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4-9

程序4-9 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 4-9]$ ls
bochsrc  boot.img  bootloader  kernel  media

[anno@localhost 4-9]$ sudo mount boot.img media -t vfat -o loop
[anno@localhost 4-9]$ sudo cp bootloader/loader.bin media
[anno@localhost 4-9]$ sync
[anno@localhost 4-9]$ sudo cp bootloader/boot.bin media
[anno@localhost 4-9]$ sync
[anno@localhost 4-9]$ sudo cp kernel/kernel.bin media
[anno@localhost 4-9]$ sync

[anno@localhost 4-9]$ bochs -f ./bochsrc

程序4-9 运行结果

程序4-9 源码阅读

代码清单 4-84 interrupt.c

#define IRQ_NAME2(nr) nr##_interrupt(void)
#define IRQ_NAME(nr) IRQ_NAME2(IRQ##nr)

#define Build_IRQ(nr)                           \
void IRQ_NAME(nr);                      \
__asm__ (   SYMBOL_NAME_STR(IRQ)#nr"_interrupt:     \n\t"   \
            "pushq  $0x00               \n\t"   \
            SAVE_ALL                    \
            "movq   %rsp,   %rdi            \n\t"   \
            "leaq   ret_from_intr(%rip),    %rax    \n\t"   \
            "pushq  %rax                \n\t"   \
            "movq   $"#nr", %rsi            \n\t"   \
            "jmp    do_IRQ  \n\t");

• 以 nr = 0x20举例：
  IRQ_NAME(0x20) => void IRQ0x20_interrupt(void); 之后是asm部分代码
  SYMBOL_NAME_STR(IRQ)#nr"_interrupt: => IRQ0x20_interrupt:
"movq $"#nr", %rsi => movq $0x20, %rsi

代码清单4-87　interrupt.c

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

• 目前的中断处理函数就是 在屏幕上显示黑底红字的中断向量号，0x20号中断是时钟中断
• io_out8(0x20,0x20); : 向主8259A中断控制器发送EOI命令复位ISR寄存器

代码清单4-85　interrupt.c

Build_IRQ(0x20)
Build_IRQ(0x21)
Build_IRQ(0x22)
Build_IRQ(0x23)
. . .


void (* interrupt[24])(void)=
{
    IRQ0x20_interrupt,
    IRQ0x21_interrupt,
    IRQ0x22_interrupt,
    IRQ0x23_interrupt,
    . . .
};

• 函数指针的数组，输入值是void且返回值也是void的一类函数

lib.h

inline void io_out8(unsigned short port,unsigned char value)
{
    __asm__ __volatile__(   "outb   %0, %%dx    \n\t"
                "mfence         \n\t"
                :
                :"a"(value),"d"(port)
                :"memory");
}

• 占位符 %0 等价于 EAX = value
• outb %0, %%dx 在这里等价于 outb %ax, %dx， 向端口dx写入值ax

代码清单4-86 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(0x21,0x00);
    io_out8(0xa1,0x00);

    sti();
}

• 外部硬件设备的中断向量号从32开始 : for(i = 32;i < 56;i++)
• io_out8(0x20,0x11); 向端口0x20写入数值0x11

参考资料

• 函数指针

[C指针]函数指针举例：C语言 完整源码
https://www.jianshu.com/p/992cbb3a55ce

• ATT 内联汇编 格式

[内联汇编]扩展asm：格式、占位符、跳转、内联汇编宏函数
https://www.jianshu.com/p/76fda24ee7f7

• _set_gate 格式化IDT描述符并填入IDT表

[OS64位][019]源码阅读：程序4-5 i=1/0 除法错误
https://www.jianshu.com/p/e14045176526

• MFENCE — Memory Fence

https://www.felixcloutier.com/x86/mfence
Does it make any sense to use the LFENCE instruction on x86/x86_64 processors?