os_kernel/kernel/interrupt.c

#include "interrupt.h"
#include "stdint.h"
#include "global.h"
#include "../lib/kernel/print.h"
#include "../lib/kernel/io.h"

char *intr_name[IDT_DESC_CNT];        // 用于保存异常的名字
intr_handler idt_table[IDT_DESC_CNT]; // 中断处理函数数组

#define EFLAGS_IF 0x200 // eflags寄存器中的if位为1
#define GET_EFLAGS(EFLAG_VAR) asm volatile("pushfl; popl %0" : "=g"(EFLAG_VAR))

static gate_desc idt[IDT_DESC_CNT]; // 中断描述符表,本质上就是个中断门描述符数组

/*创建中断门描述符*/
static void make_idt_desc(gate_desc *p_gdesc, uint8_t attr, intr_handler function)
{
    p_gdesc->offset_low = (uint32_t)function & 0x0000FFFF;
    p_gdesc->selector = SELECTOR_K_CODE;
    p_gdesc->dcount = 0;
    p_gdesc->attribute = attr;
    p_gdesc->offset_high = ((uint32_t)function & 0xFFFF0000) >> 16;
}
/* 初始化中断描述符表*/
static void itd_desc_init(void)
{
    int i;
    for (i = 0; i < IDT_DESC_CNT; i++)
    {
        make_idt_desc(&idt[i], IDT_DESC_ATTR_DPL0, intr_entry_table[i]);
    }
    put_str("   idt_desc_init done\n");
}

/* 初始化可编程中断控制器 8259A */
static void pic_init(void)
{
    /* 初始化主片*/
    outb(PIC_M_CTRL, 0x11); // ICW1: 边沿触发，级联8259， 需要 ICW4
    outb(PIC_M_DATA, 0x20); // ICW2: 起始中断向量号 0x20, 也就是 IRQ[0～7] 为 0x20~0x27
    outb(PIC_M_DATA, 0x04); // ICW3: IR2 接从片
    outb(PIC_M_DATA, 0x01); // ICW4: 8086 模式， 正常 EOI

    /* 初始化从片 */
    outb(PIC_S_CTRL, 0x11); // ICW1: 边沿触发，级联8259， 需要 ICW4
    outb(PIC_S_DATA, 0x28); // ICW2: 起始中断向量号 0x28, 也就是 IRQ[8～15] 以 0x28~0x2F
    outb(PIC_S_DATA, 0x02); // ICW3: 设置从片连接到主片的 IR2 引脚
    outb(PIC_S_DATA, 0x01); // ICW4: 8086 模式， 正常 EOI

    /* 打开主片上 IR0， 也就是目前只接受时钟产生的中断*/
    outb(PIC_M_DATA, 0xfe);
    outb(PIC_S_DATA, 0xff);

    put_str("   pic_init done\n");
}

static void general_intr_handler(uint8_t vec_nr)
{
    if (vec_nr == 0x27 || vec_nr == 0x2f)
    {
        // IRQ7 和 IRQ15 会产生伪中断，无需处理
        // 0x2f 是从片8259A上的最后一个 IRQ 引脚，保留项
        return;
    }
    put_str("int vector: 0x");
    put_int(vec_nr);
    put_char('\n');
}

static void exception_init(void)
{
    int i;
    for (i = 0; i < IDT_DESC_CNT; i++)
    {
        /*idt_table 数组中的函数是进入中断后根据中断向量号调用的，见 kernel/kernel.S 的 call [itd_table + %1*4]*/
        idt_table[i] = general_intr_handler; // 默认为 general_intr_handler
        intr_name[i] = "unknown";
    }
    intr_name[0] = "#DE Divide Error";
    intr_name[1] = "#DB Debug Exception";
    intr_name[2] = "NMI Interrupt";
    intr_name[3] = "#BP Breakpoint Exception";
    intr_name[4] = "#OF Overflow Exception";
    intr_name[5] = "#BR BOUND Range Exceeded Exception";
    intr_name[6] = "#UD Invalid Opcode Exception";
    intr_name[7] = "#NM Device Not Available Exception";
    intr_name[8] = "#DF Double Fault Exception";
    intr_name[9] = "Coprocessor Segment Overrun";
    intr_name[10] = "#TS Invalid TSS Exception";
    intr_name[11] = "#NP Segment Not Present";
    intr_name[12] = "#SS Stack Fault Exception";
    intr_name[13] = "#GP General Protection Exception";
    intr_name[14] = "#PF Page-Fault Exception";
    // intr_name[15] 第 15 项是 intel 保留项，未使用
    intr_name[16] = "#MF x87 FPU Floating-Point Error";
    intr_name[17] = "#AC Alignment Check Exception";
    intr_name[18] = "#MC Machine-Check Exception";
    intr_name[19] = "#XF SIMD Floating-Point Exception";
    put_str("   exception_init done\n");
}

/* 中断初始化主函数 */
void itd_init(void)
{
    put_str("init_idt start\n");
    itd_desc_init();  // 初始化中断描述符表
    exception_init(); // 完成一般中断处理函数注册及异常名称注册
    pic_init();       // 初始化可编程中断控制器8259A

    /* 加载 idt */
    uint64_t idt_operand = ((sizeof(idt) - 1) | ((uint64_t)((uint32_t)idt << 16)));
    asm volatile("lidt %0" ::"m"(idt_operand));
    put_str("itd_init done\n");
}

enum intr_status intr_get_status(void)
{
    uint32_t eflags = 0;
    GET_EFLAGS(eflags);
    return (EFLAGS_IF & eflags) ? INTR_ON : INTR_OFF;
}
enum intr_status intr_set_status(enum intr_status status)
{
    return status & INTR_ON ? intr_enable() : intr_disable();
}
enum intr_status intr_enable(void)
{
    enum intr_status old_status;
    if (INTR_ON == intr_get_status())
    {
        old_status = INTR_ON;
        return old_status;
    }
    else
    {
        old_status = INTR_OFF;
        asm volatile("sti"); // 开中断, sti 指令将IF位置1
        return old_status;
    }
}
enum intr_status intr_disable(void)
{
    enum intr_status old_status;
    if (INTR_ON == intr_get_status())
    {
        old_status = INTR_ON;
        asm volatile("cli" : : : "memory"); // 关中断, cli 指令将IF位置0
        return old_status;
    }
    else
    {
        old_status = INTR_OFF;
        return old_status;
    }
}