120 lines
1.5 KiB
ArmAsm
120 lines
1.5 KiB
ArmAsm
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[org 0x100]
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[bits 16]
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cli
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mov ax, ds
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mov [torm+3], ax
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mov gs, ax
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mov [oldss], ss
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mov [oldsp], sp
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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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; TODO maybe choose a better entrypoint than the start of hma
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cld
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mov cx, 65280-bindat
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mov si, bindat
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mov ax, 0xFFFF
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mov es, ax
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mov di, 0x10
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rep movsb
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; relocate jump target
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xor eax, eax
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mov ax, ds
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shl eax, 4
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add [gdt+2], eax
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add [gdt_end+2], eax
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mov [gds+2], ax
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mov [gds16+2], ax
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mov [gcs16+2], ax
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shr eax, 16
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mov [gds+4], al
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mov [gds16+4], al
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mov [gcs16+4], al
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lgdt [gdt]
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mov eax, cr0
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or al, 1
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mov cr0, eax
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ijmp: jmp dsseg:init
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[bits 32]
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init:
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; retain stack pointer
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; esp = ebp = (ss << 4) + sp
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xor ebp, ebp
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xor ebx, ebx
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mov bp, ss
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mov bx, sp
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shl ebp, 4
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add ebp, ebx
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mov esp, ebp
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mov ax, data
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mov ds, ax
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mov ss, ax
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mov es, ax
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mov fs, ax
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call code:0x100000 ; start
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cli
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jf: jmp cs16:in16
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[bits 16]
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in16:
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mov ax, ds16
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mov ds, ax
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lidt [idt]
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mov eax, cr0
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and al, 0xFE
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mov cr0, eax
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torm: jmp 0:inrm
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inrm: mov ax, gs
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov ss, [oldss]
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mov sp, [oldsp]
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sti
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xor ax, ax
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int 21h
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ret
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idt: dw 0x3FF
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dd 0
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gdt: dw gdt_end - gdt - 1
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dd gdt
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dw 0
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gcode: dd 0x0000ffff
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code equ gcode - gdt
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db 0, 10011011b, 11001111b, 0
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gdata: dd 0x0000ffff
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data equ gdata - gdt
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db 0, 10010011b, 11001111b, 0
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gds: dd 0x0000ffff
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dsseg equ gds - gdt
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db 0, 10011111b, 01001111b, 0
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gds16: dd 0x0000ffff
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ds16 equ gds16 - gdt
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db 0, 10010111b, 00001111b, 0
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gcs16: dd 0x0000ffff
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cs16 equ gcs16 - gdt
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db 0, 10011111b, 00001111b, 0
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gdt_end:
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oldss: dw 0
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oldsp: dw 0
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bindat equ $
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