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From: Andy Lutomirski <luto@amacapital.net>
Date: Thu, 26 Jun 2014 15:19:26 -0700
Message-ID: <CALCETrVTTh9yuXH0hfcOpytyBd25K6thPfqqUBQtnOqx90ZRqw@mail.gmail.com>
Subject: Re: [PATCH v6 02/10] x86, mpx: add MPX specific mmap interface
To: Dave Hansen <dave.hansen@intel.com>
Cc: "Ren, Qiaowei" <qiaowei.ren@intel.com>, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        X86 ML <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org

On Wed, Jun 25, 2014 at 2:45 PM, Dave Hansen <dave.hansen@intel.com> wrote:
> On 06/25/2014 02:05 PM, Andy Lutomirski wrote:
>> Hmm.  the memfd_create thing may be able to do this for you.  If you
>> created a per-mm memfd and mapped it, it all just might work.
>
> memfd_create() seems to bring a fair amount of baggage along (the fd
> part :) if all we want is a marker.  Really, all we need is _a_ bit, and
> some way to plumb to userspace the RSS values of VMAs with that bit set.
>
> Creating and mmap()'ing a fd seems a rather roundabout way to get there.

Hmm.  So does VM_MPX, though.  If this stuff were done entirely in
userspace, then memfd_create would be exactly the right solution, I
think.

Would it work to just scan the bound directory to figure out how many
bound tables exist?

--Andy
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