基于mykernel 2.0编写一个操作系统内核

时间:2020-05-12
本文章向大家介绍基于mykernel 2.0编写一个操作系统内核 ,主要包括基于mykernel 2.0编写一个操作系统内核 使用实例、应用技巧、基本知识点总结和需要注意事项,具有一定的参考价值,需要的朋友可以参考一下。

配置mykernel 2.0

配置命令

wget https://raw.github.com/mengning/mykernel/master/mykernel-2.0_for_linux-5.4.34.patch
sudo apt install axel
axel -n 20 https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/linux-5.4.34.tar.xz
xz -d linux-5.4.34.tar.xz 
tar -xvf linux-5.4.34.tar
cd linux-5.4.34
patch -p1 < ../mykernel-2.0_for_linux-5.4.34.patch
sudo apt install build-essential libncurses-dev bison flex libssl-dev libelf-dev
make defconfig 10 make -j$(nproc) 
sudo apt install qemu 12 qemu-system-x86_64 -kernel arch/x86/boot/bzImage

结果如下

输入以下命令

sudo apt install qemu # install QEMU
qemu-system-x86_64 -kernel arch/x86/boot/bzImage

结果如下

基于mykernel 2.0编写操作系统内核

首先在mykernel目录下增加一个mypcb.h 头文件,用来定义进程控制块(Process Control Block),也就是进程结构体的定义。

#define MAX_TASK_NUM        4
#define KERNEL_STACK_SIZE   1024*2

/* 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);

对mymain.c中的my_start_kernel函数进行修改,并在mymain.c中实现了my_process函数,用来作为进程的代码模拟一个个进程,时间片轮转调度

#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].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(
        "movq %1,%%rsp\n\t"     /* set task[pid].thread.sp to rsp */
        "pushq %1\n\t"             /* push rbp */
        "pushq %0\n\t"             /* push task[pid].thread.ip */
        "ret\n\t"                 /* pop task[pid].thread.ip to rip */
        : 
        : "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);
        }     
    }
}

对myinterrupt.c的修改,my_timer_handler用来记录时间片,时间片消耗完之后完成调度。并在该文件中完成,my_schedule(void)函数的实现

#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(time_count%1000 == 0 && my_need_sched != 1)
    {
        printk(KERN_NOTICE ">>>my_timer_handler here<<<\n");
        my_need_sched = 1;
    }
    time_count ++ ; 
    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( 
         "pushq %%rbp\n\t"      /* save rbp of prev */
         "movq %%rsp,%0\n\t"  /* save rsp of prev */
         "movq %2,%%rsp\n\t"     /* restore  rsp of next */
         "movq $1f,%1\n\t"       /* save rip of prev */ 
         "pushq %3\n\t"
         "ret\n\t"              /* restore  rip of next */
         "1:\t"                  /* next process start here */
         "popq %%rbp\n\t"
         : "=m" (prev->thread.sp),"=m" (prev->thread.ip)
         : "m" (next->thread.sp),"m" (next->thread.ip)
     );
    } 
    return; 
}

重新编译,结果如下

简要分析操作系统内核核心功能及运行工作机制

系统启动后,首先运行mymain.c中的my_start_kernel函数,里面是一个while(1) 循环,永远执行下去。然后是myinterrupt.c,里面的my_timer_handler 函数会被内核周期性的调用,每调用1000次,就去将全局变量my_need_sched的值修改为1,my_start_kernel中的while循环发现my_need_sched值变为1后,就进行进程的调度,完成进程的切换,如此往复。

原文地址:https://www.cnblogs.com/lizhen511/p/12875774.html