Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755986AbcL0Web (ORCPT ); Tue, 27 Dec 2016 17:34:31 -0500 Received: from mga04.intel.com ([192.55.52.120]:21800 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755650AbcL0WeX (ORCPT ); Tue, 27 Dec 2016 17:34:23 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,418,1477983600"; d="scan'208";a="916617104" Message-ID: <1482878061.106950.11.camel@ranerica-desktop> Subject: Re: [v2 6/7] x86/traps: Fixup general protection faults caused by UMIP From: Ricardo Neri To: Andy Lutomirski Cc: Ingo Molnar , Thomas Gleixner , Borislav Petkov , Andy Lutomirski , Peter Zijlstra , "linux-kernel@vger.kernel.org" , X86 ML , linux-msdos@vger.kernel.org, wine-devel@winehq.org, Andrew Morton , "H . Peter Anvin" , Brian Gerst , Chen Yucong , Chris Metcalf , Dave Hansen , Fenghua Yu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S . Tsirkin" , Paul Gortmaker , "Ravi V . Shankar" , Shuah Khan , Vlastimil Babka , Tony Luck , Paolo Bonzini , "Liang Z . Li" , Alexandre Julliard , Stas Sergeev Date: Tue, 27 Dec 2016 14:34:21 -0800 In-Reply-To: References: <20161224013745.108716-1-ricardo.neri-calderon@linux.intel.com> <20161224013745.108716-7-ricardo.neri-calderon@linux.intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2868 Lines: 76 On Fri, 2016-12-23 at 18:11 -0800, Andy Lutomirski wrote: > On Fri, Dec 23, 2016 at 5:37 PM, Ricardo Neri > wrote: > > If the User-Mode Instruction Prevention CPU feature is available and > > enabled, a general protection fault will be issued if the instructions > > sgdt, sldt, sidt, str or smsw are executed from user-mode context > > (CPL > 0). If the fault was caused by any of the instructions protected > > by UMIP, fixup_umip_exceptino will emulate dummy results for these > > instructions. > > > > Cc: Andy Lutomirski > > Cc: Andrew Morton > > Cc: H. Peter Anvin > > Cc: Borislav Petkov > > Cc: Brian Gerst > > Cc: Chen Yucong > > Cc: Chris Metcalf > > Cc: Dave Hansen > > Cc: Fenghua Yu > > Cc: Huang Rui > > Cc: Jiri Slaby > > Cc: Jonathan Corbet > > Cc: Michael S. Tsirkin > > Cc: Paul Gortmaker > > Cc: Peter Zijlstra > > Cc: Ravi V. Shankar > > Cc: Shuah Khan > > Cc: Vlastimil Babka > > Cc: Tony Luck > > Cc: Paolo Bonzini > > Cc: Liang Z. Li > > Cc: Alexandre Julliard > > Cc: Stas Sergeev > > Cc: x86@kernel.org > > Cc: linux-msdos@vger.kernel.org > > Signed-off-by: Ricardo Neri > > --- > > arch/x86/kernel/traps.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > > index bf0c6d0..5044fb3 100644 > > --- a/arch/x86/kernel/traps.c > > +++ b/arch/x86/kernel/traps.c > > @@ -64,6 +64,7 @@ > > #include > > #include > > #include > > +#include > > > > #ifdef CONFIG_X86_64 > > #include > > @@ -491,6 +492,9 @@ do_general_protection(struct pt_regs *regs, long error_code) > > RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); > > cond_local_irq_enable(regs); > > > > + if (user_mode(regs) && !fixup_umip_exception(regs)) > > + return; > > + > > I would do fixup_umip_exception(regs) == 0 to make it more obvious > what's going on. Sure. I will make this change. > > Also, since you're allowing this in v8086 mode, I think this should > have an explicit test in > tools/testing/selftests/x86/entry_from_vm86.c. I *think* it will work > fine, but the pt_regs handling in vm86 mode is quite scary and has > been rewritten recently. I will include a test for this. Thanks and BR, Ricardo