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

[Catalin Marinas]

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