278 lines
7.5 KiB
C++
278 lines
7.5 KiB
C++
/*
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* \brief Mapping of Genode's capability names to kernel capabilities.
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* \author Stefan Kalkowski
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* \date 2012-02-16
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*
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* Although kernels like Fiasco.OC and NOVA provide capability mechanisms
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* to us, which should prevent the usage of global names, there is no
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* efficient way to retrieve a capability a process owns, when it gets the
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* same capability delivered again via IPC from another thread. But in some
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* use-cases in Genode this is essential (e.g. parent getting a close-session
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* request from a child). Moreover, we waste a lot of slots in the
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* capability-space of the process for one and the same kernel-object.
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* That's why we introduce a map of Genode's global capability names to the
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* process-local addresses in the capability-space.
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*
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* TODO: should be moved to the generic part of the framework, and used by
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* NOVA too.
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*/
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/*
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* Copyright (C) 2012-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__BASE__CAP_MAP_H_
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#define _INCLUDE__BASE__CAP_MAP_H_
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/* Genode includes */
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#include <base/exception.h>
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#include <base/stdint.h>
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#include <base/lock_guard.h>
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#include <util/avl_tree.h>
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#include <util/noncopyable.h>
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#include <util/string.h>
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namespace Genode
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{
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/**
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* A Cap_index represents a single mapping of the global capability id
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* to the address in the local capability space.
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*
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* The address of the Cap_index determines the location in the
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* (platform-specific) capability space of the process. Therefore it
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* shouldn't be copied around, but only referenced by
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* e.g. Native_capability.
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*/
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class Cap_index : public Avl_node<Cap_index>,
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Noncopyable
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{
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private:
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enum { INVALID_ID = -1, UNUSED = 0 };
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uint8_t _ref_cnt; /* reference counter */
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uint16_t _id; /* global capability id */
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public:
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Cap_index() : _ref_cnt(0), _id(INVALID_ID) { }
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bool valid() const { return _id != INVALID_ID; }
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bool used() const { return _id != UNUSED; }
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uint16_t id() const { return _id; }
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void id(uint16_t id) { _id = id; }
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uint8_t inc();
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uint8_t dec();
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addr_t kcap();
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void* operator new (size_t size, Cap_index* idx) { return idx; }
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void operator delete (void* idx) { memset(idx, 0, sizeof(Cap_index)); }
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/************************
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** Avl node interface **
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************************/
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bool higher(Cap_index *n);
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Cap_index *find_by_id(uint16_t id);
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};
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/**
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* Allocator for Cap_index objects.
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*
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* This is just an interface, as the real allocator has to be
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* implemented platform-specific.
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*/
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class Cap_index_allocator: Noncopyable
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{
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public:
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class Index_out_of_bounds : public Exception { };
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class Region_conflict : public Exception { };
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virtual ~Cap_index_allocator() {}
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/**
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* Allocate a range of Cap_index objects
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*
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* \param cnt number of objects to allocate
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* \return pointer to first allocated object, or zero if
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* out of entries
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*/
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virtual Cap_index* alloc_range(size_t cnt) = 0;
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/**
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* Allocate a Cap_index object at a specific
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* point in the capability space
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*
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* \param kcap address in capability space
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* \throw Index_out_of_bounds if address is out of scope
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* \return pointer to allocated object
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*/
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virtual Cap_index* alloc(addr_t kcap) = 0;
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/**
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* Free a range of Cap_index objects
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*
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* \param idx pointer to first object in range
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* \param cnt number of objects to free
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* \throw Index_out_of_bounds if address is out of scope
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*/
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virtual void free(Cap_index *idx, size_t cnt) = 0;
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/**
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* Get the Cap_index object's address in capability space
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*
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* \param idx pointer to the Cap_index object in question
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*/
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virtual addr_t idx_to_kcap(Cap_index *idx) = 0;
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/**
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* Get the Cap_index object of a specific location
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* in the capability space
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*
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* \param kcap the address in the capability space
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*/
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virtual Cap_index* kcap_to_idx(addr_t kcap) = 0;
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/**
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* Returns whether a Cap_index object is from the region
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* controlled by core, or not.
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*
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* \param idx pointer to the Cap_index object in question
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*/
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virtual bool static_idx(Cap_index *idx) = 0;
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};
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/**
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* Get the global Cap_index_allocator of the process.
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*/
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Cap_index_allocator *cap_idx_alloc();
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/**
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* Low-level spin-lock to protect Cap_index_allocator and the Cap_map
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*
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* We cannot use a normal Genode lock because this lock is used by code
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* executed prior the initialization of Genode
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*/
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class Spin_lock
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{
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private:
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volatile int _spinlock;
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public:
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/**
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* Constructor
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*/
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Spin_lock();
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void lock();
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void unlock();
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/**
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* Lock guard
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*/
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typedef Genode::Lock_guard<Spin_lock> Guard;
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};
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class Native_capability;
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/**
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* The Capability_map is an AVL-tree of Cap_index objects that can be
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* found via the global capability id
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*
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* It is used to re-find capabilities whenever a capability gets
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* transfered to a process, so that we can re-use an existing one
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* to save entries in the capability space, and prevent leaks of
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* them.
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*/
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class Capability_map : Noncopyable
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{
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private:
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Avl_tree<Cap_index> _tree;
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Spin_lock _lock;
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public:
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/**
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* Find an existing Cap_index via a capability id
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*
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* \param id the global capability id
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* \return pointer of Cap_index when found, otherwise zero
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*/
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Cap_index* find(int id);
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/**
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* Create and insert a new Cap_index with a specific capability id
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*
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* Allocation of the Cap_index is done via the global
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* Cap_index_allocator, which might throw exceptions that aren't
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* caught by this method
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*
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* \param id the global capability id
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* \return pointer to the new Cap_index object, or zero
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* when allocation failed
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*/
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Cap_index* insert(int id);
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/**
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* Create and insert a new Cap_index with a specific capability id,
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* and location in capability space
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*
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* A previously existent entry with the same id gets removed!
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*
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* \param id the global capability id
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* \param kcap address in capability space
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* \return pointer to the new Cap_index object, or zero
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* when allocation failed
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*/
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Cap_index* insert(int id, addr_t kcap);
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/**
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* Create and insert a new Cap_index with a specific capability id
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* and map from given kcap to newly allocated one,
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* if the an entry with the same id exists already,
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* it is returned if it points to the same kernel-object,
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* or gets overridden if it's already invalid.
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*
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* Allocation of the Cap_index is done via the global
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* Cap_index_allocator, which might throw exceptions that aren't
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* caught by this method
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*
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* \param id the global capability id
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* \return pointer to the new Cap_index object, or zero
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* when allocation failed, or when a valid entry
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* with the same id exists and it's kernel-object
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* differs to the one given by kcap
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*/
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Cap_index* insert_map(int id, addr_t kcap);
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/**
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* Remove (resp. invalidate) a Cap_index object
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*
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* \param i pointer to Cap_index object to remove
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*/
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void remove(Cap_index* i);
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};
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/**
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* Get the global Capability_map of the process.
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*/
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Capability_map *cap_map();
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}
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#endif /* _INCLUDE__BASE__CAP_MAP_H_ */
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