samples: Add a sample for runtime chosen image

A sample for runtime chose image on FRDM K64F. It provides implementation
for Zephyr flash_area_open_custom(), so the right flash map
implementation is used, and MCUboot flash_map_id_get_next() and
flash_map_id_get_current() to prioritize sources. It should show what is
expected from an application to be able to use non-flash sources for
images.

In this sample, one can influence from which slot image will be loaded
by pressing a button on the board.

For more details on how to build and test the samples, check the
provided README.md.

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>

boot/zephyr/CMakeLists.txt

@@ -428,6 +428,12 @@ if(CONFIG_BOOT_MAX_IMG_SECTORS_AUTO)
   endif()
 endif()
 
+if(BUILD_RUNTIME_SOURCE_SAMPLE)
+    zephyr_library_sources(
+        ${MCUBOOT_DIR}/samples/runtime-source/zephyr/flash_map_dispatcher.c
+    )
+endif()
+
 if(SYSBUILD)
   if(CONFIG_SINGLE_APPLICATION_SLOT OR CONFIG_BOOT_FIRMWARE_LOADER OR CONFIG_BOOT_SWAP_USING_SCRATCH OR CONFIG_BOOT_SWAP_USING_MOVE OR CONFIG_BOOT_UPGRADE_ONLY OR CONFIG_BOOT_DIRECT_XIP OR CONFIG_BOOT_RAM_LOAD)
     # TODO: RAM LOAD support

boot/zephyr/Kconfig

@@ -332,6 +332,17 @@ config FLASH_RUNTIME_SOURCES
 	  and `flash_map_id_get_next` functions to tell mcuboot where to find
 	  the images.
 
+if FLASH_MAP_CUSTOM_SOURCES
+config AARDVARK_I2C_FLASH
+	bool "Use aardvark to emulate an I2C device from where a firmware image is read"
+	default n
+	depends on I2C
+	help
+	  If you have an I2C device that acts as a flash memory, you can enable this
+	  option to read the firmware image from it.
+
+endif
+
 config BOOT_ENCRYPTION_SUPPORT
 	bool
 	help

boot/zephyr/flash_map_extended.c

@@ -14,6 +14,10 @@
 #include <flash_map_backend/flash_map_backend.h>
 #include <sysflash/sysflash.h>
 
+#if defined(CONFIG_FLASH_RUNTIME_SOURCES)
+#include <flash_runtime_sources.h>
+#endif
+
 #include "bootutil/bootutil_log.h"
 
 BOOT_LOG_MODULE_DECLARE(mcuboot);

samples/runtime-source/zephyr/README.md

@@ -0,0 +1,56 @@
+# Runtime chosen image sample application
+
+This sample demonstrates how to use a non flash storage to retrieve the image
+being booted. It was tested on a FRDM K64F. Both slots are used to store two
+different images. The image to be booted is selected based on a button press.
+
+## Build
+
+Build mcuboot. First, ensure ZEPHYR_SDK_INSTALL_DIR is defined. From the
+mcuboot directory, run the following commands:
+
+```
+  source <path-to-zephyr>/zephyr-env.sh
+
+  west build -p -b frdm_k64f boot/zephyr/ -- -DBUILD_RUNTIME_SOURCE_SAMPLE=1 \
+        -DEXTRA_CONF_FILE="../../samples/runtime-source/zephyr/sample.conf"
+        -DEXTRA_DTC_OVERLAY_FILE=../../samples/runtime-source/zephyr/boards/frdm_k64f.overlay
+
+  west build -t flash
+```
+
+Then, build the sample application to be loaded. We need to build it twice, one
+for each slot. From the sample
+app directory (mcuboot/samples/non-flash-source/zephyr/app), run:
+
+```
+  west build -p -b frdm_k64f .
+  west flash
+```
+
+Then change the overlay file to use the second slot. For instance, open
+`boards/frdm_k64f.overlay` and change the line:
+
+```
+  zephyr,code-partition = &slot0_partition;
+
+```
+
+to:
+
+```
+    zephyr,code-partition = &slot1_partition;
+```
+
+And build and flash again:
+
+```
+  west build -b frdm_k64f .
+  west flash
+```
+
+## Run
+
+Open a serial terminal to see the output and reset the board. It shall boot the
+image on slot0 by default. By keeping the SW2 button pressed during reset, the
+bootloader will randomly select the image to be booted.

samples/runtime-source/zephyr/app/CMakeLists.txt

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(non_flash_backend_app)
+
+if (NOT DEFINED FROM_WHO)
+  set(FROM_WHO Zephyr)
+endif()
+
+target_compile_definitions(app PRIVATE "-DMCUBOOT_HELLO_WORLD_FROM=\"${FROM_WHO}\"")
+
+target_sources(app PRIVATE src/main.c)

samples/runtime-source/zephyr/app/boards/frdm_k64f.overlay

@@ -0,0 +1,5 @@
+/ {
+    chosen {
+        zephyr,code-partition = &slot0_partition;
+    };
+};

samples/runtime-source/zephyr/app/prj.conf

@@ -0,0 +1,3 @@
+CONFIG_BOOTLOADER_MCUBOOT=y
+
+CONFIG_MCUBOOT_SIGNATURE_KEY_FILE="./bootloader/mcuboot/root-rsa-2048.pem"

samples/runtime-source/zephyr/app/src/main.c

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2017 Linaro, Ltd.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/sys/printk.h>
+
+int main(void)
+{
+	printk("Hello World from %s on %s, slot %s!\n",
+	       MCUBOOT_HELLO_WORLD_FROM, CONFIG_BOARD,
+           DT_PROP(DT_CHOSEN(zephyr_code_partition), label));
+}

samples/runtime-source/zephyr/flash_map_dispatcher.c

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2024 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <flash_map_backend/flash_map_backend.h>
+#include <zephyr/drivers/gpio.h>
+#include <zephyr/kernel.h>
+#include <zephyr/random/random.h>
+
+#define SW1_NODE        DT_ALIAS(sw1)
+#if DT_NODE_HAS_STATUS(SW1_NODE, okay)
+static struct gpio_dt_spec sw1_spec = GPIO_DT_SPEC_GET(SW1_NODE, gpios);
+#endif
+
+static int curr_idx = -1;
+
+static uint8_t known_ids[] = {
+	FIXED_PARTITION_ID(slot0_partition),
+	FIXED_PARTITION_ID(slot1_partition),
+};
+
+bool
+flash_map_id_get_next(uint8_t *id, bool reset)
+{
+	if (reset) {
+		curr_idx = 0;
+#if DT_NODE_HAS_STATUS(SW1_NODE, okay)
+		if (gpio_pin_configure_dt(&sw1_spec, GPIO_INPUT) == 0) {
+			if (gpio_pin_get_dt(&sw1_spec) == 1) {
+				curr_idx = sys_rand8_get() % ARRAY_SIZE(known_ids);
+				printk("Booting from curr_idx = %d\n", curr_idx);
+			}
+		}
+#endif
+	} else {
+		curr_idx++;
+	}
+
+	if (curr_idx >= ARRAY_SIZE(known_ids)) {
+		return false;
+	}
+
+	*id = known_ids[curr_idx];
+
+	return true;
+}
+
+bool
+flash_map_id_get_current(uint8_t *id)
+{
+	if (curr_idx == -1 || curr_idx >= ARRAY_SIZE(known_ids)) {
+		return false;
+	}
+
+	*id = known_ids[curr_idx];
+
+	return true;
+}

samples/runtime-source/zephyr/sample.conf

@@ -0,0 +1,4 @@
+CONFIG_FLASH_RUNTIME_SOURCES=y
+CONFIG_BOOT_SIGNATURE_TYPE_RSA=y
+CONFIG_TEST_RANDOM_GENERATOR=y
+CONFIG_ENTROPY_GENERATOR=y