[RFC PATCH 04/20] crypto: arm/chacha - expose ARM ChaCha routine as library function

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Expose the accelerated NEON ChaCha routine directly as a symbol
export so that users of the ChaCha library can use it directly.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/arm/crypto/Kconfig            |  1 +
 arch/arm/crypto/chacha-neon-glue.c | 19 +++++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/arm/crypto/Kconfig b/arch/arm/crypto/Kconfig
index b24df84a1d7a..70e4d5fe5bdb 100644
--- a/arch/arm/crypto/Kconfig
+++ b/arch/arm/crypto/Kconfig
@@ -130,6 +130,7 @@ config CRYPTO_CHACHA20_NEON
 	depends on KERNEL_MODE_NEON
 	select CRYPTO_BLKCIPHER
 	select CRYPTO_CHACHA20
+	select CRYPTO_ARCH_HAVE_LIB_CHACHA
 
 config CRYPTO_NHPOLY1305_NEON
 	tristate "NEON accelerated NHPoly1305 hash function (for Adiantum)"
diff --git a/arch/arm/crypto/chacha-neon-glue.c b/arch/arm/crypto/chacha-neon-glue.c
index 26576772f18b..1a32c6e5c885 100644
--- a/arch/arm/crypto/chacha-neon-glue.c
+++ b/arch/arm/crypto/chacha-neon-glue.c
@@ -36,6 +36,8 @@ asmlinkage void chacha_4block_xor_neon(const u32 *state, u8 *dst, const u8 *src,
 				       int nrounds);
 asmlinkage void hchacha_block_neon(const u32 *state, u32 *out, int nrounds);
 
+static bool have_neon __ro_after_init;
+
 static void chacha_doneon(u32 *state, u8 *dst, const u8 *src,
 			  unsigned int bytes, int nrounds)
 {
@@ -62,6 +64,18 @@ static void chacha_doneon(u32 *state, u8 *dst, const u8 *src,
 	}
 }
 
+void chacha_crypt(u32 *state, u8 *dst, const u8 *src, unsigned int bytes,
+		  int nrounds)
+{
+	if (!have_neon || bytes <= CHACHA_BLOCK_SIZE || !crypto_simd_usable())
+		return chacha_crypt_generic(state, dst, src, bytes, nrounds);
+
+	kernel_neon_begin();
+	chacha_doneon(state, dst, src, bytes, nrounds);
+	kernel_neon_end();
+}
+EXPORT_SYMBOL(chacha_crypt);
+
 static int chacha_neon_stream_xor(struct skcipher_request *req,
 				  const struct chacha_ctx *ctx, const u8 *iv)
 {
@@ -177,8 +191,9 @@ static struct skcipher_alg algs[] = {
 
 static int __init chacha_simd_mod_init(void)
 {
-	if (!(elf_hwcap & HWCAP_NEON))
-		return -ENODEV;
+	have_neon = (elf_hwcap & HWCAP_NEON);
+	if (!have_neon)
+		return 0;
 
 	return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
 }
-- 
2.17.1