/*
 * 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) 1999,2000 by Sun Microsystems, Inc.
 * All rights reserved.
 * Copyright (c) 2011 Gary Mills
 * Copyright 2024 MNX Cloud, Inc.
 */

/*
 * fsck_pcfs -- routines for manipulating the BPB (BIOS parameter block)
 * of the file system.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <libintl.h>
#include <sys/types.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"
#include "pcfs_bpb.h"

extern  off64_t FirstClusterOffset;
extern  off64_t PartitionOffset;
extern  int32_t BytesPerCluster;
extern  int32_t TotalClusters;
extern  int32_t LastCluster;
extern  int32_t RootDirSize;
extern  int32_t FATSize;
extern  short   FATEntrySize;
extern  bpb_t   TheBIOSParameterBlock;
extern  int     IsFAT32;
extern  int     Verbose;

static void
computeFileAreaSize(void)
{
        int32_t dataSectors;
        int32_t overhead;

        /*
         * Compute bytes/cluster for later reference
         */
        BytesPerCluster =  TheBIOSParameterBlock.bpb.sectors_per_cluster *
            TheBIOSParameterBlock.bpb.bytes_per_sector;

        /*
         * First we'll find total number of sectors in the file area...
         */
        if (TheBIOSParameterBlock.bpb.sectors_in_volume > 0)
                dataSectors = TheBIOSParameterBlock.bpb.sectors_in_volume;
        else
                dataSectors =
                    TheBIOSParameterBlock.bpb.sectors_in_logical_volume;

        overhead = TheBIOSParameterBlock.bpb.resv_sectors;

        RootDirSize = TheBIOSParameterBlock.bpb.num_root_entries *
            sizeof (struct pcdir);
        overhead += RootDirSize / TheBIOSParameterBlock.bpb.bytes_per_sector;

        if (TheBIOSParameterBlock.bpb.sectors_per_fat) {
                /*
                 * Good old FAT12 or FAT16
                 */
                overhead += TheBIOSParameterBlock.bpb.num_fats *
                    TheBIOSParameterBlock.bpb.sectors_per_fat;
                /*
                 * Compute this for later - when we actually pull in a copy
                 * of the FAT
                 */
                FATSize = TheBIOSParameterBlock.bpb.sectors_per_fat *
                    TheBIOSParameterBlock.bpb.bytes_per_sector;
        } else {
                /*
                 *  FAT32
                 *  I'm unsure if this is always going to work.  At one
                 *  point during the creation of this program and mkfs_pcfs
                 *  it seemed that Windows had created an fs where it had
                 *  rounded big_sectors_per_fat up to a cluster boundary.
                 *  Later, though, I encountered a problem where I wasn't
                 *  finding the root directory because I was looking in the
                 *  wrong place by doing that same roundup.  So, for now,
                 *  I'm backing off on the cluster boundary thing and just
                 *  believing what I am told.
                 */
                overhead += TheBIOSParameterBlock.bpb.num_fats *
                    TheBIOSParameterBlock.bpb32.big_sectors_per_fat;
                /*
                 * Compute this for later - when we actually pull in a copy
                 * of the FAT
                 */
                FATSize = TheBIOSParameterBlock.bpb32.big_sectors_per_fat *
                    TheBIOSParameterBlock.bpb.bytes_per_sector;
        }

        /*
         * Now change sectors to clusters.  The computed value for
         * TotalClusters is persistent for the remainder of execution.
         */
        dataSectors -= overhead;
        TotalClusters = dataSectors /
            TheBIOSParameterBlock.bpb.sectors_per_cluster;

        /*
         *  Also need to compute last cluster and offset of the first cluster
         */
        LastCluster = TotalClusters + FIRST_CLUSTER;
        FirstClusterOffset = overhead *
            TheBIOSParameterBlock.bpb.bytes_per_sector;
        FirstClusterOffset += PartitionOffset;

        /*
         * XXX this should probably be more sophisticated
         */
        if (IsFAT32)
                FATEntrySize = 32;
        else {
                if (TotalClusters <= DOS_F12MAXC)
                        FATEntrySize = 12;
                else
                        FATEntrySize = 16;
        }

        if (Verbose) {
                (void) fprintf(stderr,
                    gettext("Disk has a file area of %d "
                    "allocation units,\neach with %d sectors = %llu "
                    "bytes.\n"), TotalClusters,
                    TheBIOSParameterBlock.bpb.sectors_per_cluster,
                    (uint64_t)TotalClusters *
                    TheBIOSParameterBlock.bpb.sectors_per_cluster *
                    TheBIOSParameterBlock.bpb.bytes_per_sector);
                (void) fprintf(stderr,
                    gettext("File system overhead of %d sectors.\n"), overhead);
                (void) fprintf(stderr,
                    gettext("The last cluster is %d\n"), LastCluster);
        }
}

