genode/repos/base/include/base/ipc.h

/*
 * \brief  Generic IPC infrastructure
 * \author Norman Feske
 * \date   2006-06-12
 */

/*
 * Copyright (C) 2006-2017 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU Affero General Public License version 3.
 */

#ifndef _INCLUDE__BASE__IPC_H_
#define _INCLUDE__BASE__IPC_H_

#include <base/ipc_msgbuf.h>
#include <base/rpc_args.h>
#include <base/log.h>
#include <util/meta.h>

namespace Genode {

	struct Ipc_error : Exception { };

	class Ipc_unmarshaller;

	/**
	 * Invoke capability to call an RPC function
	 *
	 * \param rcv_caps  number of capabilities expected as result
	 * \throw Blocking_canceled
	 *
	 * \noapi
	 *
	 * The 'rcv_caps' value is used on kernels like NOVA to allocate the
	 * receive window for incoming capability selectors.
	 */
	Rpc_exception_code ipc_call(Native_capability dst,
	                            Msgbuf_base &snd_msg, Msgbuf_base &rcv_msg,
	                            size_t rcv_caps);
}


/**
 * Unmarshal arguments from receive buffer
 */
class Genode::Ipc_unmarshaller : Noncopyable
{
	protected:

		Msgbuf_base &_rcv_msg;
		unsigned     _read_offset = 0;
		unsigned     _read_cap_index = 0;

	private:

		char         *_rcv_buf      = (char *)_rcv_msg.data();
		size_t const  _rcv_buf_size = _rcv_msg.capacity();

		/*
		 * Noncopyable
		 */
		Ipc_unmarshaller(Ipc_unmarshaller const &);
		Ipc_unmarshaller &operator = (Ipc_unmarshaller const &);

	public:

		/**
		 * Obtain typed capability from message buffer
		 */
		template <typename IT>
		void extract(Capability<IT> &typed_cap)
		{
			typed_cap = extract(Meta::Overload_selector<Capability<IT> >());
		}

		template<typename IT>
		Capability<IT> extract(Meta::Overload_selector<Capability<IT> >)
		{
			Native_capability untyped_cap =
				extract(Meta::Overload_selector<Native_capability>());
			return reinterpret_cap_cast<IT>(untyped_cap);
		}

		/**
		 * Obtain capability from message buffer
		 */
		void extract(Native_capability &cap)
		{
			cap = extract(Meta::Overload_selector<Native_capability>());
		}

		Native_capability extract(Meta::Overload_selector<Native_capability>)
		{
			Native_capability cap = _read_cap_index < _rcv_msg.used_caps()
			                      ? _rcv_msg.cap(_read_cap_index) : Native_capability();
			_read_cap_index++;
			return cap;
		}

		/**
		 * Read 'Rpc_in_buffer' from receive buffer
		 */
		template <size_t SIZE>
		void extract(Rpc_in_buffer<SIZE> &b)
		{
			b = Rpc_in_buffer<SIZE>(0, 0);

			/*
			 * Check receive buffer range
			 *
			 * Note: The addr of the Rpc_in_buffer_base is a null pointer when this
			 *       condition triggers.
			 */
			try {
				b = extract(Meta::Overload_selector<Rpc_in_buffer<SIZE> >());
			} catch (Ipc_error) { }
		}

		template<size_t SIZE>
		Rpc_in_buffer<SIZE> extract(Meta::Overload_selector<Rpc_in_buffer<SIZE> >)
		{
			size_t size = extract(Meta::Overload_selector<size_t>());
			if (_read_offset + size > _rcv_buf_size) {
				error("message buffer overrun");
				throw Ipc_error();
			}

			Rpc_in_buffer<SIZE> buf(&_rcv_buf[_read_offset], size);
			_read_offset += align_natural(size);
			return buf;
		}

		/**
		 * Read value of type T from buffer
		 */
		template <typename T>
		void extract(T &value)
		{
			value = extract(Meta::Overload_selector<T>());
		}

		template <typename T>
		T extract(Meta::Overload_selector<T>)
		{
			/* check receive buffer range */
			if (_read_offset + sizeof(T) > _rcv_buf_size) throw Ipc_error();

			/* return value from receive buffer */
			T value = *reinterpret_cast<T *>(&_rcv_buf[_read_offset]);

			/* increment read pointer to next dword-aligned value */
			_read_offset += align_natural(sizeof(T));

			return value;
		}

		Ipc_unmarshaller(Msgbuf_base &rcv_msg) : _rcv_msg(rcv_msg) { }
};

#endif /* _INCLUDE__BASE__IPC_H_ */