1. Kernel configuration files
   arch/arm64/configs:
   Nokia 3.1 (TA-1063/TA-1057/TA-1049/TA-1074/TA-1070): ES2_defconfig

2. How to build

  Prerequisites:

    * ramdisk.img - root fs

    * mkbootimg - boot.img generator

    * The ARM cross-compiler
      We recommend getting the CodeSourcery Lite compiler.
      Or, you can also use prebuild executable binary which is included in
      standard Android tree.

  Step 1: Build Kernel (Image)
    $ cd kernel-3.18

    $ export ARCH=arm64

    $ export CROSS_COMPILE=<cross compile path with prefix>
      NOTE: Please set the location and the prefix of the ARM cross-compiler.
            Please use the absolute path for this.
      ex) <cross compiler path>/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-gnu-6.3.1/bin/aarch64-linux-gnu-

    $ make ES2_defconfig O=<output path>
      NOTE: Please set a configuration file you want to build.

    $ make O=<output path>

    You can see arch/arm64/boot/Image.gz-dtb if you succeed in building the kernel.

  Step 2: Assembling the boot.img
    (In the output directory)
    $ mkbootimg --kernel arch/arm64/boot/Image.gz-dtb \
      --cmdline "bootopt=64S3,32N2,64N2 buildvariant=user veritykeyid=id:7e4333f9bba00adfe0ede979e28ed1920492b40f" \
      --base 0x40000000 --kernel_offset 0x00080000 --ramdisk_offset 0x05000000 --tags_offset 0x4000000 \
      --ramdisk ramdisk.img --output boot.img