mirror of
https://github.com/CloverHackyColor/CloverBootloader.git
synced 2024-12-17 15:18:06 +01:00
906 lines
26 KiB
ArmAsm
906 lines
26 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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; Boot Loader: boot0
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;
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; A small boot sector program written in x86 assembly whose only
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; responsibility is to locate the active partition, load the
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; partition booter into memory, and jump to the booter's entry point.
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; It leaves the boot drive in DL and a pointer to the partition entry in SI.
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;
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; This boot loader must be placed in the Master Boot Record.
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;
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; In order to coexist with a fdisk partition table (64 bytes), and
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; leave room for a two byte signature (0xAA55) in the end, boot0 is
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; restricted to 446 bytes (512 - 64 - 2). If boot0 did not have to
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; live in the MBR, then we would have 510 bytes to work with.
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;
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; boot0 is always loaded by the BIOS or another booter to 0:7C00h.
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;
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; This code is written for the NASM assembler.
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; nasm boot0.s -o boot0
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;
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; This version of boot0 implements hybrid GUID/MBR partition scheme support
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;
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; Written by Tam‡s Kos‡rszky on 2008-03-10
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;
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; Turbo added EFI System Partition boot support
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;
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; Added KillerJK's switchPass2 modifications
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;
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; dmazar: 10/7/2011 added scanning of all BIOS accessible drives:
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; - iterates over all drives and searches for HSF bootable partition (with boot1h)
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; and loads from it
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; - if not found, itarates over drives again and searches for active partition and
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; loads from it
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;
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; dmazar: 19/7/2011
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; Searching for bootable partition works in 3 passes now:
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;
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; - Pass1:
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; - for the boot drive only:
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; - searches MBR partition table for an active HSF+ bootable partition and boots it
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; - if not found and disk is actually GPT, then searches for the first HFS+ bootable
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; partition (or EFI with boot1f32) in the GPT array and boots it
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; - if still not found, then continues with Pass2
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;
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; - Pass2:
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; - iterates over all drives and for each drive:
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; - searches MBR partition table for the first HSF+ bootable partition and boots it
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; - if not found and disk is actually GPT, then searches for the first HFS+ bootable
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; partition (or EFI with boot1f32) in the GPT array and boots it
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; - if still not found, then continues with the next drive
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; - if all drives are searched and nothing found, then continues with Pass3
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; - Pass3:
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; - iterates over all drives and for each drive:
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; - searches MBR partition table for the first active bootable partition and boots it
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; - if not found and disk is actually GPT, then searches for the first HFS+ bootable
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; partition (or EFI with boot1f32) in the GPT and boots it
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; - if still not found, then continues with the next drive
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; - if all drives are searched and nothing found, finishes with "boot0: error"
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;
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; Bootable partition above means a partition with the boot sector signature (0xAA55)
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; at the end of the partition boot sector.
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; Booting partition means loading partition boot sector and passing control to partition
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; boot loader (for example boot1h).
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; Drives are searched in the order defined in the BIOS. Drive which is selected as the boot drive
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; is searched first.
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;
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; If compiled with DEBUG=1 gives debug output:
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; P - starting new pass
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; D - starting disk scanning: MBR and then GPT
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; p - checking MBR partition entry
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; t - testing MBR partition
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; l - MBR or GPT partition satisfies conditions - loading partition boot sector
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; G - found GPT
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; + - stage 1 booter loaded, press a key to continue
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; E - error
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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 CONFIG_BOOT0_DEBUG
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DEBUG EQU 0
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NOT_USED EQU 0 ; exclude print_hex - no space for it
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;
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; Verbose - write boot0 messages
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; No space for verbose and debug in the same time
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;
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;VERBOSE EQU CONFIG_BOOT0_VERBOSE
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%if DEBUG
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VERBOSE EQU 0
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%else
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VERBOSE EQU 1
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%endif
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;
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; Various constants.
