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

   1 /*      $NetBSD: makecontext.c,v 1.7 2011/09/20 08:42:29 joerg Exp $    */
   2
   3 /*-
   4  * Copyright (c) 2001 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
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 __RCSID("$NetBSD: makecontext.c,v 1.7 2011/09/20 08:42:29 joerg Exp $");
  35 #endif
  36
  37 #include <inttypes.h>
  38 #include <stddef.h>
  39 #include <ucontext.h>
  40 #include "extern.h"
  41
  42 #include <stdarg.h>
  43
  44 void __resumecontext(void) __dead;
  45
  46 void
  47 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
  48 {
  49         __greg_t *gr = ucp->uc_mcontext.__gregs;
  50         __greg_t *sp;
  51         int i;
  52         va_list ap;
  53
  54         /* LINTED uintptr_t is safe */
  55         sp  = (__greg_t *)
  56             ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
  57         /* LINTED uintptr_t is safe */
  58 #if defined(__mips_o32) || defined(__mips_o64)
  59         sp -= (argc >= 4 ? argc : 4);   /* Make room for >=4 arguments. */
  60         sp  = (__greg_t *)
  61               ((uintptr_t)sp & ~0x7);   /* Align on double-word boundary. */
  62 #elif defined(__mips_n32) || defined(__mips_n64)
  63         sp -= (argc > 8 ? argc - 8 : 0); /* Make room for > 8 arguments. */
  64         sp  = (__greg_t *)
  65               ((uintptr_t)sp & ~0xf);   /* Align on quad-word boundary. */
  66 #endif
  67
  68         gr[_REG_SP]  = (intptr_t)sp;
  69         gr[_REG_RA]  = (intptr_t)__resumecontext;
  70         gr[_REG_T9]  = (intptr_t)func;          /* required for .abicalls */
  71         gr[_REG_EPC] = (intptr_t)func;
  72
  73         /* Construct argument list. */
  74         va_start(ap, argc);
  75 #if defined(__mips_o32) || defined(__mips_o64)
  76         /* Up to the first four arguments are passed in $a0-3. */
  77         for (i = 0; i < argc && i < 4; i++)
  78                 /* LINTED __greg_t is safe */
  79                 gr[_REG_A0 + i] = va_arg(ap, __greg_t);
  80         /* Pass remaining arguments on the stack above the $a0-3 gap. */
  81         sp += i;
  82 #endif
  83 #if defined(__mips_n32) || defined(__mips_n64)
  84         /* Up to the first 8 arguments are passed in $a0-7. */
  85         for (i = 0; i < argc && i < 8; i++)
  86                 /* LINTED __greg_t is safe */
  87                 gr[_REG_A0 + i] = va_arg(ap, __greg_t);
  88         /* Pass remaining arguments on the stack above the $a0-3 gap. */
  89 #endif
  90         /* Pass remaining arguments on the stack above the $a0-3 gap. */
  91         for (; i < argc; i++)
  92                 /* LINTED uintptr_t is safe */
  93                 *sp++ = va_arg(ap, __greg_t);
  94         va_end(ap);
  95 }