hurd/intr-msg.c

   1 /* Replacement for mach_msg used in interruptible Hurd RPCs.
   2    Copyright (C) 1995-2018 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <mach.h>
  20 #include <mach/mig_errors.h>
  21 #include <mach/mig_support.h>
  22 #include <hurd/signal.h>
  23 #include <assert.h>
  24
  25 #include "intr-msg.h"
  26
  27 #ifdef NDR_CHAR_ASCII           /* OSF Mach flavors have different names.  */
  28 # define mig_reply_header_t     mig_reply_error_t
  29 #endif
  30
  31 error_t
  32 _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
  33                          mach_msg_option_t option,
  34                          mach_msg_size_t send_size,
  35                          mach_msg_size_t rcv_size,
  36                          mach_port_t rcv_name,
  37                          mach_msg_timeout_t timeout,
  38                          mach_port_t notify)
  39 {
  40   error_t err;
  41   struct hurd_sigstate *ss;
  42   const mach_msg_option_t user_option = option;
  43   const mach_msg_timeout_t user_timeout = timeout;
  44
  45   struct clobber
  46   {
  47 #ifdef NDR_CHAR_ASCII
  48     NDR_record_t ndr;
  49 #else
  50     mach_msg_type_t type;
  51 #endif
  52     error_t err;
  53   };
  54   union msg
  55   {
  56     mach_msg_header_t header;
  57     mig_reply_header_t reply;
  58     struct
  59     {
  60       mach_msg_header_t header;
  61 #ifdef NDR_CHAR_ASCII
  62       NDR_record_t ndr;
  63 #else
  64       int type;
  65 #endif
  66       int code;
  67     } check;
  68     struct
  69     {
  70       mach_msg_header_t header;
  71       struct clobber data;
  72     } request;
  73   };
  74   union msg *const m = (void *) msg;
  75   mach_msg_bits_t msgh_bits;
  76   mach_port_t remote_port;
  77   mach_msg_id_t msgid;
  78   struct clobber save_data;
  79
  80   if ((option & (MACH_SEND_MSG|MACH_RCV_MSG)) != (MACH_SEND_MSG|MACH_RCV_MSG)
  81       || _hurd_msgport_thread == MACH_PORT_NULL)
  82     {
  83       /* Either this is not an RPC (i.e., only a send or only a receive),
  84          so it can't be interruptible; or, the signal thread is not set up
  85          yet, so we cannot do the normal signal magic.  Do a normal,
  86          uninterruptible mach_msg call instead.  */
  87       return __mach_msg (&m->header, option, send_size, rcv_size, rcv_name,
  88                          timeout, notify);
  89     }
  90
  91   ss = _hurd_self_sigstate ();
  92
  93   /* Save state that gets clobbered by an EINTR reply message.
  94      We will need to restore it if we want to retry the RPC.  */
  95   msgh_bits = m->header.msgh_bits;
  96   remote_port = m->header.msgh_remote_port;
  97   msgid = m->header.msgh_id;
  98   assert (rcv_size >= sizeof m->request);
  99   save_data = m->request.data;
 100
 101   /* Tell the signal thread that we are doing an interruptible RPC on
 102      this port.  If we get a signal and should return EINTR, the signal
 103      thread will set this variable to MACH_PORT_NULL.  The RPC might
 104      return EINTR when some other thread gets a signal, in which case we
 105      want to restart our call.  */
 106   ss->intr_port = m->header.msgh_remote_port;
 107
 108   /* A signal may arrive here, after intr_port is set, but before the
 109      mach_msg system call.  The signal handler might do an interruptible
 110      RPC, and clobber intr_port; then it would not be set properly when we
 111      actually did send the RPC, and a later signal wouldn't interrupt that
 112      RPC.  So, _hurd_setup_sighandler saves intr_port in the sigcontext,
 113      and sigreturn restores it.  */
 114
 115  message:
 116
 117   /* XXX
 118      At all points here (once SS->intr_port is set), the signal thread
 119      thinks we are "about to enter the syscall", and might mutate our
 120      return-value register.  This is bogus.
