Re: [PATCH] kbuild: cancel sub_make_done for the install target to fix DKMS

[John S Gruber <johnsgruber@gmail.com>]

On Wed, Jul 28, 2021 at 8:13 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> Since commit bcf637f54f6d ("kbuild: parse C= and M= before changing the
> working directory"), external modules invoked by DKMS fail to build
> because M= option is not parsed.
>
> I wanted to add 'unset sub_make_done' in install.sh but similar scripts,
> arch/*/boot/install.sh, are duplicated, so I set sub_make_done empty
> in the top Makefile.
>
> Fixes: bcf637f54f6d ("kbuild: parse C= and M= before changing the working directory")
> Reported-by: John S Gruber <johnsgruber@gmail.com>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
>  Makefile | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index bb10a93edf5c..4193092f7c38 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1316,6 +1316,16 @@ PHONY += scripts_unifdef
>  scripts_unifdef: scripts_basic
>         $(Q)$(MAKE) $(build)=scripts scripts/unifdef
>
> +# ---------------------------------------------------------------------------
> +# Install
> +
> +# Many distros have the custom install script, /sbin/kernelinstall.
> +# If DKMS is installed, 'make install' will eventually recuses back
> +# to the this Makefile to build and install external modules.
> +# Cancel sub_make_done so that options such as M=, V=, etc. are parsed.
> +
> +install: sub_make_done=
> +
>  # ---------------------------------------------------------------------------
>  # Tools
>
> --
> 2.27.0
>

This patch tested successfully on my system on 5.14.0-rc3.