hurd/intr-msg.c

   1 /* Replacement for mach_msg used in interruptible Hurd RPCs.
   2    Copyright (C) 1995-2022 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    <https://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   /* 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                        &ss->cancel, &ss->intr_port);
 121
 122   switch (err)
 123     {
 124     case MACH_RCV_TIMED_OUT:
 125       if (user_option & MACH_RCV_TIMEOUT)
 126         /* The real user RPC timed out.  */
 127         break;
 128       else
 129         /* The operation was supposedly interrupted, but still has
 130            not returned.  Declare it interrupted.  */
 131         goto dead;
 132
 133     case MACH_SEND_INTERRUPTED: /* RPC didn't get out.  */
 134       if (!(option & MACH_SEND_MSG))
 135         {
 136           /* Oh yes, it did!  Since we were not doing a message send,
 137              this return code cannot have come from the kernel!
 138              Instead, it was the signal thread mutating our state to tell
 139              us not to enter this RPC.  However, we are already in the receive!
 140              Since the signal thread thought we weren't in the RPC yet,
 141              it didn't do an interrupt_operation.
 142              XXX */
 143           goto retry_receive;
 144         }
 145       /* FALLTHROUGH */
 146
 147       /* These are the other codes that mean a pseudo-receive modified
 148          the message buffer and we might need to clean up the port rights.  */
 149     case MACH_SEND_TIMED_OUT:
 150     case MACH_SEND_INVALID_NOTIFY:
 151 #ifdef MACH_SEND_NO_NOTIFY
 152     case MACH_SEND_NO_NOTIFY:
 153 #endif
 154 #ifdef MACH_SEND_NOTIFY_IN_PROGRESS
 155     case MACH_SEND_NOTIFY_IN_PROGRESS:
 156 #endif
 157       if (MACH_MSGH_BITS_REMOTE (msg->msgh_bits) == MACH_MSG_TYPE_MOVE_SEND)
 158         {
 159           __mach_port_deallocate (__mach_task_self (), msg->msgh_remote_port);
 160           msg->msgh_bits
 161             = (MACH_MSGH_BITS (MACH_MSG_TYPE_COPY_SEND,
 162                                MACH_MSGH_BITS_LOCAL (msg->msgh_bits))
 163                | MACH_MSGH_BITS_OTHER (msg->msgh_bits));
 164         }
 165       if (msg->msgh_bits & MACH_MSGH_BITS_COMPLEX)
 166         {
 167 #ifndef MACH_MSG_PORT_DESCRIPTOR
 168           /* Check for MOVE_SEND rights in the message.  These hold refs
 169              that we need to release in case the message is in fact never
 170              re-sent later.  Since it might in fact be re-sent, we turn
 171              these into COPY_SEND's after deallocating the extra user ref;
 172              the caller is responsible for still holding a ref to go with
 173              the original COPY_SEND right, so the resend copies it again.  */
 174
 175           mach_msg_type_long_t *ty = (void *) (msg + 1);
 176           while ((void *) ty < (void *) msg + msg->msgh_size)
 177             {
 178               mach_msg_type_name_t name;
 179               mach_msg_type_size_t size;
 180               mach_msg_type_number_t number;
 181
 182               inline void clean_ports (mach_port_t *ports, int dealloc)
 183                 {
 184                   mach_msg_type_number_t i;
 185                   switch (name)
 186                     {
 187                     case MACH_MSG_TYPE_MOVE_SEND:
 188                       for (i = 0; i < number; i++)
 189                         __mach_port_deallocate (__mach_task_self (), *ports++);
 190                       if (ty->msgtl_header.msgt_longform)
 191                         ty->msgtl_name = MACH_MSG_TYPE_COPY_SEND;
 192                       else
 193                         ty->msgtl_header.msgt_name = MACH_MSG_TYPE_COPY_SEND;
 194                       break;
 195                     case MACH_MSG_TYPE_COPY_SEND:
 196                     case MACH_MSG_TYPE_MOVE_RECEIVE:
 197                       break;
 198                     default:
 199                       if (MACH_MSG_TYPE_PORT_ANY (name))
 200                         assert (! "unexpected port type in interruptible RPC");
 201                     }
 202                   if (dealloc)
 203                     __vm_deallocate (__mach_task_self (),
 204                                      (vm_address_t) ports,
 205                                      number * sizeof (mach_port_t));
 206                 }
 207
 208               if (ty->msgtl_header.msgt_longform)
 209                 {
