diff --git a/lib/msun/Makefile b/lib/msun/Makefile
index 2775010a8d62..14e3d062728e 100644
--- a/lib/msun/Makefile
+++ b/lib/msun/Makefile
@@ -55,7 +55,7 @@ COMMON_SRCS= b_exp.c b_log.c b_tgamma.c \
 	s_rint.c s_rintf.c s_round.c s_roundf.c s_roundl.c \
 	s_scalbln.c s_scalbn.c s_scalbnf.c s_signbit.c \
 	s_signgam.c s_significand.c s_significandf.c s_sin.c s_sinf.c s_tan.c \
-	s_tanf.c s_tanh.c s_tanhf.c s_trunc.c s_truncf.c \
+	s_tanf.c s_tanh.c s_tanhf.c s_trunc.c s_truncf.c s_truncl.c \
 	w_cabs.c w_cabsf.c w_drem.c w_dremf.c
 
 # Location of fpmath.h and _fpmath.h
@@ -153,6 +153,6 @@ MLINKS+=sinh.3 sinhf.3
 MLINKS+=sqrt.3 cbrt.3 sqrt.3 cbrtf.3 sqrt.3 sqrtf.3
 MLINKS+=tan.3 tanf.3
 MLINKS+=tanh.3 tanhf.3
-MLINKS+=trunc.3 truncf.3
+MLINKS+=trunc.3 truncf.3 truncl.3
 
 .include <bsd.lib.mk>
diff --git a/lib/msun/man/trunc.3 b/lib/msun/man/trunc.3
index f7672d21a249..c510095c5c96 100644
--- a/lib/msun/man/trunc.3
+++ b/lib/msun/man/trunc.3
@@ -1,4 +1,4 @@
-.\" Copyright (c) 2004 David Schultz <das@FreeBSD.org>
+.\" Copyright (c) 2004, 2005 David Schultz <das@FreeBSD.org>
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
@@ -24,12 +24,13 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 20, 2004
+.Dd April 16, 2005
 .Dt TRUNC 3
 .Os
 .Sh NAME
 .Nm trunc ,
-.Nm truncf
+.Nm truncf ,
+.Nm truncl
 .Nd nearest integral value with magnitude less than or equal to |x|
 .Sh LIBRARY
 .Lb libm
@@ -39,18 +40,22 @@
 .Fn trunc "double x"
 .Ft float
 .Fn truncf "float x"
+.Ft long double
+.Fn truncl "long double x"
 .Sh DESCRIPTION
 The
-.Fn trunc
+.Fn trunc ,
+.Fn truncf ,
 and
-.Fn truncf
+.Fn truncl
 functions return the nearest integral value with magnitude less than
 or equal to
 .Pf | Fa x Ns | .
 They are equivalent to
-.Fn rint
-and
+.Fn rint ,
 .Fn rintf ,
+and
+.Fn rintl ,
 respectively, in the
 .Dv FE_TOWARDZERO
 rounding mode.
@@ -64,9 +69,10 @@ rounding mode.
 .Xr round 3
 .Sh STANDARDS
 The
-.Fn trunc
+.Fn trunc ,
+.Fn truncf ,
 and
-.Fn truncf
+.Fn truncl
 functions conform to
 .St -isoC-99 .
 .Sh HISTORY
diff --git a/lib/msun/src/math.h b/lib/msun/src/math.h
index 5ac6e562f579..ba918a36ede6 100644
--- a/lib/msun/src/math.h
+++ b/lib/msun/src/math.h
@@ -464,8 +464,8 @@ long double	sqrtl(long double);
 long double	tanhl(long double);
 long double	tanl(long double);
 long double	tgammal(long double);
-long double	truncl(long double);
 #endif
+long double	truncl(long double);
 
 #endif /* __ISO_C_VISIBLE >= 1999 */
 __END_DECLS
diff --git a/lib/msun/src/s_truncl.c b/lib/msun/src/s_truncl.c
new file mode 100644
index 000000000000..d535e9cac92e
--- /dev/null
+++ b/lib/msun/src/s_truncl.c
@@ -0,0 +1,62 @@
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ *
+ * From: @(#)s_floor.c 5.1 93/09/24
+ */
+
+#ifndef lint
+static char rcsid[] = "$FreeBSD$";
+#endif
+
+/*
+ * truncl(x)
+ * Return x rounded toward 0 to integral value
+ * Method:
+ *	Bit twiddling.
+ * Exception:
+ *	Inexact flag raised if x not equal to truncl(x).
+ */
+
+#include <float.h>
+#include <math.h>
+#include <stdint.h>
+
+#include "fpmath.h"
+
+#ifdef LDBL_IMPLICIT_NBIT
+#define	MANH_SIZE	(LDBL_MANH_SIZE + 1)
+#else
+#define	MANH_SIZE	LDBL_MANH_SIZE
+#endif
+
+long double
+truncl(long double x)
+{
+	union IEEEl2bits u = { .e = x };
+	int e = u.bits.exp - LDBL_MAX_EXP + 1;
+
+	if (e < MANH_SIZE - 1) {
+		if (e < 0) {			/* raise inexact if x != 0 */
+			u.e = 0.0;
+		} else {
+			uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
+			if (((u.bits.manh & m) | u.bits.manl) == 0)
+				return (x);	/* x is integral */
+			u.bits.manh &= ~m;
+			u.bits.manl = 0;
+		}
+	} else if (e < LDBL_MANT_DIG - 1) {
+		uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
+		if ((u.bits.manl & m) == 0)
+			return (x);	/* x is integral */
+		u.bits.manl &= ~m;
+	}
+	return (u.e);
+}