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>
---
redhat/kernel.spec.template | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
diff --git a/redhat/kernel.spec.template b/redhat/kernel.spec.template
index 7cbfb9c139eb..82d439cfefe3 100644
--- a/redhat/kernel.spec.template
+++ b/redhat/kernel.spec.template
@@ -1,4 +1,30 @@
-# We have to override the new %%install behavior because, well... the kernel is special.
+# All Global changes to build and install go here.
+# Per the below section about __spec_install_pre, any rpm
+# environment changes that affect %%install need to go
+# here before the %%install macro is pre-built.
+
+# Disable LTO in userspace packages.
+%global _lto_cflags %{nil}
+
+
+
+# The kernel's %%install section is special
+# Normally the %%install section starts by cleaning up the BUILD_ROOT
+# like so:
+#
+# %%__spec_install_pre %%{___build_pre}\
+# [ "$RPM_BUILD_ROOT" != "/" ] && rm -rf "${RPM_BUILD_ROOT}"\
+# mkdir -p `dirname "$RPM_BUILD_ROOT"`\
+# mkdir "$RPM_BUILD_ROOT"\
+# %%{nil}
+#
+# But because of kernel variants, the %%build section, specifically
+# BuildKernel(), moves each variant to its final destination as the
+# variant is built. This violates the expectation of the %%install
+# section. As a result we snapshot the current env variables and
+# purposely leave out the removal section. All global wide changes
+# should be added above this line otherwise the %%install section
+# will not see them.
%global __spec_install_pre %{___build_pre}
# Short-term fix so the package builds with GCC 10.
--
GitLab
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