| 1 | ; Project name : XTIDE Universal BIOS
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| 2 | ; Description : Int 19h Handler (Boot Loader).
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| 3 |
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| 4 | ;
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| 5 | ; XTIDE Universal BIOS and Associated Tools
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| 6 | ; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2012 by XTIDE Universal BIOS Team.
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| 7 | ;
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| 8 | ; This program is free software; you can redistribute it and/or modify
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| 9 | ; it under the terms of the GNU General Public License as published by
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| 10 | ; the Free Software Foundation; either version 2 of the License, or
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| 11 | ; (at your option) any later version.
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| 12 | ;
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| 13 | ; This program is distributed in the hope that it will be useful,
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| 14 | ; but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 15 | ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 16 | ; GNU General Public License for more details.
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| 17 | ; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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| 18 | ;
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| 19 |
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| 20 | ; Section containing code
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| 21 | SECTION .text
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| 22 |
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| 23 | ;--------------------------------------------------------------------
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| 24 | ; Int19h_BootLoaderHandler
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| 25 | ; Parameters:
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| 26 | ; Nothing
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| 27 | ; Returns:
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| 28 | ; Never returns (loads operating system)
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| 29 | ;--------------------------------------------------------------------
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| 30 | Int19h_BootLoaderHandler:
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| 31 | sti ; Enable interrupts
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| 32 | cld ; String instructions to increment pointers
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| 33 | LOAD_BDA_SEGMENT_TO es, ax ; Load BDA segment (zero) to ES
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| 34 | ; Fall to .PrepareBootLoaderStack
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| 35 |
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| 36 |
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| 37 | ;--------------------------------------------------------------------
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| 38 | ; Drive detection and boot menu use lots of stack so it is
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| 39 | ; wise to relocate stack. Otherwise something important from
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| 40 | ; interrupt vectors are likely corrupted, likely our own DPTs if
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| 41 | ; they are located to 30:0h.
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| 42 | ;
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| 43 | ; .PrepareBootLoaderStack
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| 44 | ; Parameters:
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| 45 | ; ES: BDA and interrupt vector segment (zero)
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| 46 | ; Returns:
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| 47 | ; Never returns (loads operating system)
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| 48 | ;--------------------------------------------------------------------
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| 49 | .PrepareBootLoaderStack:
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| 50 | STORE_POST_STACK_POINTER
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| 51 | SWITCH_TO_BOOT_MENU_STACK
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| 52 | ; Fall to .InitializeDisplay
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| 53 |
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| 54 |
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| 55 | ;--------------------------------------------------------------------
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| 56 | ; .InitializeDisplay
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| 57 | ; Parameters:
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| 58 | ; ES: BDA and interrupt vector segment (zero)
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| 59 | ; Returns:
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| 60 | ; Never returns (loads operating system)
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| 61 | ;--------------------------------------------------------------------
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| 62 | .InitializeDisplay:
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| 63 | ; Change display mode if necessary
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| 64 | mov ax, [cs:ROMVARS.wDisplayMode] ; AH 00h = Set Video Mode
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| 65 | cmp al, DEFAULT_TEXT_MODE
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| 66 | je SHORT .InitializeDisplayLibrary
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| 67 | int BIOS_VIDEO_INTERRUPT_10h
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| 68 | .InitializeDisplayLibrary:
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| 69 | call DetectPrint_InitializeDisplayContext
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| 70 | ; Fall to .InitializeBiosAndDetectDrives
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| 71 |
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| 72 |
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| 73 | ;--------------------------------------------------------------------
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| 74 | ; .InitializeBiosAndDetectDrives
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| 75 | ; Parameters:
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| 76 | ; ES: BDA and interrupt vector segment (zero)
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| 77 | ; Returns:
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| 78 | ; DS: RAMVARS segment
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| 79 | ;--------------------------------------------------------------------
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| 80 | %ifdef MODULE_HOTKEYS
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| 81 | call TimerTicks_ReadFromBdaToAX
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| 82 | add ax, MIN_TIME_TO_DISPLAY_HOTKEY_BAR
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| 83 | mov [es:BOOTVARS.hotkeyVars+HOTKEYVARS.wTimeToClose], ax
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| 84 | %endif
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| 85 |
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| 86 | call Initialize_AndDetectDrives
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| 87 |
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| 88 | %ifdef MODULE_HOTKEYS
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| 89 | .WaitUntilTimeToCloseHotkeyBar:
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| 90 | call TimerTicks_ReadFromBdaToAX
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| 91 | cmp ax, [es:BOOTVARS.hotkeyVars+HOTKEYVARS.wTimeToClose]
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| 92 | jb SHORT .WaitUntilTimeToCloseHotkeyBar
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| 93 | %endif
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| 94 | ; Fall to SelectDriveToBootFrom
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| 95 |
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| 96 |
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| 97 | ;--------------------------------------------------------------------
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| 98 | ; SelectDriveToBootFrom
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| 99 | ; Parameters:
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| 100 | ; DS: RAMVARS segment
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| 101 | ; ES: BDA and interrupt vector segment (zero)
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| 102 | ; Returns:
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| 103 | ; Never returns (loads operating system)
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| 104 | ;--------------------------------------------------------------------
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| 105 | SelectDriveToBootFrom:
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| 106 | %ifdef MODULE_HOTKEYS
