hw: communicate message type through UTCB

ref #874

base-hw/include/base/native_types.h

@@ -85,22 +85,43 @@ namespace Genode
 		bool valid() const { return thread_id != 0; }
 	};
 
+	/**
+	 * Types of synchronously communicated messages
+	 */
+	struct Msg_type
+	{
+		enum Id {
+			INVALID = 0,
+			IPC     = 1,
+		};
+	};
+
+	/**
+	 * Message that is communicated synchronously
+	 */
+	struct Msg
+	{
+		Msg_type::Id type;
+		uint8_t      data[];
+	};
+
+	/**
+	 * Message that is communicated between user threads
+	 */
+	struct Ipc_msg : Msg
+	{
+		size_t  size;
+		uint8_t data[];
+	};
+
 	/**
 	 * Describes a userland-thread-context region
 	 */
 	struct Native_utcb
 	{
-		/**
-		 * Structure of an IPC message held by the UTCB
-		 */
-		struct Ipc_msg
-		{
-			size_t  size;
-			uint8_t data[];
-		};
-
 		union {
 			uint8_t data[1 << MIN_MAPPING_SIZE_LOG2];
+			Msg     msg;
 			Ipc_msg ipc_msg;
 		};
 

base-hw/include/kernel/syscalls.h

@@ -333,51 +333,42 @@ namespace Kernel
 
 
 	/**
-	 * Send IPC request and wait for reply
+	 * Send IPC request and await corresponding IPC reply
 	 *
 	 * \param id  kernel name of the server thread
 	 *
-	 * \retval  0  successful
-	 * \retval -1  failed
-	 *
-	 * If the call returns successful the callers UTCB provides
-	 * a valid reply message and its metadata.
+	 * As soon as call returns, callers UTCB provides received message.
 	 */
-	inline int request_and_wait(unsigned const id)
+	inline void request_and_wait(unsigned const id)
 	{
-		return (int)syscall(REQUEST_AND_WAIT, id);
+		syscall(REQUEST_AND_WAIT, id);
 	}
 
 
 	/**
-	 * Wait for next IPC request, discard current request
+	 * Await the receipt of a message
 	 *
-	 * \retval  0  succeeded
-	 * \retval -1  failed
+	 * \return  type of received message
 	 *
-	 * If the call returns successful the callers UTCB provides
-	 * a valid request message and its metadata.
+	 * As soon as call returns, callers UTCB provides received message.
 	 */
-	inline int wait_for_request()
+	inline void wait_for_request()
 	{
-		return (int)syscall(WAIT_FOR_REQUEST);
+		syscall(WAIT_FOR_REQUEST);
 	}
 
 
 	/**
-	 * Reply to last IPC request
+	 * Reply to lastly received message
 	 *
-	 * \param await_request  if the call shall await and fetch next request
+	 * \param await_message  wether the call shall await receipt of a message
 	 *
-	 * \retval  0  succeeded
-	 * \retval -1  failed to receive request
-	 *
-	 * If await_request = 1 and the call returns successful the callers UTCB
-	 * provides a valid request message and its metadata.
+	 * If await_request = 1, callers UTCB provides received message
+	 * as soon as call returns
 	 */
-	inline int reply(bool const await_request)
+	inline void reply(bool const await_message)
 	{
-		return (int)syscall(REPLY, await_request);
+		syscall(REPLY, await_message);
 	}
 
 

base-hw/src/base/ipc.cc

@@ -92,7 +92,7 @@ Ipc_ostream::Ipc_ostream(Native_capability dst, Msgbuf_base *snd_msg)
 
 void Ipc_istream::_wait()
 {
-	/* FIXME this shall be not supported */
+	/* FIXME: this shall be not supported */
 	Kernel::pause_thread();
 }
 
@@ -116,11 +116,17 @@ void Ipc_client::_call()
 {
 	using namespace Kernel;
 
-	/* send request and receive reply */
+	/* send request */
 	unsigned const local_name = Ipc_ostream::_dst.local_name();
 	msgbuf_to_utcb(_snd_msg, _write_offset, local_name);
-	int error = request_and_wait(Ipc_ostream::_dst.dst());
-	if (error) { throw Blocking_canceled(); }
+	request_and_wait(Ipc_ostream::_dst.dst());
+
+	/* receive reply */
+	Native_utcb * const utcb = Thread_base::myself()->utcb();
+	if (utcb->msg.type != Msg_type::IPC) {
+		PERR("failed to receive reply");
+		throw Blocking_canceled();
+	}
 	utcb_to_msgbuf(_rcv_msg);
 
