Hi Aleksa, First bad commit (maybe != root cause): tree: https://github.com/alibaba/cloud-kernel.git linux-next head: 4da723592714ee2993664252216d9d5b5a3df3eb commit: 5b9369e5de06e80452e2773085a595ffb5988fad [11285/11535] open: introduce openat2(2) syscall config: um-allnoconfig (attached as .config) compiler: gcc-9 (Debian 9.3.0-13) 9.3.0 reproduce (this is a W=1 build): git checkout 5b9369e5de06e80452e2773085a595ffb5988fad # save the attached .config to linux build tree make W=1 ARCH=um 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 >>, old ones prefixed by <<): 13 | #define __SYSCALL_I386(nr, sym, qual) [nr] = 1, | ^ arch/x86/include/generated/asm/syscalls_32.h:1844:1: note: in expansion of macro '__SYSCALL_I386' 1844 | __SYSCALL_I386(427, __ia32_sys_openat2, ) | ^~~~~~~~~~~~~~ arch/x86/um/user-offsets.c:13:46: note: (near initialization for 'syscalls[427]') 13 | #define __SYSCALL_I386(nr, sym, qual) [nr] = 1, | ^ arch/x86/include/generated/asm/syscalls_32.h:1844:1: note: in expansion of macro '__SYSCALL_I386' 1844 | __SYSCALL_I386(427, __ia32_sys_openat2, ) | ^~~~~~~~~~~~~~ arch/x86/um/user-offsets.c:30:6: warning: no previous prototype for 'foo' [-Wmissing-prototypes] 30 | void foo(void) | ^~~ -- 13 | #define __SYSCALL_I386(nr, sym, qual) [nr] = 1, | ^ arch/x86/include/generated/asm/syscalls_32.h:1844:1: note: in expansion of macro '__SYSCALL_I386' 1844 | __SYSCALL_I386(427, __ia32_sys_openat2, ) | ^~~~~~~~~~~~~~ arch/x86/um/user-offsets.c:13:46: note: (near initialization for 'syscalls[427]') 13 | #define __SYSCALL_I386(nr, sym, qual) [nr] = 1, | ^ arch/x86/include/generated/asm/syscalls_32.h:1844:1: note: in expansion of macro '__SYSCALL_I386' 1844 | __SYSCALL_I386(427, __ia32_sys_openat2, ) | ^~~~~~~~~~~~~~ arch/x86/um/user-offsets.c:30:6: warning: no previous prototype for 'foo' [-Wmissing-prototypes] 30 | void foo(void) | ^~~ In file included from arch/um/kernel/asm-offsets.c:1: arch/x86/um/shared/sysdep/kernel-offsets.h:9:6: warning: no previous prototype for 'foo' [-Wmissing-prototypes] 9 | void foo(void) | ^~~ vim +13 arch/x86/um/user-offsets.c 8d0b9dc9be3919 arch/um/sys-x86_64/user-offsets.c Al Viro 2005-05-05 11 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 12 #ifdef __i386__ cfcbadb49dabb0 arch/x86/um/user-offsets.c Andy Lutomirski 2016-01-28 @13 #define __SYSCALL_I386(nr, sym, qual) [nr] = 1, 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 14 static char syscalls[] = { 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 15 #include <asm/syscalls_32.h> 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 16 }; 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 17 #else cfcbadb49dabb0 arch/x86/um/user-offsets.c Andy Lutomirski 2016-01-28 18 #define __SYSCALL_64(nr, sym, qual) [nr] = 1, 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 19 static char syscalls[] = { 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 20 #include <asm/syscalls_64.h> 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 21 }; 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 22 #endif 45db1c6176c817 arch/x86/um/user-offsets.c H. Peter Anvin 2011-12-05 23 :::::: The code at line 13 was first introduced by commit :::::: cfcbadb49dabb05efa23e1a0f95f3391c0a815bc x86/syscalls: Add syscall entry qualifiers :::::: TO: Andy Lutomirski <luto(a)kernel.org&gt; :::::: CC: Ingo Molnar <mingo(a)kernel.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org