ACPICA: Improve error message for Index() operator

For the case where an attempt is made to take an Index() beyond
the end of a String, Buffer, or Package, emit the actual length
of the object to the error message. Helpful for debugging.
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/exoparg2.c

@@ -257,7 +257,7 @@ acpi_status acpi_ex_opcode_2A_1T_1R(struct acpi_walk_state *walk_state)
 	union acpi_operand_object *return_desc = NULL;
 	u64 index;
 	acpi_status status = AE_OK;
-	acpi_size length;
+	acpi_size length = 0;
 
 	ACPI_FUNCTION_TRACE_STR(ex_opcode_2A_1T_1R,
 				acpi_ps_get_opcode_name(walk_state->opcode));
@@ -320,7 +320,6 @@ acpi_status acpi_ex_opcode_2A_1T_1R(struct acpi_walk_state *walk_state)
 		 * NOTE: A length of zero is ok, and will create a zero-length, null
 		 *       terminated string.
 		 */
-		length = 0;
 		while ((length < operand[0]->buffer.length) &&
 		       (length < operand[1]->integer.value) &&
 		       (operand[0]->buffer.pointer[length])) {
@@ -376,6 +375,7 @@ acpi_status acpi_ex_opcode_2A_1T_1R(struct acpi_walk_state *walk_state)
 		case ACPI_TYPE_STRING:
 
 			if (index >= operand[0]->string.length) {
+				length = operand[0]->string.length;
 				status = AE_AML_STRING_LIMIT;
 			}
 
@@ -386,6 +386,7 @@ acpi_status acpi_ex_opcode_2A_1T_1R(struct acpi_walk_state *walk_state)
 		case ACPI_TYPE_BUFFER:
 
 			if (index >= operand[0]->buffer.length) {
+				length = operand[0]->buffer.length;
 				status = AE_AML_BUFFER_LIMIT;
 			}
 
@@ -396,6 +397,7 @@ acpi_status acpi_ex_opcode_2A_1T_1R(struct acpi_walk_state *walk_state)
 		case ACPI_TYPE_PACKAGE:
 
 			if (index >= operand[0]->package.count) {
+				length = operand[0]->package.count;
 				status = AE_AML_PACKAGE_LIMIT;
 			}
 
@@ -414,8 +416,8 @@ acpi_status acpi_ex_opcode_2A_1T_1R(struct acpi_walk_state *walk_state)
 
 		if (ACPI_FAILURE(status)) {
 			ACPI_EXCEPTION((AE_INFO, status,
-					"Index (0x%8.8X%8.8X) is beyond end of object",
-					ACPI_FORMAT_UINT64(index)));
+					"Index (0x%X%8.8X) is beyond end of object (length 0x%X)",
+					ACPI_FORMAT_UINT64(index), length));
 			goto cleanup;
 		}