 	/* reset unmarshaller */
@@ -161,12 +167,14 @@ void Ipc_server::_prepare_next_reply_wait()
 void Ipc_server::_wait()
 {
 	/* receive next request */
-	int const error = Kernel::wait_for_request();
-	if (!error) { utcb_to_msgbuf(_rcv_msg); }
-	else {
+	Kernel::wait_for_request();
+	Native_utcb * const utcb = Thread_base::myself()->utcb();
+	if (utcb->msg.type != Msg_type::IPC) {
 		PERR("failed to receive request");
 		throw Blocking_canceled();
 	}
+	utcb_to_msgbuf(_rcv_msg);
+
 	/* update server state */
 	_prepare_next_reply_wait();
 }
@@ -182,21 +190,24 @@ void Ipc_server::_reply()
 
 void Ipc_server::_reply_wait()
 {
-	/* if there is no reply simply do wait for request */
-	/* FIXME this shall be not supported */
+	/* if there is no reply, wait for request */
 	if (!_reply_needed) {
 		_wait();
 		return;
 	}
-	/* send reply and receive next request */
+	/* send reply an await request */
 	unsigned const local_name = Ipc_ostream::_dst.local_name();
 	msgbuf_to_utcb(_snd_msg, _write_offset, local_name);
-	int const error = Kernel::reply(1);
-	if (!error) { utcb_to_msgbuf(_rcv_msg); }
-	else {
+	Kernel::reply(1);
+
+	/* fetch request */
+	Native_utcb * const utcb = Thread_base::myself()->utcb();
+	if (utcb->msg.type != Msg_type::IPC) {
 		PERR("failed to receive request");
 		throw Blocking_canceled();
 	}
+	utcb_to_msgbuf(_rcv_msg);
+
 	/* update server state */
 	_prepare_next_reply_wait();
 }

base-hw/src/base/pager.cc

@@ -95,8 +95,12 @@ Pager_capability Pager_entrypoint::manage(Pager_object * const o)
 
 void Ipc_pager::wait_for_first_fault()
 {
-	while (Kernel::wait_for_request()) { PERR("failed to receive fault"); }
 	Native_utcb * const utcb = Thread_base::myself()->utcb();
+	while (1) {
+		Kernel::wait_for_request();
+		if (utcb->msg.type == Msg_type::IPC) { break; }
+		PERR("failed to receive fault");
+	}
 	_wait_for_fault(utcb->ipc_msg.size);
 }
 
@@ -105,12 +109,10 @@ void Ipc_pager::wait_for_fault()
 {
 	Native_utcb * const utcb = Thread_base::myself()->utcb();
 	utcb->ipc_msg.size = 0;
-	int err = Kernel::reply(1);
-	if (err) {
+	Kernel::reply(1);
+	while (utcb->msg.type != Msg_type::IPC) {
 		PERR("failed to receive fault");
-		while (Kernel::wait_for_request()) {
-			PERR("failed to receive fault");
-		}
+		Kernel::wait_for_request();
 	}
 	_wait_for_fault(utcb->ipc_msg.size);
 }
@@ -153,11 +155,10 @@ void Ipc_pager::_wait_for_fault(size_t s)
 			/* resume faulter, send ack to RM and get the next message */
 			Kernel::resume_thread(msg->pager_object->badge());
 			utcb->ipc_msg.size = 0;
-			if (Kernel::reply(1)) {
+			Kernel::reply(1);
+			while (utcb->msg.type != Msg_type::IPC) {
 				PERR("failed to receive fault");
-				while (Kernel::wait_for_request()) {
-					PERR("failed to receive fault");
-				}
+				Kernel::wait_for_request();
 			}
 			s = utcb->ipc_msg.size;
 			continue; }

base-hw/src/core/kernel/thread.cc

@@ -24,6 +24,7 @@
 using namespace Kernel;
 
 typedef Genode::Thread_state Thread_state;
+typedef Genode::Msg_type     Msg_type;
 
 
 bool Thread::_core() const
@@ -90,8 +91,8 @@ void Thread::_received_ipc_request(size_t const s)
 {
 	switch (_state) {
 	case SCHEDULED:
+		_phys_utcb->msg.type = Msg_type::IPC;
 		_phys_utcb->ipc_msg.size = s;
-		user_arg_0(0);
 		return;
 	default:
 		PERR("wrong thread state to receive IPC");
@@ -121,8 +122,8 @@ void Thread::_await_ipc_succeeded(size_t const s)
 {
 	switch (_state) {
 	case AWAITS_IPC:
+		_phys_utcb->msg.type = Msg_type::IPC;
 		_phys_utcb->ipc_msg.size = s;
-		user_arg_0(0);
 		_schedule();
 		return;
 	case AWAITS_PAGER_IPC:
@@ -143,7 +144,7 @@ void Thread::_await_ipc_failed()
 {
 	switch (_state) {
 	case AWAITS_IPC:
-		user_arg_0(-1);
+		_phys_utcb->msg.type = Msg_type::INVALID;
 		_schedule();
 		return;
 	case SCHEDULED:
@@ -641,7 +642,7 @@ void Thread::_syscall_reply()
 		void * const buf_base = _phys_utcb->ipc_msg.data;
 		size_t const buf_size = _phys_utcb->ipc_msg_max_size();
 		Ipc_node::await_request(buf_base, buf_size);
-	} else { user_arg_0(0); }
+	} else { _phys_utcb->msg.type = Msg_type::INVALID; }
 }