From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753514AbcDUPwF (ORCPT <rfc822;w@1wt.eu>);
	Thu, 21 Apr 2016 11:52:05 -0400
Received: from mail-oi0-f48.google.com ([209.85.218.48]:35895 "EHLO
	mail-oi0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752649AbcDUPwD (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 21 Apr 2016 11:52:03 -0400
MIME-Version: 1.0
In-Reply-To: <9AF9DCC7-8FC4-4A93-B75A-C07B8CD9023A@zytor.com>
References: <1460757793-59020-1-git-send-email-thgarnie@google.com>
	<1460757793-59020-4-git-send-email-thgarnie@google.com>
	<5718D5F0.8010501@oracle.com>
	<9AF9DCC7-8FC4-4A93-B75A-C07B8CD9023A@zytor.com>
Date: Thu, 21 Apr 2016 08:52:01 -0700
Message-ID: <CAJcbSZHoP-B1VD9jkxH_Ma8sy+F9uYYQeormi47VeRSq3qhSOw@mail.gmail.com>
Subject: Re: [RFC v1 3/4] x86, boot: Implement ASLR for kernel memory sections (x86_64)
From: Thomas Garnier <thgarnie@google.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Borislav Petkov <bp@suse.de>, Andy Lutomirski <luto@kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Kees Cook <keescook@chromium.org>, Stephen Smalley <sds@tycho.nsa.gov>,
        Seth Jennings <sjennings@variantweb.net>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Matt Fleming <matt@codeblueprint.co.uk>,
        Toshi Kani <toshi.kani@hpe.com>,
        Alexander Kuleshov <kuleshovmail@gmail.com>,
        Alexander Popov <alpopov@ptsecurity.com>,
        Joerg Roedel <jroedel@suse.de>, Dave Young <dyoung@redhat.com>,
        Baoquan He <bhe@redhat.com>, Dave Hansen <dave.hansen@linux.intel.com>,
        Mark Salter <msalter@redhat.com>, x86@kernel.org,
        LKML <linux-kernel@vger.kernel.org>, linux-doc@vger.kernel.org,
        Greg Thelen <gthelen@google.com>, kernel-hardening@lists.openwall.com
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Apr 21, 2016 at 8:46 AM, H. Peter Anvin <hpa@zytor.com> wrote:
> On April 21, 2016 6:30:24 AM PDT, Boris Ostrovsky <boris.ostrovsky@oracle.com> wrote:
>>
>>
>>On 04/15/2016 06:03 PM, Thomas Garnier wrote:
>>> +void __init kernel_randomize_memory(void)
>>> +{
>>> +    size_t i;
>>> +    unsigned long addr = memory_rand_start;
>>> +    unsigned long padding, rand, mem_tb;
>>> +    struct rnd_state rnd_st;
>>> +    unsigned long remain_padding = memory_rand_end - memory_rand_start;
>>> +
>>> +    if (!kaslr_enabled())
>>> +            return;
>>> +
>>> +    /* Take the additional space when Xen is not active. */
>>> +    if (!xen_domain())
>>> +            page_offset_base -= __XEN_SPACE;
>>
>>This should be !xen_pv_domain(). Xen HVM guests are no different from
>>bare metal as far as address ranges are concerned. (Technically it's
>>probably !xen_pv_domain() && !xen_pvh_domain() but we can ignore PVH
>>for
>>now since it is being replaced by an HVM-type guest)
>>
>>Having said that, I am not sure I understand why page_offset_base is
>>shifted. I thought 0xffff800000000000 - 0xffff87ffffffffff is not
>>supposed to be used by anyone, whether we are running under a
>>hypervisor
>>or not.
>>
>>-boris
>
> That range is reserved for the hypervisor use.

I know, I thought I could use it if no hypervisor was used but might
introduce problems in the future so I will remove it for the next
iteration.

> --
> Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.