From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932577AbcFCJ5y (ORCPT ); Fri, 3 Jun 2016 05:57:54 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:36067 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932267AbcFCJ5w (ORCPT ); Fri, 3 Jun 2016 05:57:52 -0400 Date: Fri, 3 Jun 2016 12:57:48 +0300 From: Cyrill Gorcunov To: Dmitry Safonov Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, luto@amacapital.net, tglx@linutronix.de, hpa@zytor.com, x86@kernel.org, 0x7f454c46@gmail.com, oleg@redhat.com, xemul@virtuozzo.com, khorenko@virtuozzo.com, Andy Lutomirski Subject: Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Message-ID: <20160603095748.GC2431@uranus> References: <1464786697-20639-1-git-send-email-dsafonov@virtuozzo.com> <1464786697-20639-6-git-send-email-dsafonov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1464786697-20639-6-git-send-email-dsafonov@virtuozzo.com> User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 01, 2016 at 04:11:36PM +0300, Dmitry Safonov wrote: > As the task isn't executing at the moment of {GET,SET}REGS, > return regset that corresponds to code selector, rather than > value of TIF_IA32 flag. > I.e. if we ptrace i386 elf binary that has just changed it's > code selector to __USER_CS, than GET_REGS will return > full x86_64 register set. > > Note, that this will work only if application has changed it's CS. > If the application does 32-bit syscall with __USER_CS, ptrace > will still return 64-bit register set. Which might be still confusing > for tools that expect TS_COMPACT to be exposed [1, 2]. > > So this this change should make PTRACE_GETREGSET more reliable and > this will be another step to drop TIF_{IA32,X32} flags. > > [1]: https://sourceforge.net/p/strace/mailman/message/30471411/ > [2]: https://lkml.org/lkml/2012/1/18/320 > > Cc: Andy Lutomirski > Cc: Ingo Molnar > Cc: Thomas Gleixner > Cc: "H. Peter Anvin" > Cc: Oleg Nesterov > Signed-off-by: Dmitry Safonov Looks reasonable! Still if cs has been changed to non-compat selector and we now return 64bit registers set, won't it cause problems for old tools? I suspect it should not but still.