基于mykernel 2.0编写一个操作系统内核

/* 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);

#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) //时间片处理函数
{
    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;
}