How to use libbpf-tools with ubuntu 18.04 4.15 kernel

I'm new to ebpf. I saw that BPF CO-RE argument and it seems it would be the future way to use bpf. But when I try to use it on stock ubuntu 18.04. I had problems. I had other constraints so that I can't upgrade the kernel version.

I notice that the stock kernel doesn't have /sys/kernel/btf/vmlinux. I don't know how to regenerate the vmlinux.h file. But I install the debug symbol package. I think they serve similar purpose but I don't find a way to generate vmlinux.h on the README.

I try to compile the binary in libbpf-tools dir and run time. They all prompt it can't find btf info.

Based on the above problems, is that mean I should use the bcc instead? I can compile and run the python version tools.