aarch64-none-elf-gcc -c start.S -o start.o
aarch64-none-elf-gcc -c main.c -o main.o -nostdlib -ffreestanding
aarch64-none-elf-ld -T linker.ld start.o main.o -o kernel.elf

qemu-system-aarch64 -M virt -cpu cortex-a53 -serial mon:stdio -nographic -kernel kernel.elf

Run direction

most of the code must run with make and clean with make clean