| ; - if not found, itarates over drives again and searches for active partition and␊ |
| ; loads from it␊ |
| ;␊ |
| ; dmazar: 19/7/2011␊ |
| ; Searching for bootable partition works in 3 passes now:␊ |
| ;␊ |
| ; - Pass1:␊ |
| ; - for the boot drive only:␊ |
| ; - searches MBR partition table for an active HSF+ bootable partition and boots it␊ |
| ; - if not found and disk is actually GPT, then searches for the first HFS+ bootable␊ |
| ; partition (or EFI with boot1f32) in the GPT array and boots it␊ |
| ; - if still not found, then continues with Pass2␊ |
| ;␊ |
| ; - Pass2:␊ |
| ; - iterates over all drives and for each drive:␊ |
| ; - searches MBR partition table for the first HSF+ bootable partition and boots it␊ |
| ; - if not found and disk is actually GPT, then searches for the first HFS+ bootable␊ |
| ; partition (or EFI with boot1f32) in the GPT array and boots it␊ |
| ; - if still not found, then continues with the next drive␊ |
| ; - if all drives are searched and nothing found, then continues with Pass3␊ |
| ␊ |
| ; - Pass3:␊ |
| ; - iterates over all drives and for each drive:␊ |
| ; - searches MBR partition table for the first active bootable partition and boots it␊ |
| ; - if not found and disk is actually GPT, then searches for the first HFS+ bootable␊ |
| ; partition (or EFI with boot1f32) in the GPT and boots it␊ |
| ; - if still not found, then continues with the next drive␊ |
| ; - if all drives are searched and nothing found, finishes with "boot0: error"␊ |
| ;␊ |
| ; Bootable partition above means a partition with the boot sector signature (0xAA55)␊ |
| ; at the end of the partition boot sector.␊ |
| ; Booting partition means loading partition boot sector and passing control to partition␊ |
| ; boot loader (for example boot1h).␊ |
| ; Drives are searched in the order defined in the BIOS. Drive which is selected as the boot drive␊ |
| ; is searched first.␊ |
| ;␊ |
| ; If compiled with DEBUG=1 gives debug output:␊ |
| ; P - starting new pass␊ |
| ; D - starting disk scanning: MBR and then GPT␊ |
| ; p - checking MBR partition entry␊ |
| ; t - testing MBR partition␊ |
| ; l - MBR or GPT partition satisfies conditions - loading partition boot sector␊ |
| ; G - found GPT␊ |
| ; + - stage 1 booter loaded, press a key to continue␊ |
| ; E - error␊ |
| ;␊ |
| ␊ |
| ;␊ |
| ; Set to 1 to enable obscure debug messages.␊ |
| ;␊ |
| DEBUG␉␉␉␉EQU CONFIG_BOOT0_DEBUG␊ |
| ;DEBUG␉␉␉␉EQU CONFIG_BOOT0_DEBUG␊ |
| DEBUG␉␉␉␉EQU 0␊ |
| NOT_USED␉␉␉EQU 0␉␉␉␉; exclude print_hex - no space for it ␊ |
| ␊ |
| ;␊ |
| ; Set to 1 to enable verbose mode␊ |
| ; Verbose - write boot0 messages␊ |
| ; No space for verbose and debug in the same time␊ |
| ;␊ |
| VERBOSE␉␉␉␉EQU CONFIG_BOOT0_VERBOSE␊ |
| ;VERBOSE␉␉␉␉EQU CONFIG_BOOT0_VERBOSE␊ |
| %if DEBUG␊ |
| VERBOSE␉␉␉␉EQU 0␊ |
| %else␊ |
| VERBOSE␉␉␉␉EQU 1␊ |
| %endif␊ |
| ␊ |
| ;␊ |
| ; Various constants.␊ |
