From patchwork Tue Dec 8 03:55:02 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 553756 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 421E01402BD for ; Tue, 8 Dec 2015 15:00:16 +1100 (AEDT) Received: from localhost ([::1]:57695 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a69Rl-0004T7-Po for incoming@patchwork.ozlabs.org; Mon, 07 Dec 2015 23:00:13 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47996) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a69NE-0004Ju-Gg for qemu-devel@nongnu.org; Mon, 07 Dec 2015 22:55:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a69ND-0003YT-Cu for qemu-devel@nongnu.org; Mon, 07 Dec 2015 22:55:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56080) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a69ND-0003Y9-6z for qemu-devel@nongnu.org; Mon, 07 Dec 2015 22:55:31 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id BBACDA0B2A; Tue, 8 Dec 2015 03:55:30 +0000 (UTC) Received: from red.redhat.com (ovpn-113-183.phx2.redhat.com [10.3.113.183]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id tB83tOM1007883; Mon, 7 Dec 2015 22:55:30 -0500 From: Eric Blake To: qemu-devel@nongnu.org Date: Mon, 7 Dec 2015 20:55:02 -0700 Message-Id: <1449546921-6378-13-git-send-email-eblake@redhat.com> In-Reply-To: <1449546921-6378-1-git-send-email-eblake@redhat.com> References: <1449546921-6378-1-git-send-email-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: armbru@redhat.com, Michael Roth Subject: [Qemu-devel] [PATCH v7 12/31] qapi: Don't cast Enum* to int* X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org C compilers are allowed to represent enums as a smaller type than int, if all enum values fit in the smaller type. There are even compiler flags that force the use of this smaller representation, and using them changes the ABI of a binary. Therefore, our generated code for visit_type_ENUM() (for all qapi enums) was wrong for casting Enum* to int* when calling visit_type_enum(). It appears that no one has been doing this for qemu, because if they had, we are potentially dereferencing beyond bounds or even risking a SIGBUS on platforms where unaligned pointer dereferencing is fatal. Better is to avoid the practice entirely, and just use the correct types. This matches the fix for alternate qapi types, done earlier in "qapi: Simplify visiting of alternate types". Signed-off-by: Eric Blake --- v7: rebase on typo fix v6: new patch --- scripts/qapi-visit.py | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py index 4a4f67d..6bd188b 100644 --- a/scripts/qapi-visit.py +++ b/scripts/qapi-visit.py @@ -178,12 +178,13 @@ out: def gen_visit_enum(name): - # FIXME cast from enum *obj to int * invalidly assumes enum is int return mcgen(''' void visit_type_%(c_name)s(Visitor *v, %(c_name)s *obj, const char *name, Error **errp) { - visit_type_enum(v, (int *)obj, %(c_name)s_lookup, "%(name)s", name, errp); + int tmp = *obj; + visit_type_enum(v, &tmp, %(c_name)s_lookup, "%(name)s", name, errp); + *obj = tmp; } ''', c_name=c_name(name), name=name)