lib/libc/gen/ucontext.c

   1 /*
   2  * Copyright (c) 2007 Matthew T. Emmerton <matt@gsicomp.on.ca>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Neither the name of the author nor the names of its contributors
  11  *    may be used to endorse or promote products derived from this software
  12  *    without specific prior written permission.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  */
  26
  27 #include "namespace.h"
  28 #include <sys/param.h>
  29 #include <sys/signal.h>
  30 #include <sys/ucontext.h>
  31
  32 #include <errno.h>
  33 #include <stdarg.h>
  34 #include <stdlib.h>
  35 #include <unistd.h>
  36 #include <signal.h>
  37 #include "un-namespace.h"
  38
  39 /*
  40  * We need to block most signals during a context switch so we do not
  41  * dispatch a signal vector during a context switch.
  42  */
  43 #if 0
  44 static sigset_t sigset_block_all;
  45
  46 static void __sigset_block_all_setup(void) __attribute__ ((constructor));
  47
  48 static void
  49 __sigset_block_all_setup(void)
  50 {
  51         sigfillset(&sigset_block_all);
  52         sigdelset(&sigset_block_all, SIGSEGV);
  53         sigdelset(&sigset_block_all, SIGBUS);
  54         sigdelset(&sigset_block_all, SIGILL);
  55 }
  56 #endif
  57
  58 /*
  59  * Save the calling context in (oucp) then switch to (ucp).
  60  */
  61 int
  62 _swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
  63 {
  64         int ret;
  65
  66         if (getcontext(oucp) == 0) {
  67                 ret = sigreturn(__DECONST(ucontext_t *, ucp));
  68         } else {
  69                 ret = 0;
  70         }
  71         return(ret);
  72 }
  73
  74 /*
  75  * Switch to the target context, use sigreturn() to properly restore
  76  * everything, including rflags and to avoid scribbling over the
  77  * target stack's red-zone.
  78  *
  79  * Note that setcontext() can be called with a ucontext from a signal,
  80  * so the signal state must be restored and there is really no way to
  81  * avoid making a system call :-(
  82  */
  83 int
  84 _setcontext(const ucontext_t *ucp)
  85 {
  86         int ret;
  87
  88         /* XXX: shouldn't sigreturn() take const? or does it modify ucp? */
  89         ret = sigreturn(__DECONST(ucontext_t *, ucp));
  90
  91         return(ret);
  92 }
  93
  94 __weak_reference(_swapcontext, swapcontext);
  95 __weak_reference(_setcontext, setcontext);