samples, bpf: Refactor tail call user progs with libbpf

BPF tail call uses the BPF_MAP_TYPE_PROG_ARRAY type map for calling
into other BPF programs and this PROG_ARRAY should be filled prior to
use. Currently, samples with the PROG_ARRAY type MAP fill this program
array with bpf_load. For bpf_load to fill this map, kernel BPF program
must specify the section with specific format of <prog_type>/<array_idx>
(e.g. SEC("socket/0"))

But by using libbpf instead of bpf_load, user program can specify which
programs should be added to PROG_ARRAY. The advantage of this approach
is that you can selectively add only the programs you want, rather than
adding all of them to PROG_ARRAY, and it's much more intuitive than the
traditional approach.

This commit refactors user programs with the PROG_ARRAY type MAP with
libbpf instead of using bpf_load.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200516040608.1377876-4-danieltimlee@gmail.com

1 files changed, 2 insertions, 2 deletions

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4c91e5914329..8403e4762306 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -63,12 +63,12 @@ TRACE_HELPERS := ../../tools/testing/selftests/bpf/trace_helpers.o
 fds_example-objs := fds_example.o
 sockex1-objs := sockex1_user.o
 sockex2-objs := sockex2_user.o
-sockex3-objs := bpf_load.o sockex3_user.o
+sockex3-objs := sockex3_user.o
 tracex1-objs := tracex1_user.o $(TRACE_HELPERS)
 tracex2-objs := tracex2_user.o
 tracex3-objs := tracex3_user.o
 tracex4-objs := tracex4_user.o
-tracex5-objs := bpf_load.o tracex5_user.o $(TRACE_HELPERS)
+tracex5-objs := tracex5_user.o $(TRACE_HELPERS)
 tracex6-objs := tracex6_user.o
 tracex7-objs := tracex7_user.o
 test_probe_write_user-objs := bpf_load.o test_probe_write_user_user.o