Add reference counter for platform context

1. Move the `mbedtls_platform_context` to be platform code, in `features/mbedtls/platfrom/`.
2. Add static refernce counter, to setup and teardown the platform code only once.
3. Adjust Cryptocell porting accordingly.

Author: Ron Eldor

features/cryptocell/FEATURE_CRYPTOCELL310/Readme.md

@@ -16,6 +16,6 @@ To port your CC 310 driver to Mbed OS on your specific target, do the following:
 1. In `objects.h`, include `objects_cryptocell.h`. You can use the `FEATURE_CRYPTOCELL310` precompilation check as defined above.
 1. In `features/cryptocell/FEATURE_CRYPTOCELL310/TARGET_<target name>`, add your platform-specific libraries for all toolchains in `TOOLCHAIN_ARM`, `TOOLCHAIN_GCC_ARM` and `TOOLCHAIN_IAR` respectively.
 1. Add your CC setup code:
-	* Implement `cc_platform_setup()` and `cc_platform_terminate()` to enable CC on your platform, in case you have board-specific setup functionality, required for CC setup. These functions can be empty.
-	* Define `cc_platform_ctx` in `cc_platform.h` in a way that suits your implementation.
+	* Implement `crypto_platform_setup()` and `crypto_platform_terminate()` to enable CC on your platform, in case you have board-specific setup functionality, required for CC setup. You MUST call 'SaSi_LibInit()` and 'SaSi_LibFini()' respectively in these functions.
+	* Define `crypto_platform_ctx` in `crypto_platform.h` in a way that suits your implementation.
 

features/cryptocell/FEATURE_CRYPTOCELL310/TARGET_MCU_NRF52840/cc_platform_nrf52840.c

@@ -1,5 +1,5 @@
  /*
-  *  platform_alt.c
+  *  crypto_platform.c
   *
   *  Copyright (C) 2018, Arm Limited, All Rights Reserved
   *  SPDX-License-Identifier: Apache-2.0
@@ -18,40 +18,31 @@
   *
   */
 
-#include "mbedtls/platform.h"
-#if defined(MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT)
+#include "platform_alt.h"
+#include "nrf52840.h"
 #include "sns_silib.h"
-
+#if defined(MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT)
 /* once https://github.com/ARMmbed/mbedtls/issues/1200 will be supported,
  * rndState should be part of mbedtls_platform_context
  * Until then, we should keep it global and extern */
 
 CRYS_RND_State_t     rndState = { { 0 } } ;
 CRYS_RND_WorkBuff_t  rndWorkBuff = { { 0 } } ;
 
-
-int mbedtls_platform_setup( mbedtls_platform_context *ctx )
+int crypto_platform_setup( crypto_platform_ctx *ctx )
 {
-    int ret = 0;
-    if( ctx == NULL )
-        return ( -1 );
-
-    /* call platform specific code to setup CC driver*/
-    if( ( ret = cc_platform_setup( &ctx->platform_impl_ctx ) ) != 0 )
-        return ( ret );
+    NRF_CRYPTOCELL->ENABLE = 1;
 
     if( SaSi_LibInit( &rndState, &rndWorkBuff ) != 0 )
-        return ( -1 );
+          return ( -1 );
+
     return ( 0 );
 }
 
-void mbedtls_platform_teardown( mbedtls_platform_context *ctx )
+void crypto_platform_terminate( crypto_platform_ctx *ctx )
 {
-    if( ctx == NULL )
-        return;
-
     SaSi_LibFini( &rndState );
-    cc_platform_terminate( &ctx->platform_impl_ctx );
+    NRF_CRYPTOCELL->ENABLE = 0;
 }
 
-#endif /* MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT*/
+#endif /* MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT */

features/cryptocell/FEATURE_CRYPTOCELL310/platform_alt.c renamed to features/cryptocell/FEATURE_CRYPTOCELL310/TARGET_MCU_NRF52840/crypto_platform.c

