hurd/intr-msg.c

   1 /* Replacement for mach_msg used in interruptible Hurd RPCs.
   2    Copyright (C) 1995-2024 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     union {
  46       error_t err;
  47       uintptr_t align;
  48     };
  49   };
  50   union msg
  51   {
  52     mach_msg_header_t header;
  53     mig_reply_header_t reply;
  54     struct
  55     {
  56       mach_msg_header_t header;
  57       mach_msg_type_t type;
  58       int code;
  59     } check;
  60     struct
  61     {
  62       mach_msg_header_t header;
  63       struct clobber data;
  64     } request;
  65   };
  66   union msg *const m = (void *) msg;
  67   mach_msg_bits_t msgh_bits;
  68   mach_port_t remote_port;
  69   mach_msg_id_t msgid;
  70   struct clobber save_data;
  71
  72   if ((option & (MACH_SEND_MSG|MACH_RCV_MSG)) != (MACH_SEND_MSG|MACH_RCV_MSG)
  73       || _hurd_msgport_thread == MACH_PORT_NULL)
  74     {
  75       /* Either this is not an RPC (i.e., only a send or only a receive),
  76          so it can't be interruptible; or, the signal thread is not set up
  77          yet, so we cannot do the normal signal magic.  Do a normal,
  78          uninterruptible mach_msg call instead.  */
  79       return __mach_msg (&m->header, option, send_size, rcv_size, rcv_name,
  80                          timeout, notify);
  81     }
  82
  83   ss = _hurd_self_sigstate ();
  84
  85   /* Save state that gets clobbered by an EINTR reply message.
  86      We will need to restore it if we want to retry the RPC.  */
  87   msgh_bits = m->header.msgh_bits;
  88   remote_port = m->header.msgh_remote_port;
  89   msgid = m->header.msgh_id;
  90   assert (rcv_size >= sizeof m->request);
  91   save_data = m->request.data;
  92
  93   /* Tell the signal thread that we are doing an interruptible RPC on
  94      this port.  If we get a signal and should return EINTR, the signal
  95      thread will set this variable to MACH_PORT_NULL.  The RPC might
  96      return EINTR when some other thread gets a signal, in which case we
  97      want to restart our call.  */
  98   ss->intr_port = m->header.msgh_remote_port;
  99
 100   /* A signal may arrive here, after intr_port is set, but before the
 101      mach_msg system call.  The signal handler might do an interruptible
 102      RPC, and clobber intr_port; then it would not be set properly when we
 103      actually did send the RPC, and a later signal wouldn't interrupt that
 104      RPC.  So, _hurd_setup_sighandler saves intr_port in the sigcontext,
 105      and sigreturn restores it.  */
 106
 107  message:
 108
 109   /* Note that the signal trampoline code might modify our OPTION!  */
 110   err = INTR_MSG_TRAP (msg, option, send_size,
 111                        rcv_size, rcv_name, timeout, notify,
 112                        &ss->cancel, &ss->intr_port);
 113
 114   switch (err)
 115     {
 116     case MACH_RCV_TIMED_OUT:
 117       if (user_option & MACH_RCV_TIMEOUT)
 118         /* The real user RPC timed out.  */
 119         break;
 120       else
 121         /* The operation was supposedly interrupted, but still has
 122            not returned.  Declare it interrupted.  */
 123         goto dead;
 124
 125     case MACH_SEND_INTERRUPTED: /* RPC didn't get out.  */
 126       if (!(option & MACH_SEND_MSG))
 127         {
 128           /* Oh yes, it did!  Since we were not doing a message send,
 129              this return code cannot have come from the kernel!
 130              Instead, it was the signal thread mutating our state to tell
 131              us not to enter this RPC.  However, we are already in the receive!
 132              Since the signal thread thought we weren't in the RPC yet,
 133              it didn't do an interrupt_operation.
