linux-kernel-module-cheat/build-modules

#!/usr/bin/env python3

import distutils.dir_util
import os
import platform
import shlex
import shutil

import common
from shell_helpers import LF
import path_properties

class Main(common.BuildCliFunction):
    def __init__(self):
        super().__init__(
            description='''\
Build our Linux kernel modules without using Buildroot.

See also: https://cirosantilli.com/linux-kernel-module-cheat#host
''')
        self.add_argument(
            '--make-args',
            default='',
            help='''
Pass custom options to make.
''',
        )
        self.add_argument(
            '--host',
            default=False,
            help='''\
Build the Linux kernel modules against the host kernel.
Place the modules on a separate magic directory from non --host builds.
''',
        )
        self._add_argument('--force-rebuild')
        self.add_argument(
            'kernel-modules',
            default=[],
            help='''\
Which kernel modules to build. Default: build all.
Can be either the path to the C file, or its basename without extension.''',
            nargs='*',
        )

    def build(self):
        build_dir = self.get_build_dir()
        os.makedirs(build_dir, exist_ok=True)
        # I kid you not, out-of-tree build is not possible, O= does not work as for the kernel build:
        #
        # * https://stackoverflow.com/questions/5718899/building-an-out-of-tree-linux-kernel-module-in-a-separate-object-directory
        # * https://stackoverflow.com/questions/12244979/build-kernel-module-into-a-specific-directory
        # * https://stackoverflow.com/questions/18386182/out-of-tree-kernel-modules-multiple-module-single-makefile-same-source-file
        #
        # This copies only modified files as per:
        # https://stackoverflow.com/questions/5718899/building-an-out-of-tree-linux-kernel-module-in-a-separate-object-directory
        distutils.dir_util.copy_tree(
            self.env['kernel_modules_source_dir'],
            os.path.join(build_dir, self.env['kernel_modules_subdir']),
            update=1,
        )
        distutils.dir_util.copy_tree(
            self.env['include_source_dir'],
            os.path.join(build_dir, self.env['include_subdir']),
            update=1,
        )
        all_kernel_modules = []
        for basename in os.listdir(self.env['kernel_modules_source_dir']):
            abspath = os.path.join(self.env['kernel_modules_source_dir'], basename)
            if os.path.isfile(abspath):
                noext, ext = os.path.splitext(basename)
                if ext == self.env['c_ext']:
                    relpath = abspath[len(self.env['root_dir']) + 1:]
                    my_path_properties = path_properties.get(relpath)
                    if my_path_properties.should_be_built(self.env):
                        all_kernel_modules.append(noext)
        if self.env['kernel_modules'] == []:
            kernel_modules = all_kernel_modules
        else:
            kernel_modules = map(lambda x: os.path.splitext(os.path.split(x)[1])[0], self.env['kernel_modules'])
        object_files = map(lambda x: x + self.env['obj_ext'], kernel_modules)
        if self.env['host']:
            build_subdir = self.env['kernel_modules_build_host_subdir']
        else:
            build_subdir = self.env['kernel_modules_build_subdir']
        ccache = shutil.which('ccache')
        if ccache is not None:
            cc = '{} {}'.format(ccache, self.env['gcc_path'])
        else:
            cc = self.env['gcc_path']
        if self.env['host']:
            linux_dir = os.path.join('/lib', 'modules', platform.uname().release, 'build')
        else:
            linux_dir = self.env['linux_build_dir']
        ccflags = [
            '-I', self.env['root_dir'], LF,
        ]
        make_args_extra = []
        if self.env['verbose']:
            make_args_extra.extend(['V=1', LF])
        if self.env['force_rebuild']:
            make_args_extra.extend(['-B', LF])
        self.sh.run_cmd(
            (
                [
                    'make', LF,
                    '-j', str(self.env['nproc']), LF,
                    'ARCH={}'.format(self.env['linux_arch']), LF,
                    'CC={}'.format(cc), LF,
                    'CCFLAGS={}'.format(self.sh.cmd_to_string(ccflags)), LF,
                    'CROSS_COMPILE={}'.format(self.env['toolchain_prefix_dash']), LF,
                    'LINUX_DIR={}'.format(linux_dir), LF,
                    'M={}'.format(build_subdir), LF,
                    'OBJECT_FILES={}'.format(' '.join(object_files)), LF,
                ] +
                make_args_extra +
                self.sh.shlex_split(self.env['make_args'])
            ),
            cwd=os.path.join(self.env['kernel_modules_build_subdir']),
        )
        if not self.env['host']:
            self.sh.copy_dir_if_update_non_recursive(
                srcdir=self.env['kernel_modules_build_subdir'],
                destdir=self.env['out_rootfs_overlay_lkmc_dir'],
                filter_ext=self.env['kernel_module_ext'],
            )

    def get_build_dir(self):
        if self.env['host']:
            return self.env['kernel_modules_build_host_dir']
        else:
            return self.env['kernel_modules_build_dir']

if __name__ == '__main__':
    Main().cli()