Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <1634148189-29393-1-git-send-email-ashimida@linux.alibaba.com>
In-Reply-To: <1634148189-29393-1-git-send-email-ashimida@linux.alibaba.com>
From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Wed, 13 Oct 2021 11:50:03 -0700
Message-ID: <CAKwvOd=qxHU41HFEWLAz6DOvSMPdW863E9SKVe0PFK0ePDvizQ@mail.gmail.com>
Subject: Re: [PATCH] [PATCH V3]ARM64: SCS: Add gcc plugin to support Shadow
 Call Stack
To:     Dan Li <ashimida@linux.alibaba.com>
Cc:     masahiroy@kernel.org, michal.lkml@markovi.net,
        catalin.marinas@arm.com, will@kernel.org, keescook@chromium.org,
        nathan@kernel.org, tglx@linutronix.de, akpm@linux-foundation.org,
        samitolvanen@google.com, frederic@kernel.org, rppt@kernel.org,
        mark.rutland@arm.com, yifeifz2@illinois.edu, rostedt@goodmis.org,
        viresh.kumar@linaro.org, andreyknvl@gmail.com,
        colin.king@canonical.com, ojeda@kernel.org,
        luc.vanoostenryck@gmail.com, elver@google.com,
        nivedita@alum.mit.edu, ardb@kernel.org,
        linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-hardening@vger.kernel.org, clang-built-linux@googlegroups.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Oct 13, 2021 at 11:03 AM Dan Li <ashimida@linux.alibaba.com> wrote:
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 62c3c1d..da2da8c 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -81,7 +81,7 @@ config ARM64
>         select ARCH_SUPPORTS_DEBUG_PAGEALLOC
>         select ARCH_SUPPORTS_HUGETLBFS
>         select ARCH_SUPPORTS_MEMORY_FAILURE
> -       select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
> +       select ARCH_SUPPORTS_SHADOW_CALL_STACK if (CC_HAVE_SHADOW_CALL_STACK || GCC_PLUGIN_SHADOW_CALL_STACK)
>         select ARCH_SUPPORTS_LTO_CLANG if CPU_LITTLE_ENDIAN
>         select ARCH_SUPPORTS_LTO_CLANG_THIN
>         select ARCH_SUPPORTS_CFI_CLANG
> @@ -1062,7 +1062,7 @@ config ARCH_HAS_FILTER_PGPROT
>
>  # Supported by clang >= 7.0
>  config CC_HAVE_SHADOW_CALL_STACK
> -       def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
> +       def_bool (CC_IS_CLANG && $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18))

I guess since clang supported SCS since clang-7, but the minimally
supported version of clang according to
Documentation/process/changes.rst is 10.0.1, then this could be:

def_boot CC_IS_CLANG || $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)

Then we won't have to touch it again once SCS lands in upstream GCC,
as the cc-option test will start to pass?
-- 
Thanks,
~Nick Desaulniers