tracing: Allow syscall trace events for non privileged users

As for the raw syscalls events, individual syscall events won't
leak system wide information on task bound tracing. Allow non
privileged users to use them in such workflow.

Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Jason Baron <[email protected]>

Author: fweisbec

include/linux/ftrace_event.h

@@ -198,6 +198,14 @@ struct ftrace_event_call {
 #endif
 };
 
+#define __TRACE_EVENT_FLAGS(name, value)				\
+	static int __init trace_init_flags_##name(void)			\
+	{								\
+		event_##name.flags = value;				\
+		return 0;						\
+	}								\
+	early_initcall(trace_init_flags_##name);
+
 #define PERF_MAX_TRACE_SIZE	2048
 
 #define MAX_FILTER_PRED		32

include/linux/syscalls.h

@@ -137,7 +137,8 @@ extern struct trace_event_functions exit_syscall_print_funcs;
 		.class			= &event_class_syscall_enter,	\
 		.event.funcs            = &enter_syscall_print_funcs,	\
 		.data			= (void *)&__syscall_meta_##sname,\
-	}
+	};								\
+	__TRACE_EVENT_FLAGS(enter_##sname, TRACE_EVENT_FL_CAP_ANY)
 
 #define SYSCALL_TRACE_EXIT_EVENT(sname)					\
 	static struct syscall_metadata					\
@@ -152,7 +153,8 @@ extern struct trace_event_functions exit_syscall_print_funcs;
 		.class			= &event_class_syscall_exit,	\
 		.event.funcs		= &exit_syscall_print_funcs,	\
 		.data			= (void *)&__syscall_meta_##sname,\
-	}
+	};								\
+	__TRACE_EVENT_FLAGS(exit_##sname, TRACE_EVENT_FL_CAP_ANY)
 
 #define SYSCALL_METADATA(sname, nb)				\
 	SYSCALL_TRACE_ENTER_EVENT(sname);			\

include/trace/ftrace.h

@@ -84,12 +84,7 @@
 
 #undef TRACE_EVENT_FLAGS
 #define TRACE_EVENT_FLAGS(name, value)					\
-	static int __init trace_init_flags_##name(void)			\
-	{								\
-		event_##name.flags = value;				\
-		return 0;						\
-	}								\
-	early_initcall(trace_init_flags_##name);
+	__TRACE_EVENT_FLAGS(name, value)
 
 #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)