[kbuild-all] [jolsa-perf:bpf/ftrace 2/6] kernel/bpf/syscall.c:2931: undefined reference to `__bpf_prog_enter'

tree: https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git bpf/ftrace head: f6ca0faab8697bc6a3a6e4ffcb72b8a0a0a66558 commit: e201e5e6b442644c28e6c9a001ef2b7e4428aa51 [2/6] bpf: Add bpf ftrace link config: x86_64-kexec (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/jolsa/perf.git/commit/?id... git remote add jolsa-perf https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git git fetch --no-tags jolsa-perf bpf/ftrace git checkout e201e5e6b442644c28e6c9a001ef2b7e4428aa51 # 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 errors (new ones prefixed by >>): ld: kernel/bpf/syscall.o: in function `bpf_ftrace_function_call': vim +2931 kernel/bpf/syscall.c 2919 2920 static void 2921 bpf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, 2922 struct ftrace_ops *ops, struct ftrace_regs *fregs) 2923 { 2924 struct bpf_tracing_ftrace_link *tr_link; 2925 struct bpf_prog *prog; 2926 u64 start; 2927 2928 tr_link = container_of(ops, struct bpf_tracing_ftrace_link, ops); 2929 prog = tr_link->link.prog; 2930 2932 if (start) 2933 bpf_trace_run2(tr_link->link.prog, ip, parent_ip); 2934 2936 } 2937 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org