示例#1
0
ipc_kmsg_t
ipc_kobject_server(
	ipc_kmsg_t	request)
{
	mach_msg_size_t reply_size;
	ipc_kmsg_t reply;
	kern_return_t kr;
	mig_routine_t routine;
	ipc_port_t *destp;
	mach_msg_format_0_trailer_t *trailer;
	register mig_hash_t *ptr;
#if	MACH_RT
	boolean_t reply_rt;
#endif	/* MACH_RT */
	unsigned int th;

	/* Only fetch current thread if ETAP is configured */
	ETAP_DATA_LOAD(th, current_thread());
        ETAP_PROBE_DATA(ETAP_P_SYSCALL_MACH,
                        EVENT_BEGIN,
			((thread_t) th),
                        &request->ikm_header.msgh_id,
                        sizeof(int));
	/*
         * Find out corresponding mig_hash entry if any
         */
	{
	    register int key = request->ikm_header.msgh_id;
	    register int i = MIG_HASH(key);
	    register int max_iter = mig_table_max_displ;
	
	    do
		ptr = &mig_buckets[i++ % MAX_MIG_ENTRIES];
	    while (key != ptr->num && ptr->num && --max_iter);

	    if (!ptr->routine || key != ptr->num) {
	        ptr = (mig_hash_t *)0;
		reply_size = mig_reply_size;
	    } else {
		reply_size = ptr->size;
#if	MACH_COUNTER
		ptr->callcount++;
#endif
	    }
	}

	/* round up for ikm_cache; overhead is added by ikm_alloc */
        if ((reply_size += MAX_TRAILER_SIZE) < IKM_SAVED_MSG_SIZE)
		reply_size = IKM_SAVED_MSG_SIZE;

#if	MACH_RT
	reply_rt =
	  IP_VALID((ipc_port_t)request->ikm_header.msgh_local_port) ?
	    IP_RT((ipc_port_t)request->ikm_header.msgh_local_port) :
	    FALSE;
	    
	if (reply_rt)
	      reply = ikm_rtalloc(reply_size);
	else
#endif	/* MACH_RT */
	      reply = ikm_alloc(reply_size);

	if (reply == IKM_NULL) {
		printf("ipc_kobject_server: dropping request\n");
		ipc_kmsg_destroy(request);
		return IKM_NULL;
	}

	ikm_init(reply, reply_size);
#if	DIPC
	reply->ikm_handle = HANDLE_NULL;
#endif	/* DIPC */

	/*
	 * Initialize reply message.
	 */
	{
#define	InP	((mach_msg_header_t *) &request->ikm_header)
#define	OutP	((mig_reply_error_t *) &reply->ikm_header)

	    OutP->NDR = NDR_record;
	    OutP->Head.msgh_size = sizeof(mig_reply_error_t);

	    OutP->Head.msgh_bits =
		MACH_MSGH_BITS(MACH_MSGH_BITS_LOCAL(InP->msgh_bits), 0);
	    OutP->Head.msgh_remote_port = InP->msgh_local_port;
	    OutP->Head.msgh_local_port  = MACH_PORT_NULL;
	    OutP->Head.msgh_id = InP->msgh_id + 100;
#if	MACH_RT
	    if (reply_rt)
	          KMSG_MARK_RT(reply);
#endif	/* MACH_RT */
#undef	InP
#undef	OutP
	}

	/*
	 * Find the routine to call, and call it
	 * to perform the kernel function
	 */
	{
	    if (ptr)	
		(*ptr->routine)(&request->ikm_header, &reply->ikm_header);
	    else {
		if (!ipc_kobject_notify(&request->ikm_header, &reply->ikm_header)){
#if	MACH_IPC_TEST
		    printf("ipc_kobject_server: bogus kernel message, id=%d\n",
			request->ikm_header.msgh_id);
#endif	/* MACH_IPC_TEST */
		    ((mig_reply_error_t *) &reply->ikm_header)->RetCode
			= MIG_BAD_ID;
		}
	    }
	}

	/*
	 *	Destroy destination. The following code differs from
	 *	ipc_object_destroy in that we release the send-once
	 *	right instead of generating a send-once notification
	 * 	(which would bring us here again, creating a loop).
	 *	It also differs in that we only expect send or
	 *	send-once rights, never receive rights.
	 *
	 *	We set msgh_remote_port to IP_NULL so that the kmsg
	 *	destroy routines don't try to destroy the port twice.
	 */
	destp = (ipc_port_t *) &request->ikm_header.msgh_remote_port;
	switch (MACH_MSGH_BITS_REMOTE(request->ikm_header.msgh_bits)) {
		case MACH_MSG_TYPE_PORT_SEND:
		    ipc_port_release_send(*destp);
		    break;
		
		case MACH_MSG_TYPE_PORT_SEND_ONCE:
		    ipc_port_release_sonce(*destp);
		    break;
		
		default:
		    panic("ipc_object_destroy: strange destination rights");
	}
	*destp = IP_NULL;

        if (!(reply->ikm_header.msgh_bits & MACH_MSGH_BITS_COMPLEX) &&
           ((mig_reply_error_t *) &reply->ikm_header)->RetCode != KERN_SUCCESS)
	 	kr = ((mig_reply_error_t *) &reply->ikm_header)->RetCode;
	else
		kr = KERN_SUCCESS;

	if ((kr == KERN_SUCCESS) || (kr == MIG_NO_REPLY)) {
		/*
		 *	The server function is responsible for the contents
		 *	of the message.  The reply port right is moved
		 *	to the reply message, and we have deallocated
		 *	the destination port right, so we just need
		 *	to free the kmsg.
		 */

		/*
		 * Like ipc_kmsg_put, but without the copyout.  Also,
		 * messages to the kernel will never have been allocated
		 * from the rt_zone.
		 */

		ikm_check_initialized(request, request->ikm_size);
		if (request->ikm_size != IKM_SAVED_KMSG_SIZE ||
		    !ikm_cache_put (request)) {
			ikm_free(request);
		}
	} else {
		/*
		 *	The message contents of the request are intact.
		 *	Destroy everthing except the reply port right,
		 *	which is needed in the reply message.
		 */

		request->ikm_header.msgh_local_port = MACH_PORT_NULL;
		ipc_kmsg_destroy(request);
	}

	if (kr == MIG_NO_REPLY) {
		/*
		 *	The server function will send a reply message
		 *	using the reply port right, which it has saved.
		 */

		ikm_free(reply);

		ETAP_PROBE_DATA(ETAP_P_SYSCALL_MACH,
				EVENT_END,
				((thread_t) th),
				&request->ikm_header.msgh_id,
				sizeof(int));

		return IKM_NULL;
	} else if (!IP_VALID((ipc_port_t)reply->ikm_header.msgh_remote_port)) {
		/*
		 *	Can't queue the reply message if the destination
		 *	(the reply port) isn't valid.
		 */

		ipc_kmsg_destroy(reply);

		ETAP_PROBE_DATA(ETAP_P_SYSCALL_MACH,
				EVENT_END,
				((thread_t) th),
				&request->ikm_header.msgh_id,
				sizeof(int));

		return IKM_NULL;
	}

 	trailer = (mach_msg_format_0_trailer_t *)
		((vm_offset_t)&reply->ikm_header + (int)reply->ikm_header.msgh_size);                
 	trailer->msgh_sender = KERNEL_SECURITY_TOKEN;
 	trailer->msgh_trailer_type = MACH_MSG_TRAILER_FORMAT_0;
 	trailer->msgh_trailer_size = MACH_MSG_TRAILER_MINIMUM_SIZE;

        ETAP_PROBE_DATA(ETAP_P_SYSCALL_MACH,
                        EVENT_END,
			((thread_t) th),
                        &request->ikm_header.msgh_id,
                        sizeof(int));

	return reply;
}
示例#2
0
mach_msg_return_t
mach_msg_trap(
	mach_msg_header_t 	*msg,
	mach_msg_option_t 	option,
	mach_msg_size_t 	send_size,
	mach_msg_size_t 	rcv_size,
	mach_port_t 		rcv_name,
	mach_msg_timeout_t 	time_out,
	mach_port_t 		notify)
{
	mach_msg_return_t mr;