 121    */
 122
 123   if (ss->cancel)
 124     {
 125       /* We have been cancelled.  Don't do an RPC at all.  */
 126       ss->intr_port = MACH_PORT_NULL;
 127       ss->cancel = 0;
 128       return EINTR;
 129     }
 130
 131   /* Note that the signal trampoline code might modify our OPTION!  */
 132   err = INTR_MSG_TRAP (msg, option, send_size,
 133                        rcv_size, rcv_name, timeout, notify);
 134
 135   switch (err)
 136     {
 137     case MACH_RCV_TIMED_OUT:
 138       if (user_option & MACH_RCV_TIMEOUT)
 139         /* The real user RPC timed out.  */
 140         break;
 141       else
 142         /* The operation was supposedly interrupted, but still has
 143            not returned.  Declare it interrupted.  */
 144         goto interrupted;
 145
 146     case MACH_SEND_INTERRUPTED: /* RPC didn't get out.  */
 147       if (!(option & MACH_SEND_MSG))
 148         {
 149           /* Oh yes, it did!  Since we were not doing a message send,
 150              this return code cannot have come from the kernel!
 151              Instead, it was the signal thread mutating our state to tell
 152              us not to enter this RPC.  However, we are already in the receive!
 153              Since the signal thread thought we weren't in the RPC yet,
 154              it didn't do an interrupt_operation.
 155              XXX */
 156           goto retry_receive;
 157         }
 158       /* FALLTHROUGH */
 159
 160       /* These are the other codes that mean a pseudo-receive modified
 161          the message buffer and we might need to clean up the port rights.  */
 162     case MACH_SEND_TIMED_OUT:
 163     case MACH_SEND_INVALID_NOTIFY:
 164 #ifdef MACH_SEND_NO_NOTIFY
 165     case MACH_SEND_NO_NOTIFY:
 166 #endif
 167 #ifdef MACH_SEND_NOTIFY_IN_PROGRESS
 168     case MACH_SEND_NOTIFY_IN_PROGRESS:
 169 #endif
 170       if (MACH_MSGH_BITS_REMOTE (msg->msgh_bits) == MACH_MSG_TYPE_MOVE_SEND)
 171         {
 172           __mach_port_deallocate (__mach_task_self (), msg->msgh_remote_port);
 173           msg->msgh_bits
 174             = (MACH_MSGH_BITS (MACH_MSG_TYPE_COPY_SEND,
 175                                MACH_MSGH_BITS_LOCAL (msg->msgh_bits))
 176                | MACH_MSGH_BITS_OTHER (msg->msgh_bits));
 177         }
 178       if (msg->msgh_bits & MACH_MSGH_BITS_COMPLEX)
 179         {
 180 #ifndef MACH_MSG_PORT_DESCRIPTOR
 181           /* Check for MOVE_SEND rights in the message.  These hold refs
 182              that we need to release in case the message is in fact never
 183              re-sent later.  Since it might in fact be re-sent, we turn
 184              these into COPY_SEND's after deallocating the extra user ref;
 185              the caller is responsible for still holding a ref to go with
 186              the original COPY_SEND right, so the resend copies it again.  */
 187
 188           mach_msg_type_long_t *ty = (void *) (msg + 1);
 189           while ((void *) ty < (void *) msg + msg->msgh_size)
 190             {
 191               mach_msg_type_name_t name;
 192               mach_msg_type_size_t size;
 193               mach_msg_type_number_t number;
 194
 195               inline void clean_ports (mach_port_t *ports, int dealloc)
 196                 {
 197                   mach_msg_type_number_t i;
 198                   switch (name)
 199                     {
 200                     case MACH_MSG_TYPE_MOVE_SEND:
 201                       for (i = 0; i < number; i++)
 202                         __mach_port_deallocate (__mach_task_self (), *ports++);
 203                       if (ty->msgtl_header.msgt_longform)
 204                         ty->msgtl_name = MACH_MSG_TYPE_COPY_SEND;
 205                       else
 206                         ty->msgtl_header.msgt_name = MACH_MSG_TYPE_COPY_SEND;
 207                       break;
 208                     case MACH_MSG_TYPE_COPY_SEND:
 209                     case MACH_MSG_TYPE_MOVE_RECEIVE:
 210                       break;
 211                     default:
 212                       if (MACH_MSG_TYPE_PORT_ANY (name))
 213                         assert (! "unexpected port type in interruptible RPC");
 214                     }
 215                   if (dealloc)
 216                     __vm_deallocate (__mach_task_self (),
 217                                      (vm_address_t) ports,
 218                                      number * sizeof (mach_port_t));
 219                 }
 220
 221               if (ty->msgtl_header.msgt_longform)
