src/ucontext/generic/swapcontext.c

   1 /*
   2  * Copyright (c) 2007, 2009 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 /*
  25  * Copyright (c) 2001 Daniel M. Eischen <deischen@freebsd.org>
  26  * All rights reserved.
  27  *
  28  * Redistribution and use in source and binary forms, with or without
  29  * modification, are permitted provided that the following conditions
  30  * are met:
  31  * 1. Redistributions of source code must retain the above copyright
  32  *    notice, this list of conditions and the following disclaimer.
  33  * 2. Neither the name of the author nor the names of its contributors
  34  *    may be used to endorse or promote products derived from this software
  35  *    without specific prior written permission.
  36  *
  37  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  38  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  39  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  40  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  41  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  42  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  43  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  44  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  45  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  46  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  47  * SUCH DAMAGE.
  48  */
  49
  50 #define _XOPEN_SOURCE 600L
  51 #include <ucontext.h>
  52 #include <errno.h>
  53 #include <TargetConditionals.h>
  54
  55 /* This is a macro to capture all the code added in here that is purely to make
  56  * conformance tests pass and seems to have no functional reason nor is it
  57  * required by the standard */
  58 #define CONFORMANCE_SPECIFIC_HACK 1
  59
  60 #if TARGET_OS_OSX || TARGET_OS_DRIVERKIT
  61
  62 #pragma clang diagnostic ignored "-Wdeprecated-declarations"
  63
  64 #include <sys/param.h>
  65 #include <sys/signal.h>
  66 #include <stddef.h>
  67
  68 #define uc_flags uc_onstack
  69 #define UCF_SWAPPED 0x80000000
  70
  71 int
  72 swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
  73 {
  74         int ret;
  75         if ((oucp == NULL) || (ucp == NULL)) {
  76                 errno = EINVAL;
  77                 return -1;
  78         }
  79
  80         oucp->uc_flags &= ~UCF_SWAPPED;
  81
  82 #if CONFORMANCE_SPECIFIC_HACK
  83         // getcontext overwrites uc_link so we save it and restore it
  84         ucontext_t *next_context = oucp->uc_link;
  85         ret = getcontext(oucp);
  86         oucp->uc_link = next_context;
  87 #endif
  88
  89         if ((ret == 0) && !(oucp->uc_flags & UCF_SWAPPED)) {
  90                 oucp->uc_flags |= UCF_SWAPPED;
  91                 /* In the future, when someone calls setcontext(oucp), that will return
  92                  * us to the getcontext call above with ret = 0. However, because we
  93                  * just flipped the UCF_SWAPPED bit, we will not call setcontext again
  94                  * and will return. */
  95                 ret = setcontext(ucp);
  96         }
  97
  98         asm(""); // Prevent tailcall <rdar://problem/12581792>
  99         return (ret);
 100 }
 101
 102 #else /* TARGET_OS_OSX || TARGET_OS_DRIVERKIT */
 103
 104 int
 105 swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
 106 {
 107         errno = ENOTSUP;
 108         return -1;
 109 }
 110
 111 #endif /* TARGET_OS_OSX || TARGET_OS_DRIVERKIT */