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 512E0C0044C for ; Wed, 7 Nov 2018 11:21:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 208DC208E7 for ; Wed, 7 Nov 2018 11:21:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 208DC208E7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1730924AbeKGUvD (ORCPT ); Wed, 7 Nov 2018 15:51:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51168 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726225AbeKGUvD (ORCPT ); Wed, 7 Nov 2018 15:51:03 -0500 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 989702D7E8; Wed, 7 Nov 2018 11:21:07 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.31]) by smtp.corp.redhat.com (Postfix) with SMTP id D1F075D75C; Wed, 7 Nov 2018 11:21:01 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 7 Nov 2018 12:21:07 +0100 (CET) Date: Wed, 7 Nov 2018 12:21:01 +0100 From: Oleg Nesterov To: Elvira Khabirova 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 Subject: Re: [RFC PATCH] ptrace: add PTRACE_GET_SYSCALL_INFO request Message-ID: <20181107112100.GA20419@redhat.com> References: <20181107042751.3b519062@akathisia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181107042751.3b519062@akathisia> 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 [10.5.110.30]); Wed, 07 Nov 2018 11:21:08 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/07, Elvira Khabirova wrote: > > In short, if a 64-bit task performs a syscall through int 0x80, its tracer > has no reliable means to find out that the syscall was, in fact, > a compat syscall, and misidentifies it. > * Syscall-enter-stop and syscall-exit-stop look the same for the tracer. Yes, this was discussed many times... So perhaps it makes sense to encode compat/is_enter in ->ptrace_message, debugger can use PTRACE_GETEVENTMSG to get this info. > Secondly, ptracers also have to support a lot of arch-specific code for > obtaining information about the tracee. For some architectures, this > requires a ptrace(PTRACE_PEEKUSER, ...) invocation for every syscall > argument and return value. I am not sure about this change... I won't really argue, but imo this needs a separate patch. > +#define PT_IN_SYSCALL_STOP 0x00000004 /* task is in a syscall-stop */ ... > -static inline int ptrace_report_syscall(struct pt_regs *regs) > +static inline int ptrace_report_syscall(struct pt_regs *regs, > + unsigned long message) > { > int ptrace = current->ptrace; > > if (!(ptrace & PT_PTRACED)) > return 0; > + current->ptrace |= PT_IN_SYSCALL_STOP; > > + current->ptrace_message = message; > ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0)); > > /* > @@ -76,6 +79,7 @@ static inline int ptrace_report_syscall(struct pt_regs *regs) > current->exit_code = 0; > } > > + current->ptrace &= ~PT_IN_SYSCALL_STOP; > return fatal_signal_pending(current); ... > + case PTRACE_GET_SYSCALL_INFO: > + if (child->ptrace & PT_IN_SYSCALL_STOP) > + ret = ptrace_get_syscall(child, datavp); > + break; Why? If debugger uses PTRACE_O_TRACESYSGOOD it can know if the tracee reported syscall entry/exit or not. PTRACE_GET_SYSCALL_INFO is pointless if not, but nothing bad can happen. Oleg.