This patch set adds BPF iterator support for UNIX domain socket.  The first
patch implements it, and the second adds "%c" support for BPF_SEQ_PRINTF().

Thanks to Yonghong Song for the fix [0] for the LLVM code gen.  The fix
prevents the LLVM compiler from transforming the loop exit condition '<' to
'!=', where the upper bound is not a constant.  The transformation leads
the verifier to interpret it as an infinite loop.

And thanks to Andrii Nakryiko for its workaround [1].

[0] https://reviews.llvm.org/D107483
[1] https://lore.kernel.org/netdev/CAEf4BzZ3sVx1m1mOCcPcuVPiY6cWEAO=6VGHDiXEs9ZVD-RoLg@mail.gmail.com/ (local)


Changelog:
  v6:
  - Align the header "Inde" column
  - Change int vars to __u64 not to break test_progs-no_alu32
  - Move the if statement into the for loop not to depend on the fix [0]
  - Drop the README change
  - Modify "%c" positive test patterns

  v5:
  https://lore.kernel.org/netdev/20210812164557.79046-1-kuniyu@amazon.co.jp/ (local)
  - Align header line of bpf_iter_unix.c
  - Add test for "%c"

  v4:
  https://lore.kernel.org/netdev/20210810092807.13190-1-kuniyu@amazon.co.jp/ (local)
  - Check IS_BUILTIN(CONFIG_UNIX)
  - Support "%c" in BPF_SEQ_PRINTF()
  - Uncomment the code to print the name of the abstract socket
  - Mention the LLVM fix in README.rst
  - Remove the 'aligned' attribute in bpf_iter.h
  - Keep the format string on a single line

  v3:
  https://lore.kernel.org/netdev/20210804070851.97834-1-kuniyu@amazon.co.jp/ (local)
  - Export some functions for CONFIG_UNIX=m

  v2:
  https://lore.kernel.org/netdev/20210803011110.21205-1-kuniyu@amazon.co.jp/ (local)
  - Implement bpf_iter specific seq_ops->stop()
  - Add bpf_iter__unix in bpf_iter.h
  - Move common definitions in selftest to bpf_tracing_net.h
  - Include the code for abstract UNIX domain socket as comment in selftest
  - Use ASSERT_OK_PTR() instead of CHECK()
  - Make ternary operators on single line

  v1:
  https://lore.kernel.org/netdev/20210729233645.4869-1-kuniyu@amazon.co.jp/ (local)


Kuniyuki Iwashima (4):
  bpf: af_unix: Implement BPF iterator for UNIX domain socket.
  bpf: Support "%c" in bpf_bprintf_prepare().
  selftest/bpf: Implement sample UNIX domain socket iterator program.
  selftest/bpf: Extend the bpf_snprintf() test for "%c".

 include/linux/btf_ids.h                       |  3 +-
 kernel/bpf/helpers.c                          | 14 +++
 net/unix/af_unix.c                            | 93 +++++++++++++++++++
 .../selftests/bpf/prog_tests/bpf_iter.c       | 16 ++++
 .../selftests/bpf/prog_tests/snprintf.c       |  4 +-
 tools/testing/selftests/bpf/progs/bpf_iter.h  |  8 ++
 .../selftests/bpf/progs/bpf_iter_unix.c       | 80 ++++++++++++++++
 .../selftests/bpf/progs/bpf_tracing_net.h     |  4 +
 .../selftests/bpf/progs/test_snprintf.c       |  6 +-
 9 files changed, 223 insertions(+), 5 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_unix.c

-- 
2.30.2