btf_trace_fix.patch

From e4172808f4c4389cf8a86c2753e4a42894798c0a Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andriin@fb.com>
Date: Tue, 25 Feb 2020 10:41:33 -0800
Subject: [PATCH bpf-next] bpf: use more reliable BTF_TYPE_EMIT to preserve
 btf_trace_xxx typedefs

BTF_TYPE_EMIT has more reliable mechanism to ensure compiler preserve
requested type information. It's already used by struct_ops mechanisms with
great reliability. Switch raw tracepoints to use the same mechanism.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 include/trace/bpf_probe.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
index b04c29270973..3f55e27dfe63 100644
--- a/include/trace/bpf_probe.h
+++ b/include/trace/bpf_probe.h
@@ -55,12 +55,18 @@
 /* tracepoints with more than 12 arguments will hit build error */
 #define CAST_TO_U64(...) CONCATENATE(__CAST, COUNT_ARGS(__VA_ARGS__))(__VA_ARGS__)
 
+#ifndef BTF_TYPE_EMIT
+#define BTF_TYPE_EMIT(type) ((void)(type *)0)
+#endif
+
 #undef DECLARE_EVENT_CLASS
 #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print)	\
+typedef void (*btf_trace_##call)(void *__data, proto);			\
 static notrace void							\
 __bpf_trace_##call(void *__data, proto)					\
 {									\
 	struct bpf_prog *prog = __data;					\
+	BTF_TYPE_EMIT(btf_trace_##call);				\
 	CONCATENATE(bpf_trace_run, COUNT_ARGS(args))(prog, CAST_TO_U64(args));	\
 }
 
@@ -74,12 +80,11 @@ 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,	\
+	.bpf_func	= __bpf_trace_##template,			\
 	.num_args	= COUNT_ARGS(args),				\
 	.writable_size	= size,						\
 };
-- 
2.17.1