genode/base-foc/src/core/pd_session_extension.cc
Stefan Kalkowski 41eaff2cc6 Fiasco.OC: Re-use existing capability selectors
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.
2012-02-28 08:42:13 +01:00

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/*
* \brief Core implementation of the PD session extension
* \author Stefan Kalkowski
* \date 2011-04-14
*/
/*
* Copyright (C) 2011-2012 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU General Public License version 2.
*/
/* Genode includes */
#include <base/native_types.h>
/* Core includes */
#include <pd_session_component.h>
Genode::Native_capability Genode::Pd_session_component::task_cap() {
return Native_capability(_pd.native_task(), _pd.badge()); }