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

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Date:   Thu, 16 May 2019 02:55:02 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sam Ravnborg <sam@...nborg.org>, Arnd Bergmann <arnd@...db.de>,
        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>,
        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

Hi Kees,

On Thu, May 16, 2019 at 1:20 AM Kees Cook <keescook@...omium.org> wrote:
>
> On Wed, May 15, 2019 at 04:53:15PM +0900, Masahiro Yamada wrote:
> > On Wed, May 15, 2019 at 4:40 PM 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>
> > > ---
> > >
> >
> > > diff --git a/scripts/modules-check.sh b/scripts/modules-check.sh
> > > new file mode 100755
> > > index 000000000000..944e68bd22b0
> > > --- /dev/null
> > > +++ b/scripts/modules-check.sh
> > > @@ -0,0 +1,18 @@
> > > +#!/bin/sh
> > > +# SPDX-License-Identifier: GPL-2.0
> > > +
> > > +# Warn if two or more modules have the same basename
> > > +check_same_name_modules()
> > > +{
> > > +       same_name_modules=$(cat modules.order modules.builtin | \
> > > +                               xargs basename -a | sort | uniq -d)
>
> While probably it'll never be a problem, just for robustness, I'd add "--"
> to the end basename to terminate argument interpretation:
>
>     xargs basename -a -- | sort | ...


Sorry for my ignorance, but could you
teach me the effect of "--" ?


I sometimes use "--" as a separator
when there is ambiguity in arguments
for example, "git log <revision> -- <path>"


In this case, what is intended by "--"?



--
Best Regards
Masahiro Yamada