Messages in this thread | | | Date | Thu, 17 Jun 2021 10:18:16 +0100 | From | Matthias Maennich <> | Subject | Re: [PATCH] kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set |
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On Thu, Jun 17, 2021 at 10:43:19AM +0900, Masahiro Yamada wrote: >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.
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.
I think treating this like any other 'random' prior timestamp is ok. So, I agree: not a big deal.
Cheers, Matthias > > > > >-- >Best Regards >Masahiro Yamada
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