diff --git a/libc/bionic/semaphore.c b/libc/bionic/semaphore.c
new file mode 100644
index 0000000..fa9de0e
--- /dev/null
+++ b/libc/bionic/semaphore.c
@@ -0,0 +1,155 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include <semaphore.h>
+#include <errno.h>
+#include <sys/time.h>
+#include <sys/atomics.h>
+
+int sem_init(sem_t *sem, int pshared, unsigned int value)
+{
+    if (sem == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    if (pshared != 0) {
+        errno = ENOSYS;
+        return -1;
+    }
+
+    sem->count = value;
+    return 0;
+}
+
+
+int sem_destroy(sem_t *sem)
+{
+    if (sem == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+    if (sem->count == 0) {
+        errno = EBUSY;
+        return -1;
+    }
+    return 0;
+}
+
+
+sem_t *sem_open(const char *name, int oflag, ...)
+{
+    name=name;
+    oflag=oflag;
+
+    errno = ENOSYS;
+    return SEM_FAILED;
+}
+
+
+int sem_close(sem_t *sem)
+{
+    if (sem == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+    errno = ENOSYS;
+    return -1;
+}
+
+
+int sem_unlink(const char * name)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+
+static int
+__atomic_dec_if_positive( volatile unsigned int*  pvalue )
+{
+    unsigned int  old;
+
+    do {
+        old = *pvalue;
+    }
+    while ( old != 0 && __atomic_cmpxchg( (int)old, (int)old-1, (volatile int*)pvalue ) != 0 );
+
+    return old;
+}
+
+int sem_wait(sem_t *sem)
+{
+    if (sem == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    for (;;) {
+        if (__atomic_dec_if_positive(&sem->count))
+            break;
+
+        __futex_wait(&sem->count, 0, 0);
+    }
+    return 0;
+}
+
+int sem_post(sem_t *sem)
+{
+    if (sem == NULL)
+        return EINVAL;
+
+    if (__atomic_inc((volatile int*)&sem->count) == 0)
+        __futex_wake(&sem->count, 1);
+
+    return 0;
+}
+
+int  sem_trywait(sem_t *sem)
+{
+    if (sem == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    if (__atomic_dec_if_positive(&sem->count) > 0) {
+        return 0;
+    } else {
+        return EAGAIN;
+    }
+}
+
+int  sem_getvalue(sem_t *sem, int *sval)
+{
+    if (sem == NULL || sval == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    *sval = sem->count;
+    return 0;
+}