Hi Florent,

I love your patch! Yet something to improve:

[auto build test ERROR on bpf-next/master]

url:    https://github.com/0day-ci/linux/commits/Florent-Revest/Add-a-snprintf-eBPF-helper/20210412-233921
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: mips-decstation_r4k_defconfig (attached as .config)
compiler: mipsel-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/168301dda58989eca274d5f5c926675540010e13
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Florent-Revest/Add-a-snprintf-eBPF-helper/20210412-233921
        git checkout 168301dda58989eca274d5f5c926675540010e13
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips 

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 >>):

   mipsel-linux-ld: kernel/bpf/verifier.o: in function `check_helper_call.isra.0':
   verifier.c:(.text+0x13bac): undefined reference to `bpf_printf_prepare'
   mipsel-linux-ld: kernel/bpf/helpers.o: in function `bpf_base_func_proto':
   helpers.c:(.text+0x9c8): undefined reference to `bpf_snprintf_proto'
>> mipsel-linux-ld: helpers.c:(.text+0x9d0): undefined reference to `bpf_snprintf_proto'

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