mirror of
https://github.com/CloverHackyColor/CloverBootloader.git
synced 2024-12-25 16:37:42 +01:00
598 lines
14 KiB
ArmAsm
598 lines
14 KiB
ArmAsm
; Copyright (c) 2003 Apple Computer, Inc. All rights reserved.
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;
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; @APPLE_LICENSE_HEADER_START@
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;
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; Portions Copyright (c) 2003 Apple Computer, Inc. All Rights
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; Reserved. This file contains Original Code and/or Modifications of
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; Original Code as defined in and that are subject to the Apple Public
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; Source License Version 2.0 (the "License"). You may not use this file
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; except in compliance with the License. Please obtain a copy of the
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; License at http://www.apple.com/publicsource and read it before using
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; this file.
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;
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; The Original Code and all software distributed under the License are
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; distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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; EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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; INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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; FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT. Please see the
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; License for the specific language governing rights and limitations
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; under the License.
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;
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; @APPLE_LICENSE_HEADER_END@
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; nasm cdboot.s -o cdboot
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;
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; This version of cdboot loads 256k of data.
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;
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; Modifications by Tamás Kosárszky on 2008-10-20
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;
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;
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; Set to 1 to enable obscure debug messages.
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;
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DEBUG EQU 0
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;
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; Set to 1 to enable unused code.
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;
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UNUSED EQU 0
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;
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; Set to 1 to enable verbose mode.
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;
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VERBOSE EQU 1
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;
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; Various constants.
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;
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NULL EQU 0
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CR EQU 0x0D
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LF EQU 0x0A
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;
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; Macros.
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;
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%macro jmpabs 1
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push WORD %1
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ret
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%endmacro
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%macro DebugCharMacro 1
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pushad
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mov al, %1
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call print_char
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call getc
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popad
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%endmacro
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%macro DebugPauseMacro 0
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push ax
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call getc
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pop ax
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%endmacro
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%macro PrintCharMacro 1
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pushad
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mov al, %1
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call print_char
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popad
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%endmacro
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%macro PutCharMacro 1
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call print_char
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%endmacro
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%macro PrintHexMacro 1
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; call print_hex
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%endmacro
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%macro PrintString 1
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mov si, %1
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call print_string
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%endmacro
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%macro LogString 1
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mov di, %1
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call log_string
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%endmacro
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%if DEBUG
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%define DebugChar(x) DebugCharMacro x
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%define DebugPause(x) DebugPauseMacro
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%define PrintChar(x) PrintCharMacro x
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%define PutChar(x) PutCharMacro
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%define PrintHex(x) ;PrintHexMacro x
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%else
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%define DebugChar(x)
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%define DebugPause(x)
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%define PrintChar(x)
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%define PutChar(x)
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%define PrintHex(x)
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%endif
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maxSectorCount EQU 8 ; maximum sector count for readSectors
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CDBootSizeMagic EQU 0xDEADFACE ; indicates if the size field was not specificed
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; at build time.
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kSectorBytes EQU 2048 ; sector size in bytes
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kBoot2Size EQU 65024 ; default load size for boot2
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kBoot2MaxSize EQU (472*1024-512) ;458240 ; max size for boot2
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kBoot2Address EQU 0x0200 ; boot2 load address
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kBoot2Segment EQU 0x2000 ; boot2 load segment
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kBoot0Stack EQU 0xFFF0 ; boot0 stack pointer
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kReadBuffer EQU 0x1000 ; disk data buffer address
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kVolSectorOffset EQU 0x47 ; offset in buffer of sector number
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; in volume descriptor
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kBootSectorOffset EQU 0x28 ; offset in boot catalog
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; of sector number to load boot file
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kBootCountOffset EQU 0x26 ; offset in boot catalog
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; of number of sectors to read
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kCDBootSizeOffset EQU 2048 - 4 ; the file size can be found at the
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; last dword of this sector.
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;--------------------------------------------------------------------------
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; Start of text segment.
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SEGMENT .text
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ORG 0x7C00
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;--------------------------------------------------------------------------
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; Boot code is loaded at 0:7C00h.
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;
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start:
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cli
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jmp 0:start1
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times 8-($-$$) nop ; Put boot information table at offset 8
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; El Torito boot information table, filled in by the
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; mkisofs -boot-info-table option, if used.
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bi_pvd: dd 0 ; LBA of primary volume descriptor
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bi_file: dd 0 ; LBA of boot file
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bi_length: dd 0 ; Length of boot file
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bi_csum: dd 0 ; Checksum of boot file
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bi_reserved: times 10 dd 0 ; Reserved
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start1:
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xor ax, ax ; zero %ax
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mov ss, ax ; setup the
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mov sp, kBoot0Stack ; stack
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sti
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cld ; increment SI after each lodsb call
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mov ds, ax ; setup the
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mov es, ax ; data segments
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%if VERBOSE
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LogString(init_str)
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%endif
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;; BIOS boot drive is in DL
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mov [gBIOSDriveNumber], dl ; save BIOS drive number
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DebugChar('!')