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;
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kBoot0Segment EQU 0x0000
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kBoot0Stack EQU 0xFFF0 ; boot0 stack pointer
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kBoot0LoadAddr EQU 0x7C00 ; boot0 load address
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kBoot0RelocAddr EQU 0xE000 ; boot0 relocated address
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kMBRBuffer EQU 0x1000 ; MBR buffer address
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kLBA1Buffer EQU 0x1200 ; LBA1 - GPT Partition Table Header buffer address
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kGPTABuffer EQU 0x1400 ; GUID Partition Entry Array buffer address
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kPartTableOffset EQU 0x1be
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kMBRPartTable EQU kMBRBuffer + kPartTableOffset
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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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kHFSPSignature EQU 'H+' ; HFS+ volume signature
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kHFSPCaseSignature EQU 'HX' ; HFS+ volume case-sensitive signature
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kFAT32BootCodeOffset EQU 0x5a ; offset of boot code in FAT32 boot sector
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kBoot1FAT32Magic EQU 'BO' ; Magic string to detect our boot1f32 code
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kGPTSignatureLow EQU 'EFI ' ; GUID Partition Table Header Signature
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kGPTSignatureHigh EQU 'PART'
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kGUIDLastDwordOffs EQU 12 ; last 4 byte offset of a GUID
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kPartCount EQU 4 ; number of paritions per table
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kPartTypeHFS EQU 0xaf ; HFS+ Filesystem type
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kPartTypePMBR EQU 0xee ; On all GUID Partition Table disks a Protective MBR (PMBR)
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; in LBA 0 (that is, the first block) precedes the
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; GUID Partition Table Header to maintain compatibility
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; with existing tools that do not understand GPT partition structures.
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; The Protective MBR has the same format as a legacy MBR
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; and contains one partition entry with an OSType set to 0xEE
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; reserving the entire space used on the disk by the GPT partitions,
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; including all headers.
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kPartActive EQU 0x80 ; active flag enabled
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kPartInactive EQU 0x00 ; active flag disabled
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kHFSGUID EQU 0x48465300 ; first 4 bytes of Apple HFS Partition Type GUID.
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kAppleGUID EQU 0xACEC4365 ; last 4 bytes of Apple type GUIDs.
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kEFISystemGUID EQU 0x3BC93EC9 ; last 4 bytes of EFI System Partition Type GUID:
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; C12A7328-F81F-11D2-BA4B-00A0C93EC93B
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%ifdef FLOPPY
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kDriveNumber EQU 0x00
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%else
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kDriveNumber EQU 0x80
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%endif
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kPass1 EQU 3 ; Pass1
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kPass2 EQU 2 ; Pass2
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kPass3 EQU 1 ; Pass3
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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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;
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; Format of GPT Partition Table Header
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;
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struc gpth
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.Signature resb 8
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.Revision resb 4
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.HeaderSize resb 4
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.HeaderCRC32 resb 4
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.Reserved resb 4
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.MyLBA resb 8
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.AlternateLBA resb 8
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.FirstUsableLBA resb 8
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.LastUsableLBA resb 8
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.DiskGUID resb 16
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.PartitionEntryLBA resb 8
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.NumberOfPartitionEntries resb 4
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.SizeOfPartitionEntry resb 4
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.PartitionEntryArrayCRC32 resb 4
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endstruc
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;
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; Format of GUID Partition Entry Array
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;
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struc gpta
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.PartitionTypeGUID resb 16
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.UniquePartitionGUID resb 16
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.StartingLBA resb 8
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.EndingLBA resb 8
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.Attributes resb 8
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.PartitionName resb 72
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endstruc
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;
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; Macros.
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;
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%macro DebugCharMacro 1
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mov al, %1
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call print_char
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%endmacro
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%macro DebugPauseMacro 0
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call getc
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%endmacro
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%macro LogStringMacro 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 DebugPauseMacro
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%else
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%define DebugChar(x)
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%define DebugPause
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%endif
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%if VERBOSE
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%define LogString(x) LogStringMacro x
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%else
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%define LogString(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 kBoot0RelocAddr
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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 kBoot0Segment:kBoot0Stack.
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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 ax, ax ; zero ax
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mov ss, ax ; ss <- 0
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mov sp, kBoot0Stack ; sp <- top of stack
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sti ; reenable interrupts
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mov es, ax ; es <- 0
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mov ds, ax ; ds <- 0
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;
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; Relocate boot0 code.
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;
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mov si, kBoot0LoadAddr ; si <- source
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mov di, kBoot0RelocAddr ; di <- destination
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cld ; auto-increment SI and/or DI registers
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mov cx, kSectorBytes/2 ; copy 256 words
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repnz movsw ; repeat string move (word) operation
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;
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; Code relocated, jump to start_reloc in relocated location.
