From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751719Ab1FHSPJ (ORCPT ); Wed, 8 Jun 2011 14:15:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:4069 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750846Ab1FHSPD (ORCPT ); Wed, 8 Jun 2011 14:15:03 -0400 Subject: Re: [PATCH -v2] Audit: push audit success and retcode into arch ptrace.h From: Eric Paris To: Oleg Nesterov Cc: linux-kernel@vger.kernel.org, tony.luck@intel.com, fenghua.yu@intel.com, monstr@monstr.eu, ralf@linux-mips.org, benh@kernel.crashing.org, paulus@samba.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, linux390@de.ibm.com, lethal@linux-sh.org, davem@davemloft.net, jdike@addtoit.com, richard@nod.at, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, linux-ia64@vger.kernel.org, microblaze-uclinux@itee.uq.edu.au, linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net Date: Wed, 08 Jun 2011 14:13:36 -0400 In-Reply-To: <20110608163653.GA9592@redhat.com> References: <20110603220451.23134.47368.stgit@paris.rdu.redhat.com> <20110607171952.GA25729@redhat.com> <1307472796.2052.12.camel@localhost.localdomain> <20110608163653.GA9592@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Message-ID: <1307556823.2577.5.camel@localhost.localdomain> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2011-06-08 at 18:36 +0200, Oleg Nesterov wrote: > On 06/07, Eric Paris wrote: > > > > On Tue, 2011-06-07 at 19:19 +0200, Oleg Nesterov wrote: > > > > > > With or without this patch, can't we call audit_syscall_exit() twice > > > if there is something else in _TIF_WORK_SYSCALL_EXIT mask apart from > > > SYSCALL_AUDIT ? First time it is called from asm, then from > > > syscall_trace_leave(), no? > > > > > > For example. The task has TIF_SYSCALL_AUDIT and nothing else, it does > > > system_call->auditsys->system_call_fastpath. What if it gets, say, > > > TIF_SYSCALL_TRACE before ret_from_sys_call? > > > > No harm is done calling twice. The first call will do the real work and > > cleanup. It will set a flag in the audit data that the work has been > > done (in_syscall == 0) thus the second call will then not do any real > > work and won't have anything to clean up. > > Hmm... and I assume context->previous != NULL is not possible on x86_64. > OK, thanks. > > And I guess, all CONFIG_AUDITSYSCALL code in entry.S is only needed to > microoptimize the case when TIF_SYSCALL_AUDIT is the only reason for the > slow path. I wonder if it really makes the measureble difference... All I know is what Roland put in the changelog: Avoiding the iret return path when syscall audit is enabled helps performance a lot. I believe this was a result of Fedora starting auditd by default and then Linus bitching about how slow a null syscall in a tight loop was. It was an optimization for a microbenchmark. How much it affects things on a real syscall that does real work is probably going to be determined by how much work is done in the syscall. (or just disable auditd in userspace) -Eric