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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <unistd.h>
  21
  22 #if ! _POSIX_MAPPED_FILES
  23 #include <rt/shm_open.c>
  24
  25 #else
  26
  27 #include <errno.h>
  28 #include <sys/mman.h>
  29 #include <fcntl.h>
  30 #include <string.h>
  31 #include <stdlib.h>
  32 #include <paths.h>
  33
  34 #define SHMDIR  (_PATH_DEV "shm/")
  35
  36 /* Open shared memory object.  */
  37 int
  38 shm_open (const char *name, int oflag, mode_t mode)
  39 {
  40   size_t namelen;
  41   char *fname;
  42   int fd;
  43
  44   /* Construct the filename.  */
  45   while (name[0] == '/')
  46     ++name;
  47
  48   if (name[0] == '\0')
  49     {
  50       /* The name "/" is not supported.  */
  51       __set_errno (EINVAL);
  52       return -1;
  53     }
  54
  55   namelen = strlen (name);
  56   fname = (char *) __alloca (sizeof SHMDIR - 1 + namelen + 1);
  57   __mempcpy (__mempcpy (fname, SHMDIR, sizeof SHMDIR - 1),
  58              name, namelen + 1);
  59
  60   fd = open (name, oflag, mode);
  61   if (fd != -1)
  62     {
  63       /* We got a descriptor.  Now set the FD_CLOEXEC bit.  */
  64       int flags = fcntl (fd, F_GETFD, 0);
  65
  66       if (__builtin_expect (flags, 0) != -1)
  67         {
  68           flags |= FD_CLOEXEC;
  69           flags = fcntl (fd, F_SETFD, flags);
  70         }
  71
  72       if (flags == -1)
  73         {
  74           /* Something went wrong.  We cannot return the descriptor.  */
  75           int save_errno = errno;
  76           close (fd);
  77           fd = -1;
  78           __set_errno (save_errno);
  79         }
  80     }
  81
  82   return fd;
  83 }
  84
  85 #endif