ftrace: Rework event_create_dir()

Rework event_create_dir() to use an array of static data instead of
function pointers where possible.

The problem is that it would call the function pointer on module load
before parse_args(), possibly even before jump_labels were initialized.
Luckily the generated functions don't use jump_labels but it still seems
fragile. It also gets in the way of changing when we make the module map
executable.

The generated function are basically calling trace_define_field() with a
bunch of static arguments. So instead of a function, capture these
arguments in a static array, avoiding the function call.

Now there are a number of cases where the fields are dynamic (syscall
arguments, kprobes and uprobes), in which case a static array does not
work, for these we preserve the function call. Luckily all these cases
are not related to modules and so we can retain the function call for
them.

Also fix up all broken tracepoint definitions that now generate a
compile error.

Tested-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191111132458.342979914@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 17 insertions, 1 deletions

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 30a8cdcfd4a4..a379255c14a9 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -187,6 +187,22 @@ enum trace_reg {
 
 struct trace_event_call;
 
+#define TRACE_FUNCTION_TYPE ((const char *)~0UL)
+
+struct trace_event_fields {
+	const char *type;
+	union {
+		struct {
+			const char *name;
+			const int  size;
+			const int  align;
+			const int  is_signed;
+			const int  filter_type;
+		};
+		int (*define_fields)(struct trace_event_call *);
+	};
+};
+
 struct trace_event_class {
 	const char		*system;
 	void			*probe;
@@ -195,7 +211,7 @@ struct trace_event_class {
 #endif
 	int			(*reg)(struct trace_event_call *event,
 				       enum trace_reg type, void *data);
-	int			(*define_fields)(struct trace_event_call *);
+	struct trace_event_fields *fields_array;
 	struct list_head	*(*get_fields)(struct trace_event_call *);
 	struct list_head	fields;
 	int			(*raw_init)(struct trace_event_call *);