2017-2018-1 20155333 《信息安全系统设计基础》实验四外设驱动程序设计

2017-2018-1 20155333 《信息安全系统设计基础》实验四外设驱动程序设计

实验四外设驱动程序设计-1

• 学习资源中全课中的“hqyj.嵌入式Linux应用程序开发标准教程.pdf”中的第十一章
• 提交康奈尔笔记的照片（可以多张）

实验四外设驱动程序设计-2

• 在Ubuntu完成资源中全课中的“hqyj.嵌入式Linux应用程序开发标准教程.pdf”中的第十一章的test试验
• 提交编译，加载模块，卸载模块，测试运行的截图（要多张，全屏，体现学号信息）
• 驱动程序代码：

/* test_drv.c */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#define 	TEST_DEVICE_NAME	"test_dev"
#define		BUFF_SZ			1024

/*全局变量*/
static struct cdev test_dev;
unsigned int major =0;
static char *data = NULL;

/*函数声明*/
static ssize_t test_read(struct file *file, char *buf, size_t count, loff_t *f_pos);
static ssize_t test_write(struct file *file,const char *buffer, size_t count,loff_t *f_pos);
static int test_open(struct inode *inode, struct file *file);
static int test_release(struct inode *inode,struct file *file);

/*读函数*/
static ssize_t test_read(struct file *file, char *buf, size_t count, loff_t *f_pos)
{
	int len;
	if (count < 0 )
	{
		return -EINVAL;
	}
	len = strlen(data);
	count = (len > count)?count:len;
	if (copy_to_user(buf, data, count))
	{
		return -EFAULT;
	}
	return count;
}

/*写函数*/
static ssize_t test_write(struct file *file, const char *buffer, size_t count, loff_t *f_pos)
{
	if(count < 0)
	{
		return -EINVAL;
	}
	memset(data, 0, BUFF_SZ);
	count = (BUFF_SZ > count)?count:BUFF_SZ;
	if (copy_from_user(data, buffer, count))
	{
		return -EFAULT;
	}
	return count;
}

/*打开函数*/
static int test_open(struct inode *inode, struct file *file)
{
	printk("This is open operation\n");
	data = (char*)kmalloc(sizeof(char) * BUFF_SZ, GFP_KERNEL);
	if (!data)
	{
		return -ENOMEM;
	}
	memset(data, 0, BUFF_SZ);
	return 0;
}

/*关闭函数*/
static int test_release(struct inode *inode,struct file *file)
{
	printk("This is release operation\n");
	if (data)
	{
		kfree(data);
		data = NULL;
	}
	return 0;
}

static void test_setup_cdev(struct cdev *dev, int minor,
		struct file_operations *fops)
{
	int err, devno = MKDEV(major, minor);
    
	cdev_init(dev, fops);
	dev->owner = THIS_MODULE;
	dev->ops = fops;
	err = cdev_add (dev, devno, 1);
	if (err)
	{
		printk (KERN_NOTICE "Error %d adding test %d", err, minor);
	}
}

/* tests设备的file_operations结构 */
static struct file_operations test_fops = 
{
	.owner	 = THIS_MODULE,
	.read	 = test_read,
	.write	 = test_write,
	.open	 = test_open,
	.release = test_release,
};

/*模块注册入口*/
int init_module(void)
{
	int result;
	dev_t dev = MKDEV(major, 0);

	if (major)
	{
		result = register_chrdev_region(dev, 1, TEST_DEVICE_NAME);
	}
	else 
	{
		result = alloc_chrdev_region(&dev, 0, 1, TEST_DEVICE_NAME);
		major = MAJOR(dev);
	}

	if (result < 0) 
	{
		printk(KERN_WARNING "Test device: unable to get major %d\n", major);
		return result;
	}

	test_setup_cdev(&test_dev, 0, &test_fops);
	printk("The major of the test device is %d\n", major);
	return 0;
}
/*卸载模块*/
void cleanup_module(void) 
{
	cdev_del(&test_dev);
	unregister_chrdev_region(MKDEV(major, 0), 1);
	printk("Test device uninstalled\n");
}

• 测试代码：

/* test.c */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#define 	TEST_DEVICE_FILENAME		"/dev/test_dev"
#define		BUFF_SZ				1024
int main()
{
	int fd, nwrite, nread;
	char buff[BUFF_SZ];

	fd = open(TEST_DEVICE_FILENAME, O_RDWR);
	if (fd < 0)
	{
		perror("open");
		exit(1);
	}
		
	do
	{
		printf("Input some words to kernel(enter 'quit' to exit):");
		memset(buff, 0, BUFF_SZ);
		if (fgets(buff, BUFF_SZ, stdin) == NULL)
		{
			perror("fgets");
			break;
		}
		buff[strlen(buff) - 1] = '\0';
		
		if (write(fd, buff, strlen(buff)) < 0)
		{
			perror("write");
			break;
		}
		
		if (read(fd, buff, BUFF_SZ) < 0)
		{
			perror("read");
			break;
		}
		else
		{
			printf("The read string is from kernel:%s\n", buff);
		}
		
	} while(strncmp(buff, "quit", 4));
	
	close(fd);
	exit(0);
}

运行截图：

实验中遇到的问题及解决方法

• 问题1：在执行./test_drv_load时提示权限不够。
• 解决方法：
  使用chmod+x ./test_drv_load
  加权限，在命令前面加上sudo执行。
• 问题2：Error :Removing 'test_drv':Device or resource busy
• 解决方法：未解决！