DISABLE_BACKUP is now powerfail-safe.

By not checking/updating sector flags during copies from UPDATE to
BOOT partitions, a copy operation getting interrupted by power failure
will be less likely to cause problems to the integrity of the BOOT
image. This is because in case of interruptions, the copy operation
will be restarted from the first sector.

Author: danielinux

src/update_flash.c

@@ -553,23 +553,14 @@ static int RAMFUNCTION wolfBoot_update(int fallback_allowed)
 #endif
     hal_flash_lock();
 #else /* DISABLE_BACKUP */
-#warning "Backup mechanism disabled! Update installation will not be interruptible"
-    /* Read encryption key/IV before starting the update */
 #ifdef EXT_ENCRYPTED
     wolfBoot_get_encrypt_key(key, nonce);
 #endif
 
     /* Directly copy the content of the UPDATE partition into the BOOT partition.
-     * This mechanism is not fail-safe, and will brick your device if interrupted
-     * before the copy is finished.
      */
     while ((sector * sector_size) < total_size) {
-        if ((wolfBoot_get_update_sector_flag(sector, &flag) != 0) || (flag == SECT_FLAG_NEW)) {
-           flag = SECT_FLAG_SWAPPING;
-           wolfBoot_copy_sector(&update, &boot, sector);
-           if (((sector + 1) * sector_size) < WOLFBOOT_PARTITION_SIZE)
-               wolfBoot_set_update_sector_flag(sector, flag);
-        }
+        wolfBoot_copy_sector(&update, &boot, sector);
         sector++;
     }
     while((sector * sector_size) < WOLFBOOT_PARTITION_SIZE) {
@@ -578,7 +569,6 @@ static int RAMFUNCTION wolfBoot_update(int fallback_allowed)
     }
     st = IMG_STATE_SUCCESS;
     wolfBoot_set_partition_state(PART_BOOT, st);
-
 #ifdef EXT_FLASH
     ext_flash_lock();
 #endif