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SECTION .text
USE16
stage2.entry:
; enable A20-Line via IO-Port 92, might not work on all motherboards
in al, 0x92
or al, 2
out 0x92, al
; load memory map
;TODO: rewrite this in Rust
call memory_map
mov edi, [args.stage3_base]
mov ecx, (stage3.end - stage3)
mov [args.stage3_size], ecx
mov eax, (stage3 - stage1)/512
add ecx, 511
shr ecx, 9
call load_extent
mov dword [protected_mode.func], stage3.entry
jmp protected_mode.entry
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args:
.stage3_base dq 0x100000
.stage3_size dq 0
; load a disk extent into high memory
; eax - sector address
; ecx - sector count
; edi - destination
load_extent:
; loading stage3 to 1MiB
; move part of stage3 to stage2.end via bootsector#load and then copy it up
; repeat until all of the stage3 is loaded
buffer_size_sectors equ 127
.lp:
cmp ecx, buffer_size_sectors
jb .break
; saving counter
push eax
push ecx
push edi
; populating buffer
mov ecx, buffer_size_sectors
mov bx, stage2.end
mov dx, 0x0
; load sectors
call load
; set up unreal mode
call unreal
pop edi
; move data
mov esi, stage2.end
mov ecx, buffer_size_sectors * 512 / 4
cld
a32 rep movsd
pop ecx
pop eax
add eax, buffer_size_sectors
sub ecx, buffer_size_sectors
jmp .lp
.break:
; load the part of the stage3 that does not fill the buffer completely
test ecx, ecx
jz .finish ; if cx = 0 => skip
push ecx
push edi
mov bx, stage2.end
mov dx, 0x0
call load
; moving remnants of stage3
call unreal
pop edi
pop ecx
mov esi, stage2.end
shl ecx, 7 ; * 512 / 4
cld
a32 rep movsd
.finish:
call print_line
ret
%include "thunk.asm"
%include "protected_mode.asm"
%include "long_mode.asm"
mov eax, thunk.int16
push eax
mov eax, thunk.int15
push eax
mov eax, thunk.int13
push eax
mov eax, thunk.int10
push eax
xor eax, eax
mov al, [disk]
push eax
mov eax, [args.stage3_base]
call [eax + 0x18]
.halt:
cli
hlt
jmp .halt