23 lines
611 B
NASM
23 lines
611 B
NASM
[bits 16]
|
|
switch_to_pm:
|
|
cli ; 1. disable interrupts
|
|
lgdt [gdt_descriptor] ; 2. load the GDT descriptor
|
|
mov eax, cr0
|
|
or eax, 0x1 ; 3. set 32-bit mode bit in cr0
|
|
mov cr0, eax
|
|
jmp CODE_SEG:init_pm ; 4. far jump by using a different segment
|
|
|
|
[bits 32]
|
|
init_pm: ; we are now using 32-bit instructions
|
|
mov ax, DATA_SEG ; 5. update the segment registers
|
|
mov ds, ax
|
|
mov ss, ax
|
|
mov es, ax
|
|
mov fs, ax
|
|
mov gs, ax
|
|
|
|
mov ebp, 0x90000 ; 6. update the stack right at the top of the free space
|
|
mov esp, ebp
|
|
|
|
call BEGIN_PM ; 7. Call a well-known label with useful code
|