Hi Lorenzo, First bad commit (maybe != root cause): tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 0280e3c58f92b2fe0e8fbbdf8d386449168de4a8 commit: a3c62a042237d1adeb0290dcb768e17edd6dcd25 net: mtk_eth: add COMPILE_TEST support date: 6 weeks ago config: s390-buildonly-randconfig-r005-20220126 (https://download.01.org/0day-ci/archive/20220126/202201261608.BLH8XrDI-lk...) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 2a1b7aa016c0f4b5598806205bdfbab1ea2d92c4) 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 a3c62a042237d1adeb0290dcb768e17edd6dcd25 # save the config file to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash drivers/net/ethernet/mediatek/ 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/ethernet/mediatek/mtk_star_emac.c:12: 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:75: include/asm-generic/io.h:464:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] val = __raw_readb(PCI_IOBASE + addr); ~~~~~~~~~~ ^ include/asm-generic/io.h:477:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr)); ~~~~~~~~~~ ^ include/uapi/linux/byteorder/big_endian.h:36:59: note: expanded from macro '__le16_to_cpu' #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x)) ^ include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16' #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) ^ In file included from drivers/net/ethernet/mediatek/mtk_star_emac.c:12: 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:75: 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:115:54: note: expanded from macro '__swab32' #define __swab32(x) (__u32)__builtin_bswap32((__u32)(x)) ^ In file included from drivers/net/ethernet/mediatek/mtk_star_emac.c:12: 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:75: 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 mtk_star_of_match[] = { ^ 13 warnings generated. vim +/mtk_star_of_match +1559 drivers/net/ethernet/mediatek/mtk_star_emac.c 8c7bd5a454ffc2 Bartosz Golaszewski 2020-05-22 1558 8c7bd5a454ffc2 Bartosz Golaszewski 2020-05-22 @1559 static const struct of_device_id mtk_star_of_match[] = { 8c7bd5a454ffc2 Bartosz Golaszewski 2020-05-22 1560 { .compatible = "mediatek,mt8516-eth", }, 8c7bd5a454ffc2 Bartosz Golaszewski 2020-05-22 1561 { .compatible = "mediatek,mt8518-eth", }, 8c7bd5a454ffc2 Bartosz Golaszewski 2020-05-22 1562 { .compatible = "mediatek,mt8175-eth", }, 8c7bd5a454ffc2 Bartosz Golaszewski 2020-05-22 1563 { } 8c7bd5a454ffc2 Bartosz Golaszewski 2020-05-22 1564 }; 8c7bd5a454ffc2 Bartosz Golaszewski 2020-05-22 1565 MODULE_DEVICE_TABLE(of, mtk_star_of_match); 8c7bd5a454ffc2 Bartosz Golaszewski 2020-05-22 1566 :::::: The code at line 1559 was first introduced by commit :::::: 8c7bd5a454ffc2b0518d1499c4af95f00291d2af net: ethernet: mtk-star-emac: new driver :::::: TO: Bartosz Golaszewski <bgolaszewski(a)baylibre.com&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