rpiGenImage/bootstrap.d/13-kernel.sh

#
# Build and Setup RPi2/3/4 Kernel 4.XX 5.XX
#

# Load utility functions
. ./functions.sh

# Need to use kali kernel src if nexmon is enabled
if [ "$ENABLE_NEXMON" = true ] ; then
  KERNEL_URL="${KALI_KERNEL_URL}"
  # Clear Branch and KernelSRC_DIR if using nexmon. Everyone will forget to clone kali kernel instead of nomrla kernel
  KERNEL_BRANCH=""
  KERNELSRC_DIR=""
fi

# Fetch and build latest raspberry kernel
case "$BUILD_KERNEL" in
  "build")
#if [ "$BUILD_KERNEL" = build ] ; then
  # Setup source directory
  mkdir -p "${KERNEL_DIR}"

  # Copy existing kernel sources into chroot directory
  if [ -n "$KERNELSRC_DIR" ] && [ -d "$KERNELSRC_DIR" ] ; then
    # Copy kernel sources and include hidden files
    cp -r "${KERNELSRC_DIR}/". "${KERNEL_DIR}"

    # Clean the kernel sources
    if [ "$KERNELSRC_CLEAN" = true ] && [ "$KERNELSRC_PREBUILT" = false ] ; then
      make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" mrproper
    fi
  else # KERNELSRC_DIR=""
    # Create temporary directory for kernel sources
    temp_dir=$(as_nobody mktemp -d)

    # Fetch current RPi2/3/4 kernel sources
    if [ -z "${KERNEL_BRANCH}" ] ; then
      as_nobody -H git -C "${temp_dir}" clone --depth=1 "${KERNEL_URL}" linux
    else
      as_nobody -H git -C "${temp_dir}" clone --depth=1 --branch "${KERNEL_BRANCH}" "${KERNEL_URL}" linux
    fi

    # Copy downloaded kernel sources
    cp -r "${temp_dir}/linux/"* "${KERNEL_DIR}"

    # Remove temporary directory for kernel sources
    rm -fr "${temp_dir}"

    # Set permissions of the kernel sources
    chown -R root:root "${R}/usr/src"
  fi

  # Calculate optimal number of kernel building threads
  if [ -n "$KERNEL_THREADS" ] && [ -r /proc/cpuinfo ] ; then
    KERNEL_THREADS=$(grep -c processor /proc/cpuinfo)
  fi
  
# TODO: Check if defined Threadcount is higher than actual cores  
#  if [ "$KERNEL_THREADS" > grep -c processor /proc/cpuinfo] ; then
#	  echo "Defined more Threads than core assigned to this system"
#	  exit 1
#  fi
  
  #Copy 32bit config to 64bit
  if [ "$ENABLE_QEMU" = true ] && [ "$KERNEL_ARCH" = arm64 ]; then
  cp "${KERNEL_DIR}"/arch/arm/configs/vexpress_defconfig "${KERNEL_DIR}"/arch/arm64/configs/
  fi

  # Configure and build kernel
  if [ "$KERNELSRC_PREBUILT" = false ] ; then
    # Remove device, network and filesystem drivers from kernel configuration
    if [ "$REDUCE_KERNEL" = true ] ; then
      make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" "${KERNEL_DEFCONFIG}"
      sed -i\
      -e "s/\(^CONFIG_SND.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_SOUND.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_AC97.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_VIDEO_.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_MEDIA_TUNER.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_DVB.*\=\)[ym]/\1n/"\
      -e "s/\(^CONFIG_REISERFS.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_JFS.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_XFS.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_GFS2.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_OCFS2.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_BTRFS.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_HFS.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_JFFS2.*\=\)[ym]/\1n/"\
      -e "s/\(^CONFIG_UBIFS.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_SQUASHFS.*\=\)[ym]/\1n/"\
      -e "s/\(^CONFIG_W1.*\=\)[ym]/\1n/"\
      -e "s/\(^CONFIG_HAMRADIO.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_CAN.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_IRDA.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_BT_.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_WIMAX.*\=\)[ym]/\1n/"\
      -e "s/\(^CONFIG_6LOWPAN.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_IEEE802154.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_NFC.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_FB_TFT=.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_TOUCHSCREEN.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_USB_GSPCA_.*\=\).*/\1n/"\
      -e "s/\(^CONFIG_DRM.*\=\).*/\1n/"\
      "${KERNEL_DIR}/.config"
    fi

    if [ "$KERNELSRC_CONFIG" = true ] ; then
      # Load default raspberry kernel configuration
      make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" "${KERNEL_DEFCONFIG}"

      #Switch to KERNELSRC_DIR so we can use set_kernel_config
      cd "${KERNEL_DIR}" || exit
	  
	  # Enable RPI POE HAT fan
	  if [ "$KERNEL_POEHAT" = true ]; then
	  set_kernel_config CONFIG_SENSORS_RPI_POE_FAN m
	  fi

	  # Enable per-interface network priority control
	  # (for systemd-nspawn)
	  if [ "$KERNEL_NSPAN" = true ]; then
	  set_kernel_config CONFIG_CGROUP_NET_PRIO y
	  fi
	  
	  # Compile in BTRFS
	  if [ "$KERNEL_BTRFS" = true ]; then
	  set_kernel_config CONFIG_BTRFS_FS y
	  set_kernel_config CONFIG_BTRFS_FS_POSIX_ACL y
	  set_kernel_config CONFIG_BTRFS_FS_REF_VERIFY y
	  fi
	  
	  # Diffie-Hellman operations on retained keys
	  # (required for >keyutils-1.6)
	  if [ "$KERNEL_DHKEY" = true ]; then
		set_kernel_config CONFIG_KEY_DH_OPERATIONS y
	  fi 
	  
	  if [ "$KERNEL_ARCH" = arm64 ] && [ "$ENABLE_QEMU" = false ]; then
	    # Mask this temporarily during switch to rpi-4.19.y
	    #Fix SD_DRIVER upstream and downstream mess in 64bit RPIdeb_config
	    # use correct driver MMC_BCM2835_MMC instead of MMC_BCM2835_SDHOST - see https://www.raspberrypi.org/forums/viewtopic.php?t=210225
	    #set_kernel_config CONFIG_MMC_BCM2835 n
	    #set_kernel_config CONFIG_MMC_SDHCI_IPROC n
	    #set_kernel_config CONFIG_USB_DWC2 n
	    #sed -i "s|depends on MMC_BCM2835_MMC && MMC_BCM2835_DMA|depends on MMC_BCM2835_MMC|" "${KERNEL_DIR}"/drivers/mmc/host/Kconfig
	  
