lib/crypto: arm/nh: Migrate optimized code into library

Migrate the arm32 NEON implementation of NH into lib/crypto/.  This
makes the nh() function be optimized on arm32 kernels.

Note: this temporarily makes the adiantum template not utilize the arm32
optimized NH code.  This is resolved in a later commit that converts the
adiantum template to use nh() instead of "nhpoly1305".

Link: https://lore.kernel.org/r/20251211011846.8179-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

Author: Eric Biggers

arch/arm/crypto/Kconfig

@@ -23,16 +23,6 @@ config CRYPTO_GHASH_ARM_CE
 	  that is part of the ARMv8 Crypto Extensions, or a slower variant that
 	  uses the vmull.p8 instruction that is part of the basic NEON ISA.
 
-config CRYPTO_NHPOLY1305_NEON
-	tristate "Hash functions: NHPoly1305 (NEON)"
-	depends on KERNEL_MODE_NEON
-	select CRYPTO_NHPOLY1305
-	help
-	  NHPoly1305 hash function (Adiantum)
-
-	  Architecture: arm using:
-	  - NEON (Advanced SIMD) extensions
-
 config CRYPTO_AES_ARM
 	tristate "Ciphers: AES"
 	select CRYPTO_ALGAPI

arch/arm/crypto/Makefile

@@ -5,7 +5,6 @@
 
 obj-$(CONFIG_CRYPTO_AES_ARM) += aes-arm.o
 obj-$(CONFIG_CRYPTO_AES_ARM_BS) += aes-arm-bs.o
-obj-$(CONFIG_CRYPTO_NHPOLY1305_NEON) += nhpoly1305-neon.o
 
 obj-$(CONFIG_CRYPTO_AES_ARM_CE) += aes-arm-ce.o
 obj-$(CONFIG_CRYPTO_GHASH_ARM_CE) += ghash-arm-ce.o
@@ -14,4 +13,3 @@ aes-arm-y	:= aes-cipher-core.o aes-cipher-glue.o
 aes-arm-bs-y	:= aes-neonbs-core.o aes-neonbs-glue.o
 aes-arm-ce-y	:= aes-ce-core.o aes-ce-glue.o
 ghash-arm-ce-y	:= ghash-ce-core.o ghash-ce-glue.o
-nhpoly1305-neon-y := nh-neon-core.o nhpoly1305-neon-glue.o

arch/arm/crypto/nhpoly1305-neon-glue.c

@@ -117,6 +117,7 @@ config CRYPTO_LIB_NH
 config CRYPTO_LIB_NH_ARCH
 	bool
 	depends on CRYPTO_LIB_NH && !UML
+	default y if ARM && KERNEL_MODE_NEON
 
 config CRYPTO_LIB_POLY1305
 	tristate

lib/crypto/Kconfig

@@ -135,6 +135,7 @@ obj-$(CONFIG_CRYPTO_LIB_NH) += libnh.o
 libnh-y := nh.o
 ifeq ($(CONFIG_CRYPTO_LIB_NH_ARCH),y)
 CFLAGS_nh.o += -I$(src)/$(SRCARCH)
+libnh-$(CONFIG_ARM) += arm/nh-neon-core.o
 endif
 
 ################################################################################

lib/crypto/Makefile

@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * ARM32 accelerated implementation of NH
+ *
+ * Copyright 2018 Google LLC
+ */
+
+#include <asm/neon.h>
+#include <asm/simd.h>
+
+static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
+
+asmlinkage void nh_neon(const u32 *key, const u8 *message, size_t message_len,
+			__le64 hash[NH_NUM_PASSES]);
+
+static bool nh_arch(const u32 *key, const u8 *message, size_t message_len,
+		    __le64 hash[NH_NUM_PASSES])
+{
+	if (static_branch_likely(&have_neon) && message_len >= 64 &&
+	    may_use_simd()) {
+		scoped_ksimd()
+			nh_neon(key, message, message_len, hash);
+		return true;
+	}
+	return false;
+}
+
+#define nh_mod_init_arch nh_mod_init_arch
+static void nh_mod_init_arch(void)
+{
+	if (elf_hwcap & HWCAP_NEON)
+		static_branch_enable(&have_neon);
+}