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

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Message-ID: <20190520094020.GC15326@kroah.com>
Date:   Mon, 20 May 2019 11:40:20 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-kbuild@...r.kernel.org, Sam Ravnborg <sam@...nborg.org>,
        Arnd Bergmann <arnd@...db.de>, 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@...r.kernel.org, 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 11:54:37AM +0900, Masahiro Yamada 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>
> ---

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>