|
| kDriveNumber␉␉EQU 0x80␊ |
| %endif␊ |
| ␊ |
| kPass1␉␉␉␉EQU 3␉␉␉␉; Pass1 ␊ |
| kPass2␉␉␉␉EQU 2␉␉␉␉; Pass2 ␊ |
| kPass3␉␉␉␉EQU 1␉␉␉␉; Pass3 ␊ |
| ␊ |
| ;␊ |
| ; Format of fdisk partition entry.␊ |
| ;␊ |
|
| call print_char␊ |
| %endmacro␊ |
| ␊ |
| %macro LogString 1␊ |
| %macro DebugPauseMacro 0␊ |
| call getc␊ |
| %endmacro␊ |
| ␊ |
| %macro LogStringMacro 1␊ |
| mov di, %1␊ |
| call log_string␊ |
| %endmacro␊ |
| ␊ |
| %if DEBUG␊ |
| %define DebugChar(x) DebugCharMacro x␊ |
| %define DebugPause DebugPauseMacro␊ |
| %else␊ |
| %define DebugChar(x)␊ |
| %define DebugPause␊ |
| %endif␊ |
| ␊ |
| %if VERBOSE␊ |
| %define LogString(x) LogStringMacro x␊ |
| %else␊ |
| %define LogString(x)␊ |
| %endif␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
| ; Start of text segment.␊ |
| ␊ |
|
| ;␊ |
| start_reloc:␊ |
| ␊ |
| ␉push␉dx␉␉␉␉␉␉; save dl (boot drive) for second pass.␊ |
| ␉␉␉␉␉␉␉␉␉; will stay on stack if booter loaded in first pass.␊ |
| ␉␉␉␉␉␉␉␉␉; this should not be a problem␊ |
| mov␉␉bh, 1␉␉␉␉␉; BH = 1. two pass scanning (active or hfs partition).␊ |
| ␉␉␉␉␉␉␉␉␉; actuall use of it (scanning) is in find_boot␊ |
| ␉;␊ |
| ␉; BH is pass counter␊ |
| ␉; Pass1 BH=3, Pass2 BH=2, Pass3 BH=1␊ |
| ␉;␊ |
| mov␉␉bh, kPass1␉␉␉␉; BH = 3. Pass1␊ |
| ␊ |
| scan_drives:␊ |
| pass_loop:␊ |
| ␊ |
| ␉DebugChar('>')␊ |
| ␉DebugChar('P')␉␉␉␉␉; starting new pass␊ |
| ␉push␉dx␉␉␉␉␉␉; save dl (boot drive) for next pass␊ |
| ␉␊ |
| ␉␊ |
| .scan_drive:␊ |
| ␊ |
| %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.␊ |
|
| mov bx, kMBRBuffer␉␉␉; MBR load address␊ |
| call load␊ |
| ␉pop␉␉bx␉␉␉␉␉␉; restore BH␊ |
| jc .mbr_load_error␉␉␉; MBR load error - normally because we scanned all drives␊ |
| jc .next_pass␉␉␉␉; MBR load error - normally because we scanned all drives␊ |
| ␊ |
| ␉DebugChar('D')␉␉␉␉␉; starting disk scanning␊ |
| ␉␊ |
| ;␊ |
| ; Look for the booter partition in the MBR partition table,␊ |
| ; which is at offset kMBRPartTable.␊ |
|
| mov si, kMBRPartTable␉␉; pointer to partition table␊ |
| call find_boot␉␉␉␉; will not return on success␊ |
| ␉␊ |
| ␉; if returns - booter partition not found␊ |
| ␉; if returns - booter partition is not found␊ |
| ␉␊ |
| ␉; skip scanning of all drives in Pass1␊ |
| ␉cmp␉␉bh, kPass1␊ |
| ␉je␉␉.next_pass␊ |
| ␉␊ |
| ␉; try next drive␊ |
| ␉; if next drive does not exists - will break on above MBR load error␊ |
| ␉; if next drive does not exists - will break on the MBR load error above␊ |
| ␉inc␉␉dl␊ |
| ␉jmp␉␉scan_drives␊ |
| ␉jmp␉␉short .scan_drive␊ |
| ␉␊ |
| ␊ |
| .mbr_load_error:␊ |
| ␉; all drives scanned - see if we need to run second pass␊ |
| .next_pass:␊ |
| ␉; all drives scanned - move to next pass␊ |
| ␉pop␉␉dx␉␉␉␉␉␉; restore orig boot drive␊ |
| ␉dec␉␉bh␉␉␉␉␉␉; decrement scan pass counter␊ |
| ␉jz␉␉scan_drives␉␉␉␉; if zero - run seccond pass␊ |
| ␉jnz␉␉pass_loop␉␉␉␉; if not zero - exec next pass␊ |
