512 lines
13 KiB
C
512 lines
13 KiB
C
/* $NetBSD: fat.c,v 1.4 1996/09/27 23:22:53 christos Exp $ */
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/*
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* Copyright (C) 1995, 1996 Wolfgang Solfrank
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* Copyright (c) 1995 Martin Husemann
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Martin Husemann
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* and Wolfgang Solfrank.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef lint
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static char rcsid[] = "$NetBSD: fat.c,v 1.4 1996/09/27 23:22:53 christos Exp $";
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#endif /* not lint */
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#include <stdlib.h>
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#include <string.h>
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#include <ctype.h>
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#include <stdio.h>
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#include <unistd.h>
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#include "ext.h"
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#include "fsutil.h"
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static int checkclnum __P((struct bootblock *, int, cl_t, cl_t *));
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static int clustdiffer __P((cl_t, cl_t *, cl_t *, int));
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/*
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* Check a cluster number for valid value
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*/
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static int
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checkclnum(boot, fat, cl, next)
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struct bootblock *boot;
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int fat;
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cl_t cl;
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cl_t *next;
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{
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if (!boot->Is16BitFat && *next >= (CLUST_RSRVD&0xfff))
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*next |= 0xf000;
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if (*next == CLUST_FREE) {
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boot->NumFree++;
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return FSOK;
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}
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if (*next < CLUST_FIRST
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|| (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
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pwarn("Cluster %d in FAT %d continues with %s cluster number %d\n",
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cl, fat,
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*next < CLUST_RSRVD ? "out of range" : "reserved",
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*next);
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if (ask(0, "Truncate")) {
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*next = CLUST_EOF;
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return FSFATMOD;
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}
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return FSERROR;
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}
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return FSOK;
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}
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/*
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* Read a FAT and decode it into internal format
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*/
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int
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readfat(fs, boot, no, fp)
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int fs;
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struct bootblock *boot;
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int no;
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struct fatEntry **fp;
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{
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struct fatEntry *fat;
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u_char *buffer, *p;
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cl_t cl;
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off_t off;
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int size;
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int ret = FSOK;
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boot->NumFree = 0;
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fat = malloc(sizeof(struct fatEntry) * boot->NumClusters);
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buffer = malloc(boot->FATsecs * boot->BytesPerSec);
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if (fat == NULL || buffer == NULL) {
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perror("No space for FAT");
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if (fat)
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free(fat);
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return FSFATAL;
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}
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memset(fat, 0, sizeof(struct fatEntry) * boot->NumClusters);
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off = boot->ResSectors + no * boot->FATsecs;
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off *= boot->BytesPerSec;
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if (lseek(fs, off, SEEK_SET) != off) {
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perror("Unable to read FAT");
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free(buffer);
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free(fat);
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return FSFATAL;
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}
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if ((size = read(fs, buffer, boot->FATsecs * boot->BytesPerSec))
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!= boot->FATsecs * boot->BytesPerSec) {
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if (size < 0)
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perror("Unable to read FAT");
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else
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pfatal("Short FAT?");
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free(buffer);
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free(fat);
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return FSFATAL;
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}
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/*
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* Remember start of FAT to allow keeping it in write_fat.
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*/
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fat[0].length = buffer[0]|(buffer[1] << 8)|(buffer[2] << 16);
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if (boot->Is16BitFat)
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fat[0].length |= buffer[3] << 24;
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if (buffer[1] != 0xff || buffer[2] != 0xff
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|| (boot->Is16BitFat && buffer[3] != 0xff)) {
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char *msg = boot->Is16BitFat
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? "FAT starts with odd byte sequence (%02x%02x%02x%02x)\n"
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: "FAT starts with odd byte sequence (%02x%02x%02x)\n";
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pwarn(msg, buffer[0], buffer[1], buffer[2], buffer[3]);
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if (ask(1, "Correct")) {
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fat[0].length = boot->Media|0xffffff;
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ret |= FSFATMOD;
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}
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}
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p = buffer + (boot->Is16BitFat ? 4 : 3);
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for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
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if (boot->Is16BitFat) {
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fat[cl].next = p[0] + (p[1] << 8);
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ret |= checkclnum(boot, no, cl, &fat[cl].next);
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cl++;
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p += 2;
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} else {
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fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
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ret |= checkclnum(boot, no, cl, &fat[cl].next);
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cl++;
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if (cl >= boot->NumClusters)
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break;
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fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
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ret |= checkclnum(boot, no, cl, &fat[cl].next);
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cl++;
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p += 3;
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}
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}
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free(buffer);
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*fp = fat;
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return ret;
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}
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/*
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* Get type of reserved cluster
