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 <peter.mayd...@linaro.org>
---
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;
- copy_pmcw_to_guest(&dest->pmcw, &src->pmcw);
- copy_scsw_to_guest(&dest->scsw, &src->scsw);
+ src_pmcw = src->pmcw;
+ copy_pmcw_to_guest(&dest_pmcw, &src_pmcw);
+ dest->pmcw = dest_pmcw;
+ src_scsw = src->scsw;
+ copy_scsw_to_guest(&dest_scsw, &src_scsw);
+ dest->scsw = dest_scsw;
dest->mba = cpu_to_be64(src->mba);
for (i = 0; i < ARRAY_SIZE(dest->mda); i++) {
dest->mda[i] = src->mda[i];
@@ -1339,9 +1349,19 @@ static void copy_scsw_from_guest(SCSW *dest, const SCSW
*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;
- copy_pmcw_from_guest(&dest->pmcw, &src->pmcw);
- copy_scsw_from_guest(&dest->scsw, &src->scsw);
+ src_pmcw = src->pmcw;
+ copy_pmcw_from_guest(&dest_pmcw, &src_pmcw);
+ dest->pmcw = dest_pmcw;
+ src_scsw = src->scsw;
+ copy_scsw_from_guest(&dest_scsw, &src_scsw);
+ dest->scsw = dest_scsw;
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
