Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754008AbaG2Q4c (ORCPT ); Tue, 29 Jul 2014 12:56:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58015 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753918AbaG2Q4a (ORCPT ); Tue, 29 Jul 2014 12:56:30 -0400 Date: Tue, 29 Jul 2014 18:54:16 +0200 From: Oleg Nesterov To: Andy Lutomirski Cc: "linux-kernel@vger.kernel.org" , Kees Cook , Will Drewry , X86 ML , "linux-arm-kernel@lists.infradead.org" , Linux MIPS Mailing List , linux-arch , LSM List , Alexei Starovoitov , "H. Peter Anvin" Subject: Re: [PATCH v3 6/8] x86: Split syscall_trace_enter into two phases Message-ID: <20140729165416.GA967@redhat.com> References: <3f649f5658a163645e3ce15156176c325283762e.1405992946.git.luto@amacapital.net> <20140728173723.GA20993@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/28, Andy Lutomirski wrote: > > On Mon, Jul 28, 2014 at 10:37 AM, Oleg Nesterov wrote: > > Hi Andy, > > > > I am really sorry for delay. > > > > This is on top of the recent change from Kees, right? Could me remind me > > where can I found the tree this series based on? So that I could actually > > apply these changes... > > https://git.kernel.org/cgit/linux/kernel/git/kees/linux.git/log/?h=seccomp/fastpath > > The first four patches are already applied there. Thanks! > > If I understand correctly, syscall_trace_enter() can avoid _phase2() above. > > But we should always call user_exit() unconditionally? > > Damnit. I read that every function called by user_exit, and none of > them give any indication of why they're needed for traced syscalls but > not for untraced syscalls. On a second look, it seems that TIF_NOHZ > controls it. Yes, just to trigger the slow path, I guess. > I'll update the code to call user_exit iff TIF_NOHZ is > set. Or perhaps it would be better to not add another user of this (strange) flag and just call user_exit() unconditionally(). But, yes, you need to use from "work = flags & (_TIF_WORK_SYSCALL_ENTRY & ~TIF_NOHZ)" then. > > And we should always set X86_EFLAGS_TF if TIF_SINGLESTEP? IIRC, TF can be > > actually cleared on a 32bit kernel if we step over sysenter insn? > > I don't follow. If TIF_SINGLESTEP, then phase1 will return a nonzero > value, Ah yes, thanks, I missed this. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/