Linux内核分析第二周学习笔记

linux内核分析第二周学习笔记

标签（空格分隔）： 20135328陈都

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陈都 原创作品转载请注明出处 《Linux内核分析》MOOC课程http://mooc.study.163.com/course/USTC-1000029000

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1.函数调用堆栈

1.1小结

三把宝剑：

• 存储程序计算机
• 函数调用堆栈
• 中断机制

1.2堆栈

堆栈是C语言程序运行时必须的一个记录调用路径和参数的空间

• 函数条用框架
• 传递参数
• 保存返回地址
• 提供局部变量空间

C代码中嵌入汇编代码的写法

0. 内嵌汇编语法

asm(汇编语句模板: 输出部分: 输入部分: 破坏描述部分)

• 各部分使用“:”格开

1. 汇编语句模板

2. 输出部分

3. 输入部分

4. 破坏描述部分

5. 限制字符

实验：一个简单的操作系统内核源代码

GitHub 多进程时间片轮转代码

 *  linux/mykernel/myinterrupt.c
 *
 *  Kernel internal my_timer_handler
 *
 *  Copyright (C) 2013  Mengning
 *
 */
#include <linux/types.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/tty.h>
#include <linux/vmalloc.h>

#include "mypcb.h"

extern tPCB task[MAX_TASK_NUM];
extern tPCB * my_current_task;
extern volatile int my_need_sched;
volatile int time_count = 0;

/*
 * Called by timer interrupt.
 * it runs in the name of current running process,
 * so it use kernel stack of current running process
 */
void my_timer_handler(void)
{
#if 1
    if(time_count%1000 == 0 && my_need_sched != 1)
    {
        printk(KERN_NOTICE ">>>my_timer_handler here<<<
");
        my_need_sched = 1;
    } 
    time_count ++ ;  
#endif
    return;  	
}

void my_schedule(void)
{
    tPCB * next;
    tPCB * prev;

    if(my_current_task == NULL 
        || my_current_task->next == NULL)
    {
    	return;
    }
    printk(KERN_NOTICE ">>>my_schedule<<<
");
    /* schedule */
    next = my_current_task->next;
    prev = my_current_task;
    if(next->state == 0)/* -1 unrunnable, 0 runnable, >0 stopped */
    {
    	/* switch to next process */
    	asm volatile(	
        	"pushl %%ebp
	" 	    /* save ebp */
        	"movl %%esp,%0
	" 	/* save esp */
        	"movl %2,%%esp
	"     /* restore  esp */
        	"movl $1f,%1
	"       /* save eip */	
        	"pushl %3
	" 
        	"ret
	" 	            /* restore  eip */
        	"1:	"                  /* next process start here */
        	"popl %%ebp
	"
        	: "=m" (prev->thread.sp),"=m" (prev->thread.ip)
        	: "m" (next->thread.sp),"m" (next->thread.ip)
    	); 
    	my_current_task = next; 
    	printk(KERN_NOTICE ">>>switch %d to %d<<<
",prev->pid,next->pid);   	
    }
    else
    {
        next->state = 0;
        my_current_task = next;
        printk(KERN_NOTICE ">>>switch %d to %d<<<
",prev->pid,next->pid);
    	/* switch to new process */
    	asm volatile(	
        	"pushl %%ebp
	" 	    /* save ebp */
        	"movl %%esp,%0
	" 	/* save esp */
        	"movl %2,%%esp
	"     /* restore  esp */
        	"movl %2,%%ebp
	"     /* restore  ebp */
        	"movl $1f,%1
	"       /* save eip */	
        	"pushl %3
	" 
        	"ret
	" 	            /* restore  eip */
        	: "=m" (prev->thread.sp),"=m" (prev->thread.ip)
        	: "m" (next->thread.sp),"m" (next->thread.ip)
    	);          
    }   
    return;	
}