[PATCH 6.18 172/752] virt: vbox: uapi: Mark inner unions in packed structs as packed

Sasha Levin
2026-02-28T17:50:34Z

From: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

[ Upstream commit c25d01e1c4f2d43f47af87c00e223f5ca7c71792 ]

The unpacked unions within a packed struct generates alignment warnings
on clang for 32-bit ARM:

./usr/include/linux/vbox_vmmdev_types.h:239:4: error: field u within 'struct vmmdev_hgcm_function_parameter32'
is less aligned than 'union (unnamed union at ./usr/include/linux/vbox_vmmdev_types.h:223:2)'
and is usually due to 'struct vmmdev_hgcm_function_parameter32' being packed,
which can lead to unaligned accesses [-Werror,-Wunaligned-access]
239 | } u;
| ^

./usr/include/linux/vbox_vmmdev_types.h:254:6: error: field u within
'struct vmmdev_hgcm_function_parameter64::(anonymous union)::(unnamed at ./usr/include/linux/vbox_vmmdev_types.h:249:3)'
is less aligned than 'union (unnamed union at ./usr/include/linux/vbox_vmmdev_types.h:251:4)' and is usually due to
'struct vmmdev_hgcm_function_parameter64::(anonymous union)::(unnamed at ./usr/include/linux/vbox_vmmdev_types.h:249:3)'
being packed, which can lead to unaligned accesses [-Werror,-Wunaligned-access]

With the recent changes to compile-test the UAPI headers in more cases,
these warning in combination with CONFIG_WERROR breaks the build.

Fix the warnings.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512140314.DzDxpIVn-lkp@intel.com/
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/linux-kbuild/20260110-uapi-test-disable-headers-arm-clang-unaligned-access-v1-1-b7b0fa541daa@kernel.org/
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/linux-kbuild/29b2e736-d462-45b7-a0a9-85f8d8a3de56@app.fastmail.com/
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Tested-by: Nicolas Schier <nsc@kernel.org>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/20260115-kbuild-alignment-vbox-v1-2-076aed1623ff@linutronix.de
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/uapi/linux/vbox_vmmdev_types.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/vbox_vmmdev_types.h b/include/uapi/linux/vbox_vmmdev_types.h
index 6073858d52a2e..11f3627c3729b 100644
--- a/include/uapi/linux/vbox_vmmdev_types.h
+++ b/include/uapi/linux/vbox_vmmdev_types.h
@@ -236,7 +236,7 @@ struct vmmdev_hgcm_function_parameter32 {
/** Relative to the request header. */
__u32 offset;
} page_list;
- } u;
+ } __packed u;
} __packed;
VMMDEV_ASSERT_SIZE(vmmdev_hgcm_function_parameter32, 4 + 8);

@@ -251,7 +251,7 @@ struct vmmdev_hgcm_function_parameter64 {
union {
__u64 phys_addr;
__u64 linear_addr;
- } u;
+ } __packed u;
} __packed pointer;
struct {
/** Size of the buffer described by the page list. */
--
2.51.0