libbpf: load bpf program failed: Invalid argument about btfhub HOT 1 CLOSED

Your running kernel is 4.18.0-10 and the BTF is for 4.18.0-13, why is that ? Although it might work, having types from another kernel build might not be good (or sometimes work).

Apart from that, can u make it work with a simple "return" ? Have you tried other kprobes ? Or raw tracepoints ? Unfortunately old verifiers are very lousy in their error messages and one good practice is to "bisect" your source code until "it works", thus trying to have a kprobe with a single return could git you a good indication (iirc char * will be placed in rodata, which is something that might not work in older kernels, it is worth checking).

from btfhub.