Kconfig is a language that describes configuration options for the Linux Kernel. The syntax looks like this:

# https://github.com/torvalds/linux/blob/master/arch/riscv/Kconfig#L771
config EFI
	bool "UEFI runtime support"
	depends on MMU
	default y
	select EFI_STUB
	help
	  This option provides support for runtime services provided
	  by UEFI firmware.

• The file starts with a config entry: We define a config named EFI. The next lines are the attributes of this entry.
• EFI is a boolean config.
• EFI depends on the config MMU.
• Its default value is y.
• If EFI is equals to true then it enables EFI_STUB.
• The help attribute defines a help text for the end user.

There are plenty of other keywords in the Kconfig language, check out the official documentation for more details.

Features

• This is a parser, there is no semantic analysis in this library.
• This library only supports UTF-8 encoded files.
• List of supported entries can be found here.
• List of supported attributes can be found here.
• When source is met, it reads and parses the specified configuration file.
• This library uses clone() a lot. Do not expect amazing performances.
• This parser has been tested on the Linux kernel repository from 2.6.11 to 6.4.9 (3733 versions).
• There are cargo features for glob-wildcard (used by coreboot, for example) and kconfiglib compatibility. Enabling them adds support for some non-standard entries and attributes used by these projects.

Getting started

cargo add nom-kconfig

use nom_kconfig::{parse_kconfig, KconfigInput};
use std::path::PathBuf;
use nom_kconfig::{KconfigFile};
use std::collections::HashMap;

// curl https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.4.9.tar.xz | tar -xJ -C /tmp/
fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut variables = HashMap::new();
    variables.insert("SRCARCH", "x86");
    let linux_dir = PathBuf::from("/tmp/linux-6.4.9");

    let kconfig_file = KconfigFile::new_with_vars(
        linux_dir.clone(),
        linux_dir.join("Kconfig"),
        &variables,
        &Default::default(),
    );
    let input = kconfig_file.read_to_string()?;
    let kconfig = parse_kconfig(KconfigInput::new_extra(&input, kconfig_file));
    println!("{:?}", kconfig);
    Ok(())
}

Resources

• https://www.kernel.org/doc/html/next/kbuild/kconfig-language.html
• https://doc.coreboot.org/getting_started/kconfig.html
• https://build2.org/libbuild2-kconfig/doc/build2-kconfig-manual.xhtml#lang