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DebugPause()
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%if 0 ;DEBUG
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mov eax, [kBoot2LoadAddr]
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call print_hex
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call getc
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%endif
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;;
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;; The BIOS likely didn't load the rest of the booter,
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;; so we have to fetch it ourselves.
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;;
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mov edx, kReadBuffer
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mov al, 1
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mov ecx, 17
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call readLBA
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jc NEAR error
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DebugChar('A')
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mov ecx, [kReadBuffer + kVolSectorOffset]
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%if 0 ;DEBUG
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mov eax, ecx
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call print_hex
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DebugPause()
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%endif
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mov al, 1
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call readLBA
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jc NEAR error
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;; Now we have the boot catalog in the buffer.
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;; Really we should look at the validation entry, but oh well.
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DebugChar('B')
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mov ecx, [kReadBuffer + kBootSectorOffset]
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mov al, 1
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call readLBA ; reading this boot sector
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inc ecx ; skip the first sector which is what we are in
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%if 0 ;DEBUG
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mov eax, ecx
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call print_hex
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DebugPause()
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%endif
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;
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; Testing cdboot size
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;
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mov eax, [kReadBuffer + kCDBootSizeOffset]
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or eax, eax
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jz .useDefaultSize ; use the default size if zero
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cmp eax, CDBootSizeMagic
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je .useDefaultSize ; use the default size if equals to magic
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cmp eax, kBoot2MaxSize
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jbe .calcSectors ; use the actual size
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.useDefaultSize:
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mov eax, kBoot2Size
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%if VERBOSE
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LogString(defaultsize_str)
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%endif
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.calcSectors:
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%if VERBOSE
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LogString(size_str)
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; call print_hex
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%endif
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add eax, kSectorBytes - 1 ; adjust size before unit conversion
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shr eax, 11 ; convert file size to CD sector unit
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%if VERBOSE
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LogString(read_str)
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; call print_hex
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%endif
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%if VERBOSE
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LogString(loading_str)
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%endif
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mov edx, (kBoot2Segment << 4) + kBoot2Address
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call readSectors
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jc error
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DebugChar('C')
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%if 0 ;DEBUG
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mov eax, [es:kBoot2Address]
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call print_hex
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DebugPause()
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%endif
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DebugChar('X')
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DebugPause()
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;; Jump to newly-loaded booter
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%if VERBOSE
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LogString(done_str)
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%endif
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%if UNUSED
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LogString(keypress_str)
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call getc
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%endif
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mov dl, [gBIOSDriveNumber] ; load BIOS drive number
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jmp kBoot2Segment:kBoot2Address
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error:
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%if VERBOSE
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LogString(error_str)
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%endif
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.loop:
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hlt
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jmp .loop
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;;
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;; Support functions
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;;
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;--------------------------------------------------------------------------
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; readSectors - Reads more than 127 sectors using LBA addressing.
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;
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; Arguments:
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; AX = number of 2048-byte sectors to read (valid from 1-320).
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; EDX = pointer to where the sectors should be stored.
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; ECX = sector offset in partition
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;
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; Returns:
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; CF = 0 success
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; 1 error
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;
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readSectors:
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pushad
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mov bx, ax
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.loop:
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mov al, '.'
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call print_char
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xor eax, eax ; EAX = 0
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mov al, bl ; assume we reached the last block.
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cmp bx, maxSectorCount ; check if we really reached the last block
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jb .readBlock ; yes, BX < MaxSectorCount
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mov al, maxSectorCount ; no, read MaxSectorCount
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.readBlock:
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call readLBA
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jc .exit
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sub bx, ax ; decrease remaning sectors with the read amount
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jz .exit ; exit if no more sectors left to be loaded
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add ecx, eax ; adjust LBA sector offset
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shl eax, 11 ; convert CD sectors to bytes
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add edx, eax ; adjust target memory location
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jmp .loop ; read remaining sectors
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.exit:
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popad
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ret
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;--------------------------------------------------------------------------
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; readLBA - Read sectors from a partition using LBA addressing.
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;
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; Arguments:
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; AL = number of 512-byte sectors to read (valid from 1-127).
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; EDX = pointer to where the sectors should be stored.
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; ECX = sector offset in partition
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; [gBIOSDriveNumber] = drive number (0x80 + unit number)
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;
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; Returns:
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; CF = 0 success
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; 1 error
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;
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readLBA:
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pushad ; save all registers
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push es ; save ES
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mov bp, sp ; save current SP
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;
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; Convert EDX to segment:offset model and set ES:BX
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;
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; Some BIOSes do not like offset to be negative while reading
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; from hard drives. This usually leads to "boot1: error" when trying
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; to boot from hard drive, while booting normally from USB flash.
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; The routines, responsible for this are apparently different.
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; Thus we split linear address slightly differently for these
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; capricious BIOSes to make sure offset is always positive.
