feat(fwu): add some sanity checks for the FWU metadata

Add some sanity checks on the values read from the FWU metadata
structure. This ensures that values in the metadata structure are
inline with certain config symbol values.

Change-Id: Ic4415da9048ac3980f8f811ed7852beb90683f7d
Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>

drivers/fwu/fwu.c

@@ -24,6 +24,17 @@
 CASSERT((offsetof(struct fwu_metadata, crc_32) == 0),
 	crc_32_must_be_first_member_of_structure);
 
+/*
+ * Ensure that the NR_OF_FW_BANKS selected by the platform is not
+ * zero and not greater than the maximum number of banks allowed
+ * by the specification.
+ */
+CASSERT((NR_OF_FW_BANKS > 0) && (NR_OF_FW_BANKS <= NR_OF_MAX_FW_BANKS),
+	assert_fwu_num_banks_invalid_value);
+
+#define FWU_METADATA_VERSION		2U
+#define FWU_FW_STORE_DESC_OFFSET	0x20U
+
 static struct fwu_metadata metadata;
 static bool is_metadata_initialized __unused;
 
@@ -51,15 +62,53 @@ static int fwu_metadata_crc_check(void)
 /*******************************************************************************
  * Check the sanity of FWU metadata.
  *
- * return -1 on error, otherwise 0
+ * return -EINVAL on error, otherwise 0
  ******************************************************************************/
 static int fwu_metadata_sanity_check(void)
 {
-	/* ToDo: add more conditions for sanity check */
-	if ((metadata.active_index >= NR_OF_FW_BANKS) ||
-	    (metadata.previous_active_index >= NR_OF_FW_BANKS)) {
-		return -1;
+	if (metadata.version != FWU_METADATA_VERSION) {
+		WARN("Incorrect FWU Metadata version of %u\n",
+		     metadata.version);
+		return -EINVAL;
+	}
+
+	if (metadata.active_index >= NR_OF_FW_BANKS) {
+		WARN("Active Index value(%u) greater than the configured value(%d)",
+		     metadata.active_index, NR_OF_FW_BANKS);
+		return -EINVAL;
+	}
+
+	if (metadata.previous_active_index >= NR_OF_FW_BANKS) {
+		WARN("Previous Active Index value(%u) greater than the configured value(%d)",
+		     metadata.previous_active_index, NR_OF_FW_BANKS);
+		return -EINVAL;
+	}
+
+#if PSA_FWU_METADATA_FW_STORE_DESC
+	if (metadata.fw_desc.num_banks != NR_OF_FW_BANKS) {
+		WARN("Number of Banks(%u) in FWU Metadata different from the configured value(%d)",
+		     metadata.fw_desc.num_banks, NR_OF_FW_BANKS);
+		return -EINVAL;
+	}
+
+	if (metadata.fw_desc.num_images != NR_OF_IMAGES_IN_FW_BANK) {
+		WARN("Number of Images(%u) in FWU Metadata different from the configured value(%d)",
+		     metadata.fw_desc.num_images, NR_OF_IMAGES_IN_FW_BANK);
+		return -EINVAL;
+	}
+
+	if (metadata.desc_offset != FWU_FW_STORE_DESC_OFFSET) {
+		WARN("Descriptor Offset(0x%x) in the FWU Metadata not equal to 0x20\n",
+		     metadata.desc_offset);
+		return -EINVAL;
+	}
+#else
+	if (metadata.desc_offset != 0U) {
+		WARN("Descriptor offset has non zero value of 0x%x\n",
+		     metadata.desc_offset);
+		return -EINVAL;
 	}
+#endif
 
 	return 0;
 }