Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention

Stas Sergeev
2017-03-09T22:10:03Z

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 <stsp@list.ru> wrote:
>>> 08.03.2017 19:06, Andy Lutomirski пишет:
>>>> On Wed, Mar 8, 2017 at 6:08 AM, Stas Sergeev <stsp@list.ru> 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?