From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 29 Jul 2014 18:56:13 +0200 (CEST) Received: from mx1.redhat.com ([209.132.183.28]:32887 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S6816676AbaG2Q4G4WyMM (ORCPT ); Tue, 29 Jul 2014 18:56:06 +0200 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s6TGtxMJ003465 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 29 Jul 2014 12:55:59 -0400 Received: from tranklukator.brq.redhat.com (dhcp-1-191.brq.redhat.com [10.34.1.191]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id s6TGttLp005889; Tue, 29 Jul 2014 12:55:56 -0400 Received: by tranklukator.brq.redhat.com (nbSMTP-1.00) for uid 500 oleg@redhat.com; Tue, 29 Jul 2014 18:54:20 +0200 (CEST) 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) X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 41790 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: oleg@redhat.com Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips 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. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com ([209.132.183.28]:32887 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S6816676AbaG2Q4G4WyMM (ORCPT ); Tue, 29 Jul 2014 18:56:06 +0200 Date: Tue, 29 Jul 2014 18:54:16 +0200 From: Oleg Nesterov 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: Return-Path: Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-subscribe: List-owner: List-post: List-archive: 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" Message-ID: <20140729165416.McXhfYEpNMrJUh6pAyxr-JudQIR2qTQ3T72pMJIw4GQ@z> 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.