From: YingChi Long me@inclyc.cn
commit 55228db2697c09abddcb9487c3d9fa5854a932cd upstream.
WG14 N2350 specifies that it is an undefined behavior to have type definitions within offsetof", see
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm
This specification is also part of C23.
Therefore, replace the TYPE_ALIGN macro with the _Alignof builtin to avoid undefined behavior. (_Alignof itself is C11 and the kernel is built with -gnu11).
ISO C11 _Alignof is subtly different from the GNU C extension __alignof__. Latter is the preferred alignment and _Alignof the minimal alignment. For long long on x86 these are 8 and 4 respectively.
The macro TYPE_ALIGN's behavior matches _Alignof rather than __alignof__.
[ bp: Massage commit message. ]
Signed-off-by: YingChi Long me@inclyc.cn Signed-off-by: Borislav Petkov bp@suse.de Reviewed-by: Nick Desaulniers ndesaulniers@google.com Link: https://lore.kernel.org/r/20220925153151.2467884-1-me@inclyc.cn Signed-off-by: Nathan Chancellor nathan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/fpu/init.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
--- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -138,9 +138,6 @@ static void __init fpu__init_system_gene unsigned int fpu_kernel_xstate_size; EXPORT_SYMBOL_GPL(fpu_kernel_xstate_size);
-/* Get alignment of the TYPE. */ -#define TYPE_ALIGN(TYPE) offsetof(struct { char x; TYPE test; }, test) - /* * Enforce that 'MEMBER' is the last field of 'TYPE'. * @@ -148,8 +145,8 @@ EXPORT_SYMBOL_GPL(fpu_kernel_xstate_size * because that's how C aligns structs. */ #define CHECK_MEMBER_AT_END_OF(TYPE, MEMBER) \ - BUILD_BUG_ON(sizeof(TYPE) != ALIGN(offsetofend(TYPE, MEMBER), \ - TYPE_ALIGN(TYPE))) + BUILD_BUG_ON(sizeof(TYPE) != \ + ALIGN(offsetofend(TYPE, MEMBER), _Alignof(TYPE)))
/* * We append the 'struct fpu' to the task_struct: