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|
;============================================================================
;演示特权指令的使用
;MASM9 + LINK5
;编译选项请参见 makefile TAB = 8
;============================================================================
.686p
Include pm.inc
option casemap:none
Stack_Len equ 1024 ;堆栈大小
;============================================================================
GdtSeg Segment use32 ;全局描述符
; ;段基址 ;段界限 ;属性
Dummy: Descriptor 0, 0, 0 ;空的描述符
Normal: Descriptor 0, 0ffffh, DA_DRW ;规范段描述符
g_CodeTempDesc: Descriptor 0, 0ffffh, DA_C ;非一致代码
g_StackDesc: Descriptor 0, Stack_Len-1, DA_DRW or 4000h ;32位堆栈段
g_DataDesc: Descriptor 0, 0fffffh, DA_DRWG ;全局4G数据段
g_DemoCodeDesc: Descriptor 0, DemoCodeSegLen-1, DA_C or DA_32 ;32位演示代码段描述符
g_VideoDesc: Descriptor 0b8000h,0ffffh, DA_DRW ;全局视频操作段
g_TestDesc: Descriptor 1111h, 0ffffh, DA_DRW ;测试描述符
;----------------------------------------------------------------------------
NormalSelector equ Normal - GdtSeg ;规范段选择子
g_DataSelector equ g_DataDesc - GdtSeg ;全局数据段
g_VideoSelector equ g_VideoDesc - GdtSeg ;全局视频段选择子
g_DemoCodeSelector equ g_DemoCodeDesc - GdtSeg ;演示代码段选择子
g_StackSelector equ g_StackDesc - GdtSeg ;0环堆栈段
g_CodeTempSelector equ g_CodeTempDesc - GdtSeg ;代码段选择子
g_TestSelector equ g_TestDesc - GdtSeg ;测试选择子
g_TestRSelector equ g_TestDesc - GdtSeg + SA_RPL3 ;测试选择子
;----------------------------------------------------------------------------
GDTLen equ $ - GdtSeg ;GDT长度
_RegSp word ? ;用于保存SS:SP
_RegSs word ?
;----------------------------------------------------------------------------
SzGdtMsg byte "RealMode GDT: 0x"
SzIdtMsg byte "RealMode IDT: 0x"
SzMswMsg byte "RealMode Msm: 0x"
SzCr0Msg byte "ProtectedMode CR0: 0x"
SzCr3Msg byte 0,"Cr3: 0x"
SzDr7Msg byte 0,"Dr7: 0x"
SzTrMsg byte "Tr: 0x"
SzLdtrMsg byte " Ldtr:0x"
SzLimitMsg byte 0, "Limit:"
GdtSeg Ends
;============================================================================
Stack0Seg Segment use32
byte Stack_Len dup(?)
Stack0Seg Ends
;============================================================================
g_DemoCodeSeg Segment use32 ;演示代码段
;============================================================================
;换行, _dwValue传递当前的行列号, 计算好在Eax中返回下一行开始
PrintLn Proc uses ebx _dwValue:dword
mov eax, _dwValue
mov bl, 160
div bl
and eax, 0FFh
inc eax
mov bl, 160
mul bl
ret
PrintLn Endp
;============================================================================
;;将al中的数字转成ASCII加上显示属性并在EAX中返回
HexToAscii Proc uses ebx
mov bl, al
and al, 0fh
add al, 90h
daa
adc al, 40h
daa
mov ah, 0ch
shl eax, 16 ;转换低位
mov al, bl
shr al, 4
and al, 0fh
add al, 90h
daa
adc al, 40h ;将高位转成ASCII
daa
mov ah, 0ch ;属性
ret
HexToAscii Endp
;----------------------------------------------------------------------------
;es:si-->字符串返回缓冲区, eax要转换的dword
DwordToHex Proc uses ebx ;dword转成字符串,
mov ebx, eax
shr eax, 16 + 8
call HexToAscii
stosd
mov eax, ebx
shr eax, 16
call HexToAscii
stosd
mov eax, ebx
shr eax, 8
call HexToAscii
stosd
mov eax, ebx
