diff --git a/src/bsp/lk/kernel/semaphore.c b/src/bsp/lk/kernel/semaphore.c
new file mode 100644
index 0000000..219360a
--- /dev/null
+++ b/src/bsp/lk/kernel/semaphore.c
@@ -0,0 +1,101 @@
+/* semaphore.c
+ *
+ * Copyright 2012 Christopher Anderson <chris@nullcode.org>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <debug.h>
+#include <err.h>
+#include <kernel/semaphore.h>
+#include <kernel/thread.h>
+
+void sem_init(semaphore_t *sem, unsigned int value)
+{
+	*sem = (semaphore_t)SEMAPHORE_INITIAL_VALUE(*sem, value);
+}
+
+void sem_destroy(semaphore_t *sem)
+{
+	THREAD_LOCK(state);
+	sem->count = 0;
+	wait_queue_destroy(&sem->wait, true);
+	THREAD_UNLOCK(state);
+}
+
+int sem_post(semaphore_t *sem, bool resched)
+{
+	int ret = 0;
+
+	THREAD_LOCK(state);
+
+	/*
+	 * If the count is or was negative then a thread is waiting for a resource, otherwise
+	 * it's safe to just increase the count available with no downsides
+	 */
+	if (unlikely(++sem->count <= 0))
+		ret = wait_queue_wake_one(&sem->wait, resched, NO_ERROR);
+
+	THREAD_UNLOCK(state);
+
+	return ret;
+}
+
+status_t sem_wait(semaphore_t *sem)
+{
+	status_t ret = NO_ERROR;
+	THREAD_LOCK(state);
+
+	/*
+	 * If there are no resources available then we need to
+	 * sit in the wait queue until sem_post adds some.
+	 */
+	if (unlikely(--sem->count < 0))
+		ret = wait_queue_block(&sem->wait, INFINITE_TIME);
+
+	THREAD_UNLOCK(state);
+	return ret;
+}
+
+status_t sem_trywait(semaphore_t *sem)
+{
+	status_t ret = NO_ERROR;
+	THREAD_LOCK(state);
+
+	if (unlikely(sem->count <= 0))
+		ret = ERR_NOT_READY;
+	else
+		sem->count--;
+
+	THREAD_UNLOCK(state);
+	return ret;
+}
+
+status_t sem_timedwait(semaphore_t *sem, lk_time_t timeout)
+{
+	status_t ret = NO_ERROR;
+	THREAD_LOCK(state);
+
+	if (unlikely(--sem->count < 0)) {
+		ret = wait_queue_block(&sem->wait, timeout);
+		if (ret < NO_ERROR) {
+			if (ret == ERR_TIMED_OUT) {
+				sem->count++;
+			}
+		}
+	}
+
+	THREAD_UNLOCK(state);
+	return ret;
+}
+
+/* vim: set noexpandtab: */