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

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Date:   Wed, 15 May 2019 11:31:36 -0700
From:   Kees Cook <keescook@...omium.org>
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>, 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

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@...ionext.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