add assignement 00 to 08

07/foo.c

@@ -0,0 +1,60 @@
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/debugfs.h>
+#include <linux/mm.h>
+#include <linux/mutex.h>
+
+extern struct dentry *module_dir;
+
+ssize_t foo_read(struct file *f, char __user *buf, size_t len, loff_t *off);
+ssize_t foo_write(struct file *f, const char __user *buf, size_t len, loff_t *off);
+int init_foo(void);
+
+char buffer[PAGE_SIZE];
+size_t buffer_len = 0;
+DEFINE_MUTEX(rw_lock);
+
+static const struct file_operations fops = {
+	.owner = THIS_MODULE,
+	.read = foo_read,
+	.write = foo_write,
+};
+
+
+ssize_t foo_read(struct file *f, char __user *buf, size_t len, loff_t *off)
+{
+	size_t read;
+	
+	mutex_lock(&rw_lock);
+	read = simple_read_from_buffer(buf, len, off, buffer, buffer_len);
+	mutex_unlock(&rw_lock);
+	return read;
+}
+
+
+ssize_t foo_write(struct file *f, const char __user *buf, size_t len, loff_t *off)
+{
+	if (len > sizeof(buffer))
+		return -EINVAL;
+	mutex_lock(&rw_lock);
+	if (copy_from_user(buffer, buf, len))
+	{
+		mutex_unlock(&rw_lock);
+		return -EINVAL;
+	}
+	buffer_len = len;
+	mutex_unlock(&rw_lock);
+	return len;
+}
+
+int init_foo(void)
+{
+	struct dentry *ret;
+
+	mutex_init(&rw_lock);
+	ret = debugfs_create_file("foo", 0644, module_dir, NULL, &fops);
+	if (IS_ERR(ret)) return PTR_ERR(ret);
+	return 0;
+}