PWD := $(shell pwd)MOD_DIR ?= /lib/modules/`uname -r`/buildobj-m += hello.o modules:    make -C $(MOD_DIR) M=$(PWD) modulesmodules_install:    make -C $(MOD_DIR) M=$(PWD) modules_installclean:    rm -rf *.o *.ko *.cmd *.mod.* Module.symvers modules.order.PHONY: modules modules_install clean