diff --git a/sys/sys/libkern.h b/sys/sys/libkern.h
--- a/sys/sys/libkern.h
+++ b/sys/sys/libkern.h
@@ -226,6 +226,22 @@
 	return (strrchr(p, ch));
 }
 
+static __inline int64_t
+signed_extend64(uint64_t bitmap, int lsb, int width)
+{
+
+	return ((int64_t)(bitmap << (63 - lsb - (width - 1)))) >>
+	    (63 - (width - 1));
+}
+
+static __inline int32_t
+signed_extend32(uint32_t bitmap, int lsb, int width)
+{
+
+	return ((int32_t)(bitmap << (31 - lsb - (width - 1)))) >>
+	    (31 - (width - 1));
+}
+
 /* fnmatch() return values. */
 #define	FNM_NOMATCH	1	/* Match failed. */