linux-kernel - Re: [PATCH] kbuild: do not check name uniqueness of builtin modules

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Message-ID: <CAK8P3a2nth2sNPT46_e8G=s=D-J8LtsrA4kO2esu804_pWVs-Q@mail.gmail.com>
Date:   Mon, 20 May 2019 11:28:20 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jessica Yu <jeyu@...nel.org>,
        Lucas De Marchi <lucas.de.marchi@...il.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Michael Schmitz <schmitzmic@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Rusty Russell <rusty@...tcorp.com.au>,
        Kees Cook <keescook@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Lucas De Marchi <lucas.demarchi@...el.com>
Subject: Re: [PATCH] kbuild: do not check name uniqueness of builtin modules

On Mon, May 20, 2019 at 4:57 AM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>
> I just thought it was a good idea to scan builtin.modules in the name
> uniqueness checking, but Stephen reported a false positive.
>
> ppc64_defconfig produces:
>
>   warning: same basename if the following are built as modules:
>     arch/powerpc/platforms/powermac/nvram.ko
>     drivers/char/nvram.ko
>
> ..., which is a false positive because the former is never built as
> a module as you see in arch/powerpc/platforms/powermac/Makefile:
>
>   # CONFIG_NVRAM is an arch. independent tristate symbol, for pmac32 we really
>   # need this to be a bool.  Cheat here and pretend CONFIG_NVRAM=m is really
>   # CONFIG_NVRAM=y
>   obj-$(CONFIG_NVRAM:m=y)         += nvram.o
>
> Since we cannot predict how tricky Makefiles are written in wild,
> builtin.modules may potentially contain false positives. I do not
> think it is a big deal as far as kmod is concerned, but false positive
> warnings in the kernel build makes people upset. It is better to not
> do it.
>
> Even without checking builtin.modules, we have enough (and more solid)
> test coverage with allmodconfig.
>
> While I touched this part, I replaced the sed code with neater one
> provided by Stephen.
>
> Link: https://lkml.org/lkml/2019/5/19/120
> Link: https://lkml.org/lkml/2019/5/19/123
> Fixes: 3a48a91901c5 ("kbuild: check uniqueness of module names")
> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>

Looks good to me

Acked-by: Arnd Bergmann <arnd@...db.de>

> ---
>
>  scripts/modules-check.sh | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/scripts/modules-check.sh b/scripts/modules-check.sh
> index 2f659530e1ec..39e8cb36ba19 100755
> --- a/scripts/modules-check.sh
> +++ b/scripts/modules-check.sh
> @@ -6,10 +6,10 @@ set -e
>  # Check uniqueness of module names
>  check_same_name_modules()
>  {
> -       for m in $(sed 's:.*/::' modules.order modules.builtin | sort | uniq -d)
> +       for m in $(sed 's:.*/::' modules.order | sort | uniq -d)
>         do
> -               echo "warning: same basename if the following are built as modules:" >&2
> -               sed "/\/$m/!d;s:^kernel/:  :" modules.order modules.builtin >&2
> +               echo "warning: same module names found:" >&2
> +               sed -n "/\/$m/s:^kernel/:  :p" modules.order >&2
>         done
>  }
>
> --
> 2.17.1
>