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=-7.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,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 E54CDC4360F for ; Thu, 4 Apr 2019 02:18:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B9C44206B6 for ; Thu, 4 Apr 2019 02:18:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726694AbfDDCSk (ORCPT ); Wed, 3 Apr 2019 22:18:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33120 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726167AbfDDCSk (ORCPT ); Wed, 3 Apr 2019 22:18:40 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B9A18309708D; Thu, 4 Apr 2019 02:18:39 +0000 (UTC) Received: from localhost (ovpn-12-46.pek2.redhat.com [10.72.12.46]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 964EF62671; Thu, 4 Apr 2019 02:18:38 +0000 (UTC) Date: Thu, 4 Apr 2019 10:18:35 +0800 From: Baoquan He To: linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com Cc: dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, keescook@chromium.org, thgarnie@google.com Subject: Re: [PATCH v3 0/2] x86/mm/KASLR: Change the granularity of randomization to PUD size in 5-level Message-ID: <20190404021835.GR7627@MiWiFi-R3L-srv> References: <20190308025616.21440-1-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190308025616.21440-1-bhe@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Thu, 04 Apr 2019 02:18:39 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org PING Is there any comment for this patchset, or could we consider to merge them? On 03/08/19 at 10:56am, Baoquan He wrote: > This is v3 post, v2 post is here: > http://lkml.kernel.org/r/20190228003522.9957-1-bhe@redhat.com > v1 can be found here: > http://lkml.kernel.org/r/20190224132231.4878-1-bhe@redhat.com > > Background: > *** > Earlier, during a series of KASLR patch reviewing, Ingo got the current > memory region KASLR only has granularity of randomization in PUD size in > 4-level paging mode, and P4D size in 5-level paging mode, He suggested > me to try to change both of them to be PMD size at granularity: > > http://lkml.kernel.org/r/20180912100135.GB3333@gmail.com > > Later, I changed code to support PMD level of randomization for both > 4-level and 5-level. > > https://github.com/baoquan-he/linux/commits/mm-kaslr-2m-aligned > > The test passed on my KVM guest with 1 GB RAM, but failed when I > increased the RAM to 4 GB, and failed either on larger RAM. > > After analyzing, it's because that 1 GB page mapping need be mapped at 1 > GB aligned physical address for intel CPU. The 2 MB level of randomization > will break it and cause error. Please check below table in intel IA32 manual. > > Table 4-15. Format of an IA-32e Page-Directory-Pointer-Table Entry (PDPTE) that Maps a 1-GByte Page > > So PMD level of randomization for mm KASLR is not doable. > > However, during investigation and testing above code, it turns out that the > current code is misleading to build identity mapping for the real mode > trampoline in case KASLR enabled. From code, only a small area (which is > smaller than 1 MB) need be identity mapped. Please check below patch which > is from above mm-kaslr-2m-aligned patch series. it only builds up 2 MB > identity maping for real mode trampoline, and test passed on machines > with 32 GB RAM of 4-level and on KVM guest of 5-level. > > https://github.com/baoquan-he/linux/commit/e120e67fbf9a5aa818d20084d8dea5b4a27ecf97 > > Result: > Make a patchset to: > 1)change code to only build 1 GB of area for real mode trampoline, > namely only copy one PUD entry where physical address 0 resides; > > 2)improve the randomization granularity of 5-level from P4D size to PUD size. > > Changelog: > v2->v3: > Improve patch 1/2 according to Kirill's comments: > *) Adjust code change of 1/2; > *) Add code comment to explain the two kinds of mapping thing for > real mode; > > v1->v2: > Improve patch according to Kirill's suggestions: > *)Add more information to code comment for better understanding; > *)Improve code to save one low memory page in 4-level; > > Baoquan He (2): > x86/mm/KASLR: Only build one PUD entry of area for real mode > trampoline > x86/mm/KASLR: Change the granularity of randomization to PUD size in > 5-level > > arch/x86/mm/kaslr.c | 98 ++++++++++++++++++++------------------------- > 1 file changed, 43 insertions(+), 55 deletions(-) > > -- > 2.17.2 >