glibc/rt/shm_open.c
Sergey Bugaev a979b72747 hurd: Implement SHM_ANON
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>
2023-02-01 23:36:11 +01:00

59 lines
1.9 KiB
C

/* shm_open -- open a POSIX shared memory object. Generic POSIX file version.
Copyright (C) 2001-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <fcntl.h>
#include <not-cancel.h>
#include <pthread.h>
#include <shlib-compat.h>
#include <shm-directory.h>
#include <unistd.h>
#include <sys/mman.h>
/* Open shared memory object. */
int
__shm_open (const char *name, int oflag, mode_t mode)
{
struct shmdir_name dirname;
if (__shm_get_name (&dirname, name, false) != 0)
{
__set_errno (EINVAL);
return -1;
}
oflag |= O_NOFOLLOW | O_CLOEXEC;
#if defined (SHM_ANON) && defined (O_TMPFILE)
if (name == SHM_ANON)
oflag |= O_TMPFILE;
#endif
int fd = __open64_nocancel (dirname.name, oflag, mode);
if (fd == -1 && __glibc_unlikely (errno == EISDIR))
/* It might be better to fold this error with EINVAL since
directory names are just another example for unsuitable shared
object names and the standard does not mention EISDIR. */
__set_errno (EINVAL);
return fd;
}
versioned_symbol (libc, __shm_open, shm_open, GLIBC_2_34);
#if OTHER_SHLIB_COMPAT (librt, GLIBC_2_2, GLIBC_2_34)
compat_symbol (libc, __shm_open, shm_open, GLIBC_2_2);
#endif