[PATCH] kernel.bbclass: Set pkg-config variables for building modules

[Munehisa Kamata <kamatam@amazon.com>]

The pkg-config workaround has been applied for kernel image building, but
not for module building. On x86, this can trigger rebuilding of objtool
unnecessary at do_compile_kernelmodules task. If the kernel is built with
CONFIG_DEBUG_INFO_BTF=y, the task even rebuilds vmlinux and leads to
inconsistent build-id between bzImage and vmlinux, and also BTF mismatches
between the bzImage and modules.

To avoid the inconsistency, apply the same workaround when building
modules. For kernels 5.19+, simply set HOSTPKG_CONFIG in the make command
line.

Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
---
 meta/classes-recipe/kernel.bbclass | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/meta/classes-recipe/kernel.bbclass b/meta/classes-recipe/kernel.bbclass
index a76aaee5ba..db4461e551 100644
--- a/meta/classes-recipe/kernel.bbclass
+++ b/meta/classes-recipe/kernel.bbclass
@@ -239,6 +239,8 @@ KERNEL_EXTRA_ARGS ?= ""
 EXTRA_OEMAKE += ' CC="${KERNEL_CC}" LD="${KERNEL_LD}" OBJCOPY="${KERNEL_OBJCOPY}" STRIP="${KERNEL_STRIP}"'
 EXTRA_OEMAKE += ' HOSTCC="${BUILD_CC}" HOSTCFLAGS="${BUILD_CFLAGS}" HOSTLDFLAGS="${BUILD_LDFLAGS}" HOSTCPP="${BUILD_CPP}"'
 EXTRA_OEMAKE += ' HOSTCXX="${BUILD_CXX}" HOSTCXXFLAGS="${BUILD_CXXFLAGS}"'
+# Only for newer kernels (5.19+), native pkg-config variables are set for older kernels when building kernel and modules
+EXTRA_OEMAKE += ' HOSTPKG_CONFIG="pkg-config-native"'
 
 KERNEL_ALT_IMAGETYPE ??= ""
 
@@ -356,9 +358,6 @@ kernel_do_compile() {
 	export PKG_CONFIG_LIBDIR="$PKG_CONFIG_DIR"
 	export PKG_CONFIG_SYSROOT_DIR=""
 
-	# for newer kernels (5.19+) there's a dedicated variable
-	export HOSTPKG_CONFIG="pkg-config-native"
-
 	if [ "${KERNEL_DEBUG_TIMESTAMPS}" != "1" ]; then
 		# kernel sources do not use do_unpack, so SOURCE_DATE_EPOCH may not
 		# be set....
@@ -408,6 +407,13 @@ addtask transform_kernel after do_compile before do_install
 
 do_compile_kernelmodules() {
 	unset CFLAGS CPPFLAGS CXXFLAGS LDFLAGS MACHINE
+
+	# setup native pkg-config variables (kconfig scripts call pkg-config directly, cannot generically be overriden to pkg-config-native)
+	export PKG_CONFIG_DIR="${STAGING_DIR_NATIVE}${libdir_native}/pkgconfig"
+	export PKG_CONFIG_PATH="$PKG_CONFIG_DIR:${STAGING_DATADIR_NATIVE}/pkgconfig"
+	export PKG_CONFIG_LIBDIR="$PKG_CONFIG_DIR"
+	export PKG_CONFIG_SYSROOT_DIR=""
+
 	if [ "${KERNEL_DEBUG_TIMESTAMPS}" != "1" ]; then
 		# kernel sources do not use do_unpack, so SOURCE_DATE_EPOCH may not
 		# be set....
-- 
2.34.1