Nathan Chancellor

March 2026 ClangBuiltLinux Work

Tue, 31 Mar 2026 22:30:00 +0100

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

February 2026 ClangBuiltLinux Work

Fri, 27 Feb 2026 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

January 2026 ClangBuiltLinux Work

Fri, 30 Jan 2026 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

December 2025 ClangBuiltLinux Work

Tue, 30 Dec 2025 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Stable backports and fixes: It is important to make sure that the stable trees are as free from issues as possible, as those are the trees that devices and users use; for example, Android and Chrome OS regularly merge from stable, so if there is a problem that will impact those trees that we fixed in mainline, it should be backported.

November 2025 ClangBuiltLinux Work

Fri, 28 Nov 2025 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

October 2025 ClangBuiltLinux Work

Fri, 31 Oct 2025 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

September 2025 ClangBuiltLinux Work

Tue, 30 Sep 2025 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

August 2025 ClangBuiltLinux Work

Fri, 29 Aug 2025 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

July 2025 ClangBuiltLinux Work

Thu, 31 Jul 2025 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

June 2025 ClangBuiltLinux Work

Mon, 30 Jun 2025 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

May 2025 ClangBuiltLinux Work

Fri, 30 May 2025 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

April 2025 ClangBuiltLinux Work

Wed, 30 Apr 2025 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

March 2025 ClangBuiltLinux Work

Mon, 31 Mar 2025 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

February 2025 ClangBuiltLinux Work

Fri, 28 Feb 2025 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

January 2025 ClangBuiltLinux Work

Fri, 31 Jan 2025 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Miscellaneous fixes and improvements: These are fixes and improvements that don’t fit into a particular category but are important to ClangBuiltLinux.
- GCC 15 fixes: While it may seem like these are not important for a Clang project, the problem resolved by the changes could impact Clang should the developers decide to change the default C standard dialect to C23 like GCC did.

December 2024 ClangBuiltLinux Work

Tue, 31 Dec 2024 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

November 2024 ClangBuiltLinux Work

Fri, 29 Nov 2024 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

October 2024 ClangBuiltLinux Work

Thu, 31 Oct 2024 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Downstream fixes: These are fixes and improvements that occur in a downstream Linux tree, such as Android or ChromeOS, which our continuous integration regularly tests.
- ANDROID: GKI: Put vendor_data_pad behind CONFIG_GKI_DYNAMIC_TASK_STRUCT_SIZE
Miscellaneous fixes and improvements: These are fixes and improvements that don’t fit into a particular category but are important to ClangBuiltLinux.

September 2024 ClangBuiltLinux Work

Mon, 30 Sep 2024 15:15:00 +0100

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

August 2024 ClangBuiltLinux Work

Fri, 30 Aug 2024 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Miscellaneous fixes and improvements: These are fixes and improvements that don’t fit into a particular category but are important to ClangBuiltLinux.
- hexagon: Disable constant extender optimization for LLVM prior to 19.1.0 (v1)
- ACPI: platform-profile: Fix CFI violation when accessing sysfs files (v1)
Warning fixes: These are patches to fix various warnings that appear with LLVM. I used to go into detail about the different warnings and what they mean, but the important takeaway for this section is that the kernel should build warning free, as all developers should be using CONFIG_WERROR, which will turn these all into failures. Maybe these should be in the build failures section…

July 2024 ClangBuiltLinux Work

Wed, 31 Jul 2024 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

June 2024 ClangBuiltLinux Work

Fri, 28 Jun 2024 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

May 2024 ClangBuiltLinux Work

Fri, 31 May 2024 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

April 2024 ClangBuiltLinux Work

Tue, 30 Apr 2024 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

March 2024 ClangBuiltLinux Work

Fri, 29 Mar 2024 14:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

February 2024 ClangBuiltLinux Work

Thu, 29 Feb 2024 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

January 2024 ClangBuiltLinux Work

Wed, 31 Jan 2024 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

2023 ClangBuiltLinux Retrospective

Thu, 28 Dec 2023 12:00:00 -0700

Just like I did last year, I want to do a yearly report/retrospective for 2023 to look at what I (and the whole ClangBuiltLinux team in some cases) accomplished. I do monthly reports but looking at a high level across the year helps put things into perspective and drive improvements going into the new year.

