linux-kernel - Re: [RFC PATCH] kbuild: check uniqueness of basename of modules

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Message-ID: <CAK8P3a1y7hxME0me_Zu-F8a8jU6n=T+c32mv83utOtsL-+gc0A@mail.gmail.com>
Date:   Wed, 15 May 2019 10:08:12 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jessica Yu <jeyu@...nel.org>,
        Lucas De Marchi <lucas.de.marchi@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Rusty Russell <rusty@...tcorp.com.au>,
        Kees Cook <keescook@...omium.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] kbuild: check uniqueness of basename of modules

On Wed, May 15, 2019 at 9:39 AM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>
> In the recent build test of linux-next, Stephen saw a build error
> caused by a broken .tmp_versions/*.mod file:
>
>   https://lkml.org/lkml/2019/5/13/991
>
> drivers/net/phy/asix.ko and drivers/net/usb/asix.ko have the same
> basename, and there is a race in generating .tmp_versions/asix.mod
>
> Kbuild has not checked this before, and it occasionally shows up with
> obscure error message when this kind of race occurs.
>
> It is not trivial to catch this potential issue by eyes.
>
> Hence, this script.
>
> I compile-tested allmodconfig for the latest kernel as of writing,
> it detected the following:
>
> warning: same basename '88pm800.ko' if the following are built as modules:
>   drivers/regulator/88pm800.ko
>   drivers/mfd/88pm800.ko
> warning: same basename 'adv7511.ko' if the following are built as modules:
>   drivers/gpu/drm/bridge/adv7511/adv7511.ko
>   drivers/media/i2c/adv7511.ko
> warning: same basename 'asix.ko' if the following are built as modules:
>   drivers/net/phy/asix.ko
>   drivers/net/usb/asix.ko
> warning: same basename 'coda.ko' if the following are built as modules:
>   fs/coda/coda.ko
>   drivers/media/platform/coda/coda.ko
> warning: same basename 'realtek.ko' if the following are built as modules:
>   drivers/net/phy/realtek.ko
>   drivers/net/dsa/realtek.ko
>
> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>

That looks great!

> ---
>
>  [Alternative fix ? ]
>
> I do not know about the user experience of modprobe etc.
> when two different modules have the same name.
> It does not matter if this is correctly handled by modules.order?
>
> If this is just a problem of the build system, it is pretty easy to fix.
> For example, if we prepend the directory path, parallel build will
> never write to the same file simultanously.
>
>   asix.mod -> drivers/net/phy/asix.mod
>   asix.mod -> drivers/net/usb/asix.mod

non-unique module names cause all kinds of problems, and
modprobe can certainly not handle them correctly, and there
are issues with symbols exported from a module when another
one has the same name.

     Arnd