Hi Tong,

[FYI, it's a private test report for your RFC patch.]
[auto build test ERROR on v5.12]
[also build test ERROR on next-20210507]
[cannot apply to linus/master]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Tong-Tiangen/riscv-add-VMAP_STACK-overflow-detection/20210507-171736
base:    9f4ad9e425a1d3b6a34617b8ea226d56a119a717
config: riscv-nommu_k210_defconfig (attached as .config)
compiler: riscv64-linux-gcc (GCC) 9.3.0
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
        # https://github.com/0day-ci/linux/commit/60d8a3da002bf59ec0abeb88403dbb11cf31583f
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Tong-Tiangen/riscv-add-VMAP_STACK-overflow-detection/20210507-171736
        git checkout 60d8a3da002bf59ec0abeb88403dbb11cf31583f
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=riscv 

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

All errors (new ones prefixed by >>):

   riscv64-linux-ld: kernel/fork.o: in function `.L59':
>> fork.c:(.text+0x222): undefined reference to `vfree_atomic'
   riscv64-linux-ld: kernel/fork.o: in function `.L283':
>> fork.c:(.text+0xd8a): undefined reference to `find_vm_area'

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