From 34bba21afd8be681c1bd1d88d8dc349c79aca9f7 Mon Sep 17 00:00:00 2001
From: Michael Marineau <michael.marineau@coreos.com>
Date: Fri, 7 Aug 2015 13:08:19 -0700
Subject: [PATCH] coreos-kernel: make build ccache friendly across versions

The absolute path to the source tree includes the kernel's version
number and that path then lands in the kernel source code via the
numerous __FILE__ macros in the kernel source. So if the kernel source
version changes, even with a minor revision only, the entire cache can
be invalidated.

Reshuffle the build tree so that $S is a directory of symlinks to the
source and a nested build directory, ensuring the entire build can use
relative paths. A directory of symlinks instead of a single directory
symlink is required to prevent make from resolving the source directory
path to the original versioned path.
---
 .../eclass/coreos-kernel.eclass               | 43 +++++++------------
 1 file changed, 16 insertions(+), 27 deletions(-)

diff --git a/sdk_container/src/third_party/coreos-overlay/eclass/coreos-kernel.eclass b/sdk_container/src/third_party/coreos-overlay/eclass/coreos-kernel.eclass
index 161424080f..b8ff160c9d 100644
--- a/sdk_container/src/third_party/coreos-overlay/eclass/coreos-kernel.eclass
+++ b/sdk_container/src/third_party/coreos-overlay/eclass/coreos-kernel.eclass
@@ -62,7 +62,7 @@ find_defconfig() {
 # As if using cpio isn't bad enough already.
 # If lib doesn't exist or isn't a symlink then nothing is returned.
 get_bootengine_lib() {
-	cpio -itv --quiet < bootengine.cpio | \
+	cpio -itv --quiet < build/bootengine.cpio | \
 		awk '$1 ~ /^l/ && $9 == "lib" { print $11 }'
 	assert
 }
@@ -80,7 +80,7 @@ update_bootengine_cpio() {
 		# squash file ownership to root for new files.
 		--owner=root:root
 		# append to our local copy of bootengine
-		-F "${S}/bootengine.cpio"
+		-F "${S}/build/bootengine.cpio"
 	)
 
 	echo "Updating bootengine.cpio"
@@ -93,10 +93,10 @@ kmake() {
 	if gcc-specs-pie; then
 		kernel_cflags="-nopie -fstack-check=no"
 	fi
-	emake -C "${KERNEL_DIR}" \
+	emake \
 		ARCH="${kernel_arch}" \
 		CROSS_COMPILE="${CHOST}-" \
-		KBUILD_OUTPUT="${S}" \
+		KBUILD_OUTPUT="build" \
 		KCFLAGS="${kernel_cflags}" \
 		LDFLAGS="" \
 		"$@"
@@ -111,7 +111,8 @@ shred_keys() {
 }
 
 coreos-kernel_src_unpack() {
-	mkdir "${S}" || die
+	mkdir -p "${S}/build" || die
+	ln -s "${KERNEL_DIR}"/* "${S}/" || die
 }
 
 coreos-kernel_src_prepare() {
@@ -120,25 +121,26 @@ coreos-kernel_src_prepare() {
 		die "Source is not clean! Run make mrproper in ${KERNEL_DIR}"
 	fi
 
-	restore_config .config
-	if [[ ! -f .config ]]; then
+	restore_config build/.config
+	if [[ ! -f build/.config ]]; then
 		local config="$(find_defconfig)"
 		elog "Building using default config ${config}"
-		cp "${config}" .config || die
+		cp "${config}" build/.config || die
 	fi
 
 	# copy the cpio initrd to the output build directory so we can tack it
 	# onto the kernel image itself.
-	cp "${ROOT}"/usr/share/bootengine/bootengine.cpio bootengine.cpio || die
+	cp "${ROOT}"/usr/share/bootengine/bootengine.cpio build/bootengine.cpio \
+		|| die "cp bootengine.cpio failed, try emerge-\$BOARD bootengine"
 }
 
 coreos-kernel_src_configure() {
 	if ! use audit; then
-		sed -i -e '/^CONFIG_CMDLINE=/s/"$/ audit=0"/' .config || die
+		sed -i -e '/^CONFIG_CMDLINE=/s/"$/ audit=0"/' build/.config || die
 	fi
 	if ! use selinux; then
-		sed -i -e '/CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE/d' .config || die
-		echo CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE=0 >> .config || die
+		sed -i -e '/CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE/d' build/.config || die
+		echo CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE=0 >> build/.config || die
 	fi
 
 	# Use default for any options not explitly set in defconfig
@@ -197,22 +199,9 @@ coreos-kernel_src_install() {
 	dosym "../../../../boot/config-${version}" \
 		"/usr/lib/modules/${version}/build/.config"
 
-	save_config defconfig
+	save_config build/defconfig
 
 	shred_keys
 }
 
-# TODO(marineam): remove this function once KBUILD_OUTPUT is removed
-# from src/scripts/setup_board
-coreos-kernel_pkg_postinst() {
-	[[ -n "${KBUILD_OUTPUT}" ]] || return 0
-	# linux-info always expects to be able to find the current .config
-	# so copy it into the build tree if it isn't already there.
-	if ! cmp --quiet "${ROOT}/usr/boot/config" "${KBUILD_OUTPUT}/.config"; then
-		cp "${ROOT}/usr/boot/config" "${KBUILD_OUTPUT}/.config"
-		chown ${PORTAGE_USERNAME:-portage}:${PORTAGE_GRPNAME:-portage} \
-			"${KBUILD_OUTPUT}/.config"
-	fi
-}
-
-EXPORT_FUNCTIONS src_unpack src_prepare src_configure src_compile src_install pkg_postinst
+EXPORT_FUNCTIONS src_unpack src_prepare src_configure src_compile src_install