Linux kernel

This year, I had 129 commits accepted into maintainer trees (not all will be merged into mainline in 2023 but they were written and added in maintainer trees in 2023). They can be viewed on the web or by running the following command in an up-to-date Linux repository locally:

December 2023 ClangBuiltLinux Work

Thu, 28 Dec 2023 11:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Miscellaneous fixes and improvements: These are fixes and improvements that don’t fit into a particular category but are important to ClangBuiltLinux.
- RISC-V: Disable DWARF5 with known broken LLVM versions (v2)
Stable backports and fixes: It is important to make sure that the stable trees are as free from issues as possible, as those are the trees that devices and users use; for example, Android and Chrome OS regularly merge from stable, so if there is a problem that will impact those trees that we fixed in mainline, it should be backported.

November 2023 ClangBuiltLinux Work

Thu, 30 Nov 2023 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

October 2023 ClangBuiltLinux Work

Tue, 31 Oct 2023 16:15:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

September 2023 ClangBuiltLinux Work

Fri, 29 Sep 2023 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

August 2023 ClangBuiltLinux Work

Thu, 31 Aug 2023 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

July 2023 ClangBuiltLinux Work

Mon, 31 Jul 2023 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

June 2023 ClangBuiltLinux Work

Fri, 30 Jun 2023 13:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

May 2023 ClangBuiltLinux Work

Wed, 31 May 2023 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Warning fixes: These are patches to fix various warnings that appear with LLVM. I used to go into detail about the different warnings and what they mean, but the important takeaway for this section is that the kernel should build warning free, as all developers should be using CONFIG_WERROR, which will turn these all into failures. Maybe these should be in the build failures section…

April 2023 ClangBuiltLinux Work

Fri, 28 Apr 2023 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

March 2023 ClangBuiltLinux Work

Fri, 31 Mar 2023 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

February 2023 ClangBuiltLinux Work

Tue, 28 Feb 2023 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Downstream fixes: These are fixes and improvements that occur in a downstream Linux tree, such as Android or ChromeOS, which our continuous integration regularly tests.
- ANDROID: GKI: Fix copying of protected_exports
Miscellaneous fixes and improvements: These are fixes and improvements that don’t fit into a particular category but are important to ClangBuiltLinux.

January 2023 ClangBuiltLinux Work

Tue, 31 Jan 2023 17:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Downstream fixes: These are fixes and improvements that occur in a downstream Linux tree, such as Android or ChromeOS, which our continuous integration regularly tests.
- ANDROID: fuse: Restore upstream type of bitfields in fuse_args
Miscellaneous fixes: These are fixes and improvements that don’t fit into a particular category but are important to ClangBuiltLinux.

2022 ClangBuiltLinux Retrospective

Fri, 30 Dec 2022 11:00:00 -0700

I have been contracting for the Linux Foundation for two years now, going onto the third, and it dawned on me that I have never done a retrospective or yearly report. This is useful for looking back on the year’s worth of accomplishments, both to understand how much I have evolved and to look for areas that I would like to improve upon going forward. I have struggled with imposter syndrome for as long as I have been involved with the kernel community, so looking back to give credit where credit is due for particular solutions is a good way to try and combat that.

