Re: [Hurd-alpha-devel] Re: L4 instead of gnumach?

[Niels Möller]

Erik Verbruggen <ejv@cs.kun.nl> writes:

> Indeed. The nice thing about L4 is that it's simple and lean, and
> therefore fast. The emulation layer will definitely reduce speed. For
> example with IPC: I think the way to emulate the Mach behaviour (and to
> circumvent the page alignment) is to copy contents into page aligned
> memory blocks. But I think speed improvements can be done later on,
> especially because it will need *careful* optimizations.

What about security? I don't know L4 much (although a read some paper
on it a long time ago, the last time Hurd on L4 was discussed). My
impression was that L4 was a lot different from Mach. As the HURD
relies quite heavily on things like send rights, how heavy is it to do
something comparable on L4? Can it be done without erasing the
performance advantage?

(I believe managing send rights is a sane way to deal with security in
a complex system. So I don't think it is good enough to just try to
change the HURD's model to fit L4; after all, one of the points of
the Hurd-L4 thing is to make the HURD less dependent on particular
micro-kernels. To do that, one need to identify the features that are
essential to the HURD, and find out the best way to get them on each
kernel one is interested in).

/Niels