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;
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jmp kBoot0Segment:start_reloc
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;--------------------------------------------------------------------------
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; Start execution from the relocated location.
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;
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start_reloc:
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;
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; BH is pass counter
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; Pass1 BH=3, Pass2 BH=2, Pass3 BH=1
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;
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mov bh, kPass1 ; BH = 3. Pass1
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pass_loop:
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DebugChar('P') ; starting new pass
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push dx ; save dl (boot drive) for next pass
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.scan_drive:
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;
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; Since this code may not always reside in the MBR, always start by
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; loading the MBR to kMBRBuffer and LBA1 to kGPTBuffer.
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;
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push bx ; save BH (scan pass counter)
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xor eax, eax
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mov [my_lba], eax ; store LBA sector 0 for read_lba function
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mov al, 2 ; load two sectors: MBR and LBA1
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mov bx, kMBRBuffer ; MBR load address
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call load
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pop bx ; restore BH
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jc .next_pass ; MBR load error - normally because we scanned all drives
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DebugChar('D') ; starting disk scanning
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;
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; Look for the booter partition in the MBR partition table,
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; which is at offset kMBRPartTable.
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;
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mov si, kMBRPartTable ; pointer to partition table
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call find_boot ; will not return on success
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; if returns - booter partition is not found
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; skip scanning of all drives in Pass1
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cmp bh, kPass1
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je .next_pass
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; try next drive
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; if next drive does not exists - will break on the MBR load error above
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inc dl
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jmp short .scan_drive
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.next_pass:
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; all drives scanned - move to next pass
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pop dx ; restore orig boot drive
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dec bh ; decrement scan pass counter
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jnz pass_loop ; if not zero - exec next pass
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; we ran all passes - nothing found - error
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error:
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DebugChar('E')
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DebugPause
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LogString(boot_error_str)
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hang:
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hlt
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jmp short hang
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;--------------------------------------------------------------------------
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; Find the active (boot) partition and load the booter from the partition.
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;
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; Arguments:
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; DL = drive number (0x80 + unit number)
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; SI = pointer to fdisk partition table.
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; BH = pass counter
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;
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; Clobber list:
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; EAX, BX, EBP
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;
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find_boot:
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;
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; Check for boot block signature 0xAA55 following the 4 partition
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; entries.
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;
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cmp WORD [si + part_size * kPartCount], kBootSignature
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jne .exit ; boot signature not found.
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xor bl, bl ; BL will be set to 1 later in case of
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; Protective MBR has been found
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.start_scan:
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mov cx, kPartCount ; number of partition entries per table
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.loop:
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DebugChar('p') ; checking partition entry
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mov eax, [si + part.lba] ; save starting LBA of current
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mov [my_lba], eax ; MBR partition entry for read_lba function
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cmp BYTE [si + part.type], 0 ; unused partition?
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je .continue ; skip to next entry
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cmp BYTE [si + part.type], kPartTypePMBR ; check for Protective MBR
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jne .testPass
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mov BYTE [si + part.bootid], kPartInactive ; found Protective MBR
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; clear active flag to make sure this protective
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; partition won't be used as a bootable partition.
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mov bl, 1 ; Assume we can deal with GPT but try to scan
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; later if not found any other bootable partitions.
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;
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; The following code between .testPass and .tryToBoot performs checking for 3 passes:
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; Pass1 (BH=3) if (partition is HFS+ and active) then { DH=1; call loadBootSector}
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; Pass2 (BH=2) if (partition is HFS+) then { DH=1; call loadBootSector}
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; Pass3 (BH=1) if (partition is active) then { DH=0; call loadBootSector}
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;
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; BH is Pass counter
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; DH is argument to loadBootSector
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; = 0 - skip HFS+ partition signature check
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; = 1 - check for HFS+ partition signature
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;
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; Code may be harder to read because I tried to optimized it for minimum size.
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;
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.testPass:
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DebugChar('t') ; testing partition
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xor dh, dh ; DH=0 This will be used in Pass3 (partition is active, not HFS+).
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cmp bh, kPass3 ; If this is Pass3 (BH=1)
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je .checkActive ; check for active flag only.
