| ;␊ |
| ; Set to 1 to enable obscure debug messages.␊ |
| ;␊ |
| DEBUG␉␉␉␉EQU CONFIG_BOOT0_DEBUG␊ |
| DEBUG␉␉␉␉EQU 1␊ |
| ␊ |
| ;␊ |
| ; Set to 1 to enable verbose mode␊ |
| ;␊ |
| VERBOSE␉␉␉␉EQU CONFIG_BOOT0_VERBOSE␊ |
| VERBOSE␉␉␉␉EQU 0␊ |
| ␊ |
| ;␊ |
| ; Various constants.␊ |
|
| kMBRPartTable␉␉EQU kMBRBuffer + kPartTableOffset␊ |
| ␊ |
| kSectorBytes␉␉EQU 512␉␉␉; sector size in bytes␊ |
| kChameleonBoot1hSignature␉␉EQU␉␉0xBB99␉␉␉␉␉␉␉␉; boot sector signature␊ |
| kBootSignature␉␉EQU 0xAA55␉␉␉; boot sector signature␊ |
| kHFSPSignature␉␉EQU 'H+'␉␉␉; HFS+ volume signature␊ |
| kHFSPCaseSignature␉EQU 'HX'␉␉␉; HFS+ volume case-sensitive signature␊ |
|
| ;␊ |
| ; Macros.␊ |
| ;␊ |
| %macro DebugCharMacro 1␊ |
| mov al, %1␊ |
| call print_char␊ |
| ␊ |
| %macro PrintCharMacro 1␊ |
| ␉mov␉␉al, %1␊ |
| ␉call␉print_char␊ |
| %endmacro␊ |
| ␊ |
| %macro PrintHexEaxMacro 0␊ |
| ␉call␉print_hex␊ |
| %endmacro␊ |
| ␊ |
| %macro PrintHexMacro 1␊ |
| ␉mov eax, %1␊ |
| ␉call␉print_hex␊ |
| %endmacro␊ |
| ␊ |
| ;%macro xGetCharMacro 0␊ |
| ;␉call␉getc␊ |
| ;%endmacro␊ |
| ␊ |
| %if DEBUG␊ |
| %define PrintChar(x) PrintCharMacro x␊ |
| %define PrintHex(x) PrintHexMacro x␊ |
| %define PrintHexEax PrintHexEaxMacro␊ |
| ; %define xGetChar xGetCharMarco␊ |
| %else␊ |
| %define PrintChar(x)␊ |
| %define PrintHex(x)␊ |
| %define PrintHexEax␊ |
| ; %define xGetChar␊ |
| %endif␊ |
| ␊ |
| %macro LogString 1␊ |
| mov di, %1␊ |
| call log_string␊ |
| %endmacro␊ |
| ␊ |
| %if DEBUG␊ |
| %define DebugChar(x) DebugCharMacro x␊ |
| %if VERBOSE␊ |
| %define LogString(x) LogStringMacro x␊ |
| %else␊ |
| %define DebugChar(x)␊ |
| %define LogString(x)␊ |
| %endif␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
|
| ;␊ |
| start_reloc:␊ |
| ␊ |
| DebugChar('>')␊ |
| PrintChar('8')␊ |
| PrintChar('>')␊ |
| ␊ |
| %if DEBUG␊ |
| mov al, dl␊ |
| call print_hex␊ |
| %endif␊ |
| ␊ |
| ;␊ |
| ; Since this code may not always reside in the MBR, always start by␊ |
| ; loading the MBR to kMBRBuffer and LBA1 to kGPTBuffer.␊ |
|
| call find_boot␉␉␉␉; will not return on success␊ |
| ␊ |
| error:␊ |
| LogString(boot_error_str)␊ |
| ; LogString(boot_error_str)␊ |
| ␊ |
| hang:␊ |
| hlt␊ |
| jmp hang␊ |
| ␊ |
| ␊ |
| ␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
| ; Find the active (boot) partition and load the booter from the partition.␊ |
| ;␊ |
|
| ;␊ |
| find_boot:␊ |
| ␊ |
| ;␊ |
| ; Check for boot block signature 0xAA55 following the 4 partition␊ |
