| 1 | /* $Id: boot.c 106061 2024-09-16 14:03:52Z vboxsync $ */
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| 2 | /** @file
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| 3 | * PC BIOS - ???
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2006-2024 Oracle and/or its affiliates.
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| 8 | *
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| 9 | * This file is part of VirtualBox base platform packages, as
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| 10 | * available from https://www.virtualbox.org.
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| 11 | *
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| 12 | * This program is free software; you can redistribute it and/or
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| 13 | * modify it under the terms of the GNU General Public License
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| 14 | * as published by the Free Software Foundation, in version 3 of the
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| 15 | * License.
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| 16 | *
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| 17 | * This program is distributed in the hope that it will be useful, but
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| 18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 20 | * General Public License for more details.
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| 21 | *
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| 22 | * You should have received a copy of the GNU General Public License
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| 23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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| 24 | *
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| 25 | * SPDX-License-Identifier: GPL-3.0-only
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| 26 | * --------------------------------------------------------------------
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| 27 | *
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| 28 | * This code is based on:
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| 29 | *
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| 30 | * ROM BIOS for use with Bochs/Plex86/QEMU emulation environment
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| 31 | *
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| 32 | * Copyright (C) 2002 MandrakeSoft S.A.
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| 33 | *
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| 34 | * MandrakeSoft S.A.
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| 35 | * 43, rue d'Aboukir
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| 36 | * 75002 Paris - France
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| 37 | * http://www.linux-mandrake.com/
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| 38 | * http://www.mandrakesoft.com/
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| 39 | *
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| 40 | * This library is free software; you can redistribute it and/or
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| 41 | * modify it under the terms of the GNU Lesser General Public
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| 42 | * License as published by the Free Software Foundation; either
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| 43 | * version 2 of the License, or (at your option) any later version.
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| 44 | *
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| 45 | * This library is distributed in the hope that it will be useful,
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| 46 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 47 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 48 | * Lesser General Public License for more details.
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| 49 | *
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| 50 | * You should have received a copy of the GNU Lesser General Public
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| 51 | * License along with this library; if not, write to the Free Software
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| 52 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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| 53 | *
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| 54 | */
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| 55 |
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| 56 | /*
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| 57 | * Oracle LGPL Disclaimer: For the avoidance of doubt, except that if any license choice
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| 58 | * other than GPL or LGPL is available it will apply instead, Oracle elects to use only
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| 59 | * the Lesser General Public License version 2.1 (LGPLv2) at this time for any software where
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| 60 | * a choice of LGPL license versions is made available with the language indicating
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| 61 | * that LGPLv2 or any later version may be used, or where a choice of which version
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| 62 | * of the LGPL is applied is otherwise unspecified.
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| 63 | */
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| 64 |
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| 65 |
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| 66 | #include <stdint.h>
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| 67 | #include <string.h>
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| 68 | #include "inlines.h"
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| 69 | #include "biosint.h"
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| 70 | #include "ebda.h"
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| 71 |
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| 72 | /* Sanity check the LAN boot segment definition. */
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| 73 | #if VBOX_LANBOOT_SEG < 0xA000
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| 74 | #error VBOX_LANBOOT_SEG incorrect!
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| 75 | #endif
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| 76 |
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| 77 | /* PnP header used with LAN boot ROMs. */
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| 78 | typedef struct {
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| 79 | uint32_t sig;
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| 80 | uint8_t revision;
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| 81 | uint8_t length;
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| 82 | uint16_t next_s;
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| 83 | uint8_t pad1;
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| 84 | uint8_t checksum;
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| 85 | uint32_t dev_id;
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| 86 | uint16_t mfg_string;
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| 87 | uint16_t prod_string;
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| 88 | uint8_t base_class;
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| 89 | uint8_t subclass;
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| 90 | uint8_t interface;
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| 91 | uint8_t dev_ind;
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| 92 | uint16_t boot_code;
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| 93 | uint16_t dv;
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| 94 | uint16_t bev;
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| 95 | uint16_t pad2;
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| 96 | uint16_t sriv;
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| 97 | } pnp_exp_t;
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| 98 |
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| 99 |
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| 100 | int read_boot_sec(uint8_t bootdrv, uint16_t segment);
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| 101 | #pragma aux read_boot_sec = \
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| 102 | "mov ax,0201h" \
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| 103 | "mov dh,0" \
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| 104 | "mov cx,1" \
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| 105 | "xor bx,bx" \
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| 106 | "int 13h" \
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| 107 | "mov ax,0" \
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| 108 | "sbb ax,0" \
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| 109 | parm [dl] [es] modify [ax bx cx dx];
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| 110 |
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| 111 | //--------------------------------------------------------------------------
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| 112 | // print_boot_device
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| 113 | // displays the boot device
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| 114 | //--------------------------------------------------------------------------
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| 115 |
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| 116 | static const char drivetypes[][10]={"Floppy","Hard Disk","CD-ROM","LAN"};
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| 117 |
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| 118 | /// @todo pass inputs as bit flags rather than bytes?
