From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f69.google.com (mail-vk0-f69.google.com [209.85.213.69]) by kanga.kvack.org (Postfix) with ESMTP id B609B6B0005 for ; Wed, 14 Feb 2018 17:27:49 -0500 (EST) Received: by mail-vk0-f69.google.com with SMTP id s73so2814619vke.12 for ; Wed, 14 Feb 2018 14:27:49 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id o67sor1011880vkg.23.2018.02.14.14.27.48 for (Google Transport Security); Wed, 14 Feb 2018 14:27:48 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20180214221328.glbrdib3wumve53z@cisco> References: <17e5b515-84c8-dca2-1695-cdf819834ea2@huawei.com> <414027d3-dd73-cf11-dc2a-e8c124591646@redhat.com> <2f23544a-bd24-1e71-967b-e8d1cf5a20a3@redhat.com> <20180214221328.glbrdib3wumve53z@cisco> From: Kees Cook Date: Wed, 14 Feb 2018 14:27:47 -0800 Message-ID: Subject: Re: arm64 physmap (was Re: [kernel-hardening] [PATCH 4/6] Protectable Memory) Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Tycho Andersen Cc: Laura Abbott , Jann Horn , Igor Stoppa , Boris Lukashev , Christopher Lameter , Matthew Wilcox , Jerome Glisse , Michal Hocko , Christoph Hellwig , linux-security-module , Linux-MM , kernel list , Kernel Hardening , linux-arm-kernel On Wed, Feb 14, 2018 at 2:13 PM, Tycho Andersen wrote: > On Wed, Feb 14, 2018 at 11:48:38AM -0800, Kees Cook wrote: >> On Wed, Feb 14, 2018 at 11:06 AM, Laura Abbott wrote: >> > fixed. Modules yes are not fully protected. The conclusion from past >> > experience has been that we cannot safely break down larger page sizes >> > at runtime like x86 does. We could theoretically >> > add support for fixing up the alias if PAGE_POISONING is enabled but >> > I don't know who would actually use that in production. Performance >> > is very poor at that point. >> >> XPFO forces 4K pages on the physmap[1] for similar reasons. I have no >> doubt about performance changes, but I'd be curious to see real >> numbers. Did anyone do benchmarks on just the huge/4K change? (Without >> also the XPFO overhead?) >> >> If this, XPFO, and PAGE_POISONING all need it, I think we have to >> start a closer investigation. :) > > I haven't but it shouldn't be too hard. What benchmarks are you > thinking? Unless I'm looking at some specific micro benchmark, I tend to default to looking at kernel build benchmarks but that gets pretty noisy. Laura regularly uses hackbench, IIRC. I'm not finding the pastebin I had for that, though. I wonder if we need a benchmark subdirectory in tools/testing/, so we could collect some of these common tools? All benchmarks are terrible, but at least we'd have the same terrible benchmarks. :) -Kees -- Kees Cook Pixel Security -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org