From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752434AbeADJfd (ORCPT + 1 other); Thu, 4 Jan 2018 04:35:33 -0500 Received: from smtp-fw-6002.amazon.com ([52.95.49.90]:1206 "EHLO smtp-fw-6002.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751653AbeADJfb (ORCPT ); Thu, 4 Jan 2018 04:35:31 -0500 X-Amazon-filename: smime.p7s X-IronPort-AV: E=Sophos;i="5.45,506,1508803200"; d="p7s'?scan'208";a="325414329" Message-ID: <1515058213.12987.89.camel@amazon.co.uk> Subject: Re: [RFC] Retpoline: Binary mitigation for branch-target-injection (aka "Spectre") To: Paul Turner , LKML , "Linus Torvalds" , Greg Kroah-Hartman , Tim Chen , "Dave Hansen" , , Kees Cook , Rik van Riel , Peter Zijlstra , Andy Lutomirski , Jiri Kosina , In-Reply-To: References: Face: 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 Organization: Amazon Content-Type: multipart/signed; micalg=sha-256; protocol="application/x-pkcs7-signature"; boundary="=-Z1biZE/HrMZGwtFxVKde" Date: Thu, 4 Jan 2018 09:30:13 +0000 X-Mailer: Evolution 3.18.5.2-0ubuntu3.2 MIME-Version: 1.0 From: "Woodhouse, David" X-Evolution-Source: 1481217574.17989.4@uc8d3ff76b9bc5848a9cc Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: --=-Z1biZE/HrMZGwtFxVKde Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2018-01-04 at 01:10 -0800, Paul Turner wrote: > Apologies for the discombobulation around today's disclosure.=C2=A0=C2=A0= Obviously the > original goal was to communicate this a little more coherently, but the > unscheduled advances in the disclosure disrupted the efforts to pull this > together more cleanly. >=20 > I wanted to open discussion the "retpoline" approach and and define its > requirements so that we can separate the core > details from questions regarding any particular implementation thereof. >=20 > As a starting point, a full write-up describing the approach is available= at: > =C2=A0 https://support.google.com/faqs/answer/7625886 Note that (ab)using 'ret' in this way is incompatible with CET on upcoming processors. HJ added a -mno-indirect-branch-register option to the latest round of GCC patches, which puts the branch target in a register instead of on the stack. My kernel patches (which I'm about to reconcile with Andi's tweaks and post) do the same. 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