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a979b72747
This adds a special SHM_ANON value that can be passed into shm_open () in place of a name. When called in this way, shm_open () will create a new anonymous shared memory file. The file will be created in the same way that other shared memory files are created (i.e., under /dev/shm/), except that it is not given a name and therefore cannot be reached from the file system, nor by other calls to shm_open (). This is accomplished by utilizing O_TMPFILE. This is intended to be compatible with FreeBSD's API of the same name. Signed-off-by: Sergey Bugaev <bugaevc@gmail.com> Message-Id: <20230130125216.6254-4-bugaevc@gmail.com>
65 lines
2.0 KiB
C
65 lines
2.0 KiB
C
/* Determine directory for shm/sem files. Generic POSIX version.
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Copyright (C) 2014-2023 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <unistd.h>
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#if _POSIX_MAPPED_FILES
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#include <alloc_buffer.h>
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#include <shm-directory.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <fcntl.h>
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int
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__shm_get_name (struct shmdir_name *result, const char *name, bool sem_prefix)
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{
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struct alloc_buffer buffer;
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size_t namelen;
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buffer = alloc_buffer_create (result->name, sizeof (result->name));
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alloc_buffer_copy_bytes (&buffer, SHMDIR, strlen (SHMDIR));
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#if defined (SHM_ANON) && defined (O_TMPFILE)
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if (name == SHM_ANON)
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{
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/* For SHM_ANON, we want shm_open () to pass O_TMPFILE to open (),
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with SHMDIR itself as the path. So, leave it at that. */
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alloc_buffer_add_byte (&buffer, 0);
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if (alloc_buffer_has_failed (&buffer))
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return -1;
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return 0;
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}
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#endif
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while (name[0] == '/')
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++name;
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namelen = strlen (name);
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if (sem_prefix)
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alloc_buffer_copy_bytes (&buffer, "sem.", strlen ("sem."));
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alloc_buffer_copy_bytes (&buffer, name, namelen + 1);
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if (namelen == 0 || memchr (name, '/', namelen) != NULL
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|| alloc_buffer_has_failed (&buffer))
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return -1;
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return 0;
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}
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libc_hidden_def (__shm_get_name)
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#endif
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