linux-hardening - Re: [PATCH] [PATCH v2] AARCH64: Add gcc Shadow Call Stack support

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Date:   Fri, 25 Feb 2022 12:59:45 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     Dan Li <ashimida@...ux.alibaba.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Marco Elver <elver@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] [PATCH v2] AARCH64: Add gcc Shadow Call Stack support

On Fri, Feb 25, 2022 at 09:47:19PM +0100, Miguel Ojeda wrote:
> On Fri, Feb 25, 2022 at 4:24 AM Dan Li <ashimida@...ux.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?
> 
> > +#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`?

I thought about that too, but I think it's less simple due to the
__has_feature vs CONFIG differences, etc:
https://lore.kernel.org/lkml/202202251243.1E38256F9@keescook/

But maybe __has_feature doesn't really matter here?

-- 
Kees Cook