tracing: Use seq_buf_hex_dump() to dump buffers

Without this, buffers can be printed with __print_array macro that has
no formatting options and can be hard to read. The other way is to
mimic formatting capability with multiple calls of trace event with one
call per row which gives performance impact and different timestamp in
each row.

Link: http://lkml.kernel.org/r/1573130738-29390-2-git-send-email-piotrx.maziarz@linux.intel.com

Signed-off-by: Piotr Maziarz <piotrx.maziarz@linux.intel.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_seq.c

@@ -376,3 +376,33 @@ int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
 	return seq_buf_to_user(&s->seq, ubuf, cnt);
 }
 EXPORT_SYMBOL_GPL(trace_seq_to_user);
+
+int trace_seq_hex_dump(struct trace_seq *s, const char *prefix_str,
+		       int prefix_type, int rowsize, int groupsize,
+		       const void *buf, size_t len, bool ascii)
+{
+		unsigned int save_len = s->seq.len;
+
+	if (s->full)
+		return 0;
+
+	__trace_seq_init(s);
+
+	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
+		s->full = 1;
+		return 0;
+	}
+
+	seq_buf_hex_dump(&(s->seq), prefix_str,
+		   prefix_type, rowsize, groupsize,
+		   buf, len, ascii);
+
+	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
+		s->seq.len = save_len;
+		s->full = 1;
+		return 0;
+	}
+
+	return 1;
+}
+EXPORT_SYMBOL(trace_seq_hex_dump);