linux-kernel - [PATCH v2 09/13] tracing: define TRACE_DEFINE_SIZEOF() macro to map sizeof's to their values

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Date:   Wed, 14 Jun 2017 17:27:25 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org, rostedt@...dmis.org, mingo@...hat.com,
        rusty@...tcorp.com.au, jeyu@...hat.com,
        kirill.shutemov@...ux.intel.com, christoffer.dall@...aro.org,
        marc.zyngier@....com, jcm@...masters.org, clemens@...isch.de,
        perex@...ex.cz
Subject: [PATCH v2 09/13] tracing: define TRACE_DEFINE_SIZEOF() macro to map sizeof's to their values

Perf has a problem that if sizeof() macros are used within TRACE_EVENT()
macro's they end up in userspace as "sizeof(kernel structure)" which
cannot properly be parsed. Add a macro which can forward this data
through the eval_map for userspace utilization.

Signed-off-by: Jeremy Linton <jeremy.linton@....com>
---
 include/linux/tracepoint.h   |  1 +
 include/trace/trace_events.h | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index f7b0f55..a26ffbe 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -88,6 +88,7 @@ extern void syscall_unregfunc(void);
 #define PARAMS(args...) args
 
 #define TRACE_DEFINE_ENUM(x)
+#define TRACE_DEFINE_SIZEOF(x)
 
 #endif /* _LINUX_TRACEPOINT_H */
 
diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
index 49cce5f..3976fa1 100644
--- a/include/trace/trace_events.h
+++ b/include/trace/trace_events.h
@@ -46,6 +46,19 @@ TRACE_MAKE_SYSTEM_STR();
 	__attribute__((section("_ftrace_eval_map")))	\
 	*TRACE_SYSTEM##_##a = &__##TRACE_SYSTEM##_##a
 
+#undef TRACE_DEFINE_SIZEOF
+#define TRACE_DEFINE_SIZEOF(a)				\
+	static struct trace_eval_map __used __initdata	\
+	__##TRACE_SYSTEM##_##a =			\
+	{						\
+		.system = TRACE_SYSTEM_STRING,		\
+		.eval_string = "sizeof(" #a ")",	\
+		.eval_value = sizeof(a)			\
+	};						\
+	static struct trace_eval_map __used		\
+	__attribute__((section("_ftrace_eval_map")))	\
+	*TRACE_SYSTEM##_##a = &__##TRACE_SYSTEM##_##a
+
 /*
  * DECLARE_EVENT_CLASS can be used to add a generic function
  * handlers for events. That is, if all events have the same
@@ -158,6 +171,9 @@ TRACE_MAKE_SYSTEM_STR();
 #undef TRACE_DEFINE_ENUM
 #define TRACE_DEFINE_ENUM(a)
 
+#undef TRACE_DEFINE_SIZEOF
+#define TRACE_DEFINE_SIZEOF(a)
+
 #undef __field
 #define __field(type, item)
 
-- 
2.9.4