samples: Add a sample for runtime chosen image

A sample for runtime chose image on FRDM K64F. It provides implementation
for boot_go and flash area id related hooks, showing how an external
module implementing hooks can influence which images end up being booted
on the platform.

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 <[email protected]>
Signed-off-by: Tom Burdick <[email protected]>

samples/runtime-source/zephyr/README.md

@@ -0,0 +1,55 @@
+# 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
+sample directory, run the following commands:
+
+```
+  source <path-to-zephyr>/zephyr-env.sh
+
+  west build -p -b frdm_k64f ../../../boot/zephyr/ -- \
+      -DEXTRA_ZEPHYR_MODULES=$PWD/hooks -DEXTRA_CONF_FILE="$PWD/sample.conf
+
+  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 boot the one on slot1.

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 = &slot1_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/hooks/CMakeLists.txt

@@ -0,0 +1,3 @@
+zephyr_library()
+zephyr_library_sources(hooks.c)
+zephyr_library_link_libraries(MCUBOOT_BOOTUTIL)

samples/runtime-source/zephyr/hooks/hooks.c

@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2024 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/drivers/gpio.h>
+#include <zephyr/kernel.h>
+
+#include "bootutil/bootutil.h"
+#include "bootutil/bootutil_public.h"
+#include "bootutil/fault_injection_hardening.h"
+
+#define BOOT_TMPBUF_SZ 256
+
+static const struct flash_area *_fa_p;
+static struct image_header _hdr;
+static uint8_t tmpbuf[BOOT_TMPBUF_SZ];
+
+static uint8_t known_ids[] = {
+    FIXED_PARTITION_ID(slot0_partition),
+    FIXED_PARTITION_ID(slot1_partition),
+};
+
+static int current_id;
+
+#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
+
+fih_ret boot_go_hook(struct boot_rsp *rsp)
+{
+    int rc;
+#ifdef MCUBOOT_RAM_LOAD
+    struct boot_loader_state *state;
+#endif
+    FIH_DECLARE(fih_rc, FIH_FAILURE);
+
+    current_id = 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) {
+            current_id = ARRAY_SIZE(known_ids) - 1;
+            printk("%s pressed, forcing boot from partition %u\n",
+                   sw1_spec.port->name, known_ids[current_id]);
+        } else {
+            printk("%s not pressed, looping partitions to boot\n",
+                   sw1_spec.port->name);
+        }
+    }
+#else
+    printk("SW1 not defined, looping partitions to boot\n");
+#endif
+
+    for ( ; current_id < ARRAY_SIZE(known_ids); current_id++) {
+        printk("Trying to boot from fixed partition %u\n",
+               known_ids[current_id]);
+
+        rc = flash_area_open(known_ids[current_id], &_fa_p);
+        if (rc != 0) {
+            continue;
+        }
+
+        rc = boot_image_load_header(_fa_p, &_hdr);
+        if (rc != 0) {
+            flash_area_close(_fa_p);
+            continue;
+        }
+
+#ifdef MCUBOOT_RAM_LOAD
+        state = boot_get_loader_state();
+
+        rc = boot_load_image_from_flash_to_sram(state, &_hdr);
+        if (rc != 0) {
+            flash_area_close(_fa_p);
+            continue;
+        }
+#endif
+
+        FIH_CALL(bootutil_img_validate, fih_rc, NULL, 0, &_hdr, _fa_p, tmpbuf,
+                BOOT_TMPBUF_SZ, NULL, 0, NULL);
+        if (FIH_NOT_EQ(fih_rc, FIH_SUCCESS)) {
+            flash_area_close(_fa_p);
+#ifdef MCUBOOT_RAM_LOAD
+            boot_remove_image_from_sram(state);
+#endif
+            continue;
+        }
+
+        rsp->br_flash_dev_id = flash_area_get_device_id(_fa_p);
+        rsp->br_image_off = flash_area_get_off(_fa_p);
+        rsp->br_hdr = &_hdr;
+
+        flash_area_close(_fa_p);
+        break;
+    }
+
+    FIH_RET(fih_rc);
+}
+
+int flash_area_id_from_multi_image_slot_hook(int image_index, int slot,
+        int *area_id)
+{
+    *area_id = known_ids[current_id];
+
+    return 0;
+}
+
+int flash_area_get_device_id_hook(const struct flash_area *fa, uint8_t *dev_id)
+{
+    *dev_id = fa->fa_id;
+
+    return 0;
+}

samples/runtime-source/zephyr/hooks/zephyr/module.yml

@@ -0,0 +1,3 @@
+name: testmod
+build:
+  cmake: .

samples/runtime-source/zephyr/sample.conf

@@ -0,0 +1,8 @@
+CONFIG_FLASH_RUNTIME_SOURCES=y
+CONFIG_SINGLE_APPLICATION_SLOT=y
+CONFIG_BOOT_SIGNATURE_TYPE_RSA=y
+CONFIG_TEST_RANDOM_GENERATOR=y
+CONFIG_ENTROPY_GENERATOR=y
+
+CONFIG_BOOT_GO_HOOKS=y
+CONFIG_BOOT_FLASH_AREA_HOOKS=y