sysdeps/unix/sysv/linux/msgrcv.c

   1 /* Copyright (C) 1995-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, August 1995.
   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 <errno.h>
  20 #include <sys/msg.h>
  21 #include <ipc_priv.h>
  22
  23 #include <sysdep-cancel.h>
  24 #include <sys/syscall.h>
  25
  26 /* Kludge to work around Linux' restriction of only up to five
  27    arguments to a system call.  */
  28 struct ipc_kludge
  29   {
  30     void *msgp;
  31     long int msgtyp;
  32   };
  33
  34
  35 ssize_t
  36 __libc_msgrcv (int msqid, void *msgp, size_t msgsz, long int msgtyp,
  37                int msgflg)
  38 {
  39   /* The problem here is that Linux' calling convention only allows up to
  40      fives parameters to a system call.  */
  41   struct ipc_kludge tmp;
  42
  43   tmp.msgp = msgp;
  44   tmp.msgtyp = msgtyp;
  45
  46   if (SINGLE_THREAD_P)
  47     return INLINE_SYSCALL (ipc, 5, IPCOP_msgrcv, msqid, msgsz, msgflg, &tmp);
  48
  49   int oldtype = LIBC_CANCEL_ASYNC ();
  50
  51   ssize_t result = INLINE_SYSCALL (ipc, 5, IPCOP_msgrcv, msqid, msgsz, msgflg,
  52                                    &tmp);
  53
  54    LIBC_CANCEL_RESET (oldtype);
  55
  56   return result;
  57 }
  58 weak_alias (__libc_msgrcv, msgrcv)