Hi Heiko, First bad commit (maybe != root cause): tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master head: 6b02addb1d1748d21dd1261e46029b264be4e5a0 commit: 08c8e685c7c9223f9c4ad6365e02bebd3f106480 [7201/7920] s390: add ARCH_HAS_DEBUG_WX support config: s390-randconfig-r022-20200916 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 9e3842d60351f986d77dfe0a94f76e4fd895f188) 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 # install s390 cross compiling tool for clang build # apt-get install binutils-s390x-linux-gnu git checkout 08c8e685c7c9223f9c4ad6365e02bebd3f106480 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=s390 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 >>): debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops); ^~~~~~~~~~~ pidfd_fops include/linux/pid.h:75:37: note: 'pidfd_fops' declared here extern const struct file_operations pidfd_fops; ^ 1 error generated. # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commi... git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git git fetch --no-tags linux-next master git checkout 08c8e685c7c9223f9c4ad6365e02bebd3f106480 vim +232 arch/s390/mm/dump_pagetables.c e76e82d772522b Heiko Carstens 2012-10-04 218 e76e82d772522b Heiko Carstens 2012-10-04 219 static int pt_dump_init(void) e76e82d772522b Heiko Carstens 2012-10-04 220 { e76e82d772522b Heiko Carstens 2012-10-04 221 /* e76e82d772522b Heiko Carstens 2012-10-04 222 * Figure out the maximum virtual address being accessible with the e76e82d772522b Heiko Carstens 2012-10-04 223 * kernel ASCE. We need this to keep the page table walker functions e76e82d772522b Heiko Carstens 2012-10-04 224 * from accessing non-existent entries. e76e82d772522b Heiko Carstens 2012-10-04 225 */ e76e82d772522b Heiko Carstens 2012-10-04 226 max_addr = (S390_lowcore.kernel_asce & _REGION_ENTRY_TYPE_MASK) >> 2; e76e82d772522b Heiko Carstens 2012-10-04 227 max_addr = 1UL << (max_addr * 11 + 31); c972cc60c23f5a Heiko Carstens 2012-10-05 228 address_markers[MODULES_NR].start_address = MODULES_VADDR; e76e82d772522b Heiko Carstens 2012-10-04 229 address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap; e76e82d772522b Heiko Carstens 2012-10-04 230 address_markers[VMALLOC_NR].start_address = VMALLOC_START; 08c8e685c7c922 Heiko Carstens 2020-09-09 231 if (IS_ENABLED(CONFIG_PTDUMP_DEBUGFS)) e76e82d772522b Heiko Carstens 2012-10-04 @232 debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops); :::::: The code at line 232 was first introduced by commit :::::: e76e82d772522b05ed93228478d2a4460754b6a4 s390/mm: add page table dumper :::::: TO: Heiko Carstens <heiko.carstens(a)de.ibm.com&gt; :::::: CC: Martin Schwidefsky <schwidefsky(a)de.ibm.com&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org