December 2022 ClangBuiltLinux Work

Fri, 30 Dec 2022 11:00:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Miscellaneous fixes: These are fixes and improvements that don’t fit into a particular category but are important to ClangBuiltLinux.
- Fix lack of section mismatch warnings with LTO (v2, v3)
- security: Restrict CONFIG_ZERO_CALL_USED_REGS to gcc or clang > 15.0.6 (v1)
Warning fixes: These are patches to fix various warnings that appear with LLVM (or in the case of the first one, with GCC as the result of a patch series for ClangBuiltLinux). I used to go into detail about the different warnings and what they mean, but the important takeaway for this section is that the kernel should build warning free, as all developers should be using CONFIG_WERROR, which will turn these all into failures. Maybe these should be in the build failures section…

November 2022 ClangBuiltLinux Work

Wed, 30 Nov 2022 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

October 2022 ClangBuiltLinux Work

Mon, 31 Oct 2022 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

September 2022 ClangBuiltLinux Work

Thu, 29 Sep 2022 15:55:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

August 2022 ClangBuiltLinux Work

Wed, 31 Aug 2022 16:15:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Miscellaneous fixes and improvements: These are fixes and improvements that don’t fit into a particular category but are important to ClangBuiltLinux.
- scripts/Makefile.extrawarn: Do not disable clang's -Wformat-zero-length (v1)
- x86/build: Move '-mindirect-branch-cs-prefix' out of GCC-only block (v1)
Stable backport requests: It is important to make sure that the stable trees are as free from issues as possible, as those are the trees that devices and users use; for example, Android and Chrome OS regularly merge from stable, so if there is a problem that will impact those trees that we fixed in mainline, it should be backported.

July 2022 ClangBuiltLinux Work

Fri, 29 Jul 2022 16:00:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

June 2022 ClangBuiltLinux Work

Thu, 30 Jun 2022 16:25:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Android changes: Android is one of the largest downstream consumers of our work. Our continuous integeration tests the Android trees with newer versions of LLVM to help catch any issues that will impact Android once they upgrade their version of LLVM, which can lag behind at times.

May 2022 ClangBuiltLinux Work

Tue, 31 May 2022 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

Setting up a self-hosted GitHub Actions runner in a Fedora virtual machine using libvirt

Fri, 27 May 2022 09:21:35 -0700

Recently, I started exploring setting up a self-hosted GitHub Actions runner for the work-in-progress LLVM builds that ClangBuiltLinux is looking to distribute on kernel.org, as GitHub Actions hosted runners are pretty underwhelming in terms of performance and we want to soup these builds up with Profile Guided Optimization. Additionallly, GitHub Actions does not have a hosted arm64 Linux option, which is becoming increasingly important with chips such as Apple’s M1 getting strong mainline Linux support.

April 2022 ClangBuiltLinux Work

Fri, 29 Apr 2022 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build failures: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

About

Fri, 29 Apr 2022 10:15:00 -0700

I am a Linux kernel and LLVM hacker, currently employed as an independent contractor through The Linux Foundation to maintain ClangBuiltLinux. I am interested in performance analysis, compilers, security, and operating systems. I completed my Bachelor of Science in Information Technology at Grand Canyon University in 2022.

Below are links to some of my open source contributions. If you have any questions about them, feel free to reach out to me with the links on the home page.

Bisecting a Linux Kernel boot failure due to changed compiler flags

Thu, 28 Apr 2022 14:21:18 -0700

Occasionally, compiling the Linux kernel with a new compiler flag will result in a boot failure. If you are lucky, there will be some output to the serial console but that may not happen if the issue happens in early boot code before the serial driver has loaded. When this happens, it usually requires building part of the kernel without the compiler flag (or the “negative” version of it) to try and figure out the exact translation unit and function that causes the problem. I’ll go over this process at a high level to help others who might encounter this same issue.

Package a standalone Linux kernel using the Arch Linux Build System

Wed, 27 Apr 2022 14:06:01 -0700

As a Linux kernel developer, I will often need to build and boot new kernels to hunt down issues or test new functionality for regressions. While it is possible to manually install these kernels on machines, it is easiest to use the distribution’s package manager, as the kernel does not need to be built on the machine it is being installed on. With .deb and .rpm-based systems, it is easy to build a kernel package within the kernel source itself, using the bindeb-pkg and binrpm-pkg targets respectively. However, for Arch Linux, my distribution of choice, that is not so simple. Furthermore, when doing certain types of development, such as bisecting an issue, it is more convenient to do all the building in an actual source tree, rather than one that is managed by the Arch Build System. The following process might not be the most efficient or optimal way to do this process (the Arch wiki has a whole article about doing a git bisect with a PKGBUILD) but it works for me :)

March 2022 ClangBuiltLinux Work

Thu, 31 Mar 2022 16:30:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Boot fixes: These patches fix boot failures that we have seen in testing. In this case, it is a User Mode Linux fix, which we are looking to enable in our continuous integration setup, as it is useful for quick testing.

