Index: head/sys/arm64/arm64/db_trace.c
===================================================================
--- head/sys/arm64/arm64/db_trace.c
+++ head/sys/arm64/arm64/db_trace.c
@@ -38,12 +38,7 @@
 
 #include <machine/armreg.h>
 #include <machine/debug_monitor.h>
-
-struct unwind_state {
-	uint64_t fp;
-	uint64_t sp;
-	uint64_t pc;
-};
+#include <machine/stack.h>
 
 void
 db_md_list_watchpoints()
@@ -67,22 +62,6 @@
 	    HW_BREAKPOINT_RW));
 }
 
-static int
-db_unwind_frame(struct unwind_state *frame)
-{
-	uint64_t fp = frame->fp;
-
-	if (fp == 0)
-		return -1;
-
-	frame->sp = fp + 0x10;
-	/* FP to previous frame (X29) */
-	frame->fp = *(uint64_t *)(fp);
-	/* LR (X30) */
-	frame->pc = *(uint64_t *)(fp + 8) - 4;
-	return (0);
-}
-
 static void
 db_stack_trace_cmd(struct unwind_state *frame)
 {
@@ -95,7 +74,7 @@
 		uint64_t pc = frame->pc;
 		int ret;
 
-		ret = db_unwind_frame(frame);
+		ret = unwind_frame(frame);
 		if (ret < 0)
 			break;
 
Index: head/sys/arm64/arm64/unwind.c
===================================================================
--- head/sys/arm64/arm64/unwind.c
+++ head/sys/arm64/arm64/unwind.c
@@ -0,0 +1,52 @@
+/*-
+ * Copyright (c) 2015 The FreeBSD Foundation
+ * All rights reserved.
+ *
+ * This software was developed by Semihalf under
+ * the sponsorship of the FreeBSD Foundation.
+ *
+ * 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.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+#include <sys/param.h>
+
+#include <machine/stack.h>
+
+int
+unwind_frame(struct unwind_state *frame)
+{
+	uint64_t fp;
+
+	fp = frame->fp;
+	if (fp == 0)
+		return (-1);
+
+	frame->sp = fp + 0x10;
+	/* FP to previous frame (X29) */
+	frame->fp = *(uint64_t *)(fp);
+	/* LR (X30) */
+	frame->pc = *(uint64_t *)(fp + 8) - 4;
+
+	return (0);
+}
Index: head/sys/arm64/include/stack.h
===================================================================
--- head/sys/arm64/include/stack.h
+++ head/sys/arm64/include/stack.h
@@ -32,4 +32,12 @@
 #define	INKERNEL(va) \
 	((va) >= VM_MIN_KERNEL_ADDRESS && (va) <= VM_MAX_KERNEL_ADDRESS)
 
+struct unwind_state {
+	uint64_t fp;
+	uint64_t sp;
+	uint64_t pc;
+};
+
+int unwind_frame(struct unwind_state *);
+
 #endif /* !_MACHINE_STACK_H_ */
Index: head/sys/conf/files.arm64
===================================================================
--- head/sys/conf/files.arm64
+++ head/sys/conf/files.arm64
@@ -2,6 +2,7 @@
 arm/arm/devmap.c		standard
 arm/arm/generic_timer.c		standard
 arm/arm/pmu.c			standard
+arm64/arm64/unwind.c		optional	ddb | kdtrace_hooks
 arm64/arm64/autoconf.c		standard
 arm64/arm64/bcopy.c		standard
 arm64/arm64/bus_machdep.c	standard