From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A4561C43219 for ; Tue, 30 Apr 2019 16:44:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 814E121670 for ; Tue, 30 Apr 2019 16:44:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726547AbfD3Qo1 (ORCPT ); Tue, 30 Apr 2019 12:44:27 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:50094 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726460AbfD3QoX (ORCPT ); Tue, 30 Apr 2019 12:44:23 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4FF03374; Tue, 30 Apr 2019 09:44:23 -0700 (PDT) Received: from e107155-lin (e107155-lin.cambridge.arm.com [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 170F93F5C1; Tue, 30 Apr 2019 09:44:19 -0700 (PDT) Date: Tue, 30 Apr 2019 17:44:13 +0100 From: Sudeep Holla To: Oleg Nesterov Cc: x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Catalin Marinas , Will Deacon , Paul Mackerras , Michael Ellerman , Thomas Gleixner , Ingo Molnar , Richard Weinberger , jdike@addtoit.com, Steve Capper , Haibo Xu , Bin Lu , Andy Lutomirski , Borislav Petkov , Sudeep Holla Subject: Re: [PATCH v2 3/6] x86: clean up _TIF_SYSCALL_EMU handling using ptrace_syscall_enter hook Message-ID: <20190430164413.GA18913@e107155-lin> References: <20190318104925.16600-1-sudeep.holla@arm.com> <20190318104925.16600-4-sudeep.holla@arm.com> <20190318153321.GA23521@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190318153321.GA23521@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 18, 2019 at 04:33:22PM +0100, Oleg Nesterov wrote: > On 03/18, Sudeep Holla wrote: > > > > --- a/arch/x86/entry/common.c > > +++ b/arch/x86/entry/common.c > > @@ -70,22 +70,16 @@ static long syscall_trace_enter(struct pt_regs *regs) > > > > struct thread_info *ti = current_thread_info(); > > unsigned long ret = 0; > > - bool emulated = false; > > u32 work; > > > > if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) > > BUG_ON(regs != task_pt_regs(current)); > > > > - work = READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY; > > - > > - if (unlikely(work & _TIF_SYSCALL_EMU)) > > - emulated = true; > > - > > - if ((emulated || (work & _TIF_SYSCALL_TRACE)) && > > - tracehook_report_syscall_entry(regs)) > > + if (unlikely(ptrace_syscall_enter(regs))) > > return -1L; > > > > - if (emulated) > > + work = READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY; > > + if ((work & _TIF_SYSCALL_TRACE) && tracehook_report_syscall_entry(regs)) > > return -1L; > [...] > > And it seems that _TIF_WORK_SYSCALL_ENTRY needs some cleanups too... We don't need > "& _TIF_WORK_SYSCALL_ENTRY" in syscall_trace_enter, and _TIF_WORK_SYSCALL_ENTRY > should not include _TIF_NOHZ? > I was about to post the updated version and checked this to make sure I have covered everything or not. I had missed the above comment. All architectures have _TIF_NOHZ in their mask that they check to do work. And from x86, I read "...syscall_trace_enter(). Also includes TIF_NOHZ for enter_from_user_mode()" So I don't understand why _TIF_NOHZ needs to be dropped. Also if we need to drop, we can address that separately examining all archs. I will post the cleanup as you suggested for now. -- Regards, Sudeep