 210                   name = ty->msgtl_name;
 211                   size = ty->msgtl_size;
 212                   number = ty->msgtl_number;
 213                   ty = (void *) ty + sizeof (mach_msg_type_long_t);
 214                 }
 215               else
 216                 {
 217                   name = ty->msgtl_header.msgt_name;
 218                   size = ty->msgtl_header.msgt_size;
 219                   number = ty->msgtl_header.msgt_number;
 220                   ty = (void *) ty + sizeof (mach_msg_type_t);
 221                 }
 222
 223               if (ty->msgtl_header.msgt_inline)
 224                 {
 225                   clean_ports ((void *) ty, 0);
 226                   /* calculate length of data in bytes, rounding up */
 227                   ty = (void *) ty + (((((number * size) + 7) >> 3)
 228                                        + sizeof (mach_msg_type_t) - 1)
 229                                       &~ (sizeof (mach_msg_type_t) - 1));
 230                 }
 231               else
 232                 {
 233                   clean_ports (*(void **) ty,
 234                                ty->msgtl_header.msgt_deallocate);
 235                   ty = (void *) ty + sizeof (void *);
 236                 }
 237             }
 238 #else  /* Untyped Mach IPC flavor. */
 239           mach_msg_body_t *body = (void *) (msg + 1);
 240           mach_msg_descriptor_t *desc = (void *) (body + 1);
 241           mach_msg_descriptor_t *desc_end = desc + body->msgh_descriptor_count;
 242           for (; desc < desc_end; ++desc)
 243             switch (desc->type.type)
 244               {
 245               case MACH_MSG_PORT_DESCRIPTOR:
 246                 switch (desc->port.disposition)
 247                   {
 248                   case MACH_MSG_TYPE_MOVE_SEND:
 249                     __mach_port_deallocate (mach_task_self (),
 250                                             desc->port.name);
 251                     desc->port.disposition = MACH_MSG_TYPE_COPY_SEND;
 252                     break;
 253                   case MACH_MSG_TYPE_COPY_SEND:
 254                   case MACH_MSG_TYPE_MOVE_RECEIVE:
 255                     break;
 256                   default:
 257                     assert (! "unexpected port type in interruptible RPC");
 258                   }
 259                 break;
 260               case MACH_MSG_OOL_DESCRIPTOR:
 261                 if (desc->out_of_line.deallocate)
 262                   __vm_deallocate (__mach_task_self (),
 263                                    (vm_address_t) desc->out_of_line.address,
 264                                    desc->out_of_line.size);
 265                 break;
 266               case MACH_MSG_OOL_PORTS_DESCRIPTOR:
 267                 switch (desc->ool_ports.disposition)
 268                   {
 269                   case MACH_MSG_TYPE_MOVE_SEND:
 270                     {
 271                       mach_msg_size_t i;
 272                       const mach_port_t *ports = desc->ool_ports.address;
 273                       for (i = 0; i < desc->ool_ports.count; ++i)
 274                         __mach_port_deallocate (__mach_task_self (), ports[i]);
 275                       desc->ool_ports.disposition = MACH_MSG_TYPE_COPY_SEND;
 276                       break;
 277                     }
 278                   case MACH_MSG_TYPE_COPY_SEND:
 279                   case MACH_MSG_TYPE_MOVE_RECEIVE:
 280                     break;
 281                   default:
 282                     assert (! "unexpected port type in interruptible RPC");
 283                   }
 284                 if (desc->ool_ports.deallocate)
 285                   __vm_deallocate (__mach_task_self (),
 286                                    (vm_address_t) desc->ool_ports.address,
 287                                    desc->ool_ports.count
 288                                    * sizeof (mach_port_t));
 289                 break;
 290               default:
 291                 assert (! "unexpected descriptor type in interruptible RPC");
 292               }
 293 #endif
 294         }
 295       break;
 296
 297     case EINTR:
 298       /* Either the process was stopped and continued,
 299          or the server doesn't support interrupt_operation.  */
 300       if (ss->intr_port != MACH_PORT_NULL)
 301         /* If this signal was for us and it should interrupt calls, the
 302            signal thread will have cleared SS->intr_port.
