[PATCH] libtraceevent: Fix backward compatibility with tep_print_arg_string

[Steven Rostedt <rostedt@xxxxxxxxxxx>]

From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>

It appears that trace-cmd 2.9.6 referenced the tep_print_arg_string to
get to the offset, which was removed by libtraceevent commit 512d7be1
("libtraceevent: Add __rel_loc relative location attribute support").
Add the offset back to both tep_print_arg_string and to
tep_print_arg_bitmask (yeah, it adds a hole in the structure), for
backward compatibility.

Reported-by: Vitaly Chikunov <vt@xxxxxxxxxxxx>
Fixes: 512d7be1 ("libtraceevent: Add __rel_loc relative location attribute support")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215521
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
 include/traceevent/event-parse.h |  2 ++
 src/event-parse.c                | 10 ++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/traceevent/event-parse.h b/include/traceevent/event-parse.h
index 27cba06f55cb..68b2f4383b42 100644
--- a/include/traceevent/event-parse.h
+++ b/include/traceevent/event-parse.h
@@ -154,11 +154,13 @@ struct tep_print_arg_atom {
 
 struct tep_print_arg_string {
 	char			*string;
+	int			offset;		// for backward compatibility
 	struct tep_format_field	*field;
 };
 
 struct tep_print_arg_bitmask {
 	char			*bitmask;
+	int			offset;		// for backward compatibility
 	struct tep_format_field	*field;
 };
 
diff --git a/src/event-parse.c b/src/event-parse.c
index d3e43e5c11f8..2b346a5de16e 100644
--- a/src/event-parse.c
+++ b/src/event-parse.c
@@ -3135,6 +3135,7 @@ process_str(struct tep_event *event __maybe_unused, struct tep_print_arg *arg,
 
 	arg->type = TEP_PRINT_STRING;
 	arg->string.string = token;
+	arg->string.offset = -1;
 	arg->string.field = NULL;
 
 	if (read_expected(TEP_EVENT_DELIM, ")") < 0)
@@ -3164,6 +3165,7 @@ process_bitmask(struct tep_event *event __maybe_unused, struct tep_print_arg *ar
 
 	arg->type = TEP_PRINT_BITMASK;
 	arg->bitmask.bitmask = token;
+	arg->bitmask.offset = -1;
 	arg->bitmask.field = NULL;
 
 	if (read_expected(TEP_EVENT_DELIM, ")") < 0)
@@ -4444,8 +4446,10 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
 	case TEP_PRINT_TYPE:
 		break;
 	case TEP_PRINT_STRING: {
-		if (!arg->string.field)
+		if (!arg->string.field) {
 			arg->string.field = tep_find_any_field(event, arg->string.string);
+			arg->string.offset = arg->string.field->offset;
+		}
 		if (!arg->string.field)
 			break;
 		dynamic_offset_field(tep, arg->string.field, data, size, &offset, &len);
@@ -4459,8 +4463,10 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
 		print_str_to_seq(s, format, len_arg, arg->string.string);
 		break;
 	case TEP_PRINT_BITMASK: {
-		if (!arg->bitmask.field)
+		if (!arg->bitmask.field) {
 			arg->bitmask.field = tep_find_any_field(event, arg->bitmask.bitmask);
+			arg->bitmask.offset = arg->bitmask.field->offset;
+		}
 		if (!arg->bitmask.field)
 			break;
 		dynamic_offset_field(tep, arg->bitmask.field, data, size, &offset, &len);
-- 
2.33.0