linux-kernel - Re: [PATCH v3 2/3] randstruct: Force full rebuild when seed changes

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Message-ID: <20250507-righteous-turquoise-bustard-4fca48@l-nschier-aarch64>
Date: Wed, 7 May 2025 14:14:51 +0200
From: Nicolas Schier <nicolas.schier@...ux.dev>
To: Kees Cook <kees@...nel.org>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Petr Pavlu <petr.pavlu@...e.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-kbuild@...r.kernel.org, Justin Stitt <justinstitt@...gle.com>,
	Marco Elver <elver@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org, kasan-dev@...glegroups.com,
	llvm@...ts.linux.dev
Subject: Re: [PATCH v3 2/3] randstruct: Force full rebuild when seed changes

On Sat, 03 May 2025, Kees Cook wrote:

> While the randstruct GCC plugin was being rebuilt if the randstruct seed
> changed, Clang builds did not notice the change. This could result in
> differing struct layouts in a target depending on when it was built.
> 
> Include the existing generated header file in compiler-version.h when
> its associated feature name, RANDSTRUCT, is defined. This will be picked
> up by fixdep and force rebuilds where needed.
> 
> Signed-off-by: Kees Cook <kees@...nel.org>
> ---
> Cc: Masahiro Yamada <masahiroy@...nel.org>
> Cc: Nathan Chancellor <nathan@...nel.org>
> Cc: Nicolas Schier <nicolas.schier@...ux.dev>
> Cc: Petr Pavlu <petr.pavlu@...e.com>
> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Cc: <linux-kbuild@...r.kernel.org>
> ---
>  include/linux/compiler-version.h | 3 +++
>  include/linux/vermagic.h         | 1 -
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/compiler-version.h b/include/linux/compiler-version.h
> index 74ea11563ce3..69b29b400ce2 100644
> --- a/include/linux/compiler-version.h
> +++ b/include/linux/compiler-version.h
> @@ -16,3 +16,6 @@
>  #ifdef GCC_PLUGINS
>  #include <generated/gcc-plugins.h>
>  #endif
> +#ifdef RANDSTRUCT
> +#include <generated/randstruct_hash.h>
> +#endif
> diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h
> index 939ceabcaf06..335c360d4f9b 100644
> --- a/include/linux/vermagic.h
> +++ b/include/linux/vermagic.h
> @@ -33,7 +33,6 @@
>  #define MODULE_VERMAGIC_MODVERSIONS ""
>  #endif
>  #ifdef RANDSTRUCT
> -#include <generated/randstruct_hash.h>
>  #define MODULE_RANDSTRUCT "RANDSTRUCT_" RANDSTRUCT_HASHED_SEED
>  #else
>  #define MODULE_RANDSTRUCT
> -- 
> 2.34.1
> 

Reviewed-by: Nicolas Schier <n.schier@....de>
Tested-by: Nicolas Schier <n.schier@....de>