Core Knowledge That Modern Linux Kernel Developer Should Have

Linux Kernel Development Guide: Skills, Tools, and Environments

programming language:

The Linux kernel is mainly written in C language, so proficient in C language (especially C11 and GNU extensions) is the core skill. Some architecture-related code and high-performance drivers may use assembly language (x86, ARM, or RISC-V, depending on the hardware platform). The Rust language is also gaining increasing attention because it provides a safer and more reliable alternative.

Build system and scripts:

Understanding KBuild and Make build systems is crucial for modifying and extending kernel code. Shell scripting skills are also essential for automated repetitive tasks.

Software environment:

Git version control system is an indispensable part of the Linux kernel development process. The Qemu/KVM virtualization platform provides an efficient environment for development and debugging, allowing code testing in virtual machines to avoid frequent restarts of real hardware.

Debugging and performance analysis:

Traditional kernel debugging methods include printing debugging information using the printk function and viewing it through the dmesg command. Modern kernel development widely uses the Ftrace framework for efficient kernel tracking and debugging, as well as perf tools for performance analysis. The eBPF framework provides a revolutionary improvement in kernel observability, allowing user programs to be run inside the kernel and pass information to user space.

Embedded development:

The Linux kernel is widely used in embedded systems. Embedded developers need to be familiar with the Buildroot or Yocto build system, as well as the DTS files (describing hardware components) and the U-boot bootloader. Busybox is a commonly used lightweight user space framework.

Development environment:

Most kernel developers use vim (or other terminal editor), tmux terminal multiplexer, and cscope code cross-reference tools.

Core concept:

Linux kernel development skills are divided into general skills and domain-specific skills.

General skills:

1. Kernel encoding style: Follow the encoding style specifications of the Linux kernel and check the code using scripts/checkpatch.pl script.
2. Kernel encoding mode: Be familiar with the recommended encoding modes of the kernel, such as using goto statements to handle multi-step resource initialization.
3. Kernel internal data structure: Master commonly used kernel data structures, such as linked lists, queues, hash tables, binary trees, red and black trees, etc.
4. Synchronous primitives: Understand and proficient in various synchronization primitives, such as atomic operations, spin locks, semaphores, mutexes, RCUs, etc., to deal with multithreaded concurrency problems.
5. Interrupt processing: Understand the upper and lower half mechanisms of interrupt processing, as well as various delay working mechanisms (task queues, softirqs, taskslets, workqueues, etc.).
6. Memory management: Be familiar with the kernel's memory management mechanism, including kmalloc/kfree and slab allocator.
7. Virtual File System (VFS): Understand the common interface of VFS and its interaction with various file systems.
8. Scheduler: Understand the basic principles of kernel schedulers.
9. System call interface: Understand the system call interface between the kernel and user space.
10. /sys /proc directory: Familiar with the system information and settings under the /sys and /proc directory.
11. Loadable kernel modules: Understand the structure and loading/unloading mechanism of the kernel module, as well as the communication methods with user space (sysfs attributes, MMIO, kernel module parameters, etc.).
12. Udev: Understand the Udev subsystem and device hot-swap event handling.
13. Fault injection framework: used to test exception code paths.
14. Kernel disinfector: (KASAN, KMSAN, etc.) is used to detect memory corruption and other problems.
15. Lock Correctivity Verifier: Used to detect deadlocks and live locks.
16. Kdump/Kexec: used to analyze kernel crashes.

Domain-specific skills: depends on the specific development field (network, storage, virtualization, encryption, embedded, etc.).

User Space Tools:

Kernel developers need to be proficient in using the following user space tools:

• bash (or other shell)
• ssh
• tmux
• minicom (for serial communication for embedded devices)
• vim
• gdb (for debugging kernel errors)

Soft Skills:

• enthusiasm
• patience
• will

Hope this guide can help you better understand Linux kernel development. Remember that continuous learning and practice are the key to becoming a good kernel developer.

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