Re: [PATCH 06/18] add support for Clang's Shadow Call Stack (SCS)

Sami Tolvanen
2019-10-18T17:11:44Z

On Fri, Oct 18, 2019 at 10:08 AM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
> > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> > index 333a6695a918..9af08391f205 100644
> > --- a/include/linux/compiler-clang.h
> > +++ b/include/linux/compiler-clang.h
> > @@ -42,3 +42,5 @@
> > * compilers, like ICC.
> > */
> > #define barrier() __asm__ __volatile__("" : : : "memory")
> > +
> > +#define __noscs __attribute__((no_sanitize("shadow-call-stack")))
>
> It looks like this attribute, (and thus a requirement to use this
> feature), didn't exist until Clang 7.0: https://godbolt.org/z/p9u1we
> (as noted above)
>
> I think it's better to put __noscs behind a __has_attribute guard in
> include/linux/compiler_attributes.h. Otherwise, what will happen when
> Clang 6.0 sees __noscs, for example? (-Wunknown-sanitizers will
> happen).

Good point, I'll fix this in v2. Thanks.

Sami