要求：基于Linux的内存模拟型的字符IO设备驱动程序的设计，并编写应用程序实现线程间的通信。

基于Linux的内存模拟型的字符IO设备驱动程序的设计

1 内存模拟型的字符IO设备驱动程序memDrv.c2 IO设备驱动实现线程间的通信的程序memIoDrv.c3 Makefile文件4 程序执行步骤4.1 使用make命令4.2 查看当前系统中已经注册的字符设备的主设备号4.3 加载设备驱动模块memDrv.ko4.4 创建与memDrv驱动对应的设备节点文件4.5 编译线程间通信程序4.6 运行应用程序

1 内存模拟型的字符IO设备驱动程序memDrv.c

#include <linux/module.h>#include <linux/fs.h>#include <linux/init.h>#include <linux/cdev.h>#include <linux/slab.h>#include <linux/uaccess.h>#define MEMDEV_MAJOR 100 /*预设的mem的主设备号*/#define MEMDEV_NR_DEVS 2 /*设备数*/#define MEMDEV_SIZE 4096 /*内存大小*//*mem设备描述结构体*/struct mem_dev {char *data; unsigned long size; };static int mem_major = MEMDEV_MAJOR; //定义主设备号module_param(mem_major, int, S_IRUGO); //模块传参struct mem_dev *mem_devp; /*设备结构体指针*/struct cdev cdev; /*文件打开函数*/int mem_open(struct inode *inode, struct file *filp){struct mem_dev *dev;/*获取次设备号*/int num = MINOR(inode->i_rdev);if (num >= MEMDEV_NR_DEVS) return -ENODEV;dev = &mem_devp[num];/*将设备描述结构指针赋值给文件私有数据指针*/filp->private_data = dev;return 0; }/*文件释放函数*/int mem_release(struct inode *inode, struct file *filp){return 0;}/*读函数*/static ssize_t mem_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos){unsigned long p = *ppos; /*记录文件指针偏移位置*/ unsigned int count = size;/*记录需要读取的字节数*/ int ret = 0;/*返回值*/ struct mem_dev *dev = filp->private_data; /*获得设备结构体指针*//*判断读位置是否有效*/if (p >= MEMDEV_SIZE) /*要读取的偏移大于设备的内存空间*/ return 0;if (count > MEMDEV_SIZE - p)/*要读取的字节大于设备的内存空间*/ count = MEMDEV_SIZE - p;/*读数据到用户空间:内核空间->用户空间交换数据*/ if (copy_to_user(buf, (void*)(dev->data + p), count)){ret = - EFAULT;}else{*ppos += count;ret = count;printk(KERN_INFO "read %d bytes(s) from %d\n", count, p);}return ret;}/*写函数*/static ssize_t mem_write(struct file *filp, const char __user *buf, size_t size, loff_t *ppos){unsigned long p = *ppos;unsigned int count = size;int ret = 0;struct mem_dev *dev = filp->private_data; /*获得设备结构体指针*//*分析和获取有效的写长度*/if (p >= MEMDEV_SIZE)return 0;if (count > MEMDEV_SIZE - p) /*要写入的字节大于设备的内存空间*/count = MEMDEV_SIZE - p;/*从用户空间写入数据*/if (copy_from_user(dev->data + p, buf, count))ret = - EFAULT;else{*ppos += count;/*增加偏移位置*/ ret = count;/*返回实际的写入字节数*/ printk(KERN_INFO "written %d bytes(s) from %d\n", count, p);}return ret;}/* seek文件定位函数 */static loff_t mem_llseek(struct file *filp, loff_t offset, int whence){loff_t newpos;switch(whence) {case 0: /* SEEK_SET */ /*相对文件开始位置偏移*/ newpos = offset; /*更新文件指针位置*/break;case 1: /* SEEK_CUR */newpos = filp->f_pos + offset; break;case 2: /* SEEK_END */newpos = MEMDEV_SIZE -1 + offset;break;default: /* can't happen */return -EINVAL;}if ((newpos<0) || (newpos>MEMDEV_SIZE))return -EINVAL;filp->f_pos = newpos;return newpos;}/*文件操作结构体*/static const struct file_operations mem_fops ={.owner = THIS_MODULE,.llseek = mem_llseek,.read = mem_read,.write = mem_write,.open = mem_open,.release = mem_release,};/*设备驱动模块加载函数*/static int memdev_init(void){int result;int i;dev_t devno = MKDEV(mem_major, 0);/* 申请设备号，当xxx_major不为0时，表示静态指定；当为0时，表示动态申请*/ /* 静态申请设备号*/if (mem_major)result = register_chrdev_region(devno, 2, "memdev");else /* 动态分配设备号 */{result = alloc_chrdev_region(&devno, 0, 2, "memdev");mem_major = MAJOR(devno); /*获得申请的主设备号*/} if (result < 0)return result;/*初始化cdev结构，并传递file_operations结构指针*/ cdev_init(&cdev, &mem_fops); cdev.owner = THIS_MODULE; /*指定所属模块*/cdev.ops = &mem_fops;/* 注册字符设备 */cdev_add(&cdev, MKDEV(mem_major, 0), MEMDEV_NR_DEVS);/* 为设备描述结构分配内存*/mem_devp = kmalloc(MEMDEV_NR_DEVS * sizeof(struct mem_dev), GFP_KERNEL);if (!mem_devp) /*申请失败*/{result = - ENOMEM;goto fail_malloc;}memset(mem_devp, 0, sizeof(struct mem_dev));/*为设备分配内存*/for (i=0; i < MEMDEV_NR_DEVS; i++) {mem_devp[i].size = MEMDEV_SIZE;mem_devp[i].data = kmalloc(MEMDEV_SIZE, GFP_KERNEL);memset(mem_devp[i].data, 0, MEMDEV_SIZE);}return 0;fail_malloc: unregister_chrdev_region(devno, 1);return result;}/*模块卸载函数*/static void memdev_exit(void){cdev_del(&cdev); /*注销设备*/kfree(mem_devp);/*释放设备结构体内存*/unregister_chrdev_region(MKDEV(mem_major, 0), 2); /*释放设备号*/}MODULE_AUTHOR("Wenxiaohong");MODULE_LICENSE("GPL");module_init(memdev_init);module_exit(memdev_exit);

