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 X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 69216C43331 for ; Wed, 1 Apr 2020 18:07:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2CED82071A for ; Wed, 1 Apr 2020 18:07:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585764445; bh=hdyhXSXJP/U4prbY3ryjP91yeUA5+HpRAN5/3Wg2CJo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=EAoh1jVYRa8xMdTIM0f8SFjEE/eTuGt4K6rLEF4ESToExKerddLETw9eiZ2X9vRhr QfV6LlcYZC7bUv8xCVwJ0W89ouu2n/9+dSE75UqyK15XcW+hzbpw9nQiXdYlMpBbhi gK6ecB8rvVoR8sZz0ZMSHaUJKlE43qsN0PIGx3Ew= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732723AbgDASHY (ORCPT ); Wed, 1 Apr 2020 14:07:24 -0400 Received: from foss.arm.com ([217.140.110.172]:58332 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732121AbgDASHY (ORCPT ); Wed, 1 Apr 2020 14:07:24 -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 F1EC41FB; Wed, 1 Apr 2020 11:07:23 -0700 (PDT) Received: from localhost (unknown [10.37.6.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 759483F52E; Wed, 1 Apr 2020 11:07:23 -0700 (PDT) Date: Wed, 1 Apr 2020 19:07:21 +0100 From: Mark Brown To: Catalin Marinas Cc: Will Deacon , Mark Rutland , Amit Kachhap , Kees Cook , "linux-arm-kernel@lists.infradead.org" , Szabolcs Nagy , "stable@vger.kernel.org" Subject: Re: [PATCH] arm64: Always force a branch protection mode when the compiler has one Message-ID: <20200401180721.GG4943@sirena.org.uk> References: <20200331194459.54740-1-broonie@kernel.org> <20200401175444.GF9434@mbp> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="bajzpZikUji1w+G9" Content-Disposition: inline In-Reply-To: <20200401175444.GF9434@mbp> X-Cookie: The Ranger isn't gonna like it, Yogi. User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org --bajzpZikUji1w+G9 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Apr 01, 2020 at 06:54:44PM +0100, Catalin Marinas wrote: > On Tue, Mar 31, 2020 at 08:44:59PM +0100, Mark Brown wrote: > > Compilers with branch protection support can be configured to enable it by > > default, it is likely that distributions will do this as part of deploying > > branch protection system wide. As well as the slight overhead from having > > some extra NOPs for unused branch protection features this can cause more > > serious problems when the kernel is providing pointer authentication to > > userspace but not built for pointer authentication itself. > With 5.7 you won't be able to configure user and kernel PAC support > independently. So, I guess that's something only for prior kernel > versions. Yes, it's really for the benefit of stable at this point - hence the Cc. Going forward it's hopefully more for defensiveness than anything else, it's possible something similar might come up with some future stuff but ideally not. --bajzpZikUji1w+G9 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEyBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAl6E2FkACgkQJNaLcl1U h9AvZAf4kcawmHf3KjTLz/Ml0UjkQlK6IiE5hl/jqyojdkmbqJ6vdmNYVpxdGRZv jXhRkAf8jc6tuNYEJESXynxGqqygMkn46iMlBKpNRjNcs9niJoI5Xsc8cxczlyMD RyPLCVtV0rGCXUbCqprcZc+0OvIXavtvAGPiOW+A1uoqKmBjY8EzJOheTJPCmGxj 3RgoWrHUHfDs9UnAlSleC9HdpI1o2x+H8T6pW8lw1jKwgx7O1kGSbv/EFXWcFfqT wOGT+/QHawC2xC1GHO4hzOvq7Ao9pF4jBEAmZAxQVUgknxumFQJlSviubg8lGKxe 4jkQAXQgBy3YGWhzdW37lSBfpHaH =5eIU -----END PGP SIGNATURE----- --bajzpZikUji1w+G9--