 303            Since it's not cleared, the signal was for another thread,
 304            or SA_RESTART is set.  Restart the interrupted call.  */
 305         {
 306           /* Make sure we have a valid reply port.  The one we were using
 307              may have been destroyed by interruption.  */
 308           m->header.msgh_local_port = rcv_name = __mig_get_reply_port ();
 309           m->header.msgh_bits = msgh_bits;
 310           option = user_option;
 311           timeout = user_timeout;
 312           goto message;
 313         }
 314       err = EINTR;
 315
 316       /* The EINTR return indicates cancellation, so clear the flag.  */
 317       ss->cancel = 0;
 318       break;
 319
 320     case MACH_RCV_PORT_DIED:
 321       /* Server didn't respond to interrupt_operation,
 322          so the signal thread destroyed the reply port.  */
 323       /* FALLTHROUGH */
 324
 325     dead:
 326       err = EIEIO;
 327
 328       /* The EIEIO return indicates cancellation, so clear the flag.  */
 329       ss->cancel = 0;
 330       break;
 331
 332     case MACH_RCV_INTERRUPTED:  /* RPC sent; no reply.  */
 333       option &= ~MACH_SEND_MSG; /* Don't send again.  */
 334     retry_receive:
 335       if (ss->intr_port == MACH_PORT_NULL)
 336         {
 337           /* This signal or cancellation was for us.  We need to wait for
 338              the reply, but not hang forever.  */
 339           option |= MACH_RCV_TIMEOUT;
 340           /* Never decrease the user's timeout.  */
 341           if (!(user_option & MACH_RCV_TIMEOUT)
 342               || timeout > _hurd_interrupted_rpc_timeout)
 343             timeout = _hurd_interrupted_rpc_timeout;
 344         }
 345       else
 346         {
 347           option = user_option;
 348           timeout = user_timeout;
 349         }
 350       goto message;             /* Retry the receive.  */
 351
 352     case MACH_MSG_SUCCESS:
 353       {
 354         /* We got a reply.  Was it EINTR?  */
 355 #ifdef MACH_MSG_TYPE_BIT
 356         const union
 357         {
 358           mach_msg_type_t t;
 359           int i;
 360         } check =
 361           { t: { MACH_MSG_TYPE_INTEGER_T, sizeof (integer_t) * 8,
 362                  1, TRUE, FALSE, FALSE, 0 } };
 363 #endif
 364
 365         if (m->reply.RetCode == EINTR
 366             && m->header.msgh_size == sizeof m->reply
 367 #ifdef MACH_MSG_TYPE_BIT
 368             && m->check.type == check.i
 369 #endif
 370             && !(m->header.msgh_bits & MACH_MSGH_BITS_COMPLEX))
 371           {
 372             /* It is indeed EINTR.  Is the interrupt for us?  */
 373             if (ss->intr_port != MACH_PORT_NULL)
 374               {
 375                 /* Nope; repeat the RPC.
 376                    XXX Resources moved? */
 377
 378                 assert (m->header.msgh_id == msgid + 100);
 379
 380                 /* We know we have a valid reply port, because we just
 381                    received the EINTR reply on it.  Restore it and the
 382                    other fields in the message header needed for send,
 383                    since the header now reflects receipt of the reply.  */
 384                 m->header.msgh_local_port = rcv_name;
 385                 m->header.msgh_remote_port = remote_port;
 386                 m->header.msgh_id = msgid;
 387                 m->header.msgh_bits = msgh_bits;
 388                 /* Restore the two words clobbered by the reply data.  */
 389                 m->request.data = save_data;
 390
 391                 /* Restore the original mach_msg options.
 392                    OPTION may have had MACH_RCV_TIMEOUT added,
 393                    and/or MACH_SEND_MSG removed.  */
 394                 option = user_option;
 395                 timeout = user_timeout;
 396
 397                 /* Now we are ready to repeat the original message send.  */
 398                 goto message;
 399               }
 400             else
 401               /* The EINTR return indicates cancellation,
 402                  so clear the flag.  */
 403               ss->cancel = 0;
 404           }
 405       }
 406       break;
 407
 408     default:                    /* Quiet -Wswitch-enum.  */
 409       break;
 410     }
 411
 412   ss->intr_port = MACH_PORT_NULL;
 413
 414   return err;
 415 }
 416 libc_hidden_def (_hurd_intr_rpc_mach_msg)