diff --git a/libm/src/s_logbf.c b/libm/src/s_logbf.c
new file mode 100644
index 0000000..c54928c
--- /dev/null
+++ b/libm/src/s_logbf.c
@@ -0,0 +1,41 @@
+/* s_logbf.c -- float version of s_logb.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#ifndef lint
+static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_logbf.c,v 1.8 2005/12/03 11:57:19 bde Exp $";
+#endif
+
+#include "math.h"
+#include "math_private.h"
+
+static const float
+two25 = 3.355443200e+07;		/* 0x4c000000 */
+
+float
+logbf(float x)
+{
+	int32_t ix;
+	GET_FLOAT_WORD(ix,x);
+	ix &= 0x7fffffff;			/* high |x| */
+	if(ix==0) return (float)-1.0/fabsf(x);
+	if(ix>=0x7f800000) return x*x;
+	if(ix<0x00800000) {
+		x *= two25;		 /* convert subnormal x to normal */
+		GET_FLOAT_WORD(ix,x);
+		ix &= 0x7fffffff;
+		return (float) ((ix>>23)-127-25);
+	} else
+		return (float) ((ix>>23)-127);
+}