How to compile Linux kernel module without kernel Makefile?

1
votes

I have an ARM Linux device, but I don't have the Makefile of the kernel to build a kernel module.

I have GCC cross compiler to this arch.

How can I compile a kernel module without the Makefile of the kernel?

1
linuxgcclinux-kernelcross-compilingkernel-module

1 Answers

1
votes

How can I compile kernel module without have the Makefile of the kernel?

You can't. You need the kernel Makefile in order to compile a module, along with a pre-built kernel source tree. On most distributions, you can obtain the kernel source for building modules through packages like linux-headers-xxx where xxx should be the output of uname -r.

For example, on Debian or Ubuntu:

sudo apt-get install linux-headers-$(uanme -r)

You will then find the files needed for building modules at /lib/modules/$(uname -r)/build, and you can build a module with a Makefile like this:

KDIR  := /lib/modules/$(shell uname -r)/build
PWD   := $(shell pwd)
obj-m := mymodule.o     # same name as the .c file of your module

default:
    $(MAKE) -C $(KDIR) M=$(PWD) modules

What this does is basically invoking the kernel Makefile telling it to build the module in the current directory.

Also, I am not sure why you say that you are on an ARM Linux device, and you have a cross compiler. If you are on the device itself, you shouldn't need a cross compiler at all. If you are on a different device, then you'll need to use the appropriate uname -r for the target device in order to get the right sources and in order to build. You might need to do this by hand since the output of uname -r isn't always helpful.

You'll also need to secify the architecture and cross compilation toolchain prefix in the module Makefile, for example:

default:
    $(MAKE) -C $(KDIR) M=$(PWD) ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- modules