[PATCH v2 7/8] params: use type alignment for kernel parameters

Johan Hovold
2020-11-23T10:25:20Z

Specify type alignment for kernel parameters instead of sizeof(void *).

The alignment attribute is used to prevent gcc from increasing the
alignment of objects with static extent as an optimisation, something
which would mess up the __param array stride.

Using __alignof__(struct kernel_param) rather than sizeof(void *) is
preferred since it better indicates why it is there and doesn't break
should the type size or alignment change.

Note that on m68k the alignment of struct kernel_param is actually two
and that adding a 1- or 2-byte field to the 20-byte struct would cause a
breakage with the current 4-byte alignment.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
include/linux/moduleparam.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 742074ad9f6e..15ecc6cc3a3b 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -288,8 +288,8 @@ struct kparam_array
/* Default value instead of permissions? */ \
static const char __param_str_##name[] = prefix #name; \
static struct kernel_param __moduleparam_const __param_##name \
- __used \
- __section("__param") __attribute__ ((aligned(sizeof(void *)))) \
+ __used __section("__param") \
+ __aligned(__alignof__(struct kernel_param)) \
= { __param_str_##name, THIS_MODULE, ops, \
VERIFY_OCTAL_PERMISSIONS(perm), level, flags, { arg } }

--
2.26.2