[PATCH 00/10] Bump minimum supported version of LLVM for building the kernel to 15.0.0

[PATCH 00/10] Bump minimum supported version of LLVM for building the kernel to 15.0.0

[Nathan Chancellor]

s390 and x86 have required LLVM 15 since

  30d17fac6aae ("scripts/min-tool-version.sh: raise minimum clang version to 15.0.0 for s390")
  7861640aac52 ("x86/build: Raise the minimum LLVM version to 15.0.0")

respectively. This series bumps the rest of the kernel to 15.0.0 to
match, which allows for a decent number of clean ups.

On the distros front, we will only leave behind Debian Bookworm and
Ubuntu Jammy. In both of those cases, builders / developers can either
use the kernel.org toolchains or https://apt.llvm.org to get newer
versions that will run on those distributions, if they cannot upgrade.

  archlinux:latest              clang version 20.1.8
  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 19.1.7 (3+b1)
  debian:unstable-slim          Debian clang version 19.1.7 (3+b2)
  fedora:41                     clang version 19.1.7 (Fedora 19.1.7-4.fc41)
  fedora:latest                 clang version 20.1.8 (Fedora 20.1.8-3.fc42)
  fedora:rawhide                clang version 20.1.8 (Fedora 20.1.8-3.fc43)
  opensuse/leap:latest          clang version 17.0.6
  opensuse/tumbleweed:latest    clang version 20.1.8
  ubuntu:focal                  clang version 10.0.0-4ubuntu1
  ubuntu:jammy                  Ubuntu clang version 14.0.0-1ubuntu1.1
  ubuntu:noble                  Ubuntu clang version 18.1.3 (1ubuntu1)
  ubuntu:latest                 Ubuntu clang version 18.1.3 (1ubuntu1)
  ubuntu:rolling                Ubuntu clang version 20.1.2 (0ubuntu1)
  ubuntu:devel                  Ubuntu clang version 20.1.8 (0ubuntu1)

I think it makes sense for either Andrew to carry this via -mm on a
nonmm branch or me to carry this via the Kbuild tree, with the
appropriate acks.

---
Nathan Chancellor (10):
      kbuild: Bump minimum version of LLVM for building the kernel to 15.0.0
      arch/Kconfig: Drop always true condition from RANDOMIZE_KSTACK_OFFSET
      ARM: Clean up definition of ARM_HAS_GROUP_RELOCS
      arm64: Remove tautological LLVM Kconfig conditions
      mips: Unconditionally select ARCH_HAS_CURRENT_STACK_POINTER
      powerpc: Drop unnecessary initializations in __copy_inst_from_kernel_nofault()
      riscv: Remove version check for LTO_CLANG selects
      lib/Kconfig.debug: Drop CLANG_VERSION check from DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
      objtool: Drop noinstr hack for KCSAN_WEAK_MEMORY
      KMSAN: Remove tautological checks

 Documentation/process/changes.rst |  2 +-
 arch/Kconfig                      |  1 -
 arch/arm/Kconfig                  | 11 ++++-------
 arch/arm64/Kconfig                |  5 +----
 arch/mips/Kconfig                 |  2 +-
 arch/powerpc/include/asm/inst.h   |  4 ----
 arch/riscv/Kconfig                |  5 ++---
 lib/Kconfig.debug                 |  2 +-
 lib/Kconfig.kcsan                 |  6 ------
 lib/Kconfig.kmsan                 | 11 +----------
 scripts/min-tool-version.sh       |  6 ++----
 tools/objtool/check.c             | 10 ----------
 12 files changed, 13 insertions(+), 52 deletions(-)
---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250710-bump-min-llvm-ver-15-95231f1eb655

Best regards,
--  
Nathan Chancellor <nathan@kernel.org>


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[PATCH 07/10] riscv: Remove version check for LTO_CLANG selects

[Nathan Chancellor]

Now that the minimum supported version of LLVM for building the kernel
has been bumped to 15.0.0, there is no need to check the LLD version
before selecting ARCH_SUPPORTS_LTO_CLANG{,_THIN} because it will always
be true.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: linux-riscv@lists.infradead.org

Small note, this will conflict with
https://lore.kernel.org/20250710-riscv-restrict-lto-to-medany-v1-1-b1dac9871ecf@kernel.org/
but I think it is simple enough to deal with.
---
 arch/riscv/Kconfig | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a4b233a0659e..1d53bf02d0fa 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -64,9 +64,8 @@ config RISCV
 	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
 	select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
 	select ARCH_SUPPORTS_HUGETLBFS if MMU
-	# LLD >= 14: https://github.com/llvm/llvm-project/issues/50505
-	select ARCH_SUPPORTS_LTO_CLANG if LLD_VERSION >= 140000
-	select ARCH_SUPPORTS_LTO_CLANG_THIN if LLD_VERSION >= 140000
+	select ARCH_SUPPORTS_LTO_CLANG
+	select ARCH_SUPPORTS_LTO_CLANG_THIN
 	select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS if 64BIT && MMU
 	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
 	select ARCH_SUPPORTS_PER_VMA_LOCK if MMU

