tools lib traceevent: Handle dynamic array's element size properly

Fixing the dynamic array format field parsing.

Currently the event_read_fields function could segfault while parsing
dynamic array other than string type. The reason is the event->pevent
does not need to be set and gets dereferenced unconditionaly.

Also adding proper initialization of field->elementsize based on the
parsed dynamic type.

Signed-off-by: Jiri Olsa <[e-mail]>
Acked-by: Steven Rostedt <[e-mail]>
Cc: Corey Ashford <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
[ committer note: Made a char pointer parameter const, as requested by Steven ]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/lib/traceevent/event-parse.c

···
 	return 0;
 }
 
+static unsigned int type_size(const char *name)
+{
+	/* This covers all FIELD_IS_STRING types. */
+	static struct {
+		const char *type;
+		unsigned int size;
+	} table[] = {
+		{ "u8",   1 },
+		{ "u16",  2 },
+		{ "u32",  4 },
+		{ "u64",  8 },
+		{ "s8",   1 },
+		{ "s16",  2 },
+		{ "s32",  4 },
+		{ "s64",  8 },
+		{ "char", 1 },
+		{ },
+	};
+	int i;
+
+	for (i = 0; table[i].type; i++) {
+		if (!strcmp(table[i].type, name))
+			return table[i].size;
+	}
+
+	return 0;
+}
+
 static int event_read_fields(struct event_format *event, struct format_field **fields)
 {
 	struct format_field *field = NULL;
···
 	int count = 0;
 
 	do {
+		unsigned int size_dynamic = 0;
+
 		type = read_token(&token);
 		if (type == EVENT_NEWLINE) {
 			free_token(token);
···
 				field->type = new_type;
 				strcat(field->type, " ");
 				strcat(field->type, field->name);
+				size_dynamic = type_size(field->name);
 				free_token(field->name);
 				strcat(field->type, brackets);
 				field->name = token;
···
 		if (field->flags & FIELD_IS_ARRAY) {
 			if (field->arraylen)
 				field->elementsize = field->size / field->arraylen;
+			else if (field->flags & FIELD_IS_DYNAMIC)
+				field->elementsize = size_dynamic;
 			else if (field->flags & FIELD_IS_STRING)
 				field->elementsize = 1;
-			else
-				field->elementsize = event->pevent->long_size;
+			else if (field->flags & FIELD_IS_LONG)
+				field->elementsize = event->pevent ?
+						     event->pevent->long_size :
+						     sizeof(long);
 		} else
 			field->elementsize = field->size;