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

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Message-ID: <a9043b85-e44c-4070-1ecc-75f653539423@list.ru>
Date:   Fri, 10 Mar 2017 01:10:03 +0300
From:   Stas Sergeev <stsp@...t.ru>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Liang Z Li <liang.z.li@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Chen Yucong <slaoub@...il.com>,
        Alexandre Julliard <julliard@...ehq.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        X86 ML <x86@...nel.org>, linux-msdos@...r.kernel.org,
        wine-devel@...ehq.org
Subject: Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention

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