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#include <linux/module.h> #include <linux/fs.h> #include <linux/cdev.h> #include <linux/device.h> #include <linux/uaccess.h> #define BUF_SIZE 40 static int major_number; static int minor_encrypt = 0; static int minor_decrypt = 1; static int mod_param = 3; module_param(mod_param, int, 0644); static char encrypt_buffer[BUF_SIZE]; static struct cdev my_cdev; static struct class *my_class = NULL; static struct device *my_device = NULL; static int my_open(struct inode *inode, struct file *file) { // Implement open operation return 0; } static int my_release(struct inode *inode, struct file *file) { // Implement release operation return 0; } static ssize_t my_read(struct file *file, char __user *user_buffer, size_t count, loff_t *offset) { // Implement read operation int bytes_to_copy = min(count, BUF_SIZE); if (copy_to_user(user_buffer, encrypt_buffer, bytes_to_copy)) return -EFAULT; return bytes_to_copy; } static ssize_t my_write(struct file *file, const char __user *user_buffer, size_t count, loff_t *offset) { // Implement write operation int bytes_to_copy = min(count, BUF_SIZE); if (copy_from_user(encrypt_buffer, user_buffer, bytes_to_copy)) return -EFAULT; // Encrypt the buffer based on mod_param int i; for (i = 0; i < bytes_to_copy; ++i) encrypt_buffer[i] += mod_param; return bytes_to_copy; } static struct file_operations my_fops = { .owner = THIS_MODULE, .open = my_open, .release = my_release, .read = my_read, .write = my_write, }; static int __init my_init(void) { // Dynamically allocate a major number if ((major_number = register_chrdev(0, "my_module", &my_fops)) < 0) { printk(KERN_ALERT "Failed to register a major number\n"); return major_number; } // Create a class my_class = class_create(THIS_MODULE, "my_class"); if (IS_ERR(my_class)) { unregister_chrdev(major_number, "my_module"); printk(KERN_ALERT "Failed to register device class\n"); return PTR_ERR(my_class); } // Create a device my_device = device_create(my_class, NULL, MKDEV(major_number, minor_encrypt), NULL, "encrypt"); if (IS_ERR(my_device)) { class_destroy(my_class); unregister_chrdev(major_number, "my_module"); printk(KERN_ALERT "Failed to create the device\n"); return PTR_ERR(my_device); } // Initialize the character device cdev_init(&my_cdev, &my_fops); // Add the character device to the kernel if (cdev_add(&my_cdev, MKDEV(major_number, minor_encrypt), 1) < 0) { device_destroy(my_class, MKDEV(major_number, minor_encrypt)); class_destroy(my_class); unregister_chrdev(major_number, "my_module"); printk(KERN_ALERT "Failed to add the device to the kernel\n"); return -1; } // Create /dev/decrypt node my_device = device_create(my_class, NULL, MKDEV(major_number, minor_decrypt), NULL, "decrypt"); if (IS_ERR(my_device)) { class_destroy(my_class); unregister_chrdev(major_number, "my_module"); printk(KERN_ALERT "Failed to create the device\n"); return PTR_ERR(my_device); } // Initialize the character device for /dev/decrypt cdev_init(&my_cdev, &my_fops); // Add the character device to the kernel for /dev/decrypt if (cdev_add(&my_cdev, MKDEV(major_number, minor_decrypt), 1) < 0) { device_destroy(my_class, MKDEV(major_number, minor_decrypt)); class_destroy(my_class); unregister_chrdev(major_number, "my_module"); printk(KERN_ALERT "Failed to add the device to the kernel\n"); return -1; } printk(KERN_INFO "Module loaded with major number %d\n", major_number); return 0; } static void __exit my_exit(void) { // Clean up the module device_destroy(my_class, MKDEV(major_number, minor_encrypt)); device_destroy(my_class, MKDEV(major_number, minor_decrypt)); class_unregister(my_class); class_destroy(my_class); unregister_chrdev(major_number, "my_module"); printk(KERN_INFO "Module unloaded\n"); } module_init(my_init); module_exit(my_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Your Name"); MODULE_DESCRIPTION("Simple character device driver for encryption/decryption");
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