tracing: Move fields from event to class structure

Move the defined fields from the event to the class structure.
Since the fields of the event are defined by the class they belong
to, it makes sense to have the class hold the information instead
of the individual events. The events of the same class would just
hold duplicate information.

After this change the size of the kernel dropped another 3K:

   text	   data	    bss	    dec	    hex	filename
4913961	1088356	 861512	6863829	 68bbd5	vmlinux.orig
4900252	1057412	 861512	6819176	 680d68	vmlinux.regs
4900375	1053380	 861512	6815267	 67fe23	vmlinux.fields

Although the text increased, this was mainly due to the C files
having to adapt to the change. This is a constant increase, where
new tracepoints will not increase the Text. But the big drop is
in the data size (as well as needed allocations to hold the fields).
This will give even more savings as more tracepoints are created.

Note, if just TRACE_EVENT()s are used and not DECLARE_EVENT_CLASS()
with several DEFINE_EVENT()s, then the savings will be lost. But
we are pushing developers to consolidate events with DEFINE_EVENT()
so this should not be an issue.

The kprobes define a unique class to every new event, but are dynamic
so it should not be a issue.

The syscalls however have a single class but the fields for the individual
events are different. The syscalls use a metadata to define the
fields. I moved the fields list from the event to the metadata and
added a "get_fields()" function to the class. This function is used
to find the fields. For normal events and kprobes, get_fields() just
returns a pointer to the fields list_head in the class. For syscall
events, it returns the fields list_head in the metadata for the event.

v2:  Fixed the syscall fields. The syscall metadata needs a list
     of fields for both enter and exit.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

4 files changed, 19 insertions, 15 deletions

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index e665ed38b4bf..479c3c1876e6 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -130,6 +130,9 @@ struct ftrace_event_class {
 #endif
         int                     (*reg)(struct ftrace_event_call *event,
                                        enum trace_reg type);
+        int                     (*define_fields)(struct ftrace_event_call *);
+        struct list_head        *(*get_fields)(struct ftrace_event_call *);
+        struct list_head        fields;
 };
 
 struct ftrace_event_call {
@@ -142,8 +145,6 @@ struct ftrace_event_call {
         int                     id;
         const char              *print_fmt;
         int                     (*raw_init)(struct ftrace_event_call *);
-        int                     (*define_fields)(struct ftrace_event_call *);
-        struct list_head        fields;
         int                     filter_active;
         struct event_filter     *filter;
         void                    *mod;
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index e3348c4c22e8..fd0f1f248cd8 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -122,7 +122,7 @@ extern struct ftrace_event_class event_class_syscall_enter;
 extern struct ftrace_event_class event_class_syscall_exit;
 
 #define SYSCALL_TRACE_ENTER_EVENT(sname)                                \
-        static const struct syscall_metadata __syscall_meta_##sname;    \
+        static struct syscall_metadata __syscall_meta_##sname;          \
         static struct ftrace_event_call                                 \
         __attribute__((__aligned__(4))) event_enter_##sname;            \
         static struct trace_event enter_syscall_print_##sname = {       \
@@ -136,12 +136,11 @@ extern struct ftrace_event_class event_class_syscall_exit;
                 .class                  = &event_class_syscall_enter,   \
                 .event                  = &enter_syscall_print_##sname, \
                 .raw_init               = init_syscall_trace,           \
-                .define_fields          = syscall_enter_define_fields,  \
                 .data                   = (void *)&__syscall_meta_##sname,\
         }
 
 #define SYSCALL_TRACE_EXIT_EVENT(sname)                                 \
-        static const struct syscall_metadata __syscall_meta_##sname;    \
+        static struct syscall_metadata __syscall_meta_##sname;          \
         static struct ftrace_event_call                                 \
         __attribute__((__aligned__(4))) event_exit_##sname;             \
         static struct trace_event exit_syscall_print_##sname = {        \
@@ -155,14 +154,13 @@ extern struct ftrace_event_class event_class_syscall_exit;
                 .class                  = &event_class_syscall_exit,    \
                 .event                  = &exit_syscall_print_##sname,  \
                 .raw_init               = init_syscall_trace,           \
-                .define_fields          = syscall_exit_define_fields,   \
                 .data                   = (void *)&__syscall_meta_##sname,\
         }
 
 #define SYSCALL_METADATA(sname, nb)                             \
         SYSCALL_TRACE_ENTER_EVENT(sname);                       \
         SYSCALL_TRACE_EXIT_EVENT(sname);                        \
-        static const struct syscall_metadata __used             \
+        static struct syscall_metadata __used                   \
           __attribute__((__aligned__(4)))                       \
           __attribute__((section("__syscalls_metadata")))       \
           __syscall_meta_##sname = {                            \
@@ -172,12 +170,14 @@ extern struct ftrace_event_class event_class_syscall_exit;
                 .args           = args_##sname,                 \
                 .enter_event    = &event_enter_##sname,         \
                 .exit_event     = &event_exit_##sname,          \
+                .enter_fields   = LIST_HEAD_INIT(__syscall_meta_##sname.enter_fields), \
+                .exit_fields    = LIST_HEAD_INIT(__syscall_meta_##sname.exit_fields), \
         };
 
