diff --git a/libc/platform/bionic/page.h b/libc/platform/bionic/page.h
new file mode 100644
index 0000000..d063a98
--- /dev/null
+++ b/libc/platform/bionic/page.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#pragma once
+
+// Get PAGE_SIZE and PAGE_MASK.
+#include <sys/user.h>
+
+// Returns the address of the page containing address 'x'.
+#define PAGE_START(x) ((x) & PAGE_MASK)
+
+// Returns the offset of address 'x' in its page.
+#define PAGE_OFFSET(x) ((x) & ~PAGE_MASK)
+
+// Returns the address of the next page after address 'x', unless 'x' is
+// itself at the start of a page.
+#define PAGE_END(x) PAGE_START((x) + (PAGE_SIZE-1))