+ if (rsdp->revision > 1 && rsdp->xsdt_physical_address) {
+ /*
+ * 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.
+ */
+ address = (acpi_physical_address) rsdp->xsdt_physical_address;
+ table_entry_size = sizeof(u64);
+ rsdt_address = (acpi_physical_address)
+ rsdp->rsdt_physical_address;
+ } else {
+ /* Root table is an RSDT (32-bit physical addresses) */
+
+ address = (acpi_physical_address) rsdp->rsdt_physical_address;
+ table_entry_size = sizeof(u32);
+ }
+
+ /*
+ * It is not possible to map more than one entry in some environments,
+ * so unmap the RSDP here before mapping other tables
+ */
+ 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"));
+ }
+ }
+ /* Map the RSDT/XSDT table header to get the full table length */
+
+ table = acpi_os_map_memory(address, sizeof(struct acpi_table_header));
+ if (!table) {
+ return_ACPI_STATUS(AE_NO_MEMORY);
+ }
+
+ acpi_tb_print_table_header(address, table);
+
+ /* Get the length of the full table, verify length and map entire table */
+
+ length = table->length;
+ acpi_os_unmap_memory(table, sizeof(struct acpi_table_header));
+
+ if (length < sizeof(struct acpi_table_header)) {
+ ACPI_ERROR((AE_INFO, "Invalid length 0x%X in RSDT/XSDT",
+ length));
+ return_ACPI_STATUS(AE_INVALID_TABLE_LENGTH);
+ }