diff --git a/libc/include/sys/cdefs_elf.h b/libc/include/sys/cdefs_elf.h
index 1e57470..0887fa5 100644
--- a/libc/include/sys/cdefs_elf.h
+++ b/libc/include/sys/cdefs_elf.h
@@ -96,9 +96,24 @@
 #endif
 
 /* GCC visibility helper macro */
+/* This must be used to tag non-static functions that are private, i.e.
+ * never exposed by the shared library. */
 #define __LIBC_HIDDEN__							\
 	__attribute__ ((visibility ("hidden")))
 
+/* This must be used to tag non-static functions that are public, i.e.
+ * exposed by the shared library, and part of the stable NDK ABI */
+#define __LIBC_ABI_PUBLIC__ \
+        __attribute__ ((visibility ("default")))
+
+/* This must be used to tag non-static functions that must be exported
+ * by the shared library, but whose implementation is private to the
+ * platform. For now this is equivalent to __LIBC_ABI_PUBLIC__, but we
+ * may want to change this later.
+ */
+#define __LIBC_ABI_PRIVATE__ \
+        __attribute__ ((visibility ("default")))
+
 #define	__IDSTRING(_n,_s)		__SECTIONSTRING(.ident,_s)
 
 #define	__RCSID(_s)			__IDSTRING(rcsid,_s)