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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C410FC433FE for ; Wed, 23 Feb 2022 17:39:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243413AbiBWRkM (ORCPT ); Wed, 23 Feb 2022 12:40:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58144 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232607AbiBWRkL (ORCPT ); Wed, 23 Feb 2022 12:40:11 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A5236B48; Wed, 23 Feb 2022 09:39:43 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 26A4C61484; Wed, 23 Feb 2022 17:39:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4F2DC340E7; Wed, 23 Feb 2022 17:39:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1645637982; bh=UB/fdzNnOIHMXBBBmk61V4+OoYvesbVZ2l0elnEufzg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Kf3D2LPejolRCxzzwXBAjLaXRzKYJp3PVnWiPo6fUoWNajRrzf0DJpnrbGS310o+b d5Wp8WWyMsyHMqh1H4aXG7CkNqkqxv4nhSAXKmxgG0Wi4NmyoI0VJTpvgAse7fDhqh IEWoXVixG3N+TSSAF24zW1hB0F9jxPdSQghzIwFhmQqihwyNKVgQvCn5z5dfmBNCs9 ynAGTrmCV1hFtBbw+754CjyRqQN4nDhp5+vTuDH098HsUtx/ZeikW8QnO3DspbBz89 7KSa29WNpvX4IFs+d+kut4AytrYJVsnDTmBX/9nQDNosRbphm1Fr657UDS/CNoBrXU yp1WsX2CJWy7Q== Date: Wed, 23 Feb 2022 10:39:35 -0700 From: Nathan Chancellor To: Dan Li Cc: catalin.marinas@arm.com, will@kernel.org, ndesaulniers@google.com, keescook@chromium.org, masahiroy@kernel.org, tglx@linutronix.de, akpm@linux-foundation.org, mark.rutland@arm.com, samitolvanen@google.com, npiggin@gmail.com, linux@roeck-us.net, mhiramat@kernel.org, ojeda@kernel.org, luc.vanoostenryck@gmail.com, elver@google.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev, linux-hardening@vger.kernel.org Subject: Re: [PATCH] [PATCH] AARCH64: Add gcc Shadow Call Stack support Message-ID: References: <20220222095736.24898-1-ashimida@linux.alibaba.com> <69d351c6-a69d-6ebb-53bc-b46dfe4da08a@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <69d351c6-a69d-6ebb-53bc-b46dfe4da08a@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Wed, Feb 23, 2022 at 12:50:21AM -0800, Dan Li wrote: > > > On 2/22/22 08:16, Nathan Chancellor wrote: > > On Tue, Feb 22, 2022 at 01:57:36AM -0800, Dan Li wrote: > > > Shadow call stack is available in GCC > 11.2.0, this patch makes > > > the corresponding kernel configuration available when compiling > > > the kernel with gcc. > > > config SHADOW_CALL_STACK > > > - bool "Clang Shadow Call Stack" > > > - depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK > > > + bool "Shadow Call Stack" > > > + depends on ARCH_SUPPORTS_SHADOW_CALL_STACK > > > depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER > > > help > > > - This option enables Clang's Shadow Call Stack, which uses a > > > + This option enables Clang/GCC's Shadow Call Stack, which uses a > > > > I wonder if we want to just ditch the mention of the compiler if both > > support it? > > > > My intention is to remind users that this is a compiler feature. > But since there is also a hint in CC_HAVE_SHADOW_CALL_STACK: > +# Supported by clang >= 7.0 or GCC ... > > Removing the specific compiler here also looks fine to me. > Would this look better? > > "This option enables Shadow Call Stack, which uses a ..." > > or maybe: > > "This option enables compiler's Shadow Call Stack, which uses a ..." I do not honestly have a strong opinion around removing mention of the compiler so either looks fine to me (might be better to say "the compiler's Shadow ..." in the second one). > > > shadow stack to protect function return addresses from being > > > overwritten by an attacker. More information can be found in > > > Clang's documentation: > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > > index 09b885cc4db5..a48a604301aa 100644 > > > --- a/arch/arm64/Kconfig > > > +++ b/arch/arm64/Kconfig > > > @@ -1255,7 +1255,7 @@ config HW_PERF_EVENTS > > > config ARCH_HAS_FILTER_PGPROT > > > def_bool y > > > -# Supported by clang >= 7.0 > > > +# Supported by clang >= 7.0 or GCC > 11.2.0 > > > > Same thing here, although eventually there may be a minimum GCC version > > bump to something newer than 11.2.0, which would allow us to just drop > > CONFIG_CC_HAVE_SHADOW_CALL_STACK altogether. No strong opinion. > > > > As Guenter said, I thought maybe we could mark the minimum available > version for users :) Yes, that is what I was getting at with the "minimum version" comment. It should remain around. Cheers, Nathan