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Subject: Re: [PATCH] [PATCH V3]ARM64: SCS: Add gcc plugin to support Shadow
 Call Stack
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     masahiroy@kernel.org, michal.lkml@markovi.net,
        catalin.marinas@arm.com, will@kernel.org, keescook@chromium.org,
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        colin.king@canonical.com, ojeda@kernel.org,
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        nivedita@alum.mit.edu, ardb@kernel.org,
        linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
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References: <1634148189-29393-1-git-send-email-ashimida@linux.alibaba.com>
 <CAKwvOd=qxHU41HFEWLAz6DOvSMPdW863E9SKVe0PFK0ePDvizQ@mail.gmail.com>
From:   Dan Li <ashimida@linux.alibaba.com>
Message-ID: <c2d0bfc9-364e-a2a8-e786-7a5102e34ddc@linux.alibaba.com>
Date:   Thu, 14 Oct 2021 05:40:08 +0800
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On 10/14/21 2:50 AM, Nick Desaulniers wrote:
> 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,

That sounds reasonable.