1 files changed, 71 insertions, 0 deletions

diff --git a/drivers/acpi/tables/tbutils.c b/drivers/acpi/tables/tbutils.c
index 1da64b4518c0..8cc9492ffbf2 100644
--- a/drivers/acpi/tables/tbutils.c
+++ b/drivers/acpi/tables/tbutils.c
@@ -51,6 +51,65 @@ ACPI_MODULE_NAME("tbutils")
 static acpi_physical_address
 acpi_tb_get_root_table_entry(u8 * table_entry,
                              acpi_native_uint 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;
+}
 
 /*******************************************************************************
  *
@@ -341,6 +400,7 @@ acpi_tb_parse_root_table(acpi_physical_address rsdp_address, u8 flags)
         u32 table_count;
         struct acpi_table_header *table;
         acpi_physical_address address;
+        acpi_physical_address rsdt_address;
         u32 length;
         u8 *table_entry;
         acpi_status status;
@@ -369,6 +429,8 @@ acpi_tb_parse_root_table(acpi_physical_address rsdp_address, u8 flags)
                  */
                 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) */
 
@@ -382,6 +444,15 @@ acpi_tb_parse_root_table(acpi_physical_address rsdp_address, u8 flags)
          */
         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));