From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762454AbdADB6D (ORCPT ); Tue, 3 Jan 2017 20:58:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42372 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752664AbdADB5y (ORCPT ); Tue, 3 Jan 2017 20:57:54 -0500 Date: Wed, 4 Jan 2017 09:57:45 +0800 From: Baoquan He To: Dan Williams , Dave Jiang Cc: Ingo Molnar , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , X86 ML , david , "linux-kernel@vger.kernel.org" , "linux-nvdimm@lists.01.org" , Kees Cook , dyoung@redhat.com Subject: Re: [PATCH] x86: fix kaslr and memmap collision Message-ID: <20170104015745.GB15788@x1> References: <147977413859.13657.2181994710415174471.stgit@djiang5-desk3.ch.intel.com> <20161122084754.GA25596@gmail.com> <20170103083137.GA15788@x1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.0 (2016-08-17) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Wed, 04 Jan 2017 01:57:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/03/17 at 01:15pm, Dave Jiang wrote: > > > On 01/03/2017 11:24 AM, Dan Williams wrote: > > On Tue, Jan 3, 2017 at 12:31 AM, Baoquan He wrote: > >> Hi Dan, > >> > >> On 11/22/16 at 09:26am, Dan Williams wrote: > >>> [ replying for Dave since he's offline today and tomorrow ] > >>> > >>> On Tue, Nov 22, 2016 at 12:47 AM, Ingo Molnar wrote: > >>>> > >>>> * Dave Jiang wrote: > >>>> > >>>>> CONFIG_RANDOMIZE_BASE relocates the kernel to a random base address. > >>>>> However it does not take into account the memmap= parameter passed in from > >>>>> the kernel commandline. > >>>> > >>>> memmap= parameters are often used as a list. > >>>> > >>>>> [...] This results in the kernel sometimes being put in the middle of the user > >>>>> memmap. [...] > >>>> > >>>> What does this mean? If memmap= is used to re-define the memory map then the > >>>> kernel getting in the middle of a RAM area is what we want, isn't it? What we > >>>> don't want is for the kernel to get into reserved areas, right? > >>> > >>> Right, this is about teaching kaslr to not land the kernel in newly > >>> defined reserved regions that were not marked reserved in the initial > >>> e820 map from platform firmware. > >> > >> If only tell kaslr to not land kernel in newly defined reserved regions, > >> memory added by "memmap=nn[KMG]@ss[KMG]" should not be avoided since > >> it's usable memory. Kernel randomized into this region is also what we > >> want. Not sure if I understand it right. > > > > You're right, this is supposed to be for memmap=nn!ss cases which > > defines reserved persistent memory ranges, not memmap=nn@ss which > > defines usable memory. > > > > We need to fix mem_avoid_memmap() to only skip memmap= statements that > > specify reserved memory. Thanks for confirmation, Dan! > > > > I think nn@ss is the only one that we should skip over, otherwise > everything else looks like should be avoided. I'll update. Hi Dave, I guess your purpose is to avoid the user defined reserved memory and pmem which I am not very sure about since kaslr won't stamp on ACPI region reported by BIOS. Seems OK to avoid them all except of nn@ss. I have other concerns, will directly comment in your v4 post. Thanks Baoquan