Search notes:

arch/x86/boot/compressed/vmlinux.bin.gz

cat arch/x86/boot/compressed/vmlinux.bin arch/x86/boot/compressed/vmlinux.relocs | gzip -n -f -9 > arch/x86/boot/compressed/vmlinux.bin.gz

vmlinux.bin.gz is used to create arch/x86/boot/compressed/piggy.S.