perf tools: Allow expressions in __print_symbolic() fields

The __print_symbolic() function takes a sequence of key-value pairs for
pretty-printing a constant.  The new kvm:kvm_exit print fmt uses the
expression:

  __print_symbolic(..., { 0x040 + 1, "DB excp" }, ...)

Currently only atoms are supported and this print fmt fails to parse.
This patch adds support for expressions instead of just atoms so that
0x040 + 1 is parsed successfully.  Also add arg_num_eval() support for
the '+' operator.

Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1315148939-14313-1-git-send-email-stefanha@linux.vnet.ibm.com
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/trace-event-parse.c

@@ -1423,6 +1423,11 @@ static long long arg_num_eval(struct print_arg *arg)
 				die("unknown op '%s'", arg->op.op);
 			}
 			break;
+		case '+':
+			left = arg_num_eval(arg->op.left);
+			right = arg_num_eval(arg->op.right);
+			val = left + right;
+			break;
 		default:
 			die("unknown op '%s'", arg->op.op);
 		}
@@ -1483,6 +1488,13 @@ process_fields(struct event *event, struct print_flag_sym **list, char **tok)
 
 		free_token(token);
 		type = process_arg(event, arg, &token);
+
+		if (type == EVENT_OP)
+			type = process_op(event, arg, &token);
+
+		if (type == EVENT_ERROR)
+			goto out_free;
+
 		if (test_type_token(type, token, EVENT_DELIM, ","))
 			goto out_free;