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

[Arnd Bergmann]

On Wed, May 15, 2019 at 9:39 AM Masahiro Yamada
<yamada.masahiro@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxx>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>

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