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| 119 | void print_boot_device(uint8_t cdboot, uint8_t lanboot, uint8_t drive)
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| 120 | {
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| 121 | int i;
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| 122 |
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| 123 | // cdboot contains 0 if lan/floppy/harddisk, 1 otherwise
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| 124 | // lanboot contains 0 if floppy/harddisk, 1 otherwise
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| 125 | // drive contains real/emulated boot drive
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| 126 |
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| 127 | if(cdboot)i=2; // CD-Rom
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| 128 | else if(lanboot)i=3; // LAN
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| 129 | else if((drive&0x0080)==0x00)i=0; // Floppy
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| 130 | else if((drive&0x0080)==0x80)i=1; // Hard drive
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| 131 | else return;
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| 132 |
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| 133 | BX_INFO("Booting from %s...\n",drivetypes[i]);
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| 134 | }
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| 135 |
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| 136 | //--------------------------------------------------------------------------
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| 137 | // print_boot_failure
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| 138 | // displays the reason why boot failed
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| 139 | //--------------------------------------------------------------------------
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| 140 | /// @todo pass inputs as bit flags rather than bytes?
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| 141 | void print_boot_failure(uint8_t cdboot, uint8_t lanboot, uint8_t drive,
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| 142 | uint8_t reason, uint8_t lastdrive)
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| 143 | {
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| 144 | uint16_t drivenum = drive&0x7f;
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| 145 |
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| 146 | // cdboot: 1 if boot from cd, 0 otherwise
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| 147 | // lanboot: 1 if boot from lan, 0 otherwise
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| 148 | // drive : drive number
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| 149 | // reason: 0 signature check failed, 1 read error
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| 150 | // lastdrive: 1 boot drive is the last one in boot sequence
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| 151 |
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| 152 | if (cdboot)
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| 153 | BX_INFO("Boot from %s failed\n",drivetypes[2]);
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| 154 | else if (lanboot)
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| 155 | BX_INFO("Boot from %s failed\n",drivetypes[3]);
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| 156 | else if (drive & 0x80)
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| 157 | BX_INFO("Boot from %s %d failed\n", drivetypes[1],drivenum);
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| 158 | else
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| 159 | BX_INFO("Boot from %s %d failed\n", drivetypes[0],drivenum);
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| 160 |
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| 161 | if (lastdrive==1) {
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| 162 | if (reason==0)
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| 163 | BX_INFO_CON("No bootable medium found!\n");
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| 164 | else
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| 165 | BX_INFO_CON("Could not read from the boot medium!\n");
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| 166 | BX_INFO_CON("Please insert a bootable medium and reboot.\n");
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| 167 | }
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| 168 | }
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| 169 |
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| 170 | //--------------------------------------------------------------------------
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| 171 | // print_cdromboot_failure
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| 172 | // displays the reason why boot failed
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| 173 | //--------------------------------------------------------------------------
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| 174 | void print_cdromboot_failure(uint16_t code)
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| 175 | {
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| 176 | BX_INFO("CDROM boot failure code : %04x\n",code);
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| 177 | return;
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| 178 | }
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| 179 |
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| 180 |
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| 181 | #define BOOT_CHK_WORDS 8
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| 182 |
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| 183 | /* Check if the first n words of a boot sector
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| 184 | * are identical. Only consider the boot sector
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| 185 | * valid if they're not.
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| 186 | */
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| 187 | static int valid_bootsect(uint16_t __far *boot)
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| 188 | {
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| 189 | int i;
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| 190 | uint16_t word1;
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| 191 |
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| 192 | word1 = boot[0];
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| 193 | for (i = 1; i < BOOT_CHK_WORDS; ++i) {
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| 194 | if (word1 != boot[i])
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| 195 | break;
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| 196 | }
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| 197 |
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| 198 | return i != BOOT_CHK_WORDS;
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| 199 | }
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| 200 |
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| 201 | // returns bootsegment in ax, drive in bl
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| 202 | uint32_t BIOSCALL int19_function(uint8_t bseqnr)
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| 203 | {
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| 204 | /// @todo common code for getting the EBDA segment
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| 205 | uint16_t ebda_seg=read_word(0x0040,0x000E);
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| 206 | uint16_t bootseq;
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| 207 | uint8_t bootdrv;
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| 208 | uint8_t bootcd;
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| 209 | uint8_t bootlan;
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| 210 | uint8_t bootchk;
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| 211 | uint16_t bootseg;
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| 212 | uint16_t status;
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| 213 | uint8_t lastdrive=0;
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| 214 |
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| 215 | // if BX_ELTORITO_BOOT is not defined, old behavior
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| 216 | // check bit 5 in CMOS reg 0x2d. load either 0x00 or 0x80 into DL
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| 217 | // in preparation for the initial INT 13h (0=floppy A:, 0x80=C:)
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| 218 | // 0: system boot sequence, first drive C: then A:
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| 219 | // 1: system boot sequence, first drive A: then C:
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| 220 | // else BX_ELTORITO_BOOT is defined
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| 221 | // CMOS regs 0x3D and 0x38 contain the boot sequence:
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| 222 | // CMOS reg 0x3D & 0x0f : 1st boot device
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| 223 | // CMOS reg 0x3D & 0xf0 : 2nd boot device
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| 224 | // CMOS reg 0x38 & 0xf0 : 3rd boot device
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| 225 | // CMOS reg 0x3C & 0x0f : 4th boot device
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| 226 | // boot device codes:
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| 227 | // 0x00 : not defined
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| 228 | // 0x01 : first floppy
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| 229 | // 0x02 : first harddrive
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| 230 | // 0x03 : first cdrom
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| 231 | // 0x04 : local area network
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| 232 | // else : boot failure
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| 233 |
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| 234 | // Get the boot sequence
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| 235 | #if BX_ELTORITO_BOOT
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| 236 | bootseq=inb_cmos(0x3d);
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| 237 | bootseq|=((inb_cmos(0x38) & 0xf0) << 4);
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| 238 | bootseq|=((inb_cmos(0x3c) & 0x0f) << 12);
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| 239 | if (read_byte(ebda_seg, (uint16_t)&EbdaData->uForceBootDevice))
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| 240 | bootseq = read_byte(ebda_seg, (uint16_t)&EbdaData->uForceBootDevice);
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| 241 | /* Boot delay hack. */
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| 242 | if (bseqnr == 1)
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| 243 | delay_boot((inb_cmos(0x3c) & 0xf0) >> 4); /* Implemented in logo.c */
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| 244 |
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| 245 | if (bseqnr==2) bootseq >>= 4;
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| 246 | if (bseqnr==3) bootseq >>= 8;
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| 247 | if (bseqnr==4) bootseq >>= 12;
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| 248 | if (bootseq<0x10) lastdrive = 1;
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| 249 | bootdrv=0x00; bootcd=0;
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| 250 | bootlan=0;
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| 251 | BX_INFO("Boot : bseqnr=%d, bootseq=%x\r\n",bseqnr, bootseq);
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| 252 |
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| 253 | switch(bootseq & 0x0f) {
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| 254 | case 0x01:
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| 255 | bootdrv=0x00;
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| 256 | bootcd=0;
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| 257 | break;
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| 258 | case 0x02:
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| 259 | {
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| 260 | // Get the Boot drive.
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| 261 | uint8_t boot_drive = read_byte(ebda_seg, (uint16_t)&EbdaData->uForceBootDrive);
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| 262 |
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| 263 | bootdrv = boot_drive + 0x80;
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| 264 | bootcd=0;
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| 265 | break;
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| 266 | }
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| 267 | case 0x03:
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| 268 | bootdrv=0x00;
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| 269 | bootcd=1;
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| 270 | break;
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| 271 | case 0x04: bootlan=1; break;
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| 272 | default: return 0x00000000;
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| 273 | }
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| 274 | #else
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| 275 | bootseq=inb_cmos(0x2d);
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| 276 |
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| 277 | if (bseqnr==2) {
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| 278 | bootseq ^= 0x20;
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| 279 | lastdrive = 1;
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| 280 | }
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| 281 | bootdrv=0x00; bootcd=0;
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| 282 | if((bootseq&0x20)==0) bootdrv=0x80;
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| 283 | #endif // BX_ELTORITO_BOOT
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| 284 |
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| 285 | #if BX_ELTORITO_BOOT
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| 286 | // We have to boot from cd
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| 287 | if (bootcd != 0) {
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| 288 | status = cdrom_boot();
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| 289 |
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| 290 | // If failure
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| 291 | if ( (status & 0x00ff) !=0 ) {
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| 292 | print_cdromboot_failure(status);
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| 293 | print_boot_failure(bootcd, bootlan, bootdrv, 1, lastdrive);
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| 294 | return 0x00000000;
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| 295 | }
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| 296 |
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| 297 | bootseg = read_word(ebda_seg,(uint16_t)&EbdaData->cdemu.load_segment);
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| 298 | bootdrv = (uint8_t)(status>>8);
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| 299 | }
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| 300 |
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| 301 | #endif // BX_ELTORITO_BOOT
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| 302 |
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| 303 | // Check for boot from LAN first
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| 304 | if (bootlan == 1) {
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| 305 | uint8_t __far *fplan;
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| 306 |
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| 307 | fplan = MK_FP(VBOX_LANBOOT_SEG, 0);
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| 308 | if (*(uint16_t __far *)fplan == 0xaa55) {
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| 309 | pnp_exp_t __far *pnps;
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| 310 | uint32_t manuf;
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| 311 | void (__far *netboot_entry)(void);
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| 312 |
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| 313 | // This is NOT a generic PnP implementation, but an Etherboot-specific hack.
