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Message-ID: <26a0a816-bc3e-2ac0-d773-0819d9f225af@linux.alibaba.com>
Date:   Sun, 27 Feb 2022 23:37:38 -0800
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Subject: Re: [PATCH] [PATCH v2] AARCH64: Add gcc Shadow Call Stack support
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To:     Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Kees Cook <keescook@chromium.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Sami Tolvanen <samitolvanen@google.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Guenter Roeck <linux@roeck-us.net>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Miguel Ojeda <ojeda@kernel.org>,
        Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
        Marco Elver <elver@google.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        llvm@lists.linux.dev, linux-hardening@vger.kernel.org
References: <20220225032410.25622-1-ashimida@linux.alibaba.com>
 <CANiq72kXoonDYk095XvBwEtRCRNECd1iQOqJHE2cNcgLyUMfcQ@mail.gmail.com>
From:   Dan Li <ashimida@linux.alibaba.com>
In-Reply-To: <CANiq72kXoonDYk095XvBwEtRCRNECd1iQOqJHE2cNcgLyUMfcQ@mail.gmail.com>
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On 2/25/22 12:47, Miguel Ojeda wrote:
> On Fri, Feb 25, 2022 at 4:24 AM Dan Li <ashimida@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`.

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