youngray 标签: 程序代码如下 1: %include "pm.inc" 2: 3: org 0100h 4: jmp LABEL_BEGIN 5: 6: [section .gdt] 7: GDT_BEGIN: ;空描述符,Intel规定必须要有该描述符 8: Descriptor 0, 0, 0 9: GDT_NORMAL: ;Normal描述符,从保护模式返回实模式时,用到该描述符 10: Descriptor 0, 0ffffh, DA_DRW 11: GDT_CODE16: ;该描述符指向保护模式下的16位代码段 12: Descriptor 0, 0ffffh, DA_C 13: GDT_CODE32: ;该描述符指向保护模式下的32位代码段 14: Descriptor 0, SegCode32Len - 1, DA_C + DA_32 15: GDT_DATA: ;该描述指向保护模式下要用到的数据段 16: Descriptor 0, SegDataLen - 1, DA_DRW 17: GDT_STACK: ;该描述符指向保护模式下要用到的堆栈段 18: Descriptor 0, TopOfStack, DA_DRWA + DA_32 19: GDT_TEST: ;该描述符指向测试字符串的物理地址 20: Descriptor 0500000h, 0ffffh, DA_DRW 21: GDT_VIDEO: ;该描述符指向显存首地址 22: Descriptor 0b8000h, 0ffffh, DA_DRW 23: 24: Gdt_Len equ $ - GDT_BEGIN 25: GdtPtr dw Gdt_Len - 1 26: dd 0 ;这里的0起到保留内存空间的作用,不做为实际值 27: 28: ; 定义 GDT 选择子 29: SelectorNormal equ GDT_NORMAL - GDT_BEGIN 30: SelectorCode16 equ GDT_CODE16 - GDT_BEGIN 31: SelectorCode32 equ GDT_CODE32 - GDT_BEGIN 32: SelectorData equ GDT_DATA - GDT_BEGIN 33: SelectorStack equ GDT_STACK - GDT_BEGIN 34: SelectorTest equ GDT_TEST - GDT_BEGIN 35: SelectorVideo equ GDT_VIDEO - GDT_BEGIN 36: 37: [section .data1] ;保护模式下要用到的数据段 38: align 32 39: [bits 32] 40: LABEL_DATA: 41: SPValueInReal dw 0 ;该变量保存实模式下sp指针的值 42: PMMessage db "In Protect Mode now. ^-^", 0 ;在保护模式中显示 43: PMMessageOffset equ PMMessage - $$ 44: TestStr db "ABCDEFGH", 0 ;测试字符串 45: TestStrOffset equ TestStr - $$ 46: SegDataLen equ $ - LABEL_DATA 47: 48: [section .gs] ;保护模式下要用到的全局堆栈段 49: align 32 50: [bits 32] 51: LABEL_STACK: 52: times 512 db 0 53: TopOfStack equ $ - LABEL_STACK - 1 54: 55: [section .s16] 56: [bits 16] 57: LABEL_BEGIN: ;程序从这里开始执行 58: mov ax, cs 59: mov ds, ax 60: mov es, ax 61: mov ss, ax 62: mov sp, 0100h 63: 64: ;保存实模式下cs段寄存器的值到LABEL_GO_BACK_TO_REAL + 3所指向的地址处 65: mov [LABEL_GO_BACK_TO_REAL+3], ax 66: mov [SPValueInReal], sp ;保存实模式下sp指针的值到SPValueInReal变量 67: 68: ;初始化16位代码段描述符GDT_CODE16的基址值 69: xor eax, eax 70: mov ax , cs ;将cs段寄存器的值传送到ax 71: shl eax, 4 ;将ax中段地址左移位 72: add ax , LABEL_CODE16 ;将LABEL_CODE16的偏移地址加到ax,得到它的物理地址 73: mov [GDT_CODE16 + 2], ax ;将该物理地址分三部分分别放入描述符GDT_CODE16 74: shr eax, 16 ;中,具体的放置位置已经由Intel规定好了,你只须 75: mov [GDT_CODE16 + 4], al ;按照GDT描述符的规定把相应位置的值放进去即可 76: mov [GDT_CODE16 + 7], ah ;此时,GDT_CODE16的基址值初始化完毕 77: 78: ;初始化32位代码段描述符GDT_CODE32的基址值 79: xor eax, eax 80: mov ax , cs 81: shl eax, 4 82: add ax, LABEL_CODE32 83: mov [GDT_CODE32 + 2], ax 84: shr eax, 16 85: mov [GDT_CODE32 + 4], al 86: mov [GDT_CODE32 + 7], ah 87: 88: ;初始化数据段描述符GDT_DATA的基址值 89: xor eax, eax 90: mov ax , ds ;ds的值在上面的代码被置为cs的值 91: shl eax, 4 92: add eax, LABEL_DATA 93: mov [GDT_DATA + 2], ax 94: shr eax, 16 95: mov [GDT_DATA + 4], al 96: mov [GDT_DATA + 7], ah 97: 98: ;初始化堆栈段描述符GDT_STACK的基址值 99: xor eax, eax 100: mov ax , ds 101: shl eax, 4 102: add eax, LABEL_STACK 103: mov [GDT_STACK + 2], ax 104: shr eax, 16 105: mov [GDT_STACK + 4], al 106: mov [GDT_STACK + 7], ah 107: 108: ;为加载 GDTR 作准备 109: xor eax, eax 110: mov ax , ds 111: shl eax, 4 112: add eax, GDT_BEGIN 113: mov [GdtPtr + 2], eax 114: 115: ;加载 GDTR 116: lgdt [GdtPtr] 117: 118: ;关中断 119: cli 120: ;打开A20地址线 121: in al, 92h 122: or al, 00000010b 123: out 92h, al 124: ;打开进入保护模式的开关,该开关位于cr0寄存器的第0位 125: mov eax, cr0 126: or eax, 1 127: mov cr0, eax 128: 129: ;真正进入保护模式 130: jmp dword SelectorCode32:0 ;为了防止发生地址截断,这里的dword必不可少 131: 132: LABEL_REAL_ENTRY: ;从保护模式跳回实模式就到了这里 133: mov ax, cs 134: mov ds, ax 135: mov es, ax 136: mov ss, ax 137: mov sp, [SPValueInReal] 138: 139: ;关闭A20地址线 140: in al, 92h 141: and al, 11111101b 142: out 92h, al 143: ;开中断 144: sti 145: 146: ;返回 DOS 147: mov ax, 4c00h 148: int 21h
1: #include <stdio.h> 2: int main() 3: { 4: printf("NOT helloWorld~/n"); 5: return 0 6: }
1: #include <stdio.h> 2: int main() 3: { 4: printf("NOT helloWorld~/n"); 5: return 0 6: } 1: #include <stdio.h> 2: int main() 3: { 4: printf("NOT helloWorld~/n"); 5: return 0 6: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }
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