Index: head/sys/cddl/dev/fbt/fbt.h
===================================================================
--- head/sys/cddl/dev/fbt/fbt.h
+++ head/sys/cddl/dev/fbt/fbt.h
@@ -58,6 +58,7 @@
 void	fbt_patch_tracepoint(fbt_probe_t *, fbt_patchval_t);
 int	fbt_provide_module_function(struct linker_file *, int,
 	    struct linker_symval *, void *);
+int	fbt_excluded(const char *name);
 
 extern dtrace_provider_id_t	fbt_id;
 extern fbt_probe_t		**fbt_probetab;
Index: head/sys/cddl/dev/fbt/fbt.c
===================================================================
--- head/sys/cddl/dev/fbt/fbt.c
+++ head/sys/cddl/dev/fbt/fbt.c
@@ -111,6 +111,37 @@
 static int			fbt_probetab_size;
 static int			fbt_verbose = 0;
 
+int
+fbt_excluded(const char *name)
+{
+
+	if (strncmp(name, "dtrace_", 7) == 0 &&
+	    strncmp(name, "dtrace_safe_", 12) != 0) {
+		/*
+		 * Anything beginning with "dtrace_" may be called
+		 * from probe context unless it explicitly indicates
+		 * that it won't be called from probe context by
+		 * using the prefix "dtrace_safe_".
+		 */
+		return (1);
+	}
+
+	/* Exclude some internal functions */
+	if (name[0] == '_' && name[1] == '_')
+		return (1);
+
+	/*
+	 * When DTrace is built into the kernel we need to exclude
+	 * the FBT functions from instrumentation.
+	 */
+#ifndef _KLD_MODULE
+	if (strncmp(name, "fbt_", 4) == 0)
+		return (1);
+#endif
+
+	return (0);
+}
+
 static void
 fbt_doubletrap(void)
 {