SECLIB-667: Accelerate SHA-256 with A64 crypto extensions
Provide an additional pair of #defines, MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT
and MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY. At most one of them may be
specified. If used, it is necessary to compile with -march=armv8-a+crypto.
The MBEDTLS_SHA256_PROCESS_ALT and MBEDTLS_SHA256_ALT mechanisms
continue to work, and are mutually exclusive with A64_CRYPTO.
There should be minimal code size impact if no A64_CRYPTO option is set.
Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index a935c80..1c631b5 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -2760,6 +2760,56 @@
#define MBEDTLS_SHA256_C
/**
+ * \def MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT
+ *
+ * Enable acceleration of the SHA-256 cryptographic hash algorithm with the
+ * Arm A64 cryptographic extensions if they are available at runtime. If not,
+ * it will fall back to the C implementation.
+ *
+ * \note If MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT is defined when building
+ * for a non-Aarch64 build it will be silently ignored.
+ *
+ * \note The code uses Neon intrinsics, so \c CFLAGS must be set to a minimum
+ * of \c -march=armv8-a+crypto.
+ *
+ * \warning MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT cannot be defined at the
+ * same time as MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY.
+ *
+ * Requires: MBEDTLS_SHA256_C.
+ *
+ * Module: library/sha256.c
+ *
+ * Uncomment to have the library check for the A64 SHA-256 crypto extensions
+ * and use them if available.
+ */
+//#define MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT
+
+/**
+ * \def MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY
+ *
+ * Enable acceleration of the SHA-256 cryptographic hash algorithm with the
+ * Arm A64 cryptographic extensions, which must be available at runtime (or
+ * an illegal instruction fault will occur).
+ *
+ * \note This allows builds with a smaller code size than with
+ * MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT
+ *
+ * \note The code uses Neon intrinsics, so \c CFLAGS must be set to a minimum
+ * of \c -march=armv8-a+crypto.
+ *
+ * \warning MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY cannot be defined at the same
+ * time as MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT.
+ *
+ * Requires: MBEDTLS_SHA256_C.
+ *
+ * Module: library/sha256.c
+ *
+ * Uncomment to have the library use the A64 SHA-256 crypto extensions
+ * unconditionally.
+ */
+//#define MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY
+
+/**
* \def MBEDTLS_SHA384_C
*
* Enable the SHA-384 cryptographic hash algorithm.