10)中断初始化

trap_init

// init/main.c
void main(void) {
    ...
    trap_init();
    ...
}

// kernel/traps.c
void trap_init(void) {
    int i;
    set_trap_gate(0,&divide_error);
    set_trap_gate(1,&debug);
    set_trap_gate(2,&nmi);
    set_system_gate(3,&int3);   /* int3-5 can be called from all */
    set_system_gate(4,&overflow);
    set_system_gate(5,&bounds);
    set_trap_gate(6,&invalid_op);
    set_trap_gate(7,&device_not_available);
    set_trap_gate(8,&double_fault);
    set_trap_gate(9,&coprocessor_segment_overrun);
    set_trap_gate(10,&invalid_TSS);
    set_trap_gate(11,&segment_not_present);
    set_trap_gate(12,&stack_segment);
    set_trap_gate(13,&general_protection);
    set_trap_gate(14,&page_fault);
    set_trap_gate(15,&reserved);
    set_trap_gate(16,&coprocessor_error);
    for (i=17;i<48;i++)
        set_trap_gate(i,&reserved);
    set_trap_gate(45,&irq13);
    set_trap_gate(39,&parallel_interrupt);
}
C

这个函数负责初始化中断，能让系统接收各种事件，比如键盘。

主要有三个部分：

// kernel/traps.c
void trap_init(void) {
    int i;
    // set 了一堆 trap_gate
    set_trap_gate(0, &divide_error);
    ... 
    // 又 set 了一堆 system_gate
    set_system_gate(45, &bounds);
    ...
    // 又又批量 set 了一堆 trap_gate
    for (i=17;i<48;i++)
        set_trap_gate(i, &reserved);
    ...
}
C

set_trap_gate 和 set_system_gate

set_trap_gate 和 set_system_gate 是宏定义：

// include/asm/system.h
#define _set_gate(gate_addr,type,dpl,addr) \
__asm__ ("movw %%dx,%%ax\n\t" \
    "movw %0,%%dx\n\t" \
    "movl %%eax,%1\n\t" \
    "movl %%edx,%2" \
    : \
    : "i" ((short) (0x8000+(dpl<<13)+(type<<8))), \
    "o" (*((char *) (gate_addr))), \
    "o" (*(4+(char *) (gate_addr))), \
    "d" ((char *) (addr)),"a" (0x00080000))

#define set_trap_gate(n,addr) \
    _set_gate(&idt[n],15,0,addr)

#define set_system_gate(n,addr) \
    _set_gate(&idt[n],15,3,addr)
C