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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Wed, 5 May 2021 06:05:42 +0900
Message-ID: <CAK7LNAROdVMPQq4Qn_M=OWzJrfqNOc4fyMicNKdnCqu7G9rFgw@mail.gmail.com>
Subject: Re: [PATCH 2/2] kconfig: unify cc-option and as-option
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        Andrew Morton <akpm@linux-foundation.org>,
        Brendan Higgins <brendanhiggins@google.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Changbin Du <changbin.du@intel.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Will Deacon <will@kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, May 5, 2021 at 5:52 AM Johannes Berg <johannes@sipsolutions.net> wrote:
>
> On Wed, 2021-05-05 at 05:46 +0900, Masahiro Yamada wrote:
> >
> >  - This commit touches scripts/Kconfig.include.
> >  - External module builds (M= builds) never invoke Kconfig
> >
> > Putting these two together, your claim is really odd.
>
> Hmm.
>
> > If external module builds invoke Kconfig,
> > your kernel is already broken.
>
> Well, it's not about the kernel, that's just the normal upstream (or
> perhaps distribution) kernel.
>
> Anyway, you're right, it's much simpler. The problem isn't invoking M=
> or something like that, that happens much later and sent me on the
> completely wrong track.
>
> The problem is simply doing
>
>         make kernelversion
>
> to determine the version of a tree that's not writable to the user, e.g.
>
>         make -C /lib/modules/$(uname -r)/build/ kernelversion
>
> Which basically also means that it's harmless, since the version is of
> course not affected by cc-option.

It was fixed.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=805b2e1d427aab4bb27fa7c51ebb9db7547551b1


If you want to make it work without that commit,

   make -C /lib/modules/$(uname -r)/build/ kernelversion M=/tmp

will work.

Pass a writable directory to M=.
M= build never touches the kernel source tree.


> johannes
>


-- 
Best Regards
Masahiro Yamada