Unreal Mode: Difference between revisions
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| [unchecked revision] | [unchecked revision] |
Content deleted Content added
Syntax higlighting |
Played with comments |
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; partcopy boot.bin 0 200 -f0 |
; partcopy boot.bin 0 200 -f0 |
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[ORG 0x7c00] ; add to offsets |
[ORG 0x7c00] ; add to offsets |
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start: xor ax, ax ; make it zero |
start: xor ax, ax ; make it zero |
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mov ds, ax ; DS=0 |
mov ds, ax ; DS=0 |
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mov ss, ax ; stack starts at 0 |
mov ss, ax ; stack starts at seg 0 |
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mov sp, 0x9c00 ; 200h past code start |
mov sp, 0x9c00 ; 200h past code start |
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cli ; no |
cli ; no interrupts |
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push ds ; save real mode |
push ds ; save real mode |
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lgdt [gdtinfo] ; load gdt register |
lgdt [gdtinfo] ; load gdt register |
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mov eax, cr0 ; switch to pmode by |
mov eax, cr0 ; switch to pmode by |
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or al,1 ; set pmode bit |
or al,1 ; set pmode bit |
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mov cr0, eax |
mov cr0, eax |
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mov bx, 0x08 ; select descriptor 1 |
mov bx, 0x08 ; select descriptor 1 |
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mov ds, bx ; 8h = 1000b |
mov ds, bx ; 8h = 1000b |
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and al,0xFE ; back to realmode |
and al,0xFE ; back to realmode |
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mov cr0, eax ; by toggling bit again |
mov cr0, eax ; by toggling bit again |
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pop ds ; get back old segment |
pop ds ; get back old segment |
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sti |
sti |
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mov bx, 0x0f01 ; attrib/char of smiley |
mov bx, 0x0f01 ; attrib/char of smiley |
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mov eax, 0x0b8000 ; note 32 bit offset |
mov eax, 0x0b8000 ; note 32 bit offset |
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mov word [ds:eax], bx |
mov word [ds:eax], bx |
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jmp $ ; loop forever |
jmp $ ; loop forever |
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gdtinfo: |
gdtinfo: |
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dd gdt ;start of table |
dd gdt ;start of table |
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gdt dd 0,0 ; entry 0 is always unused |
gdt dd 0,0 ; entry 0 is always unused |
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flatdesc db 0xff, 0xff, 0, 0, 0, 10010010b, 11001111b, 0 |
flatdesc db 0xff, 0xff, 0, 0, 0, 10010010b, 11001111b, 0 |
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gdt_end: |
gdt_end: |
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times 510-($-$$) db 0 ; fill sector w/ 0's |
times 510-($-$$) db 0 ; fill sector w/ 0's |
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db 0x55 ; req'd by some BIOSes |
db 0x55 ; req'd by some BIOSes |
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db 0xAA |
db 0xAA |
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</source> |
</source> |
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