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| 314 | pnps = (void __far *)(fplan + *(uint16_t __far *)(fplan + 0x1a));
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| 315 | if (pnps->sig == 0x506e5024/* '$PnP' */) {
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| 316 | // Found PnP signature
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| 317 | manuf = *(uint32_t __far *)(fplan + pnps->mfg_string);
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| 318 | if (manuf == 0x65687445/* 'Ethe' */) {
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| 319 | // Found Etherboot ROM
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| 320 | print_boot_device(bootcd, bootlan, bootdrv);
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| 321 | netboot_entry = (void __far *)(fplan + 6);
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| 322 | netboot_entry();
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| 323 | }
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| 324 | else
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| 325 | {
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| 326 | //Found Normal Pnp ROM
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| 327 | print_boot_device(bootcd, bootlan, bootdrv);
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| 328 | int_enable(); /* Disabled as we were invoked via INT instruction. */
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| 329 | netboot_entry = (void __far *)(fplan + pnps->bev);
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| 330 | netboot_entry();
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| 331 | }
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| 332 | }
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| 333 | }
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| 334 |
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| 335 | // boot from LAN will not return if successful.
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| 336 | print_boot_failure(bootcd, bootlan, bootdrv, 1, lastdrive);
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| 337 | return 0x00000000;
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| 338 | }
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| 339 |
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| 340 | // We have to boot from harddisk or floppy
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| 341 | if (bootcd == 0 && bootlan == 0) {
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| 342 | bootseg=0x07c0;
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| 343 |
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| 344 | status = read_boot_sec(bootdrv,bootseg);
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| 345 | if (status != 0) {
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| 346 | print_boot_failure(bootcd, bootlan, bootdrv, 1, lastdrive);
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| 347 | return 0x00000000;
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| 348 | }
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| 349 | }
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| 350 |
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| 351 | // There is *no* requirement whatsoever for a valid floppy boot sector
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| 352 | // to have a 55AAh signature. UNIX boot floppies typically have no such
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| 353 | // signature. In general, it is impossible to tell a valid bootsector
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| 354 | // from an invalid one.
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| 355 | // NB: It is somewhat common for failed OS installs to have the
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| 356 | // 0x55AA signature and a valid partition table but zeros in the
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| 357 | // rest of the boot sector. We check the first few words; if identical,
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| 358 | // the boot sector is extremely unlikely to be valid.
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| 359 | if (bootdrv != 0) bootchk = 0;
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| 360 | else bootchk = 1; /* disable 0x55AA signature check on drive A: */
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| 361 |
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| 362 | #if BX_ELTORITO_BOOT
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| 363 | // if boot from cd, no signature check
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| 364 | if (bootcd != 0)
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| 365 | bootchk = 1;
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| 366 | #endif // BX_ELTORITO_BOOT
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| 367 |
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| 368 | if (!valid_bootsect(MK_FP(bootseg,0))
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| 369 | || (bootchk == 0 && read_word(bootseg,0x1fe) != 0xaa55))
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| 370 | {
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| 371 | print_boot_failure(bootcd, bootlan, bootdrv, 0, lastdrive);
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| 372 | return 0x00000000;
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| 373 | }
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| 374 |
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| 375 | #if BX_ELTORITO_BOOT
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| 376 | // Print out the boot string
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| 377 | print_boot_device(bootcd, bootlan, bootdrv);
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| 378 | #else // BX_ELTORITO_BOOT
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| 379 | print_boot_device(0, bootlan, bootdrv);
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| 380 | #endif // BX_ELTORITO_BOOT
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| 381 |
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| 382 | // return the boot segment
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| 383 | return (((uint32_t)bootdrv) << 16) + bootseg;
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| 384 | }
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| 385 |
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