Subject: [PATCH bpf-next v5 1/3] bpf: support writable context for bare tracepoint

From: Hou Tao <[email-masked]>
Date: Mon, 4 Oct 2021 17:48:55 +0800

From: Hou Tao <[email-masked]>

Commit 9df1c28bb752 ("bpf: add writable context for raw tracepoints")
supports writable context for tracepoint, but it misses the support
for bare tracepoint which has no associated trace event.

Bare tracepoint is defined by DECLARE_TRACE(), so adding a corresponding
DECLARE_TRACE_WRITABLE() macro to generate a definition in __bpf_raw_tp_map
section for bare tracepoint in a similar way to DEFINE_TRACE_WRITABLE().

Signed-off-by: Hou Tao <[email-masked]>
Acked-by: Andrii Nakryiko <[email-masked]>
---
 include/trace/bpf_probe.h | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
index a23be89119aa..a8e97f84b652 100644
--- a/include/trace/bpf_probe.h
+++ b/include/trace/bpf_probe.h
@@ -93,8 +93,7 @@ __section("__bpf_raw_tp_map") = {					\
 
 #define FIRST(x, ...) x
 
-#undef DEFINE_EVENT_WRITABLE
-#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size)	\
+#define __CHECK_WRITABLE_BUF_SIZE(call, proto, args, size)		\
 static inline void bpf_test_buffer_##call(void)				\
 {									\
 	/* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \
@@ -103,8 +102,12 @@ static inline void bpf_test_buffer_##call(void)				\
 	 */								\
 	FIRST(proto);							\
 	(void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args)));		\
-}									\
-__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
+}
+
+#undef DEFINE_EVENT_WRITABLE
+#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \
+	__CHECK_WRITABLE_BUF_SIZE(call, PARAMS(proto), PARAMS(args), size) \
+	__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
 
 #undef DEFINE_EVENT
 #define DEFINE_EVENT(template, call, proto, args)			\
@@ -119,9 +122,17 @@ __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
 	__BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args))		\
 	__DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), 0)
 
+#undef DECLARE_TRACE_WRITABLE
+#define DECLARE_TRACE_WRITABLE(call, proto, args, size) \
+	__CHECK_WRITABLE_BUF_SIZE(call, PARAMS(proto), PARAMS(args), size) \
+	__BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) \
+	__DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), size)
+
 #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
 
+#undef DECLARE_TRACE_WRITABLE
 #undef DEFINE_EVENT_WRITABLE
+#undef __CHECK_WRITABLE_BUF_SIZE
 #undef __DEFINE_EVENT
 #undef FIRST
 
-- 
2.20.1