	/* first check for common cases */

	if (option == (MACH_SEND_MSG|MACH_RCV_MSG)) {
		ipc_thread_t self = current_thread();
		ipc_space_t space = self->task->itk_space;
		ipc_kmsg_t kmsg;
		ipc_port_t dest_port;
		ipc_object_t rcv_object;
		ipc_mqueue_t rcv_mqueue;
		mach_msg_size_t reply_size;

		/*
		 *	This case is divided into ten sections, each
		 *	with a label.  There are five optimized
		 *	sections and six unoptimized sections, which
		 *	do the same thing but handle all possible
		 *	cases and are slower.
		 *
		 *	The five sections for an RPC are
		 *	    1) Get request message into a buffer.
		 *		(fast_get or slow_get)
		 *	    2) Copyin request message and rcv_name.
		 *		(fast_copyin or slow_copyin)
		 *	    3) Enqueue request and dequeue reply.
		 *		(fast_send_receive or
		 *		 slow_send and slow_receive)
		 *	    4) Copyout reply message.
		 *		(fast_copyout or slow_copyout)
		 *	    5) Put reply message to user's buffer.
		 *		(fast_put or slow_put)
		 *
		 *	Keep the locking hierarchy firmly in mind.
		 *	(First spaces, then ports, then port sets,
		 *	then message queues.)  Only a non-blocking
		 *	attempt can be made to acquire locks out of
		 *	order, or acquire two locks on the same level.
		 *	Acquiring two locks on the same level will
		 *	fail if the objects are really the same,
		 *	unless simple locking is disabled.  This is OK,
		 *	because then the extra unlock does nothing.
		 *
		 *	There are two major reasons these RPCs can't use
		 *	ipc_thread_switch, and use slow_send/slow_receive:
		 *		1) Kernel RPCs.
		 *		2) Servers fall behind clients, so
		 *		client doesn't find a blocked server thread and
		 *		server finds waiting messages and can't block.
		 */

	/*
	    fast_get:
	*/
		/*
		 *	optimized ipc_kmsg_get
		 *
		 *	No locks, references, or messages held.
		 *	We must clear ikm_cache before copyinmsg.
		 */

		if ((send_size > IKM_SAVED_MSG_SIZE) ||
		    (send_size < sizeof(mach_msg_header_t)) ||
		    (send_size & 3) ||
		    ((kmsg = ikm_cache()) == IKM_NULL))
			goto slow_get;

		ikm_cache() = IKM_NULL;
		ikm_check_initialized(kmsg, IKM_SAVED_KMSG_SIZE);

		if (copyinmsg(msg, &kmsg->ikm_header,
			      send_size)) {
			ikm_free(kmsg);
			goto slow_get;
		}

		kmsg->ikm_header.msgh_size = send_size;

	    fast_copyin:
		/*
		 *	optimized ipc_kmsg_copyin/ipc_mqueue_copyin
		 *
		 *	We have the request message data in kmsg.
		 *	Must still do copyin, send, receive, etc.
		 *
		 *	If the message isn't simple, we can't combine
		 *	ipc_kmsg_copyin_header and ipc_mqueue_copyin,
		 *	because copyin of the message body might
		 *	affect rcv_name.
		 */

		switch (kmsg->ikm_header.msgh_bits) {
		    case MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND,
					MACH_MSG_TYPE_MAKE_SEND_ONCE): {
			ipc_entry_t table;
			ipc_entry_num_t size;
			ipc_port_t reply_port;

			/* sending a request message */

		    {
			mach_port_index_t index;
			mach_port_gen_t gen;

		    {
			mach_port_t reply_name =
				kmsg->ikm_header.msgh_local_port;

			if (reply_name != rcv_name)
				goto slow_copyin;

			/* optimized ipc_entry_lookup of reply_name */

			index = MACH_PORT_INDEX(reply_name);
			gen = MACH_PORT_GEN(reply_name);
		    }

			is_read_lock(space);
			assert(space->is_active);

			size = space->is_table_size;
			table = space->is_table;

			if (index >= size)
				goto abort_request_copyin;

		    {
			ipc_entry_t entry;
			ipc_entry_bits_t bits;

			entry = &table[index];
			bits = entry->ie_bits;

			/* check generation number and type bit */

			if ((bits & (IE_BITS_GEN_MASK|
				     MACH_PORT_TYPE_RECEIVE)) !=
			    (gen | MACH_PORT_TYPE_RECEIVE))
				goto abort_request_copyin;

			reply_port = (ipc_port_t) entry->ie_object;
			assert(reply_port != IP_NULL);
		    }
		    }

			/* optimized ipc_entry_lookup of dest_name */

		    {
			mach_port_index_t index;
			mach_port_gen_t gen;

		    {
			mach_port_t dest_name =
				kmsg->ikm_header.msgh_remote_port;

			index = MACH_PORT_INDEX(dest_name);
			gen = MACH_PORT_GEN(dest_name);
		    }

			if (index >= size)
				goto abort_request_copyin;

		    {
			ipc_entry_t entry;
			ipc_entry_bits_t bits;

			entry = &table[index];
			bits = entry->ie_bits;

			/* check generation number and type bit */

			if ((bits & (IE_BITS_GEN_MASK|MACH_PORT_TYPE_SEND)) !=
			    (gen | MACH_PORT_TYPE_SEND))
				goto abort_request_copyin;

			assert(IE_BITS_UREFS(bits) > 0);

			dest_port = (ipc_port_t) entry->ie_object;
			assert(dest_port != IP_NULL);
		    }
		    }

			/*
			 *	To do an atomic copyin, need simultaneous
			 *	locks on both ports and the space.  If
			 *	dest_port == reply_port, and simple locking is
			 *	enabled, then we will abort.  Otherwise it's
			 *	OK to unlock twice.
			 */

			ip_lock(dest_port);
			if (!ip_active(dest_port) ||
			    !ip_lock_try(reply_port)) {
				ip_unlock(dest_port);
				goto abort_request_copyin;
			}
			is_read_unlock(space);

			assert(dest_port->ip_srights > 0);
			dest_port->ip_srights++;
			ip_reference(dest_port);

			assert(ip_active(reply_port));
			assert(reply_port->ip_receiver_name ==
			       kmsg->ikm_header.msgh_local_port);
			assert(reply_port->ip_receiver == space);

			reply_port->ip_sorights++;
			ip_reference(reply_port);

			kmsg->ikm_header.msgh_bits =
				MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND,
					       MACH_MSG_TYPE_PORT_SEND_ONCE);
			kmsg->ikm_header.msgh_remote_port =
					(mach_port_t) dest_port;
			kmsg->ikm_header.msgh_local_port =
					(mach_port_t) reply_port;

			/* make sure we can queue to the destination */

			if (dest_port->ip_receiver == ipc_space_kernel) {
				/*
				 * The kernel server has a reference to
				 * the reply port, which it hands back
				 * to us in the reply message.  We do
				 * not need to keep another reference to
				 * it.
				 */
				ip_unlock(reply_port);

				assert(ip_active(dest_port));
				ip_unlock(dest_port);
				goto kernel_send;
			}

			if (dest_port->ip_msgcount >= dest_port->ip_qlimit)
				goto abort_request_send_receive;

			/* optimized ipc_mqueue_copyin */

			if (reply_port->ip_pset != IPS_NULL)
				goto abort_request_send_receive;

			rcv_object = (ipc_object_t) reply_port;
			io_reference(rcv_object);
			rcv_mqueue = &reply_port->ip_messages;
			imq_lock(rcv_mqueue);
			io_unlock(rcv_object);
			goto fast_send_receive;

		    abort_request_copyin:
			is_read_unlock(space);
			goto slow_copyin;

		    abort_request_send_receive:
			ip_unlock(dest_port);
			ip_unlock(reply_port);
			goto slow_send;
		    }

		    case MACH_MSGH_BITS(MACH_MSG_TYPE_MOVE_SEND_ONCE, 0): {
			ipc_entry_num_t size;
			ipc_entry_t table;

