hurd/intr-msg.c

   1 /* Replacement for mach_msg used in interruptible Hurd RPCs.
   2    Copyright (C) 95,96,97,98,99,2000 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 not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <mach.h>
  21 #include <mach/mig_errors.h>
  22 #include <mach/mig_support.h>
  23 #include <hurd/signal.h>
  24 #include <assert.h>
  25
  26 #include "intr-msg.h"
  27
  28
  29 error_t
  30 _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
  31                          mach_msg_option_t option,
  32                          mach_msg_size_t send_size,
  33                          mach_msg_size_t rcv_size,
  34                          mach_port_t rcv_name,
  35                          mach_msg_timeout_t timeout,
  36                          mach_port_t notify)
  37 {
  38   error_t err;
  39   struct hurd_sigstate *ss;
  40   const mach_msg_option_t user_option = option;
  41   const mach_msg_timeout_t user_timeout = timeout;
  42
  43   struct clobber { int i[2]; };
  44   union msg
  45   {
  46     mach_msg_header_t header;
  47     mig_reply_header_t reply;
  48     struct
  49     {
  50       mach_msg_header_t header;
  51       int type;
  52       int code;
  53     } check;
  54     struct
  55     {
  56       mach_msg_header_t header;
  57       struct clobber data;
  58     } request;
  59   };
  60   union msg *const m = (void *) msg;
  61   mach_msg_bits_t msgh_bits;
  62   mach_port_t remote_port;
  63   mach_msg_id_t msgid;
  64   struct clobber save_data;
  65
  66   if ((option & (MACH_SEND_MSG|MACH_RCV_MSG)) != (MACH_SEND_MSG|MACH_RCV_MSG)
  67       || _hurd_msgport_thread == MACH_PORT_NULL)
  68     {
  69       /* Either this is not an RPC (i.e., only a send or only a receive),
  70          so it can't be interruptible; or, the signal thread is not set up
  71          yet, so we cannot do the normal signal magic.  Do a normal,
  72          uninterruptible mach_msg call instead.  */
  73       return __mach_msg (&m->header, option, send_size, rcv_size, rcv_name,
  74                          timeout, notify);
  75     }
  76
  77   ss = _hurd_self_sigstate ();
  78
  79   /* Save state that gets clobbered by an EINTR reply message.
  80      We will need to restore it if we want to retry the RPC.  */
  81   msgh_bits = m->header.msgh_bits;
  82   remote_port = m->header.msgh_remote_port;
  83   msgid = m->header.msgh_id;
  84   assert (rcv_size >= sizeof m->request);
  85   save_data = m->request.data;
  86
  87   /* Tell the signal thread that we are doing an interruptible RPC on
  88      this port.  If we get a signal and should return EINTR, the signal
  89      thread will set this variable to MACH_PORT_NULL.  The RPC might
  90      return EINTR when some other thread gets a signal, in which case we
  91      want to restart our call.  */
  92   ss->intr_port = m->header.msgh_remote_port;
  93
  94   /* A signal may arrive here, after intr_port is set, but before the
  95      mach_msg system call.  The signal handler might do an interruptible
  96      RPC, and clobber intr_port; then it would not be set properly when we
  97      actually did send the RPC, and a later signal wouldn't interrupt that
  98      RPC.  So, _hurd_setup_sighandler saves intr_port in the sigcontext,
  99      and sigreturn restores it.  */
 100
 101  message:
 102
 103   /* XXX
 104      At all points here (once SS->intr_port is set), the signal thread
 105      thinks we are "about to enter the syscall", and might mutate our
 106      return-value register.  This is bogus.
 107    */
 108
 109   if (ss->cancel)
 110     {
 111       /* We have been cancelled.  Don't do an RPC at all.  */
 112       ss->intr_port = MACH_PORT_NULL;
 113       ss->cancel = 0;
 114       return EINTR;
 115     }
 116
 117   /* Note that the signal trampoline code might modify our OPTION!  */
 118   err = INTR_MSG_TRAP (msg, option, send_size,
 119                        rcv_size, rcv_name, timeout, notify);
 120
 121   switch (err)
 122     {
 123     case MACH_RCV_TIMED_OUT:
 124       if (user_option & MACH_RCV_TIMEOUT)
 125         /* The real user RPC timed out.  */
 126         break;
 127       else
 128         /* The operation was supposedly interrupted, but still has
 129            not returned.  Declare it interrupted.  */
 130         goto interrupted;
 131
 132     case MACH_SEND_INTERRUPTED: /* RPC didn't get out.  */
 133       if (!(option & MACH_SEND_MSG))
 134         {
 135           /* Oh yes, it did!  Since we were not doing a message send,
 136              this return code cannot have come from the kernel!
