Hi Daniel, First bad commit (maybe != root cause): tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 8ab774587903771821b59471cc723bba6d893942 commit: b24abcff918a5cbf44b0c982bd3477a93e8e4911 bpf, kconfig: Add consolidated menu entry for bpf with core options date: 6 months ago config: x86_64-buildonly-randconfig-r006-20211012 (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout b24abcff918a5cbf44b0c982bd3477a93e8e4911 # save the attached .config to linux build tree make W=1 ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): >> arch/x86/net/bpf_jit_comp.c:2188:5: warning: no previous prototype for 'arch_prepare_bpf_dispatcher' [-Wmissing-prototypes] 2188 | int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ vim +/arch_prepare_bpf_dispatcher +2188 arch/x86/net/bpf_jit_comp.c 75ccbef6369e94 Björn Töpel 2019-12-13 2187 75ccbef6369e94 Björn Töpel 2019-12-13 @2188 int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs) 75ccbef6369e94 Björn Töpel 2019-12-13 2189 { 75ccbef6369e94 Björn Töpel 2019-12-13 2190 u8 *prog = image; 75ccbef6369e94 Björn Töpel 2019-12-13 2191 75ccbef6369e94 Björn Töpel 2019-12-13 2192 sort(funcs, num_funcs, sizeof(funcs[0]), cmp_ips, NULL); 75ccbef6369e94 Björn Töpel 2019-12-13 2193 return emit_bpf_dispatcher(&prog, 0, num_funcs - 1, funcs); 75ccbef6369e94 Björn Töpel 2019-12-13 2194 } 75ccbef6369e94 Björn Töpel 2019-12-13 2195 :::::: The code at line 2188 was first introduced by commit :::::: 75ccbef6369e94ecac696a152a998a978d41376b bpf: Introduce BPF dispatcher :::::: TO: Björn Töpel <bjorn.topel(a)intel.com&gt; :::::: CC: Alexei Starovoitov <ast(a)kernel.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org