			/* sending a reply message */

		    {
			mach_port_t reply_name =
				kmsg->ikm_header.msgh_local_port;

			if (reply_name != MACH_PORT_NULL)
				goto slow_copyin;
		    }

			is_write_lock(space);
			assert(space->is_active);

			/* optimized ipc_entry_lookup */

			size = space->is_table_size;
			table = space->is_table;

		    {
			ipc_entry_t entry;
			mach_port_gen_t gen;
			mach_port_index_t index;

		    {
			mach_port_t dest_name =
				kmsg->ikm_header.msgh_remote_port;

			index = MACH_PORT_INDEX(dest_name);
			gen = MACH_PORT_GEN(dest_name);
		    }

			if (index >= size)
				goto abort_reply_dest_copyin;

			entry = &table[index];

			/* check generation, collision bit, and type bit */

			if ((entry->ie_bits & (IE_BITS_GEN_MASK|
					       IE_BITS_COLLISION|
					       MACH_PORT_TYPE_SEND_ONCE)) !=
			    (gen | MACH_PORT_TYPE_SEND_ONCE))
				goto abort_reply_dest_copyin;

			/* optimized ipc_right_copyin */

			assert(IE_BITS_TYPE(entry->ie_bits) ==
						MACH_PORT_TYPE_SEND_ONCE);
			assert(IE_BITS_UREFS(entry->ie_bits) == 1);
			assert((entry->ie_bits & IE_BITS_MAREQUEST) == 0);

			if (entry->ie_request != 0)
				goto abort_reply_dest_copyin;

			dest_port = (ipc_port_t) entry->ie_object;
			assert(dest_port != IP_NULL);

			ip_lock(dest_port);
			if (!ip_active(dest_port)) {
				ip_unlock(dest_port);
				goto abort_reply_dest_copyin;
			}

			assert(dest_port->ip_sorights > 0);

			/* optimized ipc_entry_dealloc */

			entry->ie_next = table->ie_next;
			table->ie_next = index;
			entry->ie_bits = gen;
			entry->ie_object = IO_NULL;
		    }

			kmsg->ikm_header.msgh_bits =
				MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND_ONCE,
					       0);
			kmsg->ikm_header.msgh_remote_port =
					(mach_port_t) dest_port;

			/* make sure we can queue to the destination */

			assert(dest_port->ip_receiver != ipc_space_kernel);

			/* optimized ipc_entry_lookup/ipc_mqueue_copyin */

		    {
			ipc_entry_t entry;
			ipc_entry_bits_t bits;

		    {
			mach_port_index_t index;
			mach_port_gen_t gen;

			index = MACH_PORT_INDEX(rcv_name);
			gen = MACH_PORT_GEN(rcv_name);

			if (index >= size)
				goto abort_reply_rcv_copyin;

			entry = &table[index];
			bits = entry->ie_bits;

			/* check generation number */

			if ((bits & IE_BITS_GEN_MASK) != gen)
				goto abort_reply_rcv_copyin;
		    }

			/* check type bits; looking for receive or set */

			if (bits & MACH_PORT_TYPE_PORT_SET) {
				ipc_pset_t rcv_pset;

				rcv_pset = (ipc_pset_t) entry->ie_object;
				assert(rcv_pset != IPS_NULL);

				ips_lock(rcv_pset);
				assert(ips_active(rcv_pset));

				rcv_object = (ipc_object_t) rcv_pset;
				rcv_mqueue = &rcv_pset->ips_messages;
			} else if (bits & MACH_PORT_TYPE_RECEIVE) {
				ipc_port_t rcv_port;

				rcv_port = (ipc_port_t) entry->ie_object;
				assert(rcv_port != IP_NULL);

				if (!ip_lock_try(rcv_port))
					goto abort_reply_rcv_copyin;
				assert(ip_active(rcv_port));

				if (rcv_port->ip_pset != IPS_NULL) {
					ip_unlock(rcv_port);
					goto abort_reply_rcv_copyin;
				}

				rcv_object = (ipc_object_t) rcv_port;
				rcv_mqueue = &rcv_port->ip_messages;
			} else
				goto abort_reply_rcv_copyin;
		    }

			is_write_unlock(space);
			io_reference(rcv_object);
			imq_lock(rcv_mqueue);
			io_unlock(rcv_object);
			goto fast_send_receive;

		    abort_reply_dest_copyin:
			is_write_unlock(space);
			goto slow_copyin;

		    abort_reply_rcv_copyin:
			ip_unlock(dest_port);
			is_write_unlock(space);
			goto slow_send;
		    }

		    default:
			goto slow_copyin;
		}
		/*NOTREACHED*/

	    fast_send_receive:
		/*
		 *	optimized ipc_mqueue_send/ipc_mqueue_receive
		 *
		 *	Finished get/copyin of kmsg and copyin of rcv_name.
		 *	space is unlocked, dest_port is locked,
		 *	we can queue kmsg to dest_port,
		 *	rcv_mqueue is locked, rcv_object holds a ref,
		 *	if rcv_object is a port it isn't in a port set
		 *
		 *	Note that if simple locking is turned off,
		 *	then we could have dest_mqueue == rcv_mqueue
		 *	and not abort when we try to lock dest_mqueue.
		 */

		assert(ip_active(dest_port));
		assert(dest_port->ip_receiver != ipc_space_kernel);
		assert((dest_port->ip_msgcount < dest_port->ip_qlimit) ||
		       (MACH_MSGH_BITS_REMOTE(kmsg->ikm_header.msgh_bits) ==
						MACH_MSG_TYPE_PORT_SEND_ONCE));
		assert((kmsg->ikm_header.msgh_bits &
						MACH_MSGH_BITS_CIRCULAR) == 0);

	    {
		ipc_mqueue_t dest_mqueue;
		ipc_thread_t receiver;

	    {
		ipc_pset_t dest_pset;

		dest_pset = dest_port->ip_pset;
		if (dest_pset == IPS_NULL)
			dest_mqueue = &dest_port->ip_messages;
		else
			dest_mqueue = &dest_pset->ips_messages;
	    }

		if (!imq_lock_try(dest_mqueue)) {
		    abort_send_receive:
			ip_unlock(dest_port);
			imq_unlock(rcv_mqueue);
			ipc_object_release(rcv_object);
			goto slow_send;
		}

		receiver = ipc_thread_queue_first(&dest_mqueue->imq_threads);
		if ((receiver == ITH_NULL) ||
		    (ipc_kmsg_queue_first(&rcv_mqueue->imq_messages)
								!= IKM_NULL)) {
			imq_unlock(dest_mqueue);
			goto abort_send_receive;
		}

		/*
		 *	There is a receiver thread waiting, and
		 *	there is no reply message for us to pick up.
		 *	We have hope of hand-off, so save state.
		 */

		self->ith_msg = msg;
		self->ith_rcv_size = rcv_size;
		self->ith_object = rcv_object;
		self->ith_mqueue = rcv_mqueue;

		if ((receiver->swap_func == (void (*)()) mach_msg_continue) &&
		    thread_handoff(self, mach_msg_continue, receiver)) {
			assert(current_thread() == receiver);

			/*
			 *	We can use the optimized receive code,
			 *	because the receiver is using no options.
			 */
		} else if ((receiver->swap_func ==
				(void (*)()) exception_raise_continue) &&
			   thread_handoff(self, mach_msg_continue, receiver)) {
			counter(c_mach_msg_trap_block_exc++);
			assert(current_thread() == receiver);

			/*
			 *	We are a reply message coming back through
			 *	the optimized exception-handling path.
			 *	Finish with rcv_mqueue and dest_mqueue,
			 *	and then jump to exception code with
			 *	dest_port still locked.  We don't bother
			 *	with a sequence number in this case.
			 */

			ipc_thread_enqueue_macro(
				&rcv_mqueue->imq_threads, self);
			self->ith_state = MACH_RCV_IN_PROGRESS;
			self->ith_msize = MACH_MSG_SIZE_MAX;
			imq_unlock(rcv_mqueue);

			ipc_thread_rmqueue_first_macro(
				&dest_mqueue->imq_threads, receiver);
			imq_unlock(dest_mqueue);

			exception_raise_continue_fast(dest_port, kmsg);
			/*NOTREACHED*/
			return MACH_MSG_SUCCESS;
		} else if ((send_size <= receiver->ith_msize) &&
			   thread_handoff(self, mach_msg_continue, receiver)) {
			assert(current_thread() == receiver);

			if ((receiver->swap_func ==
				(void (*)()) mach_msg_receive_continue) &&
			    ((receiver->ith_option & MACH_RCV_NOTIFY) == 0)) {
				/*
				 *	We can still use the optimized code.
				 */
			} else {
				counter(c_mach_msg_trap_block_slow++);
				/*
				 *	We are running as the receiver,
				 *	but we can't use the optimized code.
				 *	Finish send/receive processing.
				 */

				dest_port->ip_msgcount++;
				ip_unlock(dest_port);

				ipc_thread_enqueue_macro(
					&rcv_mqueue->imq_threads, self);
				self->ith_state = MACH_RCV_IN_PROGRESS;
				self->ith_msize = MACH_MSG_SIZE_MAX;
				imq_unlock(rcv_mqueue);

				ipc_thread_rmqueue_first_macro(
					&dest_mqueue->imq_threads, receiver);
				receiver->ith_state = MACH_MSG_SUCCESS;
				receiver->ith_kmsg = kmsg;
				receiver->ith_seqno = dest_port->ip_seqno++;
				imq_unlock(dest_mqueue);

				/*
				 *	Call the receiver's continuation.
				 */

				receiver->wait_result = THREAD_AWAKENED;
				(*receiver->swap_func)();
				/*NOTREACHED*/
				return MACH_MSG_SUCCESS;
			}
		} else {
			/*
			 *	The receiver can't accept the message,
			 *	or we can't switch to the receiver.
			 */

			imq_unlock(dest_mqueue);
			goto abort_send_receive;
		}
		counter(c_mach_msg_trap_block_fast++);

		/*
		 *	Safe to unlock dest_port now that we are
		 *	committed to this path, because we hold
		 *	dest_mqueue locked.  We never bother changing
		 *	dest_port->ip_msgcount.
		 */

		ip_unlock(dest_port);

		/*
		 *	We need to finish preparing self for its
		 *	time asleep in rcv_mqueue.
		 */

		ipc_thread_enqueue_macro(&rcv_mqueue->imq_threads, self);
		self->ith_state = MACH_RCV_IN_PROGRESS;
		self->ith_msize = MACH_MSG_SIZE_MAX;
		imq_unlock(rcv_mqueue);

		/*
		 *	Finish extracting receiver from dest_mqueue.
		 */

		ipc_thread_rmqueue_first_macro(
			&dest_mqueue->imq_threads, receiver);
		kmsg->ikm_header.msgh_seqno = dest_port->ip_seqno++;
		imq_unlock(dest_mqueue);

		/*
		 *	We don't have to do any post-dequeue processing of
		 *	the message.  We never incremented ip_msgcount, we
		 *	know it has no msg-accepted request, and blocked
		 *	senders aren't a worry because we found the port
		 *	with a receiver waiting.
		 */

		self = receiver;
		space = self->task->itk_space;

		msg = self->ith_msg;
		rcv_size = self->ith_rcv_size;
		rcv_object = self->ith_object;

		/* inline ipc_object_release */
		io_lock(rcv_object);
		io_release(rcv_object);
		io_check_unlock(rcv_object);
	    }

	    fast_copyout:
		/*
		 *	Nothing locked and no references held, except
		 *	we have kmsg with msgh_seqno filled in.  Must
		 *	still check against rcv_size and do
		 *	ipc_kmsg_copyout/ipc_kmsg_put.
		 */

		assert((ipc_port_t) kmsg->ikm_header.msgh_remote_port
						== dest_port);

		reply_size = kmsg->ikm_header.msgh_size;
		if (rcv_size < reply_size)
			goto slow_copyout;

		/* optimized ipc_kmsg_copyout/ipc_kmsg_copyout_header */

		switch (kmsg->ikm_header.msgh_bits) {
		    case MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND,
					MACH_MSG_TYPE_PORT_SEND_ONCE): {
			ipc_port_t reply_port =
				(ipc_port_t) kmsg->ikm_header.msgh_local_port;
			mach_port_t dest_name, reply_name;

			/* receiving a request message */

			if (!IP_VALID(reply_port))
				goto slow_copyout;

			is_write_lock(space);
			assert(space->is_active);

			/*
			 *	To do an atomic copyout, need simultaneous
			 *	locks on both ports and the space.  If
			 *	dest_port == reply_port, and simple locking is
			 *	enabled, then we will abort.  Otherwise it's
			 *	OK to unlock twice.
			 */

			ip_lock(dest_port);
			if (!ip_active(dest_port) ||
			    !ip_lock_try(reply_port))
				goto abort_request_copyout;

			if (!ip_active(reply_port)) {
				ip_unlock(reply_port);
				goto abort_request_copyout;
			}

			assert(reply_port->ip_sorights > 0);
			ip_unlock(reply_port);

		    {
			ipc_entry_t table;
			ipc_entry_t entry;
			mach_port_index_t index;

			/* optimized ipc_entry_get */

			table = space->is_table;
			index = table->ie_next;

			if (index == 0)
				goto abort_request_copyout;

			entry = &table[index];
			table->ie_next = entry->ie_next;
			entry->ie_request = 0;

		    {
			mach_port_gen_t gen;

			assert((entry->ie_bits &~ IE_BITS_GEN_MASK) == 0);
			gen = entry->ie_bits + IE_BITS_GEN_ONE;

			reply_name = MACH_PORT_MAKE(index, gen);

			/* optimized ipc_right_copyout */

			entry->ie_bits = gen | (MACH_PORT_TYPE_SEND_ONCE | 1);
		    }

			assert(MACH_PORT_VALID(reply_name));
			entry->ie_object = (ipc_object_t) reply_port;
			is_write_unlock(space);
		    }

			/* optimized ipc_object_copyout_dest */

			assert(dest_port->ip_srights > 0);
			ip_release(dest_port);

			if (dest_port->ip_receiver == space)
				dest_name = dest_port->ip_receiver_name;
			else
				dest_name = MACH_PORT_NULL;

			if ((--dest_port->ip_srights == 0) &&
			    (dest_port->ip_nsrequest != IP_NULL)) {
				ipc_port_t nsrequest;
				mach_port_mscount_t mscount;

				/* a rather rare case */

				nsrequest = dest_port->ip_nsrequest;
				mscount = dest_port->ip_mscount;
				dest_port->ip_nsrequest = IP_NULL;
				ip_unlock(dest_port);

				ipc_notify_no_senders(nsrequest, mscount);
			} else
				ip_unlock(dest_port);

			if (! ipc_port_flag_protected_payload(dest_port)) {
				kmsg->ikm_header.msgh_bits = MACH_MSGH_BITS(
					MACH_MSG_TYPE_PORT_SEND_ONCE,
					MACH_MSG_TYPE_PORT_SEND);
				kmsg->ikm_header.msgh_local_port = dest_name;
			} else {
				kmsg->ikm_header.msgh_bits = MACH_MSGH_BITS(
					MACH_MSG_TYPE_PORT_SEND_ONCE,
					MACH_MSG_TYPE_PROTECTED_PAYLOAD);
				kmsg->ikm_header.msgh_protected_payload =
					dest_port->ip_protected_payload;
			}
			kmsg->ikm_header.msgh_remote_port = reply_name;
			goto fast_put;

		    abort_request_copyout:
			ip_unlock(dest_port);
			is_write_unlock(space);
			goto slow_copyout;
		    }

		    case MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND_ONCE, 0): {
			mach_port_t dest_name;

			/* receiving a reply message */

			ip_lock(dest_port);
			if (!ip_active(dest_port))
				goto slow_copyout;

