;------------------------------------------------------------------------------
; @file
; Transition from 16 bit real mode into 32 bit flat protected mode
;
; Copyright (c) 2008 - 2010, Intel Corporation. All rights reserved.<BR>
; 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
;
; 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 [cs:bx]
mov eax, SEC_DEFAULT_CR0
mov cr0, eax
%ifdef __YASM__ ; VBox
jmp dword LINEAR_CODE_SEL:ADDR_OF(jumpTo32BitAndLandHere)
%else
jmp LINEAR_CODE_SEL:dword ADDR_OF(jumpTo32BitAndLandHere)
%endif
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
;
; Macros for GDT entries
;
%define PRESENT_FLAG(p) (p << 7)
%define DPL(dpl) (dpl << 5)
%define SYSTEM_FLAG(s) (s << 4)
%define DESC_TYPE(t) (t)
; Type: data, expand-up, writable, accessed
%define DATA32_TYPE 3
; Type: execute, readable, expand-up, accessed
%define CODE32_TYPE 0xb
; Type: execute, readable, expand-up, accessed
%define CODE64_TYPE 0xb
%define GRANULARITY_FLAG(g) (g << 7)
%define DEFAULT_SIZE32(d) (d << 6)
%define CODE64_FLAG(l) (l << 5)
%define UPPER_LIMIT(l) (l)
;
; The Global Descriptor Table (GDT)
;
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 ; sys flag, dpl, type
DB 0 ; limit 19:16, flags
DB 0 ; base 31:24
; linear data segment descriptor
LINEAR_SEL equ $-GDT_BASE
DW 0xffff ; limit 15:0
DW 0 ; base 15:0
DB 0 ; base 23:16
DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(DATA32_TYPE)
DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(1)|CODE64_FLAG(0)|UPPER_LIMIT(0xf)
DB 0 ; base 31:24
; linear code segment descriptor
LINEAR_CODE_SEL equ $-GDT_BASE
DW 0xffff ; limit 15:0
DW 0 ; base 15:0
DB 0 ; base 23:16
DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE32_TYPE)
DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(1)|CODE64_FLAG(0)|UPPER_LIMIT(0xf)
DB 0 ; base 31:24
%ifdef ARCH_X64
; linear code (64-bit) segment descriptor
LINEAR_CODE64_SEL equ $-GDT_BASE
DW 0xffff ; limit 15:0
DW 0 ; base 15:0
DB 0 ; base 23:16
DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE64_TYPE)
DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(0)|CODE64_FLAG(1)|UPPER_LIMIT(0xf)
DB 0 ; base 31:24
%endif
GDT_END: