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

@@ -26,11 +26,11 @@
  * Portions Copyright 2007 Chad Mynhier
  * Copyright 2012 DEY Storage Systems, Inc.  All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright 2015, Joyent, Inc.
  * Copyright 2020 OmniOS Community Edition (OmniOSce) Association.
- * Copyright 2021 Oxide Computer Company
+ * Copyright 2023 Oxide Computer Company
  */
 
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>

@@ -3153,11 +3153,11 @@
  * Find an entry in the process hash table for the specified lwpid.
  * The entry will either point to an existing struct ps_lwphandle
  * or it will point to an empty slot for a new struct ps_lwphandle.
  */
 static struct ps_lwphandle **
-Lfind(struct ps_prochandle *P, lwpid_t lwpid)
+Lfind_slot(struct ps_prochandle *P, lwpid_t lwpid)
 {
         struct ps_lwphandle **Lp;
         struct ps_lwphandle *L;
 
         for (Lp = &P->hashtab[lwpid % (HASHSIZE - 1)];

@@ -3166,10 +3166,24 @@
                         break;
         return (Lp);
 }
 
 /*
+ * A wrapper around Lfind_slot() that is suitable for the rest of the internal
+ * consumers who don't care about a slot, merely existence.
+ */
+struct ps_lwphandle *
+Lfind(struct ps_prochandle *P, lwpid_t lwpid)
+{
+        if (P->hashtab == NULL) {
+                return (NULL);
+        }
+
+        return (*Lfind_slot(P, lwpid));
+}
+
+/*
  * Grab an LWP contained within the controlled process.
  * Return an opaque pointer to its LWP control structure.
  *      perr: pointer to error return code.
  */
 struct ps_lwphandle *

@@ -3188,11 +3202,11 @@
                 rc = G_NOPROC;
         else if (P->hashtab == NULL &&
             (P->hashtab = calloc(HASHSIZE, sizeof (struct ps_lwphandle *)))
             == NULL)
                 rc = G_STRANGE;
-        else if (*(Lp = Lfind(P, lwpid)) != NULL)
+        else if (*(Lp = Lfind_slot(P, lwpid)) != NULL)
                 rc = G_BUSY;
         else if ((L = malloc(sizeof (struct ps_lwphandle))) == NULL)
                 rc = G_STRANGE;
         if (rc) {
                 *perr = rc;

@@ -3330,11 +3344,11 @@
 }
 
 static void
 Lfree_internal(struct ps_prochandle *P, struct ps_lwphandle *L)
 {
-        *Lfind(P, L->lwp_id) = L->lwp_hash;     /* delete from hash table */
+        *Lfind_slot(P, L->lwp_id) = L->lwp_hash; /* delete from hash table */
         if (L->lwp_ctlfd >= 0)
                 (void) close(L->lwp_ctlfd);
         if (L->lwp_statfd >= 0)
                 (void) close(L->lwp_statfd);
 

@@ -3436,11 +3450,11 @@
 /*
  * Wait for the specified LWP to stop or terminate.
  * Or, just get the current status (PCNULL).
  * Or, direct it to stop and get the current status (PCDSTOP).
  */
-static int
+int
 Lstopstatus(struct ps_lwphandle *L,
     long request,               /* PCNULL, PCDSTOP, PCSTOP, PCWSTOP */
     uint_t msec)                /* if non-zero, timeout in milliseconds */
 {
         int ctlfd = L->lwp_ctlfd;