Hi Yonghong, I love your patch! Yet something to improve: [auto build test ERROR on bpf-next/master] url: https://github.com/0day-ci/linux/commits/Yonghong-Song/implement-bpf-iter... base: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master config: openrisc-defconfig (attached as .config) compiler: or1k-linux-gcc (GCC) 9.3.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=openrisc If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): or1k-linux-ld: net/core/filter.o: in function `bpf_skc_to_tcp_timewait_sock': filter.c:(.text+0x3e60): undefined reference to `tcpv6_prot' or1k-linux-ld: net/core/filter.o: in function `bpf_skc_to_tcp_request_sock': filter.c:(.text+0x3ee0): undefined reference to `tcpv6_prot' or1k-linux-ld: filter.c:(.text+0x3ee4): undefined reference to `tcpv6_prot' or1k-linux-ld: net/core/filter.o: in function `init_btf_sock_ids': filter.c:(.text+0x11384): undefined reference to `btf_find_by_name_kind' filter.c:(.text+0x11384): relocation truncated to fit: R_OR1K_INSN_REL_26 against undefined symbol `btf_find_by_name_kind' --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org