Unknown symbols while loading KO's

i am new to OpenWrt, i downloaded an VM instance of OpenWrt.
we compiled an private kernel module and observing unresolved symbols while loading on OpenWrt, when i load the same KO's on linux (Ubuntu) no issue is observed.

Unknown symbol kmem_cache_alloc_trace (err 0)
Unknown symbol __fentry__ (err 0)
Unknown symbol ktime_get_real_ts64 (err 0)
Unknown symbol __warn_printk (err 0)

Can some one provide some inputs to resolve the same.