 222                 {
 223                   name = ty->msgtl_name;
 224                   size = ty->msgtl_size;
 225                   number = ty->msgtl_number;
 226                   ty = (void *) ty + sizeof (mach_msg_type_long_t);
 227                 }
 228               else
 229                 {
 230                   name = ty->msgtl_header.msgt_name;
 231                   size = ty->msgtl_header.msgt_size;
 232                   number = ty->msgtl_header.msgt_number;
 233                   ty = (void *) ty + sizeof (mach_msg_type_t);
 234                 }
 235
 236               if (ty->msgtl_header.msgt_inline)
 237                 {
 238                   clean_ports ((void *) ty, 0);
 239                   /* calculate length of data in bytes, rounding up */
 240                   ty = (void *) ty + (((((number * size) + 7) >> 3)
 241                                        + sizeof (mach_msg_type_t) - 1)
 242                                       &~ (sizeof (mach_msg_type_t) - 1));
 243                 }
 244               else
 245                 {
 246                   clean_ports (*(void **) ty,
 247                                ty->msgtl_header.msgt_deallocate);
 248                   ty = (void *) ty + sizeof (void *);
 249                 }
 250             }
 251 #else  /* Untyped Mach IPC flavor. */
 252           mach_msg_body_t *body = (void *) (msg + 1);
 253           mach_msg_descriptor_t *desc = (void *) (body + 1);
 254           mach_msg_descriptor_t *desc_end = desc + body->msgh_descriptor_count;
 255           for (; desc < desc_end; ++desc)
 256             switch (desc->type.type)
 257               {
 258               case MACH_MSG_PORT_DESCRIPTOR:
 259                 switch (desc->port.disposition)
 260                   {
 261                   case MACH_MSG_TYPE_MOVE_SEND:
 262                     __mach_port_deallocate (mach_task_self (),
 263                                             desc->port.name);
 264                     desc->port.disposition = MACH_MSG_TYPE_COPY_SEND;
 265                     break;
 266                   case MACH_MSG_TYPE_COPY_SEND:
 267                   case MACH_MSG_TYPE_MOVE_RECEIVE:
 268                     break;
 269                   default:
 270                     assert (! "unexpected port type in interruptible RPC");
 271                   }
 272                 break;
 273               case MACH_MSG_OOL_DESCRIPTOR:
 274                 if (desc->out_of_line.deallocate)
 275                   __vm_deallocate (__mach_task_self (),
 276                                    (vm_address_t) desc->out_of_line.address,
 277                                    desc->out_of_line.size);
 278                 break;
 279               case MACH_MSG_OOL_PORTS_DESCRIPTOR:
 280                 switch (desc->ool_ports.disposition)
 281                   {
 282                   case MACH_MSG_TYPE_MOVE_SEND:
 283                     {
 284                       mach_msg_size_t i;
 285                       const mach_port_t *ports = desc->ool_ports.address;
 286                       for (i = 0; i < desc->ool_ports.count; ++i)
 287                         __mach_port_deallocate (__mach_task_self (), ports[i]);
 288                       desc->ool_ports.disposition = MACH_MSG_TYPE_COPY_SEND;
 289                       break;
 290                     }
 291                   case MACH_MSG_TYPE_COPY_SEND:
 292                   case MACH_MSG_TYPE_MOVE_RECEIVE:
 293                     break;
 294                   default:
 295                     assert (! "unexpected port type in interruptible RPC");
 296                   }
 297                 if (desc->ool_ports.deallocate)
 298                   __vm_deallocate (__mach_task_self (),
 299                                    (vm_address_t) desc->ool_ports.address,
 300                                    desc->ool_ports.count
 301                                    * sizeof (mach_port_t));
 302                 break;
 303               default:
 304                 assert (! "unexpected descriptor type in interruptible RPC");
 305               }
 306 #endif
 307         }
 308       break;
 309
 310     case EINTR:
 311       /* Either the process was stopped and continued,
 312          or the server doesn't support interrupt_operation.  */
 313       if (ss->intr_port != MACH_PORT_NULL)
 314         /* If this signal was for us and it should interrupt calls, the
 315            signal thread will have cleared SS->intr_port.
