From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266277AbUGAUfN (ORCPT ); Thu, 1 Jul 2004 16:35:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266274AbUGAUfN (ORCPT ); Thu, 1 Jul 2004 16:35:13 -0400 Received: from nevyn.them.org ([66.93.172.17]:1439 "EHLO nevyn.them.org") by vger.kernel.org with ESMTP id S266277AbUGAUfE (ORCPT ); Thu, 1 Jul 2004 16:35:04 -0400 Date: Thu, 1 Jul 2004 16:34:56 -0400 From: Daniel Jacobowitz To: Roland McGrath Cc: Davide Libenzi , Andrew Morton , Linus Torvalds , mingo@redhat.com, cagney@redhat.com, Linux Kernel Mailing List Subject: Re: [RFC PATCH] x86 single-step (TF) vs system calls & traps Message-ID: <20040701203455.GA22888@nevyn.them.org> Mail-Followup-To: Roland McGrath , Davide Libenzi , Andrew Morton , Linus Torvalds , mingo@redhat.com, cagney@redhat.com, Linux Kernel Mailing List References: <200407010747.i617lxIB019894@magilla.sf.frob.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200407010747.i617lxIB019894@magilla.sf.frob.com> User-Agent: Mutt/1.5.5.1+cvs20040105i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 01, 2004 at 12:47:59AM -0700, Roland McGrath wrote: > > Roland, I don't think (pretty sure actually ;) we can handle the case > > where TF is set from userspace and, at the same time, the user uses > > PTRACE_SINGLESTEP. > > I don't know where you pulled the notion of that case from. I certainly > never mentioned it. When I raised the case of user-mode setting of TF, I > was quite clear that it's a case when ptrace is not involved. > > > The PTRACE_SINGLESTEP gives you the SYSGOOD behaviour, if you set it. And > > sends a SIGTRAP notification to the ptrace'ing parent process. > > Like I said before, that is a change in the behavior. Since its inception, > SYSGOOD has meant exactly and only that when you use PTRACE_SYSCALL you > will get a different notification for a syscall-tracing stop than other > sources of SIGTRAP that may arise during execution of user code between > system calls. At no time ever before, has it been possible to get the > SIGTRAP|0x80 wait result when you had not just called PTRACE_SYSCALL. > After your change, calling PTRACE_SINGLESTEP can now produce that result. > I don't think that change is a good thing. > > As the originator of the SYSGOOD option, Dan might have a comment about this. I am not the originator of PTRACE_O_TRACESYSGOOD, I just had the bad luck to touch it. I think reporting the system call using 0x80|SIGTRAP when you PTRACE_SINGLESTEP over the trap instruction makes excellent good sense. -- Daniel Jacobowitz