Navigating the Kernel: A Comprehensive Guide to Kernel Programming

In the realm of computer science, kernel programming stands as one of the most revered and intricate disciplines. The kernel, often described as the heart of an operating system, orchestrates the symphony between hardware and software. This post is designed to be your compass as you venture into the fascinating world of kernel programming. Whether you’re a novice aspiring to demystify the nuances of the kernel or a seasoned developer aiming to refine your expertise, this guide will navigate you through the intricacies, challenges, and rewards of kernel programming. Embark on this journey with us as we delve deep into the layers of the operating system, exploring the kernel’s vast expanse and its profound impact on computing.

The Ultimate Learning Path for System Programming

1. Linux User Space Debugging
– Debugging Linux User Applications (gdb, valgrind, strace, ltrace)

2. Introduction to Linux Kernel Programming
– Understanding Kernel Modules vs. Device Drivers
– Advantages and Disadvantages of Kernel Modules
– Compilation Process for Linux Kernel Modules
– Key Commands for Kernel Modules Management (lsmod, rmmod, insmod, etc.)
– Parameter Passing to Linux Kernel Modules
– Exporting Symbols in the Kernel
– Kernel Panics, Oops, BUGs, and WARNs

3. Process Management in the Kernel
– Creation of Kernel Threads
– Module Metadata and Printk Functionality

4. Character Device Drivers Deep Dive
– Writing Character Device Drivers from Scratch
– Understanding Various File Operations
– Device Number and Device File Concepts
– Allocating Device Numbers (Static vs. Dynamic)
– Creating Device Files (Manual vs. Udev)
– Registering Devices with the Kernel
– Data Transfer Between User Space and Kernel Space
– Handling Error Cases in Ioctl Implementation
– Signalling User Space from Kernel Space
– Access Control Mechanisms in Kernel

5. Memory Management in the Linux Kernel
– Understanding Physical vs. Virtual Address Spaces
– Distinguishing Kernel Space from User Space
– Concepts of Pages, Page Faults, and Address Conversion
– Understanding Low Memory and High Memory
– Memory Allocation Mechanisms in Linux (Buddy Allocator)
– Dynamic Memory Allocation in Linux Kernel
– Kernel Stack Management

6. Synchronization in Linux Kernel Programming
– Understanding Concurrency: Preemption, Context Switch, Race Condition, etc.
– Synchronization Techniques: Per CPU Variables, Atomic Variables, Spinlocks, Semaphores, Mutexes, and more.
– Sequence Locks and Read Copy Update (RCU) Techniques

7. Linux Kernel Development and Compilation
– Linux Kernel Development Landscape
– Developer, Maintainer, and Sub-maintainer Roles
– Tips for Submitting Patches
– Various Linux Kernel Trees (Mainline, Stable, Linux-next)
– The Kernel Release Process and its Types
– Building and Modifying the Linux Kernel
– Configuring, Compiling, and Installing Linux Kernel from Source
– Different Configuration Techniques (Menuconfig, Xconfig, Oldconfig, etc.)
– Cross-Compilation of Linux Kernel
– Building Specific Kernel Components

8. Hardware Communication with Linux Device Drivers
– Basics of IO Communication
– IO Mapped IO vs. Memory Mapped IO
– Accessing IO from User Space
– Understanding PCI and SMBIOS
– Dive into Specific Kernel Modules
– IO Mapped IO Drivers (Speaker, RTC, Keyboard)
– Memory Mapped IO Drivers (Hardware Random Generator, GPIO, UART)

9. Interrupts and Bottom Halves in Linux Kernel
– Interrupts, Exceptions, and Their Types
– Hardware Interrupt Controllers: PIC, IO APIC, Local APIC
– The Process of Interrupt Handling in the Kernel
– Linux Driver Interrupts (Keyboard, Mouse, Ethernet)
– Delving into Keylogger Creation in the Kernel
– Differentiating Between Top and Bottom Halves (Threaded IRQs, Softirqs, Tasklets, Workqueues)

10. Deep Dive into System Calls
– The Nitty-Gritty of Inline Assembly
– Basics and Types of Inline Assembly
– Use Cases in the Linux Kernel (Interrupts, Atomic Operations, I/O Ports, etc.)
– System Calls in Linux
– Introduction and Mechanisms of User-to-Kernel Space Switching
– The Process of Adding a New System Call
– Interacting with Kernel Symbol Tables
– Advanced Kernel Modules: Overwriting Symbol Tables, Sniffing System Call Parameters, etc.

10. Timing Subsystem:
– Programming timing in user space
– Timing Hardware
– Jiffies
– Low resolution & High resolution timers
– Timing System calls: ctime, gettimeofday, clock_gettime, clock_settime, clock_getres, times, getrusage
– Setting time from userspace
– How to measure time for a particular instruction
– Hardware Devices used in timing measurement: RTC, TSC, Programmable Interval Timer, APIC, High Precision Event Timer

11. Embedded Linux using Yocto (Part 1):
– Yocto Project Terminology: poky, bitbake, oe-core, metadata, recipe, classes, configuration, layers, image, and packages
– Setting up a build environment for Yocto development
– Building and running Yocto images on various platforms including QEMU, Raspberry Pi3, and Beagle Bone Black
– Yocto Project Releases: Choosing the right one
– Booting Process in popular boards

12. Embedded Linux using Yocto (Part 2):
– Understanding bitbake operators
– Creating and customizing layers and images
– Introduction to image variables and features
– Basics of Yocto recipes
– Logging functions in Yocto

13. Embedded Linux using Yocto (Part 3):
– Understand FILES and PACKAGES variables
– Creating custom PACKAGES
– Writing recipes for static and dynamic libraries
– Build time vs. Run time dependencies: RDEPENDS vs. DEPENDS
– Recipes for Autotools and CMake
– Devshell
– Customizing the boot splash screen

14. Embedded Linux using Yocto (Part 4):
– Understanding the internals of the shared state cache
– Utilizing commands like bitbake-dumpsig and bitbake-diffsigs
– Incremental vs. clean builds
– Kernel development in Yocto: source, configuration, patches
– Yocto Linux Kernel Recipes and customizations
– Understanding package groups and their recipes
– Writing recipes for out-of-tree modules

15. Linux Kernel Testing:
– Introduction to Linux Kernel testing
– Tools for testing the Linux Kernel: Linux Test Project (LTP) & LTP-DDT

16. Debugging Linux Kernel (Part 1):
– Introduction to debugging techniques
– Learning about ftrace, the official Linux Kernel tracer
– Debugging use cases: Analyzing latencies, tracing context switches, observing kernel flow, etc.

17. Debugging Linux Kernel (Part 2):
– Debugging the Linux Kernel using KGDB
– KGDB setup and use on platforms like Raspberry Pi3
– Remote debugging with KGDB
– Debugging Linux Kernel Modules (In-Tree, out-of-tree)
– Use of GDB Scripts present in the Linux Kernel


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