[Jeremy ]
Sigma0 has disappeared from the latest Pistachio kernels as well, so even the information above is version dependent.
What?!? Sigma0 has always come with the kernels and will always do. How else are the applications supposed to get access to memory?
Learning about L4 in general can be frustrating as, being in significant part, a research vehicle, much of the background documentation is in conference papers and thesis extracts, and dates quickly (L4::Pistachio is evolving very rapidly). The background material is still useful, but you need to be aware that it's not always relevant to the latest releases.
Actually, the Version X.2 API and the corresponding L4Ka::Pistachio implementation is evolving rather slowly. Or put in a better way, the API is getting close to feature complete and there are as such not many more changes to the kernel (for the current API).
The source code is your friend here (although the user manual and refman are reasonably up to date). Most of the code is well written and structured (if sparsely commented), although it requires very good C++ and CPU platform knowledge to follow in detail.
The source code is *not* supposed to be your friend. This is not Linux. The refman is the definite source for kernel behaviour; and yes, the refman is updated whenever the API changes (with a changelog history entry in the preamble). If there's something unclear in the refman then please ask.
Any hack in the kernel implementation are either temporary solutions or used for testing purposes. Don't rely on them.
eSk