From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ricardo Neri Subject: Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Date: Fri, 10 Mar 2017 15:58:27 -0800 Message-ID: <1489190307.131264.45.camel@ranerica-desktop> References: <20170308003254.27833-1-ricardo.neri-calderon@linux.intel.com> <79ba0fff-4c01-2bfa-06cb-5cfc98dd710c@list.ru> <997ba581-ecfa-b773-a48e-85b92a439836@list.ru> <1489022122.131264.33.camel@ranerica-desktop> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Sender: linux-msdos-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="utf-8" To: Andy Lutomirski Cc: Stas Sergeev , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Borislav Petkov , Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Liang Z Li , Masami Hiramatsu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S. Tsirkin" , Paul Gortmaker , Vlastimil Babka , Chen Yucong On Thu, 2017-03-09 at 18:39 -0800, Andy Lutomirski wrote: > On Thu, Mar 9, 2017 at 2:10 PM, Stas Sergeev wrote: > > 09.03.2017 04:15, Ricardo Neri пишет: > > > >> On Wed, 2017-03-08 at 08:46 -0800, Andy Lutomirski wrote: > >>> > >>> On Wed, Mar 8, 2017 at 8:29 AM, Stas Sergeev wrote: > >>>> > >>>> 08.03.2017 19:06, Andy Lutomirski пишет: > >>>>> > >>>>> On Wed, Mar 8, 2017 at 6:08 AM, Stas Sergeev wrote: > >>>>>> > >>>>>> 08.03.2017 03:32, Ricardo Neri пишет: > >>>>>>> > >>>>>>> These are the instructions covered by UMIP: > >>>>>>> * SGDT - Store Global Descriptor Table > >>>>>>> * SIDT - Store Interrupt Descriptor Table > >>>>>>> * SLDT - Store Local Descriptor Table > >>>>>>> * SMSW - Store Machine Status Word > >>>>>>> * STR - Store Task Register > >>>>>>> > >>>>>>> This patchset initially treated tasks running in virtual-8086 > >>> > >>> mode as a > >>>>>>> > >>>>>>> special case. However, I received clarification that DOSEMU[8] > >>> > >>> does not > >>>>>>> > >>>>>>> support applications that use these instructions. > >>>>> > >>>>> Can you remind me what was special about it? It looks like you > >>> > >>> still > >>>>> > >>>>> emulate them in v8086 mode. > >>>> > >>>> Indeed, sorry, I meant prot mode here. :) > >>>> So I wonder what was cited to be special about v86. > >> > >> Initially my patches disabled UMIP on virtual-8086 instructions, without > >> regards of protected mode (i.e., UMIP was always enabled). I didn't have > >> emulation at the time. Then, I added emulation code that now covers > >> protected and virtual-8086 modes. I guess it is not special anymore. > > > > But isn't SLDT&friends just throw UD in v86? > > How does UMIP affect this? How does your patch affect > > this? > > Er, right. Ricardo, your code may need fixing. But don't you have a > test case for this? The behavior should be the same with and without > your patches applied. The exception is #UD, not #GP, so maybe your > code just never executes in the vm86 case. Ouch! Yes, I am afraid my code will attempt to emulate sldt in vm86 mode. The test cases that I have for vm86 are only for the instructions that are valid in vm86: smsw, sidt and sgdt. I will add test cases for str and sldt and make sure that a #UD is issued. Would this trigger a v7 series? Thanks and BR, Ricardo > > --Andy