I also get an error w.r.t. copy_struct_from_user() but on RHEL 8.3 (4.18.0-240.el8.x86_64)

[C-Newman]

# make
make -C /lib/modules/`uname -r`/build M=$PWD modules
make[1]: Entering directory '/usr/src/kernels/4.18.0-240.el8.x86_64'
  CC [M]  /root/downloads/amd_hsmp-master/amd_hsmp.o
/root/downloads/amd_hsmp-master/amd_hsmp.c: In function ‘hsmp_ioctl’:
/root/downloads/amd_hsmp-master/amd_hsmp.c:280:6: error: implicit declaration of function ‘copy_struct_from_user’; did you mean ‘copy_from_user’? [-Werror=implicit-function-declaration]
  if (copy_struct_from_user(&msg, sizeof(msg), arguser, sizeof(struct hsmp_message)))
      ^~~~~~~~~~~~~~~~~~~~~
      copy_from_user
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:322: /root/downloads/amd_hsmp-master/amd_hsmp.o] Error 1
make[1]: *** [Makefile:1544: _module_/root/downloads/amd_hsmp-master] Error 2
make[1]: Leaving directory '/usr/src/kernels/4.18.0-240.el8.x86_64'
make: *** [Makefile:16: default] Error 2