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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 49045C43441 for ; Tue, 27 Nov 2018 02:54:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E7B420664 for ; Tue, 27 Nov 2018 02:54:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1E7B420664 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=altlinux.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728392AbeK0NuX (ORCPT ); Tue, 27 Nov 2018 08:50:23 -0500 Received: from air.basealt.ru ([194.107.17.39]:54672 "EHLO air.basealt.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727542AbeK0NuX (ORCPT ); Tue, 27 Nov 2018 08:50:23 -0500 Received: by air.basealt.ru (Postfix, from userid 490) id 030A6589AE9; Tue, 27 Nov 2018 02:53:59 +0000 (UTC) Received: from akathisia (broadband-46-188-15-144.2com.net [46.188.15.144]) by air.basealt.ru (Postfix) with ESMTPSA id 4C771589AE7; Tue, 27 Nov 2018 02:53:58 +0000 (UTC) Date: Tue, 27 Nov 2018 03:53:57 +0100 From: Elvira Khabirova To: Oleg Nesterov Cc: rostedt@goodmis.org, mingo@redhat.com, linux-kernel@vger.kernel.org, ldv@altlinux.org, esyr@redhat.com, luto@kernel.org, strace-devel@lists.strace.io, linux-api@vger.kernel.org Subject: Re: [PATCH RESEND v3 1/3] ptrace: pass type of a syscall-stop in ptrace_message Message-ID: <20181127035357.0b381323@akathisia> In-Reply-To: <20181126145643.GD1660@redhat.com> References: <20181125022150.46258a20@akathisia> <20181125022227.55e8caf7@akathisia> <20181126145643.GD1660@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 26 Nov 2018 15:56:43 +0100 Oleg Nesterov wrote: > On 11/25, Elvira Khabirova wrote: > > > > + * These values are stored in task->ptrace_message by tracehook_report_syscall_* > > + * to describe current syscall-stop. > > + * > > + * Values for these constants are chosen so that they do not appear > > + * in task->ptrace_message by other means. > > + */ > > +#define PTRACE_EVENTMSG_SYSCALL_ENTRY 0x80000000U > > +#define PTRACE_EVENTMSG_SYSCALL_EXIT 0x90000000U > > Stupid question, why not > > #define PTRACE_EVENT_SYSCALL_ENTRY 8 > #define PTRACE_EVENT_SYSCALL_EXIT 9 > > right after other PTRACE_EVENT_* constants? I thought about adding new events for syscall {entry,exit}. For tracers, using new events means setting new options and checking for new values after waitpid(). They will also have to switch from using PTRACE_SYSCALL to PTRACE_CONT. Right now (with this version of the patch) tracers can use PTRACE_GETEVENTMSG without doing any additional configuration. More importantly, adding these events would require much more complex modifications of kernel code than this patch does. The only benefit I see from adding these events instead of letting syscall-stops put a value in ptrace_message is an ability to subscribe to syscall entries, but not to exits, and vice-versa, and I don't think it is worth it.