Copy from chapter3

深碍√TFBOYSˉ_ 2024-02-17 15:55 11阅读 0赞

bochs目录：D:\\Program Files\\Bochs-2.6.8

freedos.img目录：D:\\Program Files\\Bochs-2.6.8

pm.img目录：D:\\Program Files\\Bochs-2.6.8

pmtest2.com目录：D:\\Program Files\\Bochs-2.6.8

bochsrc.bxrc配置文件：

\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#  
\# Configuration file for Bochs  
\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#  
  
  
\# how much memory the emulated machine will have  
megs: 32  
  
  
\# filename of ROM images  
romimage: file=BIOS-bochs-latest  
vgaromimage: file=VGABIOS-lgpl-latest  
  
  
\# what disk images will be used  
floppya: 1\_44=freedos.img, status=inserted  
floppyb: 1\_44=pm.img, status=inserted  
boot:a  
  
  
\# choose the boot disk.  
boot: floppy  
  
  
\# where do we send log messages?  
\# log: bochsout.txt  
  
  
\# disable the mouse  
mouse: enabled=0  
  
  
\# enable key mapping, using US layout as default.  
keyboard: keymap=x11-pc-us.map

汇编代码：

; ==========================================  
; pmtest2.asm  
; 编译方法：nasm pmtest2.asm -o pmtest2.com  
; ==========================================  
  
  
%include"pm.inc"; 常量, 宏, 以及一些说明  
  
  
org0100h  
jmpLABEL\_BEGIN  
  
  
\[SECTION .gdt\]  
; GDT  
; 段基址, 段界限 , 属性  
LABEL\_GDT: Descriptor 0, 0, 0 ; 空描述符  
LABEL\_DESC\_NORMAL: Descriptor 0, 0ffffh, DA\_DRW ; Normal 描述符  
LABEL\_DESC\_CODE32: Descriptor 0, SegCode32Len-1, DA\_C+DA\_32; 非一致代码段, 32  
LABEL\_DESC\_CODE16: Descriptor 0, 0ffffh, DA\_C ; 非一致代码段, 16  
LABEL\_DESC\_DATA: Descriptor 0, DataLen-1, DA\_DRW ; Data  
LABEL\_DESC\_STACK: Descriptor 0, TopOfStack, DA\_DRWA+DA\_32; Stack, 32 位  
LABEL\_DESC\_TEST: Descriptor 0500000h, 0ffffh, DA\_DRW  
LABEL\_DESC\_VIDEO: Descriptor 0B8000h, 0ffffh, DA\_DRW ; 显存首地址  
; GDT 结束  
  
  
GdtLenequ $ - LABEL\_GDT; GDT长度  
GdtPtrdw GdtLen - 1; GDT界限  
dd0; GDT基地址  
  
  
; GDT 选择子  
SelectorNormalequLABEL\_DESC\_NORMAL\- LABEL\_GDT  
SelectorCode32equLABEL\_DESC\_CODE32\- LABEL\_GDT  
SelectorCode16equLABEL\_DESC\_CODE16\- LABEL\_GDT  
SelectorDataequLABEL\_DESC\_DATA\- LABEL\_GDT  
SelectorStackequLABEL\_DESC\_STACK\- LABEL\_GDT  
SelectorTestequLABEL\_DESC\_TEST\- LABEL\_GDT  
SelectorVideoequLABEL\_DESC\_VIDEO\- LABEL\_GDT  
; END of \[SECTION .gdt\]  
  
  
\[SECTION .data1\]; 数据段  
ALIGN32  
\[BITS32\]  
LABEL\_DATA:  
SPValueInRealModedw0  
; 字符串  
PMMessage:db "In Protect Mode now. ^-^", 0; 在保护模式中显示  
OffsetPMMessageequPMMessage - $$  
StrTest:db "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 0  
OffsetStrTestequStrTest - $$  
DataLenequ $ - LABEL\_DATA  
; END of \[SECTION .data1\]  
  
