| Message ID | 20240125-bump-min-llvm-ver-to-13-0-1-v1-0-f5ff9bda41c5@kernel.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | Bump the minimum supported version of LLVM to 13.0.1 | expand |
On Thu, Jan 25, 2024 at 03:55:06PM -0700, Nathan Chancellor wrote: > Hi all, > > This series bumps the minimum supported version of LLVM for building the > kernel to 13.0.1. The first patch does the bump and all subsequent > patches clean up all the various workarounds and checks for earlier > versions. > > Quoting the first patch's commit message for those that were only on CC > for the clean ups: > > When __builtin_mul_overflow() has arguments that differ in terms of > signedness and width, LLVM may generate a libcall to __muloti4 because > it performs the checks in terms of 65-bit multiplication. This issue > becomes harder to hit (but still possible) after LLVM 12.0.0, which > includes a special case for matching widths but different signs. > > To gain access to this special case, which the kernel can take advantage > of when calls to __muloti4 appear, bump the minimum supported version of > LLVM for building the kernel to 13.0.1. 13.0.1 was chosen because there > is minimal impact to distribution support while allowing a few more > workarounds to be dropped in the kernel source than if 12.0.0 were > chosen. Looking at container images of up to date distribution versions: > > archlinux:latest clang version 16.0.6 > debian:oldoldstable-slim clang version 7.0.1-8+deb10u2 (tags/RELEASE_701/final) > debian:oldstable-slim Debian clang version 11.0.1-2 > debian:stable-slim Debian clang version 14.0.6 > debian:testing-slim Debian clang version 16.0.6 (19) > debian:unstable-slim Debian clang version 16.0.6 (19) > fedora:38 clang version 16.0.6 (Fedora 16.0.6-3.fc38) > fedora:latest clang version 17.0.6 (Fedora 17.0.6-1.fc39) > fedora:rawhide clang version 17.0.6 (Fedora 17.0.6-1.fc40) > opensuse/leap:latest clang version 15.0.7 > opensuse/tumbleweed:latest clang version 17.0.6 > ubuntu:focal clang version 10.0.0-4ubuntu1 > ubuntu:latest Ubuntu clang version 14.0.0-1ubuntu1.1 > ubuntu:rolling Ubuntu clang version 16.0.6 (15) > ubuntu:devel Ubuntu clang version 17.0.6 (3) > > The only distribution that gets left behind is Debian Bullseye, as the > default version is 11.0.1; other distributions either have a newer > version than 13.0.1 or one older than the current minimum of 11.0.0. > Debian has easy access to more recent LLVM versions through > apt.llvm.org, so this is not as much of a concern. There are also the > kernel.org LLVM toolchains, which should work with distributions with > glibc 2.28 and newer. > > Another benefit of slimming up the number of supported versions of LLVM > for building the kernel is reducing the build capacity needed to support > a matrix that builds with each supported version, which allows a matrix > to reallocate the freed up build capacity towards something else, such > as more configuration combinations. > > This passes my build matrix with all supported versions. > > This is based on Andrew's mm-nonmm-unstable to avoid trivial conflicts > with my series to update the LLVM links across the repository [1] but I > can easily rebase it to linux-kbuild if Masahiro would rather these > patches go through there (and defer the conflict resolution to the merge > window). > > [1]: https://lore.kernel.org/20240109-update-llvm-links-v1-0-eb09b59db071@kernel.org/ > > --- > Nathan Chancellor (11): > kbuild: Raise the minimum supported version of LLVM to 13.0.1 > Makefile: Drop warn-stack-size plugin opt > x86: Drop stack-alignment plugin opt > ARM: Remove Thumb2 __builtin_thread_pointer workaround for Clang > arm64: Kconfig: Clean up tautological LLVM version checks > powerpc: Kconfig: Remove tautology in CONFIG_COMPAT > riscv: Remove MCOUNT_NAME workaround > riscv: Kconfig: Remove version dependency from CONFIG_CLANG_SUPPORTS_DYNAMIC_FTRACE > fortify: Drop Clang version check for 12.0.1 or newer > lib/Kconfig.debug: Update Clang version check in CONFIG_KCOV > compiler-clang.h: Update __diag_clang() macros for minimum version bump > > Documentation/process/changes.rst | 2 +- > Makefile | 8 -------- > arch/arm/include/asm/current.h | 8 +------- > arch/arm64/Kconfig | 5 +---- > arch/powerpc/Kconfig | 1 - > arch/riscv/Kconfig | 2 -- > arch/riscv/include/asm/ftrace.h | 14 ++------------ > arch/riscv/kernel/mcount.S | 10 +++++----- > arch/x86/Makefile | 6 ------ > include/linux/compiler-clang.h | 8 ++------ > lib/Kconfig.debug | 2 +- > scripts/min-tool-version.sh | 2 +- > scripts/recordmcount.pl | 2 +- > security/Kconfig | 2 -- > 14 files changed, 15 insertions(+), 57 deletions(-) > --- > base-commit: 979741ebd48f75ed6d101c7290e3325340d361ff > change-id: 20240124-bump-min-llvm-ver-to-13-0-1-39f84dd36b19 > > Best regards, > -- > Nathan Chancellor <nathan@kernel.org> > Yes, please. :) This looks reasonable -- I appreciate the review of default Clang versions across distros! Reviewed-by: Kees Cook <keescook@chromium.org>
Hello: This series was applied to riscv/linux.git (fixes) by Andrew Morton <akpm@linux-foundation.org>: On Thu, 25 Jan 2024 15:55:06 -0700 you wrote: > Hi all, > > This series bumps the minimum supported version of LLVM for building the > kernel to 13.0.1. The first patch does the bump and all subsequent > patches clean up all the various workarounds and checks for earlier > versions. > > [...] Here is the summary with links: - [07/11] riscv: Remove MCOUNT_NAME workaround https://git.kernel.org/riscv/c/de5f3984664e - [08/11] riscv: Kconfig: Remove version dependency from CONFIG_CLANG_SUPPORTS_DYNAMIC_FTRACE https://git.kernel.org/riscv/c/a38d97181271 You are awesome, thank you!
