samples: debug: Add a simple gdbstub sample

Sample example built with gdbstub enabled. Two serials are used, one for
normal output and another one that is used talk with gdb in the host
machine.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>

samples/debug/gdbstub/CMakeLists.txt

@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.13.1)
+
+if(BOARD MATCHES "qemu_x86")
+  list(APPEND QEMU_EXTRA_FLAGS -serial tcp:127.0.0.1:1234,server)
+endif()
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(debug)
+
+target_sources(app PRIVATE src/main.c)

samples/debug/gdbstub/README.rst

@@ -0,0 +1,31 @@
+.. _debug_sample:
+
+Debug Sample
+############
+
+Overview
+********
+
+A simple sample that can be used with qemu to show debug using gdb
+remote serial protocol capabilities.
+
+Building and Running
+********************
+
+This application can be built and executed on QEMU as follows:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/debug
+   :host-os: unix
+   :board: qemu_x86
+   :goals: run
+   :compact:
+
+Open a new terminal and use gdb to connect to the running qemu as follows:
+
+.. code-block:: bash
+
+    gdb build/zephyr/zephyr.elf
+    (gdb) target remote :1234
+
+Exit QEMU by pressing :kbd:`CTRL+A` :kbd:`x`.

samples/debug/gdbstub/prj.conf

@@ -0,0 +1,4 @@
+CONFIG_GDBSTUB=y
+CONFIG_GDBSTUB_SERIAL_BACKEND_NAME="UART_1"
+CONFIG_NO_OPTIMIZATIONS=y
+CONFIG_USERSPACE=y

samples/debug/gdbstub/run.gdbinit

@@ -0,0 +1,17 @@
+set pagination off
+symbol-file zephyr/zephyr.elf
+target remote 127.0.0.1:1234
+b test
+b main.c:33
+c
+
+s
+set var a = 2
+c
+if ret == 6
+	printf "PASSED\n"
+	quit 0
+else
+	printf "FAILED\n"
+	quit 1
+end

samples/debug/gdbstub/sample.yaml

@@ -0,0 +1,13 @@
+#
+# Copyright (c) 2020 intel Corporation.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+sample:
+  name: gdbstub sample
+tests:
+  sample.debug.gdbstub:
+    build_only: true
+    platform_allow: qemu_x86
+    tags: debug

samples/debug/gdbstub/src/main.c

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2020 Intel Corporation.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <sys/printk.h>
+
+#define STACKSIZE 512
+
+static int test(void)
+{
+	int a;
+	int b;
+
+	a = 10;
+	b = a * 2;
+
+	return a + b;
+}
+
+static void thread_entry(void *p1, void *p2, void *p3)
+{
+	printk("Hello from user thread!\n");
+}
+
+void main(void)
+{
+	int ret;
+
+	ret = test();
+	printk("%d\n", ret);
+}
+
+K_THREAD_DEFINE(thread, STACKSIZE, thread_entry, NULL, NULL, NULL,
+		7, K_USER, 0);

samples/debug/index.rst

@@ -0,0 +1,10 @@
+.. _debug-samples:
+
+Debug Samples
+#################
+
+.. toctree::
+   :maxdepth: 1
+   :glob:
+
+   **/*

samples/index.rst

@@ -27,6 +27,7 @@ Samples and Demos
    scheduler/*
    smp/*
    tfm_integration/tfm_integration.rst
+   debug/*
 
 .. comment
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