学习笔记

使用教材（配书源码以及使用方法）
《一个64位操作系统的设计与实现》
http://www.ituring.com.cn/book/2450
https://www.jianshu.com/p/28f9713a9171

源码结构

• 配书代码包 ：第4章 \ 程序 \ 程序4-10

程序4-10 运行结果

[anno@localhost bootloader]$ make
nasm boot.asm -o boot.bin
nasm loader.asm -o loader.bin

[anno@localhost kernel]$ make
gcc -E  head.S > head.s
as --64 -o head.o head.s
gcc -E  entry.S > entry.s
as --64 -o entry.o entry.s
gcc  -mcmodel=large -fno-builtin -m64 -c main.c
gcc  -mcmodel=large -fno-builtin -m64 -c printk.c
gcc  -mcmodel=large -fno-builtin -m64 -c trap.c
gcc  -mcmodel=large -fno-builtin -m64 -c memory.c
gcc  -mcmodel=large -fno-builtin -m64 -c interrupt.c
ld -b elf64-x86-64 -z muldefs -o system head.o entry.o main.o printk.o trap.o memory.o interrupt.o -T Kernel.lds 
objcopy -I elf64-x86-64 -S -R ".eh_frame" -R ".comment" -O binary system kernel.bin

[anno@localhost 4-10]$ sudo mount boot.img media -t vfat -o loop
[anno@localhost 4-10]$ sudo cp bootloader/loader.bin media
[anno@localhost 4-10]$ sync
[anno@localhost 4-10]$ sudo cp bootloader/boot.bin media
[anno@localhost 4-10]$ sync
[anno@localhost 4-10]$ sudo cp kernel/kernel.bin media
[anno@localhost 4-10]$ sync

[anno@localhost 4-10]$ bochs -f ./bochsrc

程序4-10 运行结果

程序4-10 源码阅读

程序 4-10 interrupt.c

void init_interrupt()
{
    int i;
    for(i = 32;i < 56;i++)
    {
        set_intr_gate(i , 2 , interrupt[i - 32]);
    }

    color_printk(RED,BLACK,"8259A init \n");

    //8259A-master  ICW1-4
    io_out8(0x20,0x11);
    io_out8(0x21,0x20);
    io_out8(0x21,0x04);
    io_out8(0x21,0x01);

    //8259A-slave   ICW1-4
    io_out8(0xa0,0x11);
    io_out8(0xa1,0x28);
    io_out8(0xa1,0x02);
    io_out8(0xa1,0x01);

    //8259A-M/S OCW1
    io_out8(0x21,0xfd);
    io_out8(0xa1,0xff);

    sti();
}

• 屏蔽代码清单4-86中的所有中断请求，只开启键盘中断请求

主8259A芯片的OCW1寄存器映射到I/O端口21H地址处
OCW1 0xfd 即 1 1 1 1 - 1 1 0 1 B 只允许IRQ1中断
IRQ1中断就是键盘中断
（参考 表4-12 OCW1寄存器位功能说明 以及 表4-6 8259A的中断引脚与外部设备对照表）

程序 4-10 lib.h

inline unsigned char io_in8(unsigned short port)
{
    unsigned char ret = 0;
    __asm__ __volatile__(   "inb    %%dx,   %0  \n\t"
                "mfence         \n\t"
                :"=a"(ret)
                :"d"(port)
                :"memory");
    return ret;
}

• 输出部分 : "=a"(ret) 输出结果到返回值 ret
• 输入部分："d"(port) 即 DX = port

代码清单4-88　interrupt.c

void do_IRQ(unsigned long regs,unsigned long nr)    //regs:rsp,nr
{
    unsigned char x;
    color_printk(RED,BLACK,"do_IRQ:%#08x\t",nr);
    x = io_in8(0x60);
    color_printk(RED,BLACK,"key code:%#08x\n",x);
    io_out8(0x20,0x20);
}

• x = io_in8(0x60); : 借助汇编指令IN从I/O端口地址60h处读取出键盘扫描码

参考资料

• 对比 程序4-9 与程序4-10的void init_interrupt()

[OS64][023]源码阅读：程序4-9 中断处理 : 显示黑底红字的中断向量号
https://www.jianshu.com/p/332edb3149ef