Re: [PATCH] [PATCH V3]ARM64: SCS: Add gcc plugin to support Shadow Call Stack

[Dan Li]

On 10/14/21 2:50 AM, Nick Desaulniers wrote:
> On Wed, Oct 13, 2021 at 11:03 AM Dan Li <ashimida@xxxxxxxxxxxxxxxxx> 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.