The Cap_mapping abstraction in core shouldn't use a Cap_index directly, but
use Native_capability instead, as it can break reference-counting, as long as
the same Cap_index gets used in a Cap_mapping and a Native_capability. This
commit finally fixes#208.
This commit fixes several issues that were triggered e.g. by the
'noux_tool_chain' run-script (fix#208 in part). The following problems
are tackled:
* Don't reference count capability selectors within a task that are actually
controlled by core (all beneath 0x200000), because it's undecideable which
"version" of a capability selector we currently use, e.g. a thread gets
destroyed and a new one gets created immediately some other thread might
have a Native_capability pointing to the already destroyed thread's gate
capability-slot, that is now a new valid one (the one of the new thread)
* In core we cannot invalidate and remove a capability from the so called
Cap_map before each reference to it is destroyed, so don't do this in
Cap_session_component::free, but only reference-decrement within there,
the actual removal can only be done in Cap_map::remove. Because core also
has to invalidate a capability to be removed in all protection-domains
we have to implement a core specific Cap_map::remove method
* When a capability gets inserted into the Cap_map, and we detect an old
invalid entry with the dame id in the tree, don't just overmap that
invalid entry (as there exist remaining references to it), but just remove
it from the tree and allocate an new entry.
* Use the Cap_session_component interface to free a Pager_object when it
gets dissolved, as its also used for allocation
The following fixes partly solve the problems triggered by the noux stress
test introduced by nfeske in issue #208.
* The check whether a capability exists in the Cap_map, and its insertion,
has to be done atomically
* While removing a capability it is looked up in the Cap_map via its id,
check whether the found capability pointer is the same like the looked up,
otherwise the wrong capability gets freed
* When a local capability is un- resp. marshalled, only the local pointer
gets transfered, not the redundant capability id
* Introduce several assertions and warnings to facilitate debugging
Implements Native_capability as smart-pointer type referencing Cap_index
objects. Whenever capabilities are copied, assigned, constructed, or destructed
the reference-counter of the Cap_index is incremented/decremented. When it
reaches zero the Cap_index is removed from the process-global cap_map and
gets freed. Fix for issue #32.
Removing a Cap_index from Capability_map in core can happen twice, via
Cap_session_component or destructor of a Cap_mapping. That it's checked
whether the index is part of the map before removing it. This patch puts
the check into the remove method, so both operations are within the same
lock context, to remove a race condition.
This is a follow up fix for commit d287b9d893
This commit introduces a Cap_index class for Fiasco.OC's capabilities.
A Cap_index is a combination of the global capability id, that is used by Genode
to correctly identify a kernel-object, and a corresponding entry in a
protection-domain's (kernel-)capability-space. The cap-indices are non-copyable,
unique objects, that are held in a Cap_map. The Cap_map is used to re-find
capabilities already present in the protection-domain, when a capability is
received via IPC. The retrieval of capabilities effectively fixes issue #112,
meaning the waste of capability-space entries.
Because Cap_index objects are non-copyable (their address indicates the position
in the capability-space of the pd), they are inappropriate to use as
Native_capability. Therefore, Native_capability is implemented as a reference
to Cap_index objects. This design seems to be a good pre-condition to implement
smart-pointers for entries in the capability-space, and thereby closing existing
leaks (please refer to issue #32).
Cap_index, Cap_map, and the allocator for Cap_index objects are designed in a way,
that it should be relatively easy to apply the same concept to NOVA also. By now,
these classes are located in the `base-foc` repository, but they intentionally
contain no Fiasco.OC specific elements.
The previously explained changes had extensive impact on the whole Fiasco.OC
platform implementation, due to various dependencies. The following things had to
be changed:
* The Thread object's startup and destruction routine is re-arranged, to
enable another thread (that calls the Thread destructor) gaining the
capability id of the thread's gate to remove it from the Cap_map, the
thread's UTCB had to be made available to the caller, because there
is the current location of that id. After having the UTCB available
in the Thread object for that reason, the whole thread bootstrapping
could be simplified.
* In the course of changing the Native_capability's semantic, a new Cap_mapping
class was introduced in core, that facilitates the establishment and
destruction of capability mappings between core and it's client's, especially
mappings related to Platform_thread and Platform_task, that are relevant to
task and thread creation and destruction. Thereby, the destruction of
threads had to be reworked, which effectively removed a bug (issue #149)
where some threads weren't destroyed properly.
* In the quick fix for issue #112, something similar to the Cap_map was
introduced available in all processes. Moreover, some kind of a capability
map already existed in core, to handle cap-session request properly. The
introduction of the Cap_map unified both structures, so that the
cap-session component code in core had to be reworked too.
* The platform initialization code had to be changed sligthly due to the
changes in Native_capability
* The vcpu initialization in the L4Linux support library had to be adapted
according to the already mentioned changes in the Thread object's bootstrap
code.
This patch unifies the Native_capability classes for the different kernel
platforms by introducing an appropriate template, and eliminating naming
differences. Please refer issue #145.
In the cap-session component in core when freeing a capability, the
corresponding kernel object should be unmapped from all processes and core.
Until now, the unmap operation for removing the kernel object didn't worked
because of using the wrong rights-map. This patch fixes it.
The re-use of capabilities introduced by the last patch triggered this
problem because its essential for the capability-registry to detect
invalidated capabilities.
This is an interim fix for issue #112. This patch extends the
'Capability_allocator' class with the ability to register the global
ID of a Genode capability so that the ID gets associated with a
process-local kernel capability. Whenever a Genode capability gets
unmarshalled from an IPC message, the capability-allocator is asked,
with the global ID as key, whether the kernel-cap already exists.
This significantly reduces the waste of kernel-capability slots.
To circumvent problems of having one and the same ID for different kernel
objects, the following problems had to be solved:
* Replace pseudo IDs with unique ones from core's badge allocator
* When freeing a session object, free the global ID _after_ unmapping
the kernel object, otherwise the global ID might get re-used in some
process and the registry will find a valid but wrong capability
for the ID
Because core aggregates all capabilities of all different processes, its
capability registry needs much more memory compared to a regular process.
By parametrizing capability allocators differently for core and non-core
processes, the global memory overhead for capability registries is kept
at a reasonable level.
