[kernel] Add endpoint object and related syscalls

The endpoint object adds synchronous IPC. Also added the wait-type of
'object' to threads.

src/kernel/objects/endpoint.cpp

@@ -0,0 +1,97 @@
+#include "objects/endpoint.h"
+#include "objects/thread.h"
+#include "page_manager.h"
+#include "scheduler.h"
+
+endpoint::endpoint() :
+	kobject(kobject::type::endpoint)
+{}
+
+endpoint::~endpoint()
+{
+	if (!check_signal(j6_signal_endpoint_closed))
+		close();
+}
+
+void
+endpoint::close()
+{
+	assert_signal(j6_signal_endpoint_closed);
+	for (auto &data : m_blocked)
+		data.th->wake_on_result(this, j6_status_closed);
+}
+
+j6_status_t
+endpoint::send(size_t len, void *data)
+{
+	scheduler &s = scheduler::get();
+	TCB *tcb = s.current();
+	thread_data sender = { thread::from_tcb(tcb), data };
+	sender.len = len;
+
+	if (!check_signal(j6_signal_endpoint_can_send)) {
+		assert_signal(j6_signal_endpoint_can_recv);
+		sender.th->wait_on_object(this);
+		m_blocked.append(sender);
+		s.schedule();
+
+		// we woke up having already finished the send
+		// because it happened in the receiver
+		return sender.th->get_wait_result();
+	}
+
+	thread_data receiver = m_blocked.pop_front();
+	if (m_blocked.count() == 0)
+		deassert_signal(j6_signal_endpoint_can_send);
+
+	j6_status_t status = do_message_copy(sender, receiver);
+
+	receiver.th->wake_on_result(this, status);
+	return status;
+}
+
+j6_status_t
+endpoint::receive(size_t *len, void *data)
+{
+	scheduler &s = scheduler::get();
+	TCB *tcb = s.current();
+	thread_data receiver = { thread::from_tcb(tcb), data };
+	receiver.len_p = len;
+
+	if (!check_signal(j6_signal_endpoint_can_recv)) {
+		assert_signal(j6_signal_endpoint_can_send);
+		receiver.th->wait_on_object(this);
+		m_blocked.append(receiver);
+		s.schedule();
+
+		// we woke up having already finished the recv
+		// because it happened in the sender
+		return receiver.th->get_wait_result();
+	}
+
+	thread_data sender = m_blocked.pop_front();
+	if (m_blocked.count() == 0)
+		deassert_signal(j6_signal_endpoint_can_recv);
+
+	// TODO: don't pop sender on some errors
+	j6_status_t status = do_message_copy(sender, receiver);
+	sender.th->wake_on_result(this, status);
+	return status;
+}
+
+j6_status_t
+endpoint::do_message_copy(const endpoint::thread_data &sender, endpoint::thread_data &receiver)
+{
+	if (sender.len > *receiver.len_p)
+		return j6_err_insufficient;
+
+	page_manager *pm = page_manager::get();
+	void *send_data = pm->get_offset_from_mapped(sender.data, sender.th->tcb()->pml4);
+	void *recv_data = pm->get_offset_from_mapped(receiver.data, receiver.th->tcb()->pml4);
+	kutil::memcpy(recv_data, send_data, sender.len);
+	*receiver.len_p = sender.len;
+
+	// TODO: this will not work if non-contiguous pages are mapped!!
+
+	return j6_status_ok;
+}