Re: [PATCH 01/14] kbuild: Bump minimum version of LLVM for building the kernel to 17.0.1

Re: [PATCH 01/14] kbuild: Bump minimum version of LLVM for building the kernel to 17.0.1

[Nicolas Schier]

On Tue, Apr 28, 2026 at 10:59:07PM -0400, Nathan Chancellor wrote:
> The current minimum version of LLVM for building the kernel is 15.0.0.
> However, there are two deficiencies compared to GCC that were fixed in
> LLVM 17 that are starting to become more noticeable.
> 
> The first was a bug in LLVM's scope checker [1], where all labels in a
> function were validated as potential targets of an asm goto statement,
> even if they were not listed in the asm goto statement as targets. This
> becomes particularly problematic when the cleanup attribute is used, as
> 
>   asm goto(... : label_a);
>   ...
> label_a:
>   ...
>   int var __free(foo);
>   asm goto(... : label_b);
>   ...
> label_b:
>   ...
> 
> will trigger an error since the scope checker will complain that the
> cleanup variable would be skipped when jumping from the first asm goto
> to label_b (which obviously cannot happen). This issue was the catalyst
> for commit e2ffa15b9baa ("kbuild: Disable CC_HAS_ASM_GOTO_OUTPUT on
> clang < 17"). Unfortunately, this issue is reproducible with regular asm
> goto in addition to asm goto with outputs, so that change was not
> entirely sufficient to avoid the issue altogether. As asm goto has
> effectively been required since commit a0a12c3ed057 ("asm goto:
> eradicate CC_HAS_ASM_GOTO") and the usage of the cleanup attribute
> continues to grow across the tree, raising the minimum to a version that
> avoids this issue altogether is a better long term solution than
> attempting to workaround it at every spot where it happens.
> 
> The second issue is an incompatibility with GCC 8.1+ around variables
> marked with const being valid constant expressions for _Static_assert
> and other macros [2]. With GCC 8.1 being the minimum supported version
> since commit 118c40b7b503 ("kbuild: require gcc-8 and binutils-2.30"),
> this incompatibility becomes more of a maintenance burden since only
> clang-15 and clang-16 are affected by it.
> 
> Looking at the clang version of various major distributions through
> Docker images, no one should be left behind as a result of this bump, as
> the old ones cannot clear the current minimum of 15.0.0.
> 
>   archlinux:latest              clang version 22.1.3
>   debian:oldoldstable-slim      Debian clang version 11.0.1-2
>   debian:oldstable-slim         Debian clang version 14.0.6
>   debian:stable-slim            Debian clang version 19.1.7 (3+b1)
>   debian:testing-slim           Debian clang version 21.1.8 (3+b1)
>   debian:unstable-slim          Debian clang version 21.1.8 (7+b1)
>   fedora:42                     clang version 20.1.8 (Fedora 20.1.8-4.fc42)
>   fedora:latest                 clang version 21.1.8 (Fedora 21.1.8-4.fc43)
>   fedora:44                     clang version 22.1.1 (Fedora 22.1.1-2.fc44)
>   fedora:rawhide                clang version 22.1.3 (Fedora 22.1.3-1.fc45)
>   opensuse/leap:latest          clang version 17.0.6
>   opensuse/tumbleweed:latest    clang version 21.1.8
>   ubuntu:jammy                  Ubuntu clang version 14.0.0-1ubuntu1.1
>   ubuntu:noble                  Ubuntu clang version 18.1.3 (1ubuntu1)
>   ubuntu:questing               Ubuntu clang version 20.1.8 (0ubuntu4)
>   ubuntu:resolute               Ubuntu clang version 21.1.8 (6ubuntu1)
> 
> 17.0.1 is chosen as the minimum instead of 17.0.0 to ensure that the
> particular version of LLVM 17 has the two aforementioned bugs fixed, as
> the second was fixed during the 17.0.0 release candidate phase and it
> was not until LLVM 18 that LLVM adopted the scheme of x.0.0 being a
> prerelease version and x.1.0 is a release version [3] to help with
> scenarios such as this.
> 
> Link: https://github.com/llvm/llvm-project/commit/f023f5cdb2e6c19026f04a15b5a935c041835d14 [1]
> Link: https://github.com/llvm/llvm-project/commit/0b2d5b967d98375793897295d651f58f6fbd3034 [2]
> Link: https://github.com/llvm/llvm-project/commit/4532617ae420056bf32f6403dde07fb99d276a49 [3]
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Shuah Khan <skhan@linuxfoundation.org>
> Cc: linux-doc@vger.kernel.org
> ---
>  Documentation/process/changes.rst | 2 +-
>  scripts/min-tool-version.sh       | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
> index 9a99037270ff..b9afce768446 100644
> --- a/Documentation/process/changes.rst
> +++ b/Documentation/process/changes.rst
> @@ -36,7 +36,7 @@ bindgen (optional)     0.71.1           bindgen --version
>  binutils               2.30             ld -v
>  bison                  2.0              bison --version
>  btrfs-progs            0.18             btrfs --version
> -Clang/LLVM (optional)  15.0.0           clang --version
> +Clang/LLVM (optional)  17.0.1           clang --version
>  e2fsprogs              1.41.4           e2fsck -V
>  flex                   2.5.35           flex --version
>  gdb                    7.2              gdb --version

FTR: The translations
Documentation/translations/{it_IT,pt_BR}/process/changes.rst become now
even more outdated.

