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 8FB80C43381 for ; Mon, 18 Mar 2019 15:33:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 65D7620872 for ; Mon, 18 Mar 2019 15:33:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727239AbfCRPd2 (ORCPT ); Mon, 18 Mar 2019 11:33:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34892 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726678AbfCRPd1 (ORCPT ); Mon, 18 Mar 2019 11:33:27 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 988863083391; Mon, 18 Mar 2019 15:33:26 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.34]) by smtp.corp.redhat.com (Postfix) with SMTP id C77CE5D704; Mon, 18 Mar 2019 15:33:22 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 18 Mar 2019 16:33:26 +0100 (CET) Date: Mon, 18 Mar 2019 16:33:22 +0100 From: Oleg Nesterov To: Sudeep Holla 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 Subject: Re: [PATCH v2 3/6] x86: clean up _TIF_SYSCALL_EMU handling using ptrace_syscall_enter hook Message-ID: <20190318153321.GA23521@redhat.com> References: <20190318104925.16600-1-sudeep.holla@arm.com> <20190318104925.16600-4-sudeep.holla@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190318104925.16600-4-sudeep.holla@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Mon, 18 Mar 2019 15:33:27 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; Well, I won't really argue, but to be honest I think this change doesn't make the code better... With this patch tracehook_report_syscall_entry() has 2 callers, to me this just adds some confusion. I agree that the usage of emulated/_TIF_SYSCALL_EMU looks a bit overcomplicated, I'd suggest a simple cleanup below. 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? Oleg. --- x/arch/x86/entry/common.c +++ x/arch/x86/entry/common.c @@ -70,23 +70,18 @@ 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; + work = READ_ONCE(ti->flags); - if (unlikely(work & _TIF_SYSCALL_EMU)) - emulated = true; - - if ((emulated || (work & _TIF_SYSCALL_TRACE)) && - tracehook_report_syscall_entry(regs)) - return -1L; - - if (emulated) - return -1L; + if (work & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) { + ret = tracehook_report_syscall_entry(regs); + if (ret || (work & _TIF_SYSCALL_EMU)) + return -1L; + } #ifdef CONFIG_SECCOMP /*