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;
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mov bx, dx ; save offset to BX
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and bh, 0x0f ; keep low 12 bits
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shr edx, 4 ; adjust linear address to segment base
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xor dl, dl ; mask low 8 bits
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mov es, dx ; save segment to ES
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;
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; Create the Disk Address Packet structure for the
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; INT13/F42 (Extended Read Sectors) on the stack.
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;
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; push DWORD 0 ; offset 12, upper 32-bit LBA
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push ds ; For sake of saving memory,
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push ds ; push DS register, which is 0.
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push ecx
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push es ; offset 6, memory segment
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push bx ; offset 4, memory offset
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xor ah, ah ; offset 3, must be 0
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push ax ; offset 2, number of sectors
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push WORD 16 ; offset 0-1, packet size
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;
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; INT13 Func 42 - Extended Read Sectors
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;
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; Arguments:
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; AH = 0x42
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; [gBIOSDriveNumber] = drive number (0x80 + unit number)
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; DS:SI = pointer to Disk Address Packet
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;
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; Returns:
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; AH = return status (sucess is 0)
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; carry = 0 success
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; 1 error
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;
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; Packet offset 2 indicates the number of sectors read
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; successfully.
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;
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mov dl, [gBIOSDriveNumber] ; load BIOS drive number
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mov si, sp
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mov ah, 0x42
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int 0x13
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jnc .exit
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DebugChar('R') ; indicate INT13/F42 error
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;
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; Issue a disk reset on error.
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; Should this be changed to Func 0xD to skip the diskette controller
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; reset?
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;
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%if VERBOSE
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LogString(readerror_str)
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mov eax, ecx
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; call print_hex
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%endif
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xor ax, ax ; Func 0
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int 0x13 ; INT 13
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stc ; set carry to indicate error
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.exit:
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mov sp, bp ; restore SP
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pop es ; restore ES
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popad
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ret
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;--------------------------------------------------------------------------
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; Write a string with 'cdboot: ' prefix to the console.
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;
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; Arguments:
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; ES:DI pointer to a NULL terminated string.
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;
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; Clobber list:
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; DI
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;
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log_string:
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pushad
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push di
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mov si, log_title_str
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call print_string
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pop si
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call print_string
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popad
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ret
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;-------------------------------------------------------------------------
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; Write a string to the console.
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;
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; Arguments:
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; DS:SI pointer to a NULL terminated string.
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;
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; Clobber list:
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; AX, BX, SI
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;
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print_string:
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mov bx, 1 ; BH=0, BL=1 (blue)
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.loop:
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lodsb ; load a byte from DS:SI into AL
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cmp al, 0 ; Is it a NULL?
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je .exit ; yes, all done
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mov ah, 0xE ; INT10 Func 0xE
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int 0x10 ; display byte in tty mode
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jmp .loop
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.exit:
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ret
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;%if DEBUG
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;--------------------------------------------------------------------------
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; Write the 4-byte value to the console in hex.
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;
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; Arguments:
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; EAX = Value to be displayed in hex.
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;
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%if 0
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print_hex:
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pushad
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mov cx, WORD 4
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bswap eax
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.loop:
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push ax
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ror al, 4
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call print_nibble ; display upper nibble
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pop ax
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call print_nibble ; display lower nibble
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ror eax, 8
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loop .loop
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%if UNUSED
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mov al, 10 ; carriage return
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call print_char
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mov al, 13
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call print_char
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%endif ; UNUSED
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popad
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ret
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print_nibble:
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and al, 0x0f
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add al, '0'
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cmp al, '9'
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jna .print_ascii
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add al, 'A' - '9' - 1
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.print_ascii:
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call print_char
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ret
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%endif
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;--------------------------------------------------------------------------
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; getc - wait for a key press
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;
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getc:
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pushad
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mov ah, 0
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int 0x16
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popad
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ret
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;--------------------------------------------------------------------------
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; Write a ASCII character to the console.
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;
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; Arguments:
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; AL = ASCII character.
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;
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print_char:
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pushad
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mov bx, 1 ; BH=0, BL=1 (blue)
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mov ah, 0x0e ; bios INT 10, Function 0xE
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int 0x10 ; display byte in tty mode
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popad
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ret
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;--------------------------------------------------------------------------
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; Static data.
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;
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%if VERBOSE
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log_title_str db CR, LF, 'cdboot: ', NULL
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init_str db 'init', NULL
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defaultsize_str db 'using default size', NULL
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size_str db 'file size: ', NULL
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read_str db 'reading sectors: ', NULL
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loading_str db 'loading', NULL
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done_str db 'done', NULL
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readerror_str db 'BIOS error at: ', NULL
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error_str db 'error', NULL
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%endif
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%if UNUSED
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keypress_str db 'Press any key to continue...', NULL
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%endif
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;; Pad this file to a size of 2048 bytes (one CD sector).
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pad:
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times 2044-($-$$) db 0
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CDBootSize dd CDBootSizeMagic
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;; Location of loaded boot2 code.
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kBoot2LoadAddr equ $
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;
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; Global variables
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;
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ABSOLUTE kReadBuffer + kSectorBytes
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gBIOSDriveNumber resw 1
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; END
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