From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752778AbcAGLau (ORCPT ); Thu, 7 Jan 2016 06:30:50 -0500 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:46360 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750809AbcAGLaq (ORCPT ); Thu, 7 Jan 2016 06:30:46 -0500 Date: Thu, 7 Jan 2016 11:30:29 +0000 From: Russell King - ARM Linux To: Kees Cook Cc: Arnd Bergmann , Simon Horman , Geert Uytterhoeven , Laurent Pinchart , Magnus Damm , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] ARM: fix atags_to_fdt with stack-protector-strong Message-ID: <20160107113029.GE19062@n2100.arm.linux.org.uk> References: <20160106233656.GA9316@www.outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160106233656.GA9316@www.outflux.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 06, 2016 at 03:36:56PM -0800, Kees Cook wrote: > diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile > index 3f9a9ebc77c3..d7d2c2981f65 100644 > --- a/arch/arm/boot/compressed/Makefile > +++ b/arch/arm/boot/compressed/Makefile > @@ -106,6 +106,14 @@ ORIG_CFLAGS := $(KBUILD_CFLAGS) > KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS)) > endif > > +# -fstack-protector-strong triggers protection checks in this code, > +# but it is being used too early to link to meaningful stack_chk logic. > +CFLAGS_atags_to_fdt.o := $(call cc-option, -fno-stack-protector) > +CFLAGS_fdt.o := $(call cc-option, -fno-stack-protector) > +CFLAGS_fdt_ro.o := $(call cc-option, -fno-stack-protector) > +CFLAGS_fdt_rw.o := $(call cc-option, -fno-stack-protector) > +CFLAGS_fdt_wip.o := $(call cc-option, -fno-stack-protector) This will result in "$(call cc-option, -fno-stack-protector)" being called five times when this Makefile is parsed, which seems very wasteful. I'm sure there's better solutions to that - maybe caching the value in a variable in a higher level makefile (eg, arch/arm/Makefile) ? Also, I suspect that all of the decompressor should be built with -fno-stack-protector as we don't have sufficient environment here. Maybe it should be placed in the global CFLAGS for the decompressor? -- RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.