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| 107 | call HotkeyBar_UpdateDuringDriveDetection
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| 108 |
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| 109 | %ifdef MODULE_BOOT_MENU
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| 110 | mov di, BOOTVARS.hotkeyVars+HOTKEYVARS.bScancode
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| 111 | cmp BYTE [es:di], BOOT_MENU_HOTKEY_SCANCODE
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| 112 | jne SHORT .DoNotDisplayBootMenu
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| 113 |
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| 114 | ; Stop blinking the Boot Menu hotkey and display menu
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| 115 | mov BYTE [es:di], 0
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| 116 | call HotkeyBar_DrawToTopOfScreen
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| 117 | call BootMenu_DisplayAndStoreSelectionAsHotkey
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| 118 | .DoNotDisplayBootMenu:
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| 119 | %endif
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| 120 |
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| 121 | ; Check if ROM boot (INT 18h) wanted
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| 122 | cmp BYTE [es:BOOTVARS.hotkeyVars+HOTKEYVARS.bScancode], ROM_BOOT_HOTKEY_SCANCODE
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| 123 | je SHORT JumpToBootSector_or_RomBoot ; CF clear so ROM boot
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| 124 |
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| 125 | ; Get Primary boot drive number to DL
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| 126 | call HotkeyBar_GetPrimaryBootDriveNumberToDL
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| 127 | %else
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| 128 | xor dl, dl ; Try to boot from Floppy Drive A
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| 129 | %endif ; MODULE_HOTKEYS
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| 130 |
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| 131 | ; Try to boot from Primary boot drive (00h by default)
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| 132 | call TryToBootFromPrimaryOrSecondaryBootDevice
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| 133 | jc SHORT JumpToBootSector_or_RomBoot
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| 134 |
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| 135 | ; Try to boot from Secondary boot device (80h by default)
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| 136 | %ifdef MODULE_HOTKEYS
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| 137 | call HotkeyBar_GetSecondaryBootDriveNumberToDL
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| 138 | %else
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| 139 | mov dl, 80h ; Try to boot from Hard Drive C
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| 140 | %endif
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| 141 | call TryToBootFromPrimaryOrSecondaryBootDevice
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| 142 |
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| 143 | %ifdef MODULE_BOOT_MENU
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| 144 | ; Force Boot Menu hotkey to display boot menu
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| 145 | mov BYTE [es:BOOTVARS.hotkeyVars+HOTKEYVARS.bScancode], BOOT_MENU_HOTKEY_SCANCODE
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| 146 | jnc SHORT SelectDriveToBootFrom
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| 147 | %endif
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| 148 | ; Fall to JumpToBootSector_or_RomBoot
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| 149 |
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| 150 |
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| 151 | ;--------------------------------------------------------------------
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| 152 | ; JumpToBootSector_or_RomBoot
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| 153 | ;
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| 154 | ; Switches back to the POST stack, clears the DS and ES registers,
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| 155 | ; and either jumps to the MBR (Master Boot Record) that was just read,
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| 156 | ; or calls the ROM's boot routine on interrupt 18.
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| 157 | ;
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| 158 | ; Parameters:
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| 159 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 160 | ; CF: Set for Boot Sector Boot
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| 161 | ; Clear for ROM Boot
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| 162 | ; ES:BX: (if CF set) Ptr to boot sector
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| 163 | ;
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| 164 | ; Returns:
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| 165 | ; Never returns
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| 166 | ;--------------------------------------------------------------------
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| 167 | JumpToBootSector_or_RomBoot:
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| 168 | mov cx, es ; Preserve MBR segment (can't push because of stack change)
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| 169 | mov ax, 0 ; NOTE: can't use XOR (LOAD_BDA_SEGMENT_TO) as it impacts CF
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| 170 | SWITCH_BACK_TO_POST_STACK
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| 171 |
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| 172 | ; clear segment registers before boot sector or rom call
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| 173 | mov ds, ax
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| 174 | mov es, ax
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| 175 | %ifdef USE_386
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| 176 | mov fs, ax
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| 177 | mov gs, ax
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| 178 | %endif
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| 179 | jnc SHORT .romboot
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| 180 |
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| 181 | ; jump to boot sector
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| 182 | push cx ; sgment address for MBR
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| 183 | push bx ; offset address for MBR
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| 184 | retf ; NOTE: DL is set to the drive number
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| 185 |
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| 186 | ; Boot by calling INT 18h (ROM Basic of ROM DOS)
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| 187 | .romboot:
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| 188 | int BIOS_BOOT_FAILURE_INTERRUPT_18h ; Never returns
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| 189 |
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| 190 |
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| 191 | ;--------------------------------------------------------------------
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| 192 | ; TryToBootFromPrimaryOrSecondaryBootDevice
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| 193 | ; Parameters
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| 194 | ; DL: Drive selected as boot device
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| 195 | ; DS: RAMVARS segment
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| 196 | ; ES: BDA and interrupt vector segment (zero)
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| 197 | ; Returns:
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| 198 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 199 | ; CF: Set for Boot Sector Boot
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| 200 | ; Clear for ROM Boot
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| 201 | ; ES:BX: (if CF set) Ptr to boot sector
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| 202 | ; Corrupts registers:
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| 203 | ; AX, CX, DH, SI, DI, (DL if failed to read boot sector)
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| 204 | ;--------------------------------------------------------------------
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| 205 | %ifndef MODULE_HOTKEYS
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| 206 | TryToBootFromPrimaryOrSecondaryBootDevice EQU BootSector_TryToLoadFromDriveDL
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| 207 |
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| 208 | %else
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| 209 | TryToBootFromPrimaryOrSecondaryBootDevice:
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| 210 | call DriveXlate_SetDriveToSwap
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| 211 | call DriveXlate_ToOrBack
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| 212 | jmp BootSector_TryToLoadFromDriveDL
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| 213 | %endif
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