From: Andrii Nakryiko <andriin@xxxxxx> [ Upstream commit 441420a1f0b3031f228453697406c86f110e59d4 ] btf_trace_xxx types, crucial for tp_btf BPF programs (raw tracepoint with verifier-checked direct memory access), have to be preserved in kernel BTF to allow verifier do its job and enforce type/memory safety. It was reported ([0]) that for kernels built with Clang current type-casting approach doesn't preserve these types. This patch fixes it by declaring an anonymous union for each registered tracepoint, capturing both struct bpf_raw_event_map information, as well as recording btf_trace_##call type reliably. Structurally, it's still the same content as for a plain struct bpf_raw_event_map, so no other changes are necessary. [0] https://github.com/iovisor/bcc/issues/2770#issuecomment-591007692 Fixes: e8c423fb31fa ("bpf: Add typecast to raw_tracepoints to help BTF generation") Reported-by: Wenbo Zhang <ethercflow@xxxxxxxxx> Signed-off-by: Andrii Nakryiko <andriin@xxxxxx> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Acked-by: Yonghong Song <yhs@xxxxxx> Link: https://lore.kernel.org/bpf/20200301081045.3491005-2-andriin@xxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- include/trace/bpf_probe.h | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h index b04c292709730..1ce3be63add1f 100644 --- a/include/trace/bpf_probe.h +++ b/include/trace/bpf_probe.h @@ -75,13 +75,17 @@ static inline void bpf_test_probe_##call(void) \ check_trace_callback_type_##call(__bpf_trace_##template); \ } \ typedef void (*btf_trace_##call)(void *__data, proto); \ -static struct bpf_raw_event_map __used \ - __attribute__((section("__bpf_raw_tp_map"))) \ -__bpf_trace_tp_map_##call = { \ - .tp = &__tracepoint_##call, \ - .bpf_func = (void *)(btf_trace_##call)__bpf_trace_##template, \ - .num_args = COUNT_ARGS(args), \ - .writable_size = size, \ +static union { \ + struct bpf_raw_event_map event; \ + btf_trace_##call handler; \ +} __bpf_trace_tp_map_##call __used \ +__attribute__((section("__bpf_raw_tp_map"))) = { \ + .event = { \ + .tp = &__tracepoint_##call, \ + .bpf_func = __bpf_trace_##template, \ + .num_args = COUNT_ARGS(args), \ + .writable_size = size, \ + }, \ }; #define FIRST(x, ...) x -- 2.20.1
