[DTrace-devel] [PATCH 03/05] agg: report error if aggsize is too small

[Kris Van Hees]

When aggregations are used, ensure that the aggsize value is sufficient
to hold at least a single aggregation.

Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
 libdtrace/dt_bpf.c                         |  3 +--
 test/unittest/aggs/err.aggsize-too-small.d | 26 ++++++++++++++++++++++
 test/unittest/aggs/err.aggsize-too-small.r |  3 +++
 3 files changed, 30 insertions(+), 2 deletions(-)
 create mode 100644 test/unittest/aggs/err.aggsize-too-small.d
 create mode 100644 test/unittest/aggs/err.aggsize-too-small.r

diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
index 18aa07af..b553b33f 100644
--- a/libdtrace/dt_bpf.c
+++ b/libdtrace/dt_bpf.c
@@ -520,9 +520,8 @@ gmap_create_aggs(dtrace_hdl_t *dtp)
 
 	nelems = dtp->dt_options[DTRACEOPT_AGGSIZE] /
 		 (dtp->dt_maxtuplesize + dtp->dt_maxaggdsize);
-
 	if (nelems == 0)
-		return 0;
+		return dt_set_errno(dtp, EDT_BUFTOOSMALL);
 
 	dtp->dt_aggmap_fd = create_gmap_of_maps(dtp, "aggs",
 						BPF_MAP_TYPE_ARRAY_OF_MAPS,
diff --git a/test/unittest/aggs/err.aggsize-too-small.d b/test/unittest/aggs/err.aggsize-too-small.d
new file mode 100644
index 00000000..8bd12381
--- /dev/null
+++ b/test/unittest/aggs/err.aggsize-too-small.d
@@ -0,0 +1,26 @@
+/*
+ * 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: If aggsize is too small to hold a single aggregation, report an
+ *	      error.
+ *
+ * SECTION: Aggregations/Aggregations
+ */
+
+#pragma D option aggsize=8
+
+BEGIN
+{
+	@ = count();
+	exit(0);
+}
+
+ERROR
+{
+	exit(0);
+}
diff --git a/test/unittest/aggs/err.aggsize-too-small.r b/test/unittest/aggs/err.aggsize-too-small.r
new file mode 100644
index 00000000..b0a37c5d
--- /dev/null
+++ b/test/unittest/aggs/err.aggsize-too-small.r
@@ -0,0 +1,3 @@
+-- @@stderr --
+dtrace: script 'test/unittest/aggs/err.aggsize-too-small.d' matched 2 probes
+dtrace: could not enable tracing: Enabling exceeds size of buffer
-- 
2.40.1