Revert "x86/fpu: Use _Alignof to avoid undefined behavior in TYPE_ALIGN"

This reverts commit a00d020f18dbe0666e221d929846f1b591b27c20 which is
commit 55228db2697c09abddcb9487c3d9fa5854a932cd upstream.

_Alignof is not in the gcc version that the 4.19.y kernel still
supports (4.6), so this change needs to be reverted as it breaks the
build on those older compiler versions.

Reported-by: Michael Nies <michael.nies@netclusive.com>
Link: https://lore.kernel.org/r/HE1PR0902MB188277E37DED663AE440510BE1D99@HE1PR0902MB1882.eurprd09.prod.outlook.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217013
Cc: YingChi Long <me@inclyc.cn>
Cc: Borislav Petkov <bp@suse.de>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index a3a570df6be1c30b30dab28337f4e82f1f5fdabf..9692ccc583bb34460f34a0f9c19627a06878d997 100644 (file)
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -138,6 +138,9 @@ static void __init fpu__init_system_generic(void)
 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'.
  *
@@ -145,8 +148,8 @@ 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), _Alignof(TYPE)))
+       BUILD_BUG_ON(sizeof(TYPE) != ALIGN(offsetofend(TYPE, MEMBER), \
+                                          TYPE_ALIGN(TYPE)))
 
 /*
  * We append the 'struct fpu' to the task_struct: