hurd/intr-msg.c

   1 /* Replacement for mach_msg used in interruptible Hurd RPCs.
   2    Copyright (C) 1995-2023 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_rpc.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 error_t
  29 _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
  30                          mach_msg_option_t option,
  31                          mach_msg_size_t send_size,
  32                          mach_msg_size_t rcv_size,
  33                          mach_port_t rcv_name,
  34                          mach_msg_timeout_t timeout,
  35                          mach_port_t notify)
  36 {
  37   error_t err;
  38   struct hurd_sigstate *ss;
  39   const mach_msg_option_t user_option = option;
  40   const mach_msg_timeout_t user_timeout = timeout;
  41
  42   struct clobber
  43   {
  44     mach_msg_type_t type;
  45     error_t err;
  46   };
  47   union msg
  48   {
  49     mach_msg_header_t header;
  50     mig_reply_header_t reply;
  51     struct
  52     {
  53       mach_msg_header_t header;
  54       mach_msg_type_t type;
  55       int code;
  56     } check;
  57     struct
  58     {
  59       mach_msg_header_t header;
  60       struct clobber data;
  61     } request;
  62   };
  63   union msg *const m = (void *) msg;
  64   mach_msg_bits_t msgh_bits;
  65   mach_port_t remote_port;
  66   mach_msg_id_t msgid;
  67   struct clobber save_data;
  68
  69   if ((option & (MACH_SEND_MSG|MACH_RCV_MSG)) != (MACH_SEND_MSG|MACH_RCV_MSG)
  70       || _hurd_msgport_thread == MACH_PORT_NULL)
  71     {
  72       /* Either this is not an RPC (i.e., only a send or only a receive),
  73          so it can't be interruptible; or, the signal thread is not set up
  74          yet, so we cannot do the normal signal magic.  Do a normal,
  75          uninterruptible mach_msg call instead.  */
  76       return __mach_msg (&m->header, option, send_size, rcv_size, rcv_name,
  77                          timeout, notify);
  78     }
  79
  80   ss = _hurd_self_sigstate ();
  81
  82   /* Save state that gets clobbered by an EINTR reply message.
  83      We will need to restore it if we want to retry the RPC.  */
  84   msgh_bits = m->header.msgh_bits;
  85   remote_port = m->header.msgh_remote_port;
  86   msgid = m->header.msgh_id;
  87   assert (rcv_size >= sizeof m->request);
  88   save_data = m->request.data;
  89
  90   /* Tell the signal thread that we are doing an interruptible RPC on
  91      this port.  If we get a signal and should return EINTR, the signal
  92      thread will set this variable to MACH_PORT_NULL.  The RPC might
  93      return EINTR when some other thread gets a signal, in which case we
  94      want to restart our call.  */
  95   ss->intr_port = m->header.msgh_remote_port;
  96
  97   /* A signal may arrive here, after intr_port is set, but before the
  98      mach_msg system call.  The signal handler might do an interruptible
  99      RPC, and clobber intr_port; then it would not be set properly when we
 100      actually did send the RPC, and a later signal wouldn't interrupt that
 101      RPC.  So, _hurd_setup_sighandler saves intr_port in the sigcontext,
 102      and sigreturn restores it.  */
 103
 104  message:
 105
 106   /* Note that the signal trampoline code might modify our OPTION!  */
 107   err = INTR_MSG_TRAP (msg, option, send_size,
 108                        rcv_size, rcv_name, timeout, notify,
 109                        &ss->cancel, &ss->intr_port);
 110
 111   switch (err)
 112     {
 113     case MACH_RCV_TIMED_OUT:
 114       if (user_option & MACH_RCV_TIMEOUT)
 115         /* The real user RPC timed out.  */
 116         break;
 117       else
 118         /* The operation was supposedly interrupted, but still has
 119            not returned.  Declare it interrupted.  */
 120         goto dead;
 121
 122     case MACH_SEND_INTERRUPTED: /* RPC didn't get out.  */
 123       if (!(option & MACH_SEND_MSG))
 124         {
 125           /* Oh yes, it did!  Since we were not doing a message send,
 126              this return code cannot have come from the kernel!
 127              Instead, it was the signal thread mutating our state to tell
 128              us not to enter this RPC.  However, we are already in the receive!
