nd_pfn_validate
rc = nd_pfn_validate(nd_pfn, DAX_SIG);
int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig);
EXPORT_SYMBOL(nd_pfn_validate);
rc = nd_pfn_validate(nd_pfn, PFN_SIG);
rc = nd_pfn_validate(nd_pfn, sig);