diff --git a/drivers/acpi/acpica/tbutils.c b/drivers/acpi/acpica/tbutils.c
index 3d6bb83aa7e7..ee6067062cdc 100644
--- a/drivers/acpi/acpica/tbutils.c
+++ b/drivers/acpi/acpica/tbutils.c
@@ -49,69 +49,11 @@
 ACPI_MODULE_NAME("tbutils")
 
 /* Local prototypes */
+static acpi_status acpi_tb_validate_xsdt(acpi_physical_address address);
+
 static acpi_physical_address
 acpi_tb_get_root_table_entry(u8 *table_entry, u32 table_entry_size);
 
-/*******************************************************************************
- *
- * FUNCTION:    acpi_tb_check_xsdt
- *
- * PARAMETERS:  address                    - Pointer to the XSDT
- *
- * RETURN:      status
- *		AE_OK - XSDT is okay
- *		AE_NO_MEMORY - can't map XSDT
- *		AE_INVALID_TABLE_LENGTH - invalid table length
- *		AE_NULL_ENTRY - XSDT has NULL entry
- *
- * DESCRIPTION: validate XSDT
-******************************************************************************/
-
-static acpi_status
-acpi_tb_check_xsdt(acpi_physical_address address)
-{
-	struct acpi_table_header *table;
-	u32 length;
-	u64 xsdt_entry_address;
-	u8 *table_entry;
-	u32 table_count;
-	int i;
-
-	table = acpi_os_map_memory(address, sizeof(struct acpi_table_header));
-	if (!table)
-		return AE_NO_MEMORY;
-
-	length = table->length;
-	acpi_os_unmap_memory(table, sizeof(struct acpi_table_header));
-	if (length < sizeof(struct acpi_table_header))
-		return AE_INVALID_TABLE_LENGTH;
-
-	table = acpi_os_map_memory(address, length);
-	if (!table)
-		return AE_NO_MEMORY;
-
-	/* Calculate the number of tables described in XSDT */
-	table_count =
-		(u32) ((table->length -
-		sizeof(struct acpi_table_header)) / sizeof(u64));
-	table_entry =
-		ACPI_CAST_PTR(u8, table) + sizeof(struct acpi_table_header);
-	for (i = 0; i < table_count; i++) {
-		ACPI_MOVE_64_TO_64(&xsdt_entry_address, table_entry);
-		if (!xsdt_entry_address) {
-			/* XSDT has NULL entry */
-			break;
-		}
-		table_entry += sizeof(u64);
-	}
-	acpi_os_unmap_memory(table, length);
-
-	if (i < table_count)
-		return AE_NULL_ENTRY;
-	else
-		return AE_OK;
-}
-
 #if (!ACPI_REDUCED_HARDWARE)
 /*******************************************************************************
  *
@@ -383,7 +325,7 @@ acpi_tb_get_root_table_entry(u8 *table_entry, u32 table_entry_size)
 	 * Get the table physical address (32-bit for RSDT, 64-bit for XSDT):
 	 * Note: Addresses are 32-bit aligned (not 64) in both RSDT and XSDT
 	 */
-	if (table_entry_size == sizeof(u32)) {
+	if (table_entry_size == ACPI_RSDT_ENTRY_SIZE) {
 		/*
 		 * 32-bit platform, RSDT: Return 32-bit table entry
 		 * 64-bit platform, RSDT: Expand 32-bit to 64-bit and return
@@ -413,6 +355,87 @@ acpi_tb_get_root_table_entry(u8 *table_entry, u32 table_entry_size)
 	}
 }
 
