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Re: [RFC] malloc: add random offset to mmapped memory
- From: Rich Felker <dalias at libc dot org>
- To: Maarten Bosmans <mkbosmans at gmail dot com>
- Cc: libc-alpha at sourceware dot org
- Date: Mon, 2 Mar 2015 12:40:26 -0500
- Subject: Re: [RFC] malloc: add random offset to mmapped memory
- Authentication-results: sourceware.org; auth=none
- References: <CA+CvcKSNz=kWgeQL_Y9RoAtk5Bn1xOocymwCg7QcJ7rC_dDn+A at mail dot gmail dot com>
On Sat, Jan 24, 2015 at 10:01:31PM +0100, Maarten Bosmans wrote:
> My proposal is to use the extra (unused) space that we get from mmap
> anyway (because it is page-aligned) to add an offset to the returned
> pointer. This would improve the performance of this example test case
> when the arrays are large enough to be mmapped directly.
> I would like to get some feedback whether glibc developers think this
> is a worthwhile goal to pursue, before I start working on a patch.
I think you should be cautious not to introduce random perturbations
like this into programs where ASLR has been intentionally disabled. It
makes debugging certain types of issues extremely difficult.