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- /* 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;
- }
- /* Local Variables: */
- /* tab-width: 8 */
- /* End: */
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