0x06_自制操作系统My-OS，IDT,GDT,PIC初始化，实现键盘中断

把class03改成class04

IDT,GDT,PIC

我来介绍什么是IDT和GDT，PIC，怎么实现键盘中断

GDT全局描述表在16位CPU用不到，到了32位CPU要用。

16位CPU实模式用基地址x16+偏移地址去寻找内存地址，到了32位也用基地址x16+偏移地址找地址但是，32位CPU有保护模式，防止程序乱访问内存

所以用GDT

IDT，Interrupt Descriptor Table，即中断描述符表，用来联系中断和处理函数的，比如A中断发生->执行B函数

PIC（可编程中断控制器），中断是由PIC产生的

这是我自己的理解，你要想搞明白得自己去找资料

实现键盘中断

键盘按下-PIC收到发起中断-CPU处理中断-执行对应函数

这是我自己意淫的，具体怎么回事你得自己找资料

首先初始化pic，gdt，idt

创建文件dsctbl.c

/* GDT、IDT、descriptor table 关系处理 */

#include "include/head.h"

void init_gdtidt(void)
{
    struct SEGMENT_DESCRIPTOR *gdt = (struct SEGMENT_DESCRIPTOR *) ADR_GDT;
    struct GATE_DESCRIPTOR    *idt = (struct GATE_DESCRIPTOR    *) ADR_IDT;
    int i;

    /* GDT初始化 */
    for (i = 0; i <= LIMIT_GDT / 8; i++) {
        set_segmdesc(gdt + i, 0, 0, 0);
    }
    set_segmdesc(gdt + 1, 0xffffffff,   0x00000000, AR_DATA32_RW);
    set_segmdesc(gdt + 2, LIMIT_BOTPAK, ADR_BOTPAK, AR_CODE32_ER);
    load_gdtr(LIMIT_GDT, ADR_GDT);

    /* IDT初始化 */
    for (i = 0; i <= LIMIT_IDT / 8; i++) {
        set_gatedesc(idt + i, 0, 0, 0);
    }
    load_idtr(LIMIT_IDT, ADR_IDT);

    /* IDT设置*/    set_gatedesc(idt + 0x21, (int) asm_inthandler21, 2 * 8, AR_INTGATE32);
/* IDT的设定 */
    return;
}

void set_segmdesc(struct SEGMENT_DESCRIPTOR *sd, unsigned int limit, int base, int ar)
{
    if (limit > 0xfffff) {
        ar |= 0x8000; /* G_bit = 1 */
        limit /= 0x1000;
    }
    sd->limit_low    = limit & 0xffff;
    sd->base_low     = base & 0xffff;
    sd->base_mid     = (base >> 16) & 0xff;
    sd->access_right = ar & 0xff;
    sd->limit_high   = ((limit >> 16) & 0x0f) | ((ar >> 8) & 0xf0);
    sd->base_high    = (base >> 24) & 0xff;
    return;
}

void set_gatedesc(struct GATE_DESCRIPTOR *gd, int offset, int selector, int ar)
{
    gd->offset_low   = offset & 0xffff;
    gd->selector     = selector;
    gd->dw_count     = (ar >> 8) & 0xff;
    gd->access_right = ar & 0xff;
    gd->offset_high  = (offset >> 16) & 0xffff;
    return;
}

加粗的地方就是注册21号键盘中断处理函数到IDT

head.h

/*naskfunc.asm*/
void io_stihlt();
void io_hlt(void);
void io_cli(void);
void io_sti(void);
int io_get8(int port);
void io_set8(int port, int data);
void write_mem8(int addr, int data);
int io_load_eflags(void);
void io_store_eflags(int eflags);

　void load_gdtr(int limit, int addr);

　void load_idtr(int limit, int addr);

void asm_inthandler21(void);

