The cirros image was rebuilt against the 3.13.0-83 kernel, drivers e1000e, igbvf...
[packages/trusty/cirros-testvm.git] / cirros-testvm / src-cirros / buildroot-2015.05 / linux / linux.mk
diff --git a/cirros-testvm/src-cirros/buildroot-2015.05/linux/linux.mk b/cirros-testvm/src-cirros/buildroot-2015.05/linux/linux.mk
new file mode 100644 (file)
index 0000000..c765954
--- /dev/null
@@ -0,0 +1,377 @@
+################################################################################
+#
+# Linux kernel target
+#
+################################################################################
+
+LINUX_VERSION = $(call qstrip,$(BR2_LINUX_KERNEL_VERSION))
+LINUX_LICENSE = GPLv2
+LINUX_LICENSE_FILES = COPYING
+
+# Compute LINUX_SOURCE and LINUX_SITE from the configuration
+ifeq ($(BR2_LINUX_KERNEL_CUSTOM_TARBALL),y)
+LINUX_TARBALL = $(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_TARBALL_LOCATION))
+LINUX_SITE = $(patsubst %/,%,$(dir $(LINUX_TARBALL)))
+LINUX_SOURCE = $(notdir $(LINUX_TARBALL))
+BR_NO_CHECK_HASH_FOR += $(LINUX_SOURCE)
+else ifeq ($(BR2_LINUX_KERNEL_CUSTOM_LOCAL),y)
+LINUX_SITE = $(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_LOCAL_PATH))
+LINUX_SITE_METHOD = local
+else ifeq ($(BR2_LINUX_KERNEL_CUSTOM_GIT),y)
+LINUX_SITE = $(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_REPO_URL))
+LINUX_SITE_METHOD = git
+else ifeq ($(BR2_LINUX_KERNEL_CUSTOM_HG),y)
+LINUX_SITE = $(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_REPO_URL))
+LINUX_SITE_METHOD = hg
+else
+LINUX_SOURCE = linux-$(LINUX_VERSION).tar.xz
+ifeq ($(BR2_LINUX_KERNEL_CUSTOM_VERSION),y)
+BR_NO_CHECK_HASH_FOR += $(LINUX_SOURCE)
+endif
+ifeq ($(BR2_LINUX_KERNEL_SAME_AS_HEADERS)$(BR2_KERNEL_HEADERS_VERSION),yy)
+BR_NO_CHECK_HASH_FOR += $(LINUX_SOURCE)
+endif
+# In X.Y.Z, get X and Y. We replace dots and dashes by spaces in order
+# to use the $(word) function. We support versions such as 4.0, 3.1,
+# 2.6.32, 2.6.32-rc1, 3.0-rc6, etc.
+ifeq ($(findstring x2.6.,x$(LINUX_VERSION)),x2.6.)
+LINUX_SITE = $(BR2_KERNEL_MIRROR)/linux/kernel/v2.6
+else ifeq ($(findstring x3.,x$(LINUX_VERSION)),x3.)
+LINUX_SITE = $(BR2_KERNEL_MIRROR)/linux/kernel/v3.x
+else ifeq ($(findstring x4.,x$(LINUX_VERSION)),x4.)
+LINUX_SITE = $(BR2_KERNEL_MIRROR)/linux/kernel/v4.x
+endif
+# release candidates are in testing/ subdir
+ifneq ($(findstring -rc,$(LINUX_VERSION)),)
+LINUX_SITE := $(LINUX_SITE)/testing
+endif # -rc
+endif
+
+LINUX_PATCHES = $(call qstrip,$(BR2_LINUX_KERNEL_PATCH))
+
+# We rely on the generic package infrastructure to download and apply
+# remote patches (downloaded from ftp, http or https). For local
+# patches, we can't rely on that infrastructure, because there might
+# be directories in the patch list (unlike for other packages).