	    #VLAN got disabled without reason in arm64bit
	    set_kernel_config CONFIG_IPVLAN m
	  fi
	  
	  # enable ZSWAP see https://askubuntu.com/a/472227 or https://wiki.archlinux.org/index.php/zswap
      if [ "$KERNEL_ZSWAP" = true ] ; then
        set_kernel_config CONFIG_ZPOOL y
        set_kernel_config CONFIG_ZSWAP y
        set_kernel_config CONFIG_ZBUD y
        set_kernel_config CONFIG_Z3FOLD y
        set_kernel_config CONFIG_ZSMALLOC y
        set_kernel_config CONFIG_PGTABLE_MAPPING y
	    set_kernel_config CONFIG_LZO_COMPRESS y
	  fi
	  
	  if [ "$RPI_MODEL" = 4 ] ; then
	  # Following are set in current 32-bit LPAE kernel
	    set_kernel_config CONFIG_CGROUP_PIDS y
	    set_kernel_config CONFIG_NET_IPVTI m
	    set_kernel_config CONFIG_NF_TABLES_SET m
	    set_kernel_config CONFIG_NF_TABLES_INET y
	    set_kernel_config CONFIG_NF_TABLES_NETDEV y
	    set_kernel_config CONFIG_NF_FLOW_TABLE m
	    set_kernel_config CONFIG_NFT_FLOW_OFFLOAD m
	    set_kernel_config CONFIG_NFT_CONNLIMIT m
	    set_kernel_config CONFIG_NFT_TUNNEL m
	    set_kernel_config CONFIG_NFT_OBJREF m
	    set_kernel_config CONFIG_NFT_FIB_IPV4 m
	    set_kernel_config CONFIG_NFT_FIB_IPV6 m
	    set_kernel_config CONFIG_NFT_FIB_INET m
	    set_kernel_config CONFIG_NFT_SOCKET m
	    set_kernel_config CONFIG_NFT_OSF m
	    set_kernel_config CONFIG_NFT_TPROXY m
	    set_kernel_config CONFIG_NF_DUP_NETDEV m
	    set_kernel_config CONFIG_NFT_DUP_NETDEV m
	    set_kernel_config CONFIG_NFT_FWD_NETDEV m
	    set_kernel_config CONFIG_NFT_FIB_NETDEV m
	    set_kernel_config CONFIG_NF_FLOW_TABLE_INET m
	    set_kernel_config CONFIG_NF_FLOW_TABLE m
	    set_kernel_config CONFIG_NETFILTER_XT_MATCH_SOCKET m
	    set_kernel_config CONFIG_NFT_CHAIN_ROUTE_IPV6 m
	    set_kernel_config CONFIG_NFT_CHAIN_NAT_IPV6 m
	    set_kernel_config CONFIG_NFT_MASQ_IPV6 m
	    set_kernel_config CONFIG_NFT_REDIR_IPV6 m
	    set_kernel_config CONFIG_NFT_REJECT_IPV6 m
	    set_kernel_config CONFIG_NFT_DUP_IPV6 m
	    set_kernel_config CONFIG_NFT_FIB_IPV6 m
	    set_kernel_config CONFIG_NF_FLOW_TABLE_IPV6 m
	    set_kernel_config CONFIG_NF_TABLES_BRIDGE m
	    set_kernel_config CONFIG_NFT_BRIDGE_REJECT m
	    set_kernel_config CONFIG_NF_LOG_BRIDGE m
	    set_kernel_config CONFIG_MT76_CORE m
	    set_kernel_config CONFIG_MT76_LEDS m
	    set_kernel_config CONFIG_MT76_USB m
	    set_kernel_config CONFIG_MT76x2_COMMON m
	    set_kernel_config CONFIG_MT76x0U m
	    set_kernel_config CONFIG_MT76x2U m
	    set_kernel_config CONFIG_TOUCHSCREEN_ILI210X m
	    set_kernel_config CONFIG_BCM_VC_SM m
	    set_kernel_config CONFIG_BCM2835_SMI_DEV m
	    set_kernel_config CONFIG_RPIVID_MEM m
	    set_kernel_config CONFIG_HW_RANDOM_BCM2835 y
	    set_kernel_config CONFIG_TCG_TPM m
	    set_kernel_config CONFIG_HW_RANDOM_TPM y
	    set_kernel_config CONFIG_TCG_TIS m
	    set_kernel_config CONFIG_TCG_TIS_SPI m
	    set_kernel_config CONFIG_I2C_MUX m
	    set_kernel_config CONFIG_I2C_MUX_GPMUX m
	    set_kernel_config CONFIG_I2C_MUX_PCA954x m
	    set_kernel_config CONFIG_SPI_GPIO m
	    set_kernel_config CONFIG_BATTERY_MAX17040 m
	    set_kernel_config CONFIG_SENSORS_GPIO_FAN m
	    set_kernel_config CONFIG_SENSORS_RASPBERRYPI_HWMON m
	    set_kernel_config CONFIG_BCM2835_THERMAL y
	    set_kernel_config CONFIG_RC_CORE y
	    set_kernel_config CONFIG_RC_MAP y
	    set_kernel_config CONFIG_LIRC y
	    set_kernel_config CONFIG_RC_DECODERS y
	    set_kernel_config CONFIG_IR_NEC_DECODER m
	    set_kernel_config CONFIG_IR_RC5_DECODER m
	    set_kernel_config CONFIG_IR_RC6_DECODER m
	    set_kernel_config CONFIG_IR_JVC_DECODER m
	    set_kernel_config CONFIG_IR_SONY_DECODER m
	    set_kernel_config CONFIG_IR_SANYO_DECODER m
	    set_kernel_config CONFIG_IR_SHARP_DECODER m
	    set_kernel_config CONFIG_IR_MCE_KBD_DECODER m
	    set_kernel_config CONFIG_IR_XMP_DECODER m
	    set_kernel_config CONFIG_IR_IMON_DECODER m
	    set_kernel_config CONFIG_RC_DEVICES y
	    set_kernel_config CONFIG_RC_ATI_REMOTE m
	    set_kernel_config CONFIG_IR_IMON m
	    set_kernel_config CONFIG_IR_MCEUSB m
	    set_kernel_config CONFIG_IR_REDRAT3 m
	    set_kernel_config CONFIG_IR_STREAMZAP m
	    set_kernel_config CONFIG_IR_IGUANA m
	    set_kernel_config CONFIG_IR_TTUSBIR m
	    set_kernel_config CONFIG_RC_LOOPBACK m
	    set_kernel_config CONFIG_IR_GPIO_CIR m
	    set_kernel_config CONFIG_IR_GPIO_TX m
	    set_kernel_config CONFIG_IR_PWM_TX m
	    set_kernel_config CONFIG_VIDEO_V4L2_SUBDEV_API y
	    set_kernel_config CONFIG_VIDEO_AU0828_RC y
	    set_kernel_config CONFIG_VIDEO_CX231XX m
	    set_kernel_config CONFIG_VIDEO_CX231XX_RC y
