; Copyright (c) 1999-2003 Apple Computer, Inc. All rights reserved. ; ; @APPLE_LICENSE_HEADER_START@ ; ; Portions Copyright (c) 1999-2003 Apple Computer, Inc. All Rights ; Reserved. This file contains Original Code and/or Modifications of ; Original Code as defined in and that are subject to the Apple Public ; Source License Version 2.0 (the "License"). You may not use this file ; except in compliance with the License. Please obtain a copy of the ; License at http://www.apple.com/publicsource and read it before using ; this file. ; ; The Original Code and all software distributed under the License are ; distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER ; EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, ; INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, ; FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT. Please see the ; License for the specific language governing rights and limitations ; under the License. ; ; @APPLE_LICENSE_HEADER_END@ ; ; Partition Boot Loader: boot1f32 ; ; This program is designed to reside in sector 0 of a FAT32 partition. ; It expects that the MBR has left the drive number in DL ; and a pointer to the partition entry in SI. ; ; This version requires a BIOS with EBIOS (LBA) support. ; ; This code is written for the NASM assembler. ; nasm boot1f32.s -o boot1f32 ; ; dd if=origbs of=newbs skip=3 seek=3 bs=1 count=87 conv=notrunc ; ; ; This version of boot1f32 tries to find a stage2 boot file in the root folder. ; ; Written by mackerintel on 2009-01-26 ; ; ; Set to 1 to enable obscure debug messages. ; DEBUG EQU 0 ; ; Set to 1 to enable unused code. ; UNUSED EQU 0 ; ; Set to 1 to enable verbose mode. ; VERBOSE EQU 1 ; ; Set to 1 to make this stage 1 loader expecting arguments in SI and DL registers. ; USESIDL EQU 1 ; ; Various constants. ; NULL EQU 0 CR EQU 0x0D LF EQU 0x0A maxSectorCount EQU 64 ; maximum sector count for readSectors kSectorBytes EQU 512 ; sector size in bytes kBootSignature EQU 0xAA55 ; boot sector signature kBoot1StackAddress EQU 0xFFF0 ; boot1 stack pointer kBoot1LoadAddr EQU 0x7C00 ; boot1 load address kBoot1RelocAddr EQU 0xE000 ; boot1 relocated address kBoot2Sectors EQU (384 * 1024 - 512) / kSectorBytes ; max size of 'boot' file in sectors kBoot2Segment EQU 0x2000 ; boot2 load segment kBoot2Address EQU kSectorBytes ; boot2 load address FATBUF EQU 0x7000 ; Just place for one sectors DIRBUFSEG EQU 0x1000 ; Cluster sizes >64KB aren't supported ; ; Format of fdisk partition entry. ; ; The symbol 'part_size' is automatically defined as an `EQU' ; giving the size of the structure. ; struc part .bootid resb 1 ; bootable or not .head resb 1 ; starting head, sector, cylinder .sect resb 1 ; .cyl resb 1 ; .type resb 1 ; partition type .endhead resb 1 ; ending head, sector, cylinder .endsect resb 1 ; .endcyl resb 1 ; .lba resd 1 ; starting lba .sectors resd 1 ; size in sectors endstruc struc direntry .nameext resb 11 .attr resb 1 .nused1 resb 8 .highclus resw 1 .nused2 resb 4 .lowclus resw 1 .size resd 1 endstruc ; ; Macros. ; %macro jmpabs 1 push WORD %1 ret %endmacro %macro DebugCharMacro 1 pushad mov al, %1 call print_char call getc popad %endmacro %macro PrintCharMacro 1 pushad mov al, %1 call print_char popad %endmacro %macro PutCharMacro 1 call print_char %endmacro %macro PrintHexMacro 1 call print_hex %endmacro %macro PrintString 1 mov si, %1 call print_string %endmacro %macro LogString 1 mov di, %1 call log_string %endmacro %if DEBUG %define DebugChar(x) DebugCharMacro x %define PrintChar(x) PrintCharMacro x %define PutChar(x) PutCharMacro %define PrintHex(x) PrintHexMacro x %else %define DebugChar(x) %define PrintChar(x) %define PutChar(x) %define PrintHex(x) %endif ;-------------------------------------------------------------------------- ; Start of text segment. SEGMENT .text ORG kBoot1LoadAddr jmp start times 3-($-$$) nop gOEMName times 8 db 0 ;OEMNAME gBPS dw 0 gSPC db 