From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45961) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gWM4Y-0000dj-F5 for qemu-devel@nongnu.org; Mon, 10 Dec 2018 08:58:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gWM4X-0002fT-1q for qemu-devel@nongnu.org; Mon, 10 Dec 2018 08:58:10 -0500 From: Peter Maydell Date: Mon, 10 Dec 2018 13:58:03 +0000 Message-Id: <20181210135803.20208-1-peter.maydell@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [PATCH] hw/s390/ccw.c: Don't take address of packed members List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: patches@linaro.org, qemu-s390x@nongnu.org, Cornelia Huck , Christian Borntraeger , Richard Henderson , David Hildenbrand , "Dr . David Alan Gilbert" 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 --- This seemed like a not totally ugly and reasonably localised fix that satisfies clang. Oddly, this makes the generated object file 15K smaller (421K vs 406K), so it might even be better code... hw/s390x/css.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/hw/s390x/css.c b/hw/s390x/css.c index 04ec5cc9705..ef07691e36b 100644 --- a/hw/s390x/css.c +++ b/hw/s390x/css.c @@ -1290,9 +1290,15 @@ void copy_scsw_to_guest(SCSW *dest, const SCSW *src) static void copy_schib_to_guest(SCHIB *dest, const SCHIB *src) { int i; + PMCW srcpmcw, destpmcw; + SCSW srcscsw, destscsw; - copy_pmcw_to_guest(&dest->pmcw, &src->pmcw); - copy_scsw_to_guest(&dest->scsw, &src->scsw); + srcpmcw = src->pmcw; + copy_pmcw_to_guest(&destpmcw, &srcpmcw); + dest->pmcw = destpmcw; + srcscsw = src->scsw; + copy_scsw_to_guest(&destscsw, &srcscsw); + dest->scsw = destscsw; dest->mba = cpu_to_be64(src->mba); for (i = 0; i < ARRAY_SIZE(dest->mda); i++) { dest->mda[i] = src->mda[i]; @@ -1339,9 +1345,15 @@ static void copy_scsw_from_guest(SCSW *dest, const SCSW *src) static void copy_schib_from_guest(SCHIB *dest, const SCHIB *src) { int i; + PMCW srcpmcw, destpmcw; + SCSW srcscsw, destscsw; - copy_pmcw_from_guest(&dest->pmcw, &src->pmcw); - copy_scsw_from_guest(&dest->scsw, &src->scsw); + srcpmcw = src->pmcw; + copy_pmcw_from_guest(&destpmcw, &srcpmcw); + dest->pmcw = destpmcw; + srcscsw = src->scsw; + copy_scsw_from_guest(&destscsw, &srcscsw); + dest->scsw = destscsw; dest->mba = be64_to_cpu(src->mba); for (i = 0; i < ARRAY_SIZE(dest->mda); i++) { dest->mda[i] = src->mda[i]; -- 2.19.2