prev) {
DIR_ENT de;
loff_t offset;
files++;
offset = alloc_rootdir_entry(fs,&de,"FSCK%04dREC");
de.start = CT_LE_W(i&0xffff);
if (fs->fat_bits == 32)
de.starthi = CT_LE_W(i>>16);
for (walk = i; walk > 0 && walk != -1;
walk = next_cluster(fs,walk)) {
de.size = CT_LE_L(CF_LE_L(de.size)+fs->cluster_size);
reclaimed++;
}
fs_write(offset,sizeof(DIR_ENT),&de);
}
if (reclaimed)
printf("Reclaimed %d unused cluster%s (%llu bytes) in %d chain%s.\n",
reclaimed,reclaimed == 1 ? "" : "s",(unsigned long long)reclaimed*fs->cluster_size,files,
files == 1 ? "" : "s");
}
unsigned long update_free(DOS_FS *fs)
{
unsigned long i;
unsigned long free = 0;
int do_set = 0;
for (i = 2; i < fs->clusters+2; i++)
if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
++free;
if (!fs->fsinfo_start)
return free;
if (verbose)
printf("Checking free cluster summary.\n");
if (fs->free_clusters >= 0) {
if (free != fs->free_clusters) {
printf( "Free cluster summary wrong (%ld vs. really %ld)\n",
fs->free_clusters,free);
if (interactive)
printf( "1) Correct\n2) Don't correct\n" );
else printf( " Auto-correcting.\n" );
if (!interactive || get_key("12","?") == '1')
do_set = 1;
}
}
else {
printf( "Free cluster summary uninitialized (should be %ld)\n", free );
if (interactive)
printf( "1) Set it\n2) Leave it uninitialized\n" );
else printf( " Auto-setting.\n" );
if (!interactive || get_key("12","?") == '1')
do_set = 1;
}
if (do_set) {
fs->free_clusters = free;
free = CT_LE_L(free);
fs_write(fs->fsinfo_start+offsetof(struct info_sector,free_clusters),
sizeof(free),&free);
}
return free;
}
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