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_tb_validate_xsdt
+ *
+ * PARAMETERS:  address             - Physical address of the XSDT (from RSDP)
+ *
+ * RETURN:      Status. AE_OK if the table appears to be valid.
+ *
+ * DESCRIPTION: Validate an XSDT to ensure that it is of minimum size and does
+ *              not contain any NULL entries. A problem that is seen in the
+ *              field is that the XSDT exists, but is actually useless because
+ *              of one or more (or all) NULL entries.
+ *
+ ******************************************************************************/
+
+static acpi_status acpi_tb_validate_xsdt(acpi_physical_address xsdt_address)
+{
+	struct acpi_table_header *table;
+	u8 *next_entry;
+	acpi_physical_address address;
+	u32 length;
+	u32 entry_count;
+	acpi_status status;
+	u32 i;
+
+	/* Get the XSDT length */
+
+	table =
+	    acpi_os_map_memory(xsdt_address, sizeof(struct acpi_table_header));
+	if (!table) {
+		return (AE_NO_MEMORY);
+	}
+
+	length = table->length;
+	acpi_os_unmap_memory(table, sizeof(struct acpi_table_header));
+
+	/*
+	 * Minimum XSDT length is the size of the standard ACPI header
+	 * plus one physical address entry
+	 */
+	if (length < (sizeof(struct acpi_table_header) + ACPI_XSDT_ENTRY_SIZE)) {
+		return (AE_INVALID_TABLE_LENGTH);
+	}
+
+	/* Map the entire XSDT */
+
+	table = acpi_os_map_memory(xsdt_address, length);
+	if (!table) {
+		return (AE_NO_MEMORY);
+	}
+
+	/* Get the number of entries and pointer to first entry */
+
+	status = AE_OK;
+	next_entry = ACPI_ADD_PTR(u8, table, sizeof(struct acpi_table_header));
+	entry_count = (u32)((table->length - sizeof(struct acpi_table_header)) /
+			    ACPI_XSDT_ENTRY_SIZE);
+
+	/* Validate each entry (physical address) within the XSDT */
+
+	for (i = 0; i < entry_count; i++) {
+		address =
+		    acpi_tb_get_root_table_entry(next_entry,
+						 ACPI_XSDT_ENTRY_SIZE);
+		if (!address) {
+
+			/* Detected a NULL entry, XSDT is invalid */
+
+			status = AE_NULL_ENTRY;
+			break;
+		}
+
+		next_entry += ACPI_XSDT_ENTRY_SIZE;
+	}
+
+	/* Unmap table */
+
+	acpi_os_unmap_memory(table, length);
+	return (status);
+}
+
 /*******************************************************************************
  *
  * FUNCTION:    acpi_tb_parse_root_table
@@ -438,16 +461,14 @@ acpi_status __init acpi_tb_parse_root_table(acpi_physical_address rsdp_address)
 	u32 table_count;
 	struct acpi_table_header *table;
 	acpi_physical_address address;
-	acpi_physical_address uninitialized_var(rsdt_address);
 	u32 length;
 	u8 *table_entry;
 	acpi_status status;
 
 	ACPI_FUNCTION_TRACE(tb_parse_root_table);
 
-	/*
-	 * Map the entire RSDP and extract the address of the RSDT or XSDT
-	 */
+	/* Map the entire RSDP and extract the address of the RSDT or XSDT */
+
 	rsdp = acpi_os_map_memory(rsdp_address, sizeof(struct acpi_table_rsdp));
 	if (!rsdp) {
 		return_ACPI_STATUS(AE_NO_MEMORY);
@@ -459,22 +480,20 @@ acpi_status __init acpi_tb_parse_root_table(acpi_physical_address rsdp_address)
 
 	/* Differentiate between RSDT and XSDT root tables */
 
-	if (rsdp->revision > 1 && rsdp->xsdt_physical_address
+	if ((rsdp->revision > 1) && rsdp->xsdt_physical_address
 			&& !acpi_rsdt_forced) {
 		/*
-		 * Root table is an XSDT (64-bit physical addresses). We must use the
-		 * XSDT if the revision is > 1 and the XSDT pointer is present, as per
-		 * the ACPI specification.
+		 * RSDP contains an XSDT (64-bit physical addresses). We must use
+		 * the XSDT if the revision is > 1 and the XSDT pointer is present,
+		 * as per the ACPI specification.
 		 */
 		address = (acpi_physical_address) rsdp->xsdt_physical_address;
-		table_entry_size = sizeof(u64);
-		rsdt_address = (acpi_physical_address)
-					rsdp->rsdt_physical_address;
+		table_entry_size = ACPI_XSDT_ENTRY_SIZE;
 	} else {
 		/* Root table is an RSDT (32-bit physical addresses) */
 
 		address = (acpi_physical_address) rsdp->rsdt_physical_address;
-		table_entry_size = sizeof(u32);
+		table_entry_size = ACPI_RSDT_ENTRY_SIZE;
 	}
 
 	/*
@@ -483,15 +502,25 @@ acpi_status __init acpi_tb_parse_root_table(acpi_physical_address rsdp_address)
 	 */
 	acpi_os_unmap_memory(rsdp, sizeof(struct acpi_table_rsdp));
 
