33 lines
643 B
NASM
33 lines
643 B
NASM
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; Code related to memory segment from 0xFFFF0 - 0x10FFEF
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; Check if 0000:0000 and FFFF:0010 point to the same memory
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; ZF=1 when A20 disabled and HMA unusable
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; ZF=0 when A20 enabled
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a20_enabled:
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mov ax, 0x0000
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mov ds, ax
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mov si, ax
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mov ax, 0xFFFF
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mov di, 0x0010
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mov cx, 0x0200
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repe cmpsw
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ret
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; Relocate kernel code to HMA
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hma_relocate:
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call a20_enabled
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; TODO: talk to hw to enable a20
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jz .end
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mov ax, cs
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mov ds, ax
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mov si, 0x0010
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mov ax, 0xFFFF
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mov es, ax ; new code segment
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mov ss, ax ; new stack segment
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mov di, 0x0010
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mov cx, 0x7FF8 ; 0xFFF0 divided by 2
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repe movsw
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jmp 0xFFFF:.end
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.end:
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ret
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