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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 4F722C433E0 for ; Thu, 4 Jun 2020 15:51:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2646020738 for ; Thu, 4 Jun 2020 15:51:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729593AbgFDPvq (ORCPT ); Thu, 4 Jun 2020 11:51:46 -0400 Received: from mail3-relais-sop.national.inria.fr ([192.134.164.104]:37213 "EHLO mail3-relais-sop.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729302AbgFDPvq (ORCPT ); Thu, 4 Jun 2020 11:51:46 -0400 X-IronPort-AV: E=Sophos;i="5.73,472,1583190000"; d="scan'208";a="350605555" Received: from abo-173-121-68.mrs.modulonet.fr (HELO hadrien) ([85.68.121.173]) by mail3-relais-sop.national.inria.fr with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Jun 2020 17:51:20 +0200 Date: Thu, 4 Jun 2020 17:51:19 +0200 (CEST) From: Julia Lawall X-X-Sender: jll@hadrien To: Denis Efremov cc: Julia Lawall , cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org Subject: Re: [PATCH] coccinelle: api: add kzfree script In-Reply-To: Message-ID: References: <20200604140805.111613-1-efremov@linux.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 On Thu, 4 Jun 2020, Denis Efremov wrote: > > > On 6/4/20 5:15 PM, Julia Lawall wrote: > > Did you try ... here but find that some subexpressions of E could be > > modified in between? > > Yes, I tried to use "... when != E = E1 when != &E" and results were bad. > Now, I've tried forall and when strict. Here are examples: > > // forall added > // Works well, suitable for v2. One additional catch in w1 driver. > @r depends on !patch && !(file in "lib/test_kasan.c") && !(file in "mm/slab_common.c") forall@ > expression *E; // pointer. Results are equal as if we use E. > position p; > @@ > > * memset(E, 0, ...); > ... when != E // Is it enough to match &E, E = E1? Yes. > * kfree(E)@p; > > //no forall, when strict > //results are bad, too many false positives > @r depends on !patch && !(file in "lib/test_kasan.c") && !(file in "mm/slab_common.c")@ > expression *E; > position p; > @@ > > * memset(E, 0, ...); > ... when != E // E is not enough here > when strict OK, it's reassonable. > * kfree(E)@p; > > I guess that the difference is that "forall" requires that whole pattern should occur on > every path, "when strict" states that kfree should be called on every path after memset. > This results in missed uses of E in loops and under conditions. How can I state in this > case that E should not occur at all (in all paths) in between memset, kfree even as a > subexpression? > > // Doesn't work well > ... when != E > when != if (...) { ... E ... } > when != for(...;...;...) { ... E ... } Could you send an example of some C code on which the result is not suitable? julia