linux-kernel - Re: [PATCH 05/11] arm64: Kconfig: Clean up tautological LLVM version checks

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Message-ID: <ZbOsvhDB-6LMVACP@FVFF77S0Q05N>
Date: Fri, 26 Jan 2024 12:59:55 +0000
From: Mark Rutland <mark.rutland@....com>
To: Nathan Chancellor <nathan@...nel.org>
Cc: akpm@...ux-foundation.org, masahiroy@...nel.org, nicolas@...sle.eu,
	linux-kbuild@...r.kernel.org, llvm@...ts.linux.dev,
	patches@...ts.linux.dev, linux-kernel@...r.kernel.org,
	catalin.marinas@....com, will@...nel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 05/11] arm64: Kconfig: Clean up tautological LLVM version
 checks

On Thu, Jan 25, 2024 at 03:55:11PM -0700, Nathan Chancellor wrote:
> Now that the minimum supported version of LLVM for building the kernel
> has been bumped to 13.0.1, several conditions become tautologies, as
> they will always be true because the build will fail during the
> configuration stage for older LLVM versions. Drop them, as they are
> unnecessary.
> 
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> Cc: catalin.marinas@....com
> Cc: will@...nel.org
> Cc: mark.rutland@....com
> Cc: linux-arm-kernel@...ts.infradead.org
> ---
>  arch/arm64/Kconfig | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 5a8acca4dbf4..cb34e7d780c0 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -383,7 +383,7 @@ config BUILTIN_RETURN_ADDRESS_STRIPS_PAC
>  	bool
>  	# Clang's __builtin_return_adddress() strips the PAC since 12.0.0
>  	# https://github.com/llvm/llvm-project/commit/2a96f47c5ffca84cd774ad402cacd137f4bf45e2
> -	default y if CC_IS_CLANG && (CLANG_VERSION >= 120000)
> +	default y if CC_IS_CLANG
>  	# GCC's __builtin_return_address() strips the PAC since 11.1.0,
>  	# and this was backported to 10.2.0, 9.4.0, 8.5.0, but not earlier
>  	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94891
> @@ -1387,7 +1387,6 @@ choice
>  
>  config CPU_BIG_ENDIAN
>  	bool "Build big-endian kernel"
> -	depends on !LD_IS_LLD || LLD_VERSION >= 130000
>  	# https://github.com/llvm/llvm-project/commit/1379b150991f70a5782e9a143c2ba5308da1161c

We can delete the URL here, since that was just to describe why this depended
upon LLVM 13+; it's weird for it to sit here on its own.

The URL above for __builtin_return_address() can stay or go; it may as well
stay since we have the comment aboout LLvm 12+ above it.

With that:

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

>  	depends on AS_IS_GNU || AS_VERSION >= 150000
>  	help
> @@ -2018,8 +2017,6 @@ config ARM64_BTI_KERNEL
>  	depends on !CC_IS_GCC || GCC_VERSION >= 100100
>  	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106671
>  	depends on !CC_IS_GCC
> -	# https://github.com/llvm/llvm-project/commit/a88c722e687e6780dcd6a58718350dc76fcc4cc9
> -	depends on !CC_IS_CLANG || CLANG_VERSION >= 120000
>  	depends on (!FUNCTION_GRAPH_TRACER || DYNAMIC_FTRACE_WITH_ARGS)
>  	help
>  	  Build the kernel with Branch Target Identification annotations
> 
> -- 
> 2.43.0
>