+LINUX_PATCH = $(filter ftp://% http://% https://%,$(LINUX_PATCHES))
+
+LINUX_INSTALL_IMAGES = YES
+LINUX_DEPENDENCIES += host-kmod host-lzop
+
+ifeq ($(BR2_LINUX_KERNEL_UBOOT_IMAGE),y)
+LINUX_DEPENDENCIES += host-uboot-tools
+endif
+
+LINUX_MAKE_FLAGS = \
+       HOSTCC="$(HOSTCC)" \
+       HOSTCFLAGS="$(HOSTCFLAGS)" \
+       ARCH=$(KERNEL_ARCH) \
+       INSTALL_MOD_PATH=$(TARGET_DIR) \
+       CROSS_COMPILE="$(CCACHE) $(TARGET_CROSS)" \
+       DEPMOD=$(HOST_DIR)/sbin/depmod
+
+LINUX_MAKE_ENV = \
+       $(TARGET_MAKE_ENV) \
+       BR_BINARIES_DIR=$(BINARIES_DIR)
+
+# Get the real Linux version, which tells us where kernel modules are
+# going to be installed in the target filesystem.
+LINUX_VERSION_PROBED = $(shell $(MAKE) $(LINUX_MAKE_FLAGS) -C $(LINUX_DIR) --no-print-directory -s kernelrelease)
+
+ifeq ($(BR2_LINUX_KERNEL_USE_INTREE_DTS),y)
+KERNEL_DTS_NAME = $(call qstrip,$(BR2_LINUX_KERNEL_INTREE_DTS_NAME))
+else ifeq ($(BR2_LINUX_KERNEL_USE_CUSTOM_DTS),y)
+# We keep only the .dts files, so that the user can specify both .dts
+# and .dtsi files in BR2_LINUX_KERNEL_CUSTOM_DTS_PATH. Both will be
+# copied to arch/<arch>/boot/dts, but only the .dts files will
+# actually be generated as .dtb.
+KERNEL_DTS_NAME = $(basename $(filter %.dts,$(notdir $(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_DTS_PATH)))))
+endif
+
+ifeq ($(BR2_LINUX_KERNEL_DTS_SUPPORT)$(KERNEL_DTS_NAME),y)
+$(error No kernel device tree source specified, check your \
+BR2_LINUX_KERNEL_USE_INTREE_DTS / BR2_LINUX_KERNEL_USE_CUSTOM_DTS settings)
+endif
+
+ifeq ($(BR2_LINUX_KERNEL_APPENDED_DTB),y)
+ifneq ($(words $(KERNEL_DTS_NAME)),1)
+$(error Kernel with appended device tree needs exactly one DTS source. \
+       Check BR2_LINUX_KERNEL_INTREE_DTS_NAME or BR2_LINUX_KERNEL_CUSTOM_DTS_PATH.)
+endif
+endif
+
+KERNEL_DTBS = $(addsuffix .dtb,$(KERNEL_DTS_NAME))
+
+ifeq ($(BR2_LINUX_KERNEL_IMAGE_TARGET_CUSTOM),y)
+LINUX_IMAGE_NAME = $(call qstrip,$(BR2_LINUX_KERNEL_IMAGE_NAME))
+LINUX_TARGET_NAME = $(call qstrip,$(BR2_LINUX_KERNEL_IMAGE_TARGET_NAME))
+ifeq ($(LINUX_IMAGE_NAME),)
+LINUX_IMAGE_NAME = $(LINUX_TARGET_NAME)
+endif
+else
+ifeq ($(BR2_LINUX_KERNEL_UIMAGE),y)
+LINUX_IMAGE_NAME = uImage
+else ifeq ($(BR2_LINUX_KERNEL_APPENDED_UIMAGE),y)
+LINUX_IMAGE_NAME = uImage
+else ifeq ($(BR2_LINUX_KERNEL_BZIMAGE),y)
+LINUX_IMAGE_NAME = bzImage
+else ifeq ($(BR2_LINUX_KERNEL_ZIMAGE),y)
+LINUX_IMAGE_NAME = zImage
+else ifeq ($(BR2_LINUX_KERNEL_APPENDED_ZIMAGE),y)
+LINUX_IMAGE_NAME = zImage
+else ifeq ($(BR2_LINUX_KERNEL_CUIMAGE),y)
+LINUX_IMAGE_NAME = cuImage.$(KERNEL_DTS_NAME)
+else ifeq ($(BR2_LINUX_KERNEL_SIMPLEIMAGE),y)
+LINUX_IMAGE_NAME = simpleImage.$(KERNEL_DTS_NAME)
+else ifeq ($(BR2_LINUX_KERNEL_LINUX_BIN),y)
+LINUX_IMAGE_NAME = linux.bin
+else ifeq ($(BR2_LINUX_KERNEL_VMLINUX_BIN),y)
+LINUX_IMAGE_NAME = vmlinux.bin
+else ifeq ($(BR2_LINUX_KERNEL_VMLINUX),y)
+LINUX_IMAGE_NAME = vmlinux
+else ifeq ($(BR2_LINUX_KERNEL_VMLINUZ),y)
+LINUX_IMAGE_NAME = vmlinuz
+endif
+# The if-else blocks above are all the image types we know of, and all
+# come from a Kconfig choice, so we know we have LINUX_IMAGE_NAME set
+# to something
+LINUX_TARGET_NAME = $(LINUX_IMAGE_NAME)
+endif
+
+LINUX_KERNEL_UIMAGE_LOADADDR = $(call qstrip,$(BR2_LINUX_KERNEL_UIMAGE_LOADADDR))
+ifneq ($(LINUX_KERNEL_UIMAGE_LOADADDR),)
+LINUX_MAKE_FLAGS += LOADADDR="$(LINUX_KERNEL_UIMAGE_LOADADDR)"
+endif
+
+# Compute the arch path, since i386 and x86_64 are in arch/x86 and not
+# in arch/$(KERNEL_ARCH). Even if the kernel creates symbolic links
+# for bzImage, arch/i386 and arch/x86_64 do not exist when copying the
+# defconfig file.
+ifeq ($(KERNEL_ARCH),i386)
+KERNEL_ARCH_PATH = $(LINUX_DIR)/arch/x86
+else ifeq ($(KERNEL_ARCH),x86_64)
+KERNEL_ARCH_PATH = $(LINUX_DIR)/arch/x86
+else
+KERNEL_ARCH_PATH = $(LINUX_DIR)/arch/$(KERNEL_ARCH)
+endif
+
+ifeq ($(BR2_LINUX_KERNEL_VMLINUX),y)
+LINUX_IMAGE_PATH = $(LINUX_DIR)/$(LINUX_IMAGE_NAME)
+else ifeq ($(BR2_LINUX_KERNEL_VMLINUZ),y)
+LINUX_IMAGE_PATH = $(LINUX_DIR)/$(LINUX_IMAGE_NAME)
+else
+LINUX_IMAGE_PATH = $(KERNEL_ARCH_PATH)/boot/$(LINUX_IMAGE_NAME)
+endif # BR2_LINUX_KERNEL_VMLINUX
+
+define LINUX_APPLY_LOCAL_PATCHES
+       for p in $(filter-out ftp://% http://% https://%,$(LINUX_PATCHES)) ; do \
+               if test -d $$p ; then \
+                       $(APPLY_PATCHES) $(@D) $$p \*.patch || exit 1 ; \
+               else \
+                       $(APPLY_PATCHES) $(@D) `dirname $$p` `basename $$p` || exit 1; \
+               fi \
+       done
+endef
+
+LINUX_POST_PATCH_HOOKS += LINUX_APPLY_LOCAL_PATCHES
+
+ifeq ($(BR2_LINUX_KERNEL_USE_DEFCONFIG),y)
+KERNEL_SOURCE_CONFIG = $(KERNEL_ARCH_PATH)/configs/$(call qstrip,$(BR2_LINUX_KERNEL_DEFCONFIG))_defconfig
+else ifeq ($(BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG),y)
+KERNEL_SOURCE_CONFIG = $(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE))
+endif
+
+LINUX_KCONFIG_FILE = $(KERNEL_SOURCE_CONFIG)
+LINUX_KCONFIG_EDITORS = menuconfig xconfig gconfig nconfig
+LINUX_KCONFIG_OPTS = $(LINUX_MAKE_FLAGS)
+
+define LINUX_KCONFIG_FIXUP_CMDS
+       $(if $(BR2_arm)$(BR2_armeb),
+               $(call KCONFIG_ENABLE_OPT,CONFIG_AEABI,$(@D)/.config))
+       $(if $(BR2_TARGET_ROOTFS_CPIO),
+               $(call KCONFIG_ENABLE_OPT,CONFIG_BLK_DEV_INITRD,$(@D)/.config))
+       # As the kernel gets compiled before root filesystems are
+       # built, we create a fake cpio file. It'll be
+       # replaced later by the real cpio archive, and the kernel will be
+       # rebuilt using the linux-rebuild-with-initramfs target.
+       $(if $(BR2_TARGET_ROOTFS_INITRAMFS),
+               touch $(BINARIES_DIR)/rootfs.cpio
+               $(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_SOURCE,"$${BR_BINARIES_DIR}/rootfs.cpio",$(@D)/.config)
+               $(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_UID,0,$(@D)/.config)
+               $(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_GID,0,$(@D)/.config))
+       $(if $(BR2_ROOTFS_DEVICE_CREATION_STATIC),,
+               $(call KCONFIG_ENABLE_OPT,CONFIG_DEVTMPFS,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_DEVTMPFS_MOUNT,$(@D)/.config))
+       $(if $(BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV),
+               $(call KCONFIG_ENABLE_OPT,CONFIG_INOTIFY_USER,$(@D)/.config))
+       $(if $(BR2_PACKAGE_KTAP),
+               $(call KCONFIG_ENABLE_OPT,CONFIG_DEBUG_FS,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_EVENT_TRACING,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_PERF_EVENTS,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_FUNCTION_TRACER,$(@D)/.config))
+       $(if $(BR2_PACKAGE_SYSTEMD),
+               $(call KCONFIG_ENABLE_OPT,CONFIG_CGROUPS,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_INOTIFY_USER,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_FHANDLE,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_AUTOFS4_FS,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_TMPFS_POSIX_ACL,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_TMPFS_POSIX_XATTR,$(@D)/.config))
+       $(if $(BR2_PACKAGE_SMACK),
+               $(call KCONFIG_ENABLE_OPT,CONFIG_SECURITY,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_SECURITY_SMACK,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_SECURITY_NETWORK,$(@D)/.config))
+       $(if $(BR2_PACKAGE_IPTABLES),
+               $(call KCONFIG_ENABLE_OPT,CONFIG_IP_NF_IPTABLES,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_IP_NF_FILTER,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_NETFILTER,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_NETFILTER_XTABLES,$(@D)/.config))
+       $(if $(BR2_PACKAGE_XTABLES_ADDONS),
+               $(call KCONFIG_ENABLE_OPT,CONFIG_NF_CONNTRACK,$(@D)/.config)
+               $(call KCONFIG_ENABLE_OPT,CONFIG_NF_CONNTRACK_MARK,$(@D)/.config))
+       $(if $(BR2_LINUX_KERNEL_APPENDED_DTB),
+               $(call KCONFIG_ENABLE_OPT,CONFIG_ARM_APPENDED_DTB,$(@D)/.config))
+endef
+
+ifeq ($(BR2_LINUX_KERNEL_DTS_SUPPORT),y)
+ifeq ($(BR2_LINUX_KERNEL_DTB_IS_SELF_BUILT),)
+define LINUX_BUILD_DTB
+       $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) $(KERNEL_DTBS)
+endef
+define LINUX_INSTALL_DTB
+       # dtbs moved from arch/<ARCH>/boot to arch/<ARCH>/boot/dts since 3.8-rc1
+       cp $(addprefix \
+               $(KERNEL_ARCH_PATH)/boot/$(if $(wildcard \
+               $(addprefix $(KERNEL_ARCH_PATH)/boot/dts/,$(KERNEL_DTBS))),dts/),$(KERNEL_DTBS)) \
