Files to enable build of out-of-tree kernel modules

Question

I need to prepare an apt-package for stuff to enable building kernel modules for a custom Linux. I have cross-built on a different machine the kernel headers and modules using headers_install and modules_install make-targets. After copying the generated directories I'm still not able to build kernel modules on the target machine since /lib/modules/$(shell uname -r)/build is missing.

Here is my question. What are the minimal dependencies I need to include to my package in order to enable module builds (alongside with the generated kernel headers and modules mentioned above)?

Thanks in advance.

Answer 1

After some experimenting I've got to a working solution:

#!/bin/bash

ARCH=arm

SRC_DIR=$1
MOD_DIR=$2

BUILD_DIR=$MOD_DIR/build

set -ex

cd $SRC_DIR
make modules_install INSTALL_HDR_PATH=$MOD_DIR
rm $MOD_DIR/{build,source}

mkdir $BUILD_DIR
cp $SRC_DIR/{.config,Makefile,System.map,Module.symvers} $BUILD_DIR

mkdir -p $BUILD_DIR/arch/$ARCH
cp $SRC_DIR/arch/$ARCH/Makefile $BUILD_DIR/arch/$ARCH/

cp -r $SRC_DIR/scripts $BUILD_DIR/

# Build a headers tree manually, because
# `make headers_install` doesn't put everything needed.
cp -r $SRC_DIR/include $BUILD_DIR/
cp -r $SRC_DIR/arch/$ARCH/include/* $BUILD_DIR/include/
cp -r $SRC_DIR/include/generated/* $BUILD_DIR/include/
cp -r $SRC_DIR/arch/$ARCH/include/generated/* $BUILD_DIR/include/
cp $SRC_DIR/include/linux/kconfig.h $BUILD_DIR/include/linux/

This script is fed with a path to a kernel source tree after the latter was built natively (not cross-platform).