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| author | YingChi Long <me@inclyc.cn> | 2022-11-18 08:55:35 +0800 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2022-11-22 17:13:03 +0100 |
| commit | 55228db2697c09abddcb9487c3d9fa5854a932cd (patch) | |
| tree | f2ecca183f3ea77f6863389458636c9068841be0 /arch/x86/kernel/fpu | |
| parent | 6ea25770b043c7997ab21d1ce95ba5de4d3d85d9 (diff) | |
x86/fpu: Use _Alignof to avoid undefined behavior in TYPE_ALIGN
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
Diffstat (limited to 'arch/x86/kernel/fpu')
| -rw-r--r-- | arch/x86/kernel/fpu/init.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c index 8946f89761cc..851eb13edc01 100644 --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -133,9 +133,6 @@ static void __init fpu__init_system_generic(void) fpu__init_system_mxcsr(); } -/* 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'. * @@ -143,8 +140,8 @@ static void __init fpu__init_system_generic(void) * 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: |