riscv64: add architectural defines

arch/riscv64/defs.h

@@ -0,0 +1,36 @@
+#ifndef __ARCH_RISCV64_DEFS_H
+#define __ARCH_RISCV64_DEFS_H
+
+#define REG_SZ		(8)
+#define MCONTEXT_GREGS	(176)
+
+/* program counter is saved in x0 as well as x1, similar to mips */
+#define REG_PC_SAVE	(0)
+#define REG_PC		(1)
+#define REG_SP		(2)
+#define REG_S0		(8)
+#define REG_S1		(9)
+#define REG_A0		(10)
+#define REG_A1		(11)
+#define REG_A2		(12)
+#define REG_A3		(13)
+#define REG_A4		(14)
+#define REG_A5		(15)
+#define REG_A6		(16)
+#define REG_A7		(17)
+#define REG_S2		(18)
+#define REG_S3		(19)
+#define REG_S4		(20)
+#define REG_S5		(21)
+#define REG_S6		(22)
+#define REG_S7		(23)
+#define REG_S8		(24)
+#define REG_S9		(25)
+#define REG_S10		(26)
+#define REG_S11		(27)
+
+#define PC_OFFSET	REG_OFFSET(REG_PC_SAVE)
+
+#include "common-defs.h"
+
+#endif