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*/
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char *
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rsrvdcltype(cl)
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cl_t cl;
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{
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if (cl < CLUST_BAD)
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return "reserved";
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if (cl > CLUST_BAD)
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return "as EOF";
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return "bad";
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}
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static int
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clustdiffer(cl, cp1, cp2, fatnum)
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cl_t cl;
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cl_t *cp1;
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cl_t *cp2;
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int fatnum;
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{
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if (*cp1 >= CLUST_RSRVD) {
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if (*cp2 >= CLUST_RSRVD) {
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if ((*cp1 < CLUST_BAD && *cp2 < CLUST_BAD)
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|| (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
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pwarn("Cluster %d is marked %s with different indicators, ",
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cl, rsrvdcltype(*cp1));
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if (ask(1, "fix")) {
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*cp2 = *cp1;
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return FSFATMOD;
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}
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return FSFATAL;
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}
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pwarn("Cluster %d is marked %s in FAT 1, %s in FAT %d\n",
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cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
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if (ask(0, "use FAT #1's entry")) {
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*cp2 = *cp1;
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return FSFATMOD;
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}
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if (ask(0, "use FAT #%d's entry", fatnum)) {
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*cp1 = *cp2;
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return FSFATMOD;
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}
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return FSFATAL;
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}
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pwarn("Cluster %d is marked %s in FAT 1, but continues with cluster %d in FAT %d\n",
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cl, rsrvdcltype(*cp1), *cp2, fatnum);
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if (ask(0, "Use continuation from FAT %d", fatnum)) {
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*cp1 = *cp2;
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return FSFATMOD;
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}
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if (ask(0, "Use mark from FAT 1")) {
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*cp2 = *cp1;
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return FSFATMOD;
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}
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return FSFATAL;
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}
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if (*cp2 >= CLUST_RSRVD) {
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pwarn("Cluster %d continues with cluster %d in FAT 1, but is marked %s in FAT %d\n",
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cl, *cp1, rsrvdcltype(*cp2), fatnum);
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if (ask(0, "Use continuation from FAT 1")) {
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*cp2 = *cp1;
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return FSFATMOD;
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}
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if (ask(0, "Use mark from FAT %d", fatnum)) {
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*cp1 = *cp2;
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return FSFATMOD;
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}
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return FSERROR;
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}
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pwarn("Cluster %d continues with cluster %d in FAT 1, but with cluster %d in FAT %d\n",
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cl, *cp1, *cp2, fatnum);
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if (ask(0, "Use continuation from FAT 1")) {
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*cp2 = *cp1;
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return FSFATMOD;
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}
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if (ask(0, "Use continuation from FAT %d", fatnum)) {
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*cp1 = *cp2;
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return FSFATMOD;
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}
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return FSERROR;
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}
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/*
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* Compare two FAT copies in memory. Resolve any conflicts and merge them
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* into the first one.
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*/
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int
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comparefat(boot, first, second, fatnum)
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struct bootblock *boot;
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struct fatEntry *first;
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struct fatEntry *second;
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int fatnum;
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{
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cl_t cl;
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int ret = FSOK;
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if (first[0].next != second[0].next) {
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pwarn("Media bytes in cluster 1(%02x) and %d(%02x) differ\n",
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first[0].next, fatnum, second[0].next);
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if (ask(1, "Use media byte from FAT 1")) {
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second[0].next = first[0].next;
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ret |= FSFATMOD;
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} else if (ask(0, "Use media byte from FAT %d", fatnum)) {
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first[0].next = second[0].next;
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ret |= FSFATMOD;
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} else
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ret |= FSERROR;
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}
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for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
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if (first[cl].next != second[cl].next)
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ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
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return ret;
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}
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void
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clearchain(boot, fat, head)
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struct bootblock *boot;
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struct fatEntry *fat;
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cl_t head;
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{
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cl_t p, q;
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for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
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if (fat[p].head != head)
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break;
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q = fat[p].next;
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fat[p].next = fat[p].head = CLUST_FREE;
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fat[p].length = 0;
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}
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}
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/*
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* Check a complete FAT in-memory for crosslinks
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*/
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int
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checkfat(boot, fat)
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struct bootblock *boot;
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struct fatEntry *fat;
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{
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cl_t head, p, h;
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u_int len;
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int ret = 0;
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int conf;
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/*
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* pass 1: figure out the cluster chains.
