ACPICA: acpidump: Fix truncated RSDP signature validation.

This patch enforces a rule to always use ACPI_VALIDATE_RSDP_SIG for RSDP
signatures passed from table header or ACPI_SIG_RSDP so that truncated
string comparison can be avoided.  This could help to fix the issue that
"RSD " matches but "RSD PTR " doesn't match.  Lv Zheng.
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

tools/power/acpi/os_specific/service_layers/oslinuxtbl.c

@@ -996,11 +996,22 @@ osl_map_table(acpi_size address,
 
 	/* If specified, signature must match */
 
-	if (signature && !ACPI_COMPARE_NAME(signature, mapped_table->signature)) {
+	if (signature) {
+		if (ACPI_VALIDATE_RSDP_SIG(signature)) {
+			if (!ACPI_VALIDATE_RSDP_SIG(mapped_table->signature)) {
+				acpi_os_unmap_memory(mapped_table,
+						     sizeof(struct
+							    acpi_table_header));
+				return (AE_BAD_SIGNATURE);
+			}
+		} else
+		    if (!ACPI_COMPARE_NAME(signature, mapped_table->signature))
+		{
 			acpi_os_unmap_memory(mapped_table,
 					     sizeof(struct acpi_table_header));
 			return (AE_BAD_SIGNATURE);
 		}
+	}
 
 	/* Map the entire table */
 
@@ -1135,13 +1146,23 @@ osl_read_table_from_file(char *filename,
 
 	/* If signature is specified, it must match the table */
 
-	if (signature && !ACPI_COMPARE_NAME(signature, header.signature)) {
+	if (signature) {
+		if (ACPI_VALIDATE_RSDP_SIG(signature)) {
+			if (!ACPI_VALIDATE_RSDP_SIG(header.signature)) {
+				fprintf(stderr,
+					"Incorrect RSDP signature: found %8.8s\n",
+					header.signature);
+				status = AE_BAD_SIGNATURE;
+				goto exit;
+			}
+		} else if (!ACPI_COMPARE_NAME(signature, header.signature)) {
 			fprintf(stderr,
 				"Incorrect signature: Expecting %4.4s, found %4.4s\n",
 				signature, header.signature);
 			status = AE_BAD_SIGNATURE;
 			goto exit;
 		}
+	}
 
 	table_length = ap_get_table_length(&header);
 	if (table_length == 0) {