| ␉␊ |
| ␉; we ran two passes - nothing found - error␊ |
| ␉; we ran all passes - nothing found - error␊ |
| ␉␊ |
| error:␊ |
| DebugChar('E')␊ |
| DebugPause␊ |
| LogString(boot_error_str)␊ |
| ␊ |
| hang:␊ |
| hlt␊ |
| jmp hang␊ |
| jmp short hang␊ |
| ␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
|
| ; Arguments:␊ |
| ; DL = drive number (0x80 + unit number)␊ |
| ; SI = pointer to fdisk partition table.␊ |
| ; BH = pass counter (1=first pass, 0=second pass)␊ |
| ; BH = pass counter␊ |
| ;␊ |
| ; Clobber list:␊ |
| ; EAX, BX, EBP␊ |
|
| ␊ |
| .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␊ |
| ␊ |
| ␉DebugChar('p')␉␉␉␉␉␉␉␉␉; checking partition entry␊ |
| 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?␊ |
|
| mov␉ bl, 1␉␉␉␉␉␉␉␉␉; Assume we can deal with GPT but try to scan␊ |
| ␉␉␉␉␉ ␉␉␉␉␉␉␉; later if not found any other bootable partitions.␊ |
| ␊ |
| ␉;␊ |
| ␉; The following code between .testPass and .tryToBoot performs checking for 3 passes: ␊ |
| ␉; Pass1 (BH=3) if (partition is HFS+ and active) then { DH=1; call loadBootSector} ␊ |
| ␉; Pass2 (BH=2) if (partition is HFS+) then { DH=1; call loadBootSector}␊ |
| ␉; Pass3 (BH=1) if (partition is active) then { DH=0; call loadBootSector}␊ |
| ␉;␊ |
| ␉; BH is Pass counter␊ |
| ␉; DH is argument to loadBootSector␊ |
| ␉; = 0 - skip HFS+ partition signature check␊ |
| ␉; = 1 - check for HFS+ partition signature␊ |
| ␉; ␊ |
| ␉; Code may be harder to read because I tried to optimized it for minimum size.␊ |
| ␉;␊ |
| ␉␉␉␉␉␉␉␉␉␉␉␉␉␊ |
| .testPass:␊ |
| cmp␉ bh, 1␊ |
| jne␉ .Pass2␊ |
| ␉DebugChar('t')␉␉␉␉␉␉␉␉␉; testing partition␊ |
| xor␉␉dh, dh ␉␉␉␉␉; DH=0 This will be used in Pass3 (partition is active, not HFS+).␊ |
| ␉␉␉␉␉␉␉␉␉␉␉␉␊ |
| cmp␉ bh, kPass3␉␉␉␉␉␉␉␉; If this is Pass3 (BH=1)␊ |
| je␉ .checkActive␉␉␉␉␉␉␉; check for active flag only.␊ |
| ␊ |
| .Pass1:␊ |
| cmp␉ BYTE [si + part.type], kPartTypeHFS␉␉; In pass 1 we're going to find a HFS+ partition␊ |
| ; equipped with boot1h in its boot record␊ |
| ; regardless if it's active or not.␊ |
| .checkHFS:␊ |
| ␉␉␉␉␉␉␉␉␉␉␉␉␉; We are in Pass1 (BH=3) or Pass2 (BH=2).␊ |
| ␉inc␉␉dh␉ ␉␉␉␉␉; DH=1␊ |
| cmp␉ BYTE [si + part.type], kPartTypeHFS␉␉; Check for a HFS+ partition.␊ |
| jne .continue␊ |
| mov␉␉dh, 1 ␉␉␉␉␉; Argument for loadBootSector to check HFS+ partition signature.␊ |
| ␊ |
| jmp .tryToBoot␊ |
| cmp␉ bh, kPass2␉␉␉␉␉␉␉␉; It's HFS+. That's enough checking for Pass2,␊ |
| je␉ .tryToBoot␉␉␉␉␉␉␉␉; so try to boot (with DH=1)␊ |
| ␉␉␉␉␉␉␉␉␉␉␉␉; Pass1 needs active flag check also ...␊ |
| ␊ |
| .Pass2: ␊ |
| cmp BYTE [si + part.bootid], kPartActive␉; In pass 2 we are walking on the standard path␊ |
| ; by trying to hop on the active partition.␊ |
| .checkActive:␊ |
| ␉␉␉␉␉␉␉␉␉␉␉␉␉; We are in Pass1 or Pass3␊ |
| cmp BYTE [si + part.bootid], kPartActive␉; Check if partition is Active␊ |
| jne .continue␊ |
