Fix external callback logging in profiler.

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index 0e30a9468890cbca262bb992a4e5fddf2bba0fa2..702860737f44f59b9cb109ffe39bb30b5012a23a 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -217,6 +217,20 @@ F FUNCTION_CAST(Address addr) {
 }
 
 
+// Determine whether the architecture uses function descriptors
+// which provide a level of indirection between the function pointer
+// and the function entrypoint.
+#if V8_HOST_ARCH_PPC && \
+    (V8_OS_AIX || (V8_TARGET_ARCH_PPC64 && V8_TARGET_BIG_ENDIAN))
+#define USES_FUNCTION_DESCRIPTORS 1
+#define FUNCTION_ENTRYPOINT_ADDRESS(f)       \
+  (reinterpret_cast<v8::internal::Address*>( \
+      &(reinterpret_cast<intptr_t*>(f)[0])))
+#else
+#define USES_FUNCTION_DESCRIPTORS 0
+#endif
+
+
 // -----------------------------------------------------------------------------
 // Forward declarations for frequently used classes
 // (sorted alphabetically)