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=-14.3 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_IN_DEF_DKIM_WL 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 48B21C432C3 for ; Thu, 21 Nov 2019 12:09:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F3BE920679 for ; Thu, 21 Nov 2019 12:09:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="qjDXYiaT" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F3BE920679 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A59576B030E; Thu, 21 Nov 2019 07:09:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A098D6B0311; Thu, 21 Nov 2019 07:09:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8F7856B0313; Thu, 21 Nov 2019 07:09:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0022.hostedemail.com [216.40.44.22]) by kanga.kvack.org (Postfix) with ESMTP id 7782B6B030E for ; Thu, 21 Nov 2019 07:09:12 -0500 (EST) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 381BD5DEB for ; Thu, 21 Nov 2019 12:09:12 +0000 (UTC) X-FDA: 76180164144.30.water37_1611c0ba57549 X-HE-Tag: water37_1611c0ba57549 X-Filterd-Recvd-Size: 6379 Received: from mail-wm1-f65.google.com (mail-wm1-f65.google.com [209.85.128.65]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Thu, 21 Nov 2019 12:09:11 +0000 (UTC) Received: by mail-wm1-f65.google.com with SMTP id l17so3463757wmh.0 for ; Thu, 21 Nov 2019 04:09:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=IzjZSfMrunHGb7vduavpwaqqSoHa/4JZH2uchauZK9E=; b=qjDXYiaTcacbbsIidu5+c8BZ5/JxXW4citrAmnaslqVly+6I95k7IOTzpQ75DsDtVk jTY2cRvPbv1Mb5C6AZZDc4RkkOfCoE34IpzLYc3gKEltmBndDkyH1baNJwdBTm62eg9v ntZrDWdpvfQ/rUNydbFK6LOqeil8L9PyB1d+8MqZCKmvbb4b0RntgS6P+gtCZwERPcwp mLSigceXRFhARwqqM/M4cHuaTAD/qPuICRcFNCW0VLwvWncbqV/DI0rdVvXMdyEIKko4 OaLB5q9nST3e8rn7tcKW7YcRwOn1k8+1qwYbd96yZubDr4Ha8Mt+Y6HBBRNyWSG/1xpP pEyQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=IzjZSfMrunHGb7vduavpwaqqSoHa/4JZH2uchauZK9E=; b=EMFk6z+KUIVR99ymQr25jJmDf1TCE3MUXBbijsGc7+z9eNiyFPxgmCwgj3GpolkvY+ dH8Bp8mzvvxRqiU+jmq63ZrcpHsNeoxvY1qfeobxsSOJTaUyvdmMpZsqU9oTfIxMKKx0 3t46CtQo778aTmErlaO9M0/c0oTplYL7v6xXafxgOeGE5gO1jit+q332fvdlBNLBXMAg hcyppGesHj4BZ2ONXGCy+CRKW5GbdoJ/cC6AckzgSuXoJPa1K2Kae/T5CTdxBUpqvT1B kCUmJtRxwsnV9wd/Jya4ZruL60kTBRCI67tmYlOisQkkDAB2RkSkYbgqqFl1WXN8wVu+ CAWA== X-Gm-Message-State: APjAAAXKNHeOrPM6qNI9Zhn0hw4Tnrm4q31Fi8C74p2CnFkM76yeVaKy UmEncTLbmNUSnbt2kIrz6cXm7lLg5uY32b2IIattDQ== X-Google-Smtp-Source: APXvYqz+XCyYBMWmtymRztM84CS0cgJwQpPox2MzVNFBtf3TH/l7cbaUIavm1/WLsLbL8fchWxSP8w4ObwrEZAYXs24= X-Received: by 2002:a1c:7d16:: with SMTP id y22mr9263803wmc.106.1574338149934; Thu, 21 Nov 2019 04:09:09 -0800 (PST) MIME-Version: 1.0 References: <20191030142237.249532-1-glider@google.com> <20191030142237.249532-11-glider@google.com> <20191105142155.GA45550@lakrids.cambridge.arm.com> In-Reply-To: <20191105142155.GA45550@lakrids.cambridge.arm.com> From: Alexander Potapenko Date: Thu, 21 Nov 2019 13:08:58 +0100 Message-ID: Subject: Re: [PATCH RFC v2 10/25] kmsan: define READ_ONCE_NOCHECK() To: Mark Rutland Cc: Vegard Nossum , Dmitry Vyukov , Linux Memory Management List , Al Viro , Andrew Morton , Andrey Ryabinin , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Christoph Hellwig , Dmitry Torokhov , Eric Dumazet , Eric Van Hensbergen , Greg Kroah-Hartman , Harry Wentland , Herbert Xu , Ingo Molnar , Jens Axboe , "Martin K . Petersen" , Martin Schwidefsky , "Michael S. Tsirkin" , Michal Simek , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , Takashi Iwai , "Theodore Ts'o" , Thomas Gleixner , Wolfram Sang , Vasily Gorbik , Ilya Leoshkevich , Matthew Wilcox , Randy Dunlap , Andrey Konovalov , Marco Elver Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 Tue, Nov 5, 2019 at 9:19 PM Mark Rutland wrote: > > 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(vola= tile 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)) Agreed, thanks! > Thanks, > Mark. > > > > > static __no_kasan_or_inline > > unsigned long read_word_at_a_time(const void *addr) > > -- > > 2.24.0.rc0.303.g954a862665-goog > > --=20 Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Stra=C3=9Fe, 33 80636 M=C3=BCnchen Gesch=C3=A4ftsf=C3=BChrer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg