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 S933502AbbFCSTr (ORCPT <rfc822;w@1wt.eu>);
	Wed, 3 Jun 2015 14:19:47 -0400
Received: from terminus.zytor.com ([198.137.202.10]:36544 "EHLO mail.zytor.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S932270AbbFCSTk (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Wed, 3 Jun 2015 14:19:40 -0400
Message-ID: <556F450E.1020902@zytor.com>
Date: Wed, 03 Jun 2015 11:18:54 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0
MIME-Version: 1.0
To: Andy Lutomirski <luto@amacapital.net>, Ingo Molnar <mingo@kernel.org>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Denys Vlasenko <dvlasenk@redhat.com>, Brian Gerst <brgerst@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC PATCH 0/7] x86/entry: Create a home for the x86 entry code
 in arch/x86/entry/
References: <1433350757-14247-1-git-send-email-mingo@kernel.org> <556F3368.5060708@zytor.com> <20150603171100.GB14389@gmail.com> <CALCETrW9Q-edKty9=abv+XKpAqAWVjCwPXiX1xmDifrrWxZPiw@mail.gmail.com> <20150603171650.GA15858@gmail.com> <CALCETrUY80kQ3yiBYn29jZyeZx=P9ZsA+eiq-5kgqLOMiSZJ9g@mail.gmail.com> <556F41A2.7000207@zytor.com>
In-Reply-To: <556F41A2.7000207@zytor.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 06/03/2015 11:04 AM, H. Peter Anvin wrote:
> On 06/03/2015 10:22 AM, Andy Lutomirski wrote:
>>
>> I'm convinced.  If "entry" means entry into code provided by the
>> kernel as opposed to entry via hardware-provided entry mechanism, then
>> the vdso is indeed a pile of entries into the kernel.
>>
> 
> No, it isn't.  It is user space code provided by the kernel.  It is a
> very different beast, and this is highly and unnecessarily confusing.  I
> am thrilled we finally have managed to get the vdso code separated out,
> this just muddles the situation.
> 

So let me clarify this: vdso code is really a kind of system calls, that
just happen to be executed in user space, thus *bypassing* kernel entry.
 We don't want to put all the system call code (or even the x86-specific
ones) in entry/ as that would completely eliminate the point and we have
once again re-invented the kernel/ catch-all.

	-hpa