linux-kernel - Re: [PATCH v11 27/39] arm64: Add Kconfig for Guarded Control Stack (GCS)

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Message-ID: <Zsha_58Y2nkOC35v@arm.com>
Date: Fri, 23 Aug 2024 10:48:47 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Mark Brown <broonie@...nel.org>
Cc: Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Arnd Bergmann <arnd@...db.de>, Oleg Nesterov <oleg@...hat.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	Shuah Khan <shuah@...nel.org>,
	"Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
	Deepak Gupta <debug@...osinc.com>, Ard Biesheuvel <ardb@...nel.org>,
	Szabolcs Nagy <Szabolcs.Nagy@....com>, Kees Cook <kees@...nel.org>,
	"H.J. Lu" <hjl.tools@...il.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
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	Albert Ou <aou@...s.berkeley.edu>,
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	Christian Brauner <brauner@...nel.org>,
	Thiago Jung Bauermann <thiago.bauermann@...aro.org>,
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	Yury Khrustalev <yury.khrustalev@....com>,
	Wilco Dijkstra <wilco.dijkstra@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
	kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
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	linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v11 27/39] arm64: Add Kconfig for Guarded Control Stack
 (GCS)

On Thu, Aug 22, 2024 at 02:15:30AM +0100, Mark Brown wrote:
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index a2f8ff354ca6..772f9ba99fe8 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -2137,6 +2137,26 @@ config ARM64_EPAN
>  	  if the cpu does not implement the feature.
>  endmenu # "ARMv8.7 architectural features"
>  
> +menu "v9.4 architectural features"
> +
> +config ARM64_GCS
> +	bool "Enable support for Guarded Control Stack (GCS)"
> +	default y
> +	select ARCH_HAS_USER_SHADOW_STACK
> +	select ARCH_USES_HIGH_VMA_FLAGS
> +	help
> +	  Guarded Control Stack (GCS) provides support for a separate
> +	  stack with restricted access which contains only return
> +	  addresses.  This can be used to harden against some attacks
> +	  by comparing return address used by the program with what is
> +	  stored in the GCS, and may also be used to efficiently obtain
> +	  the call stack for applications such as profiling.
> +
> +	  The feature is detected at runtime, and will remain disabled
> +	  if the system does not implement the feature.
> +
> +endmenu # "v9.4 architectural features"

BTW, as Mark R spotted we'd also need to handle uprobes. Since that's
off in defconfig, I think it can be done separately on top of this
series. In the meantime, we could make this dependent on !UPROBES.

-- 
Catalin