			/* optimized ipc_object_copyout_dest */

			assert(dest_port->ip_sorights > 0);

			if (dest_port->ip_receiver == space) {
				ip_release(dest_port);
				dest_port->ip_sorights--;
				dest_name = dest_port->ip_receiver_name;
				ip_unlock(dest_port);
			} else {
				ip_unlock(dest_port);

				ipc_notify_send_once(dest_port);
				dest_name = MACH_PORT_NULL;
			}

			if (! ipc_port_flag_protected_payload(dest_port)) {
				kmsg->ikm_header.msgh_bits = MACH_MSGH_BITS(
					0,
					MACH_MSG_TYPE_PORT_SEND_ONCE);
				kmsg->ikm_header.msgh_local_port = dest_name;
			} else {
				kmsg->ikm_header.msgh_bits = MACH_MSGH_BITS(
					0,
					MACH_MSG_TYPE_PROTECTED_PAYLOAD);
				kmsg->ikm_header.msgh_protected_payload =
					dest_port->ip_protected_payload;
			}
			kmsg->ikm_header.msgh_remote_port = MACH_PORT_NULL;
			goto fast_put;
		    }

		    case MACH_MSGH_BITS_COMPLEX|
			 MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND_ONCE, 0): {
			mach_port_t dest_name;

			/* receiving a complex reply message */

			ip_lock(dest_port);
			if (!ip_active(dest_port))
				goto slow_copyout;

			/* optimized ipc_object_copyout_dest */

			assert(dest_port->ip_sorights > 0);

			if (dest_port->ip_receiver == space) {
				ip_release(dest_port);
				dest_port->ip_sorights--;
				dest_name = dest_port->ip_receiver_name;
				ip_unlock(dest_port);
			} else {
				ip_unlock(dest_port);

				ipc_notify_send_once(dest_port);
				dest_name = MACH_PORT_NULL;
			}

			if (! ipc_port_flag_protected_payload(dest_port)) {
				kmsg->ikm_header.msgh_bits =
					MACH_MSGH_BITS_COMPLEX
					| MACH_MSGH_BITS(
						0,
						MACH_MSG_TYPE_PORT_SEND_ONCE);
				kmsg->ikm_header.msgh_local_port = dest_name;
			} else {
				kmsg->ikm_header.msgh_bits =
					MACH_MSGH_BITS_COMPLEX
					| MACH_MSGH_BITS(
					    0,
					    MACH_MSG_TYPE_PROTECTED_PAYLOAD);
				kmsg->ikm_header.msgh_protected_payload =
					dest_port->ip_protected_payload;
			}
			kmsg->ikm_header.msgh_remote_port = MACH_PORT_NULL;

			mr = ipc_kmsg_copyout_body(
				(vm_offset_t) (&kmsg->ikm_header + 1),
				(vm_offset_t) &kmsg->ikm_header
					+ kmsg->ikm_header.msgh_size,
				space,
				current_map());

			if (mr != MACH_MSG_SUCCESS) {
				(void) ipc_kmsg_put(msg, kmsg,
					kmsg->ikm_header.msgh_size);
				return mr | MACH_RCV_BODY_ERROR;
			}
			goto fast_put;
		    }

		    default:
			goto slow_copyout;
		}
		/*NOTREACHED*/

	    fast_put:
		/*
		 *	We have the reply message data in kmsg,
		 *	and the reply message size in reply_size.
		 *	Just need to copy it out to the user and free kmsg.
		 *	We must check ikm_cache after copyoutmsg.
		 */

		ikm_check_initialized(kmsg, kmsg->ikm_size);

		if ((kmsg->ikm_size != IKM_SAVED_KMSG_SIZE) ||
		    copyoutmsg(&kmsg->ikm_header, msg,
			       reply_size) ||
		    (ikm_cache() != IKM_NULL))
			goto slow_put;

		ikm_cache() = kmsg;
		thread_syscall_return(MACH_MSG_SUCCESS);
		/*NOTREACHED*/
		return MACH_MSG_SUCCESS; /* help for the compiler */

		/*
		 *	The slow path has a few non-register temporary
		 *	variables used only for call-by-reference.
		 */

	    {
		ipc_kmsg_t temp_kmsg;
		mach_port_seqno_t temp_seqno;
		ipc_object_t temp_rcv_object;
		ipc_mqueue_t temp_rcv_mqueue;

	    slow_get:
		/*
		 *	No locks, references, or messages held.
		 *	Still have to get the request, send it,
		 *	receive reply, etc.
		 */

		mr = ipc_kmsg_get(msg, send_size, &temp_kmsg);
		if (mr != MACH_MSG_SUCCESS) {
			thread_syscall_return(mr);
			/*NOTREACHED*/
		}
		kmsg = temp_kmsg;

		/* try to get back on optimized path */
		goto fast_copyin;

	    slow_copyin:
		/*
		 *	We have the message data in kmsg, but
		 *	we still need to copyin, send it,
		 *	receive a reply, and do copyout.
		 */

		mr = ipc_kmsg_copyin(kmsg, space, current_map(),
				     MACH_PORT_NULL);
		if (mr != MACH_MSG_SUCCESS) {
			ikm_free(kmsg);
			thread_syscall_return(mr);
			/*NOTREACHED*/
		}

		/* try to get back on optimized path */

		if (kmsg->ikm_header.msgh_bits & MACH_MSGH_BITS_CIRCULAR)
			goto slow_send;

		dest_port = (ipc_port_t) kmsg->ikm_header.msgh_remote_port;
		assert(IP_VALID(dest_port));

		ip_lock(dest_port);
		if (dest_port->ip_receiver == ipc_space_kernel) {
			assert(ip_active(dest_port));
			ip_unlock(dest_port);
			goto kernel_send;
		}

		if (ip_active(dest_port) &&
		    ((dest_port->ip_msgcount < dest_port->ip_qlimit) ||
		     (MACH_MSGH_BITS_REMOTE(kmsg->ikm_header.msgh_bits) ==
					MACH_MSG_TYPE_PORT_SEND_ONCE)))
		{
		    /*
		     *	Try an optimized ipc_mqueue_copyin.
		     *	It will work if this is a request message.
		     */

		    ipc_port_t reply_port;

		    reply_port = (ipc_port_t)
					kmsg->ikm_header.msgh_local_port;
		    if (IP_VALID(reply_port)) {
			if (ip_lock_try(reply_port)) {
			    if (ip_active(reply_port) &&
				reply_port->ip_receiver == space &&
				reply_port->ip_receiver_name == rcv_name &&
				reply_port->ip_pset == IPS_NULL)
			    {
				/* Grab a reference to the reply port. */
				rcv_object = (ipc_object_t) reply_port;
				io_reference(rcv_object);
				rcv_mqueue = &reply_port->ip_messages;
				imq_lock(rcv_mqueue);
				io_unlock(rcv_object);
				goto fast_send_receive;
			    }
			    ip_unlock(reply_port);
			}
		    }
		}

		ip_unlock(dest_port);
		goto slow_send;

	    kernel_send:
		/*
		 *	Special case: send message to kernel services.
		 *	The request message has been copied into the
		 *	kmsg.  Nothing is locked.
		 */

	    {
		ipc_port_t	reply_port;

		/*
		 * Perform the kernel function.
		 */

		kmsg = ipc_kobject_server(kmsg);
		if (kmsg == IKM_NULL) {
			/*
			 * No reply.  Take the
			 * slow receive path.
			 */
			goto slow_get_rcv_port;
		}

		/*
		 * Check that:
		 *	the reply port is alive
		 *	we hold the receive right
		 *	the name has not changed.
		 *	the port is not in a set
		 * If any of these are not true,
		 * we cannot directly receive the reply
		 * message.
		 */
		reply_port = (ipc_port_t) kmsg->ikm_header.msgh_remote_port;
		ip_lock(reply_port);

		if ((!ip_active(reply_port)) ||
		    (reply_port->ip_receiver != space) ||
		    (reply_port->ip_receiver_name != rcv_name) ||
		    (reply_port->ip_pset != IPS_NULL))
		{
			ip_unlock(reply_port);
			ipc_mqueue_send_always(kmsg);
			goto slow_get_rcv_port;
		}

		rcv_mqueue = &reply_port->ip_messages;
		imq_lock(rcv_mqueue);
		/* keep port locked, and don`t change ref count yet */

