Re: Kbuilds and Makefiles in building the kernel

Nagy =C3=81brah=C3=A1m Zsombor <[email protected]> =E6=96=BC 2025=E5=B9=
=B411=E6=9C=8828=E6=97=A5=E9=80=B1=E4=BA=94 =E4=B8=8B=E5=8D=884:18=E5=AF=AB=
=E9=81=93=EF=BC=9A
>
> On Fri, 2025-11-28 at 08:12 +0800, Nick Huang wrote:
> > Nagy =C3=81brah=C3=A1m Zsombor <[email protected]> =E6=96=BC 2025=E5=
=B9=B411=E6=9C=8828=E6=97=A5 =E9=80=B1=E4=BA=94 =E4=B8=8A=E5=8D=881:37=E5=
=AF=AB=E9=81=93=EF=BC=9A
> > >
> > > On Thu, 2025-11-27 at 19:26 +0800, Nick Huang wrote:
> > > > Abraham Zsombor Nagy <[email protected]> =E6=96=BC 2025=E5=B9=B41=
1=E6=9C=8827=E6=97=A5=E9=80=B1=E5=9B=9B
> > > > =E4=B8=8B=E5=8D=886:43=E5=AF=AB=E9=81=93=EF=BC=9A
> > > > >
> > > > > Hello,
> > > > >
> > > > > https://docs.kernel.org/kbuild/makefiles.html#the-kbuild-files
> > > > > stat
> > > > > es
> > > > > that when a directory contains a Kbuild file, the Makefile is
> > > > > skipped in
> > > > > that directory.
> > > > >
> > > > > It feels to me that both files are in use e.g. under arch/x86/
> > > > > directory.
> > > > >
> > > > > I'm trying to see what files are the core of the kernel and
> > > > > what
> > > > > files
> > > > > can be configured for x86 by partially parsing the Makefiles
> > > > > and
> > > > > the
> > > > > Kbuild files. Would it be sufficient to parse them as:
> > > > >
> > > > > if file =3D=3D "Makefile" or file =3D=3D "Kbuild":
> > > > >
> > > > >  > parse(file)
> > > > >
> > > > > or it should prefer the Kbuild file when present, or it is
> > > > > using
> > > > > some
> > > > > other logic?
> > > > >
> > > > > Sincerely,
> > > > >
> > > > > Abraham Nagy
> > > > >
> > > > >
> > > >
> > > > Hi  Abraham Zsombor Nagy
> > > > What functionality are you trying to add that would require
> > > > modifying
> > > > the Makefile or Kbuild?
> > > >
> > > > Sincerely,
> > > > Nick Huang
> > >
> > > Hi Nick,
> > >
> > > I'm not modifying the build files, only writing a script that walks
> > > through the source tree and parses Makefiles and Kbuild files to
> > > list
> > > what source files are linked to the kernel by default and by
> > > CONFIG_*
> > > options. This is to see what to read through to get a basic
> > > understanding of the kernel at a given config.
> > >
> > > As I understand the documentation linked above, I should skip
> > > Makefiles
> > > when Kbuild files are present in a directory, but Makefiles feels
> > > to
> > > have important lines too.
> > >
> > > The approach is something like to extract object files and
> > > subdirectories from lines that start with python regex "^\S+-y" or
> > > "^\S+-\$\(CONFIG.*\)".
> > >
> > > Sincerely,
> > > Abraham
> > >
> > >
> >
> > Hi Abraham
> > You can use git grep -n "CONFIG_**" to find the files you need.
> >
> > Sincerely,
> > Nick
>
> Hello Nick,
>
> Thank you, I've just tried git grep, it seems convenient, however I
> still need to further script and fine-tune the output, in which case I
> think having a customizable walk algorithm is the way to start with.
>
> find/git & grep walks through the directory tree that could include
> build files and sources that are from an incompatible set of config
> options. Also, there are some Makefiles that end the line with a
> backslash '\' saying to process the next line too, but which won't have
> regex match.
>
> A custom algorithm can start from a Makefile (and Kbuild file?)_and
> walk directories only that are visible from there. This way I can
> enforce a horizon of config options that are meaningfully able to
> extend the kernel. E.g. starting with minimal config, seeing the
> available additional configs, then in subsequent calls adding configs
> one by one until I have a whole kernel (but without extra parts).
>
> Make menuconfig combined with git grep and a text editor could help,
> but it would require more manual handling to achieve the same.
>
> Sincerely,
> Abraham

Hi Abraham

Are you trying to find out which configs can be enabled? If so, I
suggest you check the description of each Kconfig to see if it=E2=80=99s wh=
at
you need, or if you have a clear idea of the functionality you want to
implement.

Is your main goal to build a Linux kernel?

Sincerely,
Nick