 137              Instead, it was the signal thread mutating our state to tell
 138              us not to enter this RPC.  However, we are already in the receive!
 139              Since the signal thread thought we weren't in the RPC yet,
 140              it didn't do an interrupt_operation.
 141              XXX */
 142           goto retry_receive;
 143         }
 144       /* FALLTHROUGH */
 145
 146       /* These are the other codes that mean a pseudo-receive modified
 147          the message buffer and we might need to clean up the port rights.  */
 148     case MACH_SEND_TIMED_OUT:
 149     case MACH_SEND_INVALID_NOTIFY:
 150     case MACH_SEND_NO_NOTIFY:
 151     case MACH_SEND_NOTIFY_IN_PROGRESS:
 152       if (MACH_MSGH_BITS_REMOTE (msg->msgh_bits) == MACH_MSG_TYPE_MOVE_SEND)
 153         {
 154           __mach_port_deallocate (__mach_task_self (), msg->msgh_remote_port);
 155           msg->msgh_bits
 156             = (MACH_MSGH_BITS (MACH_MSG_TYPE_COPY_SEND,
 157                                MACH_MSGH_BITS_LOCAL (msg->msgh_bits))
 158                | MACH_MSGH_BITS_OTHER (msg->msgh_bits));
 159         }
 160       if (msg->msgh_bits & MACH_MSGH_BITS_COMPLEX)
 161         {
 162           /* Check for MOVE_SEND rights in the message.  These hold refs
 163              that we need to release in case the message is in fact never
 164              re-sent later.  Since it might in fact be re-sent, we turn
 165              these into COPY_SEND's after deallocating the extra user ref;
 166              the caller is responsible for still holding a ref to go with
 167              the original COPY_SEND right, so the resend copies it again.  */
 168
 169           mach_msg_type_long_t *ty = (void *) (msg + 1);
 170           while ((void *) ty < (void *) msg + msg->msgh_size)
 171             {
 172               mach_msg_type_name_t name;
 173               mach_msg_type_size_t size;
 174               mach_msg_type_number_t number;
 175
 176               inline void clean_ports (mach_port_t *ports, int dealloc)
 177                 {
 178                   mach_msg_type_number_t i;
 179                   switch (name)
 180                     {
 181                     case MACH_MSG_TYPE_MOVE_SEND:
 182                       for (i = 0; i < number; i++)
 183                         __mach_port_deallocate (__mach_task_self (), *ports++);
 184                       (ty->msgtl_header.msgt_longform
 185                        ? ty->msgtl_name : ty->msgtl_header.msgt_name)
 186                         = MACH_MSG_TYPE_COPY_SEND;
 187                       break;
 188                     case MACH_MSG_TYPE_COPY_SEND:
 189                     case MACH_MSG_TYPE_MOVE_RECEIVE:
 190                       break;
 191                     default:
 192                       if (MACH_MSG_TYPE_PORT_ANY (name))
 193                         assert (! "unexpected port type in interruptible RPC");
 194                     }
 195                   if (dealloc)
 196                     __vm_deallocate (__mach_task_self (),
 197                                      (vm_address_t) ports,
 198                                      number * sizeof (mach_port_t));
 199                 }
 200
 201               if (ty->msgtl_header.msgt_longform)
 202                 {
 203                   name = ty->msgtl_name;
 204                   size = ty->msgtl_size;
 205                   number = ty->msgtl_number;
 206                   (char *) ty += sizeof (mach_msg_type_long_t);
 207                 }
 208               else
 209                 {
 210                   name = ty->msgtl_header.msgt_name;
 211                   size = ty->msgtl_header.msgt_size;
 212                   number = ty->msgtl_header.msgt_number;
 213                   (char *) ty += sizeof (mach_msg_type_t);
 214                 }
 215
 216               if (ty->msgtl_header.msgt_inline)
 217                 {
 218                   clean_ports ((void *) ty, 0);
 219                   /* calculate length of data in bytes, rounding up */
 220                   (char *) ty += (((((number * size) + 7) >> 3)
 221                                    + sizeof (mach_msg_type_t) - 1)
 222                                   &~ (sizeof (mach_msg_type_t) - 1));
 223                 }
 224               else
 225                 clean_ports (*((void **) ty)++,
 226                              ty->msgtl_header.msgt_deallocate);
 227             }
 228         }
 229       break;
 230
 231     case EINTR:
 232       /* Either the process was stopped and continued,
 233          or the server doesn't support interrupt_operation.  */
 234       if (ss->intr_port != MACH_PORT_NULL)
 235         /* If this signal was for us and it should interrupt calls, the
 236            signal thread will have cleared SS->intr_port.