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.checkHFS:
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; We are in Pass1 (BH=3) or Pass2 (BH=2).
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inc dh ; DH=1
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cmp BYTE [si + part.type], kPartTypeHFS ; Check for a HFS+ partition.
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jne .continue
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cmp bh, kPass2 ; It's HFS+. That's enough checking for Pass2,
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je .tryToBoot ; so try to boot (with DH=1)
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; Pass1 needs active flag check also ...
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.checkActive:
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; We are in Pass1 or Pass3
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cmp BYTE [si + part.bootid], kPartActive ; Check if partition is Active
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jne .continue
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;
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; Found boot partition, read boot sector to memory.
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;
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.tryToBoot:
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call loadBootSector
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jne .continue
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jmp SHORT initBootLoader
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.continue:
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add si, BYTE part_size ; advance SI to next partition entry
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loop .loop ; loop through all partition entries
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;
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; Scanned all partitions but not found any with active flag enabled
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; Anyway if we found a protective MBR before we still have a chance
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; for a possible GPT Header at LBA 1
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;
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dec bl
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jnz .exit ; didn't find Protective MBR before
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call checkGPT
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.exit:
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ret ; Giving up.
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;
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; Jump to partition booter. The drive number is already in register DL.
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; SI is pointing to the modified partition entry.
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;
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initBootLoader:
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DebugChar('+')
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DebugPause
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LogString(done_str)
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jmp kBoot0LoadAddr
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;
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; Found Protective MBR Partition Type: 0xEE
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; Check for 'EFI PART' string at the beginning
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; of LBA1 for possible GPT Table Header
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;
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checkGPT:
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push bx
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mov di, kLBA1Buffer ; address of GUID Partition Table Header
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cmp DWORD [di], kGPTSignatureLow ; looking for 'EFI '
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jne .exit ; not found. Giving up.
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cmp DWORD [di + 4], kGPTSignatureHigh ; looking for 'PART'
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jne .exit ; not found. Giving up indeed.
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DebugChar('G') ; found GPT
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mov si, di
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;
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; Loading GUID Partition Table Array
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;
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mov eax, [si + gpth.PartitionEntryLBA] ; starting LBA of GPT Array
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mov [my_lba], eax ; save starting LBA for read_lba function
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mov cx, [si + gpth.NumberOfPartitionEntries] ; number of GUID Partition Array entries
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mov bx, [si + gpth.SizeOfPartitionEntry] ; size of GUID Partition Array entry
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push bx ; push size of GUID Partition entry
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;
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; Calculating number of sectors we need to read for loading a GPT Array
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;
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; push dx ; preserve DX (DL = BIOS drive unit number)
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; mov ax, cx ; AX * BX = number of entries * size of one entry
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; mul bx ; AX = total byte size of GPT Array
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; pop dx ; restore DX
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; shr ax, 9 ; convert to sectors
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;
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; ... or:
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; Current GPT Arrays uses 128 partition entries each 128 bytes long
|
|
; 128 entries * 128 bytes long GPT Array entries / 512 bytes per sector = 32 sectors
|
|
;
|
|
mov al, 32 ; maximum sector size of GPT Array (hardcoded method)
|
|
|
|
mov bx, kGPTABuffer
|
|
push bx ; push address of GPT Array
|
|
call load ; read GPT Array
|
|
pop si ; SI = address of GPT Array
|
|
pop bx ; BX = size of GUID Partition Array entry
|
|
;jc error
|
|
jc .exit ; dmazar's change to continue disk scanning if encountering invalid LBA.
|
|
|
|
;
|
|
; Walk through GUID Partition Table Array
|
|
; and load boot record from first available HFS+ partition.
|
|
;
|
|
; If it has boot signature (0xAA55) then jump to it
|
|
; otherwise skip to next partition.
