Subject: Re: Importing PaX features to NetBSD
To: Hubert Feyrer <email@example.com>
From: Elad Efrat <elad@NetBSD.org>
Date: 12/18/2005 12:12:50
Hubert Feyrer wrote:
> * under what license is the code to-be-imported (seeing GPL in the ouput
> of that test), and
There is no licensing problem.
> * what is the performance impact when this is enabled?
> I guess some more benchmarks would be useful to establish that.
I haven't done any native benchmarks, but I can point you to (some)
benchmarks already done, available at
http://www.pjvenda.org/linux/doc/pax-performance/, although I'm not
sure these are fair wrt/to the features in question.
Some information that might help figuring what would be the costs of
ASLR and MPROTECT:
ASLR calculates 3 random values on execution and saves these as offsets
to be used when a random value is needed. How expensive are 3
arc4random() calls in the context of an entire sys_execve()?
MPROTECT, when not talking about text relocations, is very simple and
a matter of playing with flags. There's some more work involved when
handling textrels, but we have both the PaX way and Matt's way to look
into and decide what would be best for us.
For these two features, the last case of handling textrels *may* present
the only visible performance hit.
However, like I already mentioned.. these are security features, and we
should let the user do the trade-off if desired. We can always have
these turned off by default.