Provide stack(9) MD stubs for RISC-V so ktr(9) can be compiled in.

sys/conf/files.riscv

@@ -34,9 +34,10 @@ riscv/riscv/machdep.c		standard
 riscv/riscv/mem.c		standard
 riscv/riscv/nexus.c		standard
 riscv/riscv/pmap.c		standard
-riscv/riscv/sys_machdep.c	standard
+riscv/riscv/stack_machdep.c	standard
 riscv/riscv/support.S		standard
 riscv/riscv/swtch.S		standard
+riscv/riscv/sys_machdep.c	standard
 riscv/riscv/trap.c		standard
 riscv/riscv/timer.c		standard
 riscv/riscv/uio_machdep.c	standard

sys/riscv/riscv/stack_machdep.c

@@ -0,0 +1,63 @@
+/*-
+ * Copyright (c) 2016 Ruslan Bukin <br@bsdpad.com>
+ * All rights reserved.
+ *
+ * Portions of this software were developed by SRI International and the
+ * University of Cambridge Computer Laboratory under DARPA/AFRL contract
+ * FA8750-10-C-0237 ("CTSRD"), as part of the DARPA CRASH research programme.
+ *
+ * Portions of this software were developed by the University of Cambridge
+ * Computer Laboratory as part of the CTSRD Project, with support from the
+ * UK Higher Education Innovation Fund (HEIF).
+ *
+ * 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 <sys/systm.h>
+#include <sys/proc.h>
+#include <sys/stack.h>
+
+#include <machine/vmparam.h>
+#include <machine/pcb.h>
+
+void
+stack_save_td(struct stack *st, struct thread *td)
+{
+
+}
+
+int
+stack_save_td_running(struct stack *st, struct thread *td)
+{
+
+	return (EOPNOTSUPP);
+}
+
+void
+stack_save(struct stack *st)
+{
+
+}