kernel-hardening - Re: [PATCH v5 25/29] arm64: allow LTO

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Message-ID: <20201012083116.GA785@willie-the-truck>
Date: Mon, 12 Oct 2020 09:31:16 +0100
From: Will Deacon <will@...nel.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	clang-built-linux@...glegroups.com,
	kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be
 selected

On Fri, Oct 09, 2020 at 09:13:34AM -0700, Sami Tolvanen wrote:
> Allow CONFIG_LTO_CLANG and CONFIG_THINLTO to be enabled.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> ---
>  arch/arm64/Kconfig | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index ad522b021f35..7016d193864f 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -72,6 +72,8 @@ config ARM64
>  	select ARCH_USE_SYM_ANNOTATIONS
>  	select ARCH_SUPPORTS_MEMORY_FAILURE
>  	select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
> +	select ARCH_SUPPORTS_LTO_CLANG
> +	select ARCH_SUPPORTS_THINLTO

Please don't enable this for arm64 until we have the dependency stuff sorted
out. I posted patches [1] for this before, but I think they should be part
of this series as they don't make sense on their own.

Will

[1] https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=rwonce/read-barrier-depends

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