2019-2020-1 20212809《Linux内核原理与分析》第二周作业

1.计算机的三个法宝：存储程序计算机、函数调用堆栈机制、中断。
2.什么是堆栈？堆栈是c语言程序运行时必须使用的记录函数调用路径和参数存储的空间。其具体作用有：记录函数调用框架、传递函数参数、保存返回值的地址、提供函数内部局部变量的存储空间等。
3.中断机制：当一个中断信号发生时，CPU将当前所执行程序的EIP和ESP压入内核堆栈，然后使EIP指向中断处理程序入口，保存现场之后执行其他程序，执行完再恢复现场，恢复EIP和ESP，继续执行中断前的程序。
内嵌汇编常用限定符：

$ cd ~/LinuxKernel/linux-3.9.4
$ rm -rf mykernel
$ patch -p1 < ../mykernel_for_linux3.9.4sc.patch
$ make allnoconfig

$ make

运行上述代码块后：

$ qemu -kernel arch/x86/boot/bzImage

然后 cd mykernel ，可以看到 qemu 窗口输出的内容的代码 mymain.c 和 myinterrupt.c
查看 mymain.c 和 myinterrupt.c的内容

#define MAX_TASK_NUM        4
#define KERNEL_STACK_SIZE   1024*2

struct Thread {
    unsigned long		ip;
    unsigned long		sp;
};

typedef struct PCB{
    int pid;
    volatile long state;	
    unsigned long stack[KERNEL_STACK_SIZE];
    
    struct Thread thread;
    unsigned long	task_entry;
    struct PCB *next;
}tPCB;

void my_schedule(void);

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

#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)                  
    { 
        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)
        ); 
        my_current_task = next; 
        printk(KERN_NOTICE ">>>switch %d to %d<<pid,next->pid);      
    }
    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; 
}

make：