[PATCH bpf-next v3 0/7] bpf: implement BPF_TASK_FD_QUERY

[Yonghong Song <yhs@fb.com>]

Currently, suppose a userspace application has loaded a bpf program
and attached it to a tracepoint/kprobe/uprobe, and a bpf
introspection tool, e.g., bpftool, wants to show which bpf program
is attached to which tracepoint/kprobe/uprobe. Such attachment
information will be really useful to understand the overall bpf
deployment in the system.

There is a name field (16 bytes) for each program, which could
be used to encode the attachment point. There are some drawbacks
for this approaches. First, bpftool user (e.g., an admin) may not
really understand the association between the name and the
attachment point. Second, if one program is attached to multiple
places, encoding a proper name which can imply all these
attachments becomes difficult.

This patch introduces a new bpf subcommand BPF_TASK_FD_QUERY.
Given a pid and fd, this command will return bpf related information
to user space. Right now it only supports tracepoint/kprobe/uprobe
perf event fd's. For such a fd, BPF_TASK_FD_QUERY will return
   . prog_id
   . tracepoint name, or
   . k[ret]probe funcname + offset or kernel addr, or
   . u[ret]probe filename + offset
to the userspace.
The user can use "bpftool prog" to find more information about
bpf program itself with prog_id.

Patch #1 adds function perf_get_event() in kernel/events/core.c.
Patch #2 implements the bpf subcommand BPF_TASK_FD_QUERY.
Patch #3 syncs tools bpf.h header and also add bpf_task_fd_query()
in the libbpf library for samples/selftests/bpftool to use.
Patch #4 adds ksym_get_addr() utility function.
Patch #5 add a test in samples/bpf for querying k[ret]probes and
u[ret]probes.
Patch #6 add a test in tools/testing/selftests/bpf for querying
raw_tracepoint and tracepoint.
Patch #7 add a new subcommand "perf" to bpftool.

Changelogs:
  v2 -> v3:
     . made perf_get_event() return perf_event pointer const.
       this was to ensure that event fields are not meddled.
     . detect whether newly BPF_TASK_FD_QUERY is supported or
       not in "bpftool perf" and warn users if it is not.
  v1 -> v2:
     . changed bpf subcommand name from BPF_PERF_EVENT_QUERY
       to BPF_TASK_FD_QUERY.
     . fixed various "bpftool perf" issues and added documentation
       and auto-completion.

Yonghong Song (7):
  perf/core: add perf_get_event() to return perf_event given a struct
    file
  bpf: introduce bpf subcommand BPF_TASK_FD_QUERY
  tools/bpf: sync kernel header bpf.h and add bpf_trace_event_query in
    libbpf
  tools/bpf: add ksym_get_addr() in trace_helpers
  samples/bpf: add a samples/bpf test for BPF_TASK_FD_QUERY
  tools/bpf: add two BPF_TASK_FD_QUERY tests in test_progs
  tools/bpftool: add perf subcommand

 include/linux/perf_event.h                       |   5 +
 include/linux/trace_events.h                     |  16 +
 include/uapi/linux/bpf.h                         |  27 ++
 kernel/bpf/syscall.c                             | 124 ++++++++
 kernel/events/core.c                             |   8 +
 kernel/trace/bpf_trace.c                         |  48 +++
 kernel/trace/trace_kprobe.c                      |  29 ++
 kernel/trace/trace_uprobe.c                      |  22 ++
 samples/bpf/Makefile                             |   4 +
 samples/bpf/task_fd_query_kern.c                 |  19 ++
 samples/bpf/task_fd_query_user.c                 | 379 +++++++++++++++++++++++
 tools/bpf/bpftool/Documentation/bpftool-perf.rst |  81 +++++
 tools/bpf/bpftool/Documentation/bpftool.rst      |   5 +-
 tools/bpf/bpftool/bash-completion/bpftool        |   9 +
 tools/bpf/bpftool/main.c                         |   3 +-
 tools/bpf/bpftool/main.h                         |   1 +
 tools/bpf/bpftool/perf.c                         | 244 +++++++++++++++
 tools/include/uapi/linux/bpf.h                   |  27 ++
 tools/lib/bpf/bpf.c                              |  24 ++
 tools/lib/bpf/bpf.h                              |   3 +
 tools/testing/selftests/bpf/test_progs.c         | 133 ++++++++
 tools/testing/selftests/bpf/trace_helpers.c      |  12 +
 tools/testing/selftests/bpf/trace_helpers.h      |   1 +
 23 files changed, 1222 insertions(+), 2 deletions(-)
 create mode 100644 samples/bpf/task_fd_query_kern.c
 create mode 100644 samples/bpf/task_fd_query_user.c
 create mode 100644 tools/bpf/bpftool/Documentation/bpftool-perf.rst
 create mode 100644 tools/bpf/bpftool/perf.c

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2.9.5