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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 814A8C433FE for ; Mon, 10 Jan 2022 16:20:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237295AbiAJQUM (ORCPT ); Mon, 10 Jan 2022 11:20:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60070 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237046AbiAJQUJ (ORCPT ); Mon, 10 Jan 2022 11:20:09 -0500 Received: from zeniv-ca.linux.org.uk (zeniv-ca.linux.org.uk [IPv6:2607:5300:60:148a::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CA54C06173F; Mon, 10 Jan 2022 08:20:09 -0800 (PST) Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1n6xOt-0013Jc-8T; Mon, 10 Jan 2022 16:20:03 +0000 Date: Mon, 10 Jan 2022 16:20:03 +0000 From: Al Viro To: Geert Uytterhoeven Cc: "Eric W. Biederman" , Linux Kernel Mailing List , Linux-Arch , Linus Torvalds , Oleg Nesterov , Kees Cook , Linux API Subject: Re: [PATCH 08/17] ptrace/m68k: Stop open coding ptrace_report_syscall Message-ID: References: <87r19opkx1.fsf_-_@email.froward.int.ebiederm.org> <20220103213312.9144-8-ebiederm@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 10, 2022 at 04:26:57PM +0100, Geert Uytterhoeven wrote: > On Mon, Jan 3, 2022 at 10:33 PM Eric W. Biederman wrote: > > The generic function ptrace_report_syscall does a little more > > than syscall_trace on m68k. The function ptrace_report_syscall > > stops early if PT_TRACED is not set, it sets ptrace_message, > > and returns the result of fatal_signal_pending. > > > > Setting ptrace_message to a passed in value of 0 is effectively not > > setting ptrace_message, making that additional work a noop. > > > > Returning the result of fatal_signal_pending and letting the caller > > ignore the result becomes a noop in this change. > > > > When a process is ptraced, the flag PT_PTRACED is always set in > > current->ptrace. Testing for PT_PTRACED in ptrace_report_syscall is > > just an optimization to fail early if the process is not ptraced. > > Later on in ptrace_notify, ptrace_stop will test current->ptrace under > > tasklist_lock and skip performing any work if the task is not ptraced. > > > > Cc: Geert Uytterhoeven > > Signed-off-by: "Eric W. Biederman" > > As this depends on the removal of a parameter from > ptrace_report_syscall() earlier in this series: > Acked-by: Geert Uytterhoeven FWIW, I would suggest taking it a bit further: make syscall_trace_enter() and syscall_trace_leave() in m68k ptrace.c unconditional, replace the calls of syscall_trace() in entry.S with syscall_trace_enter() and syscall_trace_leave() resp. and remove syscall_trace(). Geert, do you see any problems with that? The only difference is that current->ptrace_message would be set to 1 for ptrace stop on entry and 2 - on leave. Currently m68k just has it 0 all along. It is user-visible (the whole point is to let the tracer see which stop it is - entry or exit one), so somebody using PTRACE_GETEVENTMSG on syscall stops would start seeing 1 or 2 instead of "0 all along". That's how it works on all other architectures (including m68k-nommu), and I doubt that anything in userland will get broken. Behaviour of PTRACE_GETEVENTMSG for other stops (fork, etc.) remains as-is, of course.