-	if (table_entry_size == sizeof(u64)) {
-		if (acpi_tb_check_xsdt(address) == AE_NULL_ENTRY) {
-			/* XSDT has NULL entry, RSDT is used */
-			address = rsdt_address;
-			table_entry_size = sizeof(u32);
-			ACPI_WARNING((AE_INFO, "BIOS XSDT has NULL entry, "
-					"using RSDT"));
+	/*
+	 * If it is present, validate the XSDT for access/size and ensure
+	 * that all table entries are at least non-NULL
+	 */
+	if (table_entry_size == ACPI_XSDT_ENTRY_SIZE) {
+		status = acpi_tb_validate_xsdt(address);
+		if (ACPI_FAILURE(status)) {
+			ACPI_BIOS_WARNING((AE_INFO,
+					   "XSDT is invalid (%s), using RSDT",
+					   acpi_format_exception(status)));
+
+			/* Fall back to the RSDT */
+
+			address =
+			    (acpi_physical_address) rsdp->rsdt_physical_address;
+			table_entry_size = ACPI_RSDT_ENTRY_SIZE;
 		}
 	}
+
 	/* Map the RSDT/XSDT table header to get the full table length */
 
 	table = acpi_os_map_memory(address, sizeof(struct acpi_table_header));
@@ -501,12 +530,14 @@ acpi_status __init acpi_tb_parse_root_table(acpi_physical_address rsdp_address)
 
 	acpi_tb_print_table_header(address, table);
 
-	/* Get the length of the full table, verify length and map entire table */
-
+	/*
+	 * Validate length of the table, and map entire table.
+	 * Minimum length table must contain at least one entry.
+	 */
 	length = table->length;
 	acpi_os_unmap_memory(table, sizeof(struct acpi_table_header));
 
-	if (length < sizeof(struct acpi_table_header)) {
+	if (length < (sizeof(struct acpi_table_header) + table_entry_size)) {
 		ACPI_BIOS_ERROR((AE_INFO,
 				 "Invalid table length 0x%X in RSDT/XSDT",
 				 length));
@@ -526,22 +557,21 @@ acpi_status __init acpi_tb_parse_root_table(acpi_physical_address rsdp_address)
 		return_ACPI_STATUS(status);
 	}
 
-	/* Calculate the number of tables described in the root table */
+	/* Get the number of entries and pointer to first entry */
 
 	table_count = (u32)((table->length - sizeof(struct acpi_table_header)) /
 			    table_entry_size);
+	table_entry = ACPI_ADD_PTR(u8, table, sizeof(struct acpi_table_header));
+
 	/*
 	 * First two entries in the table array are reserved for the DSDT
 	 * and FACS, which are not actually present in the RSDT/XSDT - they
 	 * come from the FADT
 	 */
-	table_entry =
-	    ACPI_CAST_PTR(u8, table) + sizeof(struct acpi_table_header);
 	acpi_gbl_root_table_list.current_table_count = 2;
 
-	/*
-	 * Initialize the root table array from the RSDT/XSDT
-	 */
+	/* Initialize the root table array from the RSDT/XSDT */
+
 	for (i = 0; i < table_count; i++) {
 		if (acpi_gbl_root_table_list.current_table_count >=
 		    acpi_gbl_root_table_list.max_table_count) {
@@ -584,7 +614,7 @@ acpi_status __init acpi_tb_parse_root_table(acpi_physical_address rsdp_address)
 		acpi_tb_install_table(acpi_gbl_root_table_list.tables[i].
 				      address, NULL, i);
 
-		/* Special case for FADT - get the DSDT and FACS */
+		/* Special case for FADT - validate it then get the DSDT and FACS */
 
 		if (ACPI_COMPARE_NAME
 		    (&acpi_gbl_root_table_list.tables[i].signature,
diff --git a/include/acpi/actbl.h b/include/acpi/actbl.h
index 94970880126f..325aeae1fa99 100644
--- a/include/acpi/actbl.h
+++ b/include/acpi/actbl.h
@@ -182,6 +182,9 @@ struct acpi_table_xsdt {
 	u64 table_offset_entry[1];	/* Array of pointers to ACPI tables */
 };
 
+#define ACPI_RSDT_ENTRY_SIZE        (sizeof (u32))
+#define ACPI_XSDT_ENTRY_SIZE        (sizeof (u64))
+
 /*******************************************************************************
  *
  * FACS - Firmware ACPI Control Structure (FACS)