lib/libc/arch/x86_64/gen/makecontext.c

   1 /*      $NetBSD: makecontext.c,v 1.4 2009/07/30 20:57:17 dsl Exp $      */
   2
   3 /*-
   4  * Copyright (c) 1999 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Klaus Klein.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  *
  31  * Modified from the i386 version for x86_64 by fvdl@wasabisystems.com.
  32  *
  33  */
  34
  35 #include <sys/cdefs.h>
  36 #if defined(LIBC_SCCS) && !defined(lint)
  37 __RCSID("$NetBSD: makecontext.c,v 1.4 2009/07/30 20:57:17 dsl Exp $");
  38 #endif
  39
  40 #include <inttypes.h>
  41 #include <stddef.h>
  42 #include <ucontext.h>
  43 #include "extern.h"
  44
  45 #include <stdarg.h>
  46
  47 void
  48 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
  49 {
  50         __greg_t *gr = ucp->uc_mcontext.__gregs;
  51         uintptr_t *sp;
  52         va_list ap;
  53         int stackargs, i;
  54
  55         stackargs = argc - 6;
  56
  57         /* LINTED __greg_t is safe */
  58         gr[_REG_RIP] = (__greg_t)func;
  59
  60         /* LINTED uintptr_t is safe */
  61         sp  = (uintptr_t *)
  62             ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
  63
  64         /* LINTED uintptr_t is safe */
  65         sp  = (uintptr_t *)(((uintptr_t)sp & ~15));
  66         sp--;
  67         if (stackargs > 0)
  68                 sp -= stackargs;
  69         /* LINTED __greg_t is safe */
  70         gr[_REG_RSP] = (__greg_t)sp;
  71         gr[_REG_RBP] = (__greg_t)0;     /* Wipe out frame pointer. */
  72
  73         /* Put return address on top of stack. */
  74         /* LINTED uintptr_t is safe */
  75         *sp++ = (uintptr_t)_resumecontext;
  76
  77         /*
  78          * Construct argument list.
  79          * The registers used to pass the first 6 arguments
  80          * (rdi, rsi, rdx, rcx, r8, r9) are the first 6 in gregs,
  81          * in that order, so those arguments can just be copied to
  82          * the gregs array.
  83          */
  84         va_start(ap, argc);
  85         for (i = 0; i < 6 && argc > 0; i++) {
  86                 argc--;
  87                 /* LINTED __greg_t is safe */
  88                 gr[i] = va_arg(ap, __greg_t);
  89         }
  90
  91         while (stackargs-- > 0) {
  92                 /* LINTED uintptr_t is safe */
  93                 *sp++ = va_arg(ap, uintptr_t);
  94         }
  95
  96         va_end(ap);
  97 }