0 gReservedSectors dw 0 gNumFats db 0 gCrap1 times 11 db 0 gPartLBA dd 0 gPartSize dd 0 gSectPerFat dd 0 gCrap2 times 4 db 0 gRootCluster dd 0 gCrap3 times 16 db 0 gBIOSDriveNumber db 0 gExtInfo times 25 db 0 gFileName db "BOOT " ;-------------------------------------------------------------------------- ; Boot code is loaded at 0:7C00h. ; start: ; ; set up the stack to grow down from kBoot1StackSegment:kBoot1StackAddress. ; Interrupts should be off while the stack is being manipulated. ; cli ; interrupts off xor eax, eax ; zero ax mov ss, ax ; ss <- 0 mov sp, kBoot1StackAddress ; sp <- top of stack sti ; reenable interrupts mov ds, ax ; ds <- 0 mov es, ax ; es <- 0 ; ; Initializing global variables. ; mov ax, word [gReservedSectors] %if USESIDL add eax, [si + part.lba] %else add eax, [gPartLBA] %endif mov [gPartLBA], eax ; save the current FAT LBA offset %if USESIDL mov [gBIOSDriveNumber], dl ; save BIOS drive number %endif xor eax,eax mov al, [gNumFats] mul dword [gSectPerFat] mov [gSectPerFat], eax ;-------------------------------------------------------------------------- ; Find stage2 boot file in a FAT32 Volume's root folder. ; findRootBoot: %if VERBOSE LogString(init_str) %endif mov eax, [gRootCluster] nextdirclus: mov edx, DIRBUFSEG<<4 call readCluster jc error xor si, si mov bl, [gSPC] shl bx, 9 add bx, si nextdirent: mov di, gFileName push ds push DIRBUFSEG pop ds mov cl, [si] test cl, cl jz dserror mov cx, 11 repe cmpsb jz direntfound falsealert: pop ds add cl, 21 add si, cx cmp si, bx jz nextdirclus jmp nextdirent direntfound: ; test byte [ds:si+direntry.attr-11], 0x18 lodsb test al, 0x18 jnz falsealert push WORD [si + direntry.highclus - 12] push WORD [si + direntry.lowclus - 12] pop eax pop ds mov edx, (kBoot2Segment << 4) + kBoot2Address cont_read: push edx call readCluster pop edx pushf xor ebx,ebx mov bl, [gSPC] shl ebx, 9 add edx, ebx popf jnc cont_read boot2: %if DEBUG DebugChar ('!') %endif %if UNUSED ; ; Waiting for a key press. ; mov ah, 0 int 0x16 %endif mov dl, [gBIOSDriveNumber] ; load BIOS drive number jmp kBoot2Segment:kBoot2Address dserror: pop ds error: %if VERBOSE LogString(error_str) %endif hang: hlt jmp hang ; readCluster - Reads cluster EAX to (EDX), updates EAX to next cluster readCluster: cmp eax, 0x0ffffff8 jb do_read stc ret do_read: push eax xor ecx,ecx dec eax dec eax mov cl, [gSPC] push edx mul ecx pop edx add eax, [gSectPerFat] mov ecx, eax xor ah,ah mov al, [gSPC] call readSectors jc clusend pop ecx push cx shr ecx, 7 xor ax, ax inc ax mov edx, FATBUF call readSectors jc clusend pop si and si, 0x7f shl si, 2 mov eax, [FATBUF + si] and eax, 0x0fffffff clc ret clusend: pop eax ret ;-------------------------------------------------------------------------- ; readSectors - Reads more than 127 sectors using LBA addressing. ; ; Arguments: ; AX = number of 512-byte sectors to read (valid from 1-1280). ; EDX = pointer to where the sectors should be stored. ; ECX = sector offset in partition ; ; Returns: ; CF = 0 success ; 1 error ; readSectors: pushad mov bx, ax .loop: xor eax, eax ; EAX = 0 mov al, bl ; assume we reached the last block. cmp bx, maxSectorCount ; check if we really reached the last block jb .readBlock ; yes, BX < MaxSectorCount mov al, maxSectorCount ; no, read MaxSectorCount .readBlock: call readLBA sub bx, ax ; decrease remaning sectors with the read amount jz .exit ; exit if no more sectors left to be loaded add ecx, eax ; adjust LBA sector offset shl ax, 9 ; convert sectors to bytes add edx, eax ; adjust target memory location jmp .loop ; read remaining sectors .exit: popad ret ;-------------------------------------------------------------------------- ; readLBA - Read sectors from a partition using LBA addressing. ; ; Arguments: ; AL = number of 512-byte sectors to read (valid from 1-127). ; EDX = pointer to where the sectors should be stored. ; ECX = sector offset in partition ; [bios_drive_number] = drive number (0x80 + unit number) ; ; Returns: ; CF = 0 success ; 1 error ; readLBA: pushad ; save all registers push es ; save ES mov bp, sp ; save current SP ; ; Convert EDX to segment:offset model and set ES:BX ; ; Some BIOSes do not like offset to be negative while reading ; from hard drives. This usually leads to "boot1: error" when trying ; to boot from hard drive, while booting normally from USB flash. ; The routines, responsible for this are apparently different. ; Thus we split linear address slightly differently for these ; capricious BIOSes to make sure offset is always positive. ; mov bx, dx ; save offset to BX and bh, 0x0f ; keep low 12 bits shr edx, 4 ; adjust linear address to segment base xor dl, dl ; mask low 8 bits mov es, dx ; save segment to ES ; ; Create the Disk Address Packet structure for the ; INT13/F42 (Extended Read Sectors) on the stack. ; ; push DWORD 0 ; offset 12, upper 32-bit LBA push ds ; For sake of saving memory, push ds ; push DS register, which is 0. add ecx, [gPartLBA] ; offset 8, lower 32-bit LBA push ecx push es ; offset 6, memory segment push bx ; offset 4, memory offset xor ah, ah ; offset 3, must be 0 push ax ; offset 2, number of sectors push WORD 16 ; offset 0-1, packet size ; ; INT13 Func 42 - Extended Read Sectors ; ; Arguments: ; AH = 0x42 ; [bios_drive_number] = drive number (0x80 + unit number) ; DS:SI = pointer to Disk Address Packet ; ; Returns: ; AH = return status (sucess is 0) ; carry = 0 success ; 1 error ; ; Packet offset 2 indicates the number of sectors read ; successfully. ; mov dl, [gBIOSDriveNumber] ; load BIOS drive number mov si, sp mov ah, 0x42 int 0x13 jc error ; ; Issue a disk reset on error. ; Should this be changed to Func 0xD to skip the diskette controller ; reset? ; ; xor ax, ax ; Func 0 ; int 0x13 ; INT 13 ; stc ; set carry to indicate error .exit: mov sp, bp ; restore SP pop es ; restore ES popad ret %if VERBOSE ;-------------------------------------------------------------------------- ; Write a string with 'boot1: ' prefix to the console. ; ; Arguments: ; ES:DI pointer to a NULL terminated string. ; ; Clobber list: ; DI ; log_string: pushad push di mov si, log_title_str call print_string pop si call print_string popad ret ;------------------------------------------------------------------------- ; Write a string to the console. ; ; Arguments: ; DS:SI pointer to a NULL terminated string. ; ; Clobber list: ; AX, BX, SI ; print_string: mov bx, 1 ; BH=0, BL=1 (blue) .loop: lodsb ; load a byte from DS:SI into AL cmp al, 0 ; Is it a NULL? je .exit ; yes, all done mov ah, 0xE ; INT10 Func 0xE int 0x10 ; display byte in tty mode jmp .loop .exit: ret %endif ; VERBOSE %if DEBUG ;-------------------------------------------------------------------------- ; Write the 4-byte value to the console in hex. ; ; Arguments: ; EAX = Value to be displayed in hex. ; print_hex: pushad mov cx, WORD 4 bswap eax .loop: push ax ror al, 4 call print_nibble ; display upper nibble pop ax call print_nibble ; display lower nibble ror eax, 8 loop .loop %if UNUSED mov al, 10 ; carriage return call print_char mov al, 13 call print_char %endif ; UNUSED popad ret print_nibble: and al, 0x0f add al, '0' cmp al, '9' jna .print_ascii add al, 'A' - '9' - 1 .print_ascii: call print_char ret ;-------------------------------------------------------------------------- ; getc - wait for a key press ; getc: pushad mov ah, 0 int 0x16 popad ret ;-------------------------------------------------------------------------- ; Write a ASCII character to the console. ; ; Arguments: ; AL = ASCII character. ; print_char: pushad mov bx, 1 ; BH=0, BL=1 (blue) mov ah, 0x0e ; bios INT 10, Function 0xE int 0x10 ; display byte in tty mode popad ret %endif ; DEBUG ;-------------------------------------------------------------------------- ; Static data. ; %if VERBOSE 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