zephyr: Add support for slot selection boot hook

Add a Kconfig option to enable a bootloader hook to alter
the logic of the active slot selection in Direct XIP modes.

Signed-off-by: Tomasz Chyrowicz <[email protected]>

Author: tomchy

boot/zephyr/Kconfig

@@ -1096,6 +1096,14 @@ config MCUBOOT_ACTION_HOOKS
 	  'mcuboot_status_type_t' is listed in
 	  boot/bootutil/include/bootutil/mcuboot_status.h
 
+config FIND_NEXT_SLOT_HOOKS
+	bool "Enable hooks for finding the next active slot"
+	help
+	  This will call a handler when the MCUboot searches for the best slot
+	  for an image. By default, a slot with the highest version is selected.
+	  This hook allows to override this logic and provide a custom slot
+	  selection policy.
+
 config BOOT_DISABLE_CACHES
 	bool "Disable I/D caches before chain-loading application"
 	depends on CPU_HAS_ICACHE || CPU_HAS_DCACHE

boot/zephyr/hooks_sample.c

@@ -93,3 +93,8 @@ int boot_img_install_stat_hook(int image_index, int slot, int *img_install_stat)
 {
     return BOOT_HOOK_REGULAR;
 }
+
+int boot_find_next_slot_hook(struct boot_loader_state *state, uint8_t image, uint32_t *active_slot)
+{
+    return BOOT_HOOK_REGULAR;
+}

boot/zephyr/include/mcuboot_config/mcuboot_config.h

@@ -278,6 +278,10 @@
 #define MCUBOOT_FLASH_AREA_HOOKS
 #endif
 
+#ifdef CONFIG_FIND_NEXT_SLOT_HOOKS
+#define MCUBOOT_FIND_NEXT_SLOT_HOOKS
+#endif
+
 #ifdef CONFIG_MCUBOOT_VERIFY_IMG_ADDRESS
 #define MCUBOOT_VERIFY_IMG_ADDRESS
 #endif