April 2022 ClangBuiltLinux Work

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 :)...

April 29, 2022 · 6 min · Nathan Chancellor

Bisecting a Linux Kernel boot failure due to changed compiler flags

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....

April 28, 2022 · 7 min · Nathan Chancellor

Package a standalone Linux kernel using the Arch Linux Build System

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....

April 27, 2022 · 5 min · Nathan Chancellor

March 2022 ClangBuiltLinux Work

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....

March 31, 2022 · 6 min · Nathan Chancellor

February 2022 ClangBuiltLinux Work

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)....

February 28, 2022 · 7 min · Nathan Chancellor

January 2022 ClangBuiltLinux Work

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....

January 31, 2022 · 6 min · Nathan Chancellor

December 2021 ClangBuiltLinux Work

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"...

December 31, 2021 · 8 min · Nathan Chancellor

November 2021 ClangBuiltLinux Work

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)....

November 30, 2021 · 7 min · Nathan Chancellor

Reducing an LTO Linux kernel bug with cvise

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....

November 29, 2021 · 19 min · Nathan Chancellor

October 2021 ClangBuiltLinux Work

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....

October 29, 2021 · 7 min · Nathan Chancellor