uuid: Make qemu_uuid_bswap() take and return a QemuUUID

Currently qemu_uuid_bswap() takes a pointer to the QemuUUID to
be byte-swapped. This means it can't be used when the UUID
to be swapped is in a packed member of a struct. It's also
out of line with the general bswap*() functions we provide
in bswap.h, which take the value to be swapped and return it.

Make qemu_uuid_bswap() take a QemuUUID and return the swapped version.

This fixes some clang warnings about taking the address of
a packed struct member in block/vdi.c.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

5 files changed, 17 insertions, 19 deletions

diff --git a/block/vdi.c b/block/vdi.c
index 4cc726047c..0c34f6bae4 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -203,10 +203,10 @@ static void vdi_header_to_cpu(VdiHeader *header)
     header->block_extra = le32_to_cpu(header->block_extra);
     header->blocks_in_image = le32_to_cpu(header->blocks_in_image);
     header->blocks_allocated = le32_to_cpu(header->blocks_allocated);
-    qemu_uuid_bswap(&header->uuid_image);
-    qemu_uuid_bswap(&header->uuid_last_snap);
-    qemu_uuid_bswap(&header->uuid_link);
-    qemu_uuid_bswap(&header->uuid_parent);
+    header->uuid_image = qemu_uuid_bswap(header->uuid_image);
+    header->uuid_last_snap = qemu_uuid_bswap(header->uuid_last_snap);
+    header->uuid_link = qemu_uuid_bswap(header->uuid_link);
+    header->uuid_parent = qemu_uuid_bswap(header->uuid_parent);
 }
 
 static void vdi_header_to_le(VdiHeader *header)
@@ -227,10 +227,10 @@ static void vdi_header_to_le(VdiHeader *header)
     header->block_extra = cpu_to_le32(header->block_extra);
     header->blocks_in_image = cpu_to_le32(header->blocks_in_image);
     header->blocks_allocated = cpu_to_le32(header->blocks_allocated);
-    qemu_uuid_bswap(&header->uuid_image);
-    qemu_uuid_bswap(&header->uuid_last_snap);
-    qemu_uuid_bswap(&header->uuid_link);
-    qemu_uuid_bswap(&header->uuid_parent);
+    header->uuid_image = qemu_uuid_bswap(header->uuid_image);
+    header->uuid_last_snap = qemu_uuid_bswap(header->uuid_last_snap);
+    header->uuid_link = qemu_uuid_bswap(header->uuid_link);
+    header->uuid_parent = qemu_uuid_bswap(header->uuid_parent);
 }
 
 static void vdi_header_print(VdiHeader *header)
diff --git a/hw/acpi/vmgenid.c b/hw/acpi/vmgenid.c
index d78b579a20..02717a8b0d 100644
--- a/hw/acpi/vmgenid.c
+++ b/hw/acpi/vmgenid.c
@@ -30,8 +30,7 @@ void vmgenid_build_acpi(VmGenIdState *vms, GArray *table_data, GArray *guid,
      * first, since that's what the guest expects
      */
     g_array_set_size(guid, VMGENID_FW_CFG_SIZE - ARRAY_SIZE(guid_le.data));
-    guid_le = vms->guid;
-    qemu_uuid_bswap(&guid_le);
+    guid_le = qemu_uuid_bswap(vms->guid);
     /* The GUID is written at a fixed offset into the fw_cfg file
      * in order to implement the "OVMF SDT Header probe suppressor"
      * see docs/specs/vmgenid.txt for more details
@@ -149,8 +148,7 @@ static void vmgenid_update_guest(VmGenIdState *vms)
              * however, will expect the fields to be little-endian.
              * Perform a byte swap immediately before writing.
              */
-            guid_le = vms->guid;
-            qemu_uuid_bswap(&guid_le);
+            guid_le = qemu_uuid_bswap(vms->guid);
             /* The GUID is written at a fixed offset into the fw_cfg file
              * in order to implement the "OVMF SDT Header probe suppressor"
              * see docs/specs/vmgenid.txt for more details.
diff --git a/include/qemu/uuid.h b/include/qemu/uuid.h
index 09489ce5c5..037357d990 100644
--- a/include/qemu/uuid.h
+++ b/include/qemu/uuid.h
@@ -56,6 +56,6 @@ char *qemu_uuid_unparse_strdup(const QemuUUID *uuid);
 
 int qemu_uuid_parse(const char *str, QemuUUID *uuid);
 
-void qemu_uuid_bswap(QemuUUID *uuid);
+QemuUUID qemu_uuid_bswap(QemuUUID uuid);
 
 #endif
diff --git a/tests/vmgenid-test.c b/tests/vmgenid-test.c
index 52cdd83ec0..ae38ee5ac0 100644
--- a/tests/vmgenid-test.c
+++ b/tests/vmgenid-test.c
@@ -88,7 +88,7 @@ static void read_guid_from_memory(QTestState *qts, QemuUUID *guid)
     /* The GUID is in little-endian format in the guest, while QEMU
      * uses big-endian.  Swap after reading.
      */
-    qemu_uuid_bswap(guid);
+    *guid = qemu_uuid_bswap(*guid);
 }
 
 static void read_guid_from_monitor(QTestState *qts, QemuUUID *guid)
diff --git a/util/uuid.c b/util/uuid.c
index ebf06c049a..5787f0978c 100644
--- a/util/uuid.c
+++ b/util/uuid.c
@@ -110,10 +110,10 @@ int qemu_uuid_parse(const char *str, QemuUUID *uuid)
 
 /* Swap from UUID format endian (BE) to the opposite or vice versa.
  */
-void qemu_uuid_bswap(QemuUUID *uuid)
+QemuUUID qemu_uuid_bswap(QemuUUID uuid)
 {
-    assert(QEMU_PTR_IS_ALIGNED(uuid, sizeof(uint32_t)));
-    bswap32s(&uuid->fields.time_low);
-    bswap16s(&uuid->fields.time_mid);
-    bswap16s(&uuid->fields.time_high_and_version);
+    bswap32s(&uuid.fields.time_low);
+    bswap16s(&uuid.fields.time_mid);
+    bswap16s(&uuid.fields.time_high_and_version);
+    return uuid;
 }