Use Freescale's RNGA on the K64F
diff --git a/yotta/data/entropy_hardware_poll.c b/yotta/data/entropy_hardware_poll.c
index 1924302..3a61e22 100644
--- a/yotta/data/entropy_hardware_poll.c
+++ b/yotta/data/entropy_hardware_poll.c
@@ -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
diff --git a/yotta/data/target_config.h b/yotta/data/target_config.h
index df1a208..f350ce3 100644
--- a/yotta/data/target_config.h
+++ b/yotta/data/target_config.h
@@ -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