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

@@ -22,10 +22,11 @@
 /*        All Rights Reserved   */
 
 
 /*
  * Copyright 2014 Garrett D'Amore <garrett@damore.org>
+ * Copyright 2023 Oxide Computer Company
  *
  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 

@@ -45,10 +46,11 @@
  * does NOT include sys/regset.h anymore.
  */
 #if !defined(_XPG4_2) || defined(__EXTENSIONS__)
 #include <sys/regset.h>
 #include <sys/siginfo.h>
+#include <sys/int_types.h>
 #endif
 
 #ifdef  __cplusplus
 extern "C" {
 #endif

@@ -61,16 +63,22 @@
 #endif
 #endif
 
 extern int getcontext(ucontext_t *) __RETURNS_TWICE;
 #pragma unknown_control_flow(getcontext)
-extern int setcontext(const ucontext_t *) __NORETURN;
+extern int setcontext(const ucontext_t *);
 extern int swapcontext(ucontext_t *_RESTRICT_KYWD,
                 const ucontext_t *_RESTRICT_KYWD);
 extern void makecontext(ucontext_t *, void(*)(), int, ...);
 
 #if !defined(_XPG4_2) || defined(__EXTENSIONS__)
+extern ucontext_t *ucontext_alloc(uint32_t);
+extern void ucontext_free(ucontext_t *);
+extern int getcontext_extd(ucontext_t *, uint32_t) __RETURNS_TWICE;
+#pragma unknown_control_flow(getcontext_extd)
+extern int swapcontext_extd(ucontext_t *_RESTRICT_KYWD, uint32_t,
+                const ucontext_t *_RESTRICT_KYWD);
 extern int walkcontext(const ucontext_t *, int (*)(uintptr_t, int, void *),
     void *);
 extern int printstack(int);
 extern int addrtosymstr(void *, char *, int);
 extern int getustack(stack_t **);