编写一个简单的模拟设备驱动程序，编译成内核模块，并将之装载到内存中，编写程序调用该模块

以下是一个简单的模拟设备驱动程序的代码示例，该驱动程序将创建一个名为 "mydevice" 的字符设备，并支持读取和写入操作： ```c #include <linux/module.h> #include <linux/kernel.h> #include <linux/fs.h> #include <linux/uaccess.h> #define DEVICE_NAME "mydevice" #define BUFFER_SIZE 1024 static char device_buffer[BUFFER_SIZE]; static int pos = 0; static int device_open(struct inode *inode, struct file *file) { printk(KERN_INFO "Device opened\n"); return 0; } static int device_release(struct inode *inode, struct file *file) { printk(KERN_INFO "Device closed\n"); return 0; } static ssize_t device_read(struct file *file, char *buffer, size_t length, loff_t *offset) { int bytes_read = 0; if (pos >= BUFFER_SIZE) { return 0; } while (length && pos < BUFFER_SIZE) { put_user(device_buffer[pos], buffer++); length--; pos++; bytes_read++; } return bytes_read; } static ssize_t device_write(struct file *file, const char *buffer, size_t length, loff_t *offset) { int bytes_written = 0; if (pos >= BUFFER_SIZE) { return -ENOSPC; } while (length && pos < BUFFER_SIZE) { get_user(device_buffer[pos], buffer++); length--; pos++; bytes_written++; } return bytes_written; } static struct file_operations fops = { .open = device_open, .release = device_release, .read = device_read, .write = device_write, }; static int __init mydevice_init(void) { int ret = register_chrdev(0, DEVICE_NAME, &fops); if (ret < 0) { printk(KERN_ALERT "Failed to register device\n"); return ret; } printk(KERN_INFO "Device registered\n"); return 0; } static void __exit mydevice_exit(void) { unregister_chrdev(0, DEVICE_NAME); printk(KERN_INFO "Device unregistered\n"); } module_init(mydevice_init); module_exit(mydevice_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Your Name"); MODULE_DESCRIPTION("A simple device driver"); ``` 将上述代码保存为 mydevice.c 文件，并在终端中使用以下命令编译为内核模块： ```bash make -C /lib/modules/$(uname -r)/build M=$(pwd) modules ``` 编译成功后，将会生成名为 mydevice.ko 的内核模块文件。接下来，使用以下命令将该模块装载到内存中： ```bash sudo insmod mydevice.ko ``` 使用以下命令查看模块是否成功装载： ```bash lsmod | grep mydevice ``` 最后，可以编写一个用户程序来调用该模块，以下是一个简单的示例程序： ```c #include <stdio.h> #include <fcntl.h> #include <unistd.h> #define DEVICE_PATH "/dev/mydevice" #define BUFFER_SIZE 1024 int main() { int fd = open(DEVICE_PATH, O_RDWR); if (fd == -1) { perror("Failed to open device"); return 1; } char buffer[BUFFER_SIZE]; int bytes_read = read(fd, buffer, BUFFER_SIZE); if (bytes_read == -1) { perror("Failed to read from device"); return 1; } printf("Read %d bytes from device: %s\n", bytes_read, buffer); char *message = "Hello, device!"; int bytes_written = write(fd, message, strlen(message)); if (bytes_written == -1) { perror("Failed to write to device"); return 1; } printf("Wrote %d bytes to device\n", bytes_written); close(fd); return 0; } ``` 该程序将打开 mydevice 设备，并进行读取和写入操作。将上述代码保存为 myprogram.c 文件，并使用以下命令编译： ```bash gcc -o myprogram myprogram.c ``` 编译成功后，可以运行该程序： ```bash ./myprogram ```