【PM复习】页式存储

来源：互联网发布：淘宝教育视频全屏编辑：程序博客网时间：2024/06/04 18:31

书上说得很明白，无需赘言。

简单的一一对应的映射的代码如下：

Code:

%include "pm.inc"
org 0100h
jmp LABEL_BEGIN
[section .gdt]
LABEL_DESC_DUMMY:
Descriptor 0,0,0
LABEL_DESC_CODE32:
Descriptor 0,Code32_Len - 1,DA_C + DA_32
LABEL_DESC_CODE16:
Descriptor 0,Code16_Len - 1,DA_C
LABEL_DESC_VIDEO:
Descriptor 0b8000h,0ffffh,DA_DRW
LABEL_DESC_NORMAL:
Descriptor 0,0ffffh,DA_DRW
LABEL_DESC_DIR_BASE:
Descriptor 200000h,4095,DA_DRW
LABEL_DESC_TBL_BASE:
Descriptor 201000h,1023,DA_DRW + DA_LIMIT4K
GDT_Len equ $ - LABEL_DESC_DUMMY
GDT_Ptr:
dw GDT_Len - 1
dd 0
Selector_Code32 equ LABEL_DESC_CODE32 - LABEL_DESC_DUMMY
Selector_Code16 equ LABEL_DESC_CODE16 - LABEL_DESC_DUMMY
Selector_Video equ LABEL_DESC_VIDEO - LABEL_DESC_DUMMY
Selector_Normal equ LABEL_DESC_NORMAL - LABEL_DESC_DUMMY
Selector_Dir_Base equ LABEL_DESC_DIR_BASE - LABEL_DESC_DUMMY
Selector_Tbl_Base equ LABEL_DESC_TBL_BASE - LABEL_DESC_DUMMY
[section .s16]
[bits 16]
LABEL_BEGIN:
mov ax,cs
mov ds,ax
mov es,ax
mov [LABEL_GO_BACK_TO_REAL + 3],ax
Fill_Descriptor LABEL_DESC_CODE32,LABEL_CODE32
Fill_Descriptor LABEL_DESC_CODE16,LABEL_BEGIN
xor eax,eax
mov ax,ds
shl eax,4
add eax,LABEL_DESC_DUMMY
mov dword [GDT_Ptr + 2],eax
lgdt [GDT_Ptr]
cli
in al,92h
or al,00000010b
out 92h,al
mov eax,cr0
or al,1
mov cr0,eax
jmp Selector_Code32:0
_LABEL_PREPARE_GO_BACK_TO_REAL:
LABEL_PREPARE_GO_BACK_TO_REAL equ _LABEL_PREPARE_GO_BACK_TO_REAL - $$
mov ax,Selector_Normal
mov ds,ax
mov es,ax
mov gs,ax
mov fs,ax
mov eax,cr0
and al,11111110b
mov cr0,eax
LABEL_GO_BACK_TO_REAL:
jmp 0:LABEL_ALREADY_REAL
LABEL_ALREADY_REAL:
in al,92h
and al,11111101b
out 92h,al
sti
mov ax,4c00h
int 21h
Code16_Len equ $ -$$
[section .s32]
[bits 32]
LABEL_CODE32:
mov ax,Selector_Dir_Base
mov es,ax
xor edi,edi
cld
mov ecx,1024
mov eax,201000h + 7h
.1:
stosd
add eax,4096
loop .1
mov ax,Selector_Tbl_Base
mov es,ax
xor edi,edi
mov ecx,1024 * 1024
mov eax,7h
.2:
stosd
add eax,4096
loop .2
mov eax,200000h
mov cr3,eax
mov eax,cr0
or eax,80000000h
mov cr0,eax
mov ax,Selector_Video
mov gs,ax
mov ah,0ch
mov al,'x'
mov [gs:80 * 10],ax
jmp Selector_Code16:LABEL_PREPARE_GO_BACK_TO_REAL
Code32_Len equ $ - $$

结果如下：