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Date: Wed, 15 May 2019 11:31:36 -0700
From: Kees Cook <keescook@chromium.org>
Subject: Re: [RFC PATCH] kbuild: check uniqueness of basename of modules
Message-ID: <201905151130.87CDB73C0@keescook>
References: <20190515073818.22486-1-yamada.masahiro@socionext.com>
 <CAK7LNATUvPMqt93iwzNud0mxk99Si=CEBDyjA8BLEXM_tcTBfQ@mail.gmail.com>
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To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Sam Ravnborg <sam@ravnborg.org>, Arnd Bergmann <arnd@arndb.de>, Greg KH <gregkh@linuxfoundation.org>, Jessica Yu <jeyu@kernel.org>, Lucas De Marchi <lucas.de.marchi@gmail.com>, Linus Torvalds <torvalds@linux-foundation.org>, Rusty Russell <rusty@rustcorp.com.au>, Michal Marek <michal.lkml@markovi.net>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

On Thu, May 16, 2019 at 03:07:54AM +0900, Masahiro Yamada wrote:
> On Wed, May 15, 2019 at 4:40 PM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
> 
> >         $(Q)$(AWK) '!x[$$0]++' $^ > $(objtree)/modules.builtin
> > diff --git a/scripts/modules-check.sh b/scripts/modules-check.sh
> > new file mode 100755
> > index 000000000000..944e68bd22b0
> > --- /dev/null
> > +++ b/scripts/modules-check.sh
> > @@ -0,0 +1,18 @@
> > +#!/bin/sh
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +# Warn if two or more modules have the same basename
> > +check_same_name_modules()
> > +{
> > +       same_name_modules=$(cat modules.order modules.builtin | \
> > +                               xargs basename -a | sort | uniq -d)
> 
> 
> I noticed a bug here.
> 
> 
> allnoconfig + CONFIG_MODULES=y
> will create empty modules.order and modules.builtin.
> 
> Then, 'basename -a' will emit the error messages
> since it receives zero arguments.

You can skip running it by adding "-r" to xargs:

       -r, --no-run-if-empty
              If the standard input does not contain any nonblanks, do not run
              the command.  Normally, the command is run once even if there is
              no input.  This option is a GNU extension.



-- 
Kees Cook