[DTrace-devel] [PATCH 6/7] cg: allow input to translator to be NULL

[Kris Van Hees]

Some translators support NULL as input pointer value.  The code generator
was performing a NULL-check on a the LHS of a PTR or DOT node before
considering the possibility that the nodemis subject to translator
handling.  The check should happen after translator handling.

With this patch, tst.ProcModelTrans.d works but only for the case of
NULL input.  The test is changed to actually use a real trask_struct as
input.  New test tst.NullInput.d exercises the case this patch fixes.

Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
 libdtrace/dt_cg.c                             |  4 +--
 test/unittest/translators/tst.NullInput.d     | 31 +++++++++++++++++++
 .../unittest/translators/tst.ProcModelTrans.d | 16 ++++------
 3 files changed, 39 insertions(+), 12 deletions(-)
 create mode 100644 test/unittest/translators/tst.NullInput.d

diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
index e05a1f64..ebe2e043 100644
--- a/libdtrace/dt_cg.c
+++ b/libdtrace/dt_cg.c
@@ -6305,8 +6305,6 @@ dt_cg_node(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
 		assert(dnp->dn_right->dn_kind == DT_NODE_IDENT);
 		dt_cg_node(dnp->dn_left, dlp, drp);
 
-		dt_cg_check_notnull(dlp, drp, dnp->dn_left->dn_reg);
-
 		/*
 		 * If the left-hand side of PTR or DOT is a dynamic variable,
 		 * we expect it to be the output of a D translator.   In this
@@ -6340,6 +6338,8 @@ dt_cg_node(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
 			break;
 		}
 
+		dt_cg_check_notnull(dlp, drp, dnp->dn_left->dn_reg);
+
 		ctfp = dnp->dn_left->dn_ctfp;
 		type = ctf_type_resolve(ctfp, dnp->dn_left->dn_type);
 
diff --git a/test/unittest/translators/tst.NullInput.d b/test/unittest/translators/tst.NullInput.d
new file mode 100644
index 00000000..6d5f085b
--- /dev/null
+++ b/test/unittest/translators/tst.NullInput.d
@@ -0,0 +1,31 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2023, 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.
+ */
+
+/*
+ * ASSERTION: Translators can receive NULL as input.
+ *
+ * SECTION: Translators/Translator Declarations
+ * SECTION: Translators/Translate Operator
+ *
+ */
+
+#pragma D option quiet
+
+struct task_struct *T;
+
+BEGIN
+{
+	T = 0;
+	mypr_addr = xlate < psinfo_t > (T).pr_addr;
+	printf("pr_addr: %p", mypr_addr);
+	exit(0);
+}
+
+ERROR
+{
+	exit(1);
+}
diff --git a/test/unittest/translators/tst.ProcModelTrans.d b/test/unittest/translators/tst.ProcModelTrans.d
index cf445658..7d5fff78 100644
--- a/test/unittest/translators/tst.ProcModelTrans.d
+++ b/test/unittest/translators/tst.ProcModelTrans.d
@@ -1,29 +1,25 @@
 /*
  * Oracle Linux DTrace.
- * Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2023, 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.
  */
-/* @@xfail: dtv2 */
 
 /*
- * ASSERTION:
- * Use the translators in /usr/lib/dtrace/procfs.d
+ * ASSERTION: Basic test for translators in /usr/lib/dtrace/procfs.d
  *
- * SECTION: Translators/ Translator Declarations
- * SECTION: Translators/ Translate Operator
+ * SECTION: Translators/Translator Declarations
+ * SECTION: Translators/Translate Operator
  * SECTION: Translators/Process Model Translators
  *
  */
 
 #pragma D option quiet
 
-struct task_struct *T;
-
 BEGIN
 {
-	mypr_addr = xlate < psinfo_t > (T).pr_addr;
-	printf("pr_addr: %d", mypr_addr);
+	mypr_addr = xlate < psinfo_t > (curthread).pr_addr;
+	printf("pr_addr: %p", mypr_addr);
 	exit(0);
 }
 
-- 
2.39.3