sysdeps/posix/shm_open.c

   1 /* shm_open -- open a POSIX shared memory object.  Generic POSIX file version.
   2    Copyright (C) 2001-2017 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
  23 # include <rt/shm_open.c>
  24
  25 #else
  26
  27 # include <fcntl.h>
  28 # include <shm-directory.h>
  29
  30
  31 /* Open shared memory object.  */
  32 int
  33 shm_open (const char *name, int oflag, mode_t mode)
  34 {
  35   SHM_GET_NAME (EINVAL, -1, "");
  36
  37 # ifdef O_NOFOLLOW
  38   oflag |= O_NOFOLLOW;
  39 # endif
  40 # ifdef O_CLOEXEC
  41   oflag |= O_CLOEXEC;
  42 # endif
  43
  44   /* Disable asynchronous cancellation.  */
  45   int state;
  46   pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &state);
  47
  48   int fd = open (shm_name, oflag, mode);
  49   if (fd == -1 && __glibc_unlikely (errno == EISDIR))
  50     /* It might be better to fold this error with EINVAL since
  51        directory names are just another example for unsuitable shared
  52        object names and the standard does not mention EISDIR.  */
  53     __set_errno (EINVAL);
  54
  55 # ifndef O_CLOEXEC
  56   if (fd != -1)
  57     {
  58       /* We got a descriptor.  Now set the FD_CLOEXEC bit.  */
  59       int flags = fcntl (fd, F_GETFD, 0);
  60
  61       if (__glibc_likely (flags != -1))
  62         {
  63           flags |= FD_CLOEXEC;
  64           flags = fcntl (fd, F_SETFD, flags);
  65         }
  66
  67       if (flags == -1)
  68         {
  69           /* Something went wrong.  We cannot return the descriptor.  */
  70           int save_errno = errno;
  71           close (fd);
  72           fd = -1;
  73           __set_errno (save_errno);
  74         }
  75     }
  76 # endif
  77
  78   pthread_setcancelstate (state, NULL);
  79
  80   return fd;
  81 }
  82
  83 #endif  /* _POSIX_MAPPED_FILES */