Hi all, This series bumps the minimum supported version of LLVM for building the kernel to 13.0.1. The first patch does the bump and all subsequent patches clean up all the various workarounds and checks for earlier versions. Quoting the first patch's commit message for those that were only on CC for the clean ups: When __builtin_mul_overflow() has arguments that differ in terms of signedness and width, LLVM may generate a libcall to __muloti4 because it performs the checks in terms of 65-bit multiplication. This issue becomes harder to hit (but still possible) after LLVM 12.0.0, which includes a special case for matching widths but different signs. To gain access to this special case, which the kernel can take advantage of when calls to __muloti4 appear, bump the minimum supported version of LLVM for building the kernel to 13.0.1. 13.0.1 was chosen because there is minimal impact to distribution support while allowing a few more workarounds to be dropped in the kernel source than if 12.0.0 were chosen. Looking at container images of up to date distribution versions: archlinux:latest clang version 16.0.6 debian:oldoldstable-slim clang version 7.0.1-8+deb10u2 (tags/RELEASE_701/final) debian:oldstable-slim Debian clang version 11.0.1-2 debian:stable-slim Debian clang version 14.0.6 debian:testing-slim Debian clang version 16.0.6 (19) debian:unstable-slim Debian clang version 16.0.6 (19) fedora:38 clang version 16.0.6 (Fedora 16.0.6-3.fc38) fedora:latest clang version 17.0.6 (Fedora 17.0.6-1.fc39) fedora:rawhide clang version 17.0.6 (Fedora 17.0.6-1.fc40) opensuse/leap:latest clang version 15.0.7 opensuse/tumbleweed:latest clang version 17.0.6 ubuntu:focal clang version 10.0.0-4ubuntu1 ubuntu:latest Ubuntu clang version 14.0.0-1ubuntu1.1 ubuntu:rolling Ubuntu clang version 16.0.6 (15) ubuntu:devel Ubuntu clang version 17.0.6 (3) The only distribution that gets left behind is Debian Bullseye, as the default version is 11.0.1; other distributions either have a newer version than 13.0.1 or one older than the current minimum of 11.0.0. Debian has easy access to more recent LLVM versions through apt.llvm.org, so this is not as much of a concern. There are also the kernel.org LLVM toolchains, which should work with distributions with glibc 2.28 and newer. Another benefit of slimming up the number of supported versions of LLVM for building the kernel is reducing the build capacity needed to support a matrix that builds with each supported version, which allows a matrix to reallocate the freed up build capacity towards something else, such as more configuration combinations. This passes my build matrix with all supported versions. This is based on Andrew's mm-nonmm-unstable to avoid trivial conflicts with my series to update the LLVM links across the repository [1] but I can easily rebase it to linux-kbuild if Masahiro would rather these patches go through there (and defer the conflict resolution to the merge window). [1]: https://lore.kernel.org/20240109-update-llvm-links-v1-0-eb09b59db071@kernel.org/ --- Nathan Chancellor (11): kbuild: Raise the minimum supported version of LLVM to 13.0.1 Makefile: Drop warn-stack-size plugin opt x86: Drop stack-alignment plugin opt ARM: Remove Thumb2 __builtin_thread_pointer workaround for Clang arm64: Kconfig: Clean up tautological LLVM version checks powerpc: Kconfig: Remove tautology in CONFIG_COMPAT riscv: Remove MCOUNT_NAME workaround riscv: Kconfig: Remove version dependency from CONFIG_CLANG_SUPPORTS_DYNAMIC_FTRACE fortify: Drop Clang version check for 12.0.1 or newer lib/Kconfig.debug: Update Clang version check in CONFIG_KCOV compiler-clang.h: Update __diag_clang() macros for minimum version bump Documentation/process/changes.rst | 2 +- Makefile | 8 -------- arch/arm/include/asm/current.h | 8 +------- arch/arm64/Kconfig | 5 +---- arch/powerpc/Kconfig | 1 - arch/riscv/Kconfig | 2 -- arch/riscv/include/asm/ftrace.h | 14 ++------------ arch/riscv/kernel/mcount.S | 10 +++++----- arch/x86/Makefile | 6 ------ include/linux/compiler-clang.h | 8 ++------ lib/Kconfig.debug | 2 +- scripts/min-tool-version.sh | 2 +- scripts/recordmcount.pl | 2 +- security/Kconfig | 2 -- 14 files changed, 15 insertions(+), 57 deletions(-) --- base-commit: 979741ebd48f75ed6d101c7290e3325340d361ff change-id: 20240124-bump-min-llvm-ver-to-13-0-1-39f84dd36b19 Best regards,