From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=Yun1=YR=vger.kernel.org=linux-kernel-owner@kernel.org>
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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1
	autolearn=no 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 E6618CA9EAF
	for <linux-kernel@archiver.kernel.org>; Thu, 24 Oct 2019 13:28:53 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id C199F2166E
	for <linux-kernel@archiver.kernel.org>; Thu, 24 Oct 2019 13:28:53 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S2393588AbfJXN2w (ORCPT
        <rfc822;linux-kernel@archiver.kernel.org>);
        Thu, 24 Oct 2019 09:28:52 -0400
Received: from foss.arm.com ([217.140.110.172]:51362 "EHLO foss.arm.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S2388733AbfJXN2w (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 24 Oct 2019 09:28:52 -0400
Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14])
        by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A65C3C8F;
        Thu, 24 Oct 2019 06:28:36 -0700 (PDT)
Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14])
        by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 004113F71A;
        Thu, 24 Oct 2019 06:28:34 -0700 (PDT)
Date:   Thu, 24 Oct 2019 14:28:32 +0100
From:   Mark Rutland <mark.rutland@arm.com>
To:     Sami Tolvanen <samitolvanen@google.com>
Cc:     Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Dave Martin <Dave.Martin@arm.com>,
        Kees Cook <keescook@chromium.org>,
        Laura Abbott <labbott@redhat.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 06/18] add support for Clang's Shadow Call Stack (SCS)
Message-ID: <20191024132832.GG4300@lakrids.cambridge.arm.com>
References: <20191018161033.261971-1-samitolvanen@google.com>
 <20191018161033.261971-7-samitolvanen@google.com>
 <20191022162826.GC699@lakrids.cambridge.arm.com>
 <CABCJKudxvS9Eehr0dEFUR4H44K-PUULbjrh0i=pP_r5MGrKptA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CABCJKudxvS9Eehr0dEFUR4H44K-PUULbjrh0i=pP_r5MGrKptA@mail.gmail.com>
User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Oct 22, 2019 at 12:26:02PM -0700, Sami Tolvanen wrote:
> On Tue, Oct 22, 2019 at 9:28 AM Mark Rutland <mark.rutland@arm.com> wrote:

> > > +config SHADOW_CALL_STACK
> > > +     bool "Clang Shadow Call Stack"
> > > +     depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
> > > +     depends on CC_IS_CLANG && CLANG_VERSION >= 70000
> >
> > Is there a reason for an explicit version check rather than a
> > CC_HAS_<feature> check? e.g. was this available but broken in prior
> > versions of clang?
> 
> No, this feature was added in Clang 7. However,
> -fsanitize=shadow-call-stack might require architecture-specific
> flags, so a simple $(cc-option, -fsanitize=shadow-call-stack) in
> arch/Kconfig is not going to work. I could add something like this to
> arch/arm64/Kconfig though:
> 
> select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
> ...
> config CC_HAVE_SHADOW_CALL_STACK
>        def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
> 
> And then drop CC_IS_CLANG and version check entirely. Thoughts?

That sounds good to me, yes!

Thanks,
Mark.

