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=-2.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 23AC4C43331 for ; Mon, 30 Mar 2020 11:33:13 +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 E9C7920733 for ; Mon, 30 Mar 2020 11:33:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="USNNLOx/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E9C7920733 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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-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-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=9EePArAeIQGlkW7ol/ZnrL994YtcisiZusOcAXa3ESo=; b=USNNLOx/edWekplNaEy7Z7ckt lVC8pUzhDPjQdUSnF1bqNzNlC7zkUEW/EKiQA108U6EeTgZemqwop6E3FcC/fx8JOnUjCOzrqgsaU LgS4gYYDCNVQBMjSpoipWz5tNeC7tTkQXBl+UFmCenXcyvBCw+GDnowaEnDkXvzSofg1tkb6YJN5V Iqat5fmh56Fp7QKT+po2+teUPT+RnqxOWM/IzNqQCF8Q5MenYtv0A9QKDL4sMyP8jqbTr8s508olE uVXYjZrgY65SUNht5Xho+JGIf0uXYROSURqzNbimbKsfYUjFdfE5jSUaPyW0nIK8cArN/ZP+r0OkT OPAKOnzEQ==; 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 1jIsfH-0007Bb-VD; Mon, 30 Mar 2020 11:33:11 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jIsfE-0007Ah-M7 for linux-arm-kernel@lists.infradead.org; Mon, 30 Mar 2020 11:33:09 +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 D940A31B; Mon, 30 Mar 2020 04:33:02 -0700 (PDT) Received: from localhost (unknown [10.37.6.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5B5EE3F52E; Mon, 30 Mar 2020 04:33:02 -0700 (PDT) Date: Mon, 30 Mar 2020 12:33:00 +0100 From: Mark Brown To: Kees Cook Subject: Re: [PATCH 1/5] arm64: bti: Support building kernel C code using BTI Message-ID: <20200330113300.GD4792@sirena.org.uk> References: <20200327192107.18394-1-broonie@kernel.org> <20200327192107.18394-2-broonie@kernel.org> <202003281348.B5ECC9DB2@keescook> MIME-Version: 1.0 In-Reply-To: <202003281348.B5ECC9DB2@keescook> X-Cookie: Ahead warp factor one, Mr. Sulu. User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200330_043308_767898_6377DE3F X-CRM114-Status: GOOD ( 14.29 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: multipart/mixed; boundary="===============5061787018348439053==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============5061787018348439053== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="vni90+aGYgRvsTuO" Content-Disposition: inline --vni90+aGYgRvsTuO Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Sat, Mar 28, 2020 at 02:14:09PM -0700, Kees Cook wrote: > On Fri, Mar 27, 2020 at 07:21:03PM +0000, Mark Brown wrote: > > When running with BTI enabled we need to ask the compiler to enable > > generation of BTI landing pads beyond those generated as a result of > > pointer authentication instructions being landing pads. Since the two > > features are practically speaking unlikely to be used separately we > > will make kernel mode BTI depend on pointer authentication in order > > to simplify the Makefile. > Some vendors have been making chips with weird combinations of features. > Is there a better justification to use beyond "unlikely"? The design intent is that BTI is complementary to PAC so it would be a peculiar implementation choice to do BTI without also doing PAC but yes, implementors and system integrators have the freedom to innovate in ways that we cannot always forsee. The other bit of it is that there's fairly limited overhead from running PAC enabled code on hardware without the support. > The compiler appears to accept a leading +, so how about: ... > Or, this is all overkill. :) I feel better about adding the extra dependency than feeding an option to the compiler that looks wrong like -mbranch-protection=+bti (more BTI!) but ultimately I don't have strong feelings either way so whatever Catalin and Will prefer. --vni90+aGYgRvsTuO Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAl6B2OwACgkQJNaLcl1U h9APIgf/cISGK7SQjDmMhVW5kKagg9IJoJaSpsZe5tippg/qIhoVJzRdIswLy0fR HJmu1IH5b7vtK4oMzkOmrpC/xczRJkGqQ8fuK0mWuq3Lzwn20+l1s62CBvmsFe7C HqvcH3/UDbWFE7UyUvRQYfzYOQTERiIXPPTXbiq9kNTb7BacZidu3gAEpvPhY3MA /Qq/i1rIBGSXRoEOyZNz0/kxmDJmFyLYzuZuIYWrJqOsxYvKyPYBlmClt4Sm6xpg zCauDL3Zo5rkQP6K916/kAIsbohhsvr/Lse8BY7w0CCYWjBWUC0lYJX6sIU/xoC2 6MxleaN0Fy0J4kQDubbVceEMAuo7Gw== =iX3m -----END PGP SIGNATURE----- --vni90+aGYgRvsTuO-- --===============5061787018348439053== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============5061787018348439053==--