linux内核编程之内核与用户数据读写

Linux内核模块：设备驱动与用户空间交互示例

最新推荐文章于 2025-11-29 19:25:01 发布

原创最新推荐文章于 2025-11-29 19:25:01 发布 · 185 阅读

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该文章展示了一个简单的Linux内核模块，创建了一个设备驱动，该驱动注册了一个字符设备并实现了读写操作。用户空间应用通过打开/dev/hellodev文件进行通信，实现数据的读写。内核模块通过`module_init`和`module_exit`宏注册初始化和退出函数，而用户应用程序则通过标准I/O函数与驱动交互。

内核模块

makefile

ARCH=x86
CROSS_CMPILE=

KVERSION = $(shell uname -r)
KERNEL_DIR = /lib/modules/$(KVERSION)/build

.PHONY:all clean
all:
	make -C $(KERNEL_DIR) M=$(shell pwd) modules

clean:
	make -C $(KERNEL_DIR) M=$(shell pwd) modules clean
	rm -rf modules.order

obj-m 	+= kernel_io.o

kernel_io.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/device.h>

static int major = 0;
static char sdata[64] = {0};
static int sdatalen = 0;
static struct class* class_for_hello;

// 与struct file_operations 中的read格式匹配
static ssize_t hello_read (struct file *file, char __user *buf, size_t size, loff_t *offset) {
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	copy_to_user(buf, sdata, sdatalen);
	return sdatalen;
}

// 与struct file_operations 中的write格式匹配
static ssize_t hello_write (struct file *file, const char __user *buf, size_t size, loff_t *offset) {
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	sdatalen=size;
	copy_from_user(sdata, buf, sdatalen);
	return sdatalen;
}

// 文件操作描述体
static struct file_operations hello_fops = {
	.owner		= THIS_MODULE,
	.read       = hello_read,
	.write      = hello_write,
};

int __init hello_init(void) {
	printk("hello drv init\n");
	major = register_chrdev(0, "hello_drv", &hello_fops);
	
	class_for_hello = class_create(THIS_MODULE, "helloclass");

	/* create /dev/hellodev */
	device_create(class_for_hello, NULL, MKDEV(major, 0), NULL, "hellodev");
	
	return 0;
}

void __exit hello_exit(void) {
	printk("hello drv exit\n");
	device_destroy(class_for_hello, MKDEV(major, 0));
	class_destroy(class_for_hello);
	unregister_chrdev(major, "hello_drv");
}

module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");

用户app

user_io.c


#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char **argv) {
	int fd;
	char buf[1024];
	int len;
	int ret;
	
	/* 1. 判断参数 */
	if (argc < 2) {
		printf("Usage: %s -w <string>\n", argv[0]);
		printf("       %s -r\n", argv[0]);
		return -1;
	}

	/* 2. 打开文件 */
	fd = open("/dev/hellodev", O_RDWR);
	if (fd == -1) {
		printf("can not open file /dev/hellodev\n");
		return -1;
	}
	
	printf("open file /dev/hellodev ok\n");

	/* 3. 写文件或读文件 */
	if ((0 == strcmp(argv[1], "-w")) && (argc == 3)) {
		len = strlen(argv[2]) + 1;
		len = len < 1024 ? len : 1024;
		ret = write(fd, argv[2], len);
		printf("write driver: %d\n", ret);
	}
	else {
		len = read(fd, buf, 1024);		
		printf("read driver: %d\n", len);
		buf[1023] = '\0';
		printf("APP read : %s\n", buf);
	}
	
	close(fd);
	
	return 0;
}