Doubts regarding IRQ capabilities in L4 fiasco and genode

Harsha Sharma harshasharmaiitr at
Wed Jun 27 12:45:14 CEST 2018

Dear Genode Community,

I have some doubts regarding handling IRQ capabilities in L4 fiasco
microkernel and Genode.
L4 kernel maps IRQs to IRQ kernel objects which are created using
l4_factory_create_irq using factory object.
In genode, we attach IRQ capabilites to entrypoint thread with
l4_irq_attach in core component.
Also, signal handler session returns signal context capabilities from
core component and l4_irq_attach is also called in
What is the difference between signal context capabilities and IRQ capabilities?
(Or IRQ capabilities are kernel space capabilities and signal context
capabilities are genode cap map capabilities)
Is it possible to attach entrypoint thread to IRQ object capability
outside of core component ?

Actually, I'm working on checkpoint/restore project in genode and L4
fiasco. And comparing the kernel cap space before checkpoint and
restoring state, we find out that IRQ kernel object capabilities are
not same.
Signal context capabilities are checkpointed and restored correctly,
but problem is (most probably), that while restoring, we don't attach
it to entrypoint thread.
One approach is to intercept, IRQ session and then attaching irq
capability to entrypoint thread capability in restoring process.
Please correct me if I am wrong somewhere and any suggestions on above
approach will be really appreciated.
Thanks a lot.

Harsha Sharma


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