From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757178AbbICVIn (ORCPT ); Thu, 3 Sep 2015 17:08:43 -0400 Received: from mail-ig0-f180.google.com ([209.85.213.180]:37391 "EHLO mail-ig0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756745AbbICVIl (ORCPT ); Thu, 3 Sep 2015 17:08:41 -0400 MIME-Version: 1.0 In-Reply-To: References: <20150813005519.GA11696@www.outflux.net> <20150813022336.GA26334@x> Date: Thu, 3 Sep 2015 14:08:40 -0700 X-Google-Sender-Auth: MRY_jAObitBBRbXiv870wTu6alQ Message-ID: Subject: Re: [PATCH] x86, vsyscall: add CONFIG to control default From: Kees Cook To: Thomas Gleixner , "H. Peter Anvin" , Ingo Molnar Cc: Josh Triplett , Andy Lutomirski , "x86@kernel.org" , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 31, 2015 at 2:23 PM, Andy Lutomirski wrote: > On Aug 31, 2015 1:13 PM, "Kees Cook" wrote: >> >> On Wed, Aug 12, 2015 at 7:23 PM, Josh Triplett wrote: >> > On Wed, Aug 12, 2015 at 05:55:19PM -0700, Kees Cook wrote: >> >> Most modern systems can run with vsyscall=none. In an effort to provide >> >> a way for build-time defaults to lack legacy settings, this adds a new >> >> CONFIG to select the type of vsyscall mapping to use, similar to the >> >> existing "vsyscall" command line parameter. >> >> >> >> Signed-off-by: Kees Cook >> > >> > Seems reasonable to me. One question, though: is there *any* reason to >> > choose "native" over "emulate"? (Does "emulate" have a sufficient >> > performance penalty to matter, and do people running old glibc really >> > care about that performance while still not wanting to upgrade?) >> > If there is a reason, could you please document it in the >> > descriptions of the "native" and "emulate" options (as an upside and a >> > downside, respectively)? If there isn't, you might consider a patch to >> > remove "native". >> >> I think "native" is available out of an abundance of caution. Andy >> left it available, though I'm not sure if he had plans to remove >> "native" entirely. > > Native adds almost no code and almost no maintenance burden -- it's > really just a PTE bit. > >> >> Can someone from the x86 tree take this patch, or are there other >> things to improve? > > It looks good to me. tglx, hpa, ingo? Can this go into -tip? Thanks! -Kees -- Kees Cook Chrome OS Security