Date: Fri, 8 May 2015 16:09:09 +1000
From: Kevin Easton <kevin@guarana.org>
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Dave Hansen <dave@sr71.net>, Ingo Molnar <mingo@kernel.org>,
        linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH 00/12] [RFC] x86: Memory Protection Keys
Message-ID: <20150508060909.GA5296@chicago.guarana.org>
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On Thu, May 07, 2015 at 08:18:43PM +0100, One Thousand Gnomes wrote:
> > We could keep heap metadata as R/O and only make it R/W inside of
> > malloc() itself to catch corruption more quickly.
> 
> If you implement multiple malloc pools you can chop up lots of stuff.
> 
> In library land it isn't just stuff like malloc, you can use it as
> a debug weapon to protect library private data from naughty application
> code.

How could a library (or debugger, for that matter) arbitrate ownership
of the protection domains with the application?

One interesting use for it might be to be to provide an interface to
allocate memory and associate it with a lock that's supposed to be held
while accessing that memory.  The allocation function hashes the lock
address down to one of the 15 non-zero protection domains and applies 
that key to the memory, the lock function then adds RW access to the
appropriate protection domain and the unlock function removes it.

    - Kevin
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