Hi Kefeng,

It's probably a bug fix that unveils the link errors.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.4.y
head:   cac6eb2794c85e7777fb0caac6fa75b6364d81a0
commit: 1865d6440fb63ad979d7034b2d7c94937bfd2200 [2066/5257] PCI: mobiveil: Fix csr_read()/write() build issue
config: riscv-allyesconfig (attached as .config)
compiler: riscv64-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout 1865d6440fb63ad979d7034b2d7c94937bfd2200
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=riscv 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>, old ones prefixed by <<):

riscv64-linux-ld: lib/ubsan.o: in function `.L2':
>> ubsan.c:(.text.unlikely+0x38): undefined reference to `__ashlti3'
>> riscv64-linux-ld: ubsan.c:(.text.unlikely+0x42): undefined reference to `__ashrti3'

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0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org