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I wrote a little kernel that enable A20, map IRQ 0-15 to INT 0x20-0x2D, and switch to PM. I have just a very basic console drivers (keybord & VGA). This little OS runs well, but now I like add 'paging' to it.

I write this rutine:

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; Initialize a page directory -->

mov ax, 0x0100 ; Page directory address at 0x1000
mov fs, ax ; Load 'fs'

mov bx, 0 ; First entry
mov cx, 0x400 ; Set a counter to 1024 entries

.load_pd:

mov [fs:bx], WORD 0x0002 ; Insert a no-present page table
inc bx
inc bx ; Go next entry

loop .load_pd

; Insert first page directory entry -->

mov eax, 0x2000 ; Address of the page table
or eax, 0x0003 ; Level S, R/W, present

mov [fs:0], eax ; Insert the entry

; Load the page table with the address first 4MB of memory -->

mov ax, 0x0200 ; Page table address at 0x2000
mov fs, ax ; Load 'fs'

mov bx, 0 ; First entry
mov edx, 0 ; First address

mov cx, 0x400 ; Set a counter to 1024 entries

.load_pt

or edx, 0x0003 ; Level S, R/W, present
mov [fs:bx], edx ; Insert entry
inc bx
inc bx ; Next entry
add edx, 0x800 ; Get next address

loop .load_pt

; Load CR3 with the page directory address -->

xor eax, eax
mov eax, 0x1000
mov cr3, eax

; Set the cr0 PG bit -->

mov eax, cr0              
or eax, 0x80000000
mov cr0, eax; <-- Here the computer crash (reset)

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My problem is that the computer reset as soon as I set the PG bit!

Furthermore, I like to know if I need to change some of my code, to run in 'paging' mode, or I can use my code as it is now?

Thank you very much!

PD. I am not an ASM expert... Is my code right?

JAER Mex2003

yea it won't work

1) are you trying to set up paging under real mode? I don't think it's a good idea, but if it is
2) each page dir and page tab entry is 4 byes long, you do: BX+=2, at the loops
3) XOR EAX, EAX MOV EAX, 0x1000
you don't have to XOR EAX, EAX

Cheers,
Adrian