lib/crypto: riscv/poly1305: Import OpenSSL/CRYPTOGAMS implementation

This is a straight import of the OpenSSL/CRYPTOGAMS Poly1305
implementation for riscv authored by Andy Polyakov.  The file
'poly1305-riscv.pl' is taken straight from
https://github.com/dot-asm/cryptogams commit
5e3fba73576244708a752fa61a8e93e587f271bb.  This patch was tested on
SpacemiT X60, with 2~2.5x improvement over generic implementation.

Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
Signed-off-by: Zhihang Shao <zhihang.shao.iscas@gmail.com>
[EB: ported to lib/crypto/riscv/]
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250829152513.92459-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

lib/crypto/Kconfig

@@ -128,6 +128,7 @@ config CRYPTO_LIB_POLY1305_ARCH
 	default y if MIPS
 	# The PPC64 code needs to be fixed to work in softirq context.
 	default y if PPC64 && CPU_LITTLE_ENDIAN && VSX && BROKEN
+	default y if RISCV
 	default y if X86_64
 
 # This symbol controls the inclusion of the Poly1305 generic code.  This differs
@@ -143,7 +144,7 @@ config CRYPTO_LIB_POLY1305_GENERIC
 
 config CRYPTO_LIB_POLY1305_RSIZE
 	int
-	default 2 if MIPS
+	default 2 if MIPS || RISCV
 	default 11 if X86_64
 	default 9 if ARM || ARM64
 	default 1

lib/crypto/Makefile

@@ -112,6 +112,19 @@ endif
 
 libpoly1305-$(CONFIG_PPC) += powerpc/poly1305-p10le_64.o
 
+ifeq ($(CONFIG_RISCV),y)
+libpoly1305-y += riscv/poly1305-core.o
+poly1305-perlasm-flavour-$(CONFIG_32BIT) := 32
+poly1305-perlasm-flavour-$(CONFIG_64BIT) := 64
+quiet_cmd_perlasm_poly1305 = PERLASM $@
+      cmd_perlasm_poly1305 = $(PERL) $< $(poly1305-perlasm-flavour-y) $@
+# Use if_changed instead of cmd, in case the flavour changed.
+$(obj)/riscv/poly1305-core.S: $(src)/riscv/poly1305-riscv.pl FORCE
+	$(call if_changed,perlasm_poly1305)
+targets += riscv/poly1305-core.S
+AFLAGS_riscv/poly1305-core.o += -Dpoly1305_init=poly1305_block_init
+endif
+
 ifeq ($(CONFIG_X86),y)
 libpoly1305-y += x86/poly1305-x86_64-cryptogams.o
 $(obj)/x86/poly1305-x86_64-cryptogams.S: $(src)/x86/poly1305-x86_64-cryptogams.pl
@@ -124,6 +137,7 @@ endif # CONFIG_CRYPTO_LIB_POLY1305_ARCH
 clean-files += arm/poly1305-core.S \
 	       arm64/poly1305-core.S \
 	       mips/poly1305-core.S \
+	       riscv/poly1305-core.S \
 	       x86/poly1305-x86_64-cryptogams.S
 
 ################################################################################

lib/crypto/riscv/poly1305.h

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * OpenSSL/Cryptogams accelerated Poly1305 transform for riscv
+ *
+ * Copyright (C) 2025 Institute of Software, CAS.
+ */
+
+asmlinkage void poly1305_block_init(struct poly1305_block_state *state,
+				    const u8 raw_key[POLY1305_BLOCK_SIZE]);
+asmlinkage void poly1305_blocks(struct poly1305_block_state *state,
+				const u8 *src, u32 len, u32 hibit);
+asmlinkage void poly1305_emit(const struct poly1305_state *state,
+			      u8 digest[POLY1305_DIGEST_SIZE],
+			      const u32 nonce[4]);