  
  
  
; 全局堆栈段  
\[SECTION .gs\]  
ALIGN32  
\[BITS32\]  
LABEL\_STACK:  
times 512 db 0  
  
  
TopOfStackequ$ - LABEL\_STACK - 1  
  
  
; END of \[SECTION .gs\]  
  
  
  
  
\[SECTION .s16\]  
\[BITS16\]  
LABEL\_BEGIN:  
movax, cs  
movds, ax  
moves, ax  
movss, ax  
movsp, 0100h  
  
  
mov\[LABEL\_GO\_BACK\_TO\_REAL+3\], ax  
mov\[SPValueInRealMode\], sp  
  
  
; 初始化 16 位代码段描述符  
movax, cs  
movzxeax, ax  
shleax, 4  
addeax, LABEL\_SEG\_CODE16  
movword \[LABEL\_DESC\_CODE16 + 2\], ax  
shreax, 16  
movbyte \[LABEL\_DESC\_CODE16 + 4\], al  
movbyte \[LABEL\_DESC\_CODE16 + 7\], ah  
  
  
; 初始化 32 位代码段描述符  
xoreax, eax  
movax, cs  
shleax, 4  
addeax, LABEL\_SEG\_CODE32  
movword \[LABEL\_DESC\_CODE32 + 2\], ax  
shreax, 16  
movbyte \[LABEL\_DESC\_CODE32 + 4\], al  
movbyte \[LABEL\_DESC\_CODE32 + 7\], ah  
  
  
; 初始化数据段描述符  
xoreax, eax  
movax, ds  
shleax, 4  
addeax, LABEL\_DATA  
movword \[LABEL\_DESC\_DATA + 2\], ax  
shreax, 16  
movbyte \[LABEL\_DESC\_DATA + 4\], al  
movbyte \[LABEL\_DESC\_DATA + 7\], ah  
  
  
; 初始化堆栈段描述符  
xoreax, eax  
movax, ds  
shleax, 4  
addeax, LABEL\_STACK  
movword \[LABEL\_DESC\_STACK + 2\], ax  
shreax, 16  
movbyte \[LABEL\_DESC\_STACK + 4\], al  
movbyte \[LABEL\_DESC\_STACK + 7\], ah  
  
  
; 为加载 GDTR 作准备  
xoreax, eax  
movax, ds  
shleax, 4  
addeax, LABEL\_GDT; eax <- gdt 基地址  
movdword \[GdtPtr + 2\], eax; \[GdtPtr + 2\] <- gdt 基地址  
  
  
; 加载 GDTR  
lgdt\[GdtPtr\]  
  
  
; 关中断  
cli  
  
  
; 打开地址线A20  
inal, 92h  
oral, 00000010b  
out92h, al  
  
  
; 准备切换到保护模式  
moveax, cr0  
oreax, 1  
movcr0, eax  
  
  
; 真正进入保护模式  
jmpdword SelectorCode32:0; 执行这一句会把 SelectorCode32 装入 cs, 并跳转到 Code32Selector:0 处  
  
  
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;  
  
  
LABEL\_REAL\_ENTRY:; 从保护模式跳回到实模式就到了这里  
movax, cs  
movds, ax  
moves, ax  
movss, ax  
  
  
movsp, \[SPValueInRealMode\]  
  
  
inal, 92h; \`.  
andal, 11111101b; | 关闭 A20 地址线  
out92h, al; /  
  
  
sti; 开中断  
  
  
movax, 4c00h; \`.  
int21h; / 回到 DOS  
; END of \[SECTION .s16\]  
  
  
  
  
\[SECTION .s32\]; 32 位代码段. 由实模式跳入.  
\[BITS32\]  
  
  
LABEL\_SEG\_CODE32:  
movax, SelectorData  
movds, ax; 数据段选择子  
movax, SelectorTest  
moves, ax; 测试段选择子  
movax, SelectorVideo  
movgs, ax; 视频段选择子  
  
  
movax, SelectorStack  
movss, ax; 堆栈段选择子  
  
  
movesp, TopOfStack  
  
  
  
