doc: Explain `struct lttng_bytecode_runtime` layout restrictions

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I875b11c644917a3b9f15bf88ab44098813e59db0

diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h
index 54eb09550ce4000bd20855c0e40f254960ad19cb..b050d30ec03af5d0b435f27dae85a0c71a5d16b5 100644 (file)
--- a/include/lttng/ust-events.h
+++ b/include/lttng/ust-events.h
@@ -459,6 +459,12 @@ enum lttng_filter_ret {
        /* Other bits are kept for future use. */
 };
 
+/*
+ * This structure is used in the probes. More specifically, the `filter` and
+ * `node` fields are explicity used in the probes. When modifying this
+ * structure we must not change the layout of these two fields as it is
+ * considered ABI.
+ */
 struct lttng_bytecode_runtime {
        /* Associated bytecode */
        struct lttng_ust_filter_bytecode_node *bc;