basickernel/switch_prot.asm
Nicolás Ortega Froysa 4700f983f8
Adding code so far.
2018-02-23 17:20:31 +01:00

30 lines
975 B
NASM

[bits 16]
switch_to_pm:
cli ; turn off all interrupts until we have properly
; properly set them up
lgdt [gdt_descriptor] ; load the global descriptor table defining
; protected mode segments
mov eax, cr0 ; set flag in register to switch to protected mode
or eax, 0x1
mov cr0, eax
jmp GDT_CODE_SEG:init_pm ; make a far jump to the 32-bit code forcing a flush
; of the pipelining
[bits 32]
; initialize registers and the stack once in protected mode
init_pm:
mov ax, GDT_DATA_SEG ; point our new segment registers to the data
mov ds, ax ; selector defined in the GDT, since we cannot
mov ss, ax ; use the old 16-bit code
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 0x90000 ; Update the stack position so it's at the top
mov esp, ebp ; of the free space
call BEGIN_PM