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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 3F34FC43331 for ; Sun, 10 Nov 2019 18:14:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1D08520818 for ; Sun, 10 Nov 2019 18:14:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726973AbfKJSOJ (ORCPT ); Sun, 10 Nov 2019 13:14:09 -0500 Received: from smtprelay0069.hostedemail.com ([216.40.44.69]:34071 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726684AbfKJSOI (ORCPT ); Sun, 10 Nov 2019 13:14:08 -0500 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay07.hostedemail.com (Postfix) with ESMTP id 088A3181D3417; Sun, 10 Nov 2019 18:14:07 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: hope08_5dfd750254439 X-Filterd-Recvd-Size: 2710 Received: from XPS-9350.home (unknown [47.151.135.224]) (Authenticated sender: joe@perches.com) by omf16.hostedemail.com (Postfix) with ESMTPA; Sun, 10 Nov 2019 18:14:05 +0000 (UTC) Message-ID: <61e165241e4b98cd655ac79cd110f3f08e389838.camel@perches.com> Subject: Re: [PATCH] lkdtm: Remove set but not used variable 'byte' From: Joe Perches To: Zheng Yongjun , keescook@chromium.org, arnd@arndb.de, gregkh@linuxfoundation.org Cc: linux-kernel@vger.kernel.org, Hulk Robot Date: Sun, 10 Nov 2019 10:13:50 -0800 In-Reply-To: <20191110092249.182210-1-zhengyongjun3@huawei.com> References: <20191110092249.182210-1-zhengyongjun3@huawei.com> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.34.1-2 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 Sun, 2019-11-10 at 17:22 +0800, Zheng Yongjun wrote: > Fixes gcc '-Wunused-but-set-variable' warning: > > drivers/misc/lkdtm/bugs.c: In function lkdtm_STACK_GUARD_PAGE_LEADING: > drivers/misc/lkdtm/bugs.c:236:25: warning: variable byte set but not used [-Wunused-but-set-variable] > drivers/misc/lkdtm/bugs.c: In function lkdtm_STACK_GUARD_PAGE_TRAILING: > drivers/misc/lkdtm/bugs.c:250:25: warning: variable byte set but not used [-Wunused-but-set-variable] > > byte is never used, so remove it. I believe "hulk robot" needs to be updated instead. It seems a generically bad idea to elide as byte is in fact used because it's volatile and the compiler was forced to perform the access of *ptr. > Reported-by: Hulk Robot > Signed-off-by: Zheng Yongjun > --- > drivers/misc/lkdtm/bugs.c | 6 ------ > 1 file changed, 6 deletions(-) > > diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c > index 7284a22b1a09..fcd943725b66 100644 > --- a/drivers/misc/lkdtm/bugs.c > +++ b/drivers/misc/lkdtm/bugs.c > @@ -249,12 +249,9 @@ void lkdtm_STACK_GUARD_PAGE_LEADING(void) > { > const unsigned char *stack = task_stack_page(current); > const unsigned char *ptr = stack - 1; > - volatile unsigned char byte; > > pr_info("attempting bad read from page below current stack\n"); > > - byte = *ptr; > - > pr_err("FAIL: accessed page before stack!\n"); > } > > @@ -263,12 +260,9 @@ void lkdtm_STACK_GUARD_PAGE_TRAILING(void) > { > const unsigned char *stack = task_stack_page(current); > const unsigned char *ptr = stack + THREAD_SIZE; > - volatile unsigned char byte; > > pr_info("attempting bad read from page above current stack\n"); > > - byte = *ptr; > - > pr_err("FAIL: accessed page after stack!\n"); > } >