/* asmhead.nas */
struct BOOTINFO { /* 0x0ff0-0x0fff */
    char cyls; /* 启动区读磁盘读到此为止 */
    char leds; /* 启动时键盘的LED的状态 */
    char vmode; /* 显卡模式为多少位彩色 */
    char reserve;
    short scrnx, scrny; /* 画面分辨率 */
    char *vram;
};
#define ADR_BOOTINFO 0x00000ff0

/*graphic.c*/
void init_palette(void);
void set_palette(int start, int end, unsigned char *rgb);
void boxfill8(unsigned char *vram, int xsize, unsigned char c, int x0, int y0, int x1, int y1);
void putfont8(char *vram, int xsize, int x, int y, char c, char *font);
void putfonts8_asc(char *vram, int xsize, int x, int y, char c, unsigned char *s);

/*font*/
extern char font[4096];

/* dsctbl.c */
struct SEGMENT_DESCRIPTOR {
    short limit_low, base_low;
    char base_mid, access_right;
    char limit_high, base_high;
};
struct GATE_DESCRIPTOR {
    short offset_low, selector;
    char dw_count, access_right;
    short offset_high;
};
void init_gdtidt(void);
void set_segmdesc(struct SEGMENT_DESCRIPTOR *sd, unsigned int limit, int base, int ar);
void set_gatedesc(struct GATE_DESCRIPTOR *gd, int offset, int selector, int ar);
#define ADR_IDT            0x0026f800
#define LIMIT_IDT        0x000007ff
#define ADR_GDT            0x00270000
#define LIMIT_GDT        0x0000ffff
#define ADR_BOTPAK        0x00280000
#define LIMIT_BOTPAK    0x0007ffff
#define AR_DATA32_RW    0x4092
#define AR_CODE32_ER    0x409a
#define AR_INTGATE32    0x008e

/* pic.c */
void init_pic(void);
#define PIC0_ICW1        0x0020
#define PIC0_OCW2        0x0020
#define PIC0_IMR        0x0021
#define PIC0_ICW2        0x0021
#define PIC0_ICW3        0x0021
#define PIC0_ICW4        0x0021
#define PIC1_ICW1        0x00a0
#define PIC1_OCW2        0x00a0
#define PIC1_IMR        0x00a1
#define PIC1_ICW2        0x00a1
#define PIC1_ICW3        0x00a1
#define PIC1_ICW4        0x00a1

/*interrupt.c*/

void inthandler21(int *esp);

加粗的地方就是增加的地方

naskfunc.asm

; naskfunc
; TAB=4

[FORMAT "WCOFF"]                ; 制作目标文件的模式
[INSTRSET "i486p"]                ; 使用到486为止的指令
[BITS 32]                        ; 3制作32位模式用的机器语言
[FILE "naskfunc.asm"]            ; 文件名
    GLOBAL _io_hlt,_write_mem8,_io_cli,_io_sti,_io_get8,_io_set8,_io_stihlt
    GLOBAL _io_load_eflags,_io_store_eflags,_asm_inthandler21
    GLOBAL    _load_gdtr, _load_idtr
    EXTERN    _inthandler21

[SECTION .text]

_io_hlt:    ; void io_hlt(void);
        HLT
        RET

_io_cli:    ; void io_cli(void);
        CLI
        RET

_io_sti:    ; void io_sti(void);
        STI
        RET

_io_get8:    ; int io_get8(int port);
        MOV        EDX,[ESP+4]        ; port
        MOV        EAX,0
        IN        AL,DX
        RET

_io_set8:    ; void io_set8(int port, int data);
        MOV        EDX,[ESP+4]        ; port
        MOV        AL,[ESP+8]        ; data
        OUT        DX,AL
        RET

_io_stihlt:    ; void io_stihlt(void);
        STI
        HLT
        RET

_write_mem8: ; void write_mem8(int addr, int data);
        MOV ECX,[ESP+4] ; taking content of add
        MOV AL,[ESP+8] ; taking content of data
        MOV [ECX],AL ; *ecx=al
        RET
_io_load_eflags:    ; int io_load_eflags(void);
        PUSHFD        ; PUSH EFLAGS
        POP        EAX
        RET

