[PATCH bpf-next v3 0/5] bpf: Allow skb dynptr for tp_btf

[Philo Lu <lulie@linux.alibaba.com>]

This makes bpf_dynptr_from_skb usable for tp_btf, so that we can easily
parse skb in tracepoints. This has been discussed in [0], and Martin
suggested to use dynptr (instead of helpers like bpf_skb_load_bytes).

For safety, skb dynptr shouldn't be used in fentry/fexit. This is achieved
by add KF_TRUSTED_ARGS flag in bpf_dynptr_from_skb defination, because
pointers passed by tracepoint are trusted (PTR_TRUSTED) while those of
fentry/fexit are not.

Another problem raises that NULL pointers could be passed to tracepoint,
such as trace_tcp_send_reset, and we need to recognize them. This is done
by add a "__nullable" suffix in the func_proto of the tracepoint,
discussed in [1].

2 Test cases are added, one for "__nullable" suffix, and the other for
using skb dynptr in tp_btf.

changelog
v2 -> v3 (Andrii Nakryiko):
 Patch 1:
  - Remove prog type check in prog_arg_maybe_null()
  - Add bpf_put_raw_tracepoint() after get()
  - Use kallsyms_lookup() instead of sprintf("%ps")
 Patch 2: Add separate test "tp_btf_nullable", and use full failure msg
v1 -> v2:
 - Add "__nullable" suffix support (Alexei Starovoitov)
 - Replace "struct __sk_buff*" with "void*" in test (Martin KaFai Lau)

[0]
https://lore.kernel.org/all/20240205121038.41344-1-lulie@linux.alibaba.com/T/
[1]
https://lore.kernel.org/all/20240430121805.104618-1-lulie@linux.alibaba.com/T/

Philo Lu (5):
  bpf: Support __nullable argument suffix for tp_btf
  selftests/bpf: Add test for __nullable suffix in tp_btf
  tcp: Use skb__nullable in trace_tcp_send_reset
  bpf: Allow bpf_dynptr_from_skb() for tp_btf
  selftests/bpf: Expand skb dynptr selftests for tp_btf

 include/trace/events/tcp.h                    | 12 +++----
 kernel/bpf/btf.c                              |  9 +++++
 kernel/bpf/verifier.c                         | 36 ++++++++++++++++---
 net/core/filter.c                             |  3 +-
 .../bpf/bpf_testmod/bpf_testmod-events.h      |  6 ++++
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  2 ++
 .../testing/selftests/bpf/prog_tests/dynptr.c | 36 +++++++++++++++++--
 .../bpf/prog_tests/tp_btf_nullable.c          | 14 ++++++++
 .../testing/selftests/bpf/progs/dynptr_fail.c | 25 +++++++++++++
 .../selftests/bpf/progs/dynptr_success.c      | 23 ++++++++++++
 .../bpf/progs/test_tp_btf_nullable.c          | 24 +++++++++++++
 11 files changed, 177 insertions(+), 13 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/tp_btf_nullable.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_tp_btf_nullable.c

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2.32.0.3.g01195cf9f