 237            Since it's not cleared, the signal was for another thread,
 238            or SA_RESTART is set.  Restart the interrupted call.  */
 239         {
 240           /* Make sure we have a valid reply port.  The one we were using
 241              may have been destroyed by interruption.  */
 242           m->header.msgh_local_port = rcv_name = __mig_get_reply_port ();
 243           m->header.msgh_bits = msgh_bits;
 244           option = user_option;
 245           timeout = user_timeout;
 246           goto message;
 247         }
 248       /* FALLTHROUGH */
 249
 250     case MACH_RCV_PORT_DIED:
 251       /* Server didn't respond to interrupt_operation,
 252          so the signal thread destroyed the reply port.  */
 253       /* FALLTHROUGH */
 254
 255     interrupted:
 256       err = EINTR;
 257
 258       /* The EINTR return indicates cancellation, so clear the flag.  */
 259       ss->cancel = 0;
 260       break;
 261
 262     case MACH_RCV_INTERRUPTED:  /* RPC sent; no reply.  */
 263       option &= ~MACH_SEND_MSG; /* Don't send again.  */
 264     retry_receive:
 265       if (ss->intr_port == MACH_PORT_NULL)
 266         {
 267           /* This signal or cancellation was for us.  We need to wait for
 268              the reply, but not hang forever.  */
 269           option |= MACH_RCV_TIMEOUT;
 270           /* Never decrease the user's timeout.  */
 271           if (!(user_option & MACH_RCV_TIMEOUT)
 272               || timeout > _hurd_interrupted_rpc_timeout)
 273             timeout = _hurd_interrupted_rpc_timeout;
 274         }
 275       else
 276         {
 277           option = user_option;
 278           timeout = user_timeout;
 279         }
 280       goto message;             /* Retry the receive.  */
 281
 282     case MACH_MSG_SUCCESS:
 283       {
 284         /* We got a reply.  Was it EINTR?  */
 285         const union
 286         {
 287           mach_msg_type_t t;
 288           int i;
 289         } check =
 290           { t: { MACH_MSG_TYPE_INTEGER_T, sizeof (integer_t) * 8,
 291                  1, TRUE, FALSE, FALSE, 0 } };
 292
 293         if (m->reply.RetCode == EINTR &&
 294             m->header.msgh_size == sizeof m->reply &&
 295             m->check.type == check.i &&
 296             !(m->header.msgh_bits & MACH_MSGH_BITS_COMPLEX))
 297           {
 298             /* It is indeed EINTR.  Is the interrupt for us?  */
 299             if (ss->intr_port != MACH_PORT_NULL)
 300               {
 301                 /* Nope; repeat the RPC.
 302                    XXX Resources moved? */
 303
 304                 assert (m->header.msgh_id == msgid + 100);
 305
 306                 /* We know we have a valid reply port, because we just
 307                    received the EINTR reply on it.  Restore it and the
 308                    other fields in the message header needed for send,
 309                    since the header now reflects receipt of the reply.  */
 310                 m->header.msgh_local_port = rcv_name;
 311                 m->header.msgh_remote_port = remote_port;
 312                 m->header.msgh_id = msgid;
 313                 m->header.msgh_bits = msgh_bits;
 314                 /* Restore the two words clobbered by the reply data.  */
 315                 m->request.data = save_data;
 316
 317                 /* Restore the original mach_msg options.
 318                    OPTION may have had MACH_RCV_TIMEOUT added,
 319                    and/or MACH_SEND_MSG removed.  */
 320                 option = user_option;
 321                 timeout = user_timeout;
 322
 323                 /* Now we are ready to repeat the original message send.  */
 324                 goto message;
 325               }
 326             else
 327               /* The EINTR return indicates cancellation,
 328                  so clear the flag.  */
 329               ss->cancel = 0;
 330           }
 331       }
 332       break;
 333
 334     default:                    /* Quiet -Wswitch-enum.  */
 335     }
 336
 337   ss->intr_port = MACH_PORT_NULL;
 338
 339   return err;
 340 }