Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D7EFC433FE for ; Wed, 15 Dec 2021 13:24:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242831AbhLONYP (ORCPT ); Wed, 15 Dec 2021 08:24:15 -0500 Received: from foss.arm.com ([217.140.110.172]:51814 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237399AbhLONYN (ORCPT ); Wed, 15 Dec 2021 08:24:13 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B4E75D6E; Wed, 15 Dec 2021 05:24:12 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.67.176]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 007803F774; Wed, 15 Dec 2021 05:24:07 -0800 (PST) Date: Wed, 15 Dec 2021 13:24:04 +0000 From: Mark Rutland To: Alexander Potapenko , Marco Elver , Peter Zijlstra Cc: Alexander Viro , Andrew Morton , Andrey Konovalov , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Dumazet , Greg Kroah-Hartman , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jens Axboe , Joonsoo Kim , Kees Cook , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Petr Mladek , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 07/43] compiler_attributes.h: add __disable_sanitizer_instrumentation Message-ID: References: <20211214162050.660953-1-glider@google.com> <20211214162050.660953-8-glider@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211214162050.660953-8-glider@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 14, 2021 at 05:20:14PM +0100, Alexander Potapenko wrote: > The new attribute maps to > __attribute__((disable_sanitizer_instrumentation)), which will be > supported by Clang >= 14.0. Future support in GCC is also possible. > > This attribute disables compiler instrumentation for kernel sanitizer > tools, making it easier to implement noinstr. It is different from the > existing __no_sanitize* attributes, which may still allow certain types > of instrumentation to prevent false positives. When you say the __no_sanitize* attributes allow some instrumentation, does that apply to any of the existing KASAN/KCSAN/KCOV support, or just for KMSAN? The documentation just says the same as the commit message: | This is not the same as __attribute__((no_sanitize(...))), which depending on | the tool may still insert instrumentation to prevent false positive reports. ... which implies the other instrumentation might not be suprressed. I ask because architectures which select ARCH_WANTS_NO_INSTR *need* to be able to suppress all instrumentation. It's fine if that means they need a new version of clang for KMSAN, but if there's latent instrumentation we have more bugs to fix first... Thanks, Mark. > Signed-off-by: Alexander Potapenko > --- > Link: https://linux-review.googlesource.com/id/Ic0123ce99b33ab7d5ed1ae90593425be8d3d774a > --- > include/linux/compiler_attributes.h | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h > index b9121afd87331..37e2600202216 100644 > --- a/include/linux/compiler_attributes.h > +++ b/include/linux/compiler_attributes.h > @@ -308,6 +308,24 @@ > # define __compiletime_warning(msg) > #endif > > +/* > + * Optional: only supported since clang >= 14.0 > + * > + * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation > + * > + * disable_sanitizer_instrumentation is not always similar to > + * no_sanitize(()): the latter may still let specific sanitizers > + * insert code into functions to prevent false positives. Unlike that, > + * disable_sanitizer_instrumentation prevents all kinds of instrumentation to > + * functions with the attribute. > + */ > +#if __has_attribute(disable_sanitizer_instrumentation) > +# define __disable_sanitizer_instrumentation \ > + __attribute__((disable_sanitizer_instrumentation)) > +#else > +# define __disable_sanitizer_instrumentation > +#endif > + > /* > * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute > * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute > -- > 2.34.1.173.g76aa8bc2d0-goog >