637 lines
14 KiB
ArmAsm
637 lines
14 KiB
ArmAsm
; Copyright (c) 1999-2003 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) 1999-2003 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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;
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; Partition Boot Loader: boot1f32
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;
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; This program is designed to reside in sector 0 of a FAT32 partition.
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; It expects that the MBR has left the drive number in DL
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; and a pointer to the partition entry in SI.
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;
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; This version requires a BIOS with EBIOS (LBA) support.
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;
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; This code is written for the NASM assembler.
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; nasm boot1f32.s -o boot1f32
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;
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; dd if=origbs of=newbs skip=3 seek=3 bs=1 count=87 conv=notrunc
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;
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;
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; This version of boot1f32 tries to find a stage2 boot file in the root folder.
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;
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; Written by mackerintel on 2009-01-26
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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 0
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;
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; Set to 1 to make this stage 1 loader expecting arguments in SI and DL registers.
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;
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USESIDL 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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maxSectorCount EQU 64 ; maximum sector count for readSectors
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kSectorBytes EQU 512 ; sector size in bytes
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kBootSignature EQU 0xAA55 ; boot sector signature
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kBoot1StackAddress EQU 0xFFF0 ; boot1 stack pointer
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kBoot1LoadAddr EQU 0x7C00 ; boot1 load address
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kBoot1RelocAddr EQU 0xE000 ; boot1 relocated address
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kBoot2Sectors EQU (480 * 1024 - 512) / kSectorBytes ; max size of 'boot' file in sectors
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kBoot2Segment EQU 0x2000 ; boot2 load segment
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kBoot2Address EQU kSectorBytes ; boot2 load address
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FATBUF EQU 0x7000 ; Just place for one sectors
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DIRBUFSEG EQU 0x1000 ; Cluster sizes >64KB aren't supported
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;
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; Format of fdisk partition entry.
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;
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; The symbol 'part_size' is automatically defined as an `EQU'
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; giving the size of the structure.
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;
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struc part
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.bootid resb 1 ; bootable or not
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.head resb 1 ; starting head, sector, cylinder
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.sect resb 1 ;
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.cyl resb 1 ;
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.type resb 1 ; partition type
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.endhead resb 1 ; ending head, sector, cylinder
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.endsect resb 1 ;
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.endcyl resb 1 ;
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.lba resd 1 ; starting lba
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.sectors resd 1 ; size in sectors
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endstruc
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struc direntry
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.nameext resb 11
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.attr resb 1
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.nused1 resb 8
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.highclus resw 1
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.nused2 resb 4
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.lowclus resw 1
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.size resd 1
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endstruc
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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 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 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 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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;--------------------------------------------------------------------------
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; Start of text segment.
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SEGMENT .text
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ORG kBoot1LoadAddr
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jmp start
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times 3-($-$$) nop
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gOEMName times 8 db 0 ;OEMNAME
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gBPS dw 0
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gSPC db 0
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gReservedSectors dw 0
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gNumFats db 0
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gCrap1 times 11 db 0
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gPartLBA dd 0
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gPartSize dd 0
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gSectPerFat dd 0
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gCrap2 times 4 db 0
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gRootCluster dd 0
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gCrap3 times 16 db 0
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gBIOSDriveNumber db 0
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gExtInfo times 25 db 0
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gFileName db "BOOT " ; Used as a magic string in boot0
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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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;
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; set up the stack to grow down from kBoot1StackSegment:kBoot1StackAddress.
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; Interrupts should be off while the stack is being manipulated.
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;
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cli ; interrupts off
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xor eax, eax ; zero ax
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mov ss, ax ; ss <- 0
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mov sp, kBoot1StackAddress ; sp <- top of stack
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sti ; reenable interrupts
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mov ds, ax ; ds <- 0
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mov es, ax ; es <- 0
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;
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; Initializing global variables.