  
; 下面显示一个字符串  
movah, 0Ch; 0000: 黑底 1100: 红字  
xoresi, esi  
xoredi, edi  
movesi, OffsetPMMessage; 源数据偏移  
movedi, (80 \* 10 + 0) \* 2; 目的数据偏移。屏幕第 10 行, 第 0 列。  
cld  
.1:  
lodsb  
testal, al  
jz.2  
mov\[gs:edi\], ax  
addedi, 2  
jmp.1  
.2:; 显示完毕  
  
  
callDispReturn  
  
  
callTestRead  
callTestWrite  
callTestRead  
  
  
; 到此停止  
jmpSelectorCode16:0  
  
  
; ------------------------------------------------------------------------  
TestRead:  
xoresi, esi  
movecx, 8  
.loop:  
moval, \[es:esi\]  
callDispAL  
incesi  
loop.loop  
  
  
callDispReturn  
  
  
ret  
; TestRead 结束-----------------------------------------------------------  
  
  
  
  
; ------------------------------------------------------------------------  
TestWrite:  
pushesi  
pushedi  
xoresi, esi  
xoredi, edi  
movesi, OffsetStrTest; 源数据偏移  
cld  
.1:  
lodsb  
testal, al  
jz.2  
mov\[es:edi\], al  
incedi  
jmp.1  
.2:  
  
  
popedi  
popesi  
  
  
ret  
; TestWrite 结束----------------------------------------------------------  
  
  
  
  
; ------------------------------------------------------------------------  
; 显示 AL 中的数字  
; 默认地:  
;数字已经存在 AL 中  
;edi 始终指向要显示的下一个字符的位置  
; 被改变的寄存器:  
;ax, edi  
; ------------------------------------------------------------------------  
DispAL:  
pushecx  
pushedx  
  
  
movah, 0Ch; 0000: 黑底 1100: 红字  
movdl, al  
shral, 4  
movecx, 2  
.begin:  
andal, 01111b  
cmpal, 9  
ja.1  
addal, '0'  
jmp.2  
.1:  
subal, 0Ah  
addal, 'A'  
.2:  
mov\[gs:edi\], ax  
addedi, 2  
  
  
moval, dl  
loop.begin  
addedi, 2  
  
  
popedx  
popecx  
  
  
ret  
; DispAL 结束-------------------------------------------------------------  
  
  
  
  
; ------------------------------------------------------------------------  
DispReturn:  
pusheax  
pushebx  
moveax, edi  
movbl, 160  
divbl  
andeax, 0FFh  
inceax  
movbl, 160  
mulbl  
movedi, eax  
popebx  
popeax  
  
  
ret  
; DispReturn 结束---------------------------------------------------------  
  
  
SegCode32Lenequ$ - LABEL\_SEG\_CODE32  
; END of \[SECTION .s32\]  
  
  
  
  
; 16 位代码段. 由 32 位代码段跳入, 跳出后到实模式  
\[SECTION .s16code\]  
ALIGN32  
\[BITS16\]  
LABEL\_SEG\_CODE16:  
; 跳回实模式:  
movax, SelectorNormal  
movds, ax  
moves, ax  
movfs, ax  
movgs, ax  
movss, ax  
  
  
moveax, cr0  
andal, 11111110b  
movcr0, eax  
  
  
LABEL\_GO\_BACK\_TO\_REAL:  
jmp0:LABEL\_REAL\_ENTRY; 段地址会在程序开始处被设置成正确的值  
  
  
Code16Lenequ $ - LABEL\_SEG\_CODE16  
  
  
; END of \[SECTION .s16code\]

运行结果：

![20150705162002045][]

[20150705162002045]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/30/65bd44b9bb474607b7cda5aabee2cc00.png