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 BB08EC32767 for ; Sat, 4 Jan 2020 07:17:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E103222C4 for ; Sat, 4 Jan 2020 07:17:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726036AbgADHRB (ORCPT ); Sat, 4 Jan 2020 02:17:01 -0500 Received: from mail3-relais-sop.national.inria.fr ([192.134.164.104]:47665 "EHLO mail3-relais-sop.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725870AbgADHRB (ORCPT ); Sat, 4 Jan 2020 02:17:01 -0500 X-IronPort-AV: E=Sophos;i="5.69,393,1571695200"; d="scan'208";a="334728961" Received: from abo-154-110-68.mrs.modulonet.fr (HELO hadrien) ([85.68.110.154]) by mail3-relais-sop.national.inria.fr with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Jan 2020 08:16:58 +0100 Date: Sat, 4 Jan 2020 08:16:58 +0100 (CET) From: Julia Lawall X-X-Sender: jll@hadrien To: Wen Yang cc: Gilles Muller , Nicolas Palix , Michal Marek , Matthias Maennich , Greg Kroah-Hartman , Masahiro Yamada , Thomas Gleixner , cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org Subject: Re: [PATCH] coccinelle: semantic patch to check for inappropriate do_div() calls In-Reply-To: <20200104064448.24314-1-wenyang@linux.alibaba.com> Message-ID: References: <20200104064448.24314-1-wenyang@linux.alibaba.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --- Please note the new email address --- On Sat, 4 Jan 2020, Wen Yang wrote: > do_div() does a 64-by-32 division. > When the divisor is unsigned long, u64, or s64, > do_div() truncates it to 32 bits, this means it > can test non-zero and be truncated to zero for division. Would it be worth having a specific warning message for the long/unsigned long case? If the target architecture has 32 bit longs then the warning can be immediately ignored. julia > This semantic patch is inspired by Mateusz Guzik's patch: > commit b0ab99e7736a ("sched: Fix possible divide by zero in avg_atom() calculation") > > Signed-off-by: Wen Yang > Cc: Julia Lawall > Cc: Gilles Muller > Cc: Nicolas Palix > Cc: Michal Marek > Cc: Matthias Maennich > Cc: Greg Kroah-Hartman > Cc: Masahiro Yamada > Cc: Thomas Gleixner > Cc: cocci@systeme.lip6.fr > Cc: linux-kernel@vger.kernel.org > --- > scripts/coccinelle/misc/do_div.cocci | 66 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 66 insertions(+) > create mode 100644 scripts/coccinelle/misc/do_div.cocci > > diff --git a/scripts/coccinelle/misc/do_div.cocci b/scripts/coccinelle/misc/do_div.cocci > new file mode 100644 > index 0000000..f1b72d1 > --- /dev/null > +++ b/scripts/coccinelle/misc/do_div.cocci > @@ -0,0 +1,66 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/// do_div() does a 64-by-32 division. > +/// When the divisor is unsigned long, u64, or s64, > +/// do_div() truncates it to 32 bits, this means it > +/// can test non-zero and be truncated to zero for division. > +/// > +//# This makes an effort to find those inappropriate do_div () calls. > +// > +// Confidence: Moderate > +// Copyright: (C) 2020 Wen Yang, Alibaba. > +// Comments: > +// Options: --no-includes --include-headers > + > +virtual context > +virtual org > +virtual report > + > +@depends on context@ > +expression f; > +long l; > +unsigned long ul; > +u64 ul64; > +s64 sl64; > + > +@@ > +( > +* do_div(f, l); > +| > +* do_div(f, ul); > +| > +* do_div(f, ul64); > +| > +* do_div(f, sl64); > +) > + > +@r depends on (org || report)@ > +expression f; > +long l; > +unsigned long ul; > +position p; > +u64 ul64; > +s64 sl64; > +@@ > +( > +do_div@p(f, l); > +| > +do_div@p(f, ul); > +| > +do_div@p(f, ul64); > +| > +do_div@p(f, sl64); > +) > + > +@script:python depends on org@ > +p << r.p; > +@@ > + > +msg="WARNING: WARNING: do_div() does a 64-by-32 division, which may truncation the divisor to 32-bit" > +coccilib.org.print_todo(p[0], msg) > + > +@script:python depends on report@ > +p << r.p; > +@@ > + > +msg="WARNING: WARNING: do_div() does a 64-by-32 division, which may truncation the divisor to 32-bit" > +coccilib.report.print_report(p[0], msg) > -- > 1.8.3.1 > >