genode/base-foc/include/base/ipc_msgbuf.h
Stefan Kalkowski d287b9d893 Fiasco.OC: introduce Cap_index (fixes #149, #112)
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.
2012-03-22 14:10:44 +01:00

155 lines
3.1 KiB
C++

/*
* \brief IPC message buffer layout for Fiasco.OC
* \author Stefan Kalkowski
* \date 2010-11-30
*
* On Fiasco.OC, IPC is used to transmit plain data and capabilities.
* Therefore the message buffer contains both categories of payload.
*/
/*
* Copyright (C) 2010-2012 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.
*/
#ifndef _INCLUDE__BASE__IPC_MSGBUF_H_
#define _INCLUDE__BASE__IPC_MSGBUF_H_
/* Genode includes */
#include <base/cap_map.h>
/* Fiasco.OC includes */
namespace Fiasco {
#include <l4/sys/types.h>
#include <l4/sys/utcb.h>
}
namespace Genode {
class Msgbuf_base
{
public:
enum { MAX_CAP_ARGS_LOG2 = 2, MAX_CAP_ARGS = 1 << MAX_CAP_ARGS_LOG2 };
protected:
size_t _size;
/**
* Number of capability selectors to send.
*/
size_t _snd_cap_sel_cnt;
/**
* Capability selectors to delegate.
*/
addr_t _snd_cap_sel[MAX_CAP_ARGS];
/**
* Base of capability receive window.
*/
Cap_index* _rcv_idx_base;
/**
* Read counter for unmarshalling portal capability selectors
*/
addr_t _rcv_cap_sel_cnt;
char _msg_start[]; /* symbol marks start of message */
public:
/**
* Constructor
*/
Msgbuf_base() : _rcv_idx_base(cap_idx_alloc()->alloc(MAX_CAP_ARGS))
{
rcv_reset();
snd_reset();
}
~Msgbuf_base() {
cap_idx_alloc()->free(_rcv_idx_base, MAX_CAP_ARGS); }
/*
* Begin of actual message buffer
*/
char buf[];
/**
* Return size of message buffer
*/
inline size_t size() const { return _size; };
/**
* Return address of message buffer
*/
inline void *addr() { return &_msg_start[0]; };
/**
* Reset portal capability selector payload
*/
inline void snd_reset() { _snd_cap_sel_cnt = 0; }
/**
* Append capability selector to message buffer
*/
inline bool snd_append_cap_sel(addr_t cap_sel)
{
if (_snd_cap_sel_cnt >= MAX_CAP_ARGS)
return false;
_snd_cap_sel[_snd_cap_sel_cnt++] = cap_sel;
return true;
}
/**
* Return number of marshalled capability selectors
*/
inline size_t snd_cap_sel_cnt() { return _snd_cap_sel_cnt; }
/**
* Return capability selector to send.
*
* \param i index (0 ... 'snd_cap_sel_cnt()' - 1)
* \return capability selector, or 0 if index is invalid
*/
addr_t snd_cap_sel(unsigned i) {
return i < _snd_cap_sel_cnt ? _snd_cap_sel[i] : 0; }
/**
* Return address of capability receive window.
*/
addr_t rcv_cap_sel_base() { return _rcv_idx_base->kcap(); }
/**
* Reset capability receive window
*/
void rcv_reset() { _rcv_cap_sel_cnt = 0; }
/**
* Return next received capability selector.
*
* \return capability selector, or 0 if index is invalid
*/
addr_t rcv_cap_sel() {
return rcv_cap_sel_base() + _rcv_cap_sel_cnt++ * Fiasco::L4_CAP_SIZE; }
};
template <unsigned BUF_SIZE>
class Msgbuf : public Msgbuf_base
{
public:
char buf[BUF_SIZE];
Msgbuf() { _size = BUF_SIZE; }
};
}
#endif /* _INCLUDE__BASE__IPC_MSGBUF_H_ */