bpf_core_field_offset
off = bpf_core_field_offset(struct nameidata, pathname);
out->int_off = bpf_core_field_offset(in->int_field);
out->struct_off = bpf_core_field_offset(in->struct_field);
out->union_off = bpf_core_field_offset(in->union_field);
out->arr_off = bpf_core_field_offset(in->arr_field);
out->arr_elem_off = bpf_core_field_offset(struct core_reloc_size, arr_field[1]);
out->ptr_off = bpf_core_field_offset(struct core_reloc_size, ptr_field);
out->enum_off = bpf_core_field_offset(struct core_reloc_size, enum_field);
out->float_off = bpf_core_field_offset(struct core_reloc_size, float_field);
(void *)pos - bpf_core_field_offset(struct wakeup_source, entry),