/*
 * Copyright (C) 1995, 1997 Wolfgang Solfrank
 * Copyright (c) 1995 Martin Husemann
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: boot.c,v 1.27 2022/08/28 11:32:19 mlelstv Exp $");
#endif /* not lint */

#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <inttypes.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/dkio.h>

#include "ext.h"
#include "fsutil.h"

int
readboot(int dosfs, struct bootblock *boot)
{
        u_char *block;
        u_char *fsinfo;
        u_char *backup;
        int ret = FSOK;
        int i, err;
        u_int secsize;

        secsize = 0;
        err = ioctl(dosfs, DIOCGSECTORSIZE, &secsize);
        if (err != 0 || secsize == 0)
                secsize = DOSBOOTBLOCKSIZE;

        if (secsize < DOSBOOTBLOCKSIZE)
                pfatal("Invalid sector size %u\n", secsize);

        block = calloc(1, secsize);
        if (block == NULL)
                pfatal("Out of memory");
        
        if ((size_t)read(dosfs, block, secsize) != secsize) {
                perr("could not read boot block");
                free(block);
                return FSFATAL;
        }

        if (block[510] != 0x55 || block[511] != 0xaa) {
                pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
                free(block);
                return FSFATAL;
        }

        memset(boot, 0, sizeof *boot);
        boot->ValidFat = -1;

        /* decode bios parameter block */
        boot->BytesPerSec = block[11] + (block[12] << 8);
        boot->SecPerClust = block[13];
        if (boot->SecPerClust == 0 || popcount(boot->SecPerClust) != 1) {
                pfatal("Invalid cluster size: %u\n", boot->SecPerClust);
                return FSFATAL;
        }
        boot->ResSectors = block[14] + (block[15] << 8);
        boot->FATs = block[16];
        if (boot->FATs == 0) {
                pfatal("Invalid number of FATs: %u\n", boot->FATs);
                return FSFATAL;
        }
        boot->RootDirEnts = block[17] + (block[18] << 8);
        boot->Sectors = block[19] + (block[20] << 8);
        boot->Media = block[21];
        boot->FATsmall = block[22] + (block[23] << 8);
        boot->SecPerTrack = block[24] + (block[25] << 8);
        boot->Heads = block[26] + (block[27] << 8);
        boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + ((uint32_t)block[31] << 24);
        boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + ((uint32_t)block[35] << 24);

        boot->FATsecs = boot->FATsmall;

        fsinfo = calloc(2, secsize);
        if (fsinfo == NULL)
                pfatal("Out of memory");
        backup = calloc(1, secsize);
        if (backup == NULL)
                pfatal("Out of memory");

        if (!boot->RootDirEnts)
                boot->flags |= FAT32;
        if (boot->flags & FAT32) {
                boot->FATsecs = block[36] + (block[37] << 8)
                                + (block[38] << 16) + ((uint32_t)block[39] << 24);
                if (block[40] & 0x80)
                        boot->ValidFat = block[40] & 0x0f;

                /* check version number: */
                if (block[42] || block[43]) {
                        /* Correct?                             XXX */
                        pfatal("Unknown filesystem version: %x.%x",
                               block[43], block[42]);
                        return FSFATAL;
                }
                boot->RootCl = block[44] + (block[45] << 8)
                               + (block[46] << 16) + ((uint32_t)block[47] << 24);
                boot->FSInfo = block[48] + (block[49] << 8);
                boot->Backup = block[50] + (block[51] << 8);

                if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
                    != boot->FSInfo * boot->BytesPerSec
                    || (size_t)read(dosfs, fsinfo, 2 * secsize)
                    != 2 * secsize) {
                        perr("could not read fsinfo block");
                        return FSFATAL;
                }
                if (memcmp(fsinfo, "RRaA", 4)
                    || memcmp(fsinfo + 0x1e4, "rrAa", 4)
                    || fsinfo[0x1fc]
                    || fsinfo[0x1fd]
                    || fsinfo[0x1fe] != 0x55
                    || fsinfo[0x1ff] != 0xaa
                    || fsinfo[0x3fc]
                    || fsinfo[0x3fd]
                    || fsinfo[0x3fe] != 0x55
                    || fsinfo[0x3ff] != 0xaa) {
                        pwarn("Invalid signature in fsinfo block\n");
                        if (ask(0, "fix")) {
                                memcpy(fsinfo, "RRaA", 4);
                                memcpy(fsinfo + 0x1e4, "rrAa", 4);
                                fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
                                fsinfo[0x1fe] = 0x55;
                                fsinfo[0x1ff] = 0xaa;
                                fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
                                fsinfo[0x3fe] = 0x55;
                                fsinfo[0x3ff] = 0xaa;
                                if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
                                    != boot->FSInfo * boot->BytesPerSec
                                    || (size_t)write(dosfs, fsinfo, 2 * secsize)
                                    != 2 * secsize) {
                                        perr("Unable to write FSInfo");
                                        free(fsinfo);
                                        free(backup);
                                        free(block);
                                        return FSFATAL;
                                }
                                ret = FSBOOTMOD;
                        } else
                                boot->FSInfo = 0;
                }
                if (boot->FSInfo) {
                        boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
                                       + (fsinfo[0x1ea] << 16)
                                       + ((uint32_t)fsinfo[0x1eb] << 24);
                        boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
                                       + (fsinfo[0x1ee] << 16)
                                       + ((uint32_t)fsinfo[0x1ef] << 24);
                }