		/*
		 * If there are messages on the port
		 * or other threads waiting for a message,
		 * we cannot directly receive the reply.
		 */
		if ((ipc_thread_queue_first(&rcv_mqueue->imq_threads)
			!= ITH_NULL) ||
		    (ipc_kmsg_queue_first(&rcv_mqueue->imq_messages)
			!= IKM_NULL))
		{
			imq_unlock(rcv_mqueue);
			ip_unlock(reply_port);
			ipc_mqueue_send_always(kmsg);
			goto slow_get_rcv_port;
		}

		/*
		 * We can directly receive this reply.
		 * Since the kernel reply never blocks,
		 * it holds no message_accepted request.
		 * Since there were no messages queued
		 * on the reply port, there should be
		 * no threads blocked waiting to send.
		 */

		assert(kmsg->ikm_marequest == IMAR_NULL);
		assert(ipc_thread_queue_first(&reply_port->ip_blocked)
				== ITH_NULL);

		dest_port = reply_port;
		kmsg->ikm_header.msgh_seqno = dest_port->ip_seqno++;
		imq_unlock(rcv_mqueue);

		/*
		 * inline ipc_object_release.
		 * Port is still locked.
		 * Reference count was not incremented.
		 */
		ip_check_unlock(reply_port);

		/* copy out the kernel reply */
		goto fast_copyout;
	    }

	    slow_send:
		/*
		 *	Nothing is locked.  We have acquired kmsg, but
		 *	we still need to send it and receive a reply.
		 */

		mr = ipc_mqueue_send(kmsg, MACH_MSG_OPTION_NONE,
				     MACH_MSG_TIMEOUT_NONE);
		if (mr != MACH_MSG_SUCCESS) {
			mr |= ipc_kmsg_copyout_pseudo(kmsg, space,
						      current_map());

			assert(kmsg->ikm_marequest == IMAR_NULL);
			(void) ipc_kmsg_put(msg, kmsg,
					    kmsg->ikm_header.msgh_size);
			thread_syscall_return(mr);
			/*NOTREACHED*/
		}

	    slow_get_rcv_port:
		/*
		 * We have sent the message.  Copy in the receive port.
		 */
		mr = ipc_mqueue_copyin(space, rcv_name,
				       &temp_rcv_mqueue, &temp_rcv_object);
		if (mr != MACH_MSG_SUCCESS) {
			thread_syscall_return(mr);
			/*NOTREACHED*/
		}
		rcv_mqueue = temp_rcv_mqueue;
		rcv_object = temp_rcv_object;
		/* hold ref for rcv_object; rcv_mqueue is locked */

	/*
	    slow_receive:
	*/
		/*
		 *	Now we have sent the request and copied in rcv_name,
		 *	so rcv_mqueue is locked and hold ref for rcv_object.
		 *	Just receive a reply and try to get back to fast path.
		 *
		 *	ipc_mqueue_receive may not return, because if we block
		 *	then our kernel stack may be discarded.  So we save
		 *	state here for mach_msg_continue to pick up.
		 */

		self->ith_msg = msg;
		self->ith_rcv_size = rcv_size;
		self->ith_object = rcv_object;
		self->ith_mqueue = rcv_mqueue;

		mr = ipc_mqueue_receive(rcv_mqueue,
					MACH_MSG_OPTION_NONE,
					MACH_MSG_SIZE_MAX,
					MACH_MSG_TIMEOUT_NONE,
					FALSE, mach_msg_continue,
		       			&temp_kmsg, &temp_seqno);
		/* rcv_mqueue is unlocked */
		ipc_object_release(rcv_object);
		if (mr != MACH_MSG_SUCCESS) {
			thread_syscall_return(mr);
			/*NOTREACHED*/
		}

		(kmsg = temp_kmsg)->ikm_header.msgh_seqno = temp_seqno;
		dest_port = (ipc_port_t) kmsg->ikm_header.msgh_remote_port;
		goto fast_copyout;

	    slow_copyout:
		/*
		 *	Nothing locked and no references held, except
		 *	we have kmsg with msgh_seqno filled in.  Must
		 *	still check against rcv_size and do
		 *	ipc_kmsg_copyout/ipc_kmsg_put.
		 */

		reply_size = kmsg->ikm_header.msgh_size;
		if (rcv_size < reply_size) {
			ipc_kmsg_copyout_dest(kmsg, space);
			(void) ipc_kmsg_put(msg, kmsg, sizeof *msg);
			thread_syscall_return(MACH_RCV_TOO_LARGE);
			/*NOTREACHED*/
		}

		mr = ipc_kmsg_copyout(kmsg, space, current_map(),
				      MACH_PORT_NULL);
		if (mr != MACH_MSG_SUCCESS) {
			if ((mr &~ MACH_MSG_MASK) == MACH_RCV_BODY_ERROR) {
				(void) ipc_kmsg_put(msg, kmsg,
						kmsg->ikm_header.msgh_size);
			} else {
				ipc_kmsg_copyout_dest(kmsg, space);
				(void) ipc_kmsg_put(msg, kmsg, sizeof *msg);
			}

			thread_syscall_return(mr);
			/*NOTREACHED*/
		}

		/* try to get back on optimized path */

		goto fast_put;

	    slow_put:
		mr = ipc_kmsg_put(msg, kmsg, reply_size);
		thread_syscall_return(mr);
		/*NOTREACHED*/
	    }
	} else if (option == MACH_SEND_MSG) {
		ipc_space_t space = current_space();
		vm_map_t map = current_map();
		ipc_kmsg_t kmsg;

		mr = ipc_kmsg_get(msg, send_size, &kmsg);
		if (mr != MACH_MSG_SUCCESS)
			return mr;

		mr = ipc_kmsg_copyin(kmsg, space, map, MACH_PORT_NULL);
		if (mr != MACH_MSG_SUCCESS) {
			ikm_free(kmsg);
			return mr;
		}

		mr = ipc_mqueue_send(kmsg, MACH_MSG_OPTION_NONE,
				     MACH_MSG_TIMEOUT_NONE);
		if (mr != MACH_MSG_SUCCESS) {
			mr |= ipc_kmsg_copyout_pseudo(kmsg, space, map);

			assert(kmsg->ikm_marequest == IMAR_NULL);
			(void) ipc_kmsg_put(msg, kmsg,
					    kmsg->ikm_header.msgh_size);
		}

		return mr;
	} else if (option == MACH_RCV_MSG) {
		ipc_thread_t self = current_thread();
		ipc_space_t space = current_space();
		vm_map_t map = current_map();
		ipc_object_t object;
		ipc_mqueue_t mqueue;
		ipc_kmsg_t kmsg;
		mach_port_seqno_t seqno;

		mr = ipc_mqueue_copyin(space, rcv_name, &mqueue, &object);
		if (mr != MACH_MSG_SUCCESS)
			return mr;
		/* hold ref for object; mqueue is locked */