|
|
;
|
|
|
|
LogString(gpt_str)
|
|
|
|
.gpt_loop:
|
|
|
|
mov eax, [si + gpta.PartitionTypeGUID + kGUIDLastDwordOffs]
|
|
|
|
cmp eax, kAppleGUID ; check current GUID Partition for Apple's GUID type
|
|
je .gpt_ok
|
|
|
|
;
|
|
; Turbo - also try EFI System Partition
|
|
;
|
|
|
|
cmp eax, kEFISystemGUID ; check current GUID Partition for EFI System Partition GUID type
|
|
jne .gpt_continue
|
|
|
|
.gpt_ok:
|
|
;
|
|
; Found HFS Partition
|
|
;
|
|
|
|
mov eax, [si + gpta.StartingLBA] ; load boot sector from StartingLBA
|
|
mov [my_lba], eax
|
|
mov dh, 1 ; Argument for loadBootSector to check HFS+ partition signature.
|
|
call loadBootSector
|
|
jne .gpt_continue ; no boot loader signature
|
|
|
|
mov si, kMBRPartTable ; fake the current GUID Partition
|
|
mov [si + part.lba], eax ; as MBR style partition for boot1h
|
|
mov BYTE [si + part.type], kPartTypeHFS ; with HFS+ filesystem type (0xAF)
|
|
jmp SHORT initBootLoader
|
|
|
|
.gpt_continue:
|
|
|
|
add si, bx ; advance SI to next partition entry
|
|
loop .gpt_loop ; loop through all partition entries
|
|
|
|
.exit:
|
|
pop bx
|
|
ret ; no more GUID partitions. Giving up.
|
|
|
|
|
|
;--------------------------------------------------------------------------
|
|
; loadBootSector - Load boot sector
|
|
;
|
|
; Arguments:
|
|
; DL = drive number (0x80 + unit number)
|
|
; DH = 0 skip HFS+ partition signature checking
|
|
; 1 enable HFS+ partition signature checking
|
|
; [my_lba] = starting LBA.
|
|
;
|
|
; Returns:
|
|
; ZF = 0 if boot sector hasn't kBootSignature
|
|
; 1 if boot sector has kBootSignature
|
|
;
|
|
loadBootSector:
|
|
pusha
|
|
|
|
DebugChar('l') ; loading partition boot sector
|
|
|
|
mov al, 3
|
|
mov bx, kBoot0LoadAddr
|
|
call load
|
|
;jc error
|
|
or dl, dl ; to set flag Z=0 ; dmazar's change to continue disk scanning if encountering invalid LBA.
|
|
jc .exit ; dmazar's change to continue disk scanning if encountering invalid LBA.
|
|
|
|
or dh, dh
|
|
jz .checkBootSignature
|
|
|
|
.checkHFSSignature:
|
|
|
|
;LogString(test_str) ; dmazar: removed to get space
|
|
|
|
;
|
|
; Looking for HFSPlus ('H+') or HFSPlus case-sensitive ('HX') signature.
|
|
;
|
|
mov ax, [kBoot0LoadAddr + 2 * kSectorBytes]
|
|
cmp ax, kHFSPSignature ; 'H+'
|
|
je .checkBootSignature
|
|
cmp ax, kHFSPCaseSignature ; 'HX'
|
|
je .checkBootSignature
|
|
|
|
;
|
|
; Looking for boot1f32 magic string.
|
|
;
|
|
mov ax, [kBoot0LoadAddr + kFAT32BootCodeOffset]
|
|
cmp ax, kBoot1FAT32Magic
|
|
jne .exit
|
|
|
|
.checkBootSignature:
|
|
;
|
|
; Check for boot block signature 0xAA55
|
|
;
|
|
mov di, bx
|
|
cmp WORD [di + kSectorBytes - 2], kBootSignature
|
|
|
|
.exit:
|
|
|
|
popa
|
|
|
|
ret
|
|
|
|
|
|
;--------------------------------------------------------------------------
|
|
; load - Load one or more sectors from a partition.
|
|
;
|
|
; Arguments:
|
|
; AL = number of 512-byte sectors to read.
|
|
; ES:BX = pointer to where the sectors should be stored.
|
|
; DL = drive number (0x80 + unit number)
|
|
; [my_lba] = starting LBA.
|
|
;
|
|
; Returns:
|
|
; CF = 0 success
|
|
; 1 error
|
|
;
|
|
load:
|
|
push cx
|
|
|
|
.ebios:
|
|
mov cx, 5 ; load retry count
|
|
.ebios_loop:
|
|
call read_lba ; use INT13/F42
|
|
jnc .exit
|
|
loop .ebios_loop
|
|
|
|
.exit:
|
|
pop cx
|
|
ret
|
|
|
|
;--------------------------------------------------------------------------
|
|
; read_lba - Read sectors from a partition using LBA addressing.
