Hacking core to pass base capabilities.

Stefan Kalkowski stefan.kalkowski at ...1...
Thu Jan 31 19:04:53 CET 2013

Hi Daniel,

On 01/30/2013 11:51 PM, Daniel Waddington wrote:
> Hi,
> I am trying to hack Genode's core so that either init, or a child of
> init, is given the L4_BASE_ICU_CAP.  This will allow (as a hack) direct
> handling of IRQs from the kernel.  My problem is, is that I cannot see
> how to get the native task cap (relevant to the parent process) for the
> child process (e.g., from the Core_child or Child class) in order to do
> the task map. 
> Can someone give me some hints?

Every task in Genode/Fiasco.OC gets its task capability mapped into its
capability space at position: "Fiasco::TASK_CAP" (please look at
The mapping is established when the first thread gets bound to the task,
look at "bind_thread" in 'base-foc/src/core/platform_pd.cc'. We need the
task capability anyway to move capabilities within a task.

With respect to your attempts to get an ICU capability into a task
beyond core: I would suggest to overload the IRQ session of
Genode/Fiasco.OC in a similar manner like it's done for instance with
the CPU session, look at: 'base-foc/include/foc_cpu_session/*'. The CPU
session extension allows for example to allocate additional IRQ
capabilities that can be associated with threads. This extension was
introduced to enable running L4Linux on top Genode. I suppose you can
extend the IRQ session the same way to return ICU capabilities to any

Best Regards

> Sorry to be hacking your beautiful design ;) and yes, I know this is bad
> from a security perspective.
> Daniel
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Stefan Kalkowski
Genode Labs

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

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