 134              XXX */
 135           goto retry_receive;
 136         }
 137       if (!(option & MACH_SEND_INTERRUPT))
 138         {
 139           option = user_option;
 140           timeout = user_timeout;
 141           goto message;
 142         }
 143       /* FALLTHROUGH */
 144
 145       /* These are the other codes that mean a pseudo-receive modified
 146          the message buffer and we might need to clean up the port rights.  */
 147     case MACH_SEND_TIMED_OUT:
 148     case MACH_SEND_INVALID_NOTIFY:
 149 #ifdef MACH_SEND_NO_NOTIFY
 150     case MACH_SEND_NO_NOTIFY:
 151 #endif
 152 #ifdef MACH_SEND_NOTIFY_IN_PROGRESS
 153     case MACH_SEND_NOTIFY_IN_PROGRESS:
 154 #endif
 155       if (MACH_MSGH_BITS_REMOTE (msg->msgh_bits) == MACH_MSG_TYPE_MOVE_SEND)
 156         {
 157           __mach_port_deallocate (__mach_task_self (), msg->msgh_remote_port);
 158           msg->msgh_bits
 159             = (MACH_MSGH_BITS (MACH_MSG_TYPE_COPY_SEND,
 160                                MACH_MSGH_BITS_LOCAL (msg->msgh_bits))
 161                | MACH_MSGH_BITS_OTHER (msg->msgh_bits));
 162         }
 163       if (msg->msgh_bits & MACH_MSGH_BITS_COMPLEX)
 164         {
 165           /* Check for MOVE_SEND rights in the message.  These hold refs
 166              that we need to release in case the message is in fact never
 167              re-sent later.  Since it might in fact be re-sent, we turn
 168              these into COPY_SEND's after deallocating the extra user ref;
 169              the caller is responsible for still holding a ref to go with
 170              the original COPY_SEND right, so the resend copies it again.  */
 171
 172           mach_msg_type_long_t *ty = (void *) (msg + 1);
 173           while ((void *) ty < (void *) msg + msg->msgh_size)
 174             {
 175               mach_msg_type_name_t name;
 176               mach_msg_type_size_t size;
 177               mach_msg_type_number_t number;
 178
 179               inline void clean_ports_and_memory (char *data, const vm_size_t length,
 180                                                 int dealloc)
 181                 {
 182                   mach_msg_type_number_t i;
 183                   switch (name)
 184                     {
 185                     case MACH_MSG_TYPE_MOVE_SEND:
 186                       mach_port_t *ports = (mach_port_t *) data;
 187                       for (i = 0; i < number; i++)
 188                         __mach_port_deallocate (__mach_task_self (), *ports++);
 189                       if (ty->msgtl_header.msgt_longform)
 190                         ty->msgtl_name = MACH_MSG_TYPE_COPY_SEND;
 191                       else
 192                         ty->msgtl_header.msgt_name = MACH_MSG_TYPE_COPY_SEND;
 193                       break;
 194                     case MACH_MSG_TYPE_COPY_SEND:
 195                     case MACH_MSG_TYPE_MOVE_RECEIVE:
 196                       break;
 197                     default:
 198                       if (MACH_MSG_TYPE_PORT_ANY (name))
 199                         assert (! "unexpected port type in interruptible RPC");
 200                     }
 201                   if (dealloc)
 202                     __vm_deallocate (__mach_task_self (), (vm_address_t) data, length);
 203                 }
 204
 205               inline void clean_inlined_ports (mach_port_name_inlined_t *ports)
 206                 {
 207                   mach_msg_type_number_t i;
 208                   switch (name)
 209                     {
 210                     case MACH_MSG_TYPE_MOVE_SEND:
 211                       for (i = 0; i < number; i++)
 212                         __mach_port_deallocate (__mach_task_self (), ports[i].name);
 213                       if (ty->msgtl_header.msgt_longform)
 214                         ty->msgtl_name = MACH_MSG_TYPE_COPY_SEND;
 215                       else
 216                         ty->msgtl_header.msgt_name = MACH_MSG_TYPE_COPY_SEND;
 217                       break;
 218                     case MACH_MSG_TYPE_COPY_SEND:
 219                     case MACH_MSG_TYPE_MOVE_RECEIVE:
 220                       break;
 221                     default:
 222                       if (MACH_MSG_TYPE_PORT_ANY (name))
 223                         assert (! "unexpected port type in interruptible RPC");
 224                     }
 225                 }
 226
 227               char *data;
 228               if (ty->msgtl_header.msgt_longform)
 229                 {
 230                   name = ty->msgtl_name;
 231                   size = ty->msgtl_size;
 232                   number = ty->msgtl_number;
 233                   data = (char *) ty + sizeof (mach_msg_type_long_t);
 234                 }
 235               else
 236                 {
 237                   name = ty->msgtl_header.msgt_name;
 238                   size = ty->msgtl_header.msgt_size;
 239                   number = ty->msgtl_header.msgt_number;
 240                   data = (char *) ty + sizeof (mach_msg_type_t);
 241                 }
 242
 243               /* Calculate length of data in bytes.  */
 244               const vm_size_t length = ((number * size) + 7) >> 3;
 245               if (ty->msgtl_header.msgt_inline)
 246                 {
 247                   clean_inlined_ports ((mach_port_name_inlined_t *) data);
 248                   /* Move to the next argument.  */
 249                   ty = (void *) PTR_ALIGN_UP (data + length, __alignof__ (uintptr_t));
 250                 }
 251               else
 252                 {
 253                   clean_ports_and_memory (*(void **) data, length,
 254                                ty->msgtl_header.msgt_deallocate);
 255                   ty = (void *) data + sizeof (void *);
 256                 }
 257             }
 258         }
 259       break;
 260
 261     case EINTR:
 262       /* Either the process was stopped and continued,
 263          or the server doesn't support interrupt_operation.  */
 264       if (ss->intr_port != MACH_PORT_NULL)
 265         /* If this signal was for us and it should interrupt calls, the
 266            signal thread will have cleared SS->intr_port.
