[OS-BUILD PATCH] Allow building of kernel-tools standalone

[GitLab Bridge on behalf of dzickusrh]

From: Don Zickus <dzickus(a)redhat.com&gt;

For CKI and its cross-compile environment, it can not cross
compile userspace tools.  Instead we will native compiles them.

To allow this split, the kernel.spec needs to support only
building userspace stuff and not the kernel itself.

However the userspace tools need some vars defined. This
patch creates a new function and sets up those vars.

Also very useful for debugging userspace tools and skipping
the hour long kernel build times (like LTO).

To use this effectively, one would use
--without_up
--without_debug
--without_zfcpdump

Original author is Brian Masney <bmasney(a)redhat.com&gt;, which
I took from his RHEL-8 contribution.

Cc: Brian Masney <bmasney(a)redhat.com&gt;
Signed-off-by: Don Zickus <dzickus(a)redhat.com&gt;
---
 redhat/kernel.spec.template | 68 +++++++++++++++++++++++--------------
 1 file changed, 42 insertions(+), 26 deletions(-)

diff --git a/redhat/kernel.spec.template b/redhat/kernel.spec.template
index 7cbfb9c139eb..5354ee7cffdf 100644
--- a/redhat/kernel.spec.template
+++ b/redhat/kernel.spec.template
@@ -79,10 +79,9 @@ Summary: The Linux kernel
 
 %define pkg_release %{specrelease}
 
-# What parts do we want to build?  We must build at least one kernel.
-# These are the kernels that are built IF the architecture allows it.
-# All should default to 1 (enabled) and be flipped to 0 (disabled)
-# by later arch-specific checks.
+# What parts do we want to build? These are the kernels that are built IF the
+# architecture allows it. All should default to 1 (enabled) and be flipped to
+# 0 (disabled) by later arch-specific checks.
 
 # The following build options are enabled by default.
 # Use either --without <opt> in your rpmbuild command or force values
@@ -1338,33 +1337,18 @@ cp_vmlinux()
 
 %define make %{__make} %{?cross_opts} %{?make_opts}
HOSTCFLAGS="%{?build_hostcflags}" HOSTLDFLAGS="%{?build_hostldflags}"
 
-BuildKernel() {
-    MakeTarget=$1
-    KernelImage=$2
-    Flavour=$4
-    DoVDSO=$3
-    Flav=${Flavour:++${Flavour}}
-    InstallName=${5:-vmlinuz}
+InitBuildVars() {
+    # Initialize the kernel .config file and create some variables that are
+    # needed for the actual build process.
 
-    DoModules=1
-    if [ "$Flavour" = "zfcpdump" ]; then
-	    DoModules=0
-    fi
+    Flavour=$1
+    Flav=${Flavour:++${Flavour}}
 
     # Pick the right config file for the kernel we're building
     Config=kernel-%{version}-%{_target_cpu}${Flavour:+-${Flavour}}.config
     DevelDir=/usr/src/kernels/%{KVERREL}${Flav}
 
-    # When the bootable image is just the ELF kernel, strip it.
-    # We already copy the unstripped file into the debuginfo package.
-    if [ "$KernelImage" = vmlinux ]; then
-      CopyKernel=cp_vmlinux
-    else
-      CopyKernel=cp
-    fi
-
     KernelVer=%{version}-%{release}.%{_target_cpu}${Flav}
-    echo BUILDING A KERNEL FOR ${Flavour} %{_target_cpu}...
 
     # make sure EXTRAVERSION says what we want it to say
     # Trim the release if this is a CI build, since KERNELVERSION is limited to 64
characters
@@ -1375,8 +1359,6 @@ BuildKernel() {
     # if we are post rc1 this should match anyway so this won't matter
     perl -p -i -e 's/^PATCHLEVEL.*/PATCHLEVEL = %{patchlevel}/' Makefile
 
-    # and now to start the build process
-
     %{make} %{?_smp_mflags} mrproper
     cp configs/$Config .config
 
@@ -1393,6 +1375,32 @@ BuildKernel() {
     if [ "$Flavour" == "" ]; then
         KCFLAGS="$KCFLAGS %{?kpatch_kcflags}"
     fi
+}
+
+BuildKernel() {
+    MakeTarget=$1
+    KernelImage=$2
+    Flavour=$4
+    DoVDSO=$3
+    Flav=${Flavour:++${Flavour}}
+    InstallName=${5:-vmlinuz}
+
+    DoModules=1
+    if [ "$Flavour" = "zfcpdump" ]; then
+	    DoModules=0
+    fi
+
+    # When the bootable image is just the ELF kernel, strip it.
+    # We already copy the unstripped file into the debuginfo package.
+    if [ "$KernelImage" = vmlinux ]; then
+      CopyKernel=cp_vmlinux
+    else
+      CopyKernel=cp
+    fi
+
+    InitBuildVars $Flavour
+
+    echo BUILDING A KERNEL FOR ${Flavour} %{_target_cpu}...
 
     %{make} ARCH=$Arch olddefconfig >/dev/null
 
@@ -1920,6 +1928,14 @@ BuildKernel %make_target %kernel_image %{use_vdso} lpae
 BuildKernel %make_target %kernel_image %{_use_vdso}
 %endif
 
+%ifnarch noarch i686
+%if !%{with_debug} && !%{with_zfcpdump} && !%{with_up}
+# If only building the user space tools, then initialize the build environment
+# and some variables so that the various userspace tools can be built.
+InitBuildVars
+%endif
+%endif
+
 %global perf_make \
   %{__make} -s EXTRA_CFLAGS="${RPM_OPT_FLAGS}"
LDFLAGS="%{__global_ldflags}" %{?cross_opts} -C tools/perf V=1
NO_PERF_READ_VDSO32=1 NO_PERF_READ_VDSOX32=1 WERROR=0 NO_LIBUNWIND=1 HAVE_CPLUS_DEMANGLE=1
NO_GTK2=1 NO_STRLCPY=1 NO_BIONIC=1 prefix=%{_prefix} PYTHON=%{__python3}
 %if %{with_perf}
-- 
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