buffer_op
return buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to);
return buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from);
n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);