From: Masahiro Yamada <masahiroy@kernel.org>
To: Matthias Maennich <maennich@google.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Cc: Android Kernel" <kernel-team@android.com>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
Subject: Re: [PATCH] kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set
Date: Thu, 17 Jun 2021 10:43:19 +0900 [thread overview]
Message-ID: <CAK7LNAR=Fwzio6CQqDOYQJj9tYrf5a_-sYQ+Yr2=Qt5cYq8wOA@mail.gmail.com> (raw)
In-Reply-To: <CAK7LNAQkoqTG540EOER27G83z+DO5fkeHi-in-vRYkrbX-o0cg@mail.gmail.com>
On Thu, Jun 17, 2021 at 10:05 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Sat, Jun 12, 2021 at 11:18 PM Matthias Maennich <maennich@google.com> wrote:
> >
> > To avoid unnecessary recompilations, mkcompile_h does not regenerate
> > compile.h if just the timestamp changed.
> > Though, if KBUILD_BUILD_TIMESTAMP is set, an explicit timestamp for the
> > build was requested, in which case we should not ignore it.
> >
> > If a user follows the documentation for reproducible builds [1] and
> > defines KBUILD_BUILD_TIMESTAMP as the git commit timestamp, a clean
> > build will have the correct timestamp. A subsequent cherry-pick (or
> > amend) changes the commit timestamp and if an incremental build is done
> > with a different KBUILD_BUILD_TIMESTAMP now, that new value is not taken
> > into consideration. But it should for reproducibility.
> >
> > Hence, whenever KBUILD_BUILD_TIMESTAMP is explicitly set, do not ignore
> > UTS_VERSION when making a decision about whether the regenerated version
> > of compile.h should be moved into place.
> >
> > [1] https://www.kernel.org/doc/html/latest/kbuild/reproducible-builds.html
> >
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: linux-kbuild@vger.kernel.org
> > Signed-off-by: Matthias Maennich <maennich@google.com>
> > ---
>
>
> Applied to linux-kbuild. Thanks.
>
This may not be a big deal, but when KBUILD_BUILD_TIMESTAMP is unset,
the timestamp is not updated. It still has a user-specified string.
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2021-06-17 1:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-12 14:18 [PATCH] kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set Matthias Maennich
2021-06-17 1:05 ` Masahiro Yamada
2021-06-17 1:43 ` Masahiro Yamada [this message]
2021-06-17 9:18 ` Matthias Maennich
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