 267            Since it's not cleared, the signal was for another thread,
 268            or SA_RESTART is set.  Restart the interrupted call.  */
 269         {
 270           /* Make sure we have a valid reply port.  The one we were using
 271              may have been destroyed by interruption.  */
 272           __mig_dealloc_reply_port (rcv_name);
 273           m->header.msgh_local_port = rcv_name = __mig_get_reply_port ();
 274           m->header.msgh_bits = msgh_bits;
 275           option = user_option;
 276           timeout = user_timeout;
 277           goto message;
 278         }
 279       err = EINTR;
 280
 281       /* The EINTR return indicates cancellation, so clear the flag.  */
 282       ss->cancel = 0;
 283       break;
 284
 285     case MACH_RCV_PORT_DIED:
 286       /* Server didn't respond to interrupt_operation,
 287          so the signal thread destroyed the reply port.  */
 288       /* FALLTHROUGH */
 289
 290     dead:
 291       err = EIEIO;
 292
 293       /* The EIEIO return indicates cancellation, so clear the flag.  */
 294       ss->cancel = 0;
 295       break;
 296
 297     case MACH_RCV_INTERRUPTED:  /* RPC sent; no reply.  */
 298       option &= ~MACH_SEND_MSG; /* Don't send again.  */
 299     retry_receive:
 300       if (ss->intr_port == MACH_PORT_NULL)
 301         {
 302           /* This signal or cancellation was for us.  We need to wait for
 303              the reply, but not hang forever.  */
 304           option |= MACH_RCV_TIMEOUT;
 305           /* Never decrease the user's timeout.  */
 306           if (!(user_option & MACH_RCV_TIMEOUT)
 307               || timeout > _hurd_interrupted_rpc_timeout)
 308             timeout = _hurd_interrupted_rpc_timeout;
 309         }
 310       else
 311         {
 312           option = user_option;
 313           timeout = user_timeout;
 314         }
 315       goto message;             /* Retry the receive.  */
 316
 317     case MACH_MSG_SUCCESS:
 318       {
 319         /* We got a reply.  Was it EINTR?  */
 320 #ifdef MACH_MSG_TYPE_BIT
 321         static const mach_msg_type_t type_check = {
 322           .msgt_name = MACH_MSG_TYPE_INTEGER_T,
 323           .msgt_size = sizeof (integer_t) * 8,
 324           .msgt_number = 1,
 325           .msgt_inline = TRUE,
 326           .msgt_longform = FALSE,
 327           .msgt_deallocate = FALSE,
 328           .msgt_unused = 0
 329         };
 330 #endif
 331
 332         if (m->reply.RetCode == EINTR
 333             && m->header.msgh_size == sizeof m->reply
 334 #ifdef MACH_MSG_TYPE_BIT
 335             && !BAD_TYPECHECK(&m->check.type, &type_check)
 336 #endif
 337             && !(m->header.msgh_bits & MACH_MSGH_BITS_COMPLEX))
 338           {
 339             /* It is indeed EINTR.  Is the interrupt for us?  */
 340             if (ss->intr_port != MACH_PORT_NULL)
 341               {
 342                 /* Nope; repeat the RPC.
 343                    XXX Resources moved? */
 344
 345                 assert (m->header.msgh_id == msgid + 100);
 346
 347                 /* We know we have a valid reply port, because we just
 348                    received the EINTR reply on it.  Restore it and the
 349                    other fields in the message header needed for send,
 350                    since the header now reflects receipt of the reply.  */
 351                 m->header.msgh_local_port = rcv_name;
 352                 m->header.msgh_remote_port = remote_port;
 353                 m->header.msgh_id = msgid;
 354                 m->header.msgh_bits = msgh_bits;
 355                 /* Restore the two words clobbered by the reply data.  */
 356                 m->request.data = save_data;
 357
 358                 /* Restore the original mach_msg options.
 359                    OPTION may have had MACH_RCV_TIMEOUT added,
 360                    and/or MACH_SEND_MSG removed.  */
 361                 option = user_option;
 362                 timeout = user_timeout;
 363
 364                 /* Now we are ready to repeat the original message send.  */
 365                 goto message;
 366               }
 367             else
 368               /* The EINTR return indicates cancellation,
 369                  so clear the flag.  */
 370               ss->cancel = 0;
 371           }
 372       }
 373       break;
 374
 375     default:                    /* Quiet -Wswitch-enum.  */
 376       break;
 377     }
 378
 379   ss->intr_port = MACH_PORT_NULL;
 380
 381   return err;
 382 }
 383 libc_hidden_def (_hurd_intr_rpc_mach_msg)