hurd/intr-msg.c

   1 /* Replacement for mach_msg used in interruptible Hurd RPCs.
   2 Copyright (C) 1995 Free Software Foundation, Inc.
   3 This file is part of the GNU C Library.
   4
   5 The GNU C Library is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 License, or (at your option) any later version.
   9
  10 The GNU C Library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 #include <mach.h>
  21 #include <mach/mig_errors.h>
  22 #include <hurd/signal.h>
  23
  24 error_t
  25 _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
  26                          mach_msg_option_t option,
  27                          mach_msg_size_t send_size,
  28                          mach_msg_size_t rcv_size,
  29                          mach_port_t rcv_name,
  30                          mach_msg_timeout_t timeout,
  31                          mach_port_t notify)
  32 {
  33   struct hurd_sigstate *ss = _hurd_self_sigstate ();
  34   error_t err;
  35
  36   /* Tell the signal thread that we are doing an interruptible RPC on
  37      this port.  If we get a signal and should return EINTR, the signal
  38      thread will set this variable to MACH_PORT_NULL.  The RPC might
  39      return EINTR when some other thread gets a signal, in which case we
  40      want to restart our call.  */
  41   ss->intr_port = msg->msgh_remote_port;
  42
  43   /* A signal may arrive here, after intr_port is set, but before
  44      the mach_msg system call.  The signal handler might do an
  45      interruptible RPC, and clobber intr_port; then it would not be
  46      set properly when we actually did send the RPC, and a later
  47      signal wouldn't interrupt that RPC.  So,
  48      _hurd_setup_sighandler saves intr_port in the sigcontext, and
  49      sigreturn restores it.  */
  50
  51  message:
  52
  53   if (ss->cancel)
  54     {
  55       err = EINTR;
  56       ss->cancel = 0;
  57     }
  58   else
  59   /*       err = intr_msg_trap (msg, option, send_size,
  60            rcv_size, rcv_name, timeout, notify);
  61            */
  62     asm (".globl _hurd_intr_rpc_msg_do_trap\n"
  63          ".globl _hurd_intr_rpc_msg_in_trap\n"
  64          "                              movl %%esp, %%ecx\n"
  65          "                              leal %1, %%esp\n"
  66          "                              movl $-25, %%eax\n"
  67          "_hurd_intr_rpc_msg_do_trap:   lcall $7, $0 # status in %0\n"
  68          "_hurd_intr_rpc_msg_in_trap:   movl %%ecx, %%esp"
  69          : "=a" (err) : "m" ((&msg)[1]) : "%ecx");
  70
  71   switch (err)
  72     {
  73     case MACH_SEND_INTERRUPTED: /* RPC didn't get out.  */
  74       if (ss->intr_port != MACH_PORT_NULL)
  75         /* If this signal was for us and it should interrupt calls, the
  76            signal thread will have cleared SS->intr_port.
  77            Since it's not cleared, the signal was for another thread,
  78            or SA_RESTART is set.  Restart the interrupted call.  */
  79         goto message;
  80       /* FALLTHROUGH */
  81
  82     case MACH_RCV_PORT_DIED:
  83       /* Server didn't respond to interrupt_operation,
  84          so the signal thread destroyed the reply port.  */
  85       /* FALLTHROUGH */
  86
  87     case MACH_RCV_TIMED_OUT:
  88       /* The operation was supposedly interrupted, but still has
  89          not returned.  Declare it interrupted.  */
  90
  91       err = EINTR;
  92
  93       /* The EINTR return indicates cancellation, so clear the flag.  */
  94       ss->cancel = 0;
  95       break;
  96
  97     case MACH_RCV_INTERRUPTED:  /* RPC sent; no reply.  */
  98       option &= ~MACH_SEND_MSG; /* Don't send again.  */
  99       if (ss->intr_port == MACH_PORT_NULL)
 100         {
 101           /* This signal or cancellation was for us.  We need to wait for
 102              the reply, but not hang forever.  */
 103           option |= MACH_RCV_TIMEOUT;
 104           timeout = _hurd_interrupted_rpc_timeout;
 105         }
 106       goto message;             /* Retry the receive.  */
 107
 108     case MACH_MSG_SUCCESS:
 109       if (option & MACH_RCV_MSG)
 110         {
 111           /* We got a reply.  Was it EINTR?  */
 112           mig_reply_header_t *const reply = (void *) msg;
 113           const union
 114             {
 115               mach_msg_type_t t;
 116               int i;
 117             } check =
 118               { t: {
 119                 MACH_MSG_TYPE_INTEGER_32,
 120                 32,
 121                 1,
 122                 TRUE,
 123                 FALSE,
 124                 FALSE,
 125                 0
 126               } };
 127           if (msg->msgh_size == sizeof *reply &&
 128               !(msg->msgh_bits & MACH_MSGH_BITS_COMPLEX) &&
 129               *(int *) &reply->RetCodeType == check.i &&
 130               reply->RetCode == EINTR)
 131             {
 132               /* It is indeed EINTR.  Is the interrupt for us?  */
 133               if (ss->intr_port != MACH_PORT_NULL)
 134                 /* Nope; repeat the RPC.
 135                    XXX Resources moved? */
 136                 goto message;
 137               else
 138                 /* The EINTR return indicates cancellation, so clear the
 139                    flag.  */
 140                 ss->cancel = 0;
 141             }
 142         }
 143       break;
 144
 145     default:                    /* Quiet -Wswitch-enum.  */
 146     }
 147
 148   ss->intr_port = MACH_PORT_NULL;
 149
 150   return err;
 151 }