From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2AEA0C76190 for ; Thu, 25 Jul 2019 18:00:36 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0795F229F3 for ; Thu, 25 Jul 2019 18:00:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0795F229F3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:34648 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqi2d-0002yM-A2 for qemu-devel@archiver.kernel.org; Thu, 25 Jul 2019 14:00:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:45071) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqi2L-00023S-2Z for qemu-devel@nongnu.org; Thu, 25 Jul 2019 14:00:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hqi2J-00014D-MK for qemu-devel@nongnu.org; Thu, 25 Jul 2019 14:00:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51334) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hqi2G-0000v3-5p; Thu, 25 Jul 2019 14:00:12 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4DA2A81F0F; Thu, 25 Jul 2019 18:00:11 +0000 (UTC) Received: from work-vm (ovpn-117-187.ams2.redhat.com [10.36.117.187]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0E93C4145; Thu, 25 Jul 2019 18:00:09 +0000 (UTC) Date: Thu, 25 Jul 2019 19:00:07 +0100 From: "Dr. David Alan Gilbert" To: Peter Maydell Message-ID: <20190725180007.GN2656@work-vm> References: <20190725163710.11703-1-peter.maydell@linaro.org> <20190725163710.11703-3-peter.maydell@linaro.org> <20190725172712.GM2656@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.0 (2019-05-25) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Thu, 25 Jul 2019 18:00:11 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH for-4.1? 2/2] vmstate.h: Type check VMSTATE_STRUCT_VARRAY macros X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Damien Hedde , qemu-arm , QEMU Developers , Juan Quintela Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Maydell (peter.maydell@linaro.org) wrote: > On Thu, 25 Jul 2019 at 18:27, Dr. David Alan Gilbert > wrote: > > > > * Peter Maydell (peter.maydell@linaro.org) wrote: > > > The VMSTATE_STRUCT_VARRAY_UINT32 macro is intended to handle > > > migrating a field which is an array of structs, but where instead of > > > migrating the entire array we only migrate a variable number of > > > elements of it. > > > > > > The VMSTATE_STRUCT_VARRAY_POINTER_UINT32 macro is intended to handle > > > migrating a field which is of pointer type, and points to a > > > dynamically allocated array of structs of variable size. > > > > > > We weren't actually checking that the field passed to > > > VMSTATE_STRUCT_VARRAY_UINT32 really is an array, with the result that > > > accidentally using it where the _POINTER_ macro was intended would > > > compile but silently corrupt memory on migration. > > > > > > Add type-checking that enforces that the field passed in is > > > really of the right array type. This applies to all the VMSTATE > > > macros which use flags including VMS_VARRAY_* but not VMS_POINTER. > > > > > > Signed-off-by: Peter Maydell > > > > > --- > > > include/migration/vmstate.h | 27 +++++++++++++++++++++------ > > > 1 file changed, 21 insertions(+), 6 deletions(-) > > > > > > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h > > > index ca68584eba4..2df333c3612 100644 > > > --- a/include/migration/vmstate.h > > > +++ b/include/migration/vmstate.h > > > @@ -227,8 +227,19 @@ extern const VMStateInfo vmstate_info_bitmap; > > > extern const VMStateInfo vmstate_info_qtailq; > > > > > > #define type_check_2darray(t1,t2,n,m) ((t1(*)[n][m])0 - (t2*)0) > > > +/* Check that t2 is an array of t1 of size n */ > > > #define type_check_array(t1,t2,n) ((t1(*)[n])0 - (t2*)0) > > > > I'd have to admit I don't understand why that does what you say; > > I'd expected something to index a t2 pointer with [n]. > > Note that this is just a comment describing what the existing > macro does, as a way to distinguish its job from that of the > new macro I'm adding. > > What happens here is that t2 is a type like "foo [32]", ie > it is an array type already. t1 is the base 'foo' type; so the macro > is checking that t1[n] matches t2, where n is passed in to us > and must match the declared array size of the field (32 in > my example). (In C the size of the array is carried around as > part of its type, and must match on both sides of the expression; > so if you pass in the name of an array field that's the wrong size the > type check will fail, which is what we want.) Ah, OK that makes sense; what it really needs is that example to make me realise that t2 was already the array. Dave > > However, for the rest of it, from migration I'm happy: > > > > Reviewed-by: Dr. David Alan Gilbert > > > > given it's just fixing an ARM bug, and given it'll blow up straight away > > I think it's OK for 4.1; the only risk is if we find a compiler we don't > > like. > > thanks > -- PMM -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK