posix/shm-directory.c

   1 /* Determine directory for shm/sem files.  Generic POSIX version.
   2    Copyright (C) 2014-2024 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 <unistd.h>
  20
  21 #if _POSIX_MAPPED_FILES
  22
  23 #include <alloc_buffer.h>
  24 #include <shm-directory.h>
  25 #include <string.h>
  26 #include <sys/mman.h>
  27 #include <fcntl.h>
  28 #include <errno.h>
  29
  30 int
  31 __shm_get_name (struct shmdir_name *result, const char *name, bool sem_prefix)
  32 {
  33   struct alloc_buffer buffer;
  34   size_t namelen;
  35
  36   buffer = alloc_buffer_create (result->name, sizeof (result->name));
  37   alloc_buffer_copy_bytes (&buffer, SHMDIR, strlen (SHMDIR));
  38
  39 #if defined (SHM_ANON) && defined (O_TMPFILE)
  40   if (name == SHM_ANON)
  41     {
  42       /* For SHM_ANON, we want shm_open () to pass O_TMPFILE to open (),
  43          with SHMDIR itself as the path.  So, leave it at that.  */
  44       alloc_buffer_add_byte (&buffer, 0);
  45       if (alloc_buffer_has_failed (&buffer))
  46         return -1;
  47       return 0;
  48     }
  49 #endif
  50
  51   while (name[0] == '/')
  52     ++name;
  53   namelen = strlen (name);
  54
  55   if (sem_prefix)
  56     alloc_buffer_copy_bytes (&buffer, "sem.", strlen ("sem."));
  57   alloc_buffer_copy_bytes (&buffer, name, namelen + 1);
  58   if (namelen == 0 || memchr (name, '/', namelen) != NULL)
  59     return EINVAL;
  60   if (alloc_buffer_has_failed (&buffer))
  61     {
  62       if (namelen > NAME_MAX)
  63         return ENAMETOOLONG;
  64       return EINVAL;
  65     }
  66   return 0;
  67 }
  68 libc_hidden_def (__shm_get_name)
  69
  70 #endif