netdev - [PATCH bpf-next v5 0/3] libbpf: Add support for dynamic program attach target

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Message-Id: <158220517358.127661.1514720920408191215.stgit@xdp-tutorial>
Date:   Thu, 20 Feb 2020 13:26:13 +0000
From:   Eelco Chaudron <echaudro@...hat.com>
To:     bpf@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net, kafai@...com, songliubraving@...com,
        yhs@...com, andriin@...com, toke@...hat.com
Subject: [PATCH bpf-next v5 0/3] libbpf: Add support for dynamic program attach target

Currently when you want to attach a trace program to a bpf program
the section name needs to match the tracepoint/function semantics.

However the addition of the bpf_program__set_attach_target() API
allows you to specify the tracepoint/function dynamically.

The call flow would look something like this:

  xdp_fd = bpf_prog_get_fd_by_id(id);
  trace_obj = bpf_object__open_file("func.o", NULL);
  prog = bpf_object__find_program_by_title(trace_obj,
                                           "fentry/myfunc");
  bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
  bpf_program__set_attach_target(prog, xdp_fd,
                                 "xdpfilt_blk_all");
  bpf_object__load(trace_obj)

Signed-off-by: Eelco Chaudron <echaudro@...hat.com>
Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>

v1 -> v2: Remove requirement for attach type hint in API
v2 -> v3: Moved common warning to __find_vmlinux_btf_id, requested by Andrii
          Updated the xdp_bpf2bpf test to use this new API
v3 -> v4: Split up patch, update libbpf.map version
v4 -> v5: Fix return code, and prog assignment in test case