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