+               $(BINARIES_DIR)/
+endef
+define LINUX_INSTALL_DTB_TARGET
+       # dtbs moved from arch/<ARCH>/boot to arch/<ARCH>/boot/dts since 3.8-rc1
+       cp $(addprefix \
+               $(KERNEL_ARCH_PATH)/boot/$(if $(wildcard \
+               $(addprefix $(KERNEL_ARCH_PATH)/boot/dts/,$(KERNEL_DTBS))),dts/),$(KERNEL_DTBS)) \
+               $(TARGET_DIR)/boot/
+endef
+endif
+endif
+
+ifeq ($(BR2_LINUX_KERNEL_APPENDED_DTB),y)
+# dtbs moved from arch/$ARCH/boot to arch/$ARCH/boot/dts since 3.8-rc1
+define LINUX_APPEND_DTB
+       if [ -e $(KERNEL_ARCH_PATH)/boot/$(KERNEL_DTS_NAME).dtb ]; then \
+               cat $(KERNEL_ARCH_PATH)/boot/$(KERNEL_DTS_NAME).dtb; \
+       else \
+               cat $(KERNEL_ARCH_PATH)/boot/dts/$(KERNEL_DTS_NAME).dtb; \
+       fi >> $(KERNEL_ARCH_PATH)/boot/zImage
+endef
+ifeq ($(BR2_LINUX_KERNEL_APPENDED_UIMAGE),y)
+# We need to generate a new u-boot image that takes into
+# account the extra-size added by the device tree at the end
+# of the image. To do so, we first need to retrieve both load
+# address and entry point for the kernel from the already
+# generate uboot image before using mkimage -l.
+LINUX_APPEND_DTB += $(sep) MKIMAGE_ARGS=`$(MKIMAGE) -l $(LINUX_IMAGE_PATH) |\
+       sed -n -e 's/Image Name:[ ]*\(.*\)/-n \1/p' -e 's/Load Address:/-a/p' -e 's/Entry Point:/-e/p'`; \
+       $(MKIMAGE) -A $(MKIMAGE_ARCH) -O linux \
+       -T kernel -C none $${MKIMAGE_ARGS} \
+       -d $(KERNEL_ARCH_PATH)/boot/zImage $(LINUX_IMAGE_PATH);
+endif
+endif
+
+# Compilation. We make sure the kernel gets rebuilt when the
+# configuration has changed.
+define LINUX_BUILD_CMDS
+       $(if $(BR2_LINUX_KERNEL_USE_CUSTOM_DTS),
+               cp $(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_DTS_PATH)) $(KERNEL_ARCH_PATH)/boot/dts/)
+       $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) $(LINUX_TARGET_NAME)
+       @if grep -q "CONFIG_MODULES=y" $(@D)/.config; then      \
+               $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) modules ;        \
+       fi
+       $(LINUX_BUILD_DTB)
+       $(LINUX_APPEND_DTB)
+endef
+
+
+ifeq ($(BR2_LINUX_KERNEL_INSTALL_TARGET),y)
+define LINUX_INSTALL_KERNEL_IMAGE_TO_TARGET
+       install -m 0644 -D $(LINUX_IMAGE_PATH) $(TARGET_DIR)/boot/$(LINUX_IMAGE_NAME)
+       $(LINUX_INSTALL_DTB_TARGET)
+endef
+endif
+
+
+define LINUX_INSTALL_HOST_TOOLS
+       # Installing dtc (device tree compiler) as host tool, if selected
+       if grep -q "CONFIG_DTC=y" $(@D)/.config; then   \
+               $(INSTALL) -D -m 0755 $(@D)/scripts/dtc/dtc $(HOST_DIR)/usr/bin/dtc ;   \
+       fi
+endef
+
+
+define LINUX_INSTALL_IMAGES_CMDS
+       cp $(LINUX_IMAGE_PATH) $(BINARIES_DIR)
+       $(LINUX_INSTALL_DTB)
+endef
+
+define LINUX_INSTALL_TARGET_CMDS
+       $(LINUX_INSTALL_KERNEL_IMAGE_TO_TARGET)
+       # Install modules and remove symbolic links pointing to build