		/*
		 *	ipc_mqueue_receive may not return, because if we block
		 *	then our kernel stack may be discarded.  So we save
		 *	state here for mach_msg_continue to pick up.
		 */

		self->ith_msg = msg;
		self->ith_rcv_size = rcv_size;
		self->ith_object = object;
		self->ith_mqueue = mqueue;

		mr = ipc_mqueue_receive(mqueue,
					MACH_MSG_OPTION_NONE,
					MACH_MSG_SIZE_MAX,
					MACH_MSG_TIMEOUT_NONE,
					FALSE, mach_msg_continue,
					&kmsg, &seqno);
		/* mqueue is unlocked */
		ipc_object_release(object);
		if (mr != MACH_MSG_SUCCESS)
			return mr;

		kmsg->ikm_header.msgh_seqno = seqno;
		if (rcv_size < kmsg->ikm_header.msgh_size) {
			ipc_kmsg_copyout_dest(kmsg, space);
			(void) ipc_kmsg_put(msg, kmsg, sizeof *msg);
			return MACH_RCV_TOO_LARGE;
		}

		mr = ipc_kmsg_copyout(kmsg, space, map, MACH_PORT_NULL);
		if (mr != MACH_MSG_SUCCESS) {
			if ((mr &~ MACH_MSG_MASK) == MACH_RCV_BODY_ERROR) {
				(void) ipc_kmsg_put(msg, kmsg,
						kmsg->ikm_header.msgh_size);
			} else {
				ipc_kmsg_copyout_dest(kmsg, space);
				(void) ipc_kmsg_put(msg, kmsg, sizeof *msg);
			}

			return mr;
		}

		return ipc_kmsg_put(msg, kmsg, kmsg->ikm_header.msgh_size);
	} else if (option == MACH_MSG_OPTION_NONE) {
		/*
		 *	We can measure the "null mach_msg_trap"
		 *	(syscall entry and thread_syscall_return exit)
		 *	with this path.
		 */

		thread_syscall_return(MACH_MSG_SUCCESS);
		/*NOTREACHED*/
	}

	if (option & MACH_SEND_MSG) {
		mr = mach_msg_send(msg, option, send_size,
				   time_out, notify);
		if (mr != MACH_MSG_SUCCESS)
			return mr;
	}

	if (option & MACH_RCV_MSG) {
		mr = mach_msg_receive(msg, option, rcv_size, rcv_name,
				      time_out, notify);
		if (mr != MACH_MSG_SUCCESS)
			return mr;
	}

	return MACH_MSG_SUCCESS;
}
示例#3
0
void
exception_raise(
	ipc_port_t 	dest_port,
	ipc_port_t 	thread_port,
	ipc_port_t 	task_port,
	integer_t 	_exception, 
	integer_t 	code, 
	integer_t 	subcode)
{
	ipc_thread_t self = current_thread();
	ipc_thread_t receiver;
	ipc_port_t reply_port;
	ipc_mqueue_t dest_mqueue;
	ipc_mqueue_t reply_mqueue;
	ipc_kmsg_t kmsg;
	mach_msg_return_t mr;

	assert(IP_VALID(dest_port));

	/*
	 *	We will eventually need a message buffer.
	 *	Grab the buffer now, while nothing is locked.
	 *	This buffer will get handed to the exception server,
	 *	and it will give the buffer back with its reply.
	 */

	kmsg = ikm_cache();
	if (kmsg != IKM_NULL) {
		ikm_cache() = IKM_NULL;
		ikm_check_initialized(kmsg, IKM_SAVED_KMSG_SIZE);
	} else {
		kmsg = ikm_alloc(IKM_SAVED_MSG_SIZE);
		if (kmsg == IKM_NULL)
			panic("exception_raise");
		ikm_init(kmsg, IKM_SAVED_MSG_SIZE);
	}

	/*
	 *	We need a reply port for the RPC.
	 *	Check first for a cached port.
	 */

	ith_lock(self);
	assert(self->ith_self != IP_NULL);

	reply_port = self->ith_rpc_reply;
	if (reply_port == IP_NULL) {
		ith_unlock(self);
		reply_port = ipc_port_alloc_reply();
		ith_lock(self);
		if ((reply_port == IP_NULL) ||
		    (self->ith_rpc_reply != IP_NULL))
			panic("exception_raise");
		self->ith_rpc_reply = reply_port;
	}

	ip_lock(reply_port);
	assert(ip_active(reply_port));
	ith_unlock(self);

	/*
	 *	Make a naked send-once right for the reply port,
	 *	to hand to the exception server.
	 *	Make an extra reference for the reply port,
	 *	to receive on.  This protects us against
	 *	mach_msg_abort_rpc.
	 */

	reply_port->ip_sorights++;
	ip_reference(reply_port);

	ip_reference(reply_port);
	self->ith_port = reply_port;

	reply_mqueue = &reply_port->ip_messages;
	imq_lock(reply_mqueue);
	assert(ipc_kmsg_queue_empty(&reply_mqueue->imq_messages));
	ip_unlock(reply_port);

	/*
	 *	Make sure we can queue to the destination port.
	 */

	if (!ip_lock_try(dest_port)) {
		imq_unlock(reply_mqueue);
		goto slow_exception_raise;
	}

	if (!ip_active(dest_port) ||
	    (dest_port->ip_receiver == ipc_space_kernel)) {
		imq_unlock(reply_mqueue);
		ip_unlock(dest_port);
		goto slow_exception_raise;
	}

	/*
	 *	Find the destination message queue.
	 */

    {
	ipc_pset_t dest_pset;

	dest_pset = dest_port->ip_pset;
	if (dest_pset == IPS_NULL)
		dest_mqueue = &dest_port->ip_messages;
	else
		dest_mqueue = &dest_pset->ips_messages;
    }

	if (!imq_lock_try(dest_mqueue)) {
		imq_unlock(reply_mqueue);
		ip_unlock(dest_port);
		goto slow_exception_raise;
	}

	/*
	 *	Safe to unlock dest_port, because we hold
	 *	dest_mqueue locked.  We never bother changing
	 *	dest_port->ip_msgcount.
	 */

	ip_unlock(dest_port);

	receiver = ipc_thread_queue_first(&dest_mqueue->imq_threads);
	if ((receiver == ITH_NULL) ||
	    !((receiver->swap_func == (void (*)()) mach_msg_continue) ||
	      ((receiver->swap_func ==
				(void (*)()) mach_msg_receive_continue) &&
	       (sizeof(struct mach_exception) <= receiver->ith_msize) &&
	       ((receiver->ith_option & MACH_RCV_NOTIFY) == 0))) ||
	    !thread_handoff(self, exception_raise_continue, receiver)) {
		imq_unlock(reply_mqueue);
		imq_unlock(dest_mqueue);
		goto slow_exception_raise;
	}
	counter(c_exception_raise_block++);

	assert(current_thread() == receiver);

	/*
	 *	We need to finish preparing self for its
	 *	time asleep in reply_mqueue.  self is left
	 *	holding the extra ref for reply_port.
	 */

	ipc_thread_enqueue_macro(&reply_mqueue->imq_threads, self);
	self->ith_state = MACH_RCV_IN_PROGRESS;
	self->ith_msize = MACH_MSG_SIZE_MAX;
	imq_unlock(reply_mqueue);

	/*
	 *	Finish extracting receiver from dest_mqueue.
	 */

	ipc_thread_rmqueue_first_macro(
		&dest_mqueue->imq_threads, receiver);
	imq_unlock(dest_mqueue);

	/*
	 *	Release the receiver's reference for his object.
	 */
    {
	ipc_object_t object = receiver->ith_object;

	io_lock(object);
	io_release(object);
	io_check_unlock(object);
    }

    {
	struct mach_exception *exc =
			(struct mach_exception *) &kmsg->ikm_header;
	ipc_space_t space = receiver->task->itk_space;

	/*
	 *	We are running as the receiver now.  We hold
	 *	the following resources, which must be consumed:
	 *		kmsg, send-once right for reply_port
	 *		send rights for dest_port, thread_port, task_port
	 *	Synthesize a kmsg for copyout to the receiver.
	 */

	exc->Head.msgh_bits = (MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND_ONCE,
					      MACH_MSG_TYPE_PORT_SEND) |
			       MACH_MSGH_BITS_COMPLEX);
	exc->Head.msgh_size = sizeof *exc;
     /* exc->Head.msgh_remote_port later */
     /* exc->Head.msgh_local_port later */
	exc->Head.msgh_seqno = 0;
	exc->Head.msgh_id = MACH_EXCEPTION_ID;
	exc->threadType = exc_port_proto;
     /* exc->thread later */
	exc->taskType = exc_port_proto;
     /* exc->task later */
	exc->exceptionType = exc_code_proto;
	exc->exception = _exception;
	exc->codeType = exc_code_proto;
	exc->code = code;
	exc->subcodeType = exc_code_proto;
	exc->subcode = subcode;