 129              Since the signal thread thought we weren't in the RPC yet,
 130              it didn't do an interrupt_operation.
 131              XXX */
 132           goto retry_receive;
 133         }
 134       if (!(option & MACH_SEND_INTERRUPT))
 135         {
 136           option = user_option;
 137           timeout = user_timeout;
 138           goto message;
 139         }
 140       /* FALLTHROUGH */
 141
 142       /* These are the other codes that mean a pseudo-receive modified
 143          the message buffer and we might need to clean up the port rights.  */
 144     case MACH_SEND_TIMED_OUT:
 145     case MACH_SEND_INVALID_NOTIFY:
 146 #ifdef MACH_SEND_NO_NOTIFY
 147     case MACH_SEND_NO_NOTIFY:
 148 #endif
 149 #ifdef MACH_SEND_NOTIFY_IN_PROGRESS
 150     case MACH_SEND_NOTIFY_IN_PROGRESS:
 151 #endif
 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_and_memory (char *data, const vm_size_t length,
 177                                                 int dealloc)
 178                 {
 179                   mach_msg_type_number_t i;
 180                   switch (name)
 181                     {
 182                     case MACH_MSG_TYPE_MOVE_SEND:
 183                       mach_port_t *ports = (mach_port_t *) data;
 184                       for (i = 0; i < number; i++)
 185                         __mach_port_deallocate (__mach_task_self (), *ports++);
 186                       if (ty->msgtl_header.msgt_longform)
 187                         ty->msgtl_name = MACH_MSG_TYPE_COPY_SEND;
 188                       else
 189                         ty->msgtl_header.msgt_name = MACH_MSG_TYPE_COPY_SEND;
 190                       break;
 191                     case MACH_MSG_TYPE_COPY_SEND:
 192                     case MACH_MSG_TYPE_MOVE_RECEIVE:
 193                       break;
 194                     default:
 195                       if (MACH_MSG_TYPE_PORT_ANY (name))
 196                         assert (! "unexpected port type in interruptible RPC");
 197                     }
 198                   if (dealloc)
 199                     __vm_deallocate (__mach_task_self (), (vm_address_t) data, length);
 200                 }
 201
 202               char *data;
 203               if (ty->msgtl_header.msgt_longform)
 204                 {
 205                   name = ty->msgtl_name;
 206                   size = ty->msgtl_size;
 207                   number = ty->msgtl_number;
 208                   data = (char *) ty + sizeof (mach_msg_type_long_t);
 209                 }
 210               else
 211                 {
 212                   name = ty->msgtl_header.msgt_name;
 213                   size = ty->msgtl_header.msgt_size;
 214                   number = ty->msgtl_header.msgt_number;
 215                   data = (char *) ty + sizeof (mach_msg_type_t);
 216                 }
 217
 218               const vm_size_t length = ((number * size) + 7) >> 3;
 219               if (ty->msgtl_header.msgt_inline)
 220                 {
 221                   /* Calculate length of data in bytes.  */
 222                   clean_ports_and_memory (data, length, 0);
 223                   /* Move to the next argument.  */
 224                   ty = (void *) PTR_ALIGN_UP (data + length, __alignof__ (uintptr_t));
 225                 }
 226               else
 227                 {
 228                   clean_ports_and_memory (*(void **) data, length,
 229                                ty->msgtl_header.msgt_deallocate);
 230                   ty = (void *) data + sizeof (void *);
 231                 }
 232             }
 233         }
 234       break;
 235
 236     case EINTR:
 237       /* Either the process was stopped and continued,
 238          or the server doesn't support interrupt_operation.  */
 239       if (ss->intr_port != MACH_PORT_NULL)
 240         /* If this signal was for us and it should interrupt calls, the
 241            signal thread will have cleared SS->intr_port.
