15254 %ymm registers not restored after signal handler
15367 x86 getfpregs() summons corrupting %xmm ghosts
15333 want x86 /proc xregs support (libc_db, libproc, mdb, etc.)
15336 want libc functions for extended ucontext_t
15334 want ps_lwphandle-specific reg routines
15328 FPU_CW_INIT mistreats reserved bit
15335 i86pc fpu_subr.c isn't really platform-specific
15332 setcontext(2) isn't actually noreturn
15331 need <sys/stdalign.h>
Change-Id: I7060aa86042dfb989f77fc3323c065ea2eafa9ad
Conflicts:
    usr/src/uts/common/fs/proc/prcontrol.c
    usr/src/uts/intel/os/archdep.c
    usr/src/uts/intel/sys/ucontext.h
    usr/src/uts/intel/syscall/getcontext.c

@@ -8,48 +8,14 @@
  * source.  A copy of the CDDL is also available via the Internet at
  * http://www.illumos.org/license/CDDL.
  */
 
 /*
- * Copyright 2016 Joyent, Inc.
- * Copyright 2022 Oxide Computer Company
+ * Copyright 2023 Oxide Computer Company
  */
 
 #ifndef _STDALIGN_H
 #define _STDALIGN_H
 
-/*
- * ISO/IEC C11 stdalign.h. This header is meant to provide definitions for the
- * alignas and alignof 'keywords' into the underlying compiler-understood value.
- * In addition, there are two macros that are meant to define that this process
- * has happened. C++11 added alignas/alignof as keywords and including this
- * header is meant to cause us to still have the _is_defined macros, but not
- * define this overall.
- *
- * Unlike other cases we don't use any symbol guards here (other than C++) and
- * just allow the implementation to either have _Alignas and _Alignof or not
- * have it and lead to a compiler error for the user. The main justification of
- * this is that this header is only defined in C11 (and newer). It's not defined
- * in other standards and just as if you include a non-standard header, in this
- * case we don't try to stop that (same as if you included something like
- * libdevinfo.h).
- */
+#include <sys/stdalign.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#ifndef __cplusplus
-
-#define alignas _Alignas
-#define alignof _Alignof
-
-#endif  /* !__cplusplus */
-
-#define __alignas_is_defined    1
-#define __alignof_is_defined    1
-
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* _STDALIGN_H */