How to set up a development environment for Linux kernel with LSP support

We are going to set up a development environment for Linux kernel with LSP support. This will help you to write, navigate, and understand the kernel code more effectively. This is a follow-up to the contribute-kernel post where we set up a basic development environment for Linux kernel and talk about the process of contributing to the upstream.

Pre-requisites

We should first install clangd, which is a language server for C/C++ languages. It provides features like code completion, go to definition, find references, and more.

It can be easily installed on most Linux distributions. For example, on Ubuntu, you can install it using:

sudo apt install clangd

Generating compile_commands.json

This is the most important step in setting up the LSP support for the Linux kernel. The clangd server uses a file called compile_commands.json to understand how to compile the code. This file contains the compilation commands for each source file in the project.

For out-of-tree kernel modules

If we are developing out-of-tree kernel modules, we should use bear to help us generate this file. bear is a tool that intercepts the compilation commands and generates the compile_commands.json file.

We can install bear using the package manager. For example, on Ubuntu, we can install it using:

sudo apt install bear -y

Then we can use bear to generate the compile_commands.json file by running the following command in the kernel source directory:

make clean
bear --append make

For in-tree kernel development

For in-tree kernel development, we can use the provided script scripts/clang-tools/gen_compile_commands.py to generate the compile_commands.json file. This script will generate the file based on the current kernel configuration.

We can run the following command in the kernel source directory after compilation:

python3 scripts/clang-tools/gen_compile_commands.py