                if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET)
                    != boot->Backup * boot->BytesPerSec
                    || (size_t)read(dosfs, backup, secsize) != secsize) {
                        perr("could not read backup bootblock");
                        free(fsinfo);
                        free(backup);
                        free(block);
                        return FSFATAL;
                }
                backup[65] = block[65];                         /* XXX */
                if (memcmp(block + 11, backup + 11, 79)) {
                        /*
                         * XXX We require a reference that explains
                         * that these bytes need to match, or should
                         * drop the check.  gdt@ has observed
                         * filesystems that work fine under Windows XP
                         * and NetBSD that do not match, so the
                         * requirement is suspect.  For now, just
                         * print out useful information and continue.
                         */
                        pfatal("backup (block %d) mismatch with primary bootblock:\n",
                                boot->Backup);
                        for (i = 11; i < 11 + 90; i++) {
                                if (block[i] != backup[i])
                                        pfatal("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n",
                                               i, block[i], backup[i]);
                        }
                }
                /* Check backup FSInfo?                                 XXX */
        }

        free(fsinfo);
        free(backup);
        free(block);

        if (boot->FATsecs == 0) {
                pfatal("Invalid number of FAT sectors: %u\n", boot->FATsecs);
                return FSFATAL;
        }

        boot->FirstCluster = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
            / boot->BytesPerSec
            + boot->ResSectors
            + boot->FATs * boot->FATsecs;

        if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
                pfatal("Invalid sector size: %u", boot->BytesPerSec);
                return FSFATAL;
        }
        if (boot->SecPerClust == 0) {
                pfatal("Invalid cluster size: %u", boot->SecPerClust);
                return FSFATAL;
        }
        if (boot->Sectors) {
                boot->HugeSectors = 0;
                boot->NumSectors = boot->Sectors;
        } else
                boot->NumSectors = boot->HugeSectors;

        if (boot->FirstCluster + boot->SecPerClust > boot->NumSectors) {
                pfatal("Cluster offset too large (%u clusters)\n",
                    boot->FirstCluster);
                return FSFATAL;
        }

        /*
         * The number of clusters is derived from available data sectors,
         * divided by sectors per cluster.
         */
        boot->NumClusters =
            (boot->NumSectors - boot->FirstCluster) / boot->SecPerClust;

        if (boot->flags&FAT32)
                boot->ClustMask = CLUST32_MASK;
        else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
                boot->ClustMask = CLUST12_MASK;
        else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
                boot->ClustMask = CLUST16_MASK;
        else {
                pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
                       boot->NumClusters);
                return FSFATAL;
        }

        switch (boot->ClustMask) {
        case CLUST32_MASK:
                boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
                break;
        case CLUST16_MASK:
                boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
                break;
        default:
                boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
                break;
        }

        if (boot->NumFatEntries < boot->NumClusters) {
                pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
                       boot->NumClusters, boot->FATsecs);
                return FSFATAL;
        }

        /*
         * There are two reserved clusters. To avoid adding CLUST_FIRST every
         * time we perform boundary checks, we increment the NumClusters by 2,
         * which is CLUST_FIRST to denote the first out-of-range cluster number.
         */
        boot->NumClusters += CLUST_FIRST;

        boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;

        boot->NumFiles = 1;
        boot->NumFree = 0;

        return ret;
}

int
writefsinfo(int dosfs, struct bootblock *boot)
{
        u_char *fsinfo;

        fsinfo = calloc(2, boot->BytesPerSec);
        if (fsinfo == NULL)
                pfatal("Out of memory");

        if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
            != boot->FSInfo * boot->BytesPerSec
            || (size_t)read(dosfs, fsinfo, 2 * boot->BytesPerSec)
            != 2 * boot->BytesPerSec) {
                perr("could not read fsinfo block");
                free(fsinfo);
                return FSFATAL;
        }
        fsinfo[0x1e8] = (u_char)boot->FSFree;
        fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
        fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
        fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
        fsinfo[0x1ec] = (u_char)boot->FSNext;
        fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
        fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
        fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
        if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
            != boot->FSInfo * boot->BytesPerSec
            || (size_t)write(dosfs, fsinfo, 2 * boot->BytesPerSec)
            != 2 * boot->BytesPerSec) {
                perr("Unable to write FSInfo");
                free(fsinfo);
                return FSFATAL;
        }

        free(fsinfo);

        /*
         * Technically, we should return FSBOOTMOD here.
         *
         * However, since Win95 OSR2 (the first M$ OS that has
         * support for FAT32) doesn't maintain the FSINFO block
         * correctly, it has to be fixed pretty often.
         *
         * Therefore, we handle the FSINFO block only informally,
         * fixing it if necessary, but otherwise ignoring the
         * fact that it was incorrect.
         */
        return 0;
}