From 62823da1bd46f24e2b498513a809011dfe16cd9b Mon Sep 17 00:00:00 2001

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Date: Tue, 8 Jun 2021 17:27:44 -0400

Subject: [PATCH] libtraceevent: Handle parsing of "(REC)->" case

If a trace event wraps the special __entry variable to dereference it with

parenthesis, it shows up in the trace event format file wrapping the

"(REC)" as well. For example, the "func_repeats" event passed the __entry

into a helper macro in the TP_printk() portion, and the macro correctly

wrapped its parameter in parenthesis. This caused the output to show:

 "(((u64)(REC)->top_delta_ts << 32) | (REC)->bottom_delta_ts)"

The parser then failed to parse the "(REC)->" portion, as it expected the

"->" to appear directly after the "REC". This is not a requirement, and

the parser should be able to handle such cases.

When this occurred, trace-cmd would error with the following message:

trace-cmd: No such file or directory

  Error: expected type 4 but read 5

Link: https://lore.kernel.org/linux-trace-devel/20210608172744.796e93b7@gandalf.local.home

Fixes: 6582b0a ("tools/events: Add files to create libtraceevent.a")

Reported-by: Julia Lawall <julia.lawall@inria.fr>

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

---

 src/event-parse.c | 27 ++++++++++++++++++++++++---

 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/event-parse.c b/src/event-parse.c

index 97c1a97..1217491 100644

--- a/src/event-parse.c

+++ b/src/event-parse.c

@@ -2311,8 +2311,19 @@ process_entry(struct tep_event *event __maybe_unused, struct tep_print_arg *arg,

 	char *field;

 	char *token;

-	if (read_expected(TEP_EVENT_OP, "->") < 0)

-		goto out_err;

+	type = read_token_item(&token);

+	/*

+	 * Check if REC happens to be surrounded by parenthesis, and

+	 * return if that's the case, as "(REC)->" is valid.

+	 * but return TEP_EVENT_ITEM.

+	 */

+	if (type == TEP_EVENT_DELIM && strcmp(token, ")") == 0) {

+		*tok = token;

+		return TEP_EVENT_ITEM;

+	}

+

+	if (test_type_token(type, token,  TEP_EVENT_OP, "->"))

+		goto out_free;

 	if (read_expect_type(TEP_EVENT_ITEM, &token) < 0)

 		goto out_free;

@@ -2338,7 +2349,6 @@ process_entry(struct tep_event *event __maybe_unused, struct tep_print_arg *arg,

  out_free:

 	free_token(token);

- out_err:

 	*tok = NULL;

 	return TEP_EVENT_ERROR;

 }

@@ -3033,6 +3043,17 @@ process_paren(struct tep_event *event, struct tep_print_arg *arg, char **tok)

 	if (type == TEP_EVENT_ERROR)

 		goto out_free;

+	/*

+	 * If REC is surrounded by parenthesis, the process_arg()

+	 * will return TEP_EVENT_ITEM with token == ")". In

+	 * this case, we need to continue processing the item

+	 * and return.

+	 */

+	if (type == TEP_EVENT_ITEM && strcmp(token, ")") == 0) {

+		free_token(token);

+		return process_entry(event, arg, tok);

+	}

+

 	if (test_type_token(type, token, TEP_EVENT_DELIM, ")"))

 		goto out_free;

-- 

2.31.1