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[qemu-s390x] [PULL 1/2] hw/s390/ccw.c: Don't take address of packed memb
From: |
Cornelia Huck |
Subject: |
[qemu-s390x] [PULL 1/2] hw/s390/ccw.c: Don't take address of packed members |
Date: |
Thu, 20 Dec 2018 17:44:32 +0100 |
From: Peter Maydell <address@hidden>
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 <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Farhan Ali <address@hidden>
Reviewed-by: Thomas Huth <address@hidden>
Signed-off-by: Cornelia Huck <address@hidden>
---
hw/s390x/css.c | 32 ++++++++++++++++++++++++++------
1 file changed, 26 insertions(+), 6 deletions(-)
diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index 04ec5cc970..f92b046cd3 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;
-
- copy_pmcw_to_guest(&dest->pmcw, &src->pmcw);
- copy_scsw_to_guest(&dest->scsw, &src->scsw);
+ /*
+ * 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;
+
+ 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;
-
- copy_pmcw_from_guest(&dest->pmcw, &src->pmcw);
- copy_scsw_from_guest(&dest->scsw, &src->scsw);
+ /*
+ * 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;
+
+ 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];
--
2.17.2