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

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Message-ID: <20171207195727.GA26792@bombadil.infradead.org>
Date:   Thu, 7 Dec 2017 11:57:27 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Cyril Hrubis <chrubis@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        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>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH 0/2] mm: introduce MAP_FIXED_SAFE

On Thu, Dec 07, 2017 at 11:14:27AM -0800, Kees Cook wrote:
> On Wed, Dec 6, 2017 at 9:46 PM, Michael Ellerman <mpe@...erman.id.au> wrote:
> > Matthew Wilcox <willy@...radead.org> writes:
> >> So, just like we currently say "exactly one of MAP_SHARED or MAP_PRIVATE",
> >> we could add a new paragraph saying "at most one of MAP_FIXED or
> >> MAP_REQUIRED" and "any of the following values".
> >
> > MAP_REQUIRED doesn't immediately grab me, but I don't actively dislike
> > it either :)
> >
> > What about MAP_AT_ADDR ?
> >
> > It's short, and says what it does on the tin. The first argument to mmap
> > is actually called "addr" too.
> 
> "FIXED" is supposed to do this too.
> 
> Pavel suggested:
> 
> MAP_ADD_FIXED
> 
> (which is different from "use fixed", and describes why it would fail:
> can't add since it already exists.)
> 
> Perhaps "MAP_FIXED_NEW"?
> 
> There has been a request to drop "FIXED" from the name, so these:
> 
> MAP_FIXED_NOCLOBBER
> MAP_FIXED_NOREPLACE
> MAP_FIXED_ADD
> MAP_FIXED_NEW
> 
> Could be:
> 
> MAP_NOCLOBBER
> MAP_NOREPLACE
> MAP_ADD
> MAP_NEW
> 
> and we still have the unloved, but acceptable:
> 
> MAP_REQUIRED
> 
> My vote is still for "NOREPLACE" or "NOCLOBBER" since it's very
> specific, though "NEW" is pretty clear too.

How about MAP_NOFORCE?