zephyr: Add estimated image footer size to cache in sysbuild

Adds MCUboot's estimated overhead footer size to the application's
cache when using sysbuild, this allows that information to be
propagated to applications which can use the information to reduce
the available size for an application, preventing the MCUboot
error of image too large to swap.

Signed-off-by: Jamie McCrae <[email protected]>

boot/zephyr/CMakeLists.txt

@@ -365,6 +365,75 @@ if(CONFIG_BOOT_ENCRYPTION_KEY_FILE AND NOT CONFIG_BOOT_ENCRYPTION_KEY_FILE STREQ
   zephyr_library_sources(${GENERATED_ENCKEY})
 endif()
 
+function(mathup num align result)
+  math(EXPR out "(((${num}) + ((${align}) - 1)) & ~((${align}) - 1))")
+  set(${result} "${out}" PARENT_SCOPE)
+endfunction()
+
+if(SYSBUILD)
+  if(CONFIG_BOOT_SWAP_USING_SCRATCH OR CONFIG_BOOT_SWAP_USING_MOVE OR CONFIG_BOOT_UPGRADE_ONLY OR CONFIG_BOOT_DIRECT_XIP OR CONFIG_BOOT_RAM_LOAD)
+    dt_chosen(chosen_flash PROPERTY "zephyr,flash")
+    dt_prop(erase_size PATH "${chosen_flash}" PROPERTY "erase-block-size")
+    dt_prop(write_size PATH "${chosen_flash}" PROPERTY "write-block-size")
+
+    if(write_size LESS 8)
+      set(write_size 8)
+    endif()
+
+    set(key_size 0)
+
+    if(CONFIG_BOOT_ENCRYPT_RSA OR CONFIG_BOOT_ENCRYPT_EC256 OR CONFIG_BOOT_ENCRYPT_X25519)
+#ifdef MCUBOOT_AES_256
+#set(BOOT_ENC_KEY_SIZE 32)
+#else
+      set(BOOT_ENC_KEY_SIZE 16)
+#endif
+
+      if(CONFIG_BOOT_SWAP_SAVE_ENCTLV)
+        if(CONFIG_BOOT_ENCRYPT_RSA)
+          set(key_size 256)
+        elseif(CONFIG_BOOT_ENCRYPT_EC256)
+          math(EXPR key_size "65 + 32 + ${BOOT_ENC_KEY_SIZE}")
+        elseif(CONFIG_BOOT_ENCRYPT_X25519)
+          math(EXPR key_size "32 + 32 + ${BOOT_ENC_KEY_SIZE}")
+        else()
+          math(EXPR key_size "${BOOT_ENC_KEY_SIZE} + 8")
+        endif()
+      else()
+        set(key_size "${BOOT_ENC_KEY_SIZE}")
+      endif()
+
+      mathup(${key_size} ${write_size} key_size)
+      math(EXPR key_size "${key_size} * 2")
+    endif()
+
+    set(boot_magic_size 16)
+    mathup(${boot_magic_size} ${write_size} boot_magic_size)
+
+    math(EXPR boot_swap_data_size "${write_size} * 4")
+
+    if(CONFIG_BOOT_SWAP_USING_SCRATCH OR CONFIG_BOOT_SWAP_USING_MOVE)
+      math(EXPR boot_status_data_size "${CONFIG_BOOT_MAX_IMG_SECTORS} * (3 * ${write_size})")
+    else()
+      set(boot_status_data_size 0)
+    endif()
+
+# 352 is rough for trailer TLV
+    math(EXPR required_size "${key_size} + ${boot_magic_size} + ${boot_swap_data_size} + ${boot_status_data_size} + 352")
+
+    mathup(${required_size} ${erase_size} required_size)
+
+    if(CONFIG_BOOT_SWAP_USING_MOVE)
+      math(EXPR required_size "${required_size} + ${erase_size}")
+    endif()
+  else()
+    set(required_size 0)
+  endif()
+
+message(WARNING "required size: ${required_size}")
+  set(mcuboot_image_footer_size ${required_size} CACHE INTERNAL "" FORCE)
+endif()
+
 if(CONFIG_MCUBOOT_CLEANUP_ARM_CORE)
 zephyr_library_sources(
   ${BOOT_DIR}/zephyr/arm_cleanup.c

boot/zephyr/sysbuild/CMakeLists.txt

@@ -0,0 +1,40 @@
+function(mathup num align result)
+  math(EXPR out "(((${num}) + ((${align}) - 1)) & ~((${align}) - 1))")
+  set(${result} "${out}" PARENT_SCOPE)
+endfunction()
+
+function(${SYSBUILD_CURRENT_MODULE_NAME}_pre_image_cmake)
+  cmake_parse_arguments(POST_IMAGE_CMAKE "" "IMAGE" "IMAGES" ${ARGN})
+
+  if(NOT "${POST_IMAGE_CMAKE_IMAGE}" STREQUAL "mcuboot")
+    return()
+  endif()
+
+  set_property(
+    DIRECTORY APPEND PROPERTY
+    CMAKE_CONFIGURE_DEPENDS
+    ${CMAKE_BINARY_DIR}/mcuboot/CMakeCache.txt
+    ${CMAKE_BINARY_DIR}/mcuboot/zephyr/.config
+    )
+endfunction(${SYSBUILD_CURRENT_MODULE_NAME}_pre_image_cmake)
+
+function(${SYSBUILD_CURRENT_MODULE_NAME}_post_image_cmake)
+  cmake_parse_arguments(POST_IMAGE_CMAKE "" "IMAGE" "IMAGES" ${ARGN})
+
+  if(NOT "${POST_IMAGE_CMAKE_IMAGE}" STREQUAL "mcuboot")
+    return()
+  endif()
+
+  foreach(image ${IMAGES})
+    set(app_type)
+    get_property(app_type TARGET ${image} PROPERTY APP_TYPE)
+
+    if("${app_type}" STREQUAL "MAIN")
+      sysbuild_get(mcuboot_image_footer_size IMAGE mcuboot CACHE)
+      math(EXPR mcuboot_image_footer_size "${mcuboot_image_footer_size}" OUTPUT_FORMAT HEXADECIMAL)
+
+      set_property(TARGET ${image} APPEND_STRING PROPERTY CONFIG "CONFIG_FLASH_LOAD_OVERHEAD_SIZE=${mcuboot_image_footer_size}\n")
+      return()
+    endif()
+  endforeach()
+endfunction(${SYSBUILD_CURRENT_MODULE_NAME}_post_image_cmake)

zephyr/module.yml

@@ -2,3 +2,4 @@ samples:
   - boot/zephyr
 build:
   cmake: ./boot/bootutil/zephyr
+  sysbuild-cmake: boot/zephyr/sysbuild