[PATCH] [PATCH v2] AARCH64: Add gcc Shadow Call Stack support

[Nick Desaulniers]

On Sun, Feb 27, 2022 at 11:37 PM Dan Li <ashimida at linux.alibaba.com> wrote:
>
>
>
> On 2/25/22 12:47, Miguel Ojeda wrote:
> > On Fri, Feb 25, 2022 at 4:24 AM Dan Li <ashimida at linux.alibaba.com> wrote:
> >>
> >> +         - Clang (https://clang.llvm.org/docs/ShadowCallStack.html)
> >> +         - GCC (https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options)
> >
> > Maybe Clang: and GCC: instead of the parenthesis?
> >
> Got it.
>
> >> +#ifdef CONFIG_SHADOW_CALL_STACK
> >> +#define __noscs __attribute__((__no_sanitize__("shadow-call-stack")))
> >> +#endif
> >
> > Since both compilers have it, and I guess the `#ifdef` condition would
> > work for both, could this be moved into `compiler_types.h` where the
> > empty `__noscs` definition is, and remove the one from
> > `compiler-clang.h`?
> >
> In the clang documentation I see __has_feature(shadow_call_stack) is
> used to check if -fsanitize=shadow-call-stack is enabled, so I think
> maybe it's fine to use "#ifdef CONFIG_SHADOW_CALL_STACK"
> instead of "#if __has_attribute(__no_sanitize_address__)" here, then
> move it to `compiler_types.h`.

Or simply add a #define for __noscs to include/linux/compiler-gcc.h
with appropriate guard and leave the existing #ifndef in
include/linux/compiler_types.h as is.  I'd prefer that when the
compilers differ in terms of feature detection since it's as explicit
as possible.

>
> And from the results of my local clang 12 compilation, this doesn't
> seem to be a problem.
>
> Link: https://clang.llvm.org/docs/ShadowCallStack.html#has-feature-shadow-call-stack



-- 
Thanks,
~Nick Desaulniers