Stephen's Kernel Tools

This repo contains a few scripts I find useful for kernel hacking.

Installation

I normally have a top-level folder called kernel which I place this repo into. I then have a number of sub-folders:

• src: The Linux Kernel tree.

• useful-configs: A folder for some good kernel configs. For example this includes a really small (but valid) config, a QEMU specific config and an Ubuntu 18.04 like config.

• configs: A folder for all the other configs I use, I usually don't repo this or tie it to a separate private repo.

• debs: A folder of handy output .debs (I almost always work on Debian packages and not RPMs). Again I don't repo this.

build-kernel-debrpm

build-kernel-debrpm is a shell script that builds a kernel debian package or RHEL/CentOS RPM files for installation of a linux kernel. See the notes in the file for more information. Note this script lives in the scripts folder.

An example run of this script that would build a p2pdma enabled kernel based on version 4 of the patchsets would be:

REMOTE=https://github.com/sbates130272/linux-p2pmem \
  REMOTE_BRANCH=pci-p2p-v4 \
  CONFIG=<config-file> \
  ./build-kernel-debrpm

And an example that builds a monolithic kernel based on the default config (with all modules converted to "yes") for v4.14.30 would be:

REMOTE= git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git \
  REMOTE_BRANCH=v4.14.30 \
  MONO=yes \
  ./build-kernel-debrpm

And an example that builds a non-monolithic kernel based on the default config (with all modules converted to "yes") for v4.14.30 for arm64 on a non-arm64 host system would be:

REMOTE= git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git \
  REMOTE_BRANCH=v4.14.30 \
  ARCH=arm64 \
  CROSS_COMPILE=aarch64-linux-gnu- \
  ./build-kernel-debrpm

Note all files associated with the unique generation of this kernel (the .config and the (if present) are included in the output tarball along with a .build-info file that contains the information needed to reproduce the .debs or .rpms.

build-latest-p2pdma-kernel

A helper script around build-kernel-debrpm that should always point to the latest and greatest p2pdma kernel. Run this to generate a p2pdma kernel unless you know what you are doing and want to use build-kernel-debrpm. Only supports x86_64 right now.

Patches

build-latest-p2pdma-kernel uses three patches (located in the patches folder) to address some issues with p2pdma kernels. Namely:

• acs_disable: Add a kernel configuration parameter (acs_disable) that turns off PCIe ACS everywhere. This can be useful for testing p2pdma. To enable this mode add pci=acs_disable to your kernel command line parameters.

• p2pmem-pci: Adds a device driver for p2pmem exposed by a device driver. Based on this repository. We use this to expose p2pmem to userspace applications.

• p2pdma patches: A couple of changes were made in p2pdma.c in the v5.4 kernel that broke out of tree drivers for p2pmem. These patches fix this. They are not needed for pre-v5.4 kernels.

Note that the current version of the patches sub-folder this repository only supports v5.6.x series kernel source due to changes in drivers/pci/probe.c. You will need to generate your own patches to address other kernels. We plan to address this issue soon!

docker

A Dockerfile exists that can generate the enviromnent needed to run build-latest-p2pdma-kernel. This can make the generation of the .deb for this kernel simpler for some users. To generate the kernel Debian packages this way proceed as follows from the top-level folder of this repo. Note that since we always pull from the HEAD of the repository we need to run docker with -no-cache. This slows down the build time but avoids incorrect builds.

cd docker
docker build --no-cache -t kernel-tools:latest .

once the image has run to completion you can obtain the tarball via the following (from either the docker folder or the top-level folder for this repo).

docker create --name kernel-tools kernel-tools:latest
docker cp kernel-tools:/kernel/build-kernel-deb.docker.tar.gz .
docker rm kernel-tools

You can then install the .deb using the same approach as a native build using build-latest-p2pdma-kernel.

arch-tools

The arch-tools sub-folder contains a few useful tools for building Linux kernels and kernel modules for non-amd64 based systems. This includes some platform-specific tools and some generic ISA tools.

One of the most useful of these tools is the build-arm64 script which can build a ARM64 kernel and modules using a cross-compiler approach. You should call this script from the top-level of a kernel source tree. See the header of the script for more information. There is also a build-riscv script which can do something similar for riscv32 and riscv64 ISA.