To build source-based kernel:

1. Set CROSS_COMPILE to an appropriate path prefix, e.g.,

   export CROSS_COMPILE=../cm/prebuilt/linux-x86/toolchain/arm-eabi-4.4.3/bin/arm-eabi-

2. Build kernel:

   make m2_spr_defconfig && make -j 4


And to merge the kernel into recovery:

3. Pull recovery partition from device:

   adb reboot recovery
   adb root
   adb shell 'dd if=/dev/block/mmcblk0p18 of=/tmp/recovery.img bs=256k'
   adb pull /tmp/recovery.img

4. Merge newly-built zImage into recovery.img:

   ../cm/out/host/linux-x86/bin/unpackbootimg -i recovery.img
   cp arch/arm/boot/zImage recovery.img-zImage

   ../cm/out/host/linux-x86/bin/mkbootimg --kernel recovery.img-zImage \
       --ramdisk recovery.img-ramdisk.gz \
       --cmdline "console=null androidboot.hardware=qcom user_debug=31" \
       --base 0x80200000 --pagesize 2048 --ramdiskaddr 0x81500000 \
       -o recovery.img