From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89DC0C5DF60 for ; Tue, 5 Nov 2019 20:20:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2481D21A49 for ; Tue, 5 Nov 2019 20:20:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2481D21A49 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CEEA56B0003; Tue, 5 Nov 2019 15:20:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C9D3E6B0005; Tue, 5 Nov 2019 15:20:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BB3526B0006; Tue, 5 Nov 2019 15:20:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0050.hostedemail.com [216.40.44.50]) by kanga.kvack.org (Postfix) with ESMTP id A27E66B0003 for ; Tue, 5 Nov 2019 15:20:02 -0500 (EST) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 40BAD45C6 for ; Tue, 5 Nov 2019 20:20:02 +0000 (UTC) X-FDA: 76123340244.05.bird45_1d1525ba05a2d X-HE-Tag: bird45_1d1525ba05a2d X-Filterd-Recvd-Size: 3737 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf21.hostedemail.com (Postfix) with ESMTP for ; Tue, 5 Nov 2019 20:19:59 +0000 (UTC) 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 7A71D68D; Tue, 5 Nov 2019 12:19:56 -0800 (PST) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D060E40210; Tue, 5 Nov 2019 06:22:03 -0800 (PST) Date: Tue, 5 Nov 2019 14:21:55 +0000 From: Mark Rutland To: glider@google.com Cc: Vegard Nossum , Dmitry Vyukov , linux-mm@kvack.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, aryabinin@virtuozzo.com, luto@kernel.org, ard.biesheuvel@linaro.org, arnd@arndb.de, hch@lst.de, dmitry.torokhov@gmail.com, edumazet@google.com, ericvh@gmail.com, gregkh@linuxfoundation.org, harry.wentland@amd.com, herbert@gondor.apana.org.au, mingo@elte.hu, axboe@kernel.dk, martin.petersen@oracle.com, schwidefsky@de.ibm.com, mst@redhat.com, monstr@monstr.eu, pmladek@suse.com, sergey.senozhatsky@gmail.com, rostedt@goodmis.org, tiwai@suse.com, tytso@mit.edu, tglx@linutronix.de, wsa@the-dreams.de, gor@linux.ibm.com, iii@linux.ibm.com, willy@infradead.org, rdunlap@infradead.org, andreyknvl@google.com, elver@google.com Subject: Re: [PATCH RFC v2 10/25] kmsan: define READ_ONCE_NOCHECK() Message-ID: <20191105142155.GA45550@lakrids.cambridge.arm.com> References: <20191030142237.249532-1-glider@google.com> <20191030142237.249532-11-glider@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191030142237.249532-11-glider@google.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 30, 2019 at 03:22:22PM +0100, glider@google.com wrote: > READ_ONCE_NOCHECK() is already used by KASAN to ignore memory accesses > from e.g. stack unwinders. > Define READ_ONCE_NOCHECK() for KMSAN so that it returns initialized > values. This helps defeat false positives from leftover stack contents. > > Signed-off-by: Alexander Potapenko > To: Alexander Potapenko > Cc: Vegard Nossum > Cc: Dmitry Vyukov > Cc: linux-mm@kvack.org > --- > > Change-Id: Ib38369ba038ab3b581d8e45b81036c3304fb79cb > --- > include/linux/compiler.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 5e88e7e33abe..e8c86debdb2b 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -270,9 +270,13 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s > > /* > * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need > - * to hide memory access from KASAN. > + * to hide memory access from KASAN or KMSAN. > */ > +#ifndef CONFIG_KMSAN > #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0) > +#else > +#define READ_ONCE_NOCHECK(x) KMSAN_INIT_VALUE(__READ_ONCE(x, 0)) > +#endif When !CONFIG_KMSAN, we have: | #define KMSAN_INIT_VALUE(value) (value) ... so we don't need ifdeffery here, and can simply have: /* * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need * to hide memory access from KASAN or KMSAN. */ #define READ_ONCE_NOCHECK(x) KMSAN_INIT_VALUE(__READ_ONCE(x, 0)) Thanks, Mark. > > static __no_kasan_or_inline > unsigned long read_word_at_a_time(const void *addr) > -- > 2.24.0.rc0.303.g954a862665-goog >