tools lib traceevent: Honor operator priority

Currently it ignores operator priority and just sets processed args as a
right operand.  But it could result in priority inversion in case that
the right operand is also a operator arg and its priority is lower.

For example, following print format is from new kmem events.

  "page=%p", REC->pfn != -1UL ? (((struct page *)(0xffffea0000000000UL)) + (REC->pfn)) : ((void *)0)

But this was treated as below:

  REC->pfn != ((null - 1UL) ? ((struct page *)0xffffea0000000000UL + REC->pfn) : (void *) 0)

In this case, the right arg was '?' operator which has lower priority.
But it just sets the whole arg so making the output confusing - page was
always 0 or 1 since that's the result of logical operation.

With this patch, it can handle it properly like following:

  ((REC->pfn != (null - 1UL)) ? ((struct page *)0xffffea0000000000UL + REC->pfn) : (void *) 0)

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/1428298576-9785-10-git-send-email-namhyung@kernel.org
[ Replaced 'swap' with 'rotate' in a comment as requested by Steve and agreed by Namhyung ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index 6d31b6419d37..12a7e2a40c89 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -1939,7 +1939,22 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
                         goto out_warn_free;
 
                 type = process_arg_token(event, right, tok, type);
-                arg->op.right = right;
+
+                if (right->type == PRINT_OP &&
+                    get_op_prio(arg->op.op) < get_op_prio(right->op.op)) {
+                        struct print_arg tmp;
+
+                        /* rotate ops according to the priority */
+                        arg->op.right = right->op.left;
+
+                        tmp = *arg;
+                        *arg = *right;
+                        *right = tmp;
+
+                        arg->op.left = right;
+                } else {
+                        arg->op.right = right;
+                }
 
         } else if (strcmp(token, "[") == 0) {