Kernel Debugging with QEMU - Revision history

Axka: Add link for more info about patching and configuring the kernel

2025-11-05T09:53:53Z

Add link for more info about patching and configuring the kernel

← Older revision		Revision as of 09:53, 5 November 2025
Line 1:		Line 1:
	== Set up the QEMU VM ==		== Set up the QEMU VM ==

	=== With a Nix kernel ===		=== With a Nix-built kernel ===
	Use a NixOS config like ~~this:~~		Use a NixOS config like below. See [[Linux kernel#Custom configuration]] for more information about patching and configuring the kernel's build.

	<syntaxhighlight lang="nix">		<syntaxhighlight lang="nix">

2025-11-05T09:43:26Z

extraStructuredConfig -> structuredExtraConfig

← Older revision		Revision as of 09:43, 5 November 2025
Line 21:		Line 21:
	name = "enable debugging information";		name = "enable debugging information";
	patch = null;		patch = null;
	~~extraStructuredConfig~~ = {		structuredExtraConfig = {
	GDB_SCRIPTS = lib.kernel.yes;		GDB_SCRIPTS = lib.kernel.yes;
	DEBUG_INFO = lib.kernel.yes;		DEBUG_INFO = lib.kernel.yes;

2025-11-05T09:40:34Z

Use extraStructuredConfig instead of extraConfig in boot.kernelPatches as the latter is deprecated

← Older revision		Revision as of 09:40, 5 November 2025
Line 21:		Line 21:
	name = "enable debugging information";		name = "enable debugging information";
	patch = null;		patch = null;
	~~extraConfig~~ = ''		extraStructuredConfig = {
	GDB_SCRIPTS y		GDB_SCRIPTS = lib.kernel.yes;
	DEBUG_INFO y		DEBUG_INFO = lib.kernel.yes;
	KALLSYMS y		KALLSYMS = lib.kernel.yes;
	'';		};
	}		}
	{		{

2025-08-15T14:35:19Z

link to PR that fixes building the gdb integration script

← Older revision		Revision as of 14:35, 15 August 2025
Line 56:		Line 56:

	==== Loading module symbols and accurate kernel sources ====		==== Loading module symbols and accurate kernel sources ====

			Make sure you're using a branch of nixpkgs that has https://github.com/NixOS/nixpkgs/pull/432405 applied.

	This generates a script that starts gdb with module symbols and kernel sources attached:		This generates a script that starts gdb with module symbols and kernel sources attached:

2025-08-12T09:22:05Z

document how to debug a nix-built kernel including modules and sources

2025-05-22T10:41:24Z

Increase image size as 1024 is no longer sufficient

← Older revision		Revision as of 10:41, 22 May 2025
Line 78:		Line 78:
	Save this as <code>nixos-image.nix</code>:		Save this as <code>nixos-image.nix</code>:

	<syntaxhighlight lang="nix">		<syntaxhighlight lang="nix">{ pkgs ? import <nixpkgs> {} }:
	{ pkgs ? import <nixpkgs> {} }:
	import (pkgs.path + "/nixos/lib/make-disk-image.nix") {		import (pkgs.path + "/nixos/lib/make-disk-image.nix") {
	config = (import (pkgs.path + "/nixos/lib/eval-config.nix") {		config = (import (pkgs.path + "/nixos/lib/eval-config.nix") {
Line 89:		Line 88:
	inherit pkgs;		inherit pkgs;
	inherit (pkgs) lib;		inherit (pkgs) lib;
	diskSize = ~~1024~~;		diskSize = 2048;
	partitionTableType = "none";		partitionTableType = "none";
	# for a different format		# for a different format
	format = "qcow2";		format = "qcow2";
	}		}</syntaxhighlight>
	</syntaxhighlight>

	Than follows the nixos configuration in a file named <code>nixos-config.nix</code>		Than follows the nixos configuration in a file named <code>nixos-config.nix</code>

2024-04-19T17:32:31Z

← Older revision		Revision as of 17:32, 19 April 2024
Line 226:		Line 226:

	This integration also allows to use incremental kernel builds for rapid development. Checkout the commit message for details.		This integration also allows to use incremental kernel builds for rapid development. Checkout the commit message for details.

			[[Category:Virtualization]]

2023-03-20T09:19:33Z

adding ktest

← Older revision		Revision as of 09:19, 20 March 2023
Line 218:		Line 218:
	systemd.services."serial-getty@ttyS0".enable = true;		systemd.services."serial-getty@ttyS0".enable = true;
	</syntaxhighlight>		</syntaxhighlight>

			== Using ktest with NixOS ==

			Yellow onion has integrated nixos vms into ktest:

			https://github.com/YellowOnion/ktest/commit/73fadcff949236927133141fcba4bfd76df632e7

			This integration also allows to use incremental kernel builds for rapid development. Checkout the commit message for details.

2022-12-25T20:20:38Z

← Older revision		Revision as of 20:20, 25 December 2022
Line 209:		Line 209:
	</syntaxhighlight>		</syntaxhighlight>
	press <code>F8</code> and search for your driver, and check if it is set to "Module" with <code><M></code>. After compilation copy the driver.ko into the mounted <code>qemu-image.img</code>. Unmount start the kernel and break at the <code>load_module</code> function and <code>insmod driver.ko</code>. Happy hacking!		press <code>F8</code> and search for your driver, and check if it is set to "Module" with <code><M></code>. After compilation copy the driver.ko into the mounted <code>qemu-image.img</code>. Unmount start the kernel and break at the <code>load_module</code> function and <code>insmod driver.ko</code>. Happy hacking!

			== Bugs ==

			1. With the nixos-config provided above, the console does not work properly. boot.isContainer = true; implies console.enable = false; that disables console. The following can be used as a workaround.

			<syntaxhighlight lang="nix">
			console.enable = true;
			systemd.services."serial-getty@ttyS0".enable = true;
			</syntaxhighlight>

2021-09-13T20:53:53Z

Generate a config for KVM

← Older revision		Revision as of 20:53, 13 September 2021
Line 61:		Line 61:
	<syntaxhighlight lang="console">		<syntaxhighlight lang="console">
	$ cd linux		$ cd linux
	$ make mrproper # Clears all artifacts, do this especially if you significant old version		$ make mrproper # Clears all artifacts, do this especially if you upgrade from a significant old version
	$ nix-shell shell.nix		$ nix-shell shell.nix
	$ make defconfig kvm_guest.config		$ make defconfig kvm_guest.config