boot: bootutil: Add write block size checking

Adds write block size checking functionality and includes a
zephyr implementation, this will not throw an error or prevent
upgrade but will emit a debug log with a discrepency message

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

Author: nordicjm

boot/bootutil/src/swap_move.c

@@ -311,6 +311,13 @@ boot_slots_compatible(struct boot_loader_state *state)
     }
 #endif
 
+#if defined(MCUBOOT_SLOT0_EXPECTED_WRITE_SIZE) || defined(MCUBOOT_SLOT1_EXPECTED_WRITE_SIZE)
+    if (!swap_write_block_size_check(state)) {
+        BOOT_LOG_WRN("Cannot upgrade: slot write sizes are not compatible");
+        return 0;
+    }
+#endif
+
     if (num_sectors_pri > num_sectors_sec) {
         if (sector_sz_pri != boot_img_sector_size(state, BOOT_PRIMARY_SLOT, i)) {
             BOOT_LOG_WRN("Cannot upgrade: not same sector layout");

boot/bootutil/src/swap_priv.h

@@ -101,6 +101,19 @@ static inline size_t boot_scratch_area_size(const struct boot_loader_state *stat
 
 #endif /* defined(MCUBOOT_SWAP_USING_SCRATCH) || defined(MCUBOOT_SWAP_USING_MOVE) */
 
+#if defined(MCUBOOT_SWAP_USING_MOVE)
+/**
+ * Check if device write block sizes are as expected, function should emit an error if there is
+ * a problem. If true is returned, the slots are marked as compatible, otherwise the slots are
+ * marked as incompatible.
+ *
+ * Requires MCUBOOT_SLOT0_EXPECTED_WRITE_SIZE be set to the write block size of image 0 primary
+ * slot and MCUBOOT_SLOT1_EXPECTED_WRITE_SIZE be set to the write block size of image 0 secondary
+ * slot.
+ */
+bool swap_write_block_size_check(struct boot_loader_state *state);
+#endif /* defined(MCUBOOT_SWAP_USING_MOVE) */
+
 /**
  * Returns the maximum size of an application that can be loaded to a slot.
  */

boot/zephyr/CMakeLists.txt

@@ -380,9 +380,16 @@ dt_prop(slot0_size PATH "${slot0_flash}" PROPERTY "reg" INDEX 1)
 dt_get_parent(slot0_flash)
 dt_get_parent(slot0_flash)
 dt_prop(erase_size_slot0 PATH "${slot0_flash}" PROPERTY "erase-block-size")
+dt_prop(write_size_slot0 PATH "${slot0_flash}" PROPERTY "write-block-size")
 
-if(CONFIG_BOOT_SWAP_USING_MOVE AND DEFINED erase_size_slot0)
-  zephyr_compile_definitions("MCUBOOT_SLOT0_EXPECTED_ERASE_SIZE=${erase_size_slot0}")
+if(CONFIG_BOOT_SWAP_USING_MOVE)
+  if(DEFINED erase_size_slot0)
+    zephyr_compile_definitions("MCUBOOT_SLOT0_EXPECTED_ERASE_SIZE=${erase_size_slot0}")
+  endif()
+
+  if(DEFINED write_size_slot0)
+    zephyr_compile_definitions("MCUBOOT_SLOT0_EXPECTED_WRITE_SIZE=${write_size_slot0}")
+  endif()
 endif()
 
 if(NOT CONFIG_SINGLE_APPLICATION_SLOT)
@@ -391,9 +398,16 @@ if(NOT CONFIG_SINGLE_APPLICATION_SLOT)
   dt_get_parent(slot1_flash)
   dt_get_parent(slot1_flash)
   dt_prop(erase_size_slot1 PATH "${slot1_flash}" PROPERTY "erase-block-size")
+  dt_prop(write_size_slot1 PATH "${slot1_flash}" PROPERTY "write-block-size")
+
+  if(CONFIG_BOOT_SWAP_USING_MOVE)
+    if(DEFINED erase_size_slot1)
+      zephyr_compile_definitions("MCUBOOT_SLOT1_EXPECTED_ERASE_SIZE=${erase_size_slot1}")
+    endif()
 
-  if(CONFIG_BOOT_SWAP_USING_MOVE AND DEFINED erase_size_slot1)
-    zephyr_compile_definitions("MCUBOOT_SLOT1_EXPECTED_ERASE_SIZE=${erase_size_slot1}")
+    if(DEFINED write_size_slot1)
+      zephyr_compile_definitions("MCUBOOT_SLOT1_EXPECTED_WRITE_SIZE=${write_size_slot1}")
+    endif()
   endif()
 endif()
 
@@ -428,6 +442,10 @@ if(CONFIG_BOOT_MAX_IMG_SECTORS_AUTO)
   endif()
 endif()
 
+if((CONFIG_BOOT_SWAP_USING_SCRATCH OR CONFIG_BOOT_SWAP_USING_MOVE) AND (DEFINED write_size_slot0 OR DEFINED write_size_slot1))
+  zephyr_library_sources(flash_check.c)
+endif()
+
 if(SYSBUILD)
   if(CONFIG_SINGLE_APPLICATION_SLOT OR CONFIG_BOOT_FIRMWARE_LOADER OR 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)
     # TODO: RAM LOAD support

boot/zephyr/flash_check.c

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/devicetree.h>
+#include <zephyr/drivers/flash.h>
+
+#include <../../bootutil/src/bootutil_priv.h>
+#include "bootutil/bootutil_log.h"
+
+#include "mcuboot_config/mcuboot_config.h"
+
+#if defined(MCUBOOT_SLOT0_EXPECTED_WRITE_SIZE) || defined(MCUBOOT_SLOT1_EXPECTED_WRITE_SIZE)
+BOOT_LOG_MODULE_DECLARE(mcuboot);
+
+bool swap_write_block_size_check(struct boot_loader_state *state)
+{
+#ifdef MCUBOOT_SLOT0_EXPECTED_WRITE_SIZE
+    size_t flash_write_block_size_pri;
+#endif
+#ifdef MCUBOOT_SLOT1_EXPECTED_WRITE_SIZE
+    size_t flash_write_block_size_sec;
+#endif
+
+#ifdef MCUBOOT_SLOT0_EXPECTED_WRITE_SIZE
+    flash_write_block_size_pri = flash_get_write_block_size(
+                                              state->imgs[0][BOOT_PRIMARY_SLOT].area->fa_dev);
+
+    if (flash_write_block_size_pri != MCUBOOT_SLOT0_EXPECTED_WRITE_SIZE) {
+        BOOT_LOG_DBG("Discrepancy, slot0 expected write block size: %d, actual: %d",
+                     MCUBOOT_SLOT0_EXPECTED_WRITE_SIZE, flash_write_block_size_pri);
+    }
+#endif
+
+#ifdef MCUBOOT_SLOT1_EXPECTED_WRITE_SIZE
+    flash_write_block_size_sec = flash_get_write_block_size(
+                                              state->imgs[0][BOOT_SECONDARY_SLOT].area->fa_dev);
+
+    if (flash_write_block_size_sec != MCUBOOT_SLOT1_EXPECTED_WRITE_SIZE) {
+        BOOT_LOG_DBG("Discrepancy, slot1 expected write block size: %d, actual: %d",
+                     MCUBOOT_SLOT1_EXPECTED_WRITE_SIZE, flash_write_block_size_sec);
+    }
+#endif
+
+    return true;
+}
+#endif