基于mykernel 2.0编写一个操作系统内核

wget https://raw.github.com/mengning/mykernel/master/mykernel-2.0_for_linux-5.4.34.patch（这一步从群里下载直接复制过来即可）
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 # Default configuration is based on ‘x86_64_defconfig‘
make -j$(nproc)
sudo apt install qemu # install QEMU
qemu-system-x86_64 -kernel arch/x86/boot/bzImage

/*定义最大进程数*/
#define MAX_TASK_NUM        4
/*定义了堆栈空间大小 */
#define KERNEL_STACK_SIZE   1024*2
/* CPU-specific state of this task 
定义了一个结构体用来保存当前ip和sp */
struct Thread {
    unsigned long        ip;
    unsigned long        sp;
};

typedef struct PCB{
    int pid; /* 进程号*/
    volatile long state;    /* 进程状态 -1 unrunnable, 0 runnable, >0 stopped */
    unsigned long stack[KERNEL_STACK_SIZE]; /* 内存堆栈大小 */
    /* CPU-specific state of this task */
    struct Thread thread; /* 上述结构体 */
    unsigned long    task_entry; /* 程序入口 */
    struct PCB *next; /* 链表，将进程控制块串联起来 */
}tPCB;

void my_schedule(void); /* 声明进程调度函数 */

#include "mypcb.h"


tPCB task[MAX_TASK_NUM]; //进程队列
tPCB * my_current_task = NULL; //当前进程
volatile int my_need_sched = 0;//进程调度标志


void my_process(void);


void __init my_start_kernel(void)
{
    int pid = 0;
    int i;
    /* 初始化0号进程 */
    task[pid].pid = pid;
    task[pid].state = 0;/* 0号进程运行 */
    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];
    /*创建更多进程*/
    for(i=1;i<MAX_TASK_NUM;i++)
    {
        memcpy(&task[i],&task[0],sizeof(tPCB));
        task[i].pid = i;
        task[i].state = 0;
        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"  /* 将当前进程的栈顶指针sp值赋值给rsp寄存器中*/
        "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*/
    );
}

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);
        }
    }
}

#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.
*/
/* void my_timer_handler(void)
{
pr_notice("\n>>>>>>>>>>>>>>>>>my_timer_handler here<<<<<<<<<<<<<<<<<<\n\n");
}
*/

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;
}