Hi Jiri,

First bad commit (maybe != root cause):

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   6e7f2eacf09811d092c1b41263108ac7fe0d089d
commit: aebe5fc3b5685e1d9b86cc8314a8e8f3c6f3284e n_hdlc: put init/exit strings directly to prints
date:   3 months ago
config: microblaze-randconfig-r003-20200507 (attached as .config)
compiler: microblaze-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 aebe5fc3b5685e1d9b86cc8314a8e8f3c6f3284e
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=microblaze 

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 >>):

>> ERROR: "min_low_pfn" [net/mac80211/mac80211.ko] undefined!
>> ERROR: "min_low_pfn" [net/tls/tls.ko] undefined!
>> ERROR: "min_low_pfn" [drivers/mtd/nand/raw/cadence-nand-controller.ko] undefined!
>> ERROR: "min_low_pfn" [drivers/mtd/nand/raw/nand.ko] undefined!
>> ERROR: "min_low_pfn" [drivers/hwtracing/intel_th/intel_th_msu_sink.ko] undefined!
>> ERROR: "min_low_pfn" [drivers/hwtracing/intel_th/intel_th_msu.ko] undefined!
>> ERROR: "min_low_pfn" [drivers/md/dm-crypt.ko] undefined!
>> ERROR: "min_low_pfn" [drivers/media/common/videobuf2/videobuf2-dma-contig.ko] undefined!
>> ERROR: "min_low_pfn" [drivers/usb/misc/usbtest.ko] undefined!
>> ERROR: "min_low_pfn" [drivers/net/usb/usbnet.ko] undefined!
>> ERROR: "min_low_pfn" [crypto/essiv.ko] undefined!
>> ERROR: "min_low_pfn" [crypto/tcrypt.ko] undefined!
>> ERROR: "min_low_pfn" [fs/pstore/ramoops.ko] undefined!

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