bpf: Add typecast to raw_tracepoints to help BTF generation

When pahole converts dwarf to btf it emits only used types.
Wrap existing __bpf_trace_##template() function into
btf_trace_##template typedef and use it in type cast to
make gcc emits this type into dwarf. Then pahole will convert it to btf.
The "btf_trace_" prefix will be used to identify BTF enabled raw tracepoints.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191016032505.2089704-2-ast@kernel.org

diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
index d6e556c..b04c292 100644 (file)
--- a/include/trace/bpf_probe.h
+++ b/include/trace/bpf_probe.h
@@ -74,11 +74,12 @@ 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 *)__bpf_trace_##template,               \
+       .bpf_func       = (void *)(btf_trace_##call)__bpf_trace_##template,     \
        .num_args       = COUNT_ARGS(args),                             \
        .writable_size  = size,                                         \
 };