Hi Alexander, First bad commit (maybe != root cause): tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: af4cf6a5689a9ecc21722cb2bb6220dcaee89c6e commit: 227d72063fccb2d19b30fb4197fba478514f7d83 dsa: simplify Kconfig symbols and dependencies date: 4 months ago config: s390-randconfig-r035-20210711 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 8d69635ed9ecf36fd0ca85906bfde17949671cbe) 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 # 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 227d72063fccb2d19b30fb4197fba478514f7d83 # 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 warnings (new ones prefixed by >>): In file included from drivers/net/dsa/ocelot/seville_vsc9953.c:6: In file included from include/soc/mscc/ocelot_vcap.h:9: In file included from include/soc/mscc/ocelot.h:10: In file included from include/linux/if_vlan.h:10: In file included from include/linux/netdevice.h:37: In file included from include/net/net_namespace.h:39: In file included from include/linux/skbuff.h:31: In file included from include/linux/dma-mapping.h:10: In file included from include/linux/scatterlist.h:9: In file included from arch/s390/include/asm/io.h:80: include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr)); ~~~~~~~~~~ ^ include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu' #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x)) ^ include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32' ___constant_swab32(x) : \ ^ include/uapi/linux/swab.h:21:12: note: expanded from macro '___constant_swab32' (((__u32)(x) & (__u32)0x00ff0000UL) >> 8) | \ ^ In file included from drivers/net/dsa/ocelot/seville_vsc9953.c:6: In file included from include/soc/mscc/ocelot_vcap.h:9: In file included from include/soc/mscc/ocelot.h:10: In file included from include/linux/if_vlan.h:10: In file included from include/linux/netdevice.h:37: In file included from include/net/net_namespace.h:39: In file included from include/linux/skbuff.h:31: In file included from include/linux/dma-mapping.h:10: In file included from include/linux/scatterlist.h:9: In file included from arch/s390/include/asm/io.h:80: include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr)); ~~~~~~~~~~ ^ include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu' #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x)) ^ include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32' ___constant_swab32(x) : \ ^ include/uapi/linux/swab.h:22:12: note: expanded from macro '___constant_swab32' (((__u32)(x) & (__u32)0xff000000UL) >> 24))) ^ In file included from drivers/net/dsa/ocelot/seville_vsc9953.c:6: In file included from include/soc/mscc/ocelot_vcap.h:9: In file included from include/soc/mscc/ocelot.h:10: In file included from include/linux/if_vlan.h:10: In file included from include/linux/netdevice.h:37: In file included from include/net/net_namespace.h:39: In file included from include/linux/skbuff.h:31: In file included from include/linux/dma-mapping.h:10: In file included from include/linux/scatterlist.h:9: In file included from arch/s390/include/asm/io.h:80: include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr)); ~~~~~~~~~~ ^ include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu' #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x)) ^ include/uapi/linux/swab.h:120:12: note: expanded from macro '__swab32' __fswab32(x)) ^ In file included from drivers/net/dsa/ocelot/seville_vsc9953.c:6: In file included from include/soc/mscc/ocelot_vcap.h:9: In file included from include/soc/mscc/ocelot.h:10: In file included from include/linux/if_vlan.h:10: In file included from include/linux/netdevice.h:37: In file included from include/net/net_namespace.h:39: In file included from include/linux/skbuff.h:31: In file included from include/linux/dma-mapping.h:10: In file included from include/linux/scatterlist.h:9: In file included from arch/s390/include/asm/io.h:80: include/asm-generic/io.h:501:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] __raw_writeb(value, PCI_IOBASE + addr); ~~~~~~~~~~ ^ include/asm-generic/io.h:511:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr); ~~~~~~~~~~ ^ include/asm-generic/io.h:521:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr); ~~~~~~~~~~ ^ include/asm-generic/io.h:609:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] readsb(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:617:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] readsw(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:625:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] readsl(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:634:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] writesb(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:643:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] writesw(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] writesl(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ static const struct of_device_id seville_of_match[] = { ^ 21 warnings generated. vim +/seville_of_match +1255 drivers/net/dsa/ocelot/seville_vsc9953.c 84705fc165526e Maxim Kochetkov 2020-07-13 1254 84705fc165526e Maxim Kochetkov 2020-07-13 @1255 static const struct of_device_id seville_of_match[] = { 84705fc165526e Maxim Kochetkov 2020-07-13 1256 { .compatible = "mscc,vsc9953-switch" }, 84705fc165526e Maxim Kochetkov 2020-07-13 1257 { }, 84705fc165526e Maxim Kochetkov 2020-07-13 1258 }; 84705fc165526e Maxim Kochetkov 2020-07-13 1259 MODULE_DEVICE_TABLE(of, seville_of_match); 84705fc165526e Maxim Kochetkov 2020-07-13 1260 :::::: The code at line 1255 was first introduced by commit :::::: 84705fc165526e8e55d208b2b10a48cc720a106a net: dsa: felix: introduce support for Seville VSC9953 switch :::::: TO: Maxim Kochetkov <fido_max(a)inbox.ru&gt; :::::: CC: David S. Miller <davem(a)davemloft.net&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org