	    set_kernel_config CONFIG_VIDEO_CX231XX_ALSA m
	    set_kernel_config CONFIG_VIDEO_CX231XX_DVB m
	    set_kernel_config CONFIG_VIDEO_TM6000 m
	    set_kernel_config CONFIG_VIDEO_TM6000_ALSA m
	    set_kernel_config CONFIG_VIDEO_TM6000_DVB m
	    set_kernel_config CONFIG_DVB_USB m
	    set_kernel_config CONFIG_DVB_USB_DIB3000MC m
	    set_kernel_config CONFIG_DVB_USB_A800 m
	    set_kernel_config CONFIG_DVB_USB_DIBUSB_MB m
	    set_kernel_config CONFIG_DVB_USB_DIBUSB_MB_FAULTY y
	    set_kernel_config CONFIG_DVB_USB_DIBUSB_MC m
	    set_kernel_config CONFIG_DVB_USB_DIB0700 m
	    set_kernel_config CONFIG_DVB_USB_UMT_010 m
	    set_kernel_config CONFIG_DVB_USB_CXUSB m
	    set_kernel_config CONFIG_DVB_USB_M920X m
	    set_kernel_config CONFIG_DVB_USB_DIGITV m
	    set_kernel_config CONFIG_DVB_USB_VP7045 m
	    set_kernel_config CONFIG_DVB_USB_VP702X m
	    set_kernel_config CONFIG_DVB_USB_GP8PSK m
	    set_kernel_config CONFIG_DVB_USB_NOVA_T_USB2 m
	    set_kernel_config CONFIG_DVB_USB_TTUSB2 m
	    set_kernel_config CONFIG_DVB_USB_DTT200U m
	    set_kernel_config CONFIG_DVB_USB_OPERA1 m
	    set_kernel_config CONFIG_DVB_USB_AF9005 m
	    set_kernel_config CONFIG_DVB_USB_AF9005_REMOTE m
	    set_kernel_config CONFIG_DVB_USB_PCTV452E m
	    set_kernel_config CONFIG_DVB_USB_DW2102 m
	    set_kernel_config CONFIG_DVB_USB_CINERGY_T2 m
	    set_kernel_config CONFIG_DVB_USB_DTV5100 m
	    set_kernel_config CONFIG_DVB_USB_AZ6027 m
	    set_kernel_config CONFIG_DVB_USB_TECHNISAT_USB2 m
	    set_kernel_config CONFIG_DVB_USB_AF9015 m
	    set_kernel_config CONFIG_DVB_USB_LME2510 m
	    set_kernel_config CONFIG_DVB_USB_RTL28XXU m
	    set_kernel_config CONFIG_VIDEO_EM28XX_RC m
	    set_kernel_config CONFIG_SMS_SIANO_RC m
	    set_kernel_config CONFIG_VIDEO_IR_I2C m
	    set_kernel_config CONFIG_VIDEO_ADV7180 m
	    set_kernel_config CONFIG_VIDEO_TC358743 m
	    set_kernel_config CONFIG_VIDEO_OV5647 m
	    set_kernel_config CONFIG_DVB_M88DS3103 m
	    set_kernel_config CONFIG_DVB_AF9013 m
	    set_kernel_config CONFIG_DVB_RTL2830 m
	    set_kernel_config CONFIG_DVB_RTL2832 m
	    set_kernel_config CONFIG_DVB_SI2168 m
	    set_kernel_config CONFIG_DVB_GP8PSK_FE m
	    set_kernel_config CONFIG_DVB_USB m
	    set_kernel_config CONFIG_DVB_LGDT3306A m
	    set_kernel_config CONFIG_FB_SIMPLE y
	    set_kernel_config CONFIG_SND_BCM2708_SOC_IQAUDIO_CODEC m
	    set_kernel_config CONFIG_SND_BCM2708_SOC_I_SABRE_Q2M m
	    set_kernel_config CONFIG_SND_AUDIOSENSE_PI m
	    set_kernel_config CONFIG_SND_SOC_AD193X m
	    set_kernel_config CONFIG_SND_SOC_AD193X_SPI m
	    set_kernel_config CONFIG_SND_SOC_AD193X_I2C m
	    set_kernel_config CONFIG_SND_SOC_CS4265 m
	    set_kernel_config CONFIG_SND_SOC_DA7213 m
	    set_kernel_config CONFIG_SND_SOC_ICS43432 m
	    set_kernel_config CONFIG_SND_SOC_TLV320AIC32X4 m
	    set_kernel_config CONFIG_SND_SOC_TLV320AIC32X4_I2C m
	    set_kernel_config CONFIG_SND_SOC_I_SABRE_CODEC m
	    set_kernel_config CONFIG_HID_BIGBEN_FF m
	    #set_kernel_config CONFIG_USB_XHCI_PLATFORM y
	    set_kernel_config CONFIG_USB_TMC m
	    set_kernel_config CONFIG_USB_UAS y
	    set_kernel_config CONFIG_USBIP_VUDC m
	    set_kernel_config CONFIG_USB_CONFIGFS m
	    set_kernel_config CONFIG_USB_CONFIGFS_SERIAL y
	    set_kernel_config CONFIG_USB_CONFIGFS_ACM y
	    set_kernel_config CONFIG_USB_CONFIGFS_OBEX y
	    set_kernel_config CONFIG_USB_CONFIGFS_NCM y
	    set_kernel_config CONFIG_USB_CONFIGFS_ECM y
	    set_kernel_config CONFIG_USB_CONFIGFS_ECM_SUBSET y
	    set_kernel_config CONFIG_USB_CONFIGFS_RNDIS y
	    set_kernel_config CONFIG_USB_CONFIGFS_EEM y
	    set_kernel_config CONFIG_USB_CONFIGFS_MASS_STORAGE y
	    set_kernel_config CONFIG_USB_CONFIGFS_F_LB_SS y
	    set_kernel_config CONFIG_USB_CONFIGFS_F_FS y
	    set_kernel_config CONFIG_USB_CONFIGFS_F_UAC1 y
	    set_kernel_config CONFIG_USB_CONFIGFS_F_UAC2 y
	    set_kernel_config CONFIG_USB_CONFIGFS_F_MIDI y
	    set_kernel_config CONFIG_USB_CONFIGFS_F_HID y
	    set_kernel_config CONFIG_USB_CONFIGFS_F_UVC y
	    set_kernel_config CONFIG_USB_CONFIGFS_F_PRINTER y
	    set_kernel_config CONFIG_LEDS_PCA963X m
	    set_kernel_config CONFIG_LEDS_IS31FL32XX m
	    set_kernel_config CONFIG_LEDS_TRIGGER_NETDEV m
	    set_kernel_config CONFIG_RTC_DRV_RV3028 m
	    set_kernel_config CONFIG_AUXDISPLAY y
	    set_kernel_config CONFIG_HD44780 m
	    set_kernel_config CONFIG_FB_TFT_SH1106 m
	    set_kernel_config CONFIG_VIDEO_CODEC_BCM2835 m
	    set_kernel_config CONFIG_BCM2835_POWER y
	    set_kernel_config CONFIG_INV_MPU6050_IIO m
	    set_kernel_config CONFIG_INV_MPU6050_I2C m
	    set_kernel_config CONFIG_SECURITYFS y

