Part 2: Kernel Fundamentals

This part covers the essential concepts every kernel developer must understand: architecture, module lifecycle, coding conventions, and error handling patterns.

What You’ll Learn

Kernel vs user space architecture
Module initialization and cleanup
Module parameters and symbol exporting
Kernel coding style and conventions
Kernel data types and endianness
Error handling patterns

Prerequisites

Complete Part 1: Getting Started or have a working development environment.

Chapter Overview

Chapter	Topic	Description
2.1	Kernel Architecture	User space vs kernel space, privilege levels
2.2	Module Lifecycle	init/exit, module_param, EXPORT_SYMBOL
2.3	Coding Style	Kernel conventions, checkpatch.pl
2.4	Data Types	Fixed-width types, endianness handling
2.5	Error Handling	ERR_PTR, goto cleanup, return conventions
2.6	Kernel API	Common macros and helper functions
2.7	Data Structures	Linked lists, hash tables, red-black trees

Key Concepts

The Kernel Environment

The kernel environment differs significantly from user space:

Aspect	User Space	Kernel Space
Memory	Virtual, protected	Direct physical access
Stack	Large (MB)	Small (8-16 KB)
Libraries	Full C library	Kernel-only APIs
Errors	Exceptions possible	Must handle explicitly
Floating point	Available	Generally unavailable

Why This Matters

Understanding these fundamentals helps you:

Write stable, crash-free drivers
Avoid common kernel programming pitfalls
Follow kernel conventions for upstream acceptance
Debug issues more effectively

Examples

This part includes two example modules:

examples/part2/module-params/ - Module parameters demonstration
examples/part2/export-symbol/ - Symbol exporting between modules
examples/part2/data-structures/ - Linked list and hash table operations