src/ucontext/generic/setcontext.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 #define _XOPEN_SOURCE 600L
  25 #include <ucontext.h>
  26 #include <errno.h>
  27 #include <TargetConditionals.h>
  28
  29 #if TARGET_OS_OSX || TARGET_OS_DRIVERKIT
  30
  31 #include <stddef.h>
  32 #include <signal.h>
  33
  34 extern int _setcontext(const void *);
  35
  36 /* This is a macro to capture all the code added in here that is purely to make
  37  * conformance tests pass and seems to have no functional reason nor is it
  38  * required by the standard */
  39 #define CONFORMANCE_SPECIFIC_HACK 1
  40
  41 int
  42 setcontext(const ucontext_t *uctx)
  43 {
  44         if (uctx->uc_mcsize == 0) { /* Invalid context */
  45                 errno = EINVAL;
  46                 return -1;
  47         }
  48
  49         sigprocmask(SIG_SETMASK, &uctx->uc_sigmask, NULL);
  50
  51         mcontext_t mctx = uctx->uc_mcontext;
  52 #if CONFORMANCE_SPECIFIC_HACK
  53         // There is a conformance test which initialized a ucontext A by memcpy-ing
  54         // a ucontext B that was previously initialized with getcontext.
  55         // getcontext(B) modified B such that B.uc_mcontext = &B.__mcontext_data;
  56         // But by doing the memcpy of B to A, A.uc_mcontext = &B.__mcontext_data
  57         // when that's not necessarily what we want. We therefore have to
  58         // unfortunately ignore A.uc_mccontext and use &A.__mcontext_data even though we
  59         // don't know if A.__mcontext_data was properly initialized.  This is really
  60         // because the conformance test doesn't initialize properly with multiple
  61         // getcontexts and instead copies contexts around.
  62         //
  63         //
  64         // Note that this hack, is causing us to fail when restoring a ucontext from
  65         // a signal. See <rdar://problem/63408163> Restoring context from signal
  66         // fails on intel and arm64 platforms
  67         mctx = (mcontext_t) &uctx->__mcontext_data;
  68 #endif
  69
  70 #if defined(__x86_64__) || defined(__arm64__)
  71         return _setcontext(mctx);
  72 #else
  73         return _setcontext(uctx);
  74 #endif
  75 }
  76
  77 #else /* TARGET_OS_OSX  || TARGET_OS_DRIVERKIT */
  78
  79 int
  80 setcontext(const ucontext_t *uctx)
  81 {
  82         errno = ENOTSUP;
  83         return -1;
  84 }
  85
  86 #endif /* TARGET_OS_OSX || TARGET_OS_DRIVERKIT */