1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
|
;------------------------------------------------------------------------------
;
; Copyright (c) 2008, 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.
;
; Module Name:
;
; 16RealTo32Flat.asm
;
; Abstract:
;
; Transition from 16 bit real mode into 32 bit flat protected mode
;
;------------------------------------------------------------------------------
%define SEC_DEFAULT_CR0 0x40000023
%define SEC_DEFAULT_CR4 0x640
BITS 16
to32BitFlat:
writeToSerialPort '1'
writeToSerialPort '6'
writeToSerialPort ' '
cli
mov bx, 0xf000
mov ds, bx
mov bx, ADDR16_OF(gdtr)
o32 lgdt [bx]
mov eax, SEC_DEFAULT_CR0
mov cr0, eax
; mov eax, cr0
; or al, 1
; mov cr0, eax
jmp LINEAR_CODE_SEL:dword ADDR_OF(jumpTo32BitAndLandHere)
BITS 32
jumpTo32BitAndLandHere:
mov eax, SEC_DEFAULT_CR4
mov cr4, eax
writeToSerialPort '3'
writeToSerialPort '2'
writeToSerialPort ' '
mov ax, LINEAR_SEL
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
jmp TransitionFrom16RealTo32FlatComplete
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:
|