	    # Safer to build this in
	    set_kernel_config CONFIG_BINFMT_MISC y

	    # pulseaudio wants a buffer of at least this size
	    set_kernel_config CONFIG_SND_HDA_PREALLOC_SIZE 2048

	    # PR#3063: enable 3D acceleration with 64-bit kernel on RPi4
	    # set the appropriate kernel configs unlocked by this PR
	    set_kernel_config CONFIG_ARCH_BCM y
	    set_kernel_config CONFIG_ARCH_BCM2835 y
	    set_kernel_config CONFIG_DRM_V3D m
	    set_kernel_config CONFIG_DRM_VC4 m
	    set_kernel_config CONFIG_DRM_VC4_HDMI_CEC y

	    # PR#3144: add arm64 pcie bounce buffers; enables 4GiB on RPi4
	    # required by PR#3144; should already be applied, but just to be safe
	    set_kernel_config CONFIG_PCIE_BRCMSTB y
	    set_kernel_config CONFIG_BCM2835_MMC y

	    # Snap needs squashfs. The ubuntu eoan-preinstalled-server image at 
	    # http://cdimage.ubuntu.com/ubuntu-server/daily-preinstalled/current/ uses snap
	    # during cloud-init setup at first boot. Without this the login accounts are not
	    # created and the user can not login.
	    set_kernel_config CONFIG_SQUASHFS y

	    # Ceph support for Block Device (RBD) and Filesystem (FS)
	    # https://docs.ceph.com/docs/master/
	    set_kernel_config CONFIG_CEPH_LIB m
	    set_kernel_config CONFIG_CEPH_LIB_USE_DNS_RESOLVER y
	    set_kernel_config CONFIG_CEPH_FS m
	    set_kernel_config CONFIG_CEPH_FSCACHE y
	    set_kernel_config CONFIG_CEPH_FS_POSIX_ACL y
	    set_kernel_config CONFIG_BLK_DEV_RBD m
	  fi

      # enable basic KVM support; see https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=210546&start=25#p1300453
	  if [ "$KERNEL_VIRT" = true ] && { [ "$RPI_MODEL" = 2 ] || [ "$RPI_MODEL" = 3 ] || [ "$RPI_MODEL" = 3P ] || [ "$RPI_MODEL" = 4 ]; } ; then
		set_kernel_config CONFIG_HAVE_KVM y
		set_kernel_config CONFIG_HIGH_RES_TIMERS y
		set_kernel_config CONFIG_HAVE_KVM_IRQCHIP y
        set_kernel_config CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL y
        set_kernel_config CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT y
        set_kernel_config CONFIG_HAVE_KVM_EVENTFD y
        set_kernel_config CONFIG_HAVE_KVM_IRQFD y
        set_kernel_config CONFIG_HAVE_KVM_IRQ_ROUTING y
        set_kernel_config CONFIG_HAVE_KVM_MSI y
        set_kernel_config CONFIG_KVM y
        set_kernel_config CONFIG_KVM_ARM_HOST y
        set_kernel_config CONFIG_KVM_ARM_PMU y
        set_kernel_config CONFIG_KVM_COMPAT y
        set_kernel_config CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT y
        set_kernel_config CONFIG_KVM_MMIO y
        set_kernel_config CONFIG_KVM_VFIO y
		set_kernel_config CONFIG_KVM_MMU_AUDIT y
        set_kernel_config CONFIG_VHOST m
        set_kernel_config CONFIG_VHOST_CROSS_ENDIAN_LEGACY y
        set_kernel_config CONFIG_VHOST_NET m
        set_kernel_config CONFIG_VIRTUALIZATION y
		set_kernel_config CONFIG_SLAB_FREELIST_RANDOM=y
		set_kernel_config CONFIG_SLAB_FREELIST_HARDENED=y
		set_kernel_config CONFIG_MMU_NOTIFIER y
		
		# erratum
		set_kernel_config ARM64_ERRATUM_834220 y
		
		# https://sourceforge.net/p/kvm/mailman/message/18440797/
		set_kernel_config CONFIG_PREEMPT_NOTIFIERS y
	  fi

      # enable apparmor,integrity audit,
	  if [ "$KERNEL_SECURITY" = true ] ; then

        # security filesystem, security models and audit
        set_kernel_config CONFIG_SECURITYFS y
        set_kernel_config CONFIG_SECURITY y
        set_kernel_config CONFIG_AUDIT y

        # harden strcpy and memcpy
        set_kernel_config CONFIG_HARDENED_USERCOPY y
        set_kernel_config CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR y
        set_kernel_config CONFIG_FORTIFY_SOURCE y

