Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933423AbcKNUph (ORCPT ); Mon, 14 Nov 2016 15:45:37 -0500 Received: from mail.skyhub.de ([78.46.96.112]:59497 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932297AbcKNUpc (ORCPT ); Mon, 14 Nov 2016 15:45:32 -0500 Date: Mon, 14 Nov 2016 21:45:29 +0100 From: Borislav Petkov To: Sebastian Andrzej Siewior Cc: linux-kbuild@vger.kernel.org, Ben Hutchings , Michal Marek , x86-ml , lkml , +@pd.tnic Subject: [PATCH -v1.1] kbuild: Steal gcc's pie from the very beginning Message-ID: <20161114204529.sqn6z2bockmhxpfz@pd.tnic> References: <20161114185130.30641-1-bp@alien8.de> <20161114201457.qsevfvn465otwfvz@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20161114201457.qsevfvn465otwfvz@linutronix.de> User-Agent: NeoMutt/20161014 (1.7.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3012 Lines: 91 On Mon, Nov 14, 2016 at 09:14:57PM +0100, Sebastian Andrzej Siewior wrote: > This also means that all feature tests fail unless the -fno-PIE is > there. > > Acked-by: Sebastian Andrzej Siewior > > This thing gcc v3.4 only but I intend to update the min requirement to > alteast gcc v3.4 to cover this. As per hpa gcc v3.4 is the lowest > version should be used for x86… Ah yes, here's a v1.1. Let's leave the cc-option check until we sort out the min supported gcc version. CC: stable too. Thanks! --- From: Borislav Petkov Date: Mon, 14 Nov 2016 19:41:31 +0100 Subject: [PATCH] kbuild: Steal gcc's pie from the very beginning So Sebastian turned off the PIE for kernel builds but that was too late - Kbuild.include already uses KBUILD_CFLAGS and trying to disable gcc options with, say cc-disable-warning, fails: gcc -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs ... -Wno-sign-compare -fno-asynchronous-unwind-tables -Wframe-address -c -x c /dev/null -o .31392.tmp /dev/null:1:0: error: code model kernel does not support PIC mode because that returns an error and we can't disable the warning. For example in this case: KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,) which leads to gcc issuing all those warnings again. So let's turn off PIE/PIC at the earliest possible moment, when we declare KBUILD_CFLAGS so that cc-disable-warning picks it up too. Also, we need the $(call cc-option ...) because -fno-PIE is supported since gcc v3.4 and our lowest supported gcc version is 3.2 right now. Signed-off-by: Borislav Petkov Cc: stable@vger.kernel.org Cc: Ben Hutchings Cc: Michal Marek Cc: Sebastian Andrzej Siewior --- Makefile | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/Makefile b/Makefile index 3ff1fb26d8b2..9bc877d073d7 100644 --- a/Makefile +++ b/Makefile @@ -399,11 +399,12 @@ KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \ -fno-strict-aliasing -fno-common \ -Werror-implicit-function-declaration \ -Wno-format-security \ - -std=gnu89 + -std=gnu89 $(call cc-option,-fno-PIE) + KBUILD_AFLAGS_KERNEL := KBUILD_CFLAGS_KERNEL := -KBUILD_AFLAGS := -D__ASSEMBLY__ +KBUILD_AFLAGS := -D__ASSEMBLY__ $(call cc-option,-fno-PIE) KBUILD_AFLAGS_MODULE := -DMODULE KBUILD_CFLAGS_MODULE := -DMODULE KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds @@ -621,8 +622,6 @@ include arch/$(SRCARCH)/Makefile KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,) KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,) -KBUILD_CFLAGS += $(call cc-option,-fno-PIE) -KBUILD_AFLAGS += $(call cc-option,-fno-PIE) ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION KBUILD_CFLAGS += $(call cc-option,-ffunction-sections,) -- 2.10.0 -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.