-- 
2.50.1


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Re: [PATCH 00/10] Bump minimum supported version of LLVM for building the kernel to 15.0.0

[Kees Cook]

On Mon, Aug 18, 2025 at 11:57:16AM -0700, Nathan Chancellor wrote:
> s390 and x86 have required LLVM 15 since
>
>   30d17fac6aae ("scripts/min-tool-version.sh: raise minimum clang version to 15.0.0 for s390")
>   7861640aac52 ("x86/build: Raise the minimum LLVM version to 15.0.0")
>
> respectively. This series bumps the rest of the kernel to 15.0.0 to
> match, which allows for a decent number of clean ups.

Looks good to me!

Reviewed-by: Kees Cook <kees@kernel.org>

> I think it makes sense for either Andrew to carry this via -mm on a
> nonmm branch or me to carry this via the Kbuild tree, with the
> appropriate acks.

I vote you carry it with Kbuild. :)

--
Kees Cook

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Re: [PATCH 07/10] riscv: Remove version check for LTO_CLANG selects

[Alexandre Ghiti]

Hi Nathan,

On 8/18/25 20:57, Nathan Chancellor wrote:
> Now that the minimum supported version of LLVM for building the kernel
> has been bumped to 15.0.0, there is no need to check the LLD version
> before selecting ARCH_SUPPORTS_LTO_CLANG{,_THIN} because it will always
> be true.
>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Alexandre Ghiti <alex@ghiti.fr>
> Cc: linux-riscv@lists.infradead.org
>
> Small note, this will conflict with
> https://lore.kernel.org/20250710-riscv-restrict-lto-to-medany-v1-1-b1dac9871ecf@kernel.org/
> but I think it is simple enough to deal with.


FYI, I'll send this patch for some 6.17-rcX.


> ---
>   arch/riscv/Kconfig | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index a4b233a0659e..1d53bf02d0fa 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -64,9 +64,8 @@ config RISCV
>   	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
>   	select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
>   	select ARCH_SUPPORTS_HUGETLBFS if MMU
> -	# LLD >= 14: https://github.com/llvm/llvm-project/issues/50505
> -	select ARCH_SUPPORTS_LTO_CLANG if LLD_VERSION >= 140000
> -	select ARCH_SUPPORTS_LTO_CLANG_THIN if LLD_VERSION >= 140000
> +	select ARCH_SUPPORTS_LTO_CLANG
> +	select ARCH_SUPPORTS_LTO_CLANG_THIN
>   	select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS if 64BIT && MMU
>   	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
>   	select ARCH_SUPPORTS_PER_VMA_LOCK if MMU
>

I found another bunch of LLD_VERSION check in this file that could be 
removed:

https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L253
https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L262
https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L630
https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L731
https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L746
https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L781
https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L804

Thanks,

Alex


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Re: [PATCH 07/10] riscv: Remove version check for LTO_CLANG selects

[Nathan Chancellor]

On Wed, Aug 20, 2025 at 09:23:08AM +0200, Alexandre Ghiti wrote:
> Hi Nathan,
> 
> On 8/18/25 20:57, Nathan Chancellor wrote:
> > Now that the minimum supported version of LLVM for building the kernel
> > has been bumped to 15.0.0, there is no need to check the LLD version
> > before selecting ARCH_SUPPORTS_LTO_CLANG{,_THIN} because it will always
> > be true.
> > 
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > ---
> > Cc: Palmer Dabbelt <palmer@dabbelt.com>
> > Cc: Alexandre Ghiti <alex@ghiti.fr>
> > Cc: linux-riscv@lists.infradead.org
> > 
> > Small note, this will conflict with
> > https://lore.kernel.org/20250710-riscv-restrict-lto-to-medany-v1-1-b1dac9871ecf@kernel.org/
> > but I think it is simple enough to deal with.
> 
> FYI, I'll send this patch for some 6.17-rcX.

Thanks, that would help.

> I found another bunch of LLD_VERSION check in this file that could be
> removed:

Huh, I am very surprised that I missed those :/ thanks a lot for
catching that!

> https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L253

I have added a patch removing CONFIG_RISCV_USE_LINKER_RELAXATION.

> https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L262

I don't think this one can be currently cleaned up since it won't always
be either true or false.

> https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L630
> https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L731
> https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L746
> https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L781
> https://elixir.bootlin.com/linux/v6.17-rc2/source/arch/riscv/Kconfig#L804

I have added a patch converting those version checks to just LD_IS_LLD.

Cheers,
Nathan

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