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Date:   Mon, 09 Sep 2019 12:56:18 +0100
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Subject: Re: [PATCH] x86/umip: Add emulation for 64-bit processes
To:     Borislav Petkov <bp@alien8.de>,
        Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
CC:     Brendan Shanks <bshanks@codeweavers.com>,
        linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, x86@kernel.org,
        "Eric W. Biederman" <ebiederm@xmission.com>
From:   hpa@zytor.com
Message-ID: <1E11E98F-4A38-4CDE-8549-64A2C28DC63E@zytor.com>
Sender: linux-kernel-owner@vger.kernel.org
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On September 8, 2019 8:22:48 AM GMT+01:00, Borislav Petkov <bp@alien8=2Ede>=
 wrote:
>On Sat, Sep 07, 2019 at 02:26:10PM -0700, Ricardo Neri wrote:
>> > Wine users have encountered a number of 64-bit Windows games that
>use
>> > these instructions (particularly sgdt), and were crashing when run
>on
>> > UMIP-enabled systems=2E
>>=20
>> Emulation support for 64-bit processes was not initially included
>> because no use cases had been identified=2E
>
>AFAIR, we said at the time that 64-bit doesn't need it because this is
>legacy software only and 64-bit will get fixed properly not to use
>those
>insns=2E I can probably guess how that went =2E=2E=2E

I don't think Windows games was something we considered=2E However, needin=
g to simulate these instructions is not a huge surprise=2E The important th=
ing is that by simulating them, we can plug the leak of some very high valu=
e kernel information =E2=80=93 mainly the GDT, IDT and TSS addresses=2E
--=20
Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E