boot: Add flash area ID/device ID retrieval hooks

For users that customise (for instance, via boot_go() hook) from where
images are being loaded from, having those hardcoded to
`slot_partitionX` (when using Zephyr) can be problematic. New hooks,
`flash_area_id_from_multi_image_slot_hook` and
`flash_area_get_device_id_hook` allow some customisation around these
processes.

Support for these hooks is shielded by a different configuration than
other hooks - MCUBOOT_FLASH_AREA_HOOKS, so that it can be enabled
independently from other available hooks.

Support for this new hook was added to the Zephyr port.

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

Author: edersondisouza

boot/bootutil/include/bootutil/boot_hooks.h

@@ -82,6 +82,17 @@
 
 #endif /* MCUBOOT_BOOT_GO_HOOKS  */
 
+#ifdef MCUBOOT_FLASH_AREA_HOOKS
+
+#define BOOT_HOOK_FLASH_AREA_CALL(f, ret_default, ...) \
+    DO_HOOK_CALL(f, ret_default, __VA_ARGS__)
+
+#else
+
+#define BOOT_HOOK_FLASH_AREA_CALL(f, ret_default, ...) \
+    HOOK_CALL_NOP(f, ret_default, __VA_ARGS__)
+
+#endif /* MCUBOOT_FLASH_AREA_ID_HOOKS */
 
 /** Hook for provide image header data.
  *
@@ -215,6 +226,35 @@ int boot_reset_request_hook(bool force);
  */
 fih_ret boot_go_hook(struct boot_rsp *rsp);
 
+/**
+ * Hook to implement custom action before retrieving flash area ID.
+ *
+ * @param image_index the index of the image pair
+ * @param slot slot number
+ * @param area_id the flash area ID to be populated
+ *
+ * @retval 0 the flash area ID was fetched successfully;
+ *         BOOT_HOOK_REGULAR follow the normal execution path to get the flash
+ *         area ID;
+ *         otherwise an error-code value.
+ */
+int flash_area_id_from_multi_image_slot_hook(int image_index, int slot,
+                                             int *area_id);
+
+/**
+ * Hook to implement custom action before retrieving flash area device ID.
+ *
+ * @param fa the flash area structure
+ * @param device_id the device ID to be populated
+ *
+ * @retval 0 the device ID was fetched successfully;
+ *         BOOT_HOOK_REGULAR follow the normal execution path to get the device
+ *         ID;
+ *         otherwise an error-code value.
+ */
+int flash_area_get_device_id_hook(const struct flash_area *fa,
+                                  uint8_t *device_id);
+
 #define BOOT_RESET_REQUEST_HOOK_BUSY		1
 #define BOOT_RESET_REQUEST_HOOK_TIMEOUT		2
 #define BOOT_RESET_REQUEST_HOOK_CHECK_FAILED	3

boot/zephyr/Kconfig

@@ -472,6 +472,17 @@ config BOOT_IMAGE_EXECUTABLE_RAM_SIZE
 	default $(dt_chosen_reg_size_int,$(DT_CHOSEN_Z_SRAM),0)
 endif
 
+config FLASH_RUNTIME_SOURCES
+	bool "Images are read from flash partitions defined at runtime"
+	depends on SINGLE_APPLICATION_SLOT
+	help
+	  Instead of using information on the flash slots to decide which images
+	  to load/update, the application provides the information from which
+	  flash slot to load in runtime. This is useful when the application
+	  reads the state for hardware straps or other sources to decide which
+	  image to load. Usually, application will provide a boot_go_hook() to
+	  decide which image to load.
+
 config BOOT_ENCRYPTION_SUPPORT
 	bool
 	help
@@ -862,6 +873,13 @@ config BOOT_GO_HOOKS
 	  MCUboot's boot_go routine. It is up to the project customization to
 	  add required source files to the build.
 
+config BOOT_FLASH_AREA_HOOKS
+	bool "Enable hooks for overriding MCUboot's flash area routines"
+	help
+	  Allow to provide procedures for override or extend native
+	  MCUboot's flash area routines. It is up to the project customization to
+	  add required source files to the build.
+
 config MCUBOOT_ACTION_HOOKS
 	bool "Enable hooks for responding to MCUboot status changes"
 	help

boot/zephyr/flash_map_extended.c

@@ -14,7 +14,9 @@
 #include <flash_map_backend/flash_map_backend.h>
 #include <sysflash/sysflash.h>
 
+#include "bootutil/boot_hooks.h"
 #include "bootutil/bootutil_log.h"
+#include "bootutil/bootutil_public.h"
 
 BOOT_LOG_MODULE_DECLARE(mcuboot);
 
@@ -58,6 +60,14 @@ int flash_device_base(uint8_t fd_id, uintptr_t *ret)
  */
 int flash_area_id_from_multi_image_slot(int image_index, int slot)
 {
+    int rc, id;
+
+    rc = BOOT_HOOK_FLASH_AREA_CALL(flash_area_id_from_multi_image_slot_hook,
+                                   BOOT_HOOK_REGULAR, image_index, slot, &id);
+    if (rc != BOOT_HOOK_REGULAR) {
+        return id;
+    }
+
     switch (slot) {
     case 0: return FLASH_AREA_IMAGE_PRIMARY(image_index);
 #if !defined(CONFIG_SINGLE_APPLICATION_SLOT)
@@ -138,6 +148,15 @@ int flash_area_sector_from_off(off_t off, struct flash_sector *sector)
 
 uint8_t flash_area_get_device_id(const struct flash_area *fa)
 {
+    uint8_t device_id;
+    int rc;
+
+    rc = BOOT_HOOK_FLASH_AREA_CALL(flash_area_get_device_id_hook,
+                                   BOOT_HOOK_REGULAR, fa, &device_id);
+    if (rc != BOOT_HOOK_REGULAR) {
+        return device_id;
+    }
+
 #if defined(CONFIG_ARM)
     return fa->fa_id;
 #else

boot/zephyr/include/mcuboot_config/mcuboot_config.h

@@ -246,6 +246,10 @@
 #define MCUBOOT_BOOT_GO_HOOKS
 #endif
 
+#ifdef CONFIG_BOOT_FLASH_AREA_HOOKS
+#define MCUBOOT_FLASH_AREA_HOOKS
+#endif
+
 #ifdef CONFIG_MCUBOOT_VERIFY_IMG_ADDRESS
 #define MCUBOOT_VERIFY_IMG_ADDRESS
 #endif