Pagers by default do not share their capabilities with their children.
By using one of CAP_SHARE_SPACE, CAP_SHARE_GROUP or CAP_SHARE_CONTAINER
a pager may now share its capabilities with a collection of threads.
Test container is planned to test codezero microkernel extensively.
With these changes, everything is there to develop a full-featured test suite.
It also exemplifies how a new container type can be added to the system.
(cherry picked from commit f21fa53df421bfc8eeeaa096c89b98beed436c60)
Notion of pager hierarchy introduced using the existing but unused
pagerid field.
Thread creation now has two more flags TC_AS_PAGER and TC_SHARE_PAGER.
The former sets creator as pager, the latter sets creator's pager as pager.
Thread group capability sharing now correctly carries shared capabilities
to the thread group leader's tgr_cap_list list, and this list is checked
during capability checking.
Capabilities will be shared among collection of threads. A pager
will have a right to share its own capabilities with its space,
its thread group and its container.
Currently sharing is possible with only all of the caps. Next,
it will be support for cap splitting, granting, and partial sharing
and granting.
Access permission bits are required eventually but currently are
not a critical concern and yet they complicate configuration. For
sake of simplicity they are removed to be added later on when
absolutely needed.
Added support for pagers that fault to suspend and become zombies
along with all the threads that they manage. Zombie killing is to
be done at a later time, from this special zombie queue.
The implementation works same as a suspension, with the added action
that the thread is moved to a queue in kernel container.
Issues:
- A page-faulting thread suspends if receives -1 from pager page fault ipc.
This is fine if pager is about to delete the thread, but it is not if
it is a buggy pager.
- Need to find a way to completely get rid of suspended pager.
- A method of deleting suspended tasks could remedy both cases above.
Removed dependency on hard-coded pager id. Pager id is now passed
as an environment string `pagerid' to tasks. Alternatively, this
could take space in the utcb of each task.
Bahadir Balban