make: *** [Makefile:10: kernel.bin] Error 1

[vuk5002]

I cannot get kernel.bin to compile in any way
tried on windows with wsl ld -o kernel.bin -Ttext 0x1000 kernel_entry.o kernel.o --oformat binary
and first time it worked, but another time
ld: warning: cannot find entry symbol _start; defaulting to 0000000000001000
ld: kernel.o: in function main': kernel.c:(.text+0xe): undefined reference to clear_screen'
ld: kernel.c:(.text+0x24): undefined reference to `kprint_at'

any help??

Update: error is coming from ld -o kernel.bin -Ttext 0x1000 kernel_entry.o kernel.o --oformat binary and it gives me
kernel_entry.o: file not recognized: File format not recognized but kernel_entry.o is there