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=-2.2 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 A6845C433E0 for ; Thu, 28 May 2020 11:22:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8DF73206F1 for ; Thu, 28 May 2020 11:22:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388346AbgE1LWe (ORCPT ); Thu, 28 May 2020 07:22:34 -0400 Received: from jabberwock.ucw.cz ([46.255.230.98]:58278 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388202AbgE1LWe (ORCPT ); Thu, 28 May 2020 07:22:34 -0400 Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id 4C7001C0351; Thu, 28 May 2020 13:22:32 +0200 (CEST) Date: Thu, 28 May 2020 13:22:31 +0200 From: Pavel Machek To: "Alessandrelli, Daniele" Cc: "arnd@arndb.de" , "robh@kernel.org" , "Murphy, Paul J" , "gregkh@linuxfoundation.org" , "Shevchenko, Andriy" , "linux-kernel@vger.kernel.org" , "daniele.alessandrelli@linux.intel.com" Subject: Re: [PATCH 1/1] soc: keembay: Add Keem Bay IMR driver Message-ID: <20200528112231.GA22054@duo.ucw.cz> References: <13ca92165fab2827b6d439661e75f5b91ef083c2.1587485099.git.daniele.alessandrelli@intel.com> <20200501081002.GA1055721@kroah.com> <20200524212851.GG1192@bug> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="vtzGhvizbBRQ85DL" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --vtzGhvizbBRQ85DL Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > > Agreed, this sounds like an incompatible extension of the boot > > protocol > > that we should otherwise not merge. > >=20 > > However, there is also a lot of missing information here, and it is > > always > > possible they are trying to something for a good reason. As long as > > the > > problem that the bootloader is trying to solve is explained well > > enough > > in the changelog, we can discuss it to see how it should be done > > properly. >=20 >=20 > Apologies, I should have provided more information. Here it is :) >=20 > Basically, at boot time U-Boot code and core memory (.text, .data, > .bss, etc.) is protected by this Isolated Memory Region (IMR) which > prevents any device or processing units other than the ARM CPU to > access/modify the memory. >=20 > This is done for security reasons, to reduce the risks that a potential > attacker can use "hijacked" HW devices to interfere with the boot > process (and break the secure boot flow in place). Dunno. You disable that after boot anyway. Whether it is disabled just before starting kernel or just after it makes very little difference. Plus, I'm not sure if this has much security value at all. If I can corrupt data u-boot works _with_ (such as kernel, dtb), I'll take over the system anyway. IOW I believe the best/simplest way is to simply disable this in u-boot before jumping to kernel entrypoint. Best regards, Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --vtzGhvizbBRQ85DL Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EABECAB0WIQRPfPO7r0eAhk010v0w5/Bqldv68gUCXs+e9wAKCRAw5/Bqldv6 8kTnAJkBCFaIH+RgyEIJB348L5Z1U0EPAwCglTSJuvMLH/LegS0zeGTtaIRLU2s= =U8+S -----END PGP SIGNATURE----- --vtzGhvizbBRQ85DL--