From 68a26bc7922ebf8bbf418f8e9d69364d965433e9 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Tue, 25 Aug 2020 21:21:21 +0200 Subject: [PATCH] bpf: Update .BTF_ids section in btf.rst with sets info Updating btf.rst doc with info about BTF_SET_START/END macros. Signed-off-by: Jiri Olsa Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20200825192124.710397-12-jolsa@kernel.org --- 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.