From nobody Sun Feb 8 21:04:12 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=linaro.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1544702723043519.1668569882922; Thu, 13 Dec 2018 04:05:23 -0800 (PST) Received: from localhost ([::1]:51969 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gXPk2-0006yY-1x for importer@patchew.org; Thu, 13 Dec 2018 07:05:22 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59527) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gXPhs-0005lt-O0 for qemu-devel@nongnu.org; Thu, 13 Dec 2018 07:03:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gXPhm-0006tG-Li for qemu-devel@nongnu.org; Thu, 13 Dec 2018 07:03:08 -0500 Received: from orth.archaic.org.uk ([2001:8b0:1d0::2]:53490) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gXPhm-0005Oe-BC; Thu, 13 Dec 2018 07:03:02 -0500 Received: from pm215 by orth.archaic.org.uk with local (Exim 4.89) (envelope-from ) id 1gXPhd-00076r-4R; Thu, 13 Dec 2018 12:02:53 +0000 From: Peter Maydell To: qemu-devel@nongnu.org Date: Thu, 13 Dec 2018 12:02:52 +0000 Message-Id: <20181213120252.21697-1-peter.maydell@linaro.org> X-Mailer: git-send-email 2.19.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2001:8b0:1d0::2 Subject: [Qemu-devel] [PATCH v2] hw/s390/ccw.c: Don't take address of packed members X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Huth , Farhan Ali , David Hildenbrand , Cornelia Huck , Christian Borntraeger , qemu-s390x@nongnu.org, patches@linaro.org, Richard Henderson Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" Taking the address of a field in a packed struct is a bad idea, because it might not be actually aligned enough for that pointer type (and thus cause a crash on dereference on some host architectures). Newer versions of clang warn about this. Avoid the problem by using local copies of the PMCW and SCSW struct fields in copy_schib_from_guest() and copy_schib_to_guest(). Signed-off-by: Peter Maydell Reviewed-by: Farhan Ali Reviewed-by: Thomas Huth --- v1->v2 changes: * add comment about why we're using locals * name locals with underscores, as QEMU's naming conventions recommend hw/s390x/css.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/hw/s390x/css.c b/hw/s390x/css.c index 04ec5cc9705..f92b046cd33 100644 --- a/hw/s390x/css.c +++ b/hw/s390x/css.c @@ -1290,9 +1290,19 @@ void copy_scsw_to_guest(SCSW *dest, const SCSW *src) static void copy_schib_to_guest(SCHIB *dest, const SCHIB *src) { int i; + /* + * We copy the PMCW and SCSW in and out of local variables to + * avoid taking the address of members of a packed struct. + */ + PMCW src_pmcw, dest_pmcw; + SCSW src_scsw, dest_scsw; =20 - copy_pmcw_to_guest(&dest->pmcw, &src->pmcw); - copy_scsw_to_guest(&dest->scsw, &src->scsw); + src_pmcw =3D src->pmcw; + copy_pmcw_to_guest(&dest_pmcw, &src_pmcw); + dest->pmcw =3D dest_pmcw; + src_scsw =3D src->scsw; + copy_scsw_to_guest(&dest_scsw, &src_scsw); + dest->scsw =3D dest_scsw; dest->mba =3D cpu_to_be64(src->mba); for (i =3D 0; i < ARRAY_SIZE(dest->mda); i++) { dest->mda[i] =3D src->mda[i]; @@ -1339,9 +1349,19 @@ static void copy_scsw_from_guest(SCSW *dest, const S= CSW *src) static void copy_schib_from_guest(SCHIB *dest, const SCHIB *src) { int i; + /* + * We copy the PMCW and SCSW in and out of local variables to + * avoid taking the address of members of a packed struct. + */ + PMCW src_pmcw, dest_pmcw; + SCSW src_scsw, dest_scsw; =20 - copy_pmcw_from_guest(&dest->pmcw, &src->pmcw); - copy_scsw_from_guest(&dest->scsw, &src->scsw); + src_pmcw =3D src->pmcw; + copy_pmcw_from_guest(&dest_pmcw, &src_pmcw); + dest->pmcw =3D dest_pmcw; + src_scsw =3D src->scsw; + copy_scsw_from_guest(&dest_scsw, &src_scsw); + dest->scsw =3D dest_scsw; dest->mba =3D be64_to_cpu(src->mba); for (i =3D 0; i < ARRAY_SIZE(dest->mda); i++) { dest->mda[i] =3D src->mda[i]; --=20 2.19.2