usr/src/lib/libc/amd64/gen/makectxt.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1988 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 #pragma weak _makecontext = makecontext
  33
  34 #include "lint.h"
  35 #include <stdarg.h>
  36 #include <ucontext.h>
  37 #include <sys/stack.h>
  38
  39 /*
  40  * The ucontext_t that the user passes in must have been primed with a
  41  * call to getcontext(2), have the uc_stack member set to reflect the
  42  * stack which this context will use, and have the uc_link member set
  43  * to the context which should be resumed when this context returns.
  44  * When makecontext() returns, the ucontext_t will be set to run the
  45  * given function with the given parameters on the stack specified by
  46  * uc_stack, and which will return to the ucontext_t specified by uc_link.
  47  */
  48
  49 static void resumecontext(void);
  50
  51 void
  52 makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
  53 {
  54         long *sp;
  55         long *tsp;
  56         va_list ap;
  57         size_t size;
  58         int pusharg = (argc > 6 ? argc - 6 : 0);
  59         greg_t tmp;
  60         int i;
  61
  62         ucp->uc_mcontext.gregs[REG_PC] = (greg_t)func;
  63
  64         size = sizeof (long) * (pusharg + 1);
  65
  66         /*
  67          * Calculate new value for %rsp. On entry to a function,
  68          * %rsp must be STACK_ENTRY_ALIGNed but not STACK_ALIGNed.
  69          * This is because the pushq %rbp will correct the alignment.
  70          */
  71
  72         sp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp +
  73             ucp->uc_stack.ss_size - size) & ~(STACK_ENTRY_ALIGN - 1));
  74
  75         if (((uintptr_t)sp & (STACK_ALIGN - 1ul)) == 0)
  76                 sp -= STACK_ENTRY_ALIGN / sizeof (*sp);
  77
  78         tsp = sp + 1;
  79
  80         va_start(ap, argc);
  81
  82         for (i = 0; i < argc; i++) {
  83                 tmp = va_arg(ap, long);
  84                 switch (i) {
  85                 case 0:
  86                         ucp->uc_mcontext.gregs[REG_RDI] = tmp;
  87                         break;
  88                 case 1:
  89                         ucp->uc_mcontext.gregs[REG_RSI] = tmp;
  90                         break;
  91                 case 2:
  92                         ucp->uc_mcontext.gregs[REG_RDX] = tmp;
  93                         break;
  94                 case 3:
  95                         ucp->uc_mcontext.gregs[REG_RCX] = tmp;
  96                         break;
  97                 case 4:
  98                         ucp->uc_mcontext.gregs[REG_R8] = tmp;
  99                         break;
 100                 case 5:
 101                         ucp->uc_mcontext.gregs[REG_R9] = tmp;
 102                         break;
 103                 default:
 104                         *tsp++ = tmp;
 105                         break;
 106                 }
 107         }
 108
 109         va_end(ap);
 110
 111         *sp = (long)resumecontext;              /* return address */
 112
 113         ucp->uc_mcontext.gregs[REG_SP] = (greg_t)sp;
 114 }
 115
 116
 117 static void
 118 resumecontext(void)
 119 {
 120         ucontext_t uc;
 121
 122         (void) getcontext(&uc);
 123         (void) setcontext(uc.uc_link);
 124 }