+       # directories, not relevant on the target
+       @if grep -q "CONFIG_MODULES=y" $(@D)/.config; then      \
+               $(LINUX_MAKE_ENV) $(MAKE1) $(LINUX_MAKE_FLAGS) -C $(@D) modules_install; \
+               rm -f $(TARGET_DIR)/lib/modules/$(LINUX_VERSION_PROBED)/build ;         \
+               rm -f $(TARGET_DIR)/lib/modules/$(LINUX_VERSION_PROBED)/source ;        \
+       fi
+       $(LINUX_INSTALL_HOST_TOOLS)
+endef
+
+# Note: our package infrastructure uses the full-path of the last-scanned
+# Makefile to determine what package we're currently defining, using the
+# last directory component in the path. As such, including other Makefile,
+# like below, before we call one of the *-package macro is usally not
+# working.
+# However, since the files we include here are in the same directory as
+# the current Makefile, we are OK. But this is a hard requirement: files
+# included here *must* be in the same directory!
+include $(sort $(wildcard linux/linux-ext-*.mk))
+
+LINUX_PATCH_DEPENDENCIES += $(foreach ext,$(LINUX_EXTENSIONS),\
+       $(if $(BR2_LINUX_KERNEL_EXT_$(call UPPERCASE,$(ext))),$(ext)))
+
+LINUX_PRE_PATCH_HOOKS += $(foreach ext,$(LINUX_EXTENSIONS),\
+       $(if $(BR2_LINUX_KERNEL_EXT_$(call UPPERCASE,$(ext))),\
+               $(call UPPERCASE,$(ext))_PREPARE_KERNEL))
+
+$(eval $(kconfig-package))
+
+# Support for rebuilding the kernel after the cpio archive has
+# been generated in $(BINARIES_DIR)/rootfs.cpio.
+$(LINUX_DIR)/.stamp_initramfs_rebuilt: $(LINUX_DIR)/.stamp_target_installed $(LINUX_DIR)/.stamp_images_installed $(BINARIES_DIR)/rootfs.cpio
+       @$(call MESSAGE,"Rebuilding kernel with initramfs")
+       # Build the kernel.
+       $(LINUX_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) $(LINUX_TARGET_NAME)
+       $(LINUX_APPEND_DTB)
+       # Copy the kernel image to its final destination
+       cp $(LINUX_IMAGE_PATH) $(BINARIES_DIR)
+       # If there is a .ub file copy it to the final destination
+       test ! -f $(LINUX_IMAGE_PATH).ub || cp $(LINUX_IMAGE_PATH).ub $(BINARIES_DIR)
+       $(Q)touch $@
+
+# The initramfs building code must make sure this target gets called
+# after it generated the initramfs list of files.
+linux-rebuild-with-initramfs: $(LINUX_DIR)/.stamp_initramfs_rebuilt
+
+# Checks to give errors that the user can understand
+ifeq ($(BR_BUILDING),y)
+ifeq ($(BR2_LINUX_KERNEL_USE_DEFCONFIG),y)
+ifeq ($(call qstrip,$(BR2_LINUX_KERNEL_DEFCONFIG)),)
+$(error No kernel defconfig name specified, check your BR2_LINUX_KERNEL_DEFCONFIG setting)
+endif
+endif
+
+ifeq ($(BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG),y)
+ifeq ($(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE)),)
+$(error No kernel configuration file specified, check your BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE setting)
+endif
+endif
+
+endif