        # integrity sub-system
        set_kernel_config CONFIG_INTEGRITY y
        set_kernel_config CONFIG_INTEGRITY_ASYMMETRIC_KEYS y
        set_kernel_config CONFIG_INTEGRITY_AUDIT y
        set_kernel_config CONFIG_INTEGRITY_SIGNATURE y
        set_kernel_config CONFIG_INTEGRITY_TRUSTED_KEYRING y

        # This option provides support for retaining authentication tokens and access keys in the kernel.
        set_kernel_config CONFIG_KEYS y
        set_kernel_config CONFIG_KEYS_COMPAT y

        # Apparmor
        set_kernel_config CONFIG_SECURITY_APPARMOR_BOOTPARAM_VALUE 0
        set_kernel_config CONFIG_SECURITY_APPARMOR_HASH_DEFAULT y
        set_kernel_config CONFIG_DEFAULT_SECURITY_APPARMOR y
        set_kernel_config CONFIG_SECURITY_APPARMOR y
        set_kernel_config CONFIG_SECURITY_APPARMOR_HASH y
        set_kernel_config CONFIG_DEFAULT_SECURITY "apparmor"

        # restrictions on unprivileged users reading the kernel
        set_kernel_config CONFIG_SECURITY_DMESG_RESTRICT y

        # network security hooks
        set_kernel_config CONFIG_SECURITY_NETWORK y
        set_kernel_config CONFIG_SECURITY_NETWORK_XFRM y
        set_kernel_config CONFIG_SECURITY_PATH y
        set_kernel_config CONFIG_SECURITY_YAMA n

        set_kernel_config CONFIG_SECURITY_SELINUX n
        set_kernel_config CONFIG_SECURITY_SMACK n
        set_kernel_config CONFIG_SECURITY_TOMOYO n
        set_kernel_config CONFIG_SECURITY_APPARMOR_DEBUG n
        set_kernel_config CONFIG_SECURITY_LOADPIN n
        set_kernel_config CONFIG_HARDENED_USERCOPY_PAGESPAN n
        set_kernel_config CONFIG_IMA n
        set_kernel_config CONFIG_EVM n
        set_kernel_config CONFIG_FANOTIFY_ACCESS_PERMISSIONS y
        set_kernel_config CONFIG_NFSD_V4_SECURITY_LABEL y
        set_kernel_config CONFIG_PKCS7_MESSAGE_PARSER y
        set_kernel_config CONFIG_SYSTEM_TRUSTED_KEYRING y
        set_kernel_config CONFIG_SYSTEM_EXTRA_CERTIFICATE y
        set_kernel_config CONFIG_SECONDARY_TRUSTED_KEYRING y
        set_kernel_config CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY n
		set_kernel_config CONFIG_SYSTEM_TRUSTED_KEYS m
		set_kernel_config CONFIG_SYSTEM_EXTRA_CERTIFICATE_SIZE 4096
      fi
	  
	  if [ "$ENABLE_CRYPTFS" = true ] ; then
		set_kernel_config CONFIG_EMBEDDED y
		set_kernel_config CONFIG_EXPERT y
		set_kernel_config CONFIG_DAX y
		set_kernel_config CONFIG_MD y
		set_kernel_config CONFIG_BLK_DEV_MD y
		set_kernel_config CONFIG_MD_AUTODETECT y
		set_kernel_config CONFIG_BLK_DEV_DM y
		set_kernel_config CONFIG_BLK_DEV_DM_BUILTIN y
		set_kernel_config CONFIG_DM_CRYPT y
		set_kernel_config CONFIG_CRYPTO_BLKCIPHER y
		set_kernel_config CONFIG_CRYPTO_CBC y
		set_kernel_config CONFIG_CRYPTO_XTS y
		set_kernel_config CONFIG_CRYPTO_SHA512 y
		set_kernel_config CONFIG_CRYPTO_MANAGER y
		set_kernel_config CONFIG_ARM64_CRYPTO y
        set_kernel_config CONFIG_CRYPTO_SHA256_ARM64 m
        set_kernel_config CONFIG_CRYPTO_SHA512_ARM64 m
        set_kernel_config CONFIG_CRYPTO_SHA1_ARM64_CE m
        set_kernel_config CRYPTO_GHASH_ARM64_CE m
        set_kernel_config CRYPTO_SHA2_ARM64_CE m
        set_kernel_config CONFIG_CRYPTO_CRCT10DIF_ARM64_CE m
        set_kernel_config CONFIG_CRYPTO_CRC32_ARM64_CE m
        set_kernel_config CONFIG_CRYPTO_AES_ARM64 m
        set_kernel_config CONFIG_CRYPTO_AES_ARM64_CE m
        set_kernel_config CONFIG_CRYPTO_AES_ARM64_CE_CCM y
        set_kernel_config CONFIG_CRYPTO_AES_ARM64_CE_BLK y
        set_kernel_config CONFIG_CRYPTO_AES_ARM64_NEON_BLK m
        set_kernel_config CONFIG_CRYPTO_CHACHA20_NEON m
        set_kernel_config CONFIG_CRYPTO_AES_ARM64_BS m
      fi