| ; entries.␊ |
| ;␊ |
| cmp WORD [si + part_size * kPartCount], kBootSignature␊ |
| jne␉ .exit ␉ ␉␉␉; boot signature not found.␊ |
| ␊ |
| xor␉ bx, bx␉␉␉␉␉␉; BL will be set to 1 later in case of␊ |
| ␉␉␉␉␉␉␉␉␉␉; Protective MBR has been found␊ |
| ␊ |
| inc bh␉␉␉␉␉␉␉; BH = 1. Giving a chance for a second pass␊ |
| ␉␉␉␉␉␉␉␉␉␉; to boot an inactive but boot1h aware HFS+ partition␊ |
| ␉␉␉␉␉␉␉␉␉␉; by scanning the MBR partition entries again.␊ |
| ␊ |
| .start_scan:␉␉␉␉␉␉␉␊ |
| mov cx, kPartCount ␉; number of partition entries per table␊ |
| ␊ |
| .loop:␊ |
| ␊ |
| ;␊ |
| ; First scan through the partition table looking for the active␊ |
| ; partition.␊ |
| ;␊ |
| %if DEBUG␊ |
| mov al, [si + part.type] ␉ ; print partition type␊ |
| call print_hex␊ |
| %endif␊ |
| ␊ |
| mov␉ eax, [si + part.lba]␉␉␉␉␉; save starting LBA of current ␊ |
| mov␉ [my_lba], eax␉␉␉␉␉␉␉; MBR partition entry for read_lba function␊ |
| cmp BYTE [si + part.type], 0␉␉␉␉; unused partition?␊ |
| je .continue ␉␉␉␉␉␉␉␉; skip to next entry␊ |
| cmp␉ BYTE [si + part.type], kPartTypePMBR␉; check for Protective MBR ␊ |
| jne␉ .testPass␊ |
| ␊ |
| mov BYTE [si + part.bootid], kPartInactive␉; found Protective MBR␊ |
| ␉␉␉␉␉␉␉␉␉␉␉; clear active flag to make sure this protective␊ |
| ␉␉␉␉␉␉␉␉␉␉␉␉␉; partition won't be used as a bootable partition.␊ |
| mov␉ bl, 1␉␉␉␉␉␉␉␉␉; Assume we can deal with GPT but try to scan␊ |
| ␉␉␉␉␉ ␉␉␉␉␉␉␉; later if not found any other bootable partitions.␊ |
| ␊ |
| .testPass:␊ |
| cmp␉ bh, 1␊ |
| jne␉ .Pass2␊ |
| ␊ |
| .Pass1:␊ |
| cmp BYTE [si + part.bootid], kPartActive␉; In pass 1 we are walking on the standard path␊ |
| ; by trying to hop on the active partition.␊ |
| jne .continue␊ |
| xor␉ ␉dh, dh ␉␉␉␉␉; Argument for loadBootSector to skip HFS+ partition␊ |
| ␉␉␉␉␉␉␉␉␉␉␉ ; signature check.␊ |
| jmp .tryToBoot␊ |
| ␊ |
| .Pass2: ␊ |
| cmp␉ BYTE [si + part.type], kPartTypeHFS␉␉; In pass 2 we're going to find a HFS+ partition␊ |
| ; equipped with boot1h in its boot record␊ |
| ; regardless if it's active or not.␊ |
| jne .continue␊ |
| ␉mov ␉dh, 1 ␉␉␉␉␉; Argument for loadBootSector to check HFS+ partition signature.␊ |
| ␊ |
| DebugChar('*')␊ |
| ␊ |
| ;␊ |
| ; Found boot partition, read boot sector to memory.␊ |
| ;␊ |
| ␊ |
| .tryToBoot:␊ |
| ␊ |
| call loadBootSector␊ |
| jne .continue␊ |
| jmp␉ SHORT initBootLoader␊ |
| ␊ |
| .continue:␊ |
| add si, BYTE part_size ␉␉␉; advance SI to next partition entry␊ |
