Index: lib/libthr/arch/powerpc/Makefile.inc
===================================================================
--- /dev/null
+++ lib/libthr/arch/powerpc/Makefile.inc
@@ -0,0 +1,3 @@
+# $FreeBSD$
+
+SRCS+=  _umtx_op_err.S
Index: lib/libthr/arch/powerpc/include/pthread_md.h
===================================================================
--- lib/libthr/arch/powerpc/include/pthread_md.h
+++ lib/libthr/arch/powerpc/include/pthread_md.h
@@ -91,4 +91,6 @@
 	return (NULL);
 }
 
+#define	HAS__UMTX_OP_ERR	1
+
 #endif /* _PTHREAD_MD_H_ */
Index: lib/libthr/arch/powerpc/powerpc/_umtx_op_err.S
===================================================================
--- /dev/null
+++ lib/libthr/arch/powerpc/powerpc/_umtx_op_err.S
@@ -0,0 +1,45 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2019 Brandon Bergren <git@bdragon.rtk0.net>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include <machine/asm.h>
+#include <sys/syscall.h>
+
+	.text
+	.align 2
+ENTRY(_umtx_op_err)
+	li	%r0, SYS__umtx_op
+	sc
+	/* If summary overflow is set, r3 already contains the error. */
+	bsolr
+	/* Ignore any spurious syscall aux return values. */
+	li	%r3, 0
+	blr
+END(_umtx_op_err)
+
+	.section .note.GNU-stack,"",%progbits