target/riscv: Implement get_gdb_arch()

Change-Id: I5f4ab5243104df41031950682f688f2448a09b17
Signed-off-by: Jesse Sheridan <jesse.sheridan@gmail.com>
Reviewed-on: http://openocd.zylin.com/6322
Tested-by: jenkins
Reviewed-by: Tim Newsome <tim@sifive.com>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/target/riscv/riscv.c

@@ -1614,6 +1614,18 @@ static int riscv_write_memory(struct target *target, target_addr_t address,
 	return tt->write_memory(target, address, size, count, buffer);
 }
 
+const char *riscv_get_gdb_arch(struct target *target)
+{
+	switch (riscv_xlen(target)) {
+		case 32:
+			return "riscv:rv32";
+		case 64:
+			return "riscv:rv64";
+	}
+	LOG_ERROR("Unsupported xlen: %d", riscv_xlen(target));
+	return NULL;
+}
+
 static int riscv_get_gdb_reg_list_internal(struct target *target,
 		struct reg **reg_list[], int *reg_list_size,
 		enum target_register_class reg_class, bool read)
@@ -2848,6 +2860,7 @@ struct target_type riscv_target = {
 	.mmu = riscv_mmu,
 	.virt2phys = riscv_virt2phys,
 
+	.get_gdb_arch = riscv_get_gdb_arch,
 	.get_gdb_reg_list = riscv_get_gdb_reg_list,
 	.get_gdb_reg_list_noread = riscv_get_gdb_reg_list_noread,