1 files changed, 25 insertions, 1 deletions

diff --git a/src/lib/libcrypto/bn/arch/riscv64/bn_arch.h b/src/lib/libcrypto/bn/arch/riscv64/bn_arch.h
index 4d6571f9cb..1b4267acc0 100644
--- a/src/lib/libcrypto/bn/arch/riscv64/bn_arch.h
+++ b/src/lib/libcrypto/bn/arch/riscv64/bn_arch.h
@@ -1,4 +1,4 @@
-/*      $OpenBSD: bn_arch.h,v 1.1 2023/01/20 10:04:34 jsing Exp $ */
+/*      $OpenBSD: bn_arch.h,v 1.2 2023/01/31 05:57:08 jsing Exp $ */
 /*
  * Copyright (c) 2023 Joel Sing <jsing@openbsd.org>
  *
@@ -20,5 +20,29 @@
 
 #ifndef OPENSSL_NO_ASM
 
+#if 0 /* Needs testing and enabling. */
+#if defined(__GNUC__)
+#define HAVE_BN_UMUL_HILO
+
+static inline void
+bn_umul_hilo(BN_ULONG a, BN_ULONG b, BN_ULONG *out_h, BN_ULONG *out_l)
+{
+        BN_ULONG h, l;
+
+        /*
+         * Unsigned multiplication using a mulh/mul pair. Note that the order
+         * of these instructions is important, as they can potentially be fused
+         * into a single operation.
+         */
+        __asm__ ("mulh %0, %2, %3; mul %1, %2, %3"
+            : "=r"(h), "=r"(l)
+            : "r"(a), "r"(b));
+
+        *out_h = h;
+        *out_l = l;
+}
+#endif /* __GNUC__ */
+#endif
+
 #endif
 #endif