linux-kernel - Re: [PATCH] kbuild: check arch/$(SRCARCH)/include/generated before out-of-tree build

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Message-ID: <CAMuHMdUH46_yvYc840uvMoOOqXuU3mDOjaT65vZ=6WKGq7-Kqg@mail.gmail.com>
Date:   Tue, 9 Jul 2019 10:30:53 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-kbuild <linux-kbuild@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kbuild: check arch/$(SRCARCH)/include/generated before
 out-of-tree build

Hi Yamada-san,

On Sun, Apr 7, 2019 at 12:45 PM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
> After cross-compiling the kernel, "make mrproper" should be executed
> with the proper ARCH= option. Otherwise, stale objects will remain
> under arch/$(SRCARCH)/.
>
> One bad scenario is like this:
>
>   $ make ARCH=arm defconfig all   # cross-compile the kernel for arm
>   $ make mrproper                 # mrproper for host-arch (i.e. x86)
>   $ make ARCH=arm O=build_dir defconfig all
>
> If you miss ARCH= for mrproper and cross-compile the kernel with O=
> and ARCH= options, Kbuild will happily start to build, but may fail
> due to stale objects in the srctree.
>
> If $(srctree)/arch/$(SRCARCH)/include/generated/ exists, let's stop
> the out-of-tree build. To detect this, mrproper should clean only
> arch/$(SRCARCH)/include/generated/.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
>
>  Makefile | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 10643c3..17945ce 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1091,7 +1091,9 @@ PHONY += prepare archprepare prepare1 prepare3
>  prepare3: include/config/kernel.release
>  ifneq ($(srctree),.)
>         @$(kecho) '  Using $(srctree) as source for kernel'
> -       $(Q)if [ -f $(srctree)/.config -o -d $(srctree)/include/config ]; then \
> +       $(Q)if [ -f $(srctree)/.config -o \
> +                -d $(srctree)/include/config -o \
> +                -d $(srctree)/arch/$(SRCARCH)/include/generated ]; then \
>                 echo >&2 "  $(srctree) is not clean, please run 'make mrproper'"; \
>                 echo >&2 "  in the '$(srctree)' directory.";\

This took me a bit to find out what was wrong...

Usually I don't run "make mrproper", as it removes files I may want to
keep (e.g. tags).  Hence I ran "git ls-files -o | grep m68k | xargs rm"
(I usually build in separate output directories), confirmed with "git
ls-files -o" there were no remaining build artefacts, and was surprised
to discover I still got the error message above?!?

Apparently arch/m68k/include/generated was still present, but as "git
ls-files -o" only shows files, not directories, it was not listed.
Perhaps the directory checks above can be changed to directory exists
_and_ is not empty?

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds