Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752255AbdGRTxp (ORCPT ); Tue, 18 Jul 2017 15:53:45 -0400 Received: from mail-oi0-f68.google.com ([209.85.218.68]:35469 "EHLO mail-oi0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751500AbdGRTxm (ORCPT ); Tue, 18 Jul 2017 15:53:42 -0400 MIME-Version: 1.0 In-Reply-To: References: <20170714092540.1217397-1-arnd@arndb.de> <20170714092540.1217397-8-arnd@arndb.de> From: Arnd Bergmann Date: Tue, 18 Jul 2017 21:53:40 +0200 X-Google-Sender-Auth: wumBE5T1hi98gpVrj3xH0Jk5uu0 Message-ID: Subject: Re: [PATCH 07/14] proc/kcore: hide a harmless warning To: Ard Biesheuvel Cc: "linux-kernel@vger.kernel.org" , Jiri Olsa , Greg Kroah-Hartman , Linus Torvalds , Tejun Heo , Guenter Roeck , IDE-ML , Linux Media Mailing List , Andrew Morton , dri-devel , Kees Cook , Ingo Molnar , Laura Abbott , Pratyush Anand Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v6IJrnUd029776 Content-Length: 1660 Lines: 41 On Fri, Jul 14, 2017 at 2:28 PM, Ard Biesheuvel wrote: > On 14 July 2017 at 10:25, Arnd Bergmann wrote: >> gcc warns when MODULES_VADDR/END is defined to the same value as >> VMALLOC_START/VMALLOC_END, e.g. on x86-32: >> >> fs/proc/kcore.c: In function ‘add_modules_range’: >> fs/proc/kcore.c:622:161: error: self-comparison always evaluates to false [-Werror=tautological-compare] >> if (/*MODULES_VADDR != VMALLOC_START && */MODULES_END != VMALLOC_END) { >> > > Does it occur for subtraction as well? Or only for comparison? This replacement patch would also address the warning: diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 45629f4b5402..35824e986c2c 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -623,7 +623,7 @@ static void __init proc_kcore_text_init(void) struct kcore_list kcore_modules; static void __init add_modules_range(void) { - if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) { + if (MODULES_VADDR - VMALLOC_START && MODULES_END - VMALLOC_END) { kclist_add(&kcore_modules, (void *)MODULES_VADDR, MODULES_END - MODULES_VADDR, KCORE_VMALLOC); } I have also verified that four of the 14 patches are not needed when building without ccache, this is one of them: acpi: thermal: fix gcc-6/ccache warning proc/kcore: hide a harmless warning SFI: fix tautological-compare warning [media] fix warning on v4l2_subdev_call() result interpreted as bool Not sure what to do with those, we could either ignore them all and not care about ccache, or we try to address them all in some way. Arnd