| loop .loop ␉␉ ␉; loop through all partition entries␊ |
| ␊ |
| ;␊ |
| ; Scanned all partitions but not found any with active flag enabled␊ |
| ; Anyway if we found a protective MBR before we still have a chance ␊ |
| ; for a possible GPT Header at LBA 1␊ |
| ; ␊ |
| dec␉ bl␊ |
| jnz .switchPass2␉␉␉␉␉; didn't find Protective MBR before␊ |
| call checkGPT␊ |
| ␊ |
| .switchPass2:␊ |
| ;␊ |
| ; Switching to Pass 2 ␊ |
| ; try to find a boot1h aware HFS+ MBR partition␊ |
| ;␊ |
| dec␉ bh␊ |
| mov␉ si, kMBRPartTable␉␉␉␉; set SI to first entry of MBR Partition table␊ |
| jz .start_scan␉␉␉␉␉␉; scan again␊ |
| ␊ |
| .exit:␊ |
| ret␉␉␉␉␉␉␉␉␉␉; Giving up.␊ |
| ␊ |
| ␊ |
| ;␊ |
| ; Jump to partition booter. The drive number is already in register DL.␊ |
| ; SI is pointing to the modified partition entry.␊ |
| ;␊ |
| initBootLoader: ␊ |
| ␊ |
| DebugChar('J')␊ |
| ␊ |
| %if VERBOSE␊ |
| LogString(done_str)␊ |
| %endif␊ |
| ␊ |
| jmp kBoot0LoadAddr␊ |
| ␊ |
| ␊ |
| ; ␊ |
| ; Found Protective MBR Partition Type: 0xEE␊ |
| ; Check for 'EFI PART' string at the beginning␊ |
| ; of LBA1 for possible GPT Table Header␊ |
| ;␊ |
| checkGPT:␊ |
| push bx␊ |
| ␊ |
|
| mov [my_lba], eax␉␉␉␉␉␉␉␉; save starting LBA for read_lba function␊ |
| mov cx, [si + gpth.NumberOfPartitionEntries]␉; number of GUID Partition Array entries␊ |
| mov bx, [si + gpth.SizeOfPartitionEntry]␉␉; size of GUID Partition Array entry␊ |
| ␊ |
| push bx␉␉␉␉␉␉␉␉␉␉␉; push size of GUID Partition entry␊ |
| ␊ |
| ;␊ |
|
| %if VERBOSE␊ |
| LogString(gpt_str)␊ |
| %endif␊ |
| ␊ |
| ␉␊ |
| ␉PrintChar('P')␊ |
| ␉mov dh, 1 ; partition number to give to boot1h␊ |
| ␉␉␊ |
| .gpt_loop:␊ |
| ␊ |
| ;PrintChar('1')␊ |
| mov eax, [si + gpta.PartitionTypeGUID + kGUIDLastDwordOffs]␊ |
| ␉␊ |
| ␉cmp␉␉eax, kAppleGUID␉␉␉; check current GUID Partition for Apple's GUID type␊ |
|
| ␉jne␉␉.gpt_continue␊ |
| ␊ |
| .gpt_ok:␊ |
| ;PrintChar('2')␊ |
| ;␊ |
| ; 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)␊ |
| %if VERBOSE␊ |
| ;LogString(test_str)␊ |
| %endif␊ |
| PrintChar('!')␊ |
| ␉mov ecx, [si + gpta.StartingLBA]␊ |
| jmp␉ SHORT initBootLoader ␊ |
| ␊ |
| .gpt_continue:␊ |
| ␊ |
| add␉ si, bx␉␉␉␉␉␉␉␉␉; advance SI to next partition entry␊ |
| inc dh␊ |
| loop .gpt_loop␉␉␉␉␉␉␉␉; loop through all partition entries␉␊ |
| ␊ |
| .exit:␊ |
|
| ;␊ |
| ; 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:␊ |
|
| call load␊ |
