OKL4 structure questions

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XavierL

OKL4 structure questions

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Hi,

I have (again) some questions about OKL4 structure:

I asked in a previous mail the difference between cells and address spaces.
Josh answered that in the case off a Linux cell there is one address space
for each program and I don't understand if those address spaces are OKL4
address spaces or Linux address spaces.
In this mail Josh also said that an address space is associated with exactly
one clist but in the pdf "OKL4 Programming Overview of the OKL4 3.0 API" at
page 54 the diagram shows 3 address spaces in 2 cells and 4 clists. What is
the rule about that point?
How to decide between address space and cell isolation for a given
application?

I would like to know the status of the kernel proof of correctness.

Thanks.

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Gernot Heiser

Re: OKL4 structure questions

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>>>>> On Fri, 29 May 2009 16:03:04 +0200, [hidden email] said:
XL> Hi,
XL> I have (again) some questions about OKL4 structure:

XL> I asked in a previous mail the difference between cells and address spaces.
XL> Josh answered that in the case off a Linux cell there is one address space
XL> for each program and I don't understand if those address spaces are OKL4
XL> address spaces or Linux address spaces.

Both. Linux address spaces get mapped onto OKL4 address spaces. OKL4
(kernel) address spaces are essentially an abstraction for page tables.

XL> In this mail Josh also said that an address space is associated with exactly
XL> one clist but in the pdf "OKL4 Programming Overview of the OKL4 3.0 API" at
XL> page 54 the diagram shows 3 address spaces in 2 cells and 4 clists. What is
XL> the rule about that point?

That diagram is misleading, apologies.

XL> How to decide between address space and cell isolation for a given
XL> application?

a Secure HyperCell is a high-level abstraction, which is implemented
by using low-level kernel abstractions, including Clists and address
spaces. The system designer should think in terms of the higher-level
constructs. Cells define isolation domains. If multiple processes
exist in such a domain (as is the case in the example of a virtual
machine) then they each get mapped onto a kernel address space, all
typically sharing the same Clist (although sub-domains with further
restricted rights can be set up -- there is much more support for this
in future releases).

XL> I would like to know the status of the kernel proof of correctness.

About a month away from completion.

Gernot

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