Ensure that 'execname' is not marked DPTR

The 'execname' builtin variable is a notable exception to REF-type
variables being DTrace-managed pointers.  It is a pointer into the
task_struct and therefore needs to be explicitly excluded from the
DPTR marking of variable nodes.

Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Reviewed-by: Eugene Loh <eugene.loh@oracle.com>

libdtrace/dt_parser.c

@@ -2837,9 +2837,13 @@ dt_xcook_ident(dt_node_t *dnp, dt_idhash_t *dhp, uint_t idkind, int create)
 		 * storage (DPTR), or if the type of the variable is a
 		 * REF-type, we mark this variable node as a pointer to
 		 * DTrace-managed storage (DPTR).
+		 *
+		 * We account for one notable exception: execname.
 		 */
-		if ((idp->di_flags & DT_IDFLG_DPTR) ||
-		    (dnp->dn_flags & DT_NF_REF))
+		if (idp->di_flags & DT_IDFLG_DPTR)
+			dnp->dn_flags |= DT_NF_DPTR;
+		else if ((dnp->dn_flags & DT_NF_REF) &&
+			 idp->di_id != DIF_VAR_EXECNAME)
 			dnp->dn_flags |= DT_NF_DPTR;
 
 		if (idp->di_flags & DT_IDFLG_WRITE)

test/unittest/codegen/tst.execname-idx.d

@@ -0,0 +1,19 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ */
+
+#pragma D option quiet
+
+BEGIN
+{
+	trace(execname[0]);
+	exit(0);
+}
+
+ERROR
+{
+	exit(1);
+}