get_ret_stack
ret_stack = get_ret_stack(current, offset, &next_offset);
ret_stack = get_ret_stack(current, current->curr_ret_stack, offset);
ret_stack = get_ret_stack(task, offset, &offset);
ret_stack = get_ret_stack(task, offset, &offset);
ret_stack = get_ret_stack(task, i, &i);