Acked-by: Nicolas Schier <nsc@kernel.org>

Re: [PATCH 02/14] security/Kconfig.hardening: Remove tautological condition from CC_HAS_ZERO_CALL_USED_REGS

[Nicolas Schier]

On Tue, Apr 28, 2026 at 10:59:08PM -0400, Nathan Chancellor wrote:
> Now that the minimum supported version of LLVM for building the kernel
> has been raised to 17.0.1, the '!Clang || Clang > 15.0.6' dependency for
> CONFIG_CC_HAS_ZERO_CALL_USED_REGS is always true, so it can be removed.
> 
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> Cc: Kees Cook <kees@kernel.org>
> Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
> Cc: linux-hardening@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org
> ---
>  security/Kconfig.hardening | 3 ---
>  1 file changed, 3 deletions(-)
> 

Reviewed-by: Nicolas Schier <nsc@kernel.org>

Re: [PATCH 03/14] security/Kconfig.hardening: Remove tautological condition from FORTIFY_SOURCE

[Nicolas Schier]

On Tue, Apr 28, 2026 at 10:59:09PM -0400, Nathan Chancellor wrote:
> Now that the minimum supported version of LLVM for building the kernel
> has been raised to 17.0.1, the '!X86_32 || !Clang || Clang > 16'
> dependency of CONFIG_FORTIFY_SOURCE is always true, so it can be
> removed.
> 
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> Cc: Kees Cook <kees@kernel.org>
> Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
> Cc: linux-hardening@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org
> ---
>  security/Kconfig.hardening | 2 --
>  1 file changed, 2 deletions(-)
> 

Reviewed-by: Nicolas Schier <nsc@kernel.org>

Re: [PATCH 04/14] security/Kconfig.hardening: Remove tautological condition from CC_HAS_RANDSTRUCT

[Nicolas Schier]

On Tue, Apr 28, 2026 at 10:59:10PM -0400, Nathan Chancellor wrote:
> Now that the minimum supported version of LLVM for building the kernel
> has been raised to 17.0.1, the '!Clang || Clang >= 16' dependency for
> CONFIG_CC_HAS_RANDSTRUCT is always true, so it can be removed.
> 
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> Cc: Kees Cook <kees@kernel.org>
> Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
> Cc: linux-hardening@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org
> ---
>  security/Kconfig.hardening | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
> index e4f23c08a17a..b90cf9ed4642 100644
> --- a/security/Kconfig.hardening
> +++ b/security/Kconfig.hardening
> @@ -274,9 +274,6 @@ endmenu
>  
>  config CC_HAS_RANDSTRUCT
>  	def_bool $(cc-option,-frandomize-layout-seed-file=/dev/null)
> -	# Randstruct was first added in Clang 15, but it isn't safe to use until
> -	# Clang 16 due to https://github.com/llvm/llvm-project/issues/60349
> -	depends on !CC_IS_CLANG || CLANG_VERSION >= 160000
>  
>  choice
>  	prompt "Randomize layout of sensitive kernel structures"
> 

Reviewed-by: Nicolas Schier <nsc@kernel.org>

Re: [PATCH 05/14] arch/Kconfig: Remove tautological conditions from HAS_LTO_CLANG

[Nicolas Schier]

On Tue, Apr 28, 2026 at 10:59:11PM -0400, Nathan Chancellor wrote:
> Now that the minimum supported version of LLVM for building the kernel
> has been raised to 17.0.1, two dependency lines in CONFIG_HAS_LTO_CLANG
> are always true because Clang will always be newer than 17.0.0, so they
> can be removed.
> 
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
>  arch/Kconfig | 3 ---
>  1 file changed, 3 deletions(-)
> 

Reviewed-by: Nicolas Schier <nsc@kernel.org>

Re: [PATCH 10/14] scripts/Makefile.warn: Drop -Wformat handling for clang < 16

[Nicolas Schier]