call HexToAscii
stosd
ret
DwordToHex Endp
;============================================================================
;ds->si要显示的字符串, es->di要显示的位置
ShowMsg Proc ;显示信息到屏幕上
@@: lodsb
mov ah, 0ah
stosw
loop @b
ret
ShowMsg Endp
;============================================================================
;显示控制寄存器值
ShowControlReg Proc
local _lpRealAddress:dword
local wBuf:word
;----------------------------------------------------------------------------
;实模式下的字符串地址, 换算成保护模式下的, 方法
;----------------------------------------------------------------------------
mov esi, GdtSeg
shl esi, 4
mov _lpRealAddress, esi
;----------------------------------------------------------------------------
lea esi, SzCr0Msg
add esi, _lpRealAddress
mov ecx, sizeof SzCr0Msg
call ShowMsg
mov eax, cr0
call DwordToHex ;显示cr0
;----------------------------------------------------------------------------
lea esi, SzCr3Msg
add esi, _lpRealAddress
mov ecx, sizeof SzCr3Msg
call ShowMsg
mov eax, cr3 ;显示CR3
call DwordToHex
;----------------------------------------------------------------------------
lea esi, SzDr7Msg
add esi, _lpRealAddress
mov ecx, sizeof SzDr7Msg
call ShowMsg
mov eax, dr7 ;调试寄存器dr7
call DwordToHex
;----------------------------------------------------------------------------
Invoke PrintLn, edi
mov edi,eax
add edi, (5+14) * 2 ;换行
lea esi, SzTrMsg
add esi, _lpRealAddress
mov ecx, sizeof SzTrMsg
call ShowMsg
str word ptr ss:[wBuf]
movzx eax, word ptr ss:[wBuf] ;Tr寄存器
call DwordToHex
;----------------------------------------------------------------------------
lea esi, SzLdtrMsg
add esi, _lpRealAddress
mov ecx, sizeof SzLdtrMsg
call ShowMsg
sldt word ptr ss:[wBuf]
movzx eax, word ptr ss:[wBuf] ;LDTR寄存器
call DwordToHex
;----------------------------------------------------------------------------
ret
ShowControlReg Endp
;----------------------------------------------------------------------------
_DemoEntry equ $ - g_DemoCodeSeg
DemoEntry Proc far
mov edi, 9 * 80 * 2 + 5 * 2 ;9行5列
Invoke ShowControlReg
;----------------------------------------------------------------------------
;测试调整申请特权级指令
mov ax, g_TestSelector
mov dx, g_TestRSelector
arpl ax, dx ;if (ax)rpl < (cx)rpl (ax)rpl = (cx)rpl
;----------------------------------------------------------------------------
;装载描述符的界限
mov bx, 0
mov ax, g_TestSelector
xor edx, edx
xor cx, cx
lsl edx, eax ;将opera2的选择子指向的界限装入
lsl cx, ax
;----------------------------------------------------------------------------
;装载描述符的属性字段
xor edx, edx
xor cx, cx
lar edx, eax
lar cx, ax
;----------------------------------------------------------------------------
;测试选择子指向的段是否可读
verr ax
jnz @f
;描述符是可读的
@@:
;----------------------------------------------------------------------------
;测试选择子指向的段是否可写
verw ax
jnz @f
;描述符是可写的
@@:
;----------------------------------------------------------------------------
;由于是从16位代码段跳转过来的, 压栈都是16位的, 这里是32位代码段, 所以
;必须扩展返回地址, 才能够正常的返回
;----------------------------------------------------------------------------
pop ax ;ip
pop cx ;cs
