sysdeps/mach/hurd/i386/sigreturn.c

   1 /* Copyright (C) 1991-2014 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 register int *sp asm ("%esp");
  19
  20 #include <hurd.h>
  21 #include <hurd/signal.h>
  22 #include <hurd/threadvar.h>
  23 #include <hurd/msg.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26
  27 int
  28 __sigreturn (struct sigcontext *scp)
  29 {
  30   struct hurd_sigstate *ss;
  31   struct hurd_userlink *link = (void *) &scp[1];
  32   mach_port_t *reply_port;
  33
  34   if (scp == NULL || (scp->sc_mask & _SIG_CANT_MASK))
  35     {
  36       errno = EINVAL;
  37       return -1;
  38     }
  39
  40   ss = _hurd_self_sigstate ();
  41   __spin_lock (&ss->lock);
  42
  43   /* Remove the link on the `active resources' chain added by
  44      _hurd_setup_sighandler.  Its purpose was to make sure
  45      that we got called; now we have, it is done.  */
  46   _hurd_userlink_unlink (link);
  47
  48   /* Restore the set of blocked signals, and the intr_port slot.  */
  49   ss->blocked = scp->sc_mask;
  50   ss->intr_port = scp->sc_intr_port;
  51
  52   /* Check for pending signals that were blocked by the old set.  */
  53   if (ss->pending & ~ss->blocked)
  54     {
  55       /* There are pending signals that just became unblocked.  Wake up the
  56          signal thread to deliver them.  But first, squirrel away SCP where
  57          the signal thread will notice it if it runs another handler, and
  58          arrange to have us called over again in the new reality.  */
  59       ss->context = scp;
  60       __spin_unlock (&ss->lock);
  61       __msg_sig_post (_hurd_msgport, 0, 0, __mach_task_self ());
  62       /* If a pending signal was handled, sig_post never returned.
  63          If it did return, the pending signal didn't run a handler;
  64          proceed as usual.  */
  65       __spin_lock (&ss->lock);
  66       ss->context = NULL;
  67     }
  68
  69   if (scp->sc_onstack)
  70     {
  71       ss->sigaltstack.ss_flags &= ~SS_ONSTACK; /* XXX threadvars */
  72       /* XXX cannot unlock until off sigstack */
  73       abort ();
  74     }
  75   else
  76     __spin_unlock (&ss->lock);
  77
  78   /* Destroy the MiG reply port used by the signal handler, and restore the
  79      reply port in use by the thread when interrupted.  */
  80   reply_port =
  81     (mach_port_t *) __hurd_threadvar_location (_HURD_THREADVAR_MIG_REPLY);
  82   if (*reply_port)
  83     {
  84       mach_port_t port = *reply_port;
  85
  86       /* Assigning MACH_PORT_DEAD here tells libc's mig_get_reply_port not to
  87          get another reply port, but avoids mig_dealloc_reply_port trying to
  88          deallocate it after the receive fails (which it will, because the
  89          reply port will be bogus, whether we do this or not).  */
  90       *reply_port = MACH_PORT_DEAD;
  91
  92       __mach_port_destroy (__mach_task_self (), port);
  93     }
  94   *reply_port = scp->sc_reply_port;
  95
  96   if (scp->sc_fpused)
  97     /* Restore the FPU state.  Mach conveniently stores the state
  98        in the format the i387 `frstor' instruction uses to restore it.  */
  99     asm volatile ("frstor %0" : : "m" (scp->sc_fpsave));
 100
 101   {
 102     /* There are convenient instructions to pop state off the stack, so we
 103        copy the registers onto the user's stack, switch there, pop and
 104        return.  */
 105
 106     int *usp = (int *) scp->sc_uesp;
 107
 108     *--usp = scp->sc_eip;
 109     *--usp = scp->sc_efl;
 110     memcpy (usp -= 12, &scp->sc_i386_thread_state, 12 * sizeof (int));
 111
 112     sp = usp;
 113
 114 #define A(line) asm volatile (#line)
 115     /* The members in the sigcontext are arranged in this order
 116        so we can pop them easily.  */
 117
 118     /* Pop the segment registers (except %cs and %ss, done last).  */
 119     A (popl %gs);
 120     A (popl %fs);
 121     A (popl %es);
 122     A (popl %ds);
 123     /* Pop the general registers.  */
 124     A (popa);
 125     /* Pop the processor flags.  */
 126     A (popf);
 127     /* Return to the saved PC.  */
 128     A (ret);
 129
 130     /* Firewall.  */
 131     A (hlt);
 132 #undef A
 133   }
 134
 135   /* NOTREACHED */
 136   return -1;
 137 }
 138
 139 weak_alias (__sigreturn, sigreturn)