[bpf-next,0/5] sleepable uprobe support

Message

Delyan Kratunov April 28, 2022, 4:53 p.m. UTC

This series implements support for sleepable uprobe programs.
Key work is in patches 2 and 3, the rest is plumbing and tests.

The main observation is that the only obstacle in the way of sleepable uprobe
programs is not the uprobe infrastructure, which already runs in a user context,
but the rcu usage around bpf_prog_array.

Details are in patch 2 but the tl;dr is that we chain trace_tasks and normal rcu
grace periods when releasing to array to accommodate users of either rcu type.
This introduces latency on non-sleepable users but that's deemed acceptable, given
recent benchmarks by Andrii [1]. We're a couple of orders of magnitude under
the rate of bpf_prog_array churn that would raise flags (~1MM/s per Paul).

  [1]: https://lore.kernel.org/bpf/CAEf4BzbpjN6ca7D9KOTiFPOoBYkciYvTz0UJNp5c-_3ptm=[e-mail]/

Delyan Kratunov (5):
  bpf: move bpf_prog to bpf.h
  bpf: implement sleepable uprobes by chaining tasks and normal rcu
  bpf: allow sleepable uprobe programs to attach
  libbpf: add support for sleepable kprobe and uprobe programs
  selftests/bpf: add tests for sleepable kprobes and uprobes

 include/linux/bpf.h                           | 96 +++++++++++++++++++
 include/linux/filter.h                        | 34 -------
 include/linux/trace_events.h                  |  1 +
 kernel/bpf/core.c                             | 10 +-
 kernel/bpf/syscall.c                          |  8 ++
 kernel/bpf/verifier.c                         |  4 +-
 kernel/trace/bpf_trace.c                      | 23 +++++
 kernel/trace/trace_uprobe.c                   |  4 +-
 tools/lib/bpf/libbpf.c                        | 10 +-
 .../selftests/bpf/prog_tests/attach_probe.c   | 35 +++++++
 .../selftests/bpf/progs/test_attach_probe.c   | 44 +++++++++
 11 files changed, 228 insertions(+), 41 deletions(-)

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2.35.1