|
|
;
|
|
; Arguments:
|
|
; AL = number of 512-byte sectors to read (valid from 1-127).
|
|
; ES:BX = pointer to where the sectors should be stored.
|
|
; DL = drive number (0x80 + unit number)
|
|
; [my_lba] = starting LBA.
|
|
;
|
|
; Returns:
|
|
; CF = 0 success
|
|
; 1 error
|
|
;
|
|
read_lba:
|
|
pushad ; save all registers
|
|
mov bp, sp ; save current SP
|
|
|
|
;
|
|
; 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.
|
|
mov ecx, [my_lba] ; 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
|
|
|
|
; It pushes 2 bytes with a smaller opcode than if WORD was used
|
|
push BYTE 16 ; offset 0-1, packet size
|
|
|
|
;
|
|
; INT13 Func 42 - Extended Read Sectors
|
|
;
|
|
; Arguments:
|
|
; AH = 0x42
|
|
; DL = drive number (80h + drive unit)
|
|
; 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 si, sp
|
|
mov ah, 0x42
|
|
int 0x13
|
|
|
|
jnc .exit
|
|
|
|
;
|
|
; 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
|
|
popad
|
|
ret
|
|
|
|
|
|
%if VERBOSE
|
|
|
|
;--------------------------------------------------------------------------
|
|
; Write a string with 'boot0: ' prefix to the console.
|
|
;
|
|
; Arguments:
|
|
; ES:DI pointer to a NULL terminated string.
|
|
;
|
|
; Clobber list:
|
|
; DI
|
|
;
|
|
log_string:
|
|
pusha
|
|
|
|
push di
|
|
mov si, log_title_str
|
|
call print_string
|
|
|
|
pop si
|
|
call print_string
|
|
|
|
popa
|
|
|
|
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)
|
|
cld ; increment SI after each lodsb call
|
|
.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 short .loop
|
|
.exit:
|
|
ret
|
|
|
|
%endif ;VERBOSE
|
|
|
|
|
|
%if DEBUG
|
|
|
|
;--------------------------------------------------------------------------
|
|
; Write a ASCII character to the console.
|
|
;
|
|
; Arguments:
|
|
; AL = ASCII character.
|
|
;
|
|
print_char:
|
|
pusha
|
|
mov bx, 1 ; BH=0, BL=1 (blue)
|
|
mov ah, 0x0e ; bios INT 10, Function 0xE
|
|
int 0x10 ; display byte in tty mode
|
|
popa
|
|
ret
|
|
|
|
getc:
|
|
pusha
|
|
mov ah, 0
|
|
int 0x16
|
|
popa
|
|
ret
|
|
%endif ;DEBUG
|
|
|
|
%if NOT_USED
|
|
|
|
;--------------------------------------------------------------------------
|
|
; 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
|
|
|
|
mov al, 10 ; carriage return
|
|
call print_char
|
|
mov al, 13
|
|
call print_char
|
|
|
|
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
|
|
|
|
%endif ; NOT_USED
|
|
|
|
|
|
|
|
%if VERBOSE
|
|
|
|
;--------------------------------------------------------------------------
|
|
; NULL terminated strings.
|
|
;
|
|
log_title_str db 10, 13, 'boot0:', 0
|
|
boot_error_str db 'error', 0
|
|
|
|
gpt_str db 'GPT', 0
|
|
;test_str db 'test', 0
|
|
done_str db 'done', 0
|
|
|
|
%endif
|
|
|
|
;--------------------------------------------------------------------------
|
|
; Pad the rest of the 512 byte sized booter 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.
|
|
|
|
;
|
|
; According to EFI specification, maximum boot code size is 440 bytes
|
|
;
|
|
|
|
pad_boot:
|
|
times 440-($-$$) db 0
|
|
|
|
pad_table_and_sig:
|
|
times 510-($-$$) db 0
|
|
dw kBootSignature
|
|
|
|
|
|
ABSOLUTE 0xE400
|
|
|
|
;
|
|
; In memory variables.
|
|
;
|
|
my_lba resd 1 ; Starting LBA for read_lba function
|
|
|
|
; END
|