Hi Adrian,

On 06.02.2016 00:40, Adrian Danis wrote:
> My suggestion at this point in time would be to implement an allocation
> strategy that supports plain old incremental retype. Remembering that
> any strategy that works for incremental retype can be trivially made to
> work with retype at offset.

I will go for it then. ;-)

> Currently there are no plans to bring retype at offset to the verified
> kernel. By my understanding (note that I'm not an actual verification
> person) the main two reasons for this are
> * The heap used is both a more complicated data structure, and has very
> complicated invariants due to the nature of the searches performed on it
> * Changing the implementation of the cap derivation tree will invalidate
> large parts of the proof, which will simply require large amounts of
> verification people power to fix
> 
> Whilst we will always have an experimental branch, it is never clear
> what experiments we will continue and which we will abandon for various
> reasons. This uncertainty is of course mostly applicable to items that
> do not have roadmap for verification and life on the master branch.
> Whilst the searchable cdt (and the associated retype at offset) is
> clearly useful, unfortunately it is not on the roadmap
> (https://sel4.systems/Info/Roadmap/) and so it's continued existence is
> forever uncertain.

These insights are very valuable. Thank you for sharing them.

Cheers
Norman

-- 
Dr.-Ing. Norman Feske
Genode Labs

http://www.genode-labs.com · http://genode.org

Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden
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