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• [ Previous ] In reply to: Eyal Lotem

> I'm generally very interested in EROS and capability systems, but I might
be misinformed about it, so please correct me if I get it all wrong.
> ...

I believe what Eyal means here has to do with the definition and implementation of the EROS VM and OS.

In reply, I have a couple of questions, as well as a few ideas Eyal and I developed in "private communication"...

As I understand it, the virtual machine provides the "primitive services and a few basic object types" and the operating system puts them to use, providing its own services for the user and the application:

1. - am I correct in thinking that the design intentionally allows for more than one of these operating systems to run under the VM?
2. - the kernel (system image?) combines the VM and the hardware drivers, while the operating system is a seperate domain?
3. - or are the drivers running in seperate domains?

At this point the idea of removing the h/w drivers from the kernel (assuming point 2 is correct and not 3) and running them as user-level processes comes into play...

So, either
2.a. - an OS provides two new services: an io bank and an irq bank. The VM isn't the right place to add these services since the VM is 'abstract neutral'?
Other OSs must then run under this main OS.

or, simpler,

2.b. - a new 'domain' (in the sense of the OS and VM being seperate) provides these services.

I believe having these services at the top of the hierarchy is necessary in order for point 1 to work correctly (that is, to allow for resources to be multiplexed safely (?) among the various systems).

• hardware drivers [only] receive capabilities to these services; this prevents other user-level applications from being capable of IO while still allowing the hardware drivers to run as user-level processes safely.
• if I've read this properly, then the Page object is responsible for mapping disk pages to memory, and therefore it must be capable of communicating with the disk driver? Under 2.b I can't seem to [completely] figure out how the Page object gains access to the disk services...

Finally, doing this seems to affect the concept of the VM being 'abstract neutral' (which I'm sure is an important one)... or perhaps am I going too far into what is considered as the OS's problems?

P.S. I've been reading quite a bit about EROS for a while now... though I have a serious disability in not completely understanding the use of notation in the proof of confinement (rather, the chapter leading up to it [in Shapiro's dissertation]). Is there any way I could find a [freely available] reference or something similar to help me along?

Well, hopefully I've been clear enough about this first lot of things bothering me... and hopefully there's a reply or two, none too head-bashing...

R.J. Shaw.

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• [ Previous ] In reply to: Eyal Lotem