8350111: [PPC] AsyncGetCallTrace crashes when called while handling SIGTRAP

Reviewed-by: mbaesken
Backport-of: e4d3c97c0f388fc4b1684b78844f2166277ffd91

Author: reinrich

src/hotspot/cpu/ppc/frame_ppc.cpp

@@ -1,6 +1,6 @@
 /*
- * Copyright (c) 2000, 2023, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2023 SAP SE. All rights reserved.
+ * Copyright (c) 2000, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2025 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -191,6 +191,15 @@ bool frame::safe_for_sender(JavaThread *thread) {
     return false;
   }
 
+  if (sender_pc() == nullptr) {
+    // Likely the return pc was not yet stored to stack. We rather discard this
+    // sample also because we would hit an assertion in frame::setup(). We can
+    // find any other random value if the return pc was not yet stored to
+    // stack. We rely on consistency checks to handle this (see
+    // e.g. find_initial_Java_frame())
+    return false;
+  }
+
   return true;
 }