tools lib traceevent: Handle __print_hex(__get_dynamic_array(fieldname), len)

The kernel has a few events with a format similar to this excerpt:
        field:unsigned int len;     offset:12;      size:4; signed:0;
        field:__data_loc unsigned char[] data_array;  offset:16;      size:4; signed:0;
print fmt: "%s", __print_hex(__get_dynamic_array(data_array), REC->len)

trace-cmd could already parse that arg correctly, but print_str_arg()
was unable to handle the first parameter being a dynamic array. (It
just printed a "field not found" warning).

Teach print_str_arg's PRINT_HEX case to handle the nested
PRINT_DYNAMIC_ARRAY correctly. The output now matches the kernel's own
formatting for this case.
Signed-off-by: Howard Cochran <hcochran@lexmark.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1381503349-12271-1-git-send-email-hcochran@lexmark.com
[ Removed "polish compare", we don't do that here ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/event-parse.c

@@ -3588,6 +3588,13 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
 		}
 		break;
 	case PRINT_HEX:
+		if (arg->hex.field->type == PRINT_DYNAMIC_ARRAY) {
+			unsigned long offset;
+			offset = pevent_read_number(pevent,
+				data + arg->hex.field->dynarray.field->offset,
+				arg->hex.field->dynarray.field->size);
+			hex = data + (offset & 0xffff);
+		} else {
 			field = arg->hex.field->field.field;
 			if (!field) {
 				str = arg->hex.field->field.name;
@@ -3597,6 +3604,7 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
 				arg->hex.field->field.field = field;
 			}
 			hex = data + field->offset;
+		}
 		len = eval_num_arg(data, size, event, arg->hex.size);
 		for (i = 0; i < len; i++) {
 			if (i)