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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 66627C43387 for ; Wed, 19 Dec 2018 20:34:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C16B20869 for ; Wed, 19 Dec 2018 20:34:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730074AbeLSUev (ORCPT ); Wed, 19 Dec 2018 15:34:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:40774 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727818AbeLSUeu (ORCPT ); Wed, 19 Dec 2018 15:34:50 -0500 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EFF7220866; Wed, 19 Dec 2018 20:34:48 +0000 (UTC) Date: Wed, 19 Dec 2018 15:34:47 -0500 From: Steven Rostedt To: Joe Perches Cc: Tom Zanussi , tglx@linutronix.de, mhiramat@kernel.org, namhyung@kernel.org, vedang.patel@intel.com, bigeasy@linutronix.de, joel@joelfernandes.org, mathieu.desnoyers@efficios.com, julia@ni.com, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org Subject: Re: [PATCH 2/7] tracing: Change strlen to sizeof for hist trigger static strings Message-ID: <20181219153447.3684100d@gandalf.local.home> In-Reply-To: References: <20181219144047.49fabfa6@gandalf.local.home> <1545248809.2396.2.camel@kernel.org> <1545250591.4161.2.camel@kernel.org> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 Dec 2018 12:22:38 -0800 Joe Perches wrote: > On Wed, 2018-12-19 at 14:16 -0600, Tom Zanussi wrote: > > > > How's this? > > > > [PATCH] tracing: Introduce and use strcmp_const() for hist triggers > > > > Provide a new strcmp_const() macro and make use of it instead of the > > longer and more error-prone strncmp(str, "str", sizeof("str") - 1). > [] > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c > [] > > @@ -22,6 +22,9 @@ > > > > #define STR_VAR_LEN_MAX 32 /* must be multiple of sizeof(u64) */ > > > > +#define strcmp_const(str, str_const) \ > > + strncmp(str, str_const, sizeof(str_const) - 1) > > Not good as it's too easy to pass a pointer as str_const > and sizeof(pointer) - 1 isn't likely the string length. Agreed. And I noticed that this is used all over the kernel, so I'm not going to add this patch. I'm going to add a: #define strncmp_prefix(str, prefix) \ strncmp(str, prefix, strlen(prefix)) in include/linux/string.h And go around and use that throughout the kernel. By doing a quick grep, I already spotted a few bugs. -- Steve