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 264DDC43381 for ; Mon, 18 Mar 2019 17:20:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0272320863 for ; Mon, 18 Mar 2019 17:20:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727426AbfCRRUa (ORCPT ); Mon, 18 Mar 2019 13:20:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11979 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726767AbfCRRU3 (ORCPT ); Mon, 18 Mar 2019 13:20:29 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6443B3082AEE; Mon, 18 Mar 2019 17:20:29 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.34]) by smtp.corp.redhat.com (Postfix) with SMTP id 7D66860FAB; Mon, 18 Mar 2019 17:20:25 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 18 Mar 2019 18:20:29 +0100 (CET) Date: Mon, 18 Mar 2019 18:20:24 +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 Subject: Re: [PATCH v2 4/6] powerpc: use common ptrace_syscall_enter hook to handle _TIF_SYSCALL_EMU Message-ID: <20190318172024.GB23521@redhat.com> References: <20190318104925.16600-1-sudeep.holla@arm.com> <20190318104925.16600-5-sudeep.holla@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190318104925.16600-5-sudeep.holla@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Mon, 18 Mar 2019 17:20:29 +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/powerpc/kernel/ptrace.c > +++ b/arch/powerpc/kernel/ptrace.c > @@ -3278,35 +3278,29 @@ long do_syscall_trace_enter(struct pt_regs *regs) > > user_exit(); > > - flags = READ_ONCE(current_thread_info()->flags) & > - (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE); > - > - if (flags) { > - int rc = tracehook_report_syscall_entry(regs); > + if (unlikely(ptrace_syscall_enter(regs))) { > + /* > + * A nonzero return code from tracehook_report_syscall_entry() > + * tells us to prevent the syscall execution, but we are not > + * going to execute it anyway. > + * > + * Returning -1 will skip the syscall execution. We want to > + * avoid clobbering any registers, so we don't goto the skip > + * label below. > + */ > + return -1; > + } > > - if (unlikely(flags & _TIF_SYSCALL_EMU)) { > - /* > - * A nonzero return code from > - * tracehook_report_syscall_entry() tells us to prevent > - * the syscall execution, but we are not going to > - * execute it anyway. > - * > - * Returning -1 will skip the syscall execution. We want > - * to avoid clobbering any registers, so we don't goto > - * the skip label below. > - */ > - return -1; > - } > + flags = READ_ONCE(current_thread_info()->flags) & _TIF_SYSCALL_TRACE; Why do we need READ_ONCE() with this change? And now that we change a single bit "flags" doesn't look like a good name. Again, to me this patch just makes the code look worse. Honestly, I don't think that the new (badly named) ptrace_syscall_enter() hook makes any sense. Oleg.