Add a new file descriptor type for IPC shared memory objects and use it to

implement shm_open(2) and shm_unlink(2) in the kernel:
- Each shared memory file descriptor is associated with a swap-backed vm
  object which provides the backing store.  Each descriptor starts off with
  a size of zero, but the size can be altered via ftruncate(2).  The shared
  memory file descriptors also support fstat(2).  read(2), write(2),
  ioctl(2), select(2), poll(2), and kevent(2) are not supported on shared
  memory file descriptors.
- shm_open(2) and shm_unlink(2) are now implemented as system calls that
  manage shared memory file descriptors.  The virtual namespace that maps
  pathnames to shared memory file descriptors is implemented as a hash
  table where the hash key is generated via the 32-bit Fowler/Noll/Vo hash
  of the pathname.
- As an extension, the constant 'SHM_ANON' may be specified in place of the
  path argument to shm_open(2).  In this case, an unnamed shared memory
  file descriptor will be created similar to the IPC_PRIVATE key for
  shmget(2).  Note that the shared memory object can still be shared among
  processes by sharing the file descriptor via fork(2) or sendmsg(2), but
  it is unnamed.  This effectively serves to implement the getmemfd() idea
  bandied about the lists several times over the years.
- The backing store for shared memory file descriptors are garbage
  collected when they are not referenced by any open file descriptors or
  the shm_open(2) virtual namespace.

Submitted by:	dillon, peter (previous versions)
Submitted by:	rwatson (I based this on his version)
Reviewed by:	alc (suggested converting getmemfd() to shm_open())

1 files changed, 0 insertions, 72 deletions

diff --git a/lib/libc/gen/posixshm.c b/lib/libc/gen/posixshm.c
deleted file mode 100644
index 05fc1c9..0000000
--- a/lib/libc/gen/posixshm.c
+++ /dev/null
@@ -1,72 +0,0 @@
-/*
- * Copyright 2000 Massachusetts Institute of Technology
- *
- * Permission to use, copy, modify, and distribute this software and
- * its documentation for any purpose and without fee is hereby
- * granted, provided that both the above copyright notice and this
- * permission notice appear in all copies, that both the above
- * copyright notice and this permission notice appear in all
- * supporting documentation, and that the name of M.I.T. not be used
- * in advertising or publicity pertaining to distribution of the
- * software without specific, written prior permission.  M.I.T. makes
- * no representations about the suitability of this software for any
- * purpose.  It is provided "as is" without express or implied
- * warranty.
- *
- * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
- * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
- * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
- * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
- * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
- * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
-
-#include "namespace.h"
-#include <sys/types.h>
-#include <sys/fcntl.h>
-#include <sys/mman.h>
-#include <sys/stat.h>
-
-#include <errno.h>
-#include <unistd.h>
-#include "un-namespace.h"
-
-int
-shm_open(const char *path, int flags, mode_t mode)
-{
-	int fd;
-	struct stat stab;
-
-	if ((flags & O_ACCMODE) == O_WRONLY)
-		return (EINVAL);
-
-	fd = _open(path, flags, mode);
-	if (fd != -1) {
-		if (_fstat(fd, &stab) != 0 || !S_ISREG(stab.st_mode)) {
-			_close(fd);
-			errno = EINVAL;
-			return (-1);
-		}
-
-		if (_fcntl(fd, F_SETFL, (int)FPOSIXSHM) != 0) {
-			_close(fd);
-			return (-1);
-		}
-	}
-	return (fd);
-}
-
-int
-shm_unlink(const char *path)
-{
-	return (unlink(path));
-}