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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 B05C3C43334 for ; Mon, 3 Sep 2018 14:52:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C99620652 for ; Mon, 3 Sep 2018 14:52:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5C99620652 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726711AbeICTMs (ORCPT ); Mon, 3 Sep 2018 15:12:48 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:35774 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725949AbeICTMs (ORCPT ); Mon, 3 Sep 2018 15:12:48 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B2DDC87A50; Mon, 3 Sep 2018 14:52:17 +0000 (UTC) Received: from localhost (ovpn-8-16.pek2.redhat.com [10.72.8.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DBA4A2026D6B; Mon, 3 Sep 2018 14:52:16 +0000 (UTC) Date: Mon, 3 Sep 2018 22:52:13 +0800 From: Baoquan He To: "Kirill A. Shutemov" Cc: tglx@linutronix.de, mingo@kernel.org, hpa@zytor.com, thgarnie@google.com, kirill.shutemov@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] x86/mm/KASLR: Adjust the vmemmap size according to paging mode Message-ID: <20180903145213.GG1740@192.168.1.3> References: <20180829021754.21850-1-bhe@redhat.com> <20180829021754.21850-2-bhe@redhat.com> <20180829120530.6dhgsautjjrj4ztt@kshutemo-mobl1> <20180830152512.GE14702@192.168.1.2> <20180902205242.kcpt6wsatacahswp@kshutemo-mobl1> <20180903074718.GD1740@192.168.1.3> <20180903102642.rmzawwqsqjvh2mkb@kshutemo-mobl1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180903102642.rmzawwqsqjvh2mkb@kshutemo-mobl1> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Mon, 03 Sep 2018 14:52:17 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Mon, 03 Sep 2018 14:52:17 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'bhe@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/03/18 at 01:26pm, Kirill A. Shutemov wrote: > On Mon, Sep 03, 2018 at 03:47:18PM +0800, Baoquan He wrote: > > On 09/02/18 at 11:52pm, Kirill A. Shutemov wrote: > > > On Thu, Aug 30, 2018 at 11:25:12PM +0800, Baoquan He wrote: > > > > Hi Kirill, > > > > > > > > I made a new version according to your suggestion, just a little > > > > different, I didn't make 1TB as default, just calculate with the actual > > > > size, then align up to 1TB boundary. Just found kcore is printing more > > > > entries than before, I thought it's caused by my code, later got it was > > > > touchde by other people. > > > > > > > > Any comment about this? I can change accordingly. > > > > > > Looks good to me. > > > > > > But there's corner case when struct page is unreasonably large and > > > vmemmap_size will be way to large. We probably have to report an error if > > > we cannot fit vmemmap properly into virtual memory layout. > > > > Hmm, sizeof(struct page) can't exceed one whole page surely, otherwise > > system bootup can't go over vmemmap initlization. Except of this, we may > > need think about the virtual memory layout which vmemmap can be allowed > > to occupy. > > > > If KASAN enabled, KASLR disabled, > > 4-level 1TB + 1TB hole (2TB) > > 5-level 512TB + 2034TB hole (2.5PB) > > > > If KASAN disabled, KASLR enabled, > > 4-level 1TB + 1TB hole + 16TB (18TB) > > 5-level 512TB + 2034TB hole + 8PB (10.5PB) > > > > So, as you can see, if add check in memory KASLR code, we should only > > consider KASLR enabled case. We possibly don't need to worry about > > 5-level case since the size 10.5PB is even bigger than the maximum > > physical RAM mapping size. For 4-level, 18TB align to multiples of 2, it > > will be 32 times of the current 1TB, then we usually assume 64 as the > > default value of sizeof(struct page), then 64*32 == 1024. So we can add > > check like this, what do you think? Or any other idea? > > Looks reasonable to me. > > But I would have the BUILD_BUG_ON() in generic code. If you struct page is > more than 1/4 of PAGE_SIZE something is horribly broken. Just the 1/4 of PAGE_SIZE is based on analysis of KASLR case. If non-KASLR case, it may not be that value. Not sure if it's OK to put it in generic code, and haven't thought of a good place, maybe in setup_arch(), just at the beginning? > > > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > > index 1db8e166455e..776ec759a87c 100644 > > --- a/arch/x86/mm/kaslr.c > > +++ b/arch/x86/mm/kaslr.c > > @@ -90,6 +90,7 @@ void __init kernel_randomize_memory(void) > > BUILD_BUG_ON(vaddr_start >= vaddr_end); > > BUILD_BUG_ON(vaddr_end != CPU_ENTRY_AREA_BASE); > > BUILD_BUG_ON(vaddr_end > __START_KERNEL_map); > > + BUILD_BUG_ON(sizeof(struct page ) > PAGE_SIZE/4); > > Nitpick: redundant space before ')'. > > > > > if (!kaslr_memory_enabled()) > > return; > > > > > > For 5-level paging mode, we > > may not need to worry about that. Since KASAN > > > > ***4-level*** > > ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB) > > ... unused hole ... > > ffffec0000000000 - fffffbffffffffff (=44 bits) kasan shadow memory (16TB) > > ... unused hole ... > > > > > > > > ***5-level*** > > ffd4000000000000 - ffd5ffffffffffff (=49 bits) virtual memory map (512TB) > > ... unused hole ... > > ffdf000000000000 - fffffc0000000000 (=53 bits) kasan shadow memory (8PB) > > > > > > > > -- > > > Kirill A. Shutemov > > -- > Kirill A. Shutemov