mbedtls/yotta/data/entropy_hardware_poll.c
2015-08-06 09:57:53 +02:00

53 lines
1.1 KiB
C

/*
* Temporary "entropy" collector for Cortex-M4
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
*
* 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