"Invalid module format" when inserting a custom Linux kernel module

Question

I'm trying to write a Linux kernel module, but I'm stuck just writing some stub code. I've compiled this code in Ubuntu:

#include <linux/module.h>
int init_module(void){ printk("<1> hellp"); return 0;}
void cleanup_module(void){ printk("<1> bye");}

However, when I try to insmod it I get the error:

Invalid module format

After googling I figured it may be some problem with version compatibility, but I'm not sure. What am I doing wrong?

Answer 1

You're missing the MODULE_ parameters, here's an empty kernel project:

#include <linux/module.h>
#include <linux/kernel.h>

static void __exit cleanup(void)
{
}


static int __init startup(void)
{
}

module_init(startup);
module_exit(cleanup);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Someone Like You");