linux中断机制

no_error_code://无中断码中断
//现场保存
	xchgl %eax,(%esp)
	pushl %ebx
	pushl %ecx
	pushl %edx
	pushl %edi
	pushl %esi
	pushl %ebp
	push %ds
	push %es
	push %fs
	pushl $0		# "error code"
	lea 44(%esp),%edx
	pushl %edx
	movl $0x10,%edx
	mov %dx,%ds
	mov %dx,%es
	mov %dx,%fs
//中断处理程序入口
	call *%eax     //中断处理程序入口
//现场恢复
	addl $8,%esp
	pop %fs
	pop %es
	pop %ds
	popl %ebp
	popl %esi
	popl %edi
	popl %edx
	popl %ecx
	popl %ebx
	popl %eax
	iret		//返回值操作

这个是无错误码的与有错误码差不多。中断程序在trap.c里面

2.3.trap.c

2.3.1.trap_init函数

//中断的初始化函数
//set_trap_gate 优先级较低 只能由用户程序来调用
//set_system_gate 优先级很高 能由系统和用户所有的程序调用
void trap_init(void)
{
	int i;

	set_trap_gate(0,&divide_error);//如果被除数是0就会产生这个中断
	set_trap_gate(1,&debug);//单步调试的时候调用这个中断
	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);
	outb_p(inb_p(0x21)&0xfb,0x21);
	outb(inb_p(0xA1)&0xdf,0xA1);
	set_trap_gate(39,&parallel_interrupt);
}

2.3.2.die函数

//esp_ptr 段指针
//nr 出错的段号
//总的来说die函数就是用来打印错误信息
static void die(char * str,long esp_ptr,long nr)
{
	long * esp = (long *) esp_ptr;
	int i;
	//以下基本在打印栈信息
	printk("%s: %04x\n\r",str,nr&0xffff);
	printk("EIP:\t%04x:%p\nEFLAGS:\t%p\nESP:\t%04x:%p\n",
		esp[1],esp[0],esp[2],esp[4],esp[3]);
	printk("fs: %04x\n",_fs());
	printk("base: %p, limit: %p\n",get_base(current->ldt[1]),get_limit(0x17));
	if (esp[4] == 0x17) {
		printk("Stack: ");
		for (i=0;i<4;i++)
			printk("%p ",get_seg_long(0x17,i+(long *)esp[3]));
		printk("\n");
	}
	str(i);
	printk("Pid: %d, process nr: %d\n\r",current->pid,0xffff & i);
	for(i=0;i<10;i++)
		printk("%02x ",0xff & get_seg_byte(esp[1],(i+(char *)esp[0])));
	printk("\n\r");
	do_exit(11);//退出中断		/* play segment exception */
}

2.4 .sys_call.s

里面主要是一些中断汇编代码本质都是现场保存中断程序执行现场恢复的过程。

2.4.1._system_call.s

该函数主要关注的是设置eax寄存器然后通过call _sys_call_table(,%eax,4)获取中断服务函数sys_call_table是一个数组typedef int (*fn_ptr)()类型的函数指针【返回值是int 参数无所谓】

_system_call:
	cmpl $nr_system_calls-1,%eax
	ja bad_sys_call
	push %ds
	push %es
	push %fs
	pushl %edx
	pushl %ecx		# push %ebx,%ecx,%edx as parameters
	pushl %ebx		# to the system call
	movl $0x10,%edx		# set up ds,es to kernel space
	mov %dx,%ds
	mov %dx,%es
	movl $0x17,%edx		# fs points to local data space
	mov %dx,%fs
	call _sys_call_table(,%eax,4)
	pushl %eax
	movl _current,%eax
	cmpl $0,state(%eax)		# state
	jne reschedule
	cmpl $0,counter(%eax)		# counter
	je reschedule

//定义系统调用的sys_call_table
fn_ptr sys_call_table[] = { sys_setup, sys_exit, sys_fork, sys_read,
sys_write, sys_open, sys_close, sys_waitpid, sys_creat, sys_link,
sys_unlink, sys_execve, sys_chdir, sys_time, sys_mknod, sys_chmod,
sys_chown, sys_break, sys_stat, sys_lseek, sys_getpid, sys_mount,
sys_umount, sys_setuid, sys_getuid, sys_stime, sys_ptrace, sys_alarm,
sys_fstat, sys_pause, sys_utime, sys_stty, sys_gtty, sys_access,
sys_nice, sys_ftime, sys_sync, sys_kill, sys_rename, sys_mkdir,
sys_rmdir, sys_dup, sys_pipe, sys_times, sys_prof, sys_brk, sys_setgid,
sys_getgid, sys_signal, sys_geteuid, sys_getegid, sys_acct, sys_phys,
sys_lock, sys_ioctl, sys_fcntl, sys_mpx, sys_setpgid, sys_ulimit,
sys_uname, sys_umask, sys_chroot, sys_ustat, sys_dup2, sys_getppid,
sys_getpgrp, sys_setsid, sys_sigaction, sys_sgetmask, sys_ssetmask,
sys_setreuid,sys_setregid };

至于sys_call_table的函数实现可以自己去查看一下。