diff --git a/usr.bin/Makefile b/usr.bin/Makefile
index 4f8a36b9cfe2..03f88646e677 100644
--- a/usr.bin/Makefile
+++ b/usr.bin/Makefile
@@ -266,10 +266,8 @@ SUBDIR+=	iscsictl
 
 .if ${MK_KDUMP} != "no"
 SUBDIR+=        kdump
-.if ${MACHINE_ARCH} != "aarch64" # ARM64TODO truss does not build
 SUBDIR+=        truss
 .endif
-.endif
 
 .if ${MK_KERBEROS_SUPPORT} != "no"
 SUBDIR+=	compile_et
diff --git a/usr.bin/truss/aarch64-fbsd.c b/usr.bin/truss/aarch64-fbsd.c
new file mode 100644
index 000000000000..85819f672d76
--- /dev/null
+++ b/usr.bin/truss/aarch64-fbsd.c
@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 2015 The FreeBSD Foundation
+ *
+ * Portions of this software were developed by Konstantin Belousov
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/* FreeBSD/arm64-specific system call handling. */
+
+#include <sys/ptrace.h>
+#include <sys/syscall.h>
+
+#include <machine/reg.h>
+#include <machine/armreg.h>
+#include <machine/ucontext.h>
+
+#include <stdio.h>
+
+#include "truss.h"
+
+extern const char *syscallnames[]; /* silence compiler */
+#include "syscalls.h"
+
+static int
+aarch64_fetch_args(struct trussinfo *trussinfo, u_int narg)
+{
+	struct reg regs;
+	struct current_syscall *cs;
+	lwpid_t tid;
+	u_int i, reg, syscall_num;
+
+	tid = trussinfo->curthread->tid;
+	cs = &trussinfo->curthread->cs;
+	if (ptrace(PT_GETREGS, tid, (caddr_t)&regs, 0) < 0) {
+		fprintf(trussinfo->outfile, "-- CANNOT READ REGISTERS --\n");
+		return (-1);
+	}
+
+	/*
+	 * FreeBSD has two special kinds of system call redirections --
+	 * SYS_syscall, and SYS___syscall.  The former is the old syscall()
+	 * routine, basically; the latter is for quad-aligned arguments.
+	 *
+	 * The system call argument count and code from ptrace() already
+	 * account for these, but we need to skip over the first argument.
+	 */
+	syscall_num = regs.x[8];
+	if (syscall_num == SYS_syscall || syscall_num == SYS___syscall) {
+		reg = 1;
+		syscall_num = regs.x[0];
+	} else {
+		reg = 0;
+	}
+
+	for (i = 0; i < narg && reg < 8; i++, reg++)
+		cs->args[i] = regs.x[reg];
+	return (0);
+}
+
+static int
+aarch64_fetch_retval(struct trussinfo *trussinfo, long *retval, int *errorp)
+{
+	struct reg regs;
+	lwpid_t tid;
+
+	tid = trussinfo->curthread->tid;
+	if (ptrace(PT_GETREGS, tid, (caddr_t)&regs, 0) < 0) {
+		fprintf(trussinfo->outfile, "-- CANNOT READ REGISTERS --\n");
+		return (-1);
+	}
+
+	retval[0] = regs.x[0];
+	retval[1] = regs.x[1];
+	*errorp = !!(regs.spsr & PSR_C);
+	return (0);
+}
+
+static struct procabi aarch64_fbsd = {
+	"FreeBSD ELF64",
+	syscallnames,
+	nitems(syscallnames),
+	aarch64_fetch_args,
+	aarch64_fetch_retval
+};
+
+PROCABI(aarch64_fbsd);