Check diagnostics partition is aligned and doesn't overlap

Also updates docs to specify the requirement of the HAL flash driver by
wolfBoot_clear_failures().

docs/API.md

@@ -116,6 +116,11 @@ The application can read the records, ordered newest-first, through this API:
   copy record `index` (0 is the most recent) into `out`. Returns 0 on success.
 - `int wolfBoot_clear_failures(void)`: erase the diagnostics region.
 
+The read functions only read the region and have no external dependency.
+`wolfBoot_clear_failures()`, however, erases flash, so an application that calls
+it must have the HAL flash driver (`hal_flash_unlock`, `hal_flash_erase`,
+`hal_flash_lock`) similarly to `wolfBoot_success()`.
+
 Each `struct wolfBoot_failure_record` reports `phase`, `cause`, `partition`,
 `fw_version` (the version of the offending image, when known) and a monotonic
 `seq` number.

include/target.h.in

@@ -146,6 +146,49 @@
     #endif
 #endif
 
+#ifdef WOLFBOOT_PERSIST_FAILURE_STATUS
+    #ifndef WOLFBOOT_DIAGNOSTICS_SECTORS
+    #define WOLFBOOT_DIAGNOSTICS_SECTORS 2
+    #endif
+
+    #if (WOLFBOOT_DIAGNOSTICS_ADDRESS % WOLFBOOT_SECTOR_SIZE) != 0
+        #error "Diagnostics region is not sector-aligned"
+    #endif
+
+    #if !defined(WOLFBOOT_PART_USE_ARCH_OFFSET) && \
+        !defined(PULL_LINKER_DEFINES) && !defined(WOLFBOOT_DIAGNOSTICS_EXT)
+        #if !defined(PART_BOOT_EXT) && \
+            ((WOLFBOOT_PARTITION_BOOT_ADDRESS + 0) != 0) && \
+            ((WOLFBOOT_DIAGNOSTICS_ADDRESS + 0 + \
+              WOLFBOOT_DIAGNOSTICS_SECTORS * WOLFBOOT_SECTOR_SIZE) > \
+             (WOLFBOOT_PARTITION_BOOT_ADDRESS + 0)) && \
+            ((WOLFBOOT_DIAGNOSTICS_ADDRESS + 0) < \
+             (WOLFBOOT_PARTITION_BOOT_ADDRESS + 0 + WOLFBOOT_PARTITION_SIZE + 0))
+            #error "Diagnostics region overlaps the boot partition"
+        #endif
+
+        #if !defined(PART_UPDATE_EXT) && \
+            ((WOLFBOOT_PARTITION_UPDATE_ADDRESS + 0) != 0) && \
+            ((WOLFBOOT_DIAGNOSTICS_ADDRESS + 0 + \
+              WOLFBOOT_DIAGNOSTICS_SECTORS * WOLFBOOT_SECTOR_SIZE) > \
+             (WOLFBOOT_PARTITION_UPDATE_ADDRESS + 0)) && \
+            ((WOLFBOOT_DIAGNOSTICS_ADDRESS + 0) < \
+             (WOLFBOOT_PARTITION_UPDATE_ADDRESS + 0 + WOLFBOOT_PARTITION_SIZE + 0))
+            #error "Diagnostics region overlaps the update partition"
+        #endif
+
+        #if !defined(PART_SWAP_EXT) && \
+            ((WOLFBOOT_PARTITION_SWAP_ADDRESS + 0) != 0) && \
+            ((WOLFBOOT_DIAGNOSTICS_ADDRESS + 0 + \
+              WOLFBOOT_DIAGNOSTICS_SECTORS * WOLFBOOT_SECTOR_SIZE) > \
+             (WOLFBOOT_PARTITION_SWAP_ADDRESS + 0)) && \
+            ((WOLFBOOT_DIAGNOSTICS_ADDRESS + 0) < \
+             (WOLFBOOT_PARTITION_SWAP_ADDRESS + 0 + WOLFBOOT_SECTOR_SIZE))
+            #error "Diagnostics region overlaps the swap partition"
+        #endif
+    #endif
+#endif /* WOLFBOOT_PERSIST_FAILURE_STATUS */
+
 #endif /* WOLFBOOT_FIXED_PARTITIONS */
 
 #if !defined(WOLFBOOT_NO_LOAD_ADDRESS)