2021-2022-1 20212822《Linux内核原理与分析》第三周作业

• 实验步骤
  • 使用实验楼的虚拟机打开 shell
  • 然后 cd mykernel 您可以看到 qemu 窗口输出的内容的代码 mymain.c 和 myinterrupt.c
  • 使用自己的 Linux 系统环境
• 实验结果截图
  • 下图用make编译了内核
  • 下图是执行默认的
  • 下图是编写好自己的内核程序后的执行结果（下附代码及分析）
• 实验代码及分析
• 以下为新增内容mypcb.h(进程控制块)

#define MAX_TASK_NUM        4
#define KERNEL_STACK_SIZE   1024*2


struct Thread {
	unsigned long       ip;		//eip
	unsigned long       sp;		//esp
};

typedef struct PCB{
	int pid;		//进程id
	volatile long state;	//-1表示不可运行，0表示可运行，>0表示停止
	unsigned long stack[KERNEL_STACK_SIZE];		//内核堆栈
	struct Thread thread;		//线程
	unsigned long   task_entry;		//入口
 	struct PCB *next;		//next指针
}tPCB;

void my_schedule(void);

• 以下为修改内容mymain.c(主函数)

#include 
#include 
#include 
#include 
#include 


#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)		//入口
{
    int pid = 0;
    int i;
    
    task[pid].pid = pid;
    task[pid].state = 0;
    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];
    
    for(i=1;ipid);
            if(my_need_sched == 1)
            {
                my_need_sched = 0;
        	    my_schedule();		//若需要调度,则执行调度函数
        	}
        	printk(KERN_NOTICE "this is process %d +n",my_current_task->pid);
        }     
    }
}

• 以下为修改内容myinterrupt.c(中断控制函数)

#include 
#include 
#include 
#include 
#include 

#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;


void my_timer_handler(void)			
{
#if 1
    if(time_count%1000 == 0 && my_need_sched != 1)
    {
        printk(KERN_NOTICE ">>>my_timer_handler here<<next == NULL)
    {
    	return;
    }
    printk(KERN_NOTICE ">>>my_schedule<<next;
    prev = my_current_task;
    if(next->state == 0)
    {
    	my_current_task = next; 
    	printk(KERN_NOTICE ">>>switch %d to %d<<pid,next->pid);  
    	
    	asm volatile(	
        	"pushl %%ebpnt" 	    
        	"movl %%esp,%0nt" 	
        	"movl %2,%%espnt"     
        	"movl $1f,%1nt"       	
        	"pushl %3nt" 			
        	"retnt" 	            
        	"1:t"                  
        	"popl %%ebpnt"		
        	: "=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<<pid,next->pid);
    	
    	asm volatile(	
        	"pushl %%ebpnt" 	    
        	"movl %%esp,%0nt" 	
        	"movl %2,%%espnt"     
        	"movl %2,%%ebpnt"     
        	"movl $1f,%1nt"       	
        	"pushl %3nt" 			
        	"retnt" 	            
        	: "=m" (prev->thread.sp),"=m" (prev->thread.ip)
        	: "m" (next->thread.sp),"m" (next->thread.ip)
    	);          
    }   
    return;	
}

• 实验中遇到的问题及解决方案
  • 实验中在mykernel目录下使用make会报错，因为只有在linux-3.9.4文件夹下的makefile文件才有使用价值，返回到上一目录后再使用make即可解决问题