net/smc/smc_llc.c:26:2: warning: field within 'struct smc_llc_hdr' is less aligned than 'union smc_llc_hdr::(anonymous at net/smc/smc_llc.c:26:2)' and is usually due to 'struct smc_llc_hdr' being packed, which can lead to unaligned accesses

From: kernel test robot
Date: Fri Jun 24 2022 - 22:44:49 EST


Hi Karsten,

FYI, the error/warning still remains.

tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 92f20ff72066d8d7e2ffb655c2236259ac9d1c5d
commit: b4ba4652b3f8b7c9bbb5786f8acf4724bdab2196 net/smc: extend LLC layer for SMC-Rv2
date: 8 months ago
config: arm-randconfig-c002-20220622 (https://download.01.org/0day-ci/archive/20220624/202206240723.OOu0nUgA-lkp@xxxxxxxxx/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project af6d2a0b6825e71965f3e2701a63c239fa0ad70f)
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=b4ba4652b3f8b7c9bbb5786f8acf4724bdab2196
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git fetch --no-tags linus master
git checkout b4ba4652b3f8b7c9bbb5786f8acf4724bdab2196
# 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 SHELL=/bin/bash net/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

>> net/smc/smc_llc.c:26:2: warning: field within 'struct smc_llc_hdr' is less aligned than 'union smc_llc_hdr::(anonymous at net/smc/smc_llc.c:26:2)' and is usually due to 'struct smc_llc_hdr' being packed, which can lead to unaligned accesses [-Wunaligned-access]
union {
^
1 warning generated.


vim +26 net/smc/smc_llc.c

23
24 struct smc_llc_hdr {
25 struct smc_wr_rx_hdr common;
> 26 union {
27 struct {
28 u8 length; /* 44 */
29 #if defined(__BIG_ENDIAN_BITFIELD)
30 u8 reserved:4,
31 add_link_rej_rsn:4;
32 #elif defined(__LITTLE_ENDIAN_BITFIELD)
33 u8 add_link_rej_rsn:4,
34 reserved:4;
35 #endif
36 };
37 u16 length_v2; /* 44 - 8192*/
38 };
39 u8 flags;
40 } __packed; /* format defined in
41 * IBM Shared Memory Communications Version 2
42 * (https://www.ibm.com/support/pages/node/6326337)
43 */
44

--
0-DAY CI Kernel Test Service
https://01.org/lkp