linux-kernel - drivers/net/ethernet/sfc/falcon/selftest.c:43:15: warning: field ip within 'struct ef4_loopback_payload' is less aligned than 'struct iphdr' and is usually due to 'struct ef4_loopback_payload' being packed, which can lead to unaligned accesses

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Message-ID: <202303221557.Yc4KdwGu-lkp@intel.com>
Date:   Wed, 22 Mar 2023 15:11:25 +0800
From:   kernel test robot <lkp@...el.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: drivers/net/ethernet/sfc/falcon/selftest.c:43:15: warning: field ip
 within 'struct ef4_loopback_payload' is less aligned than 'struct iphdr' and
 is usually due to 'struct ef4_loopback_payload' being packed, which can lead
 to unaligned accesses

Hi Arnd,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   a1effab7a3a35a837dd9d2b974a1bc4939df1ad5
commit: 250c1a694ff304e5d69e74ab32755eddcc2b8f65 ARM: pxa: convert to multiplatform
date:   11 months ago
config: arm-randconfig-r023-20230322 (https://download.01.org/0day-ci/archive/20230322/202303221557.Yc4KdwGu-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 67409911353323ca5edf2049ef0df54132fa1ca7)
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 arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=250c1a694ff304e5d69e74ab32755eddcc2b8f65
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 250c1a694ff304e5d69e74ab32755eddcc2b8f65
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash drivers/net/ethernet/sfc/falcon/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303221557.Yc4KdwGu-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/net/ethernet/sfc/falcon/selftest.c:43:15: warning: field ip within 'struct ef4_loopback_payload' is less aligned than 'struct iphdr' and is usually due to 'struct ef4_loopback_payload' being packed, which can lead to unaligned accesses [-Wunaligned-access]
           struct iphdr ip;
                        ^
   1 warning generated.


vim +43 drivers/net/ethernet/sfc/falcon/selftest.c

5a6681e22c1409 Edward Cree 2016-11-28  34  
5a6681e22c1409 Edward Cree 2016-11-28  35  /*
5a6681e22c1409 Edward Cree 2016-11-28  36   * Loopback test packet structure
5a6681e22c1409 Edward Cree 2016-11-28  37   *
5a6681e22c1409 Edward Cree 2016-11-28  38   * The self-test should stress every RSS vector, and unfortunately
5a6681e22c1409 Edward Cree 2016-11-28  39   * Falcon only performs RSS on TCP/UDP packets.
5a6681e22c1409 Edward Cree 2016-11-28  40   */
5a6681e22c1409 Edward Cree 2016-11-28  41  struct ef4_loopback_payload {
5a6681e22c1409 Edward Cree 2016-11-28  42  	struct ethhdr header;
5a6681e22c1409 Edward Cree 2016-11-28 @43  	struct iphdr ip;
5a6681e22c1409 Edward Cree 2016-11-28  44  	struct udphdr udp;
5a6681e22c1409 Edward Cree 2016-11-28  45  	__be16 iteration;
5a6681e22c1409 Edward Cree 2016-11-28  46  	char msg[64];
5a6681e22c1409 Edward Cree 2016-11-28  47  } __packed;
5a6681e22c1409 Edward Cree 2016-11-28  48  

:::::: The code at line 43 was first introduced by commit
:::::: 5a6681e22c1409089132085811857d6da828761b sfc: separate out SFC4000 ("Falcon") support into new sfc-falcon driver

:::::: TO: Edward Cree <ecree@...arflare.com>
:::::: CC: David S. Miller <davem@...emloft.net>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests