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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 1D8E3C43387 for ; Wed, 19 Dec 2018 20:20:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E415D2084A for ; Wed, 19 Dec 2018 20:20:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729801AbeLSUUY (ORCPT ); Wed, 19 Dec 2018 15:20:24 -0500 Received: from smtprelay0229.hostedemail.com ([216.40.44.229]:58492 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727151AbeLSUUY (ORCPT ); Wed, 19 Dec 2018 15:20:24 -0500 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay05.hostedemail.com (Postfix) with ESMTP id 6CDD618020002; Wed, 19 Dec 2018 20:20:22 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: duck39_7765deed8c144 X-Filterd-Recvd-Size: 4339 Received: from XPS-9350.home (unknown [47.151.153.53]) (Authenticated sender: joe@perches.com) by omf13.hostedemail.com (Postfix) with ESMTPA; Wed, 19 Dec 2018 20:20:20 +0000 (UTC) Message-ID: Subject: Re: [PATCH 2/7] tracing: Change strlen to sizeof for hist trigger static strings From: Joe Perches To: Tom Zanussi , Steven Rostedt Cc: 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 Date: Wed, 19 Dec 2018 12:20:19 -0800 In-Reply-To: <1545248809.2396.2.camel@kernel.org> References: <20181219144047.49fabfa6@gandalf.local.home> <1545248809.2396.2.camel@kernel.org> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.30.1-1build1 Mime-Version: 1.0 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, 2018-12-19 at 13:46 -0600, Tom Zanussi wrote: > Hi Steve, > > On Wed, 2018-12-19 at 14:40 -0500, Steven Rostedt wrote: > > On Tue, 18 Dec 2018 14:33:21 -0600 > > Tom Zanussi wrote: > > > > > From: Tom Zanussi > > > > > > There's no need to use strlen() for static strings when the length > > > is > > > already known, so update trace_events_hist.c with sizeof() for > > > those > > > cases. > > > > > > Signed-off-by: Tom Zanussi > > > --- > > > kernel/trace/trace_events_hist.c | 38 +++++++++++++++++++--------- > > > ---------- > > > 1 file changed, 19 insertions(+), 19 deletions(-) > > > > > > diff --git a/kernel/trace/trace_events_hist.c > > > b/kernel/trace/trace_events_hist.c > > > index d29bf8a8e1dd..25d06b3ae1f6 100644 > > > --- a/kernel/trace/trace_events_hist.c > > > +++ b/kernel/trace/trace_events_hist.c > > > @@ -507,7 +507,7 @@ static int synth_field_string_size(char *type) > > > start = strstr(type, "char["); > > > if (start == NULL) > > > return -EINVAL; > > > - start += strlen("char["); > > > + start += sizeof("char[") - 1; > > > > > > end = strchr(type, ']'); > > > if (!end || end < start) > > > @@ -1843,8 +1843,8 @@ static int parse_action(char *str, struct > > > hist_trigger_attrs *attrs) > > > if (attrs->n_actions >= HIST_ACTIONS_MAX) > > > return ret; > > > > > > - if ((strncmp(str, "onmatch(", strlen("onmatch(")) == 0) || > > > - (strncmp(str, "onmax(", strlen("onmax(")) == 0)) { > > > + if ((strncmp(str, "onmatch(", sizeof("onmatch(") - 1) == > > > 0) || > > > + (strncmp(str, "onmax(", sizeof("onmax(") - 1) == 0)) { > > > attrs->action_str[attrs->n_actions] = kstrdup(str, > > > GFP_KERNEL); > > > if (!attrs->action_str[attrs->n_actions]) { > > > ret = -ENOMEM; > > > @@ -1861,34 +1861,34 @@ static int parse_assignment(char *str, > > > struct hist_trigger_attrs *attrs) > > > { > > > int ret = 0; > > > > > > - if ((strncmp(str, "key=", strlen("key=")) == 0) || > > > - (strncmp(str, "keys=", strlen("keys=")) == 0)) { > > > + if ((strncmp(str, "key=", sizeof("key=") - 1) == 0) || > > > + (strncmp(str, "keys=", sizeof("keys=") - 1) == 0)) { > > > attrs->keys_str = kstrdup(str, GFP_KERNEL); > > > > I'll apply this as is, but since there's a lot of these, I wonder if > > we > > should make a marcro for this: > > > > #define strcmp_const(str, str_const) strncmp(str, str_const, > > sizeof(str_const) - 1) > > > > ? > > > > This would help prevent bugs due to typos and bad cut and paste. > > > > Yeah, I had considered it but wasn't sure it was worth it. Since > you're suggesting it is, I can send another patch on top of these, or > feel free if you want to too. ;-) I believe the 'strlen("foo") -> sizeof("foo") - 1' conversions do not change objects at all. strlen("constant") is already optimized by gcc to a constant value when fed a constant string. the strcmp_const macro does seem to make sense as the copy/paste/typo possibility is real.