	/*
	 *	Check that the receiver can handle the message.
	 */

	if (receiver->ith_rcv_size < sizeof(struct mach_exception)) {
		/*
		 *	ipc_kmsg_destroy is a handy way to consume
		 *	the resources we hold, but it requires setup.
		 */

		exc->Head.msgh_bits =
			(MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND,
					MACH_MSG_TYPE_PORT_SEND_ONCE) |
			 MACH_MSGH_BITS_COMPLEX);
		exc->Head.msgh_remote_port = (mach_port_t) dest_port;
		exc->Head.msgh_local_port = (mach_port_t) reply_port;
		exc->thread = (mach_port_t) thread_port;
		exc->task = (mach_port_t) task_port;

		ipc_kmsg_destroy(kmsg);
		thread_syscall_return(MACH_RCV_TOO_LARGE);
		/*NOTREACHED*/
	}

	is_write_lock(space);
	assert(space->is_active);

	/*
	 *	To do an atomic copyout, need simultaneous
	 *	locks on both ports and the space.
	 */

	ip_lock(dest_port);
	if (!ip_active(dest_port) ||
	    !ip_lock_try(reply_port)) {
	    abort_copyout:
		ip_unlock(dest_port);
		is_write_unlock(space);

		/*
		 *	Oh well, we have to do the header the slow way.
		 *	First make it look like it's in-transit.
		 */

		exc->Head.msgh_bits =
			(MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND,
					MACH_MSG_TYPE_PORT_SEND_ONCE) |
			 MACH_MSGH_BITS_COMPLEX);
		exc->Head.msgh_remote_port = (mach_port_t) dest_port;
		exc->Head.msgh_local_port = (mach_port_t) reply_port;

		mr = ipc_kmsg_copyout_header(&exc->Head, space,
					     MACH_PORT_NULL);
		if (mr == MACH_MSG_SUCCESS)
			goto copyout_body;

		/*
		 *	Ack!  Prepare for ipc_kmsg_copyout_dest.
		 *	It will consume thread_port and task_port.
		 */

		exc->thread = (mach_port_t) thread_port;
		exc->task = (mach_port_t) task_port;

		ipc_kmsg_copyout_dest(kmsg, space);
		(void) ipc_kmsg_put(receiver->ith_msg, kmsg,
				    sizeof(mach_msg_header_t));
		thread_syscall_return(mr);
		/*NOTREACHED*/
	}

	if (!ip_active(reply_port)) {
		ip_unlock(reply_port);
		goto abort_copyout;
	}

	assert(reply_port->ip_sorights > 0);
	ip_unlock(reply_port);

    {
	kern_return_t kr;
	ipc_entry_t entry;

	kr = ipc_entry_get (space, &exc->Head.msgh_remote_port, &entry);
	if (kr)
		goto abort_copyout;
    {
	mach_port_gen_t gen;

	assert((entry->ie_bits &~ IE_BITS_GEN_MASK) == 0);
	gen = entry->ie_bits + IE_BITS_GEN_ONE;

	/* optimized ipc_right_copyout */

	entry->ie_bits = gen | (MACH_PORT_TYPE_SEND_ONCE | 1);
    }

	entry->ie_object = (ipc_object_t) reply_port;
	is_write_unlock(space);
    }

	/* optimized ipc_object_copyout_dest */

	assert(dest_port->ip_srights > 0);
	ip_release(dest_port);

	exc->Head.msgh_local_port =
		((dest_port->ip_receiver == space) ?
		 dest_port->ip_receiver_name : MACH_PORT_NULL);

	if ((--dest_port->ip_srights == 0) &&
	    (dest_port->ip_nsrequest != IP_NULL)) {
		ipc_port_t nsrequest;
		mach_port_mscount_t mscount;

		/* a rather rare case */

		nsrequest = dest_port->ip_nsrequest;
		mscount = dest_port->ip_mscount;
		dest_port->ip_nsrequest = IP_NULL;
		ip_unlock(dest_port);

		ipc_notify_no_senders(nsrequest, mscount);
	} else
		ip_unlock(dest_port);

    copyout_body:
	/*
	 *	Optimized version of ipc_kmsg_copyout_body,
	 *	to handle the two ports in the body.
	 */

	mr = (ipc_kmsg_copyout_object(space, (ipc_object_t) thread_port,
				      MACH_MSG_TYPE_PORT_SEND, &exc->thread) |
	      ipc_kmsg_copyout_object(space, (ipc_object_t) task_port,
				      MACH_MSG_TYPE_PORT_SEND, &exc->task));
	if (mr != MACH_MSG_SUCCESS) {
		(void) ipc_kmsg_put(receiver->ith_msg, kmsg,
				    kmsg->ikm_header.msgh_size);
		thread_syscall_return(mr | MACH_RCV_BODY_ERROR);
		/*NOTREACHED*/
	}
    }

	/*
	 *	Optimized version of ipc_kmsg_put.
	 *	We must check ikm_cache after copyoutmsg.
	 */

	ikm_check_initialized(kmsg, kmsg->ikm_size);
	assert(kmsg->ikm_size == IKM_SAVED_KMSG_SIZE);

	if (copyoutmsg(&kmsg->ikm_header, receiver->ith_msg,
		       sizeof(struct mach_exception)) ||
	    (ikm_cache() != IKM_NULL)) {
		mr = ipc_kmsg_put(receiver->ith_msg, kmsg,
				  kmsg->ikm_header.msgh_size);
		thread_syscall_return(mr);
		/*NOTREACHED*/
	}

	ikm_cache() = kmsg;
	thread_syscall_return(MACH_MSG_SUCCESS);
	/*NOTREACHED*/
#ifndef	__GNUC__
	return; /* help for the compiler */
#endif

    slow_exception_raise: {
	struct mach_exception *exc =
			(struct mach_exception *) &kmsg->ikm_header;
	ipc_kmsg_t reply_kmsg;
	mach_port_seqno_t reply_seqno;

	exception_raise_misses++;

	/*
	 *	We hold the following resources, which must be consumed:
	 *		kmsg, send-once right and ref for reply_port
	 *		send rights for dest_port, thread_port, task_port
	 *	Synthesize a kmsg to send.
	 */

	exc->Head.msgh_bits = (MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND,
					      MACH_MSG_TYPE_PORT_SEND_ONCE) |
			       MACH_MSGH_BITS_COMPLEX);
	exc->Head.msgh_size = sizeof *exc;
	exc->Head.msgh_remote_port = (mach_port_t) dest_port;
	exc->Head.msgh_local_port = (mach_port_t) reply_port;
	exc->Head.msgh_seqno = 0;
	exc->Head.msgh_id = MACH_EXCEPTION_ID;
	exc->threadType = exc_port_proto;
	exc->thread = (mach_port_t) thread_port;
	exc->taskType = exc_port_proto;
	exc->task = (mach_port_t) task_port;
	exc->exceptionType = exc_code_proto;
	exc->exception = _exception;
	exc->codeType = exc_code_proto;
	exc->code = code;
	exc->subcodeType = exc_code_proto;
	exc->subcode = subcode;

	ipc_mqueue_send_always(kmsg);

	/*
	 *	We are left with a ref for reply_port,
	 *	which we use to receive the reply message.
	 */

	ip_lock(reply_port);
	if (!ip_active(reply_port)) {
		ip_unlock(reply_port);
		exception_raise_continue_slow(MACH_RCV_PORT_DIED, IKM_NULL, /*dummy*/0);
		/*NOTREACHED*/
	}

	imq_lock(reply_mqueue);
	ip_unlock(reply_port);

	mr = ipc_mqueue_receive(reply_mqueue, MACH_MSG_OPTION_NONE,
				MACH_MSG_SIZE_MAX,
				MACH_MSG_TIMEOUT_NONE,
				FALSE, exception_raise_continue,
				&reply_kmsg, &reply_seqno);
	/* reply_mqueue is unlocked */

	exception_raise_continue_slow(mr, reply_kmsg, reply_seqno);
	/*NOTREACHED*/
    }
}