Modules

Kernel modules are collections of code, that can be loaded and unloaded from kernel on demand.

Example hello.c file

#include <linux/module.h>    // included for all kernel modules
#include <linux/kernel.h>    // included for KERN_INFO
#include <linux/init.h>      // included for __init and __exit macros

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Lakshmanan");
MODULE_DESCRIPTION("A Simple Hello World module");

static int __init hello_init(void)
{
    printk(KERN_INFO "Hello world!\n");
    return 0;    // Non-zero return means that the module couldn't be loaded.
}

static void __exit hello_cleanup(void)
{
    printk(KERN_INFO "Cleaning up module.\n");
}

module_init(hello_init);
module_exit(hello_cleanup);

List all Modules (that are loaded into memory)

$ lsmod

Create new Module

$ sudo insmod <path to the new module.ko>

Run it (i think???)

# prints the last output from the module
# dmesg prints everything
$ dmesg | tail -1

Info on Module

$ modinfo <path to the new module.ko>

Remove Module

$ rmmod <path to the new module.ko>

Probe

loads and unloads modules based dependencies