Kernel Module Development for Linux

Kernel Module Development for Linux

Kernel modules are pieces of code that can be dynamically loaded and unloaded into the Linux kernel, providing additional functionality such as device drivers or system utilities.

Developing kernel modules involves understanding the Linux kernel API and programming in C. Module development typically involves:

1. Module Initialization: Modules must initialize and register themselves with the kernel during load time. This often involves setting up data structures, allocating resources, and registering callback functions.
2. Module Cleanup: Modules must properly clean up and deregister themselves when unloaded from the kernel. This involves releasing allocated resources, unregistering callback functions, and freeing memory.
3. Module Functionality: Modules implement specific functionality, such as device drivers for hardware components, file system extensions, or system monitoring utilities.

Kernel modules can interact with the kernel through the kernel symbol table, which provides access to kernel functions and data structures. However, module developers must be cautious and follow kernel coding conventions to ensure stability and security.

Lab Activities

Simple Kernel Module Lab Activity

Below is a simple example of a kernel module that prints a message when loaded and unloaded:

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

        static int __init hello_init(void) {
            printk(KERN_INFO "Hello, kernel!\n");
            return 0;
        }

        static void __exit hello_exit(void) {
            printk(KERN_INFO "Goodbye, kernel!\n");
        }

        module_init(hello_init);
        module_exit(hello_exit);

        MODULE_LICENSE("GPL");
        MODULE_AUTHOR("Your Name");
        MODULE_DESCRIPTION("A simple kernel module");
    

To compile and load this module:

        $ make
        $ sudo insmod hello.ko
    

To unload the module:

        $ sudo rmmod hello