在Linux系统中实现一个可加载的内核模块

Intro

坐标成都电讯大专, 某操作系统课老师在PPT上草草写下3个内核线程API后就要求编程, 感受一下:

include/linux/kthread.h，你就看到了它全部的API，一共三个函数。

这里是代码声明，略
kthread_run()负责内核线程的创建， kthread_stop()负责结束创建的线程，参数是创建时返回的task_struct指针。 kthread_should_stop()返回should_stop标志。它用于创建的线程检查结束标志，并决定是否退出。

利用上面提到的系统调用，在Linux系统中实现一个可加载的内核模块，里面至少包含一个内核线程

我看完之后的感受

编程准备

准备一个CentOS 6.10的虚拟机, 下面是可能用得到的链接

CentOS 6.10
换源

安装完毕后给自己的账户添加root权限或者直接用root账户(并不推荐这么做)

然后更新yum源(不会的见前面的链接)

由于CentOS 6年久失修, 需要先更换yum的软件源才能使用yum来安装必要的组件

我使用的源如下

# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-6.10 - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6#released updates 
[updates]
name=CentOS-6.10 - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6#additional packages that may be useful
[extras]
name=CentOS-6.10 - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-6.10 - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6#contrib - packages by Centos Users
[contrib]
name=CentOS-6.10 - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6

换源后清除缓存, 刷新缓存

sudo yum clean all
sudo yum makecache

安装一些必须品

sudo yum install gcc make
sudo yum install kernel-devel-2.6.32-754.el6.x86_64

注: 这里安装内核头文件包(也就是第二条命令)中的版本号需要使用uname -r命令来确定

开始编程

叫来ChatGPT, 生成下面的代码

my_module.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/kthread.h>static struct task_struct *my_thread;static int thread_function(void *data)
{while (!kthread_should_stop()){printk(KERN_INFO "My kernel thread is running\n");msleep(1000);  // sleep for 1 second}return 0;
}static int __init my_module_init(void)
{printk(KERN_INFO "My kernel module is loaded\n");my_thread = kthread_create(thread_function, NULL, "my_thread");if (my_thread)wake_up_process(my_thread);return 0;
}static void __exit my_module_exit(void)
{printk(KERN_INFO "My kernel module is unloaded\n");if (my_thread)kthread_stop(my_thread);
}module_init(my_module_init);
module_exit(my_module_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("A simple kernel module with a kernel thread");

Makefile

注意: 此处的文件名首字母一定要大写, 即一定要写成Makefile而不是makefile

# 下面一行的"my_module"需要与上面的C源文件的名字部分保持一致
obj-m += my_module.oall:make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) modulesclean:make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) clean

写完保存, 然后在项目目录下打开终端, 输入