1. 内部中断(0~31号、0x80作为中断号)

只要初始化:

    1) 相关的中断向量表

2. 外部中断(0~255中的除了0~31号、0x80的其他中断号)

需要初始化:

    1) 相关的中断向量表

    2) 以及中断控制器(控制器负责优先级排队、屏蔽等工作)

void __init trap_init(void)

{

    int i;

#ifdef CONFIG_EISA

    void __iomem *p = early_ioremap(0x0FFFD9, 4);

    if (readl(p) == 'E' + ('I'<<8) + ('S'<<16) + ('A'<<24))

        EISA_bus = 1;

    early_iounmap(p, 4);

#endif

/*

trap_init()主要是调用set_xxx_gate(中断向量, 中断处理函数)

set_xxx_gate()就是按照中断门的格式填写中断向量表的

Intel x86支持4种"门描述符":

1) 调用门(call gate)

2) 陷阱门(trap gate)

3) 中断门(iinterrupt gate)

4) 任务门(task gate)

*/

    set_intr_gate(X86_TRAP_DE, divide_error);

    set_intr_gate_ist(X86_TRAP_NMI, &nmi, NMI_STACK);

    /* int4 can be called from all */

    set_system_intr_gate(X86_TRAP_OF, &overflow);

    set_intr_gate(X86_TRAP_BR, bounds);

    set_intr_gate(X86_TRAP_UD, invalid_op);

    set_intr_gate(X86_TRAP_NM, device_not_available);

#ifdef CONFIG_X86_32

    set_task_gate(X86_TRAP_DF, GDT_ENTRY_DOUBLEFAULT_TSS);

#else

    set_intr_gate_ist(X86_TRAP_DF, &double_fault, DOUBLEFAULT_STACK);

#endif

    set_intr_gate(X86_TRAP_OLD_MF, coprocessor_segment_overrun);

    set_intr_gate(X86_TRAP_TS, invalid_TSS);

    set_intr_gate(X86_TRAP_NP, segment_not_present);

    set_intr_gate_ist(X86_TRAP_SS, &stack_segment, STACKFAULT_STACK);

    set_intr_gate(X86_TRAP_GP, general_protection);

    set_intr_gate(X86_TRAP_SPURIOUS, spurious_interrupt_bug);

    set_intr_gate(X86_TRAP_MF, coprocessor_error);

    set_intr_gate(X86_TRAP_AC, alignment_check);

#ifdef CONFIG_X86_MCE

    set_intr_gate_ist(X86_TRAP_MC, &machine_check, MCE_STACK);

#endif

    set_intr_gate(X86_TRAP_XF, simd_coprocessor_error);

    /* Reserve all the builtin and the syscall vector: */

    for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++)

        set_bit(i, used_vectors);

#ifdef CONFIG_IA32_EMULATION

    set_system_intr_gate(IA32_SYSCALL_VECTOR, ia32_syscall);

    set_bit(IA32_SYSCALL_VECTOR, used_vectors);

#endif

//设置系统调用中断

#ifdef CONFIG_X86_32

    set_system_trap_gate(SYSCALL_VECTOR, &system_call);

    set_bit(SYSCALL_VECTOR, used_vectors);

#endif

    /*

     * Set the IDT descriptor to a fixed read-only location, so that the

     * "sidt" instruction will not leak the location of the kernel, and

     * to defend the IDT against arbitrary memory write vulnerabilities.

     * It will be reloaded in cpu_init() */

    __set_fixmap(FIX_RO_IDT, __pa_symbol(idt_table), PAGE_KERNEL_RO);

    idt_descr.address = fix_to_virt(FIX_RO_IDT);

    /*

     * Should be a barrier for any external CPU state:

     */

    cpu_init();

    x86_init.irqs.trap_init();

#ifdef CONFIG_X86_64

    memcpy(&debug_idt_table, &idt_table, IDT_ENTRIES * 16);

    set_nmi_gate(X86_TRAP_DB, &debug);

    set_nmi_gate(X86_TRAP_BP, &int3);

#endif

}

1. 对除了0~31、0x80中断号之外的其它中断向量

2. 中断控制器的初始化(相比内部中断初始化多了这一步)
这两步操作都在在init_IRQ()中完成

void __init init_IRQ(void)

{

    int i;

    /*

     * We probably need a better place for this, but it works for

     * now ...

     */

    x86_add_irq_domains();

    /*

     * On cpu 0, Assign IRQ0_VECTOR..IRQ15_VECTOR's to IRQ 0..15.

     * If these IRQ's are handled by legacy interrupt-controllers like PIC,

     * then this configuration will likely be static after the boot. If

     * these IRQ's are handled by more mordern controllers like IO-APIC,

     * then this vector space can be freed and re-used dynamically as the

     * irq's migrate etc.

     */

    for (i = 0; i < legacy_pic->nr_legacy_irqs; i++) //对于单CPU结构，

        per_cpu(vector_irq, 0)[IRQ0_VECTOR + i] = i;

    //x86_init.irqs.intr_init()等价于调用：native_init_IRQ()

    x86_init.irqs.intr_init();

}

void __init native_init_IRQ(void)

{

    int i;

    /* Execute any quirks before the call gates are initialised: */

    x86_init.irqs.pre_vector_init(); //调用 init_ISA_irqs 

    apic_intr_init();  

    /*

     * Cover the whole vector space, no vector can escape

     * us. (some of these will be overridden and become

     * 'special' SMP interrupts)

     */

     /*

     interrupt数组，它保存的是每个中断服务程序的入口地址，它的定义是在\linux-3.15.5\arch\x86\kernel\entry_32.S中

     */

    for (i = FIRST_EXTERNAL_VECTOR; i < NR_VECTORS; i++)

    {

    //设置32~255号中断

        /* IA32_SYSCALL_VECTOR could be used in trap_init already. */

        if (!test_bit(i, used_vectors))

    {

        //要除去0x80中断

        set_intr_gate(i, interrupt[i-FIRST_EXTERNAL_VECTOR]);

    }

    }

    if (!acpi_ioapic && !of_ioapic)

        setup_irq(2, &irq2);

#ifdef CONFIG_X86_32

    /*

     * External FPU? Set up irq13 if so, for

     * original braindamaged IBM FERR coupling.

     */

    if (boot_cpu_data.hard_math && !cpu_has_fpu)

        setup_irq(FPU_IRQ, &fpu_irq);

    irq_ctx_init(smp_processor_id());

#endif

}