esp32: Adds gcov over JTAG feature

Implements function to dump GCOV data to host via JTAG.
The following functionality was added:
 - Host file I/O
 - GCOV runtime I/O stubs
 - GCOV example

components/app_trace/gcov/gcov_rtio.c

@@ -0,0 +1,93 @@
+// Copyright 2017 Espressif Systems (Shanghai) PTE LTD
+//
+// 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 module implements runtime file I/O API for GCOV.
+
+#include "esp_task_wdt.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "soc/cpu.h"
+#include "soc/timer_group_struct.h"
+#include "soc/timer_group_reg.h"
+#include "esp_app_trace.h"
+
+#if CONFIG_ESP32_APPTRACE_ENABLE
+
+#define LOG_LOCAL_LEVEL CONFIG_LOG_DEFAULT_LEVEL
+#include "esp_log.h"
+const static char *TAG = "esp_gcov_rtio";
+
+static void (*s_gcov_exit)(void);
+static uint8_t s_gcov_down_buf[256];
+
+void esp_gcov_dump()
+{
+#if CONFIG_FREERTOS_UNICORE == 0
+    esp_cpu_stall(!xPortGetCoreID());
+#endif
+
+    while (!esp_apptrace_host_is_connected(ESP_APPTRACE_DEST_TRAX)) {
+        // to avoid complains that task watchdog got triggered for other tasks
+        TIMERG0.wdt_wprotect=TIMG_WDT_WKEY_VALUE;
+        TIMERG0.wdt_feed=1;
+        TIMERG0.wdt_wprotect=0;
+        // to avoid reboot on INT_WDT
+        TIMERG1.wdt_wprotect=TIMG_WDT_WKEY_VALUE;
+        TIMERG1.wdt_feed=1;
+        TIMERG1.wdt_wprotect=0;
+    }
+
+    if (s_gcov_exit) {
+        s_gcov_exit();
+    }
+
+    int ret = esp_apptrace_fstop(ESP_APPTRACE_DEST_TRAX);
+    if (ret != ESP_OK) {
+        ESP_LOGE(TAG, "Failed to send files transfer stop cmd (%d)!\n", ret);
+    }
+}
+
+int gcov_rtio_atexit(void (*function)(void))
+{
+    s_gcov_exit = function;
+    esp_apptrace_down_buffer_config(s_gcov_down_buf, sizeof(s_gcov_down_buf));
+    return 0;
+}
+
+void *gcov_rtio_fopen(const char *path, const char *mode)
+{
+    return esp_apptrace_fopen(ESP_APPTRACE_DEST_TRAX, path, mode);
+}
+
+int gcov_rtio_fclose(void *stream)
+{
+    return esp_apptrace_fclose(ESP_APPTRACE_DEST_TRAX, stream);
+}
+
+size_t gcov_rtio_fwrite(const void *ptr, size_t size, size_t nmemb, void *stream)
+{
+    return esp_apptrace_fwrite(ESP_APPTRACE_DEST_TRAX, ptr, size, nmemb, stream);
+}
+
+int gcov_rtio_fseek(void *stream, long offset, int whence)
+{
+    return esp_apptrace_fseek(ESP_APPTRACE_DEST_TRAX, stream, offset, whence);
+}
+
+long gcov_rtio_ftell(void *stream)
+{
+    return esp_apptrace_ftell(ESP_APPTRACE_DEST_TRAX, stream);
+}
+
+#endif