Add entropy collector for K64F to mbed HAL for use in mbed TLS

hal/targets.json

@@ -566,7 +566,7 @@
         "supported_toolchains": ["ARM", "GCC_ARM", "IAR"],
         "extra_labels": ["Freescale", "KSDK2_MCUS", "FRDM", "KPSDK_MCUS", "KPSDK_CODE", "MCU_K64F"],
         "is_disk_virtual": true,
-        "macros": ["CPU_MK64FN1M0VMD12", "FSL_RTOS_MBED"],
+        "macros": ["CPU_MK64FN1M0VMD12", "FSL_RTOS_MBED", "MBEDTLS_ENTROPY_HARDWARE_ALT"],
         "inherits": ["Target"],
         "progen": {"target": "frdm-k64f"},
         "detect_code": ["0240"],

hal/targets/hal/TARGET_Freescale/TARGET_KSDK2_MCUS/TARGET_K64F/entropy_hardware_poll.c

@@ -0,0 +1,83 @@
+/*
+ *  Hardware entropy collector for the K64F, using Freescale's RNGA
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ */
+
+/*
+ * Reference: "K64 Sub-Family Reference Manual, Rev. 2", chapter 34
+ */
+
+#include <stdlib.h>
+#include "cmsis.h"
+#include "fsl_common.h"
+#include "fsl_clock.h"
+
+/*
+ * Get one byte of entropy from the RNG, assuming it is up and running.
+ * As recommended (34.1.1), get only one bit of each output.
+ */
+static void rng_get_byte( unsigned char *byte )
+{
+    size_t bit;
+
+    /* 34.5 Steps 3-4-5: poll SR and read from OR when ready */
+    for( bit = 0; bit < 8; bit++ )
+    {
+        while( ( RNG->SR & RNG_SR_OREG_LVL_MASK ) == 0 );
+        *byte |= ( RNG->OR & 1 ) << bit;
+    }
+}
+
+/*
+ * Get len bytes of entropy from the hardware RNG.
+ */
+int mbedtls_hardware_poll( void *data,
+                    unsigned char *output, size_t len, size_t *olen )
+{
+    size_t i;
+    int ret;
+    ((void) data);
+
+    CLOCK_EnableClock( kCLOCK_Rnga0 );
+    CLOCK_DisableClock( kCLOCK_Rnga0 );
+    CLOCK_EnableClock( kCLOCK_Rnga0 );
+
+    /* Set "Interrupt Mask", "High Assurance" and "Go",
+     * unset "Clear interrupt" and "Sleep" */
+    RNG->CR = RNG_CR_INTM_MASK | RNG_CR_HA_MASK | RNG_CR_GO_MASK;
+
+    for( i = 0; i < len; i++ )
+        rng_get_byte( output + i );
+
+    /* Just be extra sure that we didn't do it wrong */
+    if( ( RNG->SR & RNG_SR_SECV_MASK ) != 0 )
+    {
+        ret = -1;
+        goto cleanup;
+    }
+
+    *olen = len;
+    ret = 0;
+
+cleanup:
+    /* Disable clock to save power - assume we're the only users of RNG */
+    CLOCK_DisableClock( kCLOCK_Rnga0 );
+
+    return( ret );
+}
+