53 lines
1.1 KiB
C
53 lines
1.1 KiB
C
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/*
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* Temporary "entropy" collector for Cortex-M4
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*
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* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*/
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/*
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* WARNING: this is a temporary hack!
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* 1. Currently does not provide strong entropy, should be replaced to use the
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* on-board hardware RNG (see IOTSSL-303)
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* 2. This should be in a separete yotta module which would be a target
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* dependency of mbedtls (see IOTSSL-313)
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*/
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#if defined(TARGET_LIKE_CORTEX_M4)
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#include "MK64F12.h"
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#include "core_cm4.h"
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#include <string.h>
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unsigned long hardclock( void )
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{
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static int dwt_started = 0;
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if( dwt_started == 0 )
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{
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CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
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DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
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}
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return( DWT->CYCCNT );
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}
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int mbedtls_hardware_poll( void *data,
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unsigned char *output, size_t len, size_t *olen )
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{
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unsigned long timer = hardclock();
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((void) data);
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*olen = 0;
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if( len < sizeof(unsigned long) )
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return( 0 );
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memcpy( output, &timer, sizeof(unsigned long) );
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*olen = sizeof(unsigned long);
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return( 0 );
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}
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#endif
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