Index: sys/arch/aarch64/conf/files.aarch64
===================================================================
RCS file: /cvsroot/src/sys/arch/aarch64/conf/files.aarch64,v
retrieving revision 1.22
diff -u -p -r1.22 files.aarch64
--- sys/arch/aarch64/conf/files.aarch64	18 Apr 2020 11:00:37 -0000	1.22
+++ sys/arch/aarch64/conf/files.aarch64	15 Jun 2020 16:24:51 -0000
@@ -99,6 +99,7 @@ file	arch/aarch64/aarch64/exec_machdep.c
 file	arch/aarch64/aarch64/fusu.S
 file	arch/aarch64/aarch64/idle_machdep.S
 file	arch/aarch64/aarch64/kobj_machdep.c		modular
+file	arch/aarch64/aarch64/lock_stubs.S
 file	arch/aarch64/aarch64/process_machdep.c
 file	arch/aarch64/aarch64/procfs_machdep.c		procfs
 file	arch/aarch64/aarch64/sig_machdep.c
Index: sys/arch/aarch64/include/mutex.h
===================================================================
RCS file: /cvsroot/src/sys/arch/aarch64/include/mutex.h,v
retrieving revision 1.1
diff -u -p -r1.1 mutex.h
--- sys/arch/aarch64/include/mutex.h	10 Aug 2014 05:47:38 -0000	1.1
+++ sys/arch/aarch64/include/mutex.h	15 Jun 2020 16:24:51 -0000
@@ -1,3 +1,5 @@
 /* $NetBSD: mutex.h,v 1.1 2014/08/10 05:47:38 matt Exp $ */
 
 #include <arm/mutex.h>
+
+#define __HAVE_MUTEX_STUBS		1
Index: sys/arch/evbarm/include/mutex.h
===================================================================
RCS file: /cvsroot/src/sys/arch/evbarm/include/mutex.h,v
retrieving revision 1.2
diff -u -p -r1.2 mutex.h
--- sys/arch/evbarm/include/mutex.h	9 Feb 2007 21:55:03 -0000	1.2
+++ sys/arch/evbarm/include/mutex.h	15 Jun 2020 16:24:51 -0000
@@ -1,3 +1,7 @@
 /*	$NetBSD: mutex.h,v 1.2 2007/02/09 21:55:03 ad Exp $	*/
 
+#ifdef __aarch64__
+#include <aarch64/mutex.h>
+#else
 #include <arm/mutex.h>
+#endif
--- /dev/null	2020-06-15 16:23:46.221621297 +0000
+++ sys/arch/aarch64/aarch64/lock_stubs.S	2020-06-15 16:19:04.458161352 +0000
@@ -0,0 +1,81 @@
+/*	$NetBSD$	*/
+
+/*-
+ * Copyright (c) 2014, 2020 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Matt Thomas of 3am Software Foundry, and by Andrew Doran.
+ *
+ * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
+ */
+
+#include "opt_lockdebug.h"
+
+#include <aarch64/asm.h>
+
+#include "assym.h"
+
+RCSID("$NetBSD$")
+
+#ifndef LOCKDEBUG
+/*
+ * mutex_enter(): the compare-and-set must be atomic with respect to
+ * interrupts and with respect to other CPUs.
+ */
+ENTRY(mutex_enter)
+	mrs	x1, tpidr_el1		/* x1 = curlwp */
+1:
+	ldxr	x2, [x0]		/* load old value */
+	cbnz	x2, 3f			/*   equals zero? */
+	stxr	w3, x1, [x0]		/* store curlwp as new value */
+	cbnz	w3, 2f			/*   succeed? nope, try again. */
+	dmb	sy			/* membar_enter() */
+	ret
+2:
+	b	1b
+3:	
+	b	_C_LABEL(mutex_vector_enter)
+END(mutex_enter)
+
+/*
+ * mutex_exit(): the compare-and-set need only be atomic with respect
+ * to interrupts.  the cheapest way to achieve that may be to use a
+ * restartable sequence, but the code do that would be quite involved,
+ * so just use ldxr+stxr to achieve the same.
+ */
+ENTRY(mutex_exit)
+	dmb	sy			/* membar_exit() */
+	mrs	x1, tpidr_el1		/* x1 = curlwp */
+1:
+	ldxr	x2, [x0]		/* load old value */
+	cmp	x1, x2			/*   equals curlwp? */
+	b.ne	3f			/*     slow path if different */
+	stxr	w3, xzr, [x0]		/* store zero as new value */
+	cbnz	w3, 2f			/*   succeed? nope, try again. */
+	ret
+2:
+	b	1b
+3:	
+	b	_C_LABEL(mutex_vector_exit)
+END(mutex_exit)
+#endif	/* !LOCKDEBUG */