@@ -19,6 +19,7 @@
   */
 #ifndef __CC_PLATFORM_H_
 #define __CC_PLATFORM_H_
+#if defined(MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT)
 /**
  * \brief   The CC platform context structure.
  *
@@ -27,7 +28,10 @@
  */
 typedef struct {
     char dummy; /**< Placeholder member, as empty structs are not portable. */
+    /*
+     * Add CRYS_RND_State_t rndState; when https://github.com/ARMmbed/mbedtls/issues/1200 is supported
+     */
 }
-cc_platform_ctx;
-
+crypto_platform_ctx;
+#endif /* MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT */
 #endif /* __CC_PLATFORM_H_ */

features/cryptocell/FEATURE_CRYPTOCELL310/TARGET_MCU_NRF52840/cc_platform.h renamed to features/cryptocell/FEATURE_CRYPTOCELL310/TARGET_MCU_NRF52840/crypto_platform.h

@@ -20,8 +20,9 @@
 
 #ifndef __PLATFORM_ALT__
 #define __PLATFORM_ALT__
-#include "cc_platform.h"
-#include "crys_rnd.h"
+#include "platform_mbed.h"
+#if defined(MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT)
+#include "crypto_platform.h"
 
 /**
  * \brief   The platform context structure.
@@ -30,40 +31,37 @@
  *          setup or teardown operations.
  */
 typedef struct {
-    cc_platform_ctx platform_impl_ctx; /** A context holding all the partner's platform specific context */
-    /*
-     * Add CRYS_RND_State_t rndState; when https://github.com/ARMmbed/mbedtls/issues/1200 is supported
-     * */
+    crypto_platform_ctx platform_impl_ctx; /* A context holding all the platform specific context for cryptography. Should be defined in crypto_platform.h */
 }
 mbedtls_platform_context;
 
 
+void mbedtls_platform_init( mbedtls_platform_context* ctx);
 /**
- * \brief   This function performs any partner platform initialization operations,
- *          needed top enable CryptoCell.
+ * \brief   This function performs any platform initialization operations,
+ *          needed for setting up cryptographic modules.
  *
  * \param   ctx     The platform specific context.
  *
  * \return          \c 0 on success.
  *
- * \note    This function is intended to allow platform-specific initialization for CryptoCell,
- *          and is called before initializing the CC library(SaSi_LibInit). Its
+ * \note    This function is intended to allow platform-specific initialization for Mbed TLS,
+ *          and is called before initializing the Mbed TLS functions. Its
  *          implementation is platform-specific, and its implementation MUST be provided.
  *
  */
-int cc_platform_setup( cc_platform_ctx *ctx );
+int crypto_platform_setup( crypto_platform_ctx *ctx );
 
 /**
- * \brief   This function performs any partner platform teardown operations, to disable CryptoCell.
+ * \brief   This function performs any  platform teardown operations, to disable cryptographic operations.
  *
  * \param   ctx     The platform specific context.
  *
- * \note    This function is called after terminating CC library(SaSi_LibFini)
- *          and intended to free any resource used for CryptoCell by the platform.
+ * \note    This function is intended to free any resource used Mbed TLS by the platform.
  *          Its implementation is platform-specific,and its implementation MUST be provided.
  *
  */
-void cc_platform_terminate( cc_platform_ctx *ctx );
-
+void crypto_platform_terminate( crypto_platform_ctx *ctx );
+#endif
 #endif /* __PLATFORM_ALT__ */
 

features/cryptocell/FEATURE_CRYPTOCELL310/platform_alt.h renamed to features/mbedtls/platform/inc/platform_alt.h

@@ -0,0 +1,59 @@
+ /*
+  *  platform_alt.c
+  *
+  *  Copyright (C) 2018, 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.
+  *
+  */
+
+#include "mbedtls/platform.h"
+#if defined(MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT)
+
+static int reference_count = 0;
+
+int mbedtls_platform_setup( mbedtls_platform_context *ctx )
+{
+    int ret = 0;
+    if( ctx == NULL )
+        return ( -1 );
+
+    reference_count++;
+
+    if( reference_count == 1 )
+    {
+        /* call platform specific code to setup crypto driver*/
+        ret = crypto_platform_setup( &ctx->platform_impl_ctx );
+    }
+    return ( ret );
+}
+
+void mbedtls_platform_teardown( mbedtls_platform_context *ctx )
+{
+    if( ctx == NULL )
+        return;
+
+    if( reference_count == 0 )
+        return;
+
+    reference_count--;
+
+    if( reference_count == 0 )
+    {
+        /* call platform specific code to terminate crypto driver*/
+        crypto_platform_terminate( &ctx->platform_impl_ctx );
+    }
+}
+
+#endif /* MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT*/