February 2022 ClangBuiltLinux Work

Mon, 28 Feb 2022 00:17:30 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Miscellaneous improvements: These are series or patches that do not really fit into any of the other categories I typically use with my reports.
- Allow CONFIG_DEBUG_INFO_DWARF5=y + CONFIG_DEBUG_INFO_BTF=y (v1)
- tools/resolve_btfids: Do not print any commands when building silently (v1)
-Wenum-conversion: This warning occurs when one enumerated type is implicitly converted to another enumerated type, which is typically a bug, although it might not actually be a problem in practice if the used enum has the same value as the intended enum (which is the case here). It is still good to get it corrected, as the enums might not stay in sync.

January 2022 ClangBuiltLinux Work

Mon, 31 Jan 2022 00:18:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Stable patches: The stable trees are the trees that most users consume so keeping them building and as warning and issue free as reasonable is important.
- [PATCH 5.4] Input: touchscreen - Fix backport of a02dcde595f7cbd240ccd64de96034ad91cffc40 (v1)
- [PATCH RFC 4.9 0/5] Fix booting arm64 big endian with QEMU 5.0.0+ (v1)
- [PATCH 4.4,4.9] power: reset: ltc2952: Fix use of floating point literals (v1)
- Patches for clang and CONFIG_WERROR (arm64/x86_64)
-Wpointer-bool-conversion: This warning is usually harmless, as it is typically just a developer checking if an array in the middle of a structure is NULL, which is not possible if the structure is not NULL, which would likely cause issues further up a call chain. In this one case, the fix was just to remove the check.

December 2021 ClangBuiltLinux Work

Fri, 31 Dec 2021 12:00:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Android patches: Android is one of the biggest downstream consumers of our work. Making sure that it stays working is incredibly important so that it can reach real users.
- Revert "ANDROID: disable INFINIBAND_QIB from allmodconfig build"
- ANDROID: allmodconfig: Re-enable TEST_KMOD

November 2021 ClangBuiltLinux Work

Tue, 30 Nov 2021 16:23:00 -0700

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

Build errors: These are hard errors that appear for one reason or another. The first two are from a recent change in LLVM to avoid crashing the compiler (see the commit message for more details, I learned floating point literals exist in C). The third series is a resend that fixes ARCH=hexagon allmodconfig, which is an important target for us because ARCH=hexagon requires LLVM. Lastly, the final series fixes a generic issue uncovered by the kernel test robot with an ARCH=hexagon randconfig.

Reducing an LTO Linux kernel bug with cvise

Mon, 29 Nov 2021 10:07:16 -0700

My co-maintainer Nick Desaulniers wrote a great post about taking a several thousand line C file that exposed a compiler bug down to 12 lines with creduce. I thought I would do the same thing with a bug that only happens with link time optimization (LTO) in the Linux kernel, which is a bit of a different beast. Hopefully this post can help others reduce their own bugs and think about the best way to triage a bug.

October 2021 ClangBuiltLinux Work

Fri, 29 Oct 2021 14:10:00 -0700

This was a bit of a shorter month for me, as I took some vacation at the beginning of the month to recouperate and meet half of my girlfriend’s extended family and friends for the first time. Thankfully, the rest of the ClangBuiltLinux team was able to keep everything churning along in my absence and I was able to be super productive the rest of the month once I returned.

