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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 16D6AC43466 for ; Fri, 18 Sep 2020 21:40:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5E8EF2311B for ; Fri, 18 Sep 2020 21:40:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5E8EF2311B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ucw.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 887798E0003; Fri, 18 Sep 2020 17:40:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8105E8E0001; Fri, 18 Sep 2020 17:40:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6D81C8E0003; Fri, 18 Sep 2020 17:40:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0115.hostedemail.com [216.40.44.115]) by kanga.kvack.org (Postfix) with ESMTP id 529998E0001 for ; Fri, 18 Sep 2020 17:40:25 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 0F1983622 for ; Fri, 18 Sep 2020 21:40:25 +0000 (UTC) X-FDA: 77277501210.06.joke60_630c8be2712e Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id E255E1011AC93 for ; Fri, 18 Sep 2020 21:40:24 +0000 (UTC) X-HE-Tag: joke60_630c8be2712e X-Filterd-Recvd-Size: 5415 Received: from jabberwock.ucw.cz (jabberwock.ucw.cz [46.255.230.98]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Fri, 18 Sep 2020 21:40:24 +0000 (UTC) Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id 19EEE1C0B78; Fri, 18 Sep 2020 23:40:21 +0200 (CEST) Date: Fri, 18 Sep 2020 23:40:20 +0200 From: Pavel Machek To: "Yu, Yu-cheng" Cc: Randy Dunlap , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Peter Zijlstra , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang Subject: Re: [PATCH v12 1/8] x86/cet/ibt: Add Kconfig option for user-mode Indirect Branch Tracking Message-ID: <20200918214020.GF4304@duo.ucw.cz> References: <20200918192312.25978-1-yu-cheng.yu@intel.com> <20200918192312.25978-2-yu-cheng.yu@intel.com> <20200918205933.GB4304@duo.ucw.cz> <019b5e45-b116-7f3d-f1f2-3680afbd676c@intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="AH+kv8CCoFf6qPuz" Content-Disposition: inline In-Reply-To: <019b5e45-b116-7f3d-f1f2-3680afbd676c@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: --AH+kv8CCoFf6qPuz Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri 2020-09-18 14:25:12, Yu, Yu-cheng wrote: > On 9/18/2020 1:59 PM, Pavel Machek wrote: > > On Fri 2020-09-18 13:24:13, Randy Dunlap wrote: > > > Hi, > > >=20 > > > If you do another version of this: > > >=20 > > > On 9/18/20 12:23 PM, Yu-cheng Yu wrote: > > > > Introduce Kconfig option X86_INTEL_BRANCH_TRACKING_USER. > > > >=20 > > > > Indirect Branch Tracking (IBT) provides protection against CALL-/JM= P- > > > > oriented programming attacks. It is active when the kernel has this > > > > feature enabled, and the processor and the application support it. > > > > When this feature is enabled, legacy non-IBT applications continue = to > > > > work, but without IBT protection. > > > >=20 > > > > Signed-off-by: Yu-cheng Yu > > > > --- > > > > v10: > > > > - Change build-time CET check to config depends on. > > > >=20 > > > > arch/x86/Kconfig | 16 ++++++++++++++++ > > > > 1 file changed, 16 insertions(+) > > > >=20 > > > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > > > > index 6b6dad011763..b047e0a8d1c2 100644 > > > > --- a/arch/x86/Kconfig > > > > +++ b/arch/x86/Kconfig > > > > @@ -1963,6 +1963,22 @@ config X86_INTEL_SHADOW_STACK_USER > > > > If unsure, say y. > > > > +config X86_INTEL_BRANCH_TRACKING_USER > > > > + prompt "Intel Indirect Branch Tracking for user-mode" > > > > + def_bool n > > > > + depends on CPU_SUP_INTEL && X86_64 > > > > + depends on $(cc-option,-fcf-protection) > > > > + select X86_INTEL_CET > > > > + help > > > > + Indirect Branch Tracking (IBT) provides protection against > > > > + CALL-/JMP-oriented programming attacks. It is active when > > > > + the kernel has this feature enabled, and the processor and > > > > + the application support it. When this feature is enabled, > > > > + legacy non-IBT applications continue to work, but without > > > > + IBT protection. > > > > + > > > > + If unsure, say y > > >=20 > > > If unsure, say y. > >=20 > > Actually, it would be "If unsure, say Y.", to be consistent with the > > rest of the Kconfig. > >=20 > > But I wonder if Yes by default is good idea. Only very new CPUs will > > support this, right? Are they even available at the market? Should the > > help text say "if your CPU is Whatever Lake or newer, ...." :-) ? >=20 > I will revise the wording if there is another version. But a CET-capable > kernel can run on legacy systems. We have been testing that combination. Yes, but enabling CET is unneccessary overhead on older systems. And Kconfig is great place to explain that. Best regards, Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --AH+kv8CCoFf6qPuz Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EABECAB0WIQRPfPO7r0eAhk010v0w5/Bqldv68gUCX2UpRAAKCRAw5/Bqldv6 8tKaAJoCjw1dkJHdYlkUkB4fM1+kRrBkbACfTbioBaGJ8ZtKgM0RqUOnLeG0ipE= =cAzW -----END PGP SIGNATURE----- --AH+kv8CCoFf6qPuz--