boot: zephyr: add support for revert mode with ramload

Add support for revert mode when using ramloading. This includes the
same restrictions as revert mode with direct-xip, namely that an image
must have a valid BOOT_MAGIC value in order for mcuboot to attempt to
load it.

Signed-off-by: Daniel DeGrasse <ddegrasse@tenstorrent.com>

Author: danieldegrasse

boot/bootutil/src/bootutil_priv.h

@@ -285,7 +285,8 @@ struct boot_loader_state {
         /* Image destination and size for the active slot */
         uint32_t img_dst;
         uint32_t img_sz;
-#elif defined(MCUBOOT_DIRECT_XIP_REVERT)
+#endif
+#if defined(MCUBOOT_DIRECT_XIP_REVERT) || defined(MCUBOOT_RAM_LOAD_REVERT)
         /* Swap status for the active slot */
         struct boot_swap_state swap_state;
 #endif

boot/bootutil/src/loader.c

@@ -2605,7 +2605,8 @@ print_loaded_images(struct boot_loader_state *state)
 }
 #endif
 
-#if defined(MCUBOOT_DIRECT_XIP) && defined(MCUBOOT_DIRECT_XIP_REVERT)
+#if (defined(MCUBOOT_DIRECT_XIP) && defined(MCUBOOT_DIRECT_XIP_REVERT)) || \
+    (defined(MCUBOOT_RAM_LOAD) && defined(MCUBOOT_RAM_LOAD_REVERT))
 /**
  * Checks whether the active slot of the current image was previously selected
  * to run. Erases the image if it was selected but its execution failed,
@@ -2724,17 +2725,17 @@ boot_load_and_validate_images(struct boot_loader_state *state)
                 state->slot_usage[BOOT_CURR_IMG(state)].active_slot = NO_ACTIVE_SLOT;
                 continue;
             }
+#endif /* MCUBOOT_DIRECT_XIP */
 
-#ifdef MCUBOOT_DIRECT_XIP_REVERT
+#if defined(MCUBOOT_DIRECT_XIP_REVERT) || defined(MCUBOOT_RAM_LOAD_REVERT)
             rc = boot_select_or_erase(state);
             if (rc != 0) {
                 /* The selected image slot has been erased. */
                 state->slot_usage[BOOT_CURR_IMG(state)].slot_available[active_slot] = false;
                 state->slot_usage[BOOT_CURR_IMG(state)].active_slot = NO_ACTIVE_SLOT;
                 continue;
             }
-#endif /* MCUBOOT_DIRECT_XIP_REVERT */
-#endif /* MCUBOOT_DIRECT_XIP */
+#endif /* MCUBOOT_DIRECT_XIP_REVERT || MCUBOOT_RAM_LOAD_REVERT */
 
 #ifdef MCUBOOT_RAM_LOAD
             /* Image is first loaded to RAM and authenticated there in order to

boot/zephyr/Kconfig

@@ -504,6 +504,17 @@ config BOOT_DIRECT_XIP_REVERT
 	  attempt to boot the previous image. The images can also be made permanent
 	  (marked as confirmed in advance) just like in swap mode.
 
+config BOOT_RAM_LOAD_REVERT
+	bool "Enable the revert mechanism in ram-load mode"
+	depends on BOOT_RAM_LOAD
+	help
+	  If y, enables the revert mechanism in ram-load similar to the one in
+	  swap mode. It requires the trailer magic to be added to the signed image.
+	  When a reboot happens without the image being confirmed at runtime, the
+	  bootloader considers the image faulty and erases it. After this it will
+	  attempt to boot the previous image. The images can also be made permanent
+	  (marked as confirmed in advance) just like in swap mode.
+
 config BOOT_BOOTSTRAP
 	bool "Bootstrap erased the primary slot from the secondary slot"
 	help

boot/zephyr/include/mcuboot_config/mcuboot_config.h

@@ -100,6 +100,10 @@
 #define MCUBOOT_DIRECT_XIP_REVERT
 #endif
 
+#ifdef CONFIG_BOOT_RAM_LOAD_REVERT
+#define MCUBOOT_RAM_LOAD_REVERT
+#endif
+
 #ifdef CONFIG_BOOT_RAM_LOAD
 #define MCUBOOT_RAM_LOAD 1
 #define IMAGE_EXECUTABLE_RAM_START CONFIG_BOOT_IMAGE_EXECUTABLE_RAM_START