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;
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mov ax, word [gReservedSectors]
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%if USESIDL
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add eax, [si + part.lba]
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%else
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add eax, [gPartLBA]
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%endif
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mov [gPartLBA], eax ; save the current FAT LBA offset
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%if USESIDL
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mov [gBIOSDriveNumber], dl ; save BIOS drive number
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%endif
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xor eax,eax
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mov al, [gNumFats]
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mul dword [gSectPerFat]
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mov [gSectPerFat], eax
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;--------------------------------------------------------------------------
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; Find stage2 boot file in a FAT32 Volume's root folder.
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;
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findRootBoot:
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%if VERBOSE
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LogString(init_str)
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%endif
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mov eax, [gRootCluster]
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nextdirclus:
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mov edx, DIRBUFSEG<<4
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call readCluster
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jc error
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xor si, si
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mov bl, [gSPC]
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shl bx, 9
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add bx, si
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nextdirent:
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mov di, gFileName
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push ds
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push DIRBUFSEG
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pop ds
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mov cl, [si]
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test cl, cl
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jz dserror
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mov cx, 11
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repe cmpsb
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jz direntfound
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falsealert:
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pop ds
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add cl, 21
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add si, cx
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cmp si, bx
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jz nextdirclus
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jmp nextdirent
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direntfound:
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; test byte [ds:si+direntry.attr-11], 0x18
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lodsb
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test al, 0x18
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jnz falsealert
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push WORD [si + direntry.highclus - 12]
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push WORD [si + direntry.lowclus - 12]
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pop eax
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pop ds
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mov edx, (kBoot2Segment << 4) + kBoot2Address
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cont_read:
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push edx
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call readCluster
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pop edx
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pushf
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xor ebx,ebx
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mov bl, [gSPC]
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shl ebx, 9
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add edx, ebx
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popf
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jnc cont_read
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boot2:
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%if DEBUG
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DebugChar ('!')
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%endif
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%if UNUSED
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;
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; Waiting for a key press.
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;
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mov ah, 0
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int 0x16
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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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dserror:
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pop ds
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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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hang:
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hlt
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jmp hang
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; readCluster - Reads cluster EAX to (EDX), updates EAX to next cluster
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readCluster:
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cmp eax, 0x0ffffff8
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jb do_read
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stc
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ret
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do_read:
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push eax
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xor ecx,ecx
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dec eax
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dec eax
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mov cl, [gSPC]
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push edx
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mul ecx
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pop edx
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add eax, [gSectPerFat]
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mov ecx, eax
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xor ah,ah
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mov al, [gSPC]
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call readSectors
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jc clusend
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pop ecx
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push cx
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shr ecx, 7
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xor ax, ax
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inc ax
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mov edx, FATBUF
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call readSectors
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jc clusend
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pop si
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and si, 0x7f
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shl si, 2
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mov eax, [FATBUF + si]
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and eax, 0x0fffffff
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clc
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ret
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clusend:
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pop eax
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ret
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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 512-byte sectors to read (valid from 1-1280).
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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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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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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 ax, 9 ; convert 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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; [bios_drive_number] = 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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add ecx, [gPartLBA] ; offset 8, lower 32-bit LBA
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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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; [bios_drive_number] = 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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jc 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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; 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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%if VERBOSE
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;--------------------------------------------------------------------------
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; Write a string with 'boot1: ' 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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%endif ; VERBOSE
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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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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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;--------------------------------------------------------------------------
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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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%endif ; DEBUG
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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, 'b1f: ', NULL
|
|
init_str db 'init', NULL
|
|
error_str db 'error', NULL
|
|
%endif
|
|
|
|
;--------------------------------------------------------------------------
|
|
; Pad the rest of the 512 byte sized sector with zeroes. The last
|
|
; two bytes is the mandatory boot sector signature.
|
|
;
|
|
; If the booter code becomes too large, then nasm will complain
|
|
; that the 'times' argument is negative.
|
|
|
|
pad_table_and_sig:
|
|
times 510-($-$$) db 0
|
|
dw kBootSignature
|
|
|
|
ABSOLUTE kBoot1LoadAddr + kSectorBytes
|
|
|
|
; END
|