Examples container type is designed to keep applications using codezero
userspace libraries, which is aiming to help newcomers who would like to
develop programs on top of the l4 microkernel.
Now bare bone application is one of the examples. In the near future, lots of
new programs will be introduced to show the various aspects of codezero
eco-system.
Currently, the tid returned from kernel contains container id as
well, which makes it sufficient to do inter-container syscalls without
any preparation.
The helpers added are for presentation purposes only. Container id
is deleted so that the raw thread id is available for printing or
similar.
Thread ids now contain their container ids in the top 2 nibbles.
Threads on other containers can be addressed by changing those
two nibbles. The addressing of inter-container threads are
subject to capabilities.
Task ids are now unsigned as the container ids will need to be encoded
in the id fields as well.
For requests who require even more comprehensive id input, (such as
thread creation) also added is the container id so that threads
_could_ potentially be created in other containers as well.
VIRTMEM and PHYSMEM are theoretically separate resources to be
protected than a MAP resource, which is meant to protect the syscall
privileges.
In practice MAP is always used together with a VIRTMEM and a PHYSMEM
resource, therefore reach VIRTMEM/PHYSMEM resource is now merged with
the MAP capability, combining the micro-permission bits.
We still have to have the pager structs because they possess intermediate
data during boot up such as for transferring of capability lists to
boot stack one-by-one, and then to newly generated ktcbs.
Previously all pending events were handled on return of exceptions
in process context. This was causing threads that run in userspace
and take no exceptions not handle their pending events indefinitely.
Now scheduler handles them in irq context as well.
Multi-threaded apps can now wait on children to destroy.
WAIT_ON is useful when a child exists with an exit code and the pager
of the child does not want to take the hassle of destorying it via an
ipc. It provides an alternative method of synchronous thread destruction,
where the child destroys itself directly rather than the parent issuing
a destroy on it explicitly.
Pagers kill all children but suspend themselves.
Currently not straightforward for a pager to delete its own tcb and quit.
It should take all allocator locks without sleeping, remove itself from
scheduler queue and then delete itself and quit. This is not so easy now
as some allocation locks are mutexes. (Address space lock, ktcb/space
allocators etc.)
An easier approach would be to have a kernel thread or a superior thread
that would delete the pager
Reiterating again to simplify:
Working:
- Pager issues destroy, client also issues exit
they work in sync.
Missing
- Pager killing itself
- Pager killing all children while killing itself
- Pager waiting on children
