Sorry for the late reply. I couldn't post messages. It always said internal error.
Yes, it was xor-neon and it is not in the base system. The solution:
w g e t http://www.tinycorelinux.net/12.x/aarch64/releases/RPi/src/kernel/modules-5.4.51-piCore-v8.tar.xz
tar xf modules-5.4.51-piCore-v8.tar.xz
m k d i r /lib/modules/5.4.51-piCore-v8/kernel/arch/arm64/lib
c p lib/modules/5.4.51-piCore-v8/kernel/arch/arm64/lib/xor-neon.ko /lib/modules/5.4.51-piCore-v8/kernel/arch/arm64/lib
depmod -a `uname -r`
Some commands above are separted with spaces. If not, there will be the internal error. That is why I post this message so late
After that the modules xor and btrfs can be loaded properly.
Please add xor-neon.ko in the piCore base in the future release.
Thanks