sysdeps/posix/shm_open.c

   1 /* shm_open -- open a POSIX shared memory object.  Generic POSIX file version.
   2    Copyright (C) 2001,2002,2005 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 <unistd.h>
  20
  21 #if ! _POSIX_MAPPED_FILES
  22 #include <rt/shm_open.c>
  23
  24 #else
  25
  26 #include <errno.h>
  27 #include <sys/mman.h>
  28 #include <fcntl.h>
  29 #include <string.h>
  30 #include <stdlib.h>
  31 #include <paths.h>
  32
  33 #define SHMDIR  (_PATH_DEV "shm/")
  34
  35 /* Open shared memory object.  */
  36 int
  37 shm_open (const char *name, int oflag, mode_t mode)
  38 {
  39   size_t namelen;
  40   char *fname;
  41   int fd;
  42
  43   /* Construct the filename.  */
  44   while (name[0] == '/')
  45     ++name;
  46
  47   if (name[0] == '\0')
  48     {
  49       /* The name "/" is not supported.  */
  50       __set_errno (EINVAL);
  51       return -1;
  52     }
  53
  54   namelen = strlen (name);
  55   fname = (char *) __alloca (sizeof SHMDIR - 1 + namelen + 1);
  56   __mempcpy (__mempcpy (fname, SHMDIR, sizeof SHMDIR - 1),
  57              name, namelen + 1);
  58
  59   fd = open (name, oflag, mode);
  60   if (fd != -1)
  61     {
  62       /* We got a descriptor.  Now set the FD_CLOEXEC bit.  */
  63       int flags = fcntl (fd, F_GETFD, 0);
  64
  65       if (__builtin_expect (flags, 0) != -1)
  66         {
  67           flags |= FD_CLOEXEC;
  68           flags = fcntl (fd, F_SETFD, flags);
  69         }
  70
  71       if (flags == -1)
  72         {
  73           /* Something went wrong.  We cannot return the descriptor.  */
  74           int save_errno = errno;
  75           close (fd);
  76           fd = -1;
  77           __set_errno (save_errno);
  78         }
  79     }
  80
  81   return fd;
  82 }
  83
  84 #endif