From patchwork Fri Jan 29 13:48:52 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 8163371 Return-Path: X-Original-To: patchwork-qemu-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 8DFADBEEE5 for ; Fri, 29 Jan 2016 13:53:14 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id F059D2038A for ; Fri, 29 Jan 2016 13:53:13 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3D36F20221 for ; Fri, 29 Jan 2016 13:53:13 +0000 (UTC) Received: from localhost ([::1]:34248 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aP9U8-0002Hl-JD for patchwork-qemu-devel@patchwork.kernel.org; Fri, 29 Jan 2016 08:53:12 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41445) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aP9QI-0003aF-L6 for qemu-devel@nongnu.org; Fri, 29 Jan 2016 08:49:15 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aP9QH-0001KP-O2 for qemu-devel@nongnu.org; Fri, 29 Jan 2016 08:49:14 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41739) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aP9QH-0001KF-J8 for qemu-devel@nongnu.org; Fri, 29 Jan 2016 08:49:13 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 344933F3B3; Fri, 29 Jan 2016 13:49:13 +0000 (UTC) Received: from red.redhat.com (ovpn-113-130.phx2.redhat.com [10.3.113.130]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u0TDn5FQ019157; Fri, 29 Jan 2016 08:49:12 -0500 From: Eric Blake To: qemu-devel@nongnu.org Date: Fri, 29 Jan 2016 06:48:52 -0700 Message-Id: <1454075341-13658-17-git-send-email-eblake@redhat.com> In-Reply-To: <1454075341-13658-1-git-send-email-eblake@redhat.com> References: <1454075341-13658-1-git-send-email-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: marcandre.lureau@redhat.com, armbru@redhat.com, Michael Roth Subject: [Qemu-devel] [PATCH v10 16/25] 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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, although 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 using compiler ABI switches 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. But it is still better to avoid the practice entirely, and just use the correct types. This matches the fix for alternate qapi types, done earlier in commit 0426d53 "qapi: Simplify visiting of alternate types", with generated code changing as: | void visit_type_QType(Visitor *v, QType *obj, const char *name, Error **errp) | { |- visit_type_enum(v, (int *)obj, QType_lookup, "QType", name, errp); |+ int value = *obj; |+ visit_type_enum(v, &value, QType_lookup, "QType", name, errp); |+ *obj = value; | } Signed-off-by: Eric Blake Reviewed-by: Marc-André Lureau --- v10: s/tmp/value/, shorter commit message v9: mention earlier commit id, enhance commit message v8: no change 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 f98bb5f..ba75667 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 value = *obj; + visit_type_enum(v, &value, %(c_name)s_lookup, "%(name)s", name, errp); + *obj = value; } ''', c_name=c_name(name), name=name)