linux-kernel - Re: [PATCH 0/2] mm: introduce MAP_FIXED

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Message-ID: <87zi6we9z2.fsf@concordia.ellerman.id.au>
Date:   Wed, 06 Dec 2017 15:50:09 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Michal Hocko <mhocko@...nel.org>, Kees Cook <keescook@...omium.org>
Cc:     Linux API <linux-api@...r.kernel.org>,
        Khalid Aziz <khalid.aziz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Florian Weimer <fweimer@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Abdul Haleem <abdhalee@...ux.vnet.ibm.com>,
        Joel Stanley <joel@....id.au>
Subject: Re: [PATCH 0/2] mm: introduce MAP_FIXED_SAFE

Michal Hocko <mhocko@...nel.org> writes:

> On Wed 29-11-17 14:25:36, Kees Cook wrote:
>> On Wed, Nov 29, 2017 at 6:42 AM, Michal Hocko <mhocko@...nel.org> wrote:
>> > The first patch introduced MAP_FIXED_SAFE which enforces the given
>> > address but unlike MAP_FIXED it fails with ENOMEM if the given range
>> > conflicts with an existing one. The flag is introduced as a completely
>> 
>> I still think this name should be better. "SAFE" doesn't say what it's
>> safe from...

Yes exactly.

> It is safe in a sense it doesn't perform any address space dangerous
> operations. mmap is _inherently_ about the address space so the context
> should be kind of clear.

So now you have to define what "dangerous" means.

>> MAP_FIXED_UNIQUE
>> MAP_FIXED_ONCE
>> MAP_FIXED_FRESH
>
> Well, I can open a poll for the best name, but none of those you are
> proposing sound much better to me. Yeah, naming sucks...

I think Kees and I both previously suggested MAP_NO_CLOBBER for the
modifier.

So the obvious option for this would be MAP_FIXED_NO_CLOBBER.

Which is a bit longer sure, but says more or less exactly what it does.

cheers