      # Netfilter kernel support See https://github.com/raspberrypi/linux/issues/2177#issuecomment-354647406
      if [ "$KERNEL_NF" = true ] ; then
	    set_kernel_config CONFIG_IP_NF_SECURITY m
        set_kernel_config CONFIG_NETLABEL y
        set_kernel_config CONFIG_IP6_NF_SECURITY m
        set_kernel_config CONFIG_IP_NF_TARGET_SYNPROXY m
        set_kernel_config CONFIG_NETFILTER_XT_TARGET_AUDIT m
        set_kernel_config CONFIG_NETFILTER_XT_MATCH_CGROUP m
        set_kernel_config CONFIG_NETFILTER_XT_MATCH_IPCOMP m
        set_kernel_config CONFIG_NETFILTER_XT_MATCH_SOCKET m
        set_kernel_config CONFIG_NFT_FIB_INET m
        set_kernel_config CONFIG_NFT_FIB_IPV4 m
        set_kernel_config CONFIG_NFT_FIB_IPV6 m
        set_kernel_config CONFIG_NFT_FIB_NETDEV m
        set_kernel_config CONFIG_NFT_OBJREF m
        set_kernel_config CONFIG_NFT_RT m
        set_kernel_config CONFIG_NFT_SET_BITMAP m
        set_kernel_config CONFIG_NF_CONNTRACK_TIMEOUT y
        set_kernel_config CONFIG_NF_LOG_ARP m
        set_kernel_config CONFIG_NF_SOCKET_IPV4 m
        set_kernel_config CONFIG_NF_SOCKET_IPV6 m
        set_kernel_config CONFIG_BRIDGE_EBT_BROUTE m
        set_kernel_config CONFIG_BRIDGE_EBT_T_FILTER m
        set_kernel_config CONFIG_BRIDGE_NF_EBTABLES m
        set_kernel_config CONFIG_IP6_NF_IPTABLES m
        set_kernel_config CONFIG_IP6_NF_MATCH_AH m
        set_kernel_config CONFIG_IP6_NF_MATCH_EUI64 m
        set_kernel_config CONFIG_IP6_NF_NAT m
        set_kernel_config CONFIG_IP6_NF_TARGET_MASQUERADE m
        set_kernel_config CONFIG_IP6_NF_TARGET_NPT m
        set_kernel_config CONFIG_IP_SET_BITMAP_IPMAC m
        set_kernel_config CONFIG_IP_SET_BITMAP_PORT m
        set_kernel_config CONFIG_IP_SET_HASH_IP m
        set_kernel_config CONFIG_IP_SET_HASH_IPMARK m
        set_kernel_config CONFIG_IP_SET_HASH_IPPORT m
        set_kernel_config CONFIG_IP_SET_HASH_IPPORTIP m
        set_kernel_config CONFIG_IP_SET_HASH_IPPORTNET m
        set_kernel_config CONFIG_IP_SET_HASH_MAC m
        set_kernel_config CONFIG_IP_SET_HASH_NET m
        set_kernel_config CONFIG_IP_SET_HASH_NETIFACE m
        set_kernel_config CONFIG_IP_SET_HASH_NETNET m
        set_kernel_config CONFIG_IP_SET_HASH_NETPORT m
        set_kernel_config CONFIG_IP_SET_HASH_NETPORTNET m
        set_kernel_config CONFIG_IP_SET_LIST_SET m
        set_kernel_config CONFIG_NETFILTER_XTABLES m
        set_kernel_config CONFIG_NETFILTER_XTABLES m
        set_kernel_config CONFIG_NFT_BRIDGE_META m
        set_kernel_config CONFIG_NFT_BRIDGE_REJECT m
        set_kernel_config CONFIG_NFT_CHAIN_NAT_IPV4 m
        set_kernel_config CONFIG_NFT_CHAIN_NAT_IPV6 m
        set_kernel_config CONFIG_NFT_CHAIN_ROUTE_IPV4 m
        set_kernel_config CONFIG_NFT_CHAIN_ROUTE_IPV6 m
        set_kernel_config CONFIG_NFT_COMPAT m
        set_kernel_config CONFIG_NFT_COUNTER m
        set_kernel_config CONFIG_NFT_CT m
        set_kernel_config CONFIG_NFT_DUP_IPV4 m
        set_kernel_config CONFIG_NFT_DUP_IPV6 m
        set_kernel_config CONFIG_NFT_DUP_NETDEV m
        set_kernel_config CONFIG_NFT_EXTHDR m
        set_kernel_config CONFIG_NFT_FWD_NETDEV m
        set_kernel_config CONFIG_NFT_HASH m
        set_kernel_config CONFIG_NFT_LIMIT m
        set_kernel_config CONFIG_NFT_LOG m
        set_kernel_config CONFIG_NFT_MASQ m
        set_kernel_config CONFIG_NFT_MASQ_IPV4 m
        set_kernel_config CONFIG_NFT_MASQ_IPV6 m
        set_kernel_config CONFIG_NFT_META m
        set_kernel_config CONFIG_NFT_NAT m
        set_kernel_config CONFIG_NFT_NUMGEN m
        set_kernel_config CONFIG_NFT_QUEUE m
        set_kernel_config CONFIG_NFT_QUOTA m
        set_kernel_config CONFIG_NFT_REDIR m
        set_kernel_config CONFIG_NFT_REDIR_IPV4 m
        set_kernel_config CONFIG_NFT_REDIR_IPV6 m
        set_kernel_config CONFIG_NFT_REJECT m
        set_kernel_config CONFIG_NFT_REJECT_INET m
        set_kernel_config CONFIG_NFT_REJECT_IPV4 m
        set_kernel_config CONFIG_NFT_REJECT_IPV6 m
        set_kernel_config CONFIG_NFT_SET_HASH m
        set_kernel_config CONFIG_NFT_SET_RBTREE m
        set_kernel_config CONFIG_NF_CONNTRACK_IPV4 m
        set_kernel_config CONFIG_NF_CONNTRACK_IPV6 m
        set_kernel_config CONFIG_NF_DEFRAG_IPV4 m
        set_kernel_config CONFIG_NF_DEFRAG_IPV6 m
        set_kernel_config CONFIG_NF_DUP_IPV4 m
        set_kernel_config CONFIG_NF_DUP_IPV6 m
        set_kernel_config CONFIG_NF_DUP_NETDEV m
        set_kernel_config CONFIG_NF_LOG_BRIDGE m
        set_kernel_config CONFIG_NF_LOG_IPV4 m
        set_kernel_config CONFIG_NF_LOG_IPV6 m
        set_kernel_config CONFIG_NF_NAT_IPV4 m
        set_kernel_config CONFIG_NF_NAT_IPV6 m
        set_kernel_config CONFIG_NF_NAT_MASQUERADE_IPV4 y
        set_kernel_config CONFIG_NF_NAT_MASQUERADE_IPV6 y
        set_kernel_config CONFIG_NF_NAT_PPTP m
        set_kernel_config CONFIG_NF_NAT_PROTO_GRE m
        set_kernel_config CONFIG_NF_NAT_REDIRECT y
        set_kernel_config CONFIG_NF_NAT_SIP m
        set_kernel_config CONFIG_NF_NAT_SNMP_BASIC m
        set_kernel_config CONFIG_NF_NAT_TFTP m
        set_kernel_config CONFIG_NF_REJECT_IPV4 m
        set_kernel_config CONFIG_NF_REJECT_IPV6 m
        set_kernel_config CONFIG_NF_TABLES m
        set_kernel_config CONFIG_NF_TABLES_IPV4 y
        set_kernel_config CONFIG_NF_TABLES_IPV6 y
        set_kernel_config CONFIG_NF_TABLES_SET m
        set_kernel_config CONFIG_NF_TABLES_INET y
        set_kernel_config CONFIG_NF_TABLES_NETDEV y
        set_kernel_config CONFIG_NFT_CONNLIMIT m
        set_kernel_config CONFIG_NFT_TUNNEL m
        set_kernel_config CONFIG_NFT_SOCKET m
        set_kernel_config CONFIG_NFT_TPROXY m
        set_kernel_config CONFIG_NF_FLOW_TABLE m
        set_kernel_config CONFIG_NFT_FLOW_OFFLOAD m
        set_kernel_config CONFIG_NF_FLOW_TABLE_INET m
        set_kernel_config CONFIG_NF_TABLES_ARP y
        set_kernel_config CONFIG_NF_FLOW_TABLE_IPV4 y
        set_kernel_config CONFIG_NF_FLOW_TABLE_IPV6 y
        set_kernel_config CONFIG_NF_TABLES_BRIDGE y
        set_kernel_config CONFIG_NF_CT_NETLINK_TIMEOUT m
        set_kernel_config CONFIG_NFT_OSF m
	