2 IO设备驱动实现线程间的通信的程序memIoDrv.c

/* written by wenxiaohong chongqing university at 1225 *//* Confidential for Chongqing University */#include <stdio.h>#include <fcntl.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>#include <pthread.h>#include <semaphore.h>#define memIoDev_NAME "/dev/memDrv"#define THREAD_NUM 2#define THREAD1_MSG3#define THREAD2_MSG3sem_t sem; //semaphorestruct msg {// data structure for msg passingint tid;// task id int value; // msg value };int memIoFd;void * thread1_handler(void *arg);void * thread2_handler(void *arg);int main(){int i;pthread_t tid[THREAD_NUM];if(sem_init(&sem, 0, 0) == -1) //初始化信号量，其初值为0{perror("semaphore intitialization failed\n");return 0;}if((memIoFd = open(memIoDev_NAME,O_RDWR)) < 0) //打开设备文件{printf("open memDrv Error! FD:%d\n",memIoFd);return 0;}else{printf("open memDrv sucess!\n");}pthread_create(&tid[0], NULL, thread1_handler, NULL); //创建第一个线程pthread_create(&tid[1], NULL, thread2_handler, NULL); //创建第二个线程for(i = 0; i < THREAD_NUM; i++){pthread_join(tid[i],NULL);}//cleaning semaphoresem_destroy(&sem);return 0;}void * thread1_handler(void *arg){int count;int value;struct msg thread1Item; printf ("thread1 started: thread1 id = %#x\n", pthread_self());for (count = 1; count <= THREAD1_MSG; count++){value = count * 10; //Fill in the data structure for message passing thread1Item.tid = pthread_self ();thread1Item.value = value;//Send Messages if ((write (memIoFd, (char *)&thread1Item, sizeof (thread1Item))) == 0) {perror ("Error in sending the message"); return 0; } elseprintf ("thread1: id = %#x, sent value = %d \n", pthread_self(), value);}sem_post(&sem); //Acquire a semaphore(+1)pthread_exit(NULL);}void * thread2_handler(void *arg){int count;struct msg thread2Item; sem_wait(&sem); //Release the semaphore (-1)printf ("thread2 started: thread2 id = %#x\n", pthread_self());lseek(memIoFd,0,SEEK_SET);for (count = 1; count <= THREAD2_MSG; count++){//Receive Messages if ((read (memIoFd, (char *)&thread2Item, sizeof (thread2Item))) == 0) {perror ("Error in receiving the message"); return 0; } elseprintf ("thread2: id = %#x, received msg of value %d from tid = %#x\n",pthread_self(), thread2Item.value, thread2Item.tid);}pthread_exit(NULL);}

3 Makefile文件

Makefile文件将编译memDrv.c编译为设备驱动模块memDrv.ko。

CONFIG_MODULE_SIG=n# Kernel modulesobj-m += memDrv.o# Specify flags for the module compilation.build: kernel_moduleskernel_modules:make -C /usr/src/linux-headers-$(shell uname -r) M=$(CURDIR) modulesclean:make -C /usr/src/linux-headers-$(shell uname -r) M=$(CURDIR) clean

4 程序执行步骤

运行环境为：ubantu16.04

4.1 使用make命令

利用make命令将memDrv.c编译为设备驱动模块memDrv.ko。

4.2 查看当前系统中已经注册的字符设备的主设备号

使用cat /proc/devices命令查看当前系统中已经注册的字符设备或者块设备的主设备号。可以看出图3中没有主设备号为100的字符设备，所以我们下一步就加载驱动模块。

4.3 加载设备驱动模块memDrv.ko

使用“insmod”命令加载设备驱动模块memDrv.ko，可以从图中看出主设备号为100的驱动模块已经加载成功。

4.4 创建与memDrv驱动对应的设备节点文件

使用“mknod”命令在/dev目录下创建与memDrv驱动对应的设备节点文件，memIoDrv应用程序就是通过操作这个设备节点文件来完成对memDrv设备的读和写，进而完成线程间通信。

其中“mknod”是创建节点命令 ，“/dev/memDrv”是要创建的节点文件c”表示这是个字符设备，“100”是设备的主设备号，“0”是设备的次设备号。创建完成以后就会存在/dev/memDrv这个文件。

4.5 编译线程间通信程序

使用“gcc”命令编译线程间通信程序，注意此时memIoDrv.c中使用了线程，所以编译命令中要加入**“-lpthread”选项。**

4.6 运行应用程序

使用“sudo ./memIoDrv”运行应用程序，注意需要加上sudo，否则权限不够。下图中可以看出线程1分别写入了三个数据，线程2也读取到了对应的三个数据，与作业二有所不同，Linux中写完一段内存可以自动偏移，而不是覆盖，所以线程2可以读到三个数据。值得注意的是，线程2在读取前，需要使用lseek函数将文件读写指针置于文件头，即将文件偏移量置0。