pcfs/fsck/fat.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 1999 by Sun Microsystems, Inc.
 * All rights reserved.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * fsck_pcfs -- routines for manipulating the FAT.
 */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <libintl.h>
#include <sys/dktp/fdisk.h>
#include <sys/fs/pc_fs.h>
#include <sys/fs/pc_dir.h>
#include <sys/fs/pc_label.h>
#include "pcfs_common.h"
#include "fsck_pcfs.h"

extern  int32_t BytesPerCluster;
extern  int32_t TotalClusters;
extern  int32_t LastCluster;
extern  off64_t FirstClusterOffset;
extern  off64_t PartitionOffset;
extern  bpb_t   TheBIOSParameterBlock;
extern  int ReadOnly;
extern  int IsFAT32;
extern  int Verbose;

static  uchar_t *TheFAT;
static  int FATRewriteNeeded = 0;

int32_t     FATSize;
short       FATEntrySize;

static off64_t
seekFAT(int fd)
{
    off64_t seekto;
    /*
     *  The FAT(s) immediately follows the reserved sectors.
     */
    seekto = TheBIOSParameterBlock.bpb.resv_sectors *
        TheBIOSParameterBlock.bpb.bytes_per_sector + PartitionOffset;
    return (lseek64(fd, seekto, SEEK_SET));
}

void
getFAT(int fd)
{
    ssize_t bytesRead;

    if (TheFAT != NULL) {
        return;
    } else if ((TheFAT = (uchar_t *)malloc(FATSize)) == NULL) {
        mountSanityCheckFails();
        perror(gettext("No memory for a copy of the FAT"));
        (void) close(fd);
        exit(7);
    }
    if (seekFAT(fd) < 0) {
        mountSanityCheckFails();
        perror(gettext("Cannot seek to FAT"));
        (void) close(fd);
        exit(7);
    }
    if (Verbose)
        (void) fprintf(stderr,
            gettext("Reading FAT\n"));
    if ((bytesRead = read(fd, TheFAT, FATSize)) != FATSize) {
        mountSanityCheckFails();
        if (bytesRead < 0) {
            perror(gettext("Cannot read a FAT"));
        } else {
            (void) fprintf(stderr,
                gettext("Short read of FAT."));
        }
        (void) close(fd);
        exit(7);
    }
    /*
     * XXX - might want to read the other copies of the FAT
     * for comparison and/or to use if the first one seems hosed.
     */
    if (Verbose) {
        (void) fprintf(stderr,
            gettext("Dump of FAT's first 32 bytes.\n"));
        header_for_dump();
        dump_bytes(TheFAT, 32);
    }
}

void
writeFATMods(int fd)
{
    ssize_t bytesWritten;

    if (TheFAT == NULL) {
        (void) fprintf(stderr,
            gettext("Internal error: No FAT to write\n"));
        (void) close(fd);
        exit(11);
    }
    if (!FATRewriteNeeded) {
        if (Verbose) {
            (void) fprintf(stderr,
                gettext("No FAT changes need to be written.\n"));
        }
        return;
    }
    if (ReadOnly)
        return;
    if (Verbose)
        (void) fprintf(stderr, gettext("Writing FAT\n"));
    if (seekFAT(fd) < 0) {
        perror(gettext("Cannot seek to FAT"));
        (void) close(fd);
        exit(11);
    }
    if ((bytesWritten = write(fd, TheFAT, FATSize)) != FATSize) {
        if (bytesWritten < 0) {
            perror(gettext("Cannot write FAT"));
        } else {
            (void) fprintf(stderr,
                gettext("Short write of FAT."));
        }
        (void) close(fd);
        exit(11);
    }
    FATRewriteNeeded = 0;
}

/*
 *  checkFAT32CleanBit()
 *  Return non-zero if the bit indicating proper Windows shutdown has
 *  been set.
 */
int
checkFAT32CleanBit(int fd)
{
    getFAT(fd);
    return (TheFAT[WIN_SHUTDOWN_STATUS_BYTE] & WIN_SHUTDOWN_BIT_MASK);
}

static uchar_t *
findClusterEntryInFAT(int32_t currentCluster)
{
    int32_t idx;
    if (FATEntrySize == 32) {
        idx = currentCluster * 4;
    } else if (FATEntrySize == 16) {
        idx = currentCluster * 2;
    } else {
        idx = currentCluster + currentCluster/2;
    }
    return (TheFAT + idx);
}