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*/
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for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
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/* find next untraveled chain */
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if (fat[head].head != 0 /* cluster already belongs to some chain*/
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|| fat[head].next == CLUST_FREE)
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continue; /* skip it. */
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/* follow the chain and mark all clusters on the way */
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for (len = 0, p = head;
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p >= CLUST_FIRST && p < boot->NumClusters;
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p = fat[p].next) {
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fat[p].head = head;
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len++;
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}
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/* the head record gets the length */
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fat[head].length = len;
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}
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/*
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* pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
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* we didn't know the real start of the chain then - would have treated partial
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* chains as interlinked with their main chain)
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*/
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for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
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/* find next untraveled chain */
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if (fat[head].head != head)
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continue;
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/* follow the chain to its end (hopefully) */
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for (p = head;
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fat[p].next >= CLUST_FIRST && fat[p].next < boot->NumClusters;
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p = fat[p].next)
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if (fat[fat[p].next].head != head)
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break;
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if (fat[p].next >= CLUST_EOFS)
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continue;
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if (fat[p].next == 0) {
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pwarn("Cluster chain starting at %d ends with free cluster\n", head);
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if (ask(0, "Clear chain starting at %d", head)) {
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clearchain(boot, fat, head);
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ret |= FSFATMOD;
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} else
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ret |= FSERROR;
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continue;
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}
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if (fat[p].next >= CLUST_RSRVD) {
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pwarn("Cluster chain starting at %d ends with cluster marked %s\n",
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head, rsrvdcltype(fat[p].next));
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if (ask(0, "Clear chain starting at %d", head)) {
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clearchain(boot, fat, head);
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ret |= FSFATMOD;
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} else
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ret |= FSERROR;
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continue;
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}
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if (fat[p].next < CLUST_FIRST || fat[p].next >= boot->NumClusters) {
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pwarn("Cluster chain starting at %d ends with cluster out of range (%d)\n",
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head, fat[p].next);
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if (ask(0, "Clear chain starting at %d", head)) {
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clearchain(boot, fat, head);
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ret |= FSFATMOD;
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} else
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ret |= FSERROR;
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}
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pwarn("Cluster chains starting at %d and %d are linked at cluster %d\n",
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head, fat[p].head, p);
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conf = FSERROR;
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if (ask(0, "Clear chain starting at %d", head)) {
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clearchain(boot, fat, head);
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conf = FSFATMOD;
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}
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if (ask(0, "Clear chain starting at %d", h = fat[p].head)) {
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if (conf == FSERROR) {
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/*
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* Transfer the common chain to the one not cleared above.
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*/
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for (; p >= CLUST_FIRST && p < boot->NumClusters;
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p = fat[p].next) {
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if (h != fat[p].head) {
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/*
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* Have to reexamine this chain.
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*/
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head--;
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break;
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}
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fat[p].head = head;
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}
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}
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clearchain(boot, fat, h);
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conf |= FSFATMOD;
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}
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ret |= conf;
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}
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return ret;
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}
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/*
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* Write out FATs encoding them from the internal format
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*/
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int
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writefat(fs, boot, fat)
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int fs;
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struct bootblock *boot;
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struct fatEntry *fat;
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{
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u_char *buffer, *p;
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cl_t cl;
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int i;
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u_int32_t fatsz;
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off_t off;
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int ret = FSOK;
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buffer = malloc(fatsz = boot->FATsecs * boot->BytesPerSec);
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if (buffer == NULL) {
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perror("No space for FAT");
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return FSFATAL;
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}
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memset(buffer, 0, fatsz);
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boot->NumFree = 0;
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buffer[0] = (u_char)fat[0].length;
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buffer[1] = (u_char)(fat[0].length >> 8);
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if (boot->Is16BitFat)
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buffer[3] = (u_char)(fat[0].length >> 24);
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for (cl = CLUST_FIRST, p = buffer; cl < boot->NumClusters;) {
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if (boot->Is16BitFat) {
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p[0] = (u_char)fat[cl].next;
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if (fat[cl].next == CLUST_FREE)
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boot->NumFree++;
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p[1] = (u_char)(fat[cl++].next >> 8);
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p += 2;
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} else {
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if (fat[cl].next == CLUST_FREE)
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boot->NumFree++;
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if (cl + 1 < boot->NumClusters
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&& fat[cl + 1].next == CLUST_FREE)
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boot->NumFree++;
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p[0] = (u_char)fat[cl].next;
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p[1] = (u_char)((fat[cl].next >> 8) & 0xf)
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|(u_char)(fat[cl+1].next << 4);
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p[2] = (u_char)(fat[cl++].next >> 8);
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p += 3;
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}
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}
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for (i = 0; i < boot->FATs; i++) {
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off = boot->ResSectors + i * boot->FATsecs;
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off *= boot->BytesPerSec;
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if (lseek(fs, off, SEEK_SET) != off
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|| write(fs, buffer, fatsz) != fatsz) {
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perror("Unable to write FAT");
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ret = FSFATAL; /* Return immediately? XXX */
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}
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}
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free(buffer);
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return ret;
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}
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/*
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* Check a complete in-memory FAT for lost cluster chains
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*/
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int
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checklost(dosfs, boot, fat)
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int dosfs;
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struct bootblock *boot;
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struct fatEntry *fat;
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{
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cl_t head;
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int mod = FSOK;
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for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
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/* find next untraveled chain */
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if (fat[head].head != head
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|| fat[head].next == CLUST_FREE
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|| (fat[head].next >= CLUST_RSRVD
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&& fat[head].next < CLUST_EOFS)
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|| (fat[head].flags & FAT_USED))
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continue;
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pwarn("Lost cluster chain at cluster 0x%04x\n%d Cluster(s) lost\n",
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head, fat[head].length);
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mod |= reconnect(dosfs, boot, fat, head);
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if (mod & FSFATAL)
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break;
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}
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finishlf();
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return mod;
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}
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