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 S1753328AbbIZRWA (ORCPT <rfc822;w@1wt.eu>);
	Sat, 26 Sep 2015 13:22:00 -0400
Received: from terminus.zytor.com ([198.137.202.10]:54623 "EHLO mail.zytor.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1753278AbbIZRVs (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Sat, 26 Sep 2015 13:21:48 -0400
User-Agent: K-9 Mail for Android
In-Reply-To: <CALCETrUeGAedCKcSCvedyooamr6-tyfb3-b3uYDZG+k3Q_v9rw@mail.gmail.com>
References: <1443218539-7610-1-git-send-email-matt@codeblueprint.co.uk> <1443218539-7610-2-git-send-email-matt@codeblueprint.co.uk> <20150926055643.GA25877@gmail.com> <CALCETrUeGAedCKcSCvedyooamr6-tyfb3-b3uYDZG+k3Q_v9rw@mail.gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain;
 charset=UTF-8
Subject: Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Sat, 26 Sep 2015 10:20:22 -0700
To: Andy Lutomirski <luto@amacapital.net>, Ingo Molnar <mingo@kernel.org>
CC: Matt Fleming <matt@codeblueprint.co.uk>,
        Thomas Gleixner <tglx@linutronix.de>,
        Matt Fleming <matt.fleming@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
        "Lee, Chun-Yi" <jlee@suse.com>, Borislav Petkov <bp@suse.de>,
        Leif Lindholm <leif.lindholm@linaro.org>,
        Peter Jones <pjones@redhat.com>, James Bottomley <JBottomley@odin.com>,
        Matthew Garrett <mjg59@srcf.ucam.org>, Dave Young <dyoung@redhat.com>,
        stable <stable@vger.kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
        Denys Vlasenko <dvlasenk@redhat.com>, Brian Gerst <brgerst@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>
Message-ID: <E40EBF14-FD9E-49C0-A7FB-951958F72F79@zytor.com>
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

I think it "works" because the affected BIOSes don't put spaces between the chunks.  I have discussed this with Matt.

On September 26, 2015 10:01:14 AM PDT, Andy Lutomirski <luto@amacapital.net> wrote:
>On Fri, Sep 25, 2015 at 10:56 PM, Ingo Molnar <mingo@kernel.org> wrote:
>>
>> So this commit worries me.
>>
>> This bug is a good find, and the fix is obviously needed and urgent,
>but I'm not
>> sure about the implementation at all. (I've Cc:-ed a few more x86 low
>level
>> gents.)
>>
>> * Matt Fleming <matt@codeblueprint.co.uk> wrote:
>>> +             /*
>>> +              * Starting in UEFI v2.5 the EFI_PROPERTIES_TABLE
>>> +              * config table feature requires us to map all entries
>>> +              * in the same order as they appear in the EFI memory
>>> +              * map. That is to say, entry N must have a lower
>>> +              * virtual address than entry N+1. This is because the
>>> +              * firmware toolchain leaves relative references in
>>> +              * the code/data sections, which are split and become
>>> +              * separate EFI memory regions. Mapping things
>>> +              * out-of-order leads to the firmware accessing
>>> +              * unmapped addresses.
>>> +              *
>
>I'm clearly missing something.  What is EFI doing that it doesn't care
>how big the gap between sections is but it still requires them to be
>in order?  It's not as though x86_64 has an addressing mode that
>allows only non-negative offsets.
>
>--Andy

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