From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-x244.google.com (mail-lf0-x244.google.com [IPv6:2a00:1450:4010:c07::244]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 672273B2A4 for ; Thu, 4 Jan 2018 16:20:49 -0500 (EST) Received: by mail-lf0-x244.google.com with SMTP id f3so3171680lfe.4 for ; Thu, 04 Jan 2018 13:20:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=MHzorKwx/wgWFDcL0LLaglJc+AwgvgvfIjhtlYi7KyE=; b=nvG3cb5IgDoSzxjSriOGSHbiD4YWZNbvMI07FuUEPyrFCOeAlaS9nF3x+HN7y3wDnW /qELEgiJFBUu3s43gg2IUaT/RcxbClyB+7SVVRh2Hml1FPHPtzGYyNaNY7c5VAroLF33 z8NQbKtzxFTYixkXAwqpRGgbTACJRyzBGjHY4Gyj2jX+eF0drhmgRM1Tez7+7YlSZ/Tt SvsxFxl2O0np70HrIxCF0aXias3Zg/iVdo8etQsNhMHLtzTBJY4ECNc/Ak8Vi/4+a4uf /ri0nrkQl4UECbToPEpn08k083jiAJvTX8huofVDuvosp3prCOz2zDft8S2jOPxqvWqR DJtw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=MHzorKwx/wgWFDcL0LLaglJc+AwgvgvfIjhtlYi7KyE=; b=bd5jbcn6IKn7YnPs+J/i1ur0HzMdwUippP23lV1Csw6xnUBsBfN755siz6bntSu88V xYBkjqQHrYtN5j2HuJ3IgsCrEunXnXbQPLprD7BEH3LQXaCRriN/Kx5hKsxF2EUHBnx1 M2QRM0DAPppqqzkp5iH1Rbkb3Z1gwPHAgHYDb0M33neKsQuNrzxKQq4arlwtp4B6NDL7 ntF3zneBmc6gXzVhZlSXpnBm2lbp5gLMi8+MTp3MUtzG2yIzuKvKs6ehqMn+BfgdxUC+ M0Jz8/bR+EVNtsFZ5uM2LLz9iAZUDePH7S3rhzAjUxgIdQhUF87gbiKWbinaQu7rPMYx k1Ig== X-Gm-Message-State: AKwxytedUmcEl5ak+Tldpb8f9GPqUEa5zimny3UZscxFVnEWd/mI1btH SZ8QOB+Ub+0EoGAiwA4aoCI= X-Google-Smtp-Source: ACJfBouMXqrJnKcEnxgt4R+gJekmOAvoDR/ibYJxpshz1n9NkTznqNjkDONaPo6iuts+RBBKIWXS2g== X-Received: by 10.25.22.195 with SMTP id 64mr423036lfw.21.1515100848098; Thu, 04 Jan 2018 13:20:48 -0800 (PST) Received: from [192.168.239.216] (mobile-access-bceee7-52.dhcp.inet.fi. [188.238.231.52]) by smtp.gmail.com with ESMTPSA id x84sm760947lff.70.2018.01.04.13.20.46 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 04 Jan 2018 13:20:47 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.2 \(3445.5.20\)) From: Jonathan Morton X-Priority: 3 (Normal) In-Reply-To: <1515097734.30384822@apps.rackspace.com> Date: Thu, 4 Jan 2018 23:20:45 +0200 Cc: Dave Taht , cerowrt-devel@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: References: <2D7460E1-C724-4DAE-86CA-2D48AB2DAFE5@gmail.com> <1515097734.30384822@apps.rackspace.com> To: "dpreed@deepplum.com" X-Mailer: Apple Mail (2.3445.5.20) Subject: Re: [Cerowrt-devel] KASLR: Do we have to worry about other arches than x86? X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 04 Jan 2018 21:20:49 -0000 > On 4 Jan, 2018, at 10:28 pm, dpreed@deepplum.com wrote: >=20 > The really core issue with Meltdown at the highest level is that the = kernel is addressable from userspace, except for the "privilege level" = in the page table entries. That's a couple of bits between userspace and = data that userspace isn't supposed to ever see. And those bits are = ignored during specutlative execution's memory accesses. ...on Intel CPUs since Nehalem and Silvermont, and on a very small = number of ARM's highest-performance cores (which you're unlikely to find = in CPE). But not on most ARM cores, nor on AMD CPUs. These all do their security = checks more promptly, so the rogue data never reaches either a shadow = register nor an execution unit, even under speculative execution. The conceptually simplest mitigation turns out to be switching off = branch prediction. - Jonathan Morton