linux-kernel - Re: [PATCH] kbuild: move -fzero-init-padding-bits=all to the top-level Makefile

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Message-ID: <20250215203733.GA2954129@ax162>
Date: Sat, 15 Feb 2025 13:37:33 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
	Kees Cook <kees@...nel.org>, Nicolas Schier <nicolas@...sle.eu>
Subject: Re: [PATCH] kbuild: move -fzero-init-padding-bits=all to the
 top-level Makefile

On Sun, Feb 16, 2025 at 01:15:52AM +0900, Masahiro Yamada wrote:
> The -fzero-init-padding-bits=all option is not a warning flag, so
> defining it in scripts/Makefile.extrawarn is inconsistent.
> 
> Move it to the top-level Makefile for consistency.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Whoops, I will have to watch for that in the future.

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
> 
>  Makefile                   | 3 +++
>  scripts/Makefile.extrawarn | 3 ---
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 89628e354ca7..4a36864dd4bd 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -928,6 +928,9 @@ KBUILD_CFLAGS	+= $(CC_AUTO_VAR_INIT_ZERO_ENABLER)
>  endif
>  endif
>  
> +# Explicitly clear padding bits during variable initialization
> +KBUILD_CFLAGS += $(call cc-option,-fzero-init-padding-bits=all)
> +
>  # While VLAs have been removed, GCC produces unreachable stack probes
>  # for the randomize_kstack_offset feature. Disable it for all compilers.
>  KBUILD_CFLAGS	+= $(call cc-option, -fno-stack-clash-protection)
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index dc081cf46d21..d75897559d18 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -82,9 +82,6 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
>  # Warn if there is an enum types mismatch
>  KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
>  
> -# Explicitly clear padding bits during variable initialization
> -KBUILD_CFLAGS += $(call cc-option,-fzero-init-padding-bits=all)
> -
>  KBUILD_CFLAGS += -Wextra
>  KBUILD_CFLAGS += -Wunused
>  
> -- 
> 2.43.0
>