linux-kernel - [PATCH] tools lib traceevent: add checks for returned EVENT

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Date:	Mon, 3 Aug 2015 13:08:05 -0400
From:	Dean Nelson <dnelson@...hat.com>
To:	a.p.zijlstra@...llo.org, mingo@...hat.com, rostedt@...dmis.org,
	acme@...nel.org
Cc:	linux-kernel@...r.kernel.org, jolsa@...nel.org
Subject: [PATCH] tools lib traceevent: add checks for returned EVENT_ERROR type

Running the following perf-stat command on an arm64 system produces the
following result...

  [root@...ch64 ~]# perf stat -e kmem:mm_page_alloc -a sleep 1
    Warning: [kmem:mm_page_alloc] function sizeof not defined
    Warning: Error: expected type 4 but read 0
  Segmentation fault
  [root@...ch64 ~]#

The second warning message and SIGSEGV stem from the issue expressed in the
first warning message, and are the result of ignoring the EVENT_ERROR type
returned back through the call chain.

Dealing with the first warning message is beyond the scope of this patch. But
the second warning is addressed by this patch's first hunk. And the SIGSEGV is
eliminated by its second hunk.

Signed-off-by: Dean Nelson <dnelson@...hat.com>
---
 tools/lib/traceevent/event-parse.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index cc25f05..72e2933 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -1680,6 +1680,9 @@ process_cond(struct event_format *event, struct print_arg *top, char **tok)
 	type = process_arg(event, left, &token);
 
  again:
+	if (type == EVENT_ERROR)
+		goto out_free;
+
 	/* Handle other operations in the arguments */
 	if (type == EVENT_OP && strcmp(token, ":") != 0) {
 		type = process_op(event, left, &token);
@@ -1940,7 +1943,7 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
 
 		type = process_arg_token(event, right, tok, type);
 
-		if (right->type == PRINT_OP &&
+		if (type != EVENT_ERROR && right->type == PRINT_OP &&
 		    get_op_prio(arg->op.op) < get_op_prio(right->op.op)) {
 			struct print_arg tmp;
 
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