/*
 *  XXX - right now we aren't attempting to fix anything that looks bad,
 *      instead we just give up.
 */
void
readBPB(int fd)
{
        boot_sector_t ubpb;

        /*
         *  The BPB is the first sector of the file system
         */
        if (lseek64(fd, PartitionOffset, SEEK_SET) < 0) {
                mountSanityCheckFails();
                perror(gettext("Cannot seek to start of disk partition"));
                (void) close(fd);
                exit(7);
        }
        if (Verbose)
                (void) fprintf(stderr,
                    gettext("Reading BIOS parameter block\n"));
        if (read(fd, ubpb.buf, bpsec) < bpsec) {
                mountSanityCheckFails();
                perror(gettext("Read BIOS parameter block"));
                (void) close(fd);
                exit(2);
        }

        if (ltohs(ubpb.mb.signature) != BOOTSECSIG) {
                mountSanityCheckFails();
                (void) fprintf(stderr,
                    gettext("Bad signature on BPB. Giving up.\n"));
                exit(2);
        }

#ifdef _BIG_ENDIAN
        swap_pack_grabbpb(&TheBIOSParameterBlock, &(ubpb.bs));
#else
        (void) memcpy(&(TheBIOSParameterBlock.bpb), &(ubpb.bs.bs_front.bs_bpb),
            sizeof (TheBIOSParameterBlock.bpb));
        (void) memcpy(&(TheBIOSParameterBlock.ebpb), &(ubpb.bs.bs_ebpb),
            sizeof (TheBIOSParameterBlock.ebpb));
#endif
        if (TheBIOSParameterBlock.bpb.bytes_per_sector != 512 &&
            TheBIOSParameterBlock.bpb.bytes_per_sector != 1024 &&
            TheBIOSParameterBlock.bpb.bytes_per_sector != 2048 &&
            TheBIOSParameterBlock.bpb.bytes_per_sector != 4096) {
                mountSanityCheckFails();
                (void) fprintf(stderr,
                    gettext("Bogus bytes per sector value.  Giving up.\n"));
                exit(2);
        }
        if (!(ISP2(TheBIOSParameterBlock.bpb.sectors_per_cluster) &&
            IN_RANGE(TheBIOSParameterBlock.bpb.sectors_per_cluster,
            1, 128))) {
                mountSanityCheckFails();
                (void) fprintf(stderr,
                    gettext("Bogus sectors per cluster value.  Giving up.\n"));
                (void) close(fd);
                exit(6);
        }
        if (TheBIOSParameterBlock.bpb.sectors_per_fat == 0) {
#ifdef _BIG_ENDIAN
                swap_pack_grab32bpb(&TheBIOSParameterBlock, &(ubpb.bs));
#else
                (void) memcpy(&(TheBIOSParameterBlock.bpb32),
                    &(ubpb.bs32.bs_bpb32),
                    sizeof (TheBIOSParameterBlock.bpb32));
#endif
                IsFAT32 = 1;
        }
        if (!IsFAT32) {
                if ((TheBIOSParameterBlock.bpb.num_root_entries == 0) ||
                    ((TheBIOSParameterBlock.bpb.num_root_entries *
                    sizeof (struct pcdir)) %
                    TheBIOSParameterBlock.bpb.bytes_per_sector) != 0) {
                        mountSanityCheckFails();
                        (void) fprintf(stderr,
                            gettext("Bogus number of root entries.  "
                            "Giving up.\n"));
                        exit(2);
                }
        } else {
                if (TheBIOSParameterBlock.bpb.num_root_entries != 0) {
                        mountSanityCheckFails();
                        (void) fprintf(stderr,
                            gettext("Bogus number of root entries.  "
                            "Giving up.\n"));
                        exit(2);
                }
        }
        /*
         * In general, we would expect the number of FATs field to
         * equal 2.  Our mkfs and Windows have this as a default
         * value.  I suppose someone could override the default,
         * though, so we'll sort of arbitrarily accept any number
         * between 1 and 4 inclusive as reasonable values.
         *
         * XXX: Warn, but continue, if value is suspicious? (>2?)
         */
        if (TheBIOSParameterBlock.bpb.num_fats > 4 ||
            TheBIOSParameterBlock.bpb.num_fats < 1) {
                mountSanityCheckFails();
                (void) fprintf(stderr,
                    gettext("Bogus number of FATs.  Giving up.\n"));
                exit(2);
        }
        computeFileAreaSize();
}