 316            Since it's not cleared, the signal was for another thread,
 317            or SA_RESTART is set.  Restart the interrupted call.  */
 318         {
 319           /* Make sure we have a valid reply port.  The one we were using
 320              may have been destroyed by interruption.  */
 321           m->header.msgh_local_port = rcv_name = __mig_get_reply_port ();
 322           m->header.msgh_bits = msgh_bits;
 323           option = user_option;
 324           timeout = user_timeout;
 325           goto message;
 326         }
 327       /* FALLTHROUGH */
 328
 329     case MACH_RCV_PORT_DIED:
 330       /* Server didn't respond to interrupt_operation,
 331          so the signal thread destroyed the reply port.  */
 332       /* FALLTHROUGH */
 333
 334     interrupted:
 335       err = EINTR;
 336
 337       /* The EINTR return indicates cancellation, so clear the flag.  */
 338       ss->cancel = 0;
 339       break;
 340
 341     case MACH_RCV_INTERRUPTED:  /* RPC sent; no reply.  */
 342       option &= ~MACH_SEND_MSG; /* Don't send again.  */
 343     retry_receive:
 344       if (ss->intr_port == MACH_PORT_NULL)
 345         {
 346           /* This signal or cancellation was for us.  We need to wait for
 347              the reply, but not hang forever.  */
 348           option |= MACH_RCV_TIMEOUT;
 349           /* Never decrease the user's timeout.  */
 350           if (!(user_option & MACH_RCV_TIMEOUT)
 351               || timeout > _hurd_interrupted_rpc_timeout)
 352             timeout = _hurd_interrupted_rpc_timeout;
 353         }
 354       else
 355         {
 356           option = user_option;
 357           timeout = user_timeout;
 358         }
 359       goto message;             /* Retry the receive.  */
 360
 361     case MACH_MSG_SUCCESS:
 362       {
 363         /* We got a reply.  Was it EINTR?  */
 364 #ifdef MACH_MSG_TYPE_BIT
 365         const union
 366         {
 367           mach_msg_type_t t;
 368           int i;
 369         } check =
 370           { t: { MACH_MSG_TYPE_INTEGER_T, sizeof (integer_t) * 8,
 371                  1, TRUE, FALSE, FALSE, 0 } };
 372 #endif
 373
 374         if (m->reply.RetCode == EINTR &&
 375             m->header.msgh_size == sizeof m->reply &&
 376 #ifdef MACH_MSG_TYPE_BIT
 377             m->check.type == check.i &&
 378 #endif
 379             !(m->header.msgh_bits & MACH_MSGH_BITS_COMPLEX))
 380           {
 381             /* It is indeed EINTR.  Is the interrupt for us?  */
 382             if (ss->intr_port != MACH_PORT_NULL)
 383               {
 384                 /* Nope; repeat the RPC.
 385                    XXX Resources moved? */
 386
 387                 assert (m->header.msgh_id == msgid + 100);
 388
 389                 /* We know we have a valid reply port, because we just
 390                    received the EINTR reply on it.  Restore it and the
 391                    other fields in the message header needed for send,
 392                    since the header now reflects receipt of the reply.  */
 393                 m->header.msgh_local_port = rcv_name;
 394                 m->header.msgh_remote_port = remote_port;
 395                 m->header.msgh_id = msgid;
 396                 m->header.msgh_bits = msgh_bits;
 397                 /* Restore the two words clobbered by the reply data.  */
 398                 m->request.data = save_data;
 399
 400                 /* Restore the original mach_msg options.
 401                    OPTION may have had MACH_RCV_TIMEOUT added,
 402                    and/or MACH_SEND_MSG removed.  */
 403                 option = user_option;
 404                 timeout = user_timeout;
 405
 406                 /* Now we are ready to repeat the original message send.  */
 407                 goto message;
 408               }
 409             else
 410               /* The EINTR return indicates cancellation,
 411                  so clear the flag.  */
 412               ss->cancel = 0;
 413           }
 414       }
 415       break;
 416
 417     default:                    /* Quiet -Wswitch-enum.  */
 418       break;
 419     }
 420
 421   ss->intr_port = MACH_PORT_NULL;
 422
 423   return err;
 424 }