 242            Since it's not cleared, the signal was for another thread,
 243            or SA_RESTART is set.  Restart the interrupted call.  */
 244         {
 245           /* Make sure we have a valid reply port.  The one we were using
 246              may have been destroyed by interruption.  */
 247           __mig_dealloc_reply_port (rcv_name);
 248           m->header.msgh_local_port = rcv_name = __mig_get_reply_port ();
 249           m->header.msgh_bits = msgh_bits;
 250           option = user_option;
 251           timeout = user_timeout;
 252           goto message;
 253         }
 254       err = EINTR;
 255
 256       /* The EINTR return indicates cancellation, so clear the flag.  */
 257       ss->cancel = 0;
 258       break;
 259
 260     case MACH_RCV_PORT_DIED:
 261       /* Server didn't respond to interrupt_operation,
 262          so the signal thread destroyed the reply port.  */
 263       /* FALLTHROUGH */
 264
 265     dead:
 266       err = EIEIO;
 267
 268       /* The EIEIO return indicates cancellation, so clear the flag.  */
 269       ss->cancel = 0;
 270       break;
 271
 272     case MACH_RCV_INTERRUPTED:  /* RPC sent; no reply.  */
 273       option &= ~MACH_SEND_MSG; /* Don't send again.  */
 274     retry_receive:
 275       if (ss->intr_port == MACH_PORT_NULL)
 276         {
 277           /* This signal or cancellation was for us.  We need to wait for
 278              the reply, but not hang forever.  */
 279           option |= MACH_RCV_TIMEOUT;
 280           /* Never decrease the user's timeout.  */
 281           if (!(user_option & MACH_RCV_TIMEOUT)
 282               || timeout > _hurd_interrupted_rpc_timeout)
 283             timeout = _hurd_interrupted_rpc_timeout;
 284         }
 285       else
 286         {
 287           option = user_option;
 288           timeout = user_timeout;
 289         }
 290       goto message;             /* Retry the receive.  */
 291
 292     case MACH_MSG_SUCCESS:
 293       {
 294         /* We got a reply.  Was it EINTR?  */
 295 #ifdef MACH_MSG_TYPE_BIT
 296         static const mach_msg_type_t type_check = {
 297           .msgt_name = MACH_MSG_TYPE_INTEGER_T,
 298           .msgt_size = sizeof (integer_t) * 8,
 299           .msgt_number = 1,
 300           .msgt_inline = TRUE,
 301           .msgt_longform = FALSE,
 302           .msgt_deallocate = FALSE,
 303           .msgt_unused = 0
 304         };
 305 #endif
 306
 307         if (m->reply.RetCode == EINTR
 308             && m->header.msgh_size == sizeof m->reply
 309 #ifdef MACH_MSG_TYPE_BIT
 310             && !BAD_TYPECHECK(&m->check.type, &type_check)
 311 #endif
 312             && !(m->header.msgh_bits & MACH_MSGH_BITS_COMPLEX))
 313           {
 314             /* It is indeed EINTR.  Is the interrupt for us?  */
 315             if (ss->intr_port != MACH_PORT_NULL)
 316               {
 317                 /* Nope; repeat the RPC.
 318                    XXX Resources moved? */
 319
 320                 assert (m->header.msgh_id == msgid + 100);
 321
 322                 /* We know we have a valid reply port, because we just
 323                    received the EINTR reply on it.  Restore it and the
 324                    other fields in the message header needed for send,
 325                    since the header now reflects receipt of the reply.  */
 326                 m->header.msgh_local_port = rcv_name;
 327                 m->header.msgh_remote_port = remote_port;
 328                 m->header.msgh_id = msgid;
 329                 m->header.msgh_bits = msgh_bits;
 330                 /* Restore the two words clobbered by the reply data.  */
 331                 m->request.data = save_data;
 332
 333                 /* Restore the original mach_msg options.
 334                    OPTION may have had MACH_RCV_TIMEOUT added,
 335                    and/or MACH_SEND_MSG removed.  */
 336                 option = user_option;
 337                 timeout = user_timeout;
 338
 339                 /* Now we are ready to repeat the original message send.  */
 340                 goto message;
 341               }
 342             else
 343               /* The EINTR return indicates cancellation,
 344                  so clear the flag.  */
 345               ss->cancel = 0;
 346           }
 347       }
 348       break;
 349
 350     default:                    /* Quiet -Wswitch-enum.  */
 351       break;
 352     }
 353
 354   ss->intr_port = MACH_PORT_NULL;
 355
 356   return err;
 357 }
 358 libc_hidden_def (_hurd_intr_rpc_mach_msg)