movzx ecx, cx
movzx eax, ax
push ecx ;cs
push eax ;eip
ret
DemoEntry Endp
DemoCodeSegLen equ $ - g_DemoCodeSeg
g_DemoCodeSeg Ends
;============================================================================
;16位段, 由实模式跳入
;============================================================================
g_Code16Seg Segment use16
_GoToProtect Proc ;返回实模式
mov ax, NormalSelector
mov fs, ax ;规范选择子
mov es, ax
mov ds, ax
mov ss, ax
mov gs, ax
mov eax, cr0 ;关PE位, 进入实模式
and al, 0feh
mov cr0, eax
;刷新段选择子缓冲区, 退回实模式
Jmp16 <seg StartCodeSeg >, < offset _RealProtect >
_GoToProtect Endp
;----------------------------------------------------------------------------
_ProtectEntry Proc ;实模式跳入入口
mov ax, g_StackSelector
mov ss, ax
mov esp, Stack_Len ;设置堆栈
mov ax, g_DataSelector ;设置源数据段
mov ds, ax
mov ax, g_VideoSelector
mov es, ax ;设置目标ES
;----------------------------------------------------------------------------
;这个比较给力, 从16位代码段跳转到32位代码段
CALL16 <g_DemoCodeSelector>, _DemoEntry ;演示特权指令
;----------------------------------------------------------------------------
call _GoToProtect ;返回保护模式
_ProtectEntry Endp
g_Code16Seg Ends
;============================================================================
StartCodeSeg Segment use16 ;实模式启动代码
_InitGdt Proc uses es ;初始化全局描述符表
local _fGdtPtr:fword
xor eax, eax
mov ax, GdtSeg
mov es, ax ;es-->全局描述符表
;----------------------------------------------------------------------------
shl eax, 4
mov dword ptr es:[_fGdtPtr+2], eax ;初始化VGDT描述符
mov word ptr es:[_fGdtPtr], GDTLen-1 ;GDT长度
;----------------------------------------------------------------------------
xor eax, eax
mov ax, g_Code16Seg ;初始化十六位的代码段
shl eax, 4
mov word ptr es:[g_CodeTempDesc+2], ax ;段基址低位
shr eax, 16
mov byte ptr es:[g_CodeTempDesc+4], al ;段基址高地址低位
mov byte ptr es:[g_CodeTempDesc+7], ah ;段基址高地址高位
;----------------------------------------------------------------------------
xor eax, eax
mov ax, g_DemoCodeSeg ;初始化32位的演示代码段
shl eax, 4
mov word ptr es:[g_DemoCodeDesc+2], ax
shr eax, 16
mov byte ptr es:[g_DemoCodeDesc+4], al
mov byte ptr es:[g_DemoCodeDesc+7], ah
;----------------------------------------------------------------------------
xor eax, eax
mov ax, Stack0Seg ;初始化32位的演示堆栈
shl eax, 4
mov word ptr es:[g_StackDesc+2], ax
shr eax, 16
mov byte ptr es:[g_StackDesc+4], al
mov byte ptr es:[g_StackDesc+7], ah
;----------------------------------------------------------------------------
lgdt fword ptr ss:[_fGdtPtr] ;装载GDT
ret
_InitGdt Endp
;============================================================================
;;将al中的数字转成ASCII加上显示属性并在EAX中返回
_HexToAscii Proc uses ebx
mov bl, al
and al, 0fh
add al, 90h
daa
adc al, 40h
daa
mov ah, 0ah
shl eax, 16 ;转换低位
mov al, bl
shr al, 4
and al, 0fh
add al, 90h
daa
adc al, 40h ;将高位转成ASCII
daa
mov ah, 0ah ;属性
ret
_HexToAscii Endp
;----------------------------------------------------------------------------
;es:si-->字符串返回缓冲区, eax要转换的dword
_DwordToHex Proc uses ebx ;dword转成字符串,
mov ebx, eax
shr eax, 16 + 8
call _HexToAscii
stosd
