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;; ;;
;; SWITCH TO 32 BIT PROTECTED MODE ;;
;; ;;
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os_data = os_data_l-gdts ; GDTs
os_code = os_code_l-gdts
int_code equ int_code_l-gdts
int_data equ int_data_l-gdts
tss0sys equ tss0sys_l-gdts
graph_data equ 3+graph_data_l-gdts
tss0 equ tss0_l-gdts
app_code equ 3+app_code_l-gdts
app_data equ 3+app_data_l-gdts
; CR0 Flags - Protected mode and Paging
mov ecx, CR0_PE
; Enabling 32 bit protected mode
sidt [cs:old_ints_h-0x10000]
cli ; disable all irqs
cld
mov al,255 ; mask all irqs
out 0xa1,al
out 0x21,al
l.5: in al, 0x64 ; Enable A20
test al, 2
jnz l.5
mov al, 0xD1
out 0x64, al
l.6: in al, 0x64
test al, 2
jnz l.6
mov al, 0xDF
out 0x60, al
l.7: in al, 0x64
test al, 2
jnz l.7
mov al, 0xFF
out 0x64, al
lgdt [cs:gdts-0x10000] ; Load GDT
mov eax, cr0 ; Turn on paging // protected mode
or eax, ecx
and eax, 10011111b *65536*256 + 0xffffff ; caching enabled
mov cr0, eax
jmp $+2
org $+0x10000
mov ax,os_data ; Selector for os
mov ds,ax
mov es,ax
mov fs,ax
mov gs,ax
mov ss,ax
mov esp,0x3ec00 ; Set stack
jmp pword os_code:B32 ; jmp to enable 32 bit mode
if gdte >= $
error 'GDT overlaps with used code!'
end if