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 866A5C433F5 for ; Wed, 15 Dec 2021 13:27:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242841AbhLON1v (ORCPT ); Wed, 15 Dec 2021 08:27:51 -0500 Received: from foss.arm.com ([217.140.110.172]:51922 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237399AbhLON1u (ORCPT ); Wed, 15 Dec 2021 08:27:50 -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 EEAE9ED1; Wed, 15 Dec 2021 05:27:49 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.67.176]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2AF9E3F774; Wed, 15 Dec 2021 05:27:45 -0800 (PST) Date: Wed, 15 Dec 2021 13:27:42 +0000 From: Mark Rutland To: Alexander Potapenko 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 , Marco Elver , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , 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 09/43] kmsan: introduce __no_sanitize_memory and __no_kmsan_checks Message-ID: References: <20211214162050.660953-1-glider@google.com> <20211214162050.660953-10-glider@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211214162050.660953-10-glider@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 14, 2021 at 05:20:16PM +0100, Alexander Potapenko wrote: > __no_sanitize_memory is a function attribute that instructs KMSAN to > skip a function during instrumentation. This is needed to e.g. implement > the noinstr functions. > > __no_kmsan_checks is a function attribute that makes KMSAN > ignore the uninitialized values coming from the function's > inputs, and initialize the function's outputs. > > Functions marked with this attribute can't be inlined into functions > not marked with it, and vice versa. Just to check, I assume an unmarked __always_inline() function can be inlined into a marked function? Otherwise this is going to be really painful to manage for low-level helper functions. Thanks, Mark. > > __SANITIZE_MEMORY__ is a macro that's defined iff the file is > instrumented with KMSAN. This is not the same as CONFIG_KMSAN, which is > defined for every file. > > Signed-off-by: Alexander Potapenko > --- > Link: https://linux-review.googlesource.com/id/I004ff0360c918d3cd8b18767ddd1381c6d3281be > --- > include/linux/compiler-clang.h | 23 +++++++++++++++++++++++ > include/linux/compiler-gcc.h | 6 ++++++ > 2 files changed, 29 insertions(+) > > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h > index 3c4de9b6c6e3e..5f11a6f269e28 100644 > --- a/include/linux/compiler-clang.h > +++ b/include/linux/compiler-clang.h > @@ -51,6 +51,29 @@ > #define __no_sanitize_undefined > #endif > > +#if __has_feature(memory_sanitizer) > +#define __SANITIZE_MEMORY__ > +/* > + * Unlike other sanitizers, KMSAN still inserts code into functions marked with > + * no_sanitize("kernel-memory"). Using disable_sanitizer_instrumentation > + * provides the behavior consistent with other __no_sanitize_ attributes, > + * guaranteeing that __no_sanitize_memory functions remain uninstrumented. > + */ > +#define __no_sanitize_memory __disable_sanitizer_instrumentation > + > +/* > + * The __no_kmsan_checks attribute ensures that a function does not produce > + * false positive reports by: > + * - initializing all local variables and memory stores in this function; > + * - skipping all shadow checks; > + * - passing initialized arguments to this function's callees. > + */ > +#define __no_kmsan_checks __attribute__((no_sanitize("kernel-memory"))) > +#else > +#define __no_sanitize_memory > +#define __no_kmsan_checks > +#endif > + > /* > * Support for __has_feature(coverage_sanitizer) was added in Clang 13 together > * with no_sanitize("coverage"). Prior versions of Clang support coverage > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > index ccbbd31b3aae5..f6e69387aad05 100644 > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -129,6 +129,12 @@ > #define __SANITIZE_ADDRESS__ > #endif > > +/* > + * GCC does not support KMSAN. > + */ > +#define __no_sanitize_memory > +#define __no_kmsan_checks > + > /* > * Turn individual warnings and errors on and off locally, depending > * on version. > -- > 2.34.1.173.g76aa8bc2d0-goog >