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Use Freescale's RNGA on the K64F

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Manuel Pégourié-Gonnard 2015-08-18 13:33:14 +02:00 committed by Simon Butcher
parent 6eaf3659ea
commit 0e4d9afa61
2 changed files with 49 additions and 26 deletions
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69
yotta/data/entropy_hardware_poll.c
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@ -1,5 +1,5 @@
/*
* Temporary "entropy" collector for Cortex-M4
* 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
@ -20,46 +20,69 @@
*/
/*
* 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
* WARNING: this is temporary!
* This should be in a separate yotta module which would be a target
* dependency of mbedtls (see IOTSSL-313)
*/
#if defined(TARGET_LIKE_CORTEX_M4)
#if defined(TARGET_LIKE_K64F)
#include "MK64F12.h"
#include "core_cm4.h"
#include <string.h>
/*
* Reference: "K64 Sub-Family Reference Manual, Rev. 2", chapter 34
*/
unsigned long hardclock( void )
#include "fsl_clock_manager.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 )
{
static int dwt_started = 0;
size_t bit;
if( dwt_started == 0 )
/* 34.5 Steps 3-4-5: poll SR and read from OR when ready */
for( bit = 0; bit < 8; bit++ )
{
CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
while( ( RNG->SR & RNG_SR_OREG_LVL_MASK ) == 0 );
*byte |= ( RNG->OR & 1 ) << bit;
}
return( DWT->CYCCNT );
}
/*
* Get len bytes of entropy from the hardware RNG.
*/
int mbedtls_hardware_poll( void *data,
unsigned char *output, size_t len, size_t *olen )
{
unsigned long timer = hardclock();
size_t i;
int ret;
((void) data);
*olen = 0;
if( len < sizeof(unsigned long) )
return( 0 );
CLOCK_SYS_EnableRngaClock( 0 );
memcpy( output, &timer, sizeof(unsigned long) );
*olen = sizeof(unsigned long);
/* 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;
return( 0 );
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_SYS_DisableRngaClock( 0 );
return( ret );
}
#endif

6
yotta/data/target_config.h
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@ -26,10 +26,10 @@
#endif
/*
* WARNING: this is a temporary hack!
* 2. This should be in a separete yotta module which would be a target
* WARNING: this is temporary!
* This should be in a separate yotta module which would be a target
* dependency of mbedtls (see IOTSSL-313)
*/
#if defined(TARGET_LIKE_CORTEX_M4)
#if defined(TARGET_LIKE_K64F)
#define MBEDTLS_ENTROPY_HARDWARE_ALT
#endif