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2019-2020-1 20199315《Linux内核原理与分析》第三周作业

作者:互联网

《庖丁解牛Linux内核分析》第二章


asm volatile(                       /*__asm__是GCC关键字asm的宏定义,是内嵌汇编的关键字,表示这是一条内嵌汇编语句。__volatile__的宏定义,告诉编译器不要优化代码,汇编指令保留原样。*/
"movl $0,%%eax\n\t"          /* clear %eax to 0。将EAX清0 */
"addl %1,%%eax\n\t"          /* %eax+=val1。%1指下面的输出和输入的部分,此处是指val1,该句意为把val1的值放到ECX里面,然后把ECX的值与EAX寄存器求和放入EAX寄存器中。 */
"addl %2,%%eax\n\t"          /* %eax+=val2。该句意为把val2的值放到ECX里面,然后把ECX的值与EAX寄存器(val1的值)求和放入EAX寄存器中。*/
"movl %%eax,%0\n\t"         /* val2=%eax。把val1加上val2的值存储的地方放到%0,即val3。 */
: "=m" (val3)                        /* =m意思是写到内存变量里面去 */
: "c" (val1),"d" (val2)            /* c指用ECX寄存器存储val1的值 */
);

实验楼实验二

下载linux-3.9.4.tar.xz,并搭建虚拟的x86CPU实验平台。


$ sudo apt-get install qemu # install QEMU
$ sudo ln -s /usr/bin/qemu-system-i386 /usr/bin/qemu
$ wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.9.4.tar.xz # download Linux Kernel 3.9.4 source code
$ wget https://raw.github.com/mengning/mykernel/master/mykernel_for_linux3.9.4sc.patch # download mykernel_for_linux3.9.4sc.patch
$ xz -d linux-3.9.4.tar.xz
$ tar -xvf linux-3.9.4.tar
# 注意路径是区分大小的
$ cd ~/LinuxKernel/linux-3.9.4
$ rm -rf mykernel
$ patch -p1 < ../mykernel_for_linux3.9.4sc.patch
$ make allnoconfig
# 编译内核请耐心等待
$ make
$ qemu -kernel arch/x86/boot/bzImage

在Linux-3.9.4内核源代码根目录下cd进入mykernel目录,可以看到QEMU窗口输出的内容的代码mymain.c和myinterrupt.c。

myinterrupt.c和mymain.c代码分别如下。

mykernel/mypcb.h:

   
/*
 *  linux/mykernel/mypcb.h
 *
 *  Kernel internal PCB types
 *
 *  Copyright (C) 2013  Mengning
 *
 */

#define MAX_TASK_NUM        4
#define KERNEL_STACK_SIZE   1024*2 # unsigned long
/* 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 */
    unsigned long 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);

mykernel/mymain.c


/*
 *  linux/mykernel/mymain.c
 *
 *  Kernel internal my_start_kernel
 *
 *  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"

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].stack[KERNEL_STACK_SIZE-1] - 1) = (unsigned long)&task[i].stack[KERNEL_STACK_SIZE-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 */
        : 
        : "c" (task[pid].thread.ip),"d" (task[pid].thread.sp)   /* input c or d mean %ecx/%edx*/
    );
} 

int i = 0;

void my_process(void)
{    
    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);
        }     
    }
}

mykernel/myinterrupt.c


/*
 *  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 */
    {        
        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)
        ); 
    }  
    return; 
}

标签:task,20199315,寄存器,pid,2020,mykernel,2019,include,my
来源: https://www.cnblogs.com/qianxiaoxu/p/11597458.html