      fi

	  # Enables BPF syscall for systemd-journald see https://github.com/torvalds/linux/blob/master/init/Kconfig#L848 or https://groups.google.com/forum/#!topic/linux.gentoo.user/_2aSc_ztGpA
	  if [ "$KERNEL_BPF" = true ] ; then
        set_kernel_config CONFIG_BPF_SYSCALL y
	    set_kernel_config CONFIG_BPF_EVENTS y
	    set_kernel_config CONFIG_BPF_STREAM_PARSER y
	    set_kernel_config CONFIG_CGROUP_BPF y
	    set_kernel_config CONFIG_XDP_SOCKETS y
	  fi

	  # KERNEL_DEFAULT_GOV was set by user 
	  if [ "$KERNEL_DEFAULT_GOV" != ondemand ] && [ -n "$KERNEL_DEFAULT_GOV" ] ; then
	    case "$KERNEL_DEFAULT_GOV" in
          performance)
	            set_kernel_config CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE y
            ;;
          userspace)
            	    set_kernel_config CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE y
            ;;
          ondemand)
		    set_kernel_config CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND y
            ;;
          conservative)
		    set_kernel_config CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE y
		    ;;
          shedutil)
		    set_kernel_config CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL y
            ;;
          *)
            echo "error: unsupported default cpu governor"
            exit 1
            ;;
        esac
        # unset previous default governor
	    unset_kernel_config CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
	  fi

	  #Revert to previous directory
	  cd "${WORKDIR}" || exit

      # Set kernel configuration parameters to enable qemu emulation
      if [ "$ENABLE_QEMU" = true ] ; then
        echo "CONFIG_FHANDLE=y" >> "${KERNEL_DIR}"/.config
        echo "CONFIG_LBDAF=y" >> "${KERNEL_DIR}"/.config
      fi

      # Copy custom kernel configuration file
      if [ -n "$KERNELSRC_USRCONFIG" ] ; then
        cp "$KERNELSRC_USRCONFIG" "${KERNEL_DIR}"/.config
      fi

      # Set kernel configuration parameters to their default values
      if [ "$KERNEL_OLDDEFCONFIG" = true ] ; then
        make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" olddefconfig
      fi

      # Start menu-driven kernel configuration (interactive)
      if [ "$KERNEL_MENUCONFIG" = true ] ; then
        make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" menuconfig
      fi
	# end if "$KERNELSRC_CONFIG" = true
    fi

    # Use ccache to cross compile the kernel
    if [ "$KERNEL_CCACHE" = true ] ; then
      cc="ccache ${CROSS_COMPILE}gcc"
    else
      cc="${CROSS_COMPILE}gcc"
    fi

    # Cross compile kernel and dtbs
    make -j "${NB_CORES}" -C "${KERNEL_DIR}" -j"${KERNEL_THREADS}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" CC="${cc}" "${KERNEL_BIN_IMAGE}" dtbs

    # Cross compile kernel modules
    if grep -q "CONFIG_MODULES=y" "${KERNEL_DIR}/.config" ; then
      make -j "${NB_CORES}" -C "${KERNEL_DIR}" -j"${KERNEL_THREADS}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" CC="${cc}" modules
    fi
  # end if "$KERNELSRC_PREBUILT" = false
  fi

  # Check if kernel compilation was successful
  if [ ! -r "${KERNEL_DIR}/arch/${KERNEL_ARCH}/boot/${KERNEL_BIN_IMAGE}" ] ; then
    echo "error: kernel compilation failed! (kernel image not found)"
    cleanup
    exit 1
  fi

  # Install kernel modules
  if [ "$ENABLE_REDUCE" = true ] ; then
    if grep -q "CONFIG_MODULES=y" "${KERNEL_DIR}/.config" ; then
      make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" INSTALL_MOD_STRIP=1 INSTALL_MOD_PATH=../../.. modules_install
    fi
  else
    if grep -q "CONFIG_MODULES=y" "${KERNEL_DIR}/.config" ; then
      make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" INSTALL_MOD_PATH=../../.. modules_install
    fi

    # Install kernel firmware
    if grep -q "^firmware_install:" "${KERNEL_DIR}/Makefile" ; then
      make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" INSTALL_FW_PATH=../../../lib firmware_install
    fi
  fi

  # Install kernel headers
  if [ "$KERNEL_HEADERS" = true ] && [ "$REDUCE_KERNEL" = false ] ; then
    make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" INSTALL_HDR_PATH=../.. headers_install
  fi

  # Prepare boot (firmware) directory
  mkdir "${BOOT_DIR}"

  # Get kernel release version
  KERNEL_VERSION=$(cat "${KERNEL_DIR}/include/config/kernel.release")

  # Copy kernel configuration file to the boot directory
  install_readonly "${KERNEL_DIR}/.config" "${R}/boot/config-${KERNEL_VERSION}"

  # Prepare device tree directory
  mkdir "${BOOT_DIR}/overlays"

  # Ensure the proper .dtb is located
  if [ "$KERNEL_ARCH" = "arm" ] ; then
    for dtb in "${KERNEL_DIR}/arch/${KERNEL_ARCH}/boot/dts/"*.dtb ; do
      if [ -f "${dtb}" ] ; then
        install_readonly "${dtb}" "${BOOT_DIR}/"
      fi
    done
  else
    for dtb in "${KERNEL_DIR}/arch/${KERNEL_ARCH}/boot/dts/broadcom/"*.dtb ; do
      if [ -f "${dtb}" ] ; then
        install_readonly "${dtb}" "${BOOT_DIR}/"
      fi
    done
  fi

