tracing: Fix double CPP substitution in TRACE_EVENT_FN

TRACE_EVENT_FN relays on TRACE_EVENT by reprocessing its parameters
into the ftrace events CPP macro. This leads to a double substitution
in some cases.

For example, a bad consequence is a format always prefixed by
"%s, %s\n" for every TRACE_EVENT_FN based events.

Eg:
	cat /debug/tracing/events/syscalls/sys_enter/format
	[...]
	print fmt: "%s, %s\n", "\"NR %ld (%lx, %lx, %lx, %lx, %lx, %lx)\"",\
	"REC->id, REC->args[0], REC->args[1], REC->args[2], REC->args[3],\
	REC->args[4], REC->args[5]"

This creates a failure in post-processing tools such as perf trace or
trace-cmd.

Then drop this double substitution and replace it by a new __cpparg()
macro that relays CPP arguments containing commas.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Josh Stone <jistone@redhat.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Jason Baron <jbaron@redhat.com>
LKML-Reference: <1251413406-6704-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 6 deletions

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 360a77ad79e1..57c56a998ee6 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -45,14 +45,15 @@
         };                                                      \
         static struct ftrace_event_call event_##name
 
+#undef __cpparg
+#define __cpparg(arg...) arg
+
 /* Callbacks are meaningless to ftrace. */
 #undef TRACE_EVENT_FN
-#define TRACE_EVENT_FN(name, proto, args, tstruct,              \
-                assign, print, reg, unreg)                      \
-        TRACE_EVENT(name, TP_PROTO(proto), TP_ARGS(args),       \
-                TP_STRUCT__entry(tstruct),                      \
-                TP_fast_assign(assign),                         \
-                TP_printk(print))
+#define TRACE_EVENT_FN(name, proto, args, tstruct,                      \
+                assign, print, reg, unreg)                              \
+        TRACE_EVENT(name, __cpparg(proto), __cpparg(args),              \
+                __cpparg(tstruct), __cpparg(assign), __cpparg(print))   \
 
 #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)