90 lines
1.8 KiB
NASM
90 lines
1.8 KiB
NASM
SECTION .text
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USE16
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startup:
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; enable A20-Line via IO-Port 92, might not work on all motherboards
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in al, 0x92
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or al, 2
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out 0x92, al
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; loading kernel to 1MiB
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; move part of kernel to startup_end via bootsector#load and then copy it up
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; repeat until all of the kernel is loaded
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; buffersize in multiple of sectors (512 Bytes)
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; min 1
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; max (0x70000 - startup_end) / 512
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buffer_size_sectors equ 1
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; buffer size in Bytes
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buffer_size_bytes equ buffer_size_sectors * 512
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kernel_base equ 0x100000
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; how often do we need to call load and move memory
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mov ecx, kernel_file.length_sectors / buffer_size_sectors
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mov ax, (kernel_file - boot) / 512
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mov edi, kernel_base
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cld
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.lp:
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; saving counter
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push cx
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; populating buffer
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mov cx, buffer_size_sectors
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mov bx, startup_end
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mov dx, 0x0
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push ax
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call load
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; moving buffer
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call unreal
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pop ax
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mov esi, startup_end
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mov ecx, buffer_size_bytes / 4
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a32 rep movsd
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; preparing next iteration
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add ax, buffer_size_sectors
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pop cx
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loop .lp
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; load the part of the kernel that does not fill the buffer completely
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mov cx, kernel_file.length_sectors % buffer_size_sectors
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test cx, cx
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jz finished_loading ; if cx = 0 => skip
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mov bx, startup_end
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mov dx, 0x0
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call load
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; moving remnants of kernel
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call unreal
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mov esi, startup_end
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mov ecx, (kernel_file.length_sectors % buffer_size_bytes) / 4
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a32 rep movsd
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finished_loading:
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call memory_map
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call vesa
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call initialize.fpu
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call initialize.sse
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call initialize.pit
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call initialize.pic
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jmp startup_arch
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%include "descriptor_flags.inc"
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%include "gdt_entry.inc"
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%include "unreal.asm"
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%include "memory_map.asm"
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%include "vesa.asm"
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%include "initialize.asm"
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