Index: b/usr/src/lib/libc/port/sys/flock.c
===================================================================
--- /dev/null
+++ b/usr/src/lib/libc/port/sys/flock.c
@@ -0,0 +1,82 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+/*	Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T	*/
+/*	  All Rights Reserved  	*/
+
+/*
+ * Portions of this source code were derived from Berkeley 4.3 BSD
+ * under license from the Regents of the University of California.
+ */
+
+/*LINTLIBRARY*/
+
+#include <sys/types.h>
+#include <sys/file.h>
+#include <sys/fcntl.h>
+#include <errno.h>
+
+int
+flock(int fd, int operation)
+{
+	struct flock	fl;
+	int	cmd;
+	int	ret;
+
+	/* initialize the flock struct to set lock on entire file */
+	fl.l_whence = 0;
+	fl.l_start = 0;
+	fl.l_len = 0;
+	fl.l_type = 0;
+
+	/* In non-blocking lock, use F_SETLK for cmd, F_SETLKW otherwise */
+	if (operation & LOCK_NB) {
+		cmd = F_SETLK;
+		operation &= ~LOCK_NB;	/* turn off this bit */
+	} else
+		cmd = F_SETLKW;
+
+	switch (operation) {
+	case LOCK_UN:
+		fl.l_type |= F_UNLCK;
+		break;
+	case LOCK_SH:
+		fl.l_type |= F_RDLCK;
+		break;
+	case LOCK_EX:
+		fl.l_type |= F_WRLCK;
+		break;
+	default:
+		errno = EINVAL;
+		return (-1);
+	}
+
+	ret = fcntl(fd, cmd, &fl);
+
+	if (ret == -1 && errno == EACCES)
+		errno = EWOULDBLOCK;
+
+	return (ret);
+}
Index: b/usr/src/lib/libc/amd64/Makefile
===================================================================
--- a/usr/src/lib/libc/amd64/Makefile
+++ b/usr/src/lib/libc/amd64/Makefile
@@ -193,6 +193,7 @@ COMSYSOBJS=			\
 	fchdir.o		\
 	fchroot.o		\
 	fdsync.o		\
+	flock.o		\
 	fpathconf.o		\
 	fstatfs.o		\
 	fstatvfs.o		\
Index: b/usr/src/lib/libc/i386/Makefile.com
===================================================================
--- a/usr/src/lib/libc/i386/Makefile.com
+++ b/usr/src/lib/libc/i386/Makefile.com
@@ -217,6 +217,7 @@ COMSYSOBJS=			\
 	fchdir.o		\
 	fchroot.o		\
 	fdsync.o		\
+	flock.o		\
 	fpathconf.o		\
 	fstatfs.o		\
 	fstatvfs.o		\
Index: b/usr/src/lib/libc/port/mapfile-vers
===================================================================
--- a/usr/src/lib/libc/port/mapfile-vers
+++ b/usr/src/lib/libc/port/mapfile-vers
@@ -274,6 +274,7 @@ SYMBOL_VERSION DYSON_1 {
         error_message_count;
         error_one_per_line;
         error_print_progname;
+        flock;
         mempcpy;
         program_invocation_name;
         program_invocation_short_name;