| xor␉␉dh, dh ␉␉␉␉␉; Argument for loadBootSector to skip HFS+ partition␊ |
| ; signature check.␊ |
| ␊ |
| DebugChar('*')␊ |
| ␊ |
| ;␊ |
| ; Found boot partition, read boot sector to memory.␊ |
|
| ;␊ |
| initBootLoader: ␊ |
| ␊ |
| DebugChar('J')␊ |
| DebugChar('+')␊ |
| DebugPause␊ |
| ␊ |
| %if VERBOSE␊ |
| LogString(done_str)␊ |
| %endif␊ |
| ␊ |
| jmp kBoot0LoadAddr␊ |
| ␊ |
|
| jne␉ .exit␉␉␉␉␉␉␉␉; not found. Giving up.␊ |
| cmp␉ DWORD [di + 4], kGPTSignatureHigh ; looking for 'PART'␊ |
| jne␉ .exit␉␉␉␉␉␉␉␉; not found. Giving up indeed.␊ |
| ␊ |
| DebugChar('G')␉␉␉␉␉␉␉␉; found GPT␊ |
| mov␉ si, di␊ |
| ␊ |
| ␊ |
| ;␊ |
| ; Loading GUID Partition Table 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 error␊ |
| ␉jc .exit␉␉␉␉␉; dmazar's change to continue disk scanning if encountering invalid LBA.␊ |
| ␊ |
| ;␊ |
| ; Walk through GUID Partition Table Array␊ |
|
| ; otherwise skip to next partition.␊ |
| ;␊ |
| ␊ |
| %if VERBOSE␊ |
| LogString(gpt_str)␊ |
| %endif␊ |
| ␊ |
| .gpt_loop:␊ |
| ␊ |
|
| loadBootSector:␊ |
| pusha␊ |
| ␊ |
| DebugChar('l')␉␉␉␉␉␉␉␉␉; loading partition boot sector␊ |
| ␊ |
| mov al, 3␊ |
| mov bx, kBoot0LoadAddr␊ |
| call load␊ |
| jc error␊ |
| ;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:␊ |
| ␊ |
| %if VERBOSE␊ |
| ;LogString(test_str)␉␉␉; dmazar: removed to get space␊ |
| %endif␊ |
| ␊ |
| ␉;␊ |
| ␉; Looking for HFSPlus ('H+') or HFSPlus case-sensitive ('HX') signature.␊ |
|
| pop cx␊ |
| ret␊ |
| ␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
| ; 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('<')␊ |
| %if DEBUG␊ |
| mov eax, ecx␊ |
| call print_hex␊ |
| %endif␊ |
| ␊ |
| ;␊ |
| ; INT13 Func 42 - Extended Read Sectors␊ |
| ;␊ |
|
| ␊ |
| jnc .exit␊ |
| ␊ |
| DebugChar('R') ; indicate INT13/F42 error␊ |
| ␊ |
| ;␊ |
| ; Issue a disk reset on error.␊ |
| ; Should this be changed to Func 0xD to skip the diskette controller␊ |
|
| popad␊ |
| ret␊ |
| ␊ |
| ␊ |
| ␊ |
| %if VERBOSE␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
| ; Write a string with 'boot0: ' prefix to the console.␊ |
| ;␊ |
|
| .exit:␊ |
| ret␊ |
| ␊ |
| %endif ;VERBOSE␊ |
| ␊ |
| ␊ |
| %if DEBUG␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
|
| 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.␊ |
|
| call print_char␊ |
| ret␊ |
| ␊ |
| getc:␊ |
| pusha␊ |
| mov ah, 0␊ |
| int 0x16␊ |
| popa␊ |
| ret␊ |
| %endif ;DEBUG␊ |
| ␉␊ |
| %endif ; NOT_USED␊ |
| ␊ |
| ␊ |
| ␊ |
| %if VERBOSE␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
| ; NULL terminated strings.␊ |
| ;␊ |
| log_title_str␉␉db 10, 13, 'boot0: ', 0␊ |
| log_title_str␉␉db 10, 13, 'boot0:', 0␊ |
| boot_error_str ␉db 'error', 0␊ |
| ␊ |
| %if VERBOSE␊ |
| gpt_str␉␉␉db 'GPT', 0␊ |
| ;test_str␉␉db 'test', 0␊ |
| done_str␉␉db 'done', 0␊ |
| ␊ |
| %endif␊ |
| ␊ |
| ;--------------------------------------------------------------------------␊ |
