tracing: Fix array size mismatch in format string

commit 87291347c49dc40aa339f587b209618201c2e527 upstream.

In event format strings, the array size is reported in two locations.
One in array subscript and then via the "size:" attribute. The values
reported there have a mismatch.

For e.g., in sched:sched_switch the prev_comm and next_comm character
arrays have subscript values as [32] where as the actual field size is
16.

name: sched_switch
ID: 301
format:
        field:unsigned short common_type;       offset:0;       size:2; signed:0;
        field:unsigned char common_flags;       offset:2;       size:1; signed:0;
        field:unsigned char common_preempt_count;       offset:3;       size:1;signed:0;
        field:int common_pid;   offset:4;       size:4; signed:1;

        field:char prev_comm[32];       offset:8;       size:16;        signed:1;
        field:pid_t prev_pid;   offset:24;      size:4; signed:1;
        field:int prev_prio;    offset:28;      size:4; signed:1;
        field:long prev_state;  offset:32;      size:8; signed:1;
        field:char next_comm[32];       offset:40;      size:16;        signed:1;
        field:pid_t next_pid;   offset:56;      size:4; signed:1;
        field:int next_prio;    offset:60;      size:4; signed:1;

After bisection, the following commit was blamed:
92edca0 tracing: Use direct field, type and system names

This commit removes the duplication of strings for field->name and
field->type assuming that all the strings passed in
__trace_define_field() are immutable. This is not true for arrays, where
the type string is created in event_storage variable and field->type for
all array fields points to event_storage.

Use __stringify() to create a string constant for the type string.

Also, get rid of event_storage and event_storage_mutex that are not
needed anymore.

also, an added benefit is that this reduces the overhead of events a bit more:

   text    data     bss     dec     hex filename
8424787 2036472 1302528 11763787         b3804b vmlinux
8420814 2036408 1302528 11759750         b37086 vmlinux.patched

Link: http://lkml.kernel.org/r/1392349908-29685-1-git-send-email-vnagarnaik@google.com

Cc: Laurent Chavey <chavey@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

2 files changed, 2 insertions, 11 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index b03b1f897b5e..bc1bd20f7942 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -27,12 +27,6 @@
 
 DEFINE_MUTEX(event_mutex);
 
-DEFINE_MUTEX(event_storage_mutex);
-EXPORT_SYMBOL_GPL(event_storage_mutex);
-
-char event_storage[EVENT_STORAGE_SIZE];
-EXPORT_SYMBOL_GPL(event_storage);
-
 LIST_HEAD(ftrace_events);
 static LIST_HEAD(ftrace_common_fields);
 
diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
index d21a74670088..d7d0b50b1b70 100644
--- a/kernel/trace/trace_export.c
+++ b/kernel/trace/trace_export.c
@@ -95,15 +95,12 @@ static void __always_unused ____ftrace_check_##name(void)		\
 #undef __array
 #define __array(type, item, len)					\
 	do {								\
+		char *type_str = #type"["__stringify(len)"]";		\
 		BUILD_BUG_ON(len > MAX_FILTER_STR_VAL);			\
-		mutex_lock(&event_storage_mutex);			\
-		snprintf(event_storage, sizeof(event_storage),		\
-			 "%s[%d]", #type, len);				\
-		ret = trace_define_field(event_call, event_storage, #item, \
+		ret = trace_define_field(event_call, type_str, #item,	\
 				 offsetof(typeof(field), item),		\
 				 sizeof(field.item),			\
 				 is_signed_type(type), filter_type);	\
-		mutex_unlock(&event_storage_mutex);			\
 		if (ret)						\
 			return ret;					\
 	} while (0);