Diff: source/entropy_hardware_poll.c

Revision:

1:24750b9ad5ef

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/entropy_hardware_poll.c	Fri Jan 22 16:44:49 2016 -0600
@@ -0,0 +1,65 @@
+/*
+ *  Temporary "entropy" collector for Cortex-M4
+ *
+ *  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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+/*
+ * WARNING: this is a temporary hack!
+ * 1. Currently does not provide strong entropy, should be replaced to use the
+ * on-board hardware RNG (see IOTSSL-303)
+ * 2. This should be in a separete yotta module which would be a target
+ * dependency of mbedtls (see IOTSSL-313)
+ */
+
+#if defined(TARGET_LIKE_CORTEX_M4)
+
+#include "MK64F12.h"
+#include "core_cm4.h"
+#include <string.h>
+
+unsigned long hardclock( void )
+{
+    static int dwt_started = 0;
+
+    if( dwt_started == 0 )
+    {
+        CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
+        DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
+    }
+
+    return( DWT->CYCCNT );
+}
+
+int mbedtls_hardware_poll( void *data,
+                    unsigned char *output, size_t len, size_t *olen )
+{
+    unsigned long timer = hardclock();
+    ((void) data);
+    *olen = 0;
+
+    if( len < sizeof(unsigned long) )
+        return( 0 );
+
+    memcpy( output, &timer, sizeof(unsigned long) );
+    *olen = sizeof(unsigned long);
+
+    return( 0 );
+}
+
+#endif