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authorMartin KaFai Lau <kafai@fb.com>2020-01-08 16:35:14 -0800
committerAlexei Starovoitov <ast@kernel.org>2020-01-09 08:46:18 -0800
commit590a0088825016ca7ec53f1aef7e84e1211778d8 (patch)
tree52b5cbb3c88cd6600754c545453e2e00b38e7091 /tools/lib/bpf/libbpf.map
parentbpf: Synch uapi bpf.h to tools/ (diff)
downloadlinux-dev-590a0088825016ca7ec53f1aef7e84e1211778d8.tar.xz
linux-dev-590a0088825016ca7ec53f1aef7e84e1211778d8.zip
bpf: libbpf: Add STRUCT_OPS support
This patch adds BPF STRUCT_OPS support to libbpf. The only sec_name convention is SEC(".struct_ops") to identify the struct_ops implemented in BPF, e.g. To implement a tcp_congestion_ops: SEC(".struct_ops") struct tcp_congestion_ops dctcp = { .init = (void *)dctcp_init, /* <-- a bpf_prog */ /* ... some more func prts ... */ .name = "bpf_dctcp", }; Each struct_ops is defined as a global variable under SEC(".struct_ops") as above. libbpf creates a map for each variable and the variable name is the map's name. Multiple struct_ops is supported under SEC(".struct_ops"). In the bpf_object__open phase, libbpf will look for the SEC(".struct_ops") section and find out what is the btf-type the struct_ops is implementing. Note that the btf-type here is referring to a type in the bpf_prog.o's btf. A "struct bpf_map" is added by bpf_object__add_map() as other maps do. It will then collect (through SHT_REL) where are the bpf progs that the func ptrs are referring to. No btf_vmlinux is needed in the open phase. In the bpf_object__load phase, the map-fields, which depend on the btf_vmlinux, are initialized (in bpf_map__init_kern_struct_ops()). It will also set the prog->type, prog->attach_btf_id, and prog->expected_attach_type. Thus, the prog's properties do not rely on its section name. [ Currently, the bpf_prog's btf-type ==> btf_vmlinux's btf-type matching process is as simple as: member-name match + btf-kind match + size match. If these matching conditions fail, libbpf will reject. The current targeting support is "struct tcp_congestion_ops" which most of its members are function pointers. The member ordering of the bpf_prog's btf-type can be different from the btf_vmlinux's btf-type. ] Then, all obj->maps are created as usual (in bpf_object__create_maps()). Once the maps are created and prog's properties are all set, the libbpf will proceed to load all the progs. bpf_map__attach_struct_ops() is added to register a struct_ops map to a kernel subsystem. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200109003514.3856730-1-kafai@fb.com
Diffstat (limited to '')
-rw-r--r--tools/lib/bpf/libbpf.map3
1 files changed, 3 insertions, 0 deletions
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index b300d74c921a..a19f04e6e3d9 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -213,6 +213,7 @@ LIBBPF_0.0.7 {
global:
btf_dump__emit_type_decl;
bpf_link__disconnect;
+ bpf_map__attach_struct_ops;
bpf_object__find_program_by_name;
bpf_object__attach_skeleton;
bpf_object__destroy_skeleton;
@@ -223,5 +224,7 @@ LIBBPF_0.0.7 {
bpf_prog_attach_xattr;
bpf_program__attach;
bpf_program__name;
+ bpf_program__is_struct_ops;
+ bpf_program__set_struct_ops;
btf__align_of;
} LIBBPF_0.0.6;