| jc error␊ |
| ␊ |
| ␉or␉␉dh, dh␊ |
| ␉jz␉␉.checkBootSignature␊ |
| ␉␊ |
| .checkHFSSignature:␊ |
| ␊ |
| %if VERBOSE␊ |
| LogString(test_str)␊ |
| %endif␊ |
| ␊ |
| ␉;␊ |
| ␉; 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␊ |
| ; Check for chameleon boot block signature of boot1h␊ |
| ;␊ |
| mov␉ di, bx␊ |
| cmp WORD [di + kSectorBytes - 2], kBootSignature␊ |
| cmp WORD [di + kSectorBytes - 4], kChameleonBoot1hSignature␊ |
| ␊ |
| .exit:␊ |
| ␊ |
| popa␊ |
| ␊ |
| ret␊ |
| ␊ |
| ␊ |
|
| ret␊ |
| ␊ |
| ␊ |
| initBootLoader: ␊ |
| ␉LogString(done_str)␊ |
| ␊ |
| PrintChar('J')␊ |
| ␊ |
| ;␉mov eax,kBoot0LoadAddr␊ |
| ;␉call print_hex␊ |
| ;␉mov eax,[kBoot0LoadAddr]␊ |
| ;␉call print_hex␊ |
| ;push si␊ |
| ;pop eax␊ |
| ;PrintHexEax␊ |
| ;PrintHex(edx)␊ |
| ␊ |
| jmp kBoot0LoadAddr␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
| ; read_lba - Read sectors from a partition using LBA addressing.␊ |
| ;␊ |
|
| ; It pushes 2 bytes with a smaller opcode than if WORD was used␊ |
| push BYTE 16 ; offset 0-1, packet size␊ |
| ␊ |
| DebugChar('<')␊ |
| PrintChar('<')␊ |
| %if DEBUG␊ |
| mov eax, ecx␊ |
| call print_hex␊ |
|
| ␊ |
| jnc .exit␊ |
| ␊ |
| DebugChar('R') ; indicate INT13/F42 error␊ |
| ; PrintChar('R') ; indicate INT13/F42 error␊ |
| ␊ |
| ;␊ |
| ; Issue a disk reset on error.␊ |
|
| ; Clobber list:␊ |
| ; DI␊ |
| ;␊ |
| log_string:␊ |
| pusha␊ |
| ␊ |
| push␉di␊ |
| mov␉␉si, log_title_str␊ |
| call␉print_string␊ |
| ;log_string:␊ |
| ; pusha␊ |
| ; ␊ |
| ; push␉di␊ |
| ; mov␉␉si, log_title_str␊ |
| ; call␉print_string␊ |
| ;␊ |
| ; pop␉␉si␊ |
| ; call␉print_string␊ |
| ;␊ |
| ; popa␊ |
| ; ␊ |
| ; ret␊ |
| ␊ |
| pop␉␉si␊ |
| call␉print_string␊ |
| ␊ |
| popa␊ |
| ␊ |
| ret␊ |
| ␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
| ; Write a string to the console.␊ |
| ;␊ |
|
| ;--------------------------------------------------------------------------␊ |
| ; NULL terminated strings.␊ |
| ;␊ |
| log_title_str␉␉db 10, 13, 'boot0: ', 0␊ |
| boot_error_str ␉db 'error', 0␊ |
| ;log_title_str␉␉db 10, 13, 'boot0: ', 0␊ |
| ;boot_error_str ␉db 'err', 0␊ |
| ␊ |
| %if VERBOSE␊ |
| gpt_str␉␉␉db 'GPT', 0␊ |
| test_str␉␉db 'test', 0␊ |
| ;test_str␉␉db 'test', 0␊ |
| done_str␉␉db 'done', 0␊ |
| %endif␊ |
| ␊ |
|
| times 440-($-$$) db 0␊ |
| ␊ |
| pad_table_and_sig:␊ |
| times 510-($-$$) db 0␊ |
| times 508-($-$$) db 0␊ |
| dw kChameleonBoot1hSignature␊ |
| dw kBootSignature␊ |
| ␉␊ |
| ␉␊ |