September 2021 ClangBuiltLinux Work

Thu, 30 Sep 2021 10:00:00 -0700

Linux kernel patches

tools: compiler-gcc.h: Guard error attribute use with __has_attribute (v1): The minimum version of GCC was raised to 5.1, which helped simplify a lot of code but caused issues for older versions of clang. This helps resolve it.
Harden clang against unknown flag options (v2): A follow up.
ptp: ocp: Avoid operator precedence warning in ptp_ocp_summary_show() (v1, v2): An interesting warning around operator precedence, which will not be an issue in practice but now that Linus has decreed that warnings are unacceptable, it is important to clean them up!

August 2021 ClangBuiltLinux Work

Tue, 31 Aug 2021 20:38:00 -0700

Linux kernel patches

[PATCH] dmaengine: idxd: Remove unused status variable in irq_process_work_list(): Not a clang specific warning but it impacts builds where I use -Werror, as kernel builds should be as warning clean as possible.
[PATCH] ASoC: Intel: boards: Fix CONFIG_SND_SOC_SDW_MOCKUP select: Not a clang specific warning but Kconfig warnings such as this can potentially be build errors later due to incorrect dependency selection so it is important to fix them when they pop up.

July 2021 ClangBuiltLinux Work

Sun, 01 Aug 2021 00:00:00 -0700

Linux kernel patches

[PATCH] Hexagon: Export raw I/O routines for modules: Hexagon is a digital signal processor architecture by Qualcomm, which is a little special in terms of the Linux kernel because it is the only architecture that does not have a GCC backend so LLVM has to be used to build it, meaning that it is important to keep it building. This patch fixes an issue with allmodconfig, which enables us to build a wide variety of code and verify the compiler is able to handle all of it.

June 2021 ClangBuiltLinux Work

Thu, 01 Jul 2021 13:48:16 -0700

Linux kernel patches

ANDROID: sched: Gate sched_stat tracepoint exports on CONFIG_SCHEDSTATS: One of those instances where a tangential change in the Android trees broke our continuous integration. Our CI tests some 32-bit ARM configurations because certain Android OEMs care about them but these configs are not tested by the actual Android team, meaning we find breakage that they do not.
[PATCH net-next] net: ks8851: Make ks8851_read_selftest() return void: clang implemented GCC’s -Wunused-but-set-variable and this instance was found by Intel’s kernel test robot. Rather simple fix but it is important to fix warnings as they crop up so that the build stays as clean as possible so that the real issues are easily visible.

May 2021 ClangBuiltLinux Work

Tue, 01 Jun 2021 08:29:00 -0700

This month felt longer than others but I feel like that was because I was a lot more spread out in the work that I was doing. Let’s dive in, shall we?

Linux kernel patches / backports

[PATCH] fbmem: Correct position of '__maybe_unused' in proc_fb_seq_ops: A common mistake people make is splitting “struct ” with an attribute, in this case “__maybe_unused”, which clang warns about while GCC does not. This causes a warning in all of our builds. Unfortunately, this patch did not actually make it into mainline because Linus fixed it himself.

April 2021 ClangBuiltLinux Work

Fri, 30 Apr 2021 21:14:13 -0700

Another month down! Feels like I just wrote the March 2021 post… but I suppose that is what happens when your project moves super quickly :)

Linux kernel patches

[PATCH] ACPI / CPPC: Replace cppc_attr with kobj_attribute: I discovered this issue as part of my testing of Sami Tolvanen’s Control Flow Integrity series (more on that below). There are probably many more of these lurking because this pattern is hard to spot without runtime testing. As I have time amongst all of the other issues and such, I will be testing the x86 variant of CFI on several different servers, trying to flush out all of the different issues there.

March 2021 ClangBuiltLinux Work

Thu, 01 Apr 2021 10:25:53 -0700

Another month, another post about the work that I have done as a kernel/compiler developer! One of the highlights this month is that I got LLVM commit access so I can merge my own patches into LLVM, which I did twice so far.