mov eax, ebx
shr eax, 16
call _HexToAscii
stosd
mov eax, ebx
shr eax, 8
call _HexToAscii
stosd
mov eax, ebx
call _HexToAscii
stosd
ret
_DwordToHex Endp
;----------------------------------------------------------------------------
;es:di-->字符串写入的缓冲区, ax要转换的word
_WordToHex Proc uses bx
mov bx, ax
shr ax, 8
call _HexToAscii
stosd
mov ax, bx
call _HexToAscii
stosd
ret
_WordToHex Endp
;============================================================================
;换行, _dwValue传递当前的行列号, 计算好在Eax中返回下一行开始
_PrintLn Proc uses ebx _dwValue:dword
mov eax, _dwValue
mov bl, 160
div bl
and eax, 0FFh
inc eax
mov bl, 160
mul bl
ret
_PrintLn Endp
;============================================================================
;ds->si要显示的字符串, es->di要显示的位置
_ShowMsg Proc ;显示信息到屏幕上
@@: lodsb
mov ah, 0ch
stosw
loop @b
ret
_ShowMsg Endp
;============================================================================
_ShowRegister Proc uses es ds ;演示实模式下可以使用的特权指令
local _fRegBuf:fword
local _wBuf:word
sgdt fword ptr ss:[_fRegBuf] ;读取实模式下的GDT
mov edi, 80 * 2 * 5 + 5 * 2 ;5行5列
mov ax, 0b800h
mov es, ax
cld
;----------------------------------------------------------------------------
;显示GDT
mov ax, GdtSeg
mov ds, ax
lea si, SzGdtMsg
mov cx, sizeof SzGdtMsg
call _ShowMsg
mov eax, dword ptr ss:[_fRegBuf+2]
call _DwordToHex ;显示GDT基址
lea si, SzLimitMsg
mov cx, sizeof SzLimitMsg
call _ShowMsg
mov ax, word ptr ss:[_fRegBuf]
call _WordToHex ;显示GDT限长
;----------------------------------------------------------------------------
Invoke _PrintLn, edi ;换行
mov edi, eax
add edi, 5 * 2
;显示IDT
sidt fword ptr ss:[_fRegBuf] ;读取实模式下的IDT
lea si, SzIdtMsg
mov cx, sizeof SzIdtMsg
call _ShowMsg
mov eax, dword ptr ss:[_fRegBuf+2]
call _DwordToHex ;显示GDT基址
lea si, SzLimitMsg
mov cx, sizeof SzLimitMsg
call _ShowMsg
mov ax, word ptr ss:[_fRegBuf]
call _WordToHex ;显示GDT限长
;----------------------------------------------------------------------------
smsw word ptr [_wBuf] ;显示CR0的低16位
Invoke _PrintLn, edi ;换行
mov edi, eax
add edi, 5 * 2
lea si, SzMswMsg
mov cx, sizeof SzMswMsg
call _ShowMsg
mov ax, word ptr ss:[_wBuf]
call _WordToHex ;显示MSW
;----------------------------------------------------------------------------
ret
_ShowRegister Endp
;============================================================================
Jmain Proc ;启动入口
call _ShowRegister ;显示实模式的关键寄存器
call _InitGdt ;初始化GDT全局描述符
;----------------------------------------------------------------------------
mov ax, GdtSeg
mov ds, ax
mov ds:[_RegSs], ss
mov ds:[_RegSp], sp ;保存SS:SP
_EnableA20 ;关中断开A20地址线
mov eax, cr0
or eax, 1
mov cr0, eax ;开启分段, 进入保护模式
;----------------------------------------------------------------------------
Jmp16 g_CodeTempSelector, <offset _ProtectEntry>;跳入保护模式
Jmain Endp
;----------------------------------------------------------------------------
_RealProtect Proc ;返回保护模式
mov ax, GdtSeg
mov ds, ax
lss sp, dword ptr ds:[_RegSp] ;恢复SS:SP
_DisableA20 ;关A20地址线, 开中断
sti
mov ax, 4c00h
int 21h
_RealProtect Endp
StartCodeSeg Ends
End Jmain
|
