audk/OvmfPkg/ResetVector/Ia16/16RealTo32Flat.asm

141 lines
3.9 KiB
NASM
Raw Normal View History

;------------------------------------------------------------------------------
; @file
; Transition from 16 bit real mode into 32 bit flat protected mode
;
; Copyright (c) 2008 - 2009, Intel Corporation
; All rights reserved. This program and the accompanying materials
; are licensed and made available under the terms and conditions of the BSD License
; which accompanies this distribution. The full text of the license may be found at
; http://opensource.org/licenses/bsd-license.php
;
; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
;
;------------------------------------------------------------------------------
%define SEC_DEFAULT_CR0 0x40000023
%define SEC_DEFAULT_CR4 0x640
BITS 16
;
; Modified: EAX, EBX
;
TransitionFromReal16To32BitFlat:
debugShowPostCode POSTCODE_16BIT_MODE
cli
mov bx, 0xf000
mov ds, bx
mov bx, ADDR16_OF(gdtr)
o32 lgdt [bx]
mov eax, SEC_DEFAULT_CR0
mov cr0, eax
jmp LINEAR_CODE_SEL:dword ADDR_OF(jumpTo32BitAndLandHere)
BITS 32
jumpTo32BitAndLandHere:
mov eax, SEC_DEFAULT_CR4
mov cr4, eax
debugShowPostCode POSTCODE_32BIT_MODE
mov ax, LINEAR_SEL
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
OneTimeCallRet TransitionFromReal16To32BitFlat
ALIGN 2
gdtr:
dw GDT_END - GDT_BASE - 1 ; GDT limit
dd ADDR_OF(GDT_BASE)
ALIGN 16
GDT_BASE:
; null descriptor
NULL_SEL equ $-GDT_BASE
dw 0 ; limit 15:0
dw 0 ; base 15:0
db 0 ; base 23:16
db 0 ; type
db 0 ; limit 19:16, flags
db 0 ; base 31:24
; linear data segment descriptor
LINEAR_SEL equ $-GDT_BASE
dw 0FFFFh ; limit 0xFFFFF
dw 0 ; base 0
db 0
db 092h ; present, ring 0, data, expand-up, writable
db 0CFh ; page-granular, 32-bit
db 0
; linear code segment descriptor
LINEAR_CODE_SEL equ $-GDT_BASE
dw 0FFFFh ; limit 0xFFFFF
dw 0 ; base 0
db 0
db 09Ah ; present, ring 0, data, expand-up, writable
db 0CFh ; page-granular, 32-bit
db 0
; system data segment descriptor
SYS_DATA_SEL equ $-GDT_BASE
dw 0FFFFh ; limit 0xFFFFF
dw 0 ; base 0
db 0
db 092h ; present, ring 0, data, expand-up, writable
db 0CFh ; page-granular, 32-bit
db 0
; system code segment descriptor
SYS_CODE_SEL equ $-GDT_BASE
dw 0FFFFh ; limit 0xFFFFF
dw 0 ; base 0
db 0
db 09Ah ; present, ring 0, data, expand-up, writable
db 0CFh ; page-granular, 32-bit
db 0
; spare segment descriptor
LINEAR_CODE64_SEL equ $-GDT_BASE
DW -1 ; LimitLow
DW 0 ; BaseLow
DB 0 ; BaseMid
DB 9bh
DB 0afh ; LimitHigh (CS.L=1, CS.D=0)
DB 0 ; BaseHigh
; spare segment descriptor
SPARE4_SEL equ $-GDT_BASE
dw 0 ; limit 0xFFFFF
dw 0 ; base 0
db 0
db 0 ; present, ring 0, data, expand-up, writable
db 0 ; page-granular, 32-bit
db 0
; spare segment descriptor
SPARE5_SEL equ $-GDT_BASE
dw 0 ; limit 0xFFFFF
dw 0 ; base 0
db 0
db 0 ; present, ring 0, data, expand-up, writable
db 0 ; page-granular, 32-bit
db 0
GDT_END: