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@xxxxxxxxxxxxxxxxx/T/
[1]
https://lore.kernel.org/all/20240430121805.104618-1-lulie@xxxxxxxxxxxxxxxxx/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
--
2.32.0.3.g01195cf9f
