Constrained file descriptors

[Johannes Kliemann]

Hi Norman,

before Christmas we chatted about enabling the MMIO session on Linux.
You said that you know a possibility to create constrained file
descriptors (in such a way that accesses through this descriptor can
only access a part of the file). I've done a second search but I
couldn't find any useful information regarding this topic.
Do you have any further, more specific, information about how to achieve
this goal?

Regards,
Johannes