Updating btf.rst doc with info about BTF_SET_START/END macros.
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
Documentation/bpf/btf.rst | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst
index b5361b8621c9..44dc789de2b4 100644
--- a/Documentation/bpf/btf.rst
+++ b/Documentation/bpf/btf.rst
@@ -724,6 +724,31 @@ want to define unused entry in BTF_ID_LIST, like::
BTF_ID_UNUSED
BTF_ID(struct, task_struct)
+The ``BTF_SET_START/END`` macros pair defines sorted list of BTF ID values
+and their count, with following syntax::
+
+ BTF_SET_START(set)
+ BTF_ID(type1, name1)
+ BTF_ID(type2, name2)
+ BTF_SET_END(set)
+
+resulting in following layout in .BTF_ids section::
+
+ __BTF_ID__set__set:
+ .zero 4
+ __BTF_ID__type1__name1__3:
+ .zero 4
+ __BTF_ID__type2__name2__4:
+ .zero 4
+
+The ``struct btf_id_set set;`` variable is defined to access the list.
+
+The ``typeX`` name can be one of following::
+
+ struct, union, typedef, func
+
+and is used as a filter when resolving the BTF ID value.
+
All the BTF ID lists and sets are compiled in the .BTF_ids section and
resolved during the linking phase of kernel build by ``resolve_btfids`` tool.
--
2.25.4
