VMware workstation 15+ Ubuntu 19.10
1.按照https://github.com/mengning/mykernel 的说明配置mykernel 2.0,熟悉Linux内核的编译
第一个链接通过修改hosts文件获得
2.基于mykernel 2.0编写一个操作系统内核,参照https://github.com/mengning/mykernel 提供的范例代码
(1)在linux-5.4.34下有mykernel目录,进入该目录,其中mymain.c 是内核运行的程序。当前有一个虚拟的CPU执行C代码的上下文环境,mymain.c中的代码在不停地执行。同时有一个中断处理程序的上下文环境,周期性地产生的时钟中断信号,能够触发myinterrupt.c中的代码。
(2) 修改代码
mypcb.h头文件
⾸先在mykernel⽬录下增加⼀个 mypcb.h头⽂件,
定义Thread结构体,其中包括指令指针ip和堆栈指针sp。
定义结构体变量PCB用来描述进程的各个参数。
声明调度函数my_schedule.
/*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 */
mymain.c中的my_start_kernel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); } } }
myinterrupt.c
#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; }
首先创建一个0号的进程,并进行初始化,然后用一个for循环又创建了3个进程,并用链表连起这四个进程。
之后这段代码又对寄存器EIP,EBP,ESP进行初始化,先将堆栈指针sp赋给了ESP寄存器,然后将堆栈指针sp内容压栈,之后将指令指针ip的内容也压栈,下一条指令是ret,它是将当前栈中ESP所指的内容出栈到EIP中,当前ESP所指的内容就是前一条指令压栈进去的ip的值,现在使得EIP寄存器的内容就是进程0的入口地址(ip内容),从而使得进程0能够被执行。
3.简要分析操作系统内核核心功能及运行工作机制
核心功能:进程管理、内存管理、I/O管理、文件管理、网络管理
工作机制:用四个进程循环完成并模拟进程切换