linux-kernel - Re: [PATCH v7 1/4] x86/insn-eval: Add support for 64-bit kernel mode

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Date:   Thu, 2 Jan 2020 12:49:46 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Jann Horn <jannh@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v7 1/4] x86/insn-eval: Add support for 64-bit kernel mode

On Thu, Jan 02, 2020 at 10:27:33AM +0100, Borislav Petkov wrote:
> On Thu, Jan 02, 2020 at 04:55:22PM +0900, Andy Lutomirski wrote:
> > > In most cases you have struct insn around (or can easily pass it down to
> > > the place). Why not use insn->x86_64?
> > 
> > What populates that?
> 
> insn_init() AFAICT.
> 
> However, you have cases where you don't have struct insn:
> fixup_umip_exception() uses it and it calls insn_get_seg_base() which
> does use it too.

Caller can indicate the bitness directly. It's always 32-bit for UMIP and
get_seg_base_limit() can use insn->x86_64.

-- 
 Kirill A. Shutemov