From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932828AbaFPWBS (ORCPT ); Mon, 16 Jun 2014 18:01:18 -0400 Received: from mail-ve0-f177.google.com ([209.85.128.177]:61284 "EHLO mail-ve0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932101AbaFPWBO (ORCPT ); Mon, 16 Jun 2014 18:01:14 -0400 MIME-Version: 1.0 In-Reply-To: <539F6889.8040103@zytor.com> References: <539F1C59.6070308@gmx.de> <539F297F.7010904@nod.at> <539F2B2D.6050105@gmx.de> <539F3077.7040005@gmx.de> <539F35A0.2050002@gmx.de> <539F567F.2050802@gmx.de> <539F5702.5050104@nod.at> <539F6646.4040605@zytor.com> <539F6889.8040103@zytor.com> From: Andy Lutomirski Date: Mon, 16 Jun 2014 15:00:53 -0700 Message-ID: Subject: Re: 3.15: kernel BUG at kernel/auditsc.c:1525! To: "H. Peter Anvin" Cc: Richard Weinberger , X86 ML , =?UTF-8?Q?Toralf_F=C3=B6rster?= , Eric Paris , Linux Kernel 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, Jun 16, 2014 at 2:58 PM, H. Peter Anvin wrote: >> >> For 64-bit, I want to do this instead: >> >> https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=x86/seccomp-fastpath&id=a5ec2d7af2c54b55fc7201fa662138b53fbbda39 >> >> I see no reason why the 64-bit badsys code needs its own code path at >> all. I haven't sent it yet because AFAICT it doesn't fix any bug, and >> the series it's a part of isn't ready. >> >> I'm also contemplating rewriting the 64-bit syscall entry work path in C. >> > > Cute... although it still leaves an extra branch for the badsys. It > might perform better than a cmov, but it might not. I bet that the branch is faster in most cases -- I'd be somewhat surprised if CPUs can speculate through a cmov, and that value is needed for control flow almost immediately. --Andy