Re: Just a few questions

[ness]

[I answer the questions on my best knowledge, but that doesn't imply the
answers have to be right]
Justin Emmanuel wrote:
> I just have a few questions, sorry if these have been addressed already
> somewhere and I missed them, but I am curious. I have been listening to
> Dr Shapiro's talks on Eros and it made me ask some questions.
>
> 1) How can the a process/kernel know that a capability really is
> who/what it says it is?

The kernel knows everything, so it has never a problem.
The second question is more tricky. In the Hurd, a process cannot know
that. It has to trust the soure of the capability. In EROS there is the
possibility to identify a capability. I'm not sure how it works, but it
has sth. to do with comparing caps, or so. We already had a discussion
about this here.

> 2) How many capabilities can a capability have? E.G. A mouse pointer
> capability loaded from a somewhere or other that also ( malevolently)
> has the capability programed in to write to the hard drive?? Whats to
> stop that happening? Is the user requested to give permission every time
> a particular I/O operation takes place? What if you have connected a
> file system ( maybe a floppy, CD ROM) and wish to copy some directories,
> will it ask for permission on every object?

A capability points to one object and has some rights associated with it.

> 3) Will L4 on Hurd be using a constructor capability?

First, we're not sure anymore whether we'll be allowed to say Hurd/L4.
Maybye Hurd/Coyotos, maybye... Second, we had a lot of design changes
last time. Only a few people have an imagination of how the Hurd on X
will look like in the future. But I guess we will not adopt the
constructor mechanism.

> 4) Does L4 have the answers to some of the questions raised by a project
> like Eros?

The Hurd and EROS have different goals. The successor of EROS is coyotos.
> Thanks for you patience. 
>  
--
-ness-