 #define SYSCALL_DEFINE0(sname)                                  \
         SYSCALL_TRACE_ENTER_EVENT(_##sname);                    \
         SYSCALL_TRACE_EXIT_EVENT(_##sname);                     \
-        static const struct syscall_metadata __used             \
+        static struct syscall_metadata __used                   \
           __attribute__((__aligned__(4)))                       \
           __attribute__((section("__syscalls_metadata")))       \
           __syscall_meta__##sname = {                           \
@@ -185,6 +185,8 @@ extern struct ftrace_event_class event_class_syscall_exit;
                 .nb_args        = 0,                            \
                 .enter_event    = &event_enter__##sname,        \
                 .exit_event     = &event_exit__##sname,         \
+                .enter_fields   = LIST_HEAD_INIT(__syscall_meta__##sname.enter_fields), \
+                .exit_fields    = LIST_HEAD_INIT(__syscall_meta__##sname.exit_fields), \
         };                                                      \
         asmlinkage long sys_##sname(void)
 #else
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 26d132418f92..c7e3bcd5d52f 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -430,6 +430,9 @@ static inline notrace int ftrace_get_offsets_##call(			\
  *
  * static struct ftrace_event_class __used event_class_<template> = {
  *      .system                 = "<system>",
+ *      .define_fields          = ftrace_define_fields_<call>,
+ *      .fields                 = LIST_HEAD_INIT(event_class_##call.fields), \
+ *      .probe                  = ftrace_raw_event_##call,              \
  * };
  *
  * static struct ftrace_event_call __used
@@ -438,10 +441,8 @@ static inline notrace int ftrace_get_offsets_##call(			\
  *      .name                   = "<call>",
  *      .class                  = event_class_<template>,
  *      .raw_init               = trace_event_raw_init,
- *      .regfunc                = ftrace_raw_reg_event_<call>,
- *      .unregfunc              = ftrace_raw_unreg_event_<call>,
+ *      .event                  = &ftrace_event_type_<call>,
  *      .print_fmt              = print_fmt_<call>,
- *      .define_fields          = ftrace_define_fields_<call>,
  * };
  *
  */
@@ -563,6 +564,8 @@ _TRACE_PERF_PROTO(call, PARAMS(proto));					\
 static const char print_fmt_##call[] = print;                           \
 static struct ftrace_event_class __used event_class_##call = {          \
         .system                 = __stringify(TRACE_SYSTEM),            \
+        .define_fields          = ftrace_define_fields_##call,          \
+        .fields                 = LIST_HEAD_INIT(event_class_##call.fields),\
         .probe                  = ftrace_raw_event_##call,              \
         _TRACE_PERF_INIT(call)                                          \
 };
@@ -578,7 +581,6 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
         .event                  = &ftrace_event_type_##call,            \
         .raw_init               = trace_event_raw_init,                 \
         .print_fmt              = print_fmt_##template,                 \
-        .define_fields          = ftrace_define_fields_##template,      \
 };
 
 #undef DEFINE_EVENT_PRINT
@@ -594,7 +596,6 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
         .event                  = &ftrace_event_type_##call,            \
         .raw_init               = trace_event_raw_init,                 \
         .print_fmt              = print_fmt_##call,                     \
-        .define_fields          = ftrace_define_fields_##template,      \
 }
 
 #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
diff --git a/include/trace/syscall.h b/include/trace/syscall.h
index e5e5f48dbfb3..39647743cd95 100644
--- a/include/trace/syscall.h
+++ b/include/trace/syscall.h
@@ -25,6 +25,8 @@ struct syscall_metadata {
         int             nb_args;
         const char      **types;
         const char      **args;
+        struct list_head enter_fields;
+        struct list_head exit_fields;
 
         struct ftrace_event_call *enter_event;
         struct ftrace_event_call *exit_event;
@@ -34,8 +36,6 @@ struct syscall_metadata {
 extern unsigned long arch_syscall_addr(int nr);
 extern int init_syscall_trace(struct ftrace_event_call *call);
 
-extern int syscall_enter_define_fields(struct ftrace_event_call *call);
-extern int syscall_exit_define_fields(struct ftrace_event_call *call);
 extern int reg_event_syscall_enter(struct ftrace_event_call *call);
 extern void unreg_event_syscall_enter(struct ftrace_event_call *call);
 extern int reg_event_syscall_exit(struct ftrace_event_call *call);