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/*
* 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.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
/*
* 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_K64F)
/*
* Reference: "K64 Sub-Family Reference Manual, Rev. 2", chapter 34
*/
#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 )
{
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_SYS_EnableRngaClock( 0 );
/* 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_SYS_DisableRngaClock( 0 );
return( ret );
}
#endif
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