  # Copy compiled dtb device tree files
  if [ -d "${KERNEL_DIR}/arch/${KERNEL_ARCH}/boot/dts/overlays" ] ; then
    for dtb in "${KERNEL_DIR}/arch/${KERNEL_ARCH}/boot/dts/overlays/"*.dtbo ; do
      if [ -f "${dtb}" ] ; then
        install_readonly "${dtb}" "${BOOT_DIR}/overlays/"
      fi
    done

    if [ -f "${KERNEL_DIR}/arch/${KERNEL_ARCH}/boot/dts/overlays/README" ] ; then
      install_readonly "${KERNEL_DIR}/arch/${KERNEL_ARCH}/boot/dts/overlays/README" "${BOOT_DIR}/overlays/README"
    fi
  fi

  if [ "$ENABLE_UBOOT" = false ] ; then
    # Convert and copy kernel image to the boot directory
    cp "${KERNEL_DIR}/arch/${KERNEL_ARCH}/boot/${KERNEL_BIN_IMAGE}" "${BOOT_DIR}/${KERNEL_IMAGE}"
  else
    # Copy kernel image to the boot directory
    install_readonly "${KERNEL_DIR}/arch/${KERNEL_ARCH}/boot/${KERNEL_BIN_IMAGE}" "${BOOT_DIR}/${KERNEL_IMAGE}"
  fi

  # Remove kernel sources
  if [ "$KERNEL_REMOVESRC" = true ] ; then
    rm -fr "${KERNEL_DIR}"
  else
    # Prepare compiled kernel modules
    if grep -q "CONFIG_MODULES=y" "${KERNEL_DIR}/.config" ; then
      if grep -q "^modules_prepare:" "${KERNEL_DIR}/Makefile" ; then
        make -j "${NB_CORES}" -C "${KERNEL_DIR}" ARCH="${KERNEL_ARCH}" CROSS_COMPILE="${CROSS_COMPILE}" modules_prepare
      fi

      # Create symlinks for kernel modules
      chroot_exec ln -sf /usr/src/linux "/lib/modules/${KERNEL_VERSION}/build"
      chroot_exec ln -sf /usr/src/linux "/lib/modules/${KERNEL_VERSION}/source"
    fi
  fi
  ;;

"download")
else # BUILD_KERNEL=false
  if [ "$SET_ARCH" = 64 ] ; then
    if [ "$RPI_MODEL" = 3 ] || [ "$RPI_MODEL" = 3P ] ; then
	  # Use Sakakis modified kernel if ZSWAP is active
      if [ "$KERNEL_ZSWAP" = true ] || [ "$KERNEL_VIRT" = true ] || [ "$KERNEL_NF" = true ] || [ "$KERNEL_BPF" = true ] ; then
	    RPI3_64_KERNEL_URL="${RPI3_64_BIS_KERNEL_URL}"
	  fi

      # Create temporary directory for dl
      temp_dir=$(as_nobody mktemp -d)

      # Fetch kernel dl
      as_nobody wget -O "${temp_dir}"/kernel.tar.xz -c "$RPI3_64_KERNEL_URL" 
    fi
    if [ "$SET_ARCH" = 64 ] && [ "$RPI_MODEL" = 4 ] ; then
      # Create temporary directory for dl
      temp_dir=$(as_nobody mktemp -d)

      # Fetch kernel dl
      as_nobody wget -O "${temp_dir}"/kernel.tar.xz -c "$RPI4_64_KERNEL_URL" 
    fi
	
	#extract download
    tar -xJf "${temp_dir}"/kernel.tar.xz -C "${temp_dir}"

    #move extracted kernel to /boot/firmware
    mkdir "${R}/boot/firmware"
    cp "${temp_dir}"/boot/* "${R}"/boot/firmware/
    cp -r "${temp_dir}"/lib/* "${R}"/lib/

    # Remove temporary directory for kernel sources
    rm -fr "${temp_dir}"

    # Set permissions of the kernel sources
    chown -R root:root "${R}/boot/firmware"
    chown -R root:root "${R}/lib/modules"
  fi

  # Install Kernel from hypriot comptabile with all Raspberry PI (dunno if its compatible with RPI4 - better compile your own kernel)
  if [ "$SET_ARCH" = 32 ] && [ "$RPI_MODEL" != 4 ] ; then
    # Create temporary directory for dl
    temp_dir=$(as_nobody mktemp -d)

    # Fetch kernel
    as_nobody wget -O "${temp_dir}"/kernel.deb -c "$RPI_32_KERNEL_URL"

    # Copy downloaded kernel package
    mv "${temp_dir}"/kernel.deb "${R}"/tmp/kernel.deb

    # Set permissions
    chown -R root:root "${R}"/tmp/kernel.deb

	# Install kernel
	chroot_exec dpkg -i /tmp/kernel.deb

	# move /boot to /boot/firmware to fit script env.
	#mkdir "${BOOT_DIR}"
	mkdir "${temp_dir}"/firmware
	mv  "${R}"/boot/* "${temp_dir}"/firmware/
	mv "${temp_dir}"/firmware "${R}"/boot/

	#same for kernel headers
	if [ "$KERNEL_HEADERS" = true ] ; then
	  # Fetch kernel header
	  as_nobody wget -O "${temp_dir}"/kernel-header.deb -c "$RPI_32_KERNELHEADER_URL"
	  mv "${temp_dir}"/kernel-header.deb "${R}"/tmp/kernel-header.deb
	  chown -R root:root "${R}"/tmp/kernel-header.deb
	  # Install kernel header
	  chroot_exec dpkg -i /tmp/kernel-header.deb
	  rm -f "${R}"/tmp/kernel-header.deb
	fi

    # Remove temporary directory and files
    rm -fr "${temp_dir}"
	rm -f "${R}"/tmp/kernel.deb
  fi
fi
  ;;

"uselocal")
  echo "using local kernel previous run"
  ;;
  
esac

# Check if kernel installation was successful
KERNEL="$(ls -1 "${R}"/boot/firmware/kernel* | sort | tail -n 1)"
if [ -z "$KERNEL" ] ; then
  echo "error: kernel installation failed! (/boot/kernel* not found)"
  cleanup
  exit 1
fi
#fi