/*
 *  {read,write}FATentry
 *  For the 16 and 32 bit FATs these routines are relatively easy
 *  to follow.
 *
 *  12 bit FATs are kind of strange, though.  The magic index for
 *  12 bit FATS computed below, 1.5 * clusterNum, is a
 *  simplification that there are 8 bits in a byte, so you need
 *  1.5 bytes per entry.
 *
 *  It's easiest to think about FAT12 entries in pairs:
 *
 *  ---------------------------------------------
 *  | mid1 | low1 | low2 | high1 | high2 | mid2 |
 *  ---------------------------------------------
 *
 *  Each box in the diagram represents a nibble (4 bits) of a FAT
 *  entry.  A FAT entry is made up of three nibbles.  So if you
 *  look closely, you'll see that first byte of the pair of
 *  entries contains the low and middle nibbles of the first
 *  entry.  The second byte has the low nibble of the second entry
 *  and the high nibble of the first entry.  Those two bytes alone
 *  are enough to read the first entry.  The second FAT entry is
 *  finished out by the last nibble pair.
 */
int32_t
readFATEntry(int32_t currentCluster)
{
    int32_t value;
    uchar_t *ep;

    ep = findClusterEntryInFAT(currentCluster);
    if (FATEntrySize == 32) {
        read_32_bits(ep, (uint32_t *)&value);
    } else if (FATEntrySize == 16) {
        read_16_bits(ep, (uint32_t *)&value);
        /*
         *  Convert 16 bit entry to 32 bit if we are
         *  into the reserved or higher values.
         */
        if (value >= PCF_RESCLUSTER)
            value |= 0xFFF0000;
    } else {
        value = 0;
        if (currentCluster & 1) {
            /*
             * Odd numbered cluster
             */
            value = (((unsigned int)*ep++ & 0xf0) >> 4);
            value += (*ep << 4);
        } else {
            value = *ep++;
            value += ((*ep & 0x0f) << 8);
        }
        /*
         *  Convert 12 bit entry to 32 bit if we are
         *  into the reserved or higher values.
         */
        if (value >= PCF_12BCLUSTER)
            value |= 0xFFFF000;
    }
    return (value);
}

void
writeFATEntry(int32_t currentCluster, int32_t value)
{
    uchar_t *ep;

    FATRewriteNeeded = 1;
    ep = findClusterEntryInFAT(currentCluster);
    if (FATEntrySize == 32) {
        store_32_bits(&ep, value);
    } else if (FATEntrySize == 16) {
        store_16_bits(&ep, value);
    } else {
        if (currentCluster & 1) {
            /*
             * Odd numbered cluster
             */
            *ep = (*ep & 0x0f) | ((value << 4) & 0xf0);
            ep++;
            *ep = (value >> 4) & 0xff;
        } else {
            *ep++ = value & 0xff;
            *ep = (*ep & 0xf0) | ((value >> 8) & 0x0f);
        }
    }
}

/*
 * reservedInFAT - Is this cluster marked in the reserved range?
 *  The range from PCF_RESCLUSTER32 to PCF_BADCLUSTER32 - 1,
 *  have been reserved by Microsoft.  No cluster should be
 *  marked with these; they are effectively invalid cluster values.
 */
int
reservedInFAT(int32_t clusterNum)
{
    int32_t e;

    e = readFATEntry(clusterNum);
    return (e >= PCF_RESCLUSTER32 && e < PCF_BADCLUSTER32);
}

/*
 *  badInFAT - Is this cluster marked as bad?  I.e., is it inaccessible?
 */
int
badInFAT(int32_t clusterNum)
{
    return (readFATEntry(clusterNum) == PCF_BADCLUSTER32);
}

/*
 *  lastInFAT - Is this cluster marked as free?  I.e., is it available
 *  for use?
 */
int
freeInFAT(int32_t clusterNum)
{
    return (readFATEntry(clusterNum) == PCF_FREECLUSTER);
}

/*
 *  lastInFAT - Is this cluster the last in its cluster chain?
 */
int
lastInFAT(int32_t clusterNum)
{
    return (readFATEntry(clusterNum) == PCF_LASTCLUSTER32);
}

/*
 *  markLastInFAT - Mark this cluster as the last in its cluster chain.
 */
void
markLastInFAT(int32_t clusterNum)
{
    writeFATEntry(clusterNum, PCF_LASTCLUSTER32);
}

void
markFreeInFAT(int32_t clusterNum)
{
    writeFATEntry(clusterNum, PCF_FREECLUSTER);
}

void
markBadInFAT(int32_t clusterNum)
{
    writeFATEntry(clusterNum, PCF_BADCLUSTER32);
}