From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756173Ab0BOTLP (ORCPT ); Mon, 15 Feb 2010 14:11:15 -0500 Received: from terminus.zytor.com ([198.137.202.10]:49983 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755797Ab0BOTLO (ORCPT ); Mon, 15 Feb 2010 14:11:14 -0500 Message-ID: <4B799C3F.7010308@zytor.com> Date: Mon, 15 Feb 2010 11:10:55 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.7) Gecko/20100120 Fedora/3.0.1-1.fc12 Thunderbird/3.0.1 MIME-Version: 1.0 To: Oleg Nesterov CC: Linus Torvalds , Roland McGrath , linux-kernel@vger.kernel.org Subject: Re: x86: get rid of the insane TIF_ABI_PENDING bit References: <20100215161752.GA19962@redhat.com> In-Reply-To: <20100215161752.GA19962@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/15/2010 08:17 AM, Oleg Nesterov wrote: >> + >> + /* Prepare the first "return" to user space */ >> + current_thread_info()->status |= TS_COMPAT; > > Can't understand why we need TS_COMPAT. I assume this is correct, > this was copied from flush_thread(). > > What TS_COMPAT actually means? I thought it just means "the task > is inside 32-bit syscall". > > If a 64bit task execs a 32bit app, can't this TS_COMPAT break, say, > syscall_get_arguments() ? > > Just curious, I don't really understand COMPAT issues anyway. > I suspect the purpose of TS_COMPAT is actually so you can ptrace() the newly exec'd process (and see it as a 32-bit process!) before it returns to userspace. The comment, obviously, is wrong -- that again refers to TIF_IA32. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.