Linux kernel patches

powerpc/fadump: Mark fadump_calculate_reserve_size as __init: LLVM 13 switched over to the New Pass Manager (NPM), which has impacted some inlining decisions, which in turn exposed some bugs in section annotations. The kernel places certain functions and variables into specific sections that are discarded and freed after init. If a non-init function calls an init function, that is technically a use-after-free so the kernel warns when this happens. In this particular case, identical_pvr_fixup() was not marked as __init and it was not getting inlined so the calls to identify_cpu() and of_get_flat_dt_prop() resulting in the modpost warnings. In practice, this is not an issue because identical_pvr_fixup() is only called from __init context but it is important to get these things right so that real warnings can easily be caught.

February 2021 ClangBuiltLinux Work

Sun, 28 Feb 2021 00:01:20 -0700

As some of you may or may not know by now, I am now employed by the Linux Foundation to help improve Linux security. The primary way that I am doing that is through the work I do for ClangBuiltLinux, of which I am an official maintainer.

Linux kernel patches

First and foremost, I am a Linux kernel developer, meaning that I love sending kernel patches. Getting familiar with git send-email and the standard Linux kernel workflow can be difficult but now that I am used to it, I find other things cumbersome.

Working with git bisect

Fri, 17 Apr 2020 15:23:45 -0700

Before Google+ shut down, I had a post on there giving a brief overview of git bisect, which a lot of people found useful. Unfortunately, I forgot to save it and move it somewhere else before the shutdown deadline. As a result, I am going to redo it here and spice it up a bit.

One caveat before I start: there is great official documentation for git bisect, from which I have taken quite a bit of information. If I say something that contradicts what the documentation says, assume the documentation is right.

The art of git revert

Wed, 15 Apr 2020 15:11:58 -0700

I have always loved reading good commit messages and I have tried myself to write good commit messages to inspire others to do the same. I see good commit messages as important for two reasons: it allows people who work on a project afterwards to understand the context behind a change (so that you don’t have a denvercoder9 situation) and it allows other people to get familiar with your project by fully understanding the why behind a change. I learned a lot about the Linux kernel purely through reading the commit messages in certain subsystems.

Creating WSL 2 distributions from LXC images

Wed, 15 Apr 2020 12:40:20 -0700

I have been a big fan of Windows Subsystem for Linux 2 as I need Windows for school but I am so used to the command line for remoting into my server and automating various tasks locally. For those of you who do not know, WSL 2 uses a Linux kernel under the hood (which I customize here) and all of the various distributions that you can run are basically containers on top of it.

Building and using Cuttlefish

Fri, 31 Jan 2020 18:52:00 -0700

Recently, I stumbled upon a talk that Alistair Delva, a Google engineer, gave at the 2018 Linux Plumbers Conference around Cuttlefish, an Android Virtual Device (AVD) that is used to validate the Android platform virtually (i.e. without a separate device). This is something that is really cool because it makes it easy to follow along with upstream Android development and see what changes they are making under the hood, all from adb shell. Cuttlefish boots in around 20 seconds on my machine and swapping out kernels is as simple as adding two command flags which I will go over later. If you are running Cuttlefish locally, you can even view it with TightVNC.

Building the WSL 2 kernel with Clang

Tue, 17 Dec 2019 13:53:23 -0700

Recently, I built a computer for school that I installed Windows 10 Pro on (link to the current specs if you are curious). I was a little bummed about leaving Chrome OS because I was going to lose my local Linux development environment; however, Windows Subsystem for Linux is a thing and it has gotten even better with WSL 2, as it is actually running a Linux kernel so there is full Linux compatibility going forward. I also learned that it is possible to replace the Linux kernel that Microsoft ships with your own. This is a mini guide for what I uncovered because there is not a ton of information around for how to do this.

Downloads

Tue, 02 Jul 2019 00:00:00 +0000

I used to host files on this website but I have offloaded them to other services.

Flash Kernel downloads can be found in their individual repos:

Note, these are all unmaintained right now so I wouldn’t recommend running them in their current form but it’s your device.

TWRP downloads can be found in the threads that referenced them:

Anything else wasn’t important enough to mention here. I’ve updated the links in all the places I could. Contact me using the info on the front page if you need something that isn’t here.