2019-2020-1 20199303《Linux内核原理与分析》第三周作业

操作系统是如何工作的

除了存储程序计算机和函数调用堆栈机制，还有一个非常基础的概念就是中断，这三个关键性的方法机制可以称作计算机的三个法宝：程序存储计算机、函数调用、中断

堆栈的作用：记录函数调用框架、传递函数参数、保存返回值地址、提供函数内部局部便量的存储空间。

堆栈相关的寄存器 ESP：堆栈指针，指向堆栈栈顶 EBP：基址指针，指向堆栈栈底

堆栈操作：push pop

实验过程

依次输入

cd ~/LinuxKernel/linux-3.9.4

$ rm -rf mykernel

$ patch -p1 < ../mykernel_for_linux3.9.4sc.patch

$ make allnoconfig

$ make

$ qemu -kernel arch/x86/boot/bzImage

可以看到内核启动效果

mymain.c可以每100000次输出一次my start kernel here ，周期性地产生时钟中断信号，同时执行myinterrupt.c中的代码。

然后按实验要求修改代码如下所示

mypcb.h:

#define MAX_TASK_NUM 4

#define KERNEL_STACK_SIZE 1024*8

/* CPU-specific state of this task */

struct Thread {

unsigned long		ip;

unsigned long		sp;

};

typedef struct PCB{

int pid;

volatile long state;	/* -1 unrunnable, 0 runnable, >0 stopped */

char stack[KERNEL_STACK_SIZE];

/* CPU-specific state of this task */

struct Thread thread;

unsigned long	task_entry;

struct PCB *next;

}tPCB;

void my_schedule(void);

mymain.c:

#include <linux/types.h>

#include <linux/string.h>

#include <linux/ctype.h>

#include <linux/tty.h>

#include <linux/vmalloc.h>

#include "mypcb.h"

tPCB task[MAX_TASK_NUM];

tPCB * my_current_task = NULL;

volatile int my_need_sched = 0;

void my_process(void);

void __init my_start_kernel(void)

{

int pid = 0;

int i;

/* Initialize process 0*/

task[pid].pid = pid;

task[pid].state = 0;/* -1 unrunnable, 0 runnable, >0 stopped */

task[pid].task_entry = task[pid].thread.ip = (unsigned long)my_process;

task[pid].thread.sp = (unsigned long)&task[pid].stack[KERNEL_STACK_SIZE-1];

task[pid].next = &task[pid];

/*fork more process */

for(i=1;i<MAX_TASK_NUM;i++)

{

    memcpy(&task[i],&task[0],sizeof(tPCB));

    task[i].pid = i;

    task[i].state = -1;

    task[i].thread.sp = (unsigned long)&task[i].stack[KERNEL_STACK_SIZE-1];

    task[i].next = task[i-1].next;

    task[i-1].next = &task[i];

}

/* start process 0 by task[0] */

pid = 0;

my_current_task = &task[pid];

asm volatile(

	"movl %1,%%esp\n\t" 	/* set task[pid].thread.sp to esp */

	"pushl %1\n\t" 	        /* push ebp */

	"pushl %0\n\t" 	        /* push task[pid].thread.ip */

	"ret\n\t" 	            /* pop task[pid].thread.ip to eip */

	"popl %%ebp\n\t"

	:

	: "c" (task[pid].thread.ip),"d" (task[pid].thread.sp)	/* input c or d mean %ecx/%edx*/

);

}

void my_process(void)

{

int i = 0;

while(1)

{

    i++;

    if(i%10000000 == 0)

    {

        printk(KERN_NOTICE "this is process %d -\n",my_current_task->pid);

        if(my_need_sched == 1)

        {

            my_need_sched = 0;

    	    my_schedule();

    	}

    	printk(KERN_NOTICE "this is process %d +\n",my_current_task->pid);

    }

}

}

myinterrupt.c:

#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 */

{

	my_current_task = next;

	printk(KERN_NOTICE ">>>switch %d to %d<<<\n",prev->pid,next->pid);

	/* 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)

	); 

}

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;

}

完成后的目录为

运行的结果为

在my_process(void)函数中，每10000000次打印“this is process %d”,如果my_need_sched为1时，执行myinerrupt中的my_schedule()触发中断。

巴特西

2019-2020-1 20199303《Linux内核原理与分析》第三周作业

操作系统是如何工作的

实验过程

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