_io_store_eflags:    ; void io_store_eflags(int eflags);
        MOV        EAX,[ESP+4]
        PUSH    EAX
        POPFD        ; POP EFLAGS
        RET
_load_gdtr:        ; void load_gdtr(int limit, int addr);
        MOV        AX,[ESP+4]        ; limit
        MOV        [ESP+6],AX
        LGDT    [ESP+6]
        RET

_load_idtr:        ; void load_idtr(int limit, int addr);
        MOV        AX,[ESP+4]        ; limit
        MOV        [ESP+6],AX
        LIDT    [ESP+6]
        RET
_asm_inthandler21:
        PUSH    ES
        PUSH    DS
        PUSHAD
        MOV        EAX,ESP
        PUSH    EAX
        MOV        AX,SS
        MOV        DS,AX
        MOV        ES,AX
        CALL    _inthandler21
        POP        EAX
        POPAD
        POP        DS
        POP        ES
        IRETD

加粗的地方就是要修改的地方

IDT-->_asm_inthandler21-->_inthandler21函数

新建pic.c

/*初始化关系 */

#include "include/head.h"

void init_pic(void)
/* PIC初始化 */
{
    io_set8(PIC0_IMR,  0xff  ); /* 禁止所有中断 */
    io_set8(PIC1_IMR,  0xff  ); /* 禁止所有中断 */

    io_set8(PIC0_ICW1, 0x11  ); /* 边缘触发模式（edge trigger mode） */
    io_set8(PIC0_ICW2, 0x20  ); /* IRQ0-7由INT20-27接收 */
    io_set8(PIC0_ICW3, 1 << 2); /* PIC1由IRQ2相连 */
    io_set8(PIC0_ICW4, 0x01  ); /* 无缓冲区模式 */

    io_set8(PIC1_ICW1, 0x11  ); /* 边缘触发模式（edge trigger mode） */
    io_set8(PIC1_ICW2, 0x28  ); /* IRQ8-15由INT28-2f接收 */
    io_set8(PIC1_ICW3, 2     ); /* PIC1由IRQ2连接 */
    io_set8(PIC1_ICW4, 0x01  ); /* 无缓冲区模式 */

    io_set8(PIC0_IMR,  0xfb  ); /* 11111011 PIC1以外全部禁止 */
    io_set8(PIC1_IMR,  0xff  ); /* 11111111 禁止所有中断 */

    return;
}

创建interrupt.c

#include "include/head.h"

void inthandler21(int *esp)
/* 来自PS/2键盘的中断 */
{
    struct BOOTINFO *binfo = (struct BOOTINFO *) ADR_BOOTINFO;
    boxfill8(binfo->vram, binfo->scrnx, 7, 0, 0, 32 * 8 - 1, 15);
    putfonts8_asc(binfo->vram, binfo->scrnx, 0, 0, 0, "INT 21 (IRQ-1) :PS/2 keyboard");
    for (;;) {
        io_hlt();
    }
}

最后修改mian.c

#include "include/head.h"
#include <string.h>

struct BOOTINFO *binfo = (struct BOOTINFO *) ADR_BOOTINFO;

void Main(void){
    int i;char s[256];

    init_gdtidt();
    init_pic();
    io_sti();

    init_palette();

    boxfill8(binfo->vram, binfo->scrnx, 0,0,0,binfo->scrnx, binfo->scrny);
    sprintf(s, "scrnx = %d", binfo->scrnx);
    putfonts8_asc(binfo->vram, binfo->scrnx, 8, 8, 7, s);
    io_set8(PIC0_IMR, 0xf9); /* 开放PIC1和键盘中断(11111001) */

    for (;;) {
        io_hlt();
    }
}

别忘了编译之改一下makefile

 运行：

cd class02
..\z_tools\make.exe run

 

自制操作系统合集

原文地址：https://www.cnblogs.com/Frank-dev-blog/category/2249116.html

项目github地址rick521/My-OS (github.com)给我点颗star