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

Catalin Marinas
2024-08-23T09:48:55Z

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