Merge branch 'bpf: Allow skb dynptr for tp_btf'

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Philo Lu says:

====================
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/
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

...

This commit is contained in:

Martin KaFai Lau 2024-09-11 08:48:50 -07:00

parent 23dc986732 83dff60171

commit fdfd9d82a4

11 changed files with 172 additions and 13 deletions

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12

include/trace/events/tcp.h

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3

kernel/bpf/btf.c

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36

kernel/bpf/verifier.c

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3

net/core/filter.c

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6

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h

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2

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c

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37

tools/testing/selftests/bpf/prog_tests/dynptr.c

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14

tools/testing/selftests/bpf/prog_tests/tp_btf_nullable.c

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25

tools/testing/selftests/bpf/progs/dynptr_fail.c

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23

tools/testing/selftests/bpf/progs/dynptr_success.c

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24

tools/testing/selftests/bpf/progs/test_tp_btf_nullable.c

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