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Code: Select all

; TODO
; 1. Load Kernel at 0x10000
; 2. Enter to the PM
; 3. Jump to Kernel

; 2004-06-15 changed for nasm


[BITS 16]
ORG 0x0000

start:
   db   0x66
   lgdt   [gdt_desc]

   mov   eax,cr0
   or   al,1
   mov   cr0,eax

   jmp   dword 0x0008:0x1000+next


[BITS 32]
next:
   nop
   nop
   
   cli
   mov   ax,10h
   mov   ds,ax
   mov   es,ax
   mov   fs,ax
   mov   gs,ax
   mov   ss,ax
   mov   esp,(2*1024*1024)
   sti
   
   mov   byte [0x0b8000],'X'
   mov   byte [0x0b8001],0x1b

hang:
   jmp hang

   ;IMPL ME
   ;Enter to the Kernel
   ;call   _test 

gdt_desc:
      dw   0x0004*0x08
      dd   gdt+0x1000
;gdt_48:;
;   dw   0x0004*0x08      ; gdt limit=4 max GDT entries
;   dd   BIG_GDT+0x7c00   ; gdt base

;------------------------------------------------------------------------------
; NULL DESCRIPTER
;------------------------------------------------------------------------------
ALIGN   4
gdt   db      0,0,0,0
   db      0,0,0,0

;------------------------------------------------------------------------------
; DESCRIPTER #1
; Index 08h
; Base 0 / Limit FFFFFFFFh
; Code/Readable/Nonconforming
; Level 0
;------------------------------------------------------------------------------
   dw      0ffffh      ; 0-15   Limit
   dw      0h      ; 16-31   Base
   db      0h      ; 0-7   Base
   db      10011010b   ; 8-15   Type Privilege Present
   db      11001111b   ; 16-23   Limit Attr Granularity
   db      0h      ; 24-31 Base

;------------------------------------------------------------------------------
; DESCRIPTER #2
; Index 10h
; Base 0 / Limit FFFFFFFFh
; Data/
; Level 0
;------------------------------------------------------------------------------
   dw      0ffffh      ; 0-15   Limit
   dw      0h      ; 16-31   Base
   db      0h      ; 0-7   Base
   db      10010010b   ; 8-15   Type Privilege Present
   db      11001111b   ; 16-23   Limit Attr Granularity
   db      0h      ; 24-31 Base

gdt_size   equ   $ - gdt ;in bytes

   END

Code: Select all

[BITS 16]
ORG 0x0

start:
   lgdt [gdt_desc]
   cli
   mov   eax,cr0
   or   al,1
   mov   cr0,eax
   jmp   dword 0x0008:next

[BITS 32]
next:
   mov   ax,10h
   mov   ds,ax
   mov   es,ax
   mov   fs,ax
   mov   gs,ax
   mov   ss,ax
   mov   esp,(2*1024*1024)
   
   mov   byte [0x0b8000],'X'
   mov   byte [0x0b8001],0x1b

hang:
   jmp hang

;------------------------------------------------------------------------------
; NULL DESCRIPTOR and gdt_desc
;------------------------------------------------------------------------------
ALIGN   16
gdt:
gdt_desc:
      dw   0x0004*0x08
      dd   gdt
ALIGN   16

{snipped - other descriptors same as before}