Date:   Mon, 1 Jul 2019 09:10:45 -0700
From:   Stanislav Fomichev <sdf@...ichev.me>
To:     Andrii Nakryiko <andriin@...com>
Cc:     andrii.nakryiko@...il.com, bpf@...r.kernel.org,
        netdev@...r.kernel.org, ast@...com, daniel@...earbox.net,
        kernel-team@...com, songliubraving@...com
Subject: Re: [PATCH v4 bpf-next 0/9] libbpf: add bpf_link and tracing attach
 APIs

On 06/28, Andrii Nakryiko wrote:
> This patchset adds the following APIs to allow attaching BPF programs to
> tracing entities:
> - bpf_program__attach_perf_event for attaching to any opened perf event FD,
>   allowing users full control;
> - bpf_program__attach_kprobe for attaching to kernel probes (both entry and
>   return probes);
> - bpf_program__attach_uprobe for attaching to user probes (both entry/return);
> - bpf_program__attach_tracepoint for attaching to kernel tracepoints;
> - bpf_program__attach_raw_tracepoint for attaching to raw kernel tracepoint
>   (wrapper around bpf_raw_tracepoint_open);
> 
> This set of APIs makes libbpf more useful for tracing applications.
> 
> All attach APIs return abstract struct bpf_link that encapsulates logic of
> detaching BPF program. See patch #2 for details. bpf_assoc was considered as
> an alternative name for this opaque "handle", but bpf_link seems to be
> appropriate semantically and is nice and short.
> 
> Pre-patch #1 makes internal libbpf_strerror_r helper function work w/ negative
> error codes, lifting the burder off callers to keep track of error sign.
> Patch #2 adds bpf_link abstraction.
> Patch #3 adds attach_perf_event, which is the base for all other APIs.
> Patch #4 adds kprobe/uprobe APIs.
> Patch #5 adds tracepoint API.
> Patch #6 adds raw_tracepoint API.
> Patch #7 converts one existing test to use attach_perf_event.
> Patch #8 adds new kprobe/uprobe tests.
> Patch #9 converts some selftests currently using tracepoint to new APIs.
> 
> v3->v4:
> - proper errno handling (Stanislav);
> - bpf_fd -> prog_fd (Stanislav);
> - switch to fprintf (Song);
Reviewed-by: Stanislav Fomichev <sdf@...gle.com>

Thanks!

> v2->v3:
> - added bpf_link concept (Daniel);
> - didn't add generic bpf_link__attach_program for reasons described in [0];
> - dropped Stanislav's Reviewed-by from patches #2-#6, in case he doesn't like
>   the change;
> v1->v2:
> - preserve errno before close() call (Stanislav);
> - use libbpf_perf_event_disable_and_close in selftest (Stanislav);
> - remove unnecessary memset (Stanislav);
> 
> [0] https://lore.kernel.org/bpf/CAEf4BzZ7EM5eP2eaZn7T2Yb5QgVRiwAs+epeLR1g01TTx-6m6Q@mail.gmail.com/
> 
> Andrii Nakryiko (9):
>   libbpf: make libbpf_strerror_r agnostic to sign of error
>   libbpf: introduce concept of bpf_link
>   libbpf: add ability to attach/detach BPF program to perf event
>   libbpf: add kprobe/uprobe attach API
>   libbpf: add tracepoint attach API
>   libbpf: add raw tracepoint attach API
>   selftests/bpf: switch test to new attach_perf_event API
>   selftests/bpf: add kprobe/uprobe selftests
>   selftests/bpf: convert existing tracepoint tests to new APIs
> 
>  tools/lib/bpf/libbpf.c                        | 359 ++++++++++++++++++
>  tools/lib/bpf/libbpf.h                        |  21 +
>  tools/lib/bpf/libbpf.map                      |   8 +-
>  tools/lib/bpf/str_error.c                     |   2 +-
>  .../selftests/bpf/prog_tests/attach_probe.c   | 155 ++++++++
>  .../bpf/prog_tests/stacktrace_build_id.c      |  50 +--
>  .../bpf/prog_tests/stacktrace_build_id_nmi.c  |  31 +-
>  .../selftests/bpf/prog_tests/stacktrace_map.c |  43 +--
>  .../bpf/prog_tests/stacktrace_map_raw_tp.c    |  15 +-
>  .../selftests/bpf/progs/test_attach_probe.c   |  55 +++
>  10 files changed, 644 insertions(+), 95 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_probe.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_attach_probe.c
> 
> -- 
> 2.17.1
> 

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