From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=dzuu=YR=lists.infradead.org=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@kernel.org>
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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,
	SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 6E3B3CA9EBC
	for <infradead-linux-arm-kernel@archiver.kernel.org>; Thu, 24 Oct 2019 13:34:41 +0000 (UTC)
Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by mail.kernel.org (Postfix) with ESMTPS id 16B2D21925
	for <infradead-linux-arm-kernel@archiver.kernel.org>; Thu, 24 Oct 2019 13:34:41 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="C7td8CJT"
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 16B2D21925
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com
Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;
	d=lists.infradead.org; s=bombadil.20170209; h=Sender:
	Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post:
	List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:
	Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description:
	Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:
	List-Owner; bh=YR0Xl6m3rRuez0MPbVGp573Pc/kDMWy3eIbw6u12DQg=; b=C7td8CJTgWqjL4
	dEwNYnqEULGnEx1LX+J3l3qTVuJXYW8XvdtzxEP6JEaANts6WzYI+z51xlLd16wE2yurzkmt4RJbD
	dGJYXn7VUFCJQ9TqYlU+A636ClODGJ2Bv7chR1y3dZZ6jIcyUpzQK7S9XaP7lm6rzBrIX9OrJGVVK
	O3i/3a+Ao8JVxKXlZkoC43p/ReMYgUU00WazZbiP3UuzrTPmvdPEvrnfRhQBl/IIYo9nsMVstRDxH
	K2rMhbOYMiXFJ8kEuBImaUwcdUoWz3I3yDq4BH+rX/jIW781gI+Twif6Rdx0iYFA3IWZREf5rArPV
	YPNMadT91LMWjtDVhA+g==;
Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org)
	by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux))
	id 1iNdG4-0002fp-7s; Thu, 24 Oct 2019 13:34:32 +0000
Received: from [217.140.110.172] (helo=foss.arm.com)
 by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux))
 id 1iNdAX-00052V-7I
 for linux-arm-kernel@lists.infradead.org; Thu, 24 Oct 2019 13:28:52 +0000
Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14])
 by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A65C3C8F;
 Thu, 24 Oct 2019 06:28:36 -0700 (PDT)
Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com
 [10.121.207.14])
 by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 004113F71A;
 Thu, 24 Oct 2019 06:28:34 -0700 (PDT)
Date: Thu, 24 Oct 2019 14:28:32 +0100
From: Mark Rutland <mark.rutland@arm.com>
To: Sami Tolvanen <samitolvanen@google.com>
Subject: Re: [PATCH 06/18] add support for Clang's Shadow Call Stack (SCS)
Message-ID: <20191024132832.GG4300@lakrids.cambridge.arm.com>
References: <20191018161033.261971-1-samitolvanen@google.com>
 <20191018161033.261971-7-samitolvanen@google.com>
 <20191022162826.GC699@lakrids.cambridge.arm.com>
 <CABCJKudxvS9Eehr0dEFUR4H44K-PUULbjrh0i=pP_r5MGrKptA@mail.gmail.com>
MIME-Version: 1.0
Content-Disposition: inline
In-Reply-To: <CABCJKudxvS9Eehr0dEFUR4H44K-PUULbjrh0i=pP_r5MGrKptA@mail.gmail.com>
User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01)
X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 
X-CRM114-CacheID: sfid-20191024_062849_326690_1EA7A2BF 
X-CRM114-Status: GOOD (  14.31  )
X-BeenThere: linux-arm-kernel@lists.infradead.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: <linux-arm-kernel.lists.infradead.org>
List-Unsubscribe: <http://lists.infradead.org/mailman/options/linux-arm-kernel>, 
 <mailto:linux-arm-kernel-request@lists.infradead.org?subject=unsubscribe>
List-Archive: <http://lists.infradead.org/pipermail/linux-arm-kernel/>
List-Post: <mailto:linux-arm-kernel@lists.infradead.org>
List-Help: <mailto:linux-arm-kernel-request@lists.infradead.org?subject=help>
List-Subscribe: <http://lists.infradead.org/mailman/listinfo/linux-arm-kernel>, 
 <mailto:linux-arm-kernel-request@lists.infradead.org?subject=subscribe>
Cc: Kees Cook <keescook@chromium.org>,
 Ard Biesheuvel <ard.biesheuvel@linaro.org>,
 Catalin Marinas <catalin.marinas@arm.com>,
 Kernel Hardening <kernel-hardening@lists.openwall.com>,
 Nick Desaulniers <ndesaulniers@google.com>,
 LKML <linux-kernel@vger.kernel.org>, Steven Rostedt <rostedt@goodmis.org>,
 clang-built-linux <clang-built-linux@googlegroups.com>,
 Laura Abbott <labbott@redhat.com>, Will Deacon <will@kernel.org>,
 Dave Martin <Dave.Martin@arm.com>,
 linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Sender: "linux-arm-kernel" <linux-arm-kernel-bounces@lists.infradead.org>
Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org

On Tue, Oct 22, 2019 at 12:26:02PM -0700, Sami Tolvanen wrote:
> On Tue, Oct 22, 2019 at 9:28 AM Mark Rutland <mark.rutland@arm.com> wrote:

> > > +config SHADOW_CALL_STACK
> > > +     bool "Clang Shadow Call Stack"
> > > +     depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
> > > +     depends on CC_IS_CLANG && CLANG_VERSION >= 70000
> >
> > Is there a reason for an explicit version check rather than a
> > CC_HAS_<feature> check? e.g. was this available but broken in prior
> > versions of clang?
> 
> No, this feature was added in Clang 7. However,
> -fsanitize=shadow-call-stack might require architecture-specific
> flags, so a simple $(cc-option, -fsanitize=shadow-call-stack) in
> arch/Kconfig is not going to work. I could add something like this to
> arch/arm64/Kconfig though:
> 
> select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
> ...
> config CC_HAVE_SHADOW_CALL_STACK
>        def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
> 
> And then drop CC_IS_CLANG and version check entirely. Thoughts?

That sounds good to me, yes!

Thanks,
Mark.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel