Guarantee STFLE facility list alignment under precheck

tests/testDriver_stfle_alignment_precheck.c

@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: Apache-2.0
+/*
+ * Copyright IBM Corp. 2024
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "testsupport.h"
+
+#include <string.h>
+
+/*
+ * Regression coverage for an alignment edge case in the Linux STFLE path.
+ *
+ * When ZDNN_ENABLE_PRECHECK is enabled, invoke_stfle() verifies the facility
+ * list buffer is 8-byte aligned. Historically, zdnn_is_nnpa_installed() used a
+ * local unsigned-char array which is not *guaranteed* to be 8-byte aligned.
+ *
+ * This test asserts that enabling precheck does not trigger a
+ * ZDNN_MISALIGNED_PARMBLOCK failure in the STFLE path.
+ *
+ * Note: This is a Linux-only behavior; z/OS uses a system copy of STFLE.
+ */
+
+void setUp(void) {
+#ifdef __MVS__
+  TEST_IGNORE_MESSAGE("Linux STFLE alignment regression test; skipping on z/OS");
+#endif
+}
+
+void tearDown(void) {}
+
+void test_precheck_does_not_trigger_misaligned_parmblock(void) {
+  precheck_enabled = true;
+
+  char buf_stderr[BUFSIZ] = {0};
+
+  stderr_to_pipe();
+  (void)zdnn_is_nnpa_installed();
+  restore_stderr(buf_stderr, BUFSIZ);
+
+  TEST_ASSERT_NULL_MESSAGE(
+      strstr(buf_stderr, "ZDNN_MISALIGNED_PARMBLOCK"),
+      "Unexpected misaligned parmblock failure in STFLE path");
+
+  precheck_enabled = false;
+}
+
+int main(void) {
+  UNITY_BEGIN();
+
+  RUN_TEST(test_precheck_does_not_trigger_misaligned_parmblock);
+
+  return UNITY_END();
+}

zdnn/initializer.cpp

@@ -18,7 +18,6 @@
 extern "C" {
 #include "zdnn.h"
 }
-#include <iostream>
 
 /// Invoke initializer routine(s) at DLL-load time.
 ///

zdnn/zdnn_init.c

@@ -163,16 +163,19 @@ static inline int check_bitfield(const uint8_t *bitfield, int bitno) {
 bool zdnn_is_nnpa_installed() {
 #ifndef __MVS__
   int nnpa_supported;
-  unsigned char facilities[STFLE_LENGTH] = {0};
+  // invoke_stfle() requires the facility list to be 8-byte aligned when
+  // ZDNN_ENABLE_PRECHECK is enabled. Using a uint64_t array guarantees the
+  // required alignment regardless of compiler/stack placement decisions.
+  uint64_t facilities64[STFLE_LENGTH / 8] = {0};
   int cc;
-  cc = invoke_stfle(facilities);
+  cc = invoke_stfle((unsigned char *)facilities64);
 
   if (cc) {
     LOG_ERROR("STFLE failed with %d", cc);
     return false;
   }
 
-  nnpa_supported = check_bitfield(facilities, STFLE_NNPA);
+  nnpa_supported = check_bitfield((uint8_t *)facilities64, STFLE_NNPA);
 
   LOG_INFO("Hardware NNPA support available - %s",
            nnpa_supported ? "TRUE" : "FALSE");