On Tue, Apr 28, 2026 at 10:59:16PM -0400, Nathan Chancellor wrote:
> Now that the minimum supported version of LLVM for building the kernel
> has been raised to 17.0.1, the block dealing with -Wformat with clang
> prior to 16 can be removed since the condition for its inclusion is
> always false.
> 
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
>  scripts/Makefile.warn | 10 ----------
>  1 file changed, 10 deletions(-)
> 

Reviewed-by: Nicolas Schier <nsc@kernel.org>

Re: [PATCH 14/14] kbuild: Remove check for broken scoping with clang < 17 in CC_HAS_ASM_GOTO_OUTPUT

[Nicolas Schier]

On Tue, Apr 28, 2026 at 10:59:20PM -0400, Nathan Chancellor wrote:
> Now that the minimum supported version of LLVM for building the kernel
> has been raised to 17.0.1, the check added to CC_HAS_ASM_GOTO_OUTPUT by
> commit e2ffa15b9baa ("kbuild: Disable CC_HAS_ASM_GOTO_OUTPUT on clang <
> 17") can be removed, as the issue it detects is guaranteed to be fixed.
> 
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> Cc: Thomas Gleixner <tglx@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> ---
>  init/Kconfig | 3 ---
>  1 file changed, 3 deletions(-)
> 

Acked-by: Nicolas Schier <nsc@kernel.org>

Re: [PATCH 01/14] kbuild: Bump minimum version of LLVM for building the kernel to 17.0.1

[Daniel Pereira]

On Tue, May 5, 2026 at 1:11 PM Nicolas Schier <nsc@kernel.org> wrote:
>
>> FTR: The translations
>>Documentation/translations/{it\_IT,pt\_BR}/process/changes.rst become now
>>even more outdated.
>
>>Acked-by: Nicolas Schier <nsc@kernel.org>
>

Hi Nicolas,

Just confirming that I will make the necessary corrections to the
changes.rst Portuguese translation (pt\_BR) in the next few days.

Thanks,

Daniel Pereira
Linux Kernel Maintainer pt\_BR

Re: [PATCH 01/14] kbuild: Bump minimum version of LLVM for building the kernel to 17.0.1

[Nathan Chancellor]

Hi Daniel,

On Tue, May 05, 2026 at 03:26:40PM -0300, Daniel Pereira wrote:
> On Tue, May 5, 2026 at 1:11 PM Nicolas Schier <nsc@kernel.org> wrote:
> >
> >> FTR: The translations
> >>Documentation/translations/{it\_IT,pt\_BR}/process/changes.rst become now
> >>even more outdated.
> >
> >>Acked-by: Nicolas Schier <nsc@kernel.org>
> >
> 
> Hi Nicolas,
> 
> Just confirming that I will make the necessary corrections to the
> changes.rst Portuguese translation (pt\_BR) in the next few days.

Thanks but I think I can just update the version number in this patch
when I send v2, as the update should happen atomically. If you patch it
separately, it might not be true depending on when my change is merged.

-- 
Cheers,
Nathan

Re: [PATCH 01/14] kbuild: Bump minimum version of LLVM for building the kernel to 17.0.1

[Daniel Pereira]

On Wed, May 6, 2026 at 3:21 AM Nathan Chancellor <nathan@kernel.org> wrote:

>
>> Thanks but I think I can just update the version number in this patch
>> when I send v2, as the update should happen atomically. If you patch it
>> separately, it might not be true depending on when my change is merged.
>
>> --
>> Cheers,
>> Nathan

Hi Nathan,

Thanks for your reply. I still needed to adjust the changes.rst file
for the Portuguese translation (pt_BR), as I found it was quite
outdated compared to the current English document.

Thanks,

Daniel Pereira

Re: [PATCH 08/14] riscv: Remove tautological condition from selection of ARCH_SUPPORTS_CFI

[Paul Walmsley]

On Tue, 28 Apr 2026, Nathan Chancellor wrote:

> Now that the minimum supported version of LLVM for building the kernel
> has been raised to 17.0.1, the condition of the selection of
> CONFIG_ARCH_SUPPORTS_CFI is always true, so it can be removed.
> 
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Acked-by: Paul Walmsley <pjw@kernel.org> # arch/riscv

- Paul

Re: [PATCH 09/14] riscv: Drop tautological condition from TOOLCHAIN_NEEDS_OLD_ISA_SPEC

[Paul Walmsley]

On Tue, 28 Apr 2026, Nathan Chancellor wrote:

> Now that the minimum supported version of LLVM for building the kernel
> has been raised to 17.0.1, the Clang dependency part of
> CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC is always false, so it can be
> removed. Adjust the help text to remove mention of Clang < 17, as it is
> irrelevant for the kernel after the minimum supported bump.
> 
> Signed-off-by: Nathan Chancellor <nathan@kernel.org> 

Acked-by: Paul Walmsley <pjw@kernel.org>  # arch/riscv


- Paul