mbedtls: Add an alt implementation of timing

Implement the MBEDTLS_TIMING_ALT interface for Mbed OS. This
implementation is sufficient to run the Mbed TLS benchmarking
application.

connectivity/mbedtls/CMakeLists.txt

@@ -16,6 +16,7 @@ target_sources(mbed-mbedtls
         platform/src/mbed_trng.cpp
         platform/src/platform_alt.cpp
         platform/src/shared_rng.cpp
+        platform/src/timing.cpp
 
         source/aes.c
         source/aesni.c

connectivity/mbedtls/include/mbedtls/check_config.h

@@ -55,9 +55,8 @@
 #endif
 #endif /* _WIN32 */
 
-#if defined(TARGET_LIKE_MBED) && \
-    ( defined(MBEDTLS_NET_C) || defined(MBEDTLS_TIMING_C) )
-#error "The NET and TIMING modules are not available for mbed OS - please use the network and timing functions provided by mbed OS"
+#if defined(TARGET_LIKE_MBED) && defined(MBEDTLS_NET_C)
+#error "The NET module is not available for mbed OS - please use the network functions provided by mbed OS"
 #endif
 
 #if defined(MBEDTLS_DEPRECATED_WARNING) && \

connectivity/mbedtls/platform/inc/timing_alt.h

@@ -0,0 +1,42 @@
+/*
+ *  timing_alt.h
+ *
+ *  Copyright (C) 2021, 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.
+ *
+ */
+
+#ifndef TIMING_ALT_H
+#define TIMING_ALT_H
+
+#include "mbedtls/timing.h"
+#if defined(MBEDTLS_TIMING_ALT)
+
+#include <time.h>
+
+struct mbedtls_timing_hr_time
+{
+    struct timeval start;
+};
+
+typedef struct mbedtls_timing_delay_context
+{
+    struct mbedtls_timing_hr_time   timer;
+    uint32_t                        int_ms;
+    uint32_t                        fin_ms;
+} mbedtls_timing_delay_context;
+
+#endif
+#endif

connectivity/mbedtls/platform/src/timing.cpp

@@ -0,0 +1,67 @@
+/*
+ *  timing.cpp
+ *
+ *  Copyright (C) 2021, 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.
+ *
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+#include "mbedtls/timing.h"
+#include "drivers/Timeout.h"
+#include <chrono>
+
+extern "C" {
+    volatile int mbedtls_timing_alarmed = 0;
+};
+
+static void handle_alarm(void)
+{
+    mbedtls_timing_alarmed = 1;
+}
+
+extern "C" void mbedtls_set_alarm(int seconds)
+{
+    static mbed::Timeout t;
+    mbedtls_timing_alarmed = 0;
+
+    t.attach(handle_alarm, std::chrono::seconds(seconds));
+}
+
+#if !defined(HAVE_HARDCLOCK)
+#define HAVE_HARDCLOCK
+#include "platform/mbed_rtc_time.h"
+static int hardclock_init = 0;
+static struct timeval tv_init;
+
+extern "C" unsigned long mbedtls_timing_hardclock(void)
+{
+    struct timeval tv_cur;
+
+    if (hardclock_init == 0)
+    {
+        gettimeofday(&tv_init, NULL);
+        hardclock_init = 1;
+    }
+
+    gettimeofday(&tv_cur, NULL);
+    return((tv_cur.tv_sec - tv_init.tv_sec) * 1000000
+          + (tv_cur.tv_usec - tv_init.tv_usec));
+}
+#endif /* !HAVE_HARDCLOCK */