[PATCH v3 4/4] kbuild: compile-test kernel headers to ensure they are self-contained

Masahiro Yamada yamada.masahiro at socionext.com
Sun Jun 30 00:57:23 PDT 2019

Hi Sam,

On Sat, Jun 29, 2019 at 3:01 AM Sam Ravnborg <sam at ravnborg.org> wrote:
> Hi Masahiro.
> On Fri, Jun 28, 2019 at 01:39:02AM +0900, Masahiro Yamada wrote:
> > The headers in include/ are globally used in the kernel source tree
> > to provide common APIs. They are included from external modules, too.
> >
> > It will be useful to make as many headers self-contained as possible
> > so that we do not have to rely on a specific include order.
> >
> > There are more than 4000 headers in include/. In my rough analysis,
> > 70% of them are already self-contained. With efforts, most of them
> > can be self-contained.
> >
> > For now, we must exclude more than 1000 headers just because they
> > cannot be compiled as standalone units. I added them to header-test-.
> > The black list was mostly generated by a script, so should be checked
> > later.
> The list is smaller than I had expected.
> And I see why you insisted on avoiding a maze ok Kbuild files.
> It looks good, except there is a few issues..
> The file kernel/kheaders_data.tar.xz includes all the .s files.
> Something needs to be done to exclude the .s files...

Good catch. I will change scripts/gen_kheaders.sh

> When building a full kernel the build fails like this:
>   LD      vmlinux.o
> aarch64-linux-gnu-ld: cannot find include/lib.a: No such file or directory
> make[1]: *** [/home/sam/kernel/linux-kbuild.git/Makefile:1054: vmlinux] Error 1
> make[1]: Leaving directory '/home/sam/kernel/linux-kbuild.git/.build/arm64-allyesconfig'
> make: *** [Makefile:179: sub-make] Error 2

My bad - I built only include/,
without testing full build.

I will fix.

> include/uapi/linux/mman.h fails when building sparc64 allmodconfig.
> There is likely more header files that will fail when we start to
> throw this after diverse randconfigs.
> I have no good idea how to catch this.
> Unless your scripts could automate this across several architectures.

Thanks. I excluded a little more headers.

> I did not continue my testing futher.
> > +header-test-                 += uapi/drm/vmwgfx_drm.h
> > +header-test-                 += uapi/linux/a.out.h
> > +header-test-                 += uapi/linux/coda.h
> ...
> > +header-test-                 += uapi/xen/evtchn.h
> > +header-test-                 += uapi/xen/gntdev.h
> > +header-test-                 += uapi/xen/privcmd.h
> I though uapi files were covered by another Makefile?
> If they are added because we pull them in using a pattern, maybe they
> should be removed using a specific filer-out?

I have not looked at this closely yet.

usr/include/Makefile tests UAPI headers
crafted by scripts/headers_install.sh

Testing UAPI headers in their raw form
makes sense, I think.

Best Regards
Masahiro Yamada

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