Re: KIP and other user mappings

On Wed Dec 13, 2006 at 14:34:30 +0100, Espen Skoglund wrote:
>[bahadir balban]
>> Hi,
>> In L4, what offsets and pages does the userspace need to know about
>> by standard?
>
>> On ARM (NICTA::Pistachio hello 1.1) for instance, KernelInterface()
>> is entered via a trap at offset 0xFFFFFFb4, and there are other
>> traps nearby. Does the userspace need to know about these by
>> standard or are they there for convenience? My expectation would be
>> that it would only need to know a fixed offset for KernelInterface()
>> call.
>
>> Also, are there other pages than the KIP that the userland expects
>> to find? For instance, USER_UTCB_REF is defined at 0xFF000FF0
>> (l4/include/arm/vregs.h), almost at the end of the KIP page for ARM.
>> Is it part of the KIP? Does the userspace need to know it's offset
>> in advance, or is it to be discovered from the KIP?
>
>I must admit that I'm not up to speed on the latest developments of
>NICTA::Pistachio/ARM, but in general the user apps need only know
>what's defined in the ABI for the architecture in question.  E.g., it
>might be a special trap or jump to a particular location to get the
>KIP address, or it might be a memory access to a special location to
>get the UTCB address.  These things should all be properly described
>in the ABI spec.

This is the case for ARM. The architecture specified way of obtaining the
UTCB address is reading from a special address. (0xFF000FF0)

Cheers,

Benno