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Date: Fri, 15 Nov 2019 14:46:08 +0000
From: Mark Rutland <mark.rutland@arm.com>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Dave Martin <Dave.Martin@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Laura Abbott <labbott@redhat.com>, Marc Zyngier <maz@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Jann Horn <jannh@google.com>,
	Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	clang-built-linux@googlegroups.com,
	kernel-hardening@lists.openwall.com,
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 13/14] arm64: disable SCS for hypervisor code
Message-ID: <20191115144607.GH41572@lakrids.cambridge.arm.com>
References: <20191018161033.261971-1-samitolvanen@google.com>
 <20191105235608.107702-1-samitolvanen@google.com>
 <20191105235608.107702-14-samitolvanen@google.com>
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In-Reply-To: <20191105235608.107702-14-samitolvanen@google.com>
User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01)

On Tue, Nov 05, 2019 at 03:56:07PM -0800, Sami Tolvanen wrote:
> Filter out CC_FLAGS_SCS for code that runs at a different exception
> level.
> 
> Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>

Looks sound, and objdump confirms that the hyp objects are using x29's
frame record, without using x18.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  arch/arm64/kvm/hyp/Makefile | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
> index ea710f674cb6..17ea3da325e9 100644
> --- a/arch/arm64/kvm/hyp/Makefile
> +++ b/arch/arm64/kvm/hyp/Makefile
> @@ -28,3 +28,6 @@ GCOV_PROFILE	:= n
>  KASAN_SANITIZE	:= n
>  UBSAN_SANITIZE	:= n
>  KCOV_INSTRUMENT	:= n
> +
> +# remove the SCS flags from all objects in this directory
> +KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
> -- 
> 2.24.0.rc1.363.gb1bccd3e3d-goog
>