From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755904AbeASO1Q (ORCPT ); Fri, 19 Jan 2018 09:27:16 -0500 Received: from mail-lf0-f65.google.com ([209.85.215.65]:41866 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755020AbeASO1G (ORCPT ); Fri, 19 Jan 2018 09:27:06 -0500 X-Google-Smtp-Source: AH8x225VQGwdfoc9oF56BydO6H2Y+lS5fNyKICkVIMXzdym8gMqo3ePHJXidPR8gsnOqFU1j0l1Hmg== Date: Fri, 19 Jan 2018 17:27:12 +0300 From: Serge Semin To: Matt Redfearn Cc: Florian Fainelli , ralf@linux-mips.org, miodrag.dinic@mips.com, jhogan@kernel.org, goran.ferenc@mips.com, david.daney@cavium.com, paul.gortmaker@windriver.com, paul.burton@mips.com, alex.belits@cavium.com, Steven.Hill@cavium.com, alexander.sverdlin@nokia.com, kumba@gentoo.org, marcin.nowakowski@mips.com, James.hogan@mips.com, Peter.Wotton@mips.com, Sergey.Semin@t-platforms.ru, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 11/14] MIPS: memblock: Print out kernel virtual mem layout Message-ID: <20180119142712.GA3101@mobilestation> References: <20180117222312.14763-1-fancer.lancer@gmail.com> <20180117222312.14763-12-fancer.lancer@gmail.com> <20180118201856.GA996@mobilestation> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 19, 2018 at 07:59:43AM +0000, Matt Redfearn wrote: Hello Matt, > Hi Serge, > > > > On 18/01/18 20:18, Serge Semin wrote: > >On Thu, Jan 18, 2018 at 12:03:03PM -0800, Florian Fainelli wrote: > >>On 01/17/2018 02:23 PM, Serge Semin wrote: > >>>It is useful to have the kernel virtual memory layout printed > >>>at boot time so to have the full information about the booted > >>>kernel. In some cases it might be unsafe to have virtual > >>>addresses freely visible in logs, so the %pK format is used if > >>>one want to hide them. > >>> > >>>Signed-off-by: Serge Semin > >> > >>I personally like having that information because that helps debug and > >>have a quick reference, but there appears to be a trend to remove this > >>in the name of security: > >> > >>https://patchwork.kernel.org/patch/10124007/ > >> > >>maybe hide this behind a configuration option? > > > >Yeah, arm code was the place I picked the function up.) But in my case > >I've used %pK so the pointers would disappear from logging when > >kptr_restrict sysctl is 1 or 2. > >I agree, that we might need to make the printouts optional. If there is > >any kernel config, which for instance increases the kernel security we > >could also use it or anything else to discard the printouts at compile > >time. > > > Certainly, when KASLR is active it would be preferable to hide this > information, so you could use CONFIG_RELOCATABLE. The existing KASLR stuff > additionally hides this kind of information behind CONFIG_DEBUG_KERNEL, so > that only people actively debugging the kernel see it: > > http://elixir.free-electrons.com/linux/v4.15-rc8/source/arch/mips/kernel/setup.c#L604 Ok. I'll hide the printouts behind both of that config macros in the next patchset version. Regards, -Sergey > > Thanks, > Matt > > > > >>-- > >>Florian