08 done

08/main.c

@@ -0,0 +1,76 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/miscdevice.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Louis Solofrizzo <louis@ne02ptzero.me>");
+MODULE_DESCRIPTION("Useless module");
+
+static ssize_t myfd_read (struct file *fp, char __user *user,
+size_t size, loff_t *offs);
+static ssize_t myfd_write(struct file *fp, const char __user *user,
+size_t size, loff_t *offs);
+
+static struct file_operations myfd_fops = {
+	.owner = THIS_MODULE,
+	.read = &myfd_read,
+	.write = &myfd_write
+};
+
+static struct miscdevice myfd_device = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "reverse",
+	.fops = &myfd_fops
+};
+
+char str[PAGE_SIZE];
+DEFINE_MUTEX(rw_lock);
+
+static int __init myfd_init(void)
+{
+	mutex_init(&rw_lock);
+	return misc_register(&myfd_device);
+}
+
+static void __exit myfd_cleanup(void)
+{
+	misc_deregister(&myfd_device);
+}
+
+ssize_t myfd_read(struct file *fp, char __user *user, size_t size, loff_t *offs)
+{
+	ssize_t retval;
+	size_t len;
+	char *tmp;
+	
+	mutex_lock(&rw_lock);
+	len = strlen(str);
+	tmp = kmalloc(sizeof(char) * PAGE_SIZE, GFP_KERNEL);
+	for (size_t i = 0,j = len - 1; i < len; i++, j--) {
+		tmp[i] = str[j];
+	}
+	tmp[len] = 0;
+	retval = simple_read_from_buffer(user, size, offs, tmp, len);
+	mutex_unlock(&rw_lock);
+	return retval;
+}
+
+ssize_t myfd_write(struct file *fp, const char __user *user, size_t size,
+		loff_t *offs)
+{
+	ssize_t res;
+
+	if(size >= (PAGE_SIZE - 1))
+		return -EINVAL;
+	mutex_lock(&rw_lock);
+	res = simple_write_to_buffer(str, size, offs, user, size);
+	str[res] = 0x0;
+	mutex_unlock(&rw_lock);
+	return res;
+}
+
+module_init(myfd_init);
+module_exit(myfd_cleanup);