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From:   Andy Lutomirski <luto@amacapital.net>
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Subject: Re: [PATCH v7 1/4] x86/insn-eval: Add support for 64-bit kernel mode
Date:   Thu, 2 Jan 2020 16:55:22 +0900
Message-Id: <498AAA9C-4779-4557-BBF5-A05C55563204@amacapital.net>
References: <20200102074705.n6cnvxrcojhlxqr5@box.shutemov.name>
Cc:     Jann Horn <jannh@google.com>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>, kasan-dev@googlegroups.com,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>
In-Reply-To: <20200102074705.n6cnvxrcojhlxqr5@box.shutemov.name>
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Jan 2, 2020, at 4:47 PM, Kirill A. Shutemov <kirill@shutemov.name> wrot=
e:
>=20
> =EF=BB=BFOn Thu, Dec 19, 2019 at 12:11:47AM +0100, Jann Horn wrote:
>> To support evaluating 64-bit kernel mode instructions:
>>=20
>> Replace existing checks for user_64bit_mode() with a new helper that
>> checks whether code is being executed in either 64-bit kernel mode or
>> 64-bit user mode.
>>=20
>> Select the GS base depending on whether the instruction is being
>> evaluated in kernel mode.
>>=20
>> Signed-off-by: Jann Horn <jannh@google.com>
>=20
> In most cases you have struct insn around (or can easily pass it down to
> the place). Why not use insn->x86_64?
>=20
>=20

What populates that?

FWIW, this code is a bit buggy: it gets EFI mixed mode wrong. I=E2=80=99m no=
t entirely sure we care.=