- 一、三个法宝
- 二、实验步骤
- 1.输入指令编译运行mykernel
- 2.查看mymain.c与myinterrupt.c源代码
- 3.完成一个简单的时间片轮转多道程序
- 三、遇到的问题
存储程序计算机、函数调用堆栈机制、中断
二、实验步骤 1.输入指令编译运行mykernel指令如下：
# 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
执行结果：
mymain.c
void __init my_start_kernel(void)
{
int i = 0;
while(1)
{
i++;
if(i%100000 == 0)
printk(KERN_NOTICE "my_start_kernel here %d n",i);
//在my_start_kernel函数中，不停循环输出 my_start_kernel here
}
}
myinterrupt.c
void my_timer_handler(void)
{
printk(KERN_NOTICE "n>>>>>>>>>>>>>>>>>my_timer_handler here<<<<<<<<<<<<<<<<<
3.完成一个简单的时间片轮转多道程序
mymain.c
#include
#include
#include
#include
#include
#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;
task[pid].pid = pid;
task[pid].state = 0;
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];
for(i=1;ipid);
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
#include
#include
#include
#include
#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;
void my_timer_handler(void)
{
if(time_count%1000 == 0 && my_need_sched != 1)
{
printk(KERN_NOTICE ">>>my_timer_handler here<<next == NULL)
{
return;
}
printk(KERN_NOTICE ">>>my_schedule<<next;
prev = my_current_task;
if(next->state == 0)
{
my_current_task = next;
printk(KERN_NOTICE ">>>switch %d to %d<<pid,next->pid);
asm volatile(
"pushl %%ebpnt"
"movl %%esp,%0nt"
"movl %2,%%espnt"
"movl $1f,%1nt"
"pushl %3nt"
"retnt"
"1:t"
"popl %%ebpnt"
: "=m" (prev->thread.sp),"=m" (prev->thread.ip)
: "m" (next->thread.sp),"m" (next->thread.ip)
}
return;
}
mypcb.h
#define MAX_TASK_NUM 4
#define KERNEL_STACK_SIZE 1024*2
struct Thread {
unsigned long ip;
unsigned long sp;
};
typedef struct PCB{
int pid;
volatile long state;
unsigned long stack[KERNEL_STACK_SIZE];
struct Thread thread;
unsigned long task_entry;
struct PCB *next;
}tPCB;
void my_schedule(void);
执行结果：
代码分析：
mymain.c
#include
#include
#include
#include
#include
#include "mypcb.h"
tPCB task[MAX_TASK_NUM];
//定义了一个类型为PCB的task数组
tPCB * my_current_task = NULL;
//定义了一个PCB类型的指针变量并且初值为空
volatile int my_need_sched = 0;//进程是否需要调度的标志位
void my_process(void);
//声明函数
void __init my_start_kernel(void)//对内核进行初始化
{
int pid = 0;//定义0号进程
int i;
task[pid].pid = pid;
task[pid].state = 0;
task[pid].task_entry = task[pid].thread.ip = (unsigned long)my_process;//定义了0号进程的入口为my_process方法的首地址
task[pid].thread.sp = (unsigned long)&task[pid].stack[KERNEL_STACK_SIZE-1];
task[pid].next = &task[pid];
for(i=1;ipid);
if(my_need_sched == 1)
{
my_need_sched = 0;//将标志位置0
my_schedule();//执行my_schedule()方法
}
printk(KERN_NOTICE "this is process %d +n",my_current_task->pid);
}
}
}
myinterrupt.c
#include
#include
#include
#include
#include
#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;//时间计数器
void my_timer_handler(void)//时间中断程序
{
if(time_count%1000 == 0 && my_need_sched != 1)
{
printk(KERN_NOTICE ">>>my_timer_handler here<<next == NULL)
{
return;
}//如果当前任务为空或者没有其他进程需要执行返回
printk(KERN_NOTICE ">>>my_schedule<<next;
prev = my_current_task;
if(next->state == 0)
{
my_current_task = next;
printk(KERN_NOTICE ">>>switch %d to %d<<pid,next->pid);
asm volatile(
"pushl %%ebpnt"
"movl %%esp,%0nt"
"movl %2,%%espnt"
"movl $1f,%1nt"
"pushl %3nt"
"retnt"
"1:t"
"popl %%ebpnt"
: "=m" (prev->thread.sp),"=m" (prev->thread.ip)
: "m" (next->thread.sp),"m" (next->thread.ip)
);
//嵌入式汇编保存了当前进程的PCB信息用来为进程调度做准备
}
return;
}
mypcb.h
#define MAX_TASK_NUM 4
#define KERNEL_STACK_SIZE 1024*2
struct Thread {
unsigned long ip;
unsigned long sp;
}; //定义了一个结构体用来保存当前ip和sp
typedef struct PCB{
int pid; //进程号
volatile long state;
unsigned long stack[KERNEL_STACK_SIZE];
//内核堆栈大小
struct Thread thread;
//一个Thread类型的结构体变量thread
unsigned long task_entry;//程序入口
struct PCB *next;//用来将PCB链接起来的链表
}tPCB;
void my_schedule(void);//声明进程调度函数
三、遇到的问题
1.实验中遇到的问题：执行make指令时出现错误
解决：查看代码后发现代码有错误，改正错误后重新make再执行。
2.本周学习中遇到的问题：fatal error:openssl/evp.h:没有那个文件或目录
问题出现的原因：尝试编译的程序使用OpenSSL，但是需要和OpenSSL链接的文件（库和头文件）在使用的Linux平台上缺少。
解决方案：要在Debian、Ubuntu或者其他衍生版上安装OpenSSL：
$ sudo apt-get install libssl-dev
