On Wed, Oct 28, 2020 at 08:03:37PM -0000, GitLab Bridge on behalf of dzickusrh wrote:
> From: Don Zickus <dzickus@xxxxxxxxxx>
>
> There are two parts to this fix. One is using the recommended way
> to disable LTO. The other is to make it work for the kernel.spec
> file.
>
> Various kernel-tool programs (like perf) can not handle LTO yet, so
> they are disabled.
>
> This is done with '%define _lto_cflags {nil}'.
>
> However that doesn't quite work for the kernel for the %install
> section. It works for the %build section.
>
> Oddly, back at the birth of dist-git, the initial kernel.spec
> file was imported with a line at the top
>
> %global __spec_install_pre %{___build_pre}
>
> For whatever reason, the kernel was deemed special and that line
> pre-built the %install scripts _before_ the lto_cflags could
> dynamically be disabled.
>
> Moving the _lto_cflags line above the _pre line disables LTO for both the
> %build and %install sections of the spec file successfully.
>
> However, because that _pre line is unintiutive and caused hours
> of debugging headache, I hacked up the output to see what the
> %__spec_install_pre and ___build_pre looked like at the
> beginning of the %install section. The idea was __build_pre
> is what we want going forward.
>
> Unfortunately, after examining the results, I learned the %install
> section expects a clean RPM_BUILD_ROOT. But the kernel %build
> section puts each compiled variant into the RPM_BUILD_ROOT as
> it completes. Thus is gets removed on %install setup. So the
> %__spec_install_pre line has to stay.
>
> Instead I add a bunch of comments explaining why it is necessary
> and where to add changes like _lto_cflags. This hopefully
> reduces headaches in the future.
>
> V2: restore __spec_install_pre line and add comments.
>
> Cc: Jeff Law <law@xxxxxxxxxx>
> Signed-off-by: Don Zickus <dzickus@xxxxxxxxxx>
I like this version much better.
Acked-by: Brian Masney <bmasney@xxxxxxxxxx>
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