xref: /xsrc/external/mit/libxshmfence/dist/src/xshmfence_alloc.c

/*
 * Copyright © 2013 Keith Packard
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include "xshmfenceint.h"

#if !HAVE_MEMFD_CREATE
#if HAVE_DECL___NR_MEMFD_CREATE
#include <asm/unistd.h>
static int memfd_create(const char *name,
			    unsigned int flags)
{
	return syscall(__NR_memfd_create, name, flags);
}
#define HAVE_MEMFD_CREATE	1
#endif
#endif

#if HAVE_MEMFD_CREATE

/* Get defines for the memfd_create syscall, using the
 * header if available, or just defining the constants otherwise
 */

#if HAVE_MEMFD_H
#include <sys/memfd.h>
#else
/* flags for memfd_create(2) (unsigned int) */
#define MFD_CLOEXEC		0x0001U
#define MFD_ALLOW_SEALING	0x0002U
#endif

#endif

/**
 * xshmfence_alloc_shm:
 *
 * Allocates a shared memory object large enough to hold a single
 * fence.
 *
 * Return value: the file descriptor of the object, or -1 on failure
 * (in which case, errno will be set as appropriate).
 **/
int
xshmfence_alloc_shm(void)
{
	char	template[] = SHMDIR "/shmfd-XXXXXX";
	int	fd;

#if HAVE_MEMFD_CREATE
	fd = memfd_create("xshmfence", MFD_CLOEXEC|MFD_ALLOW_SEALING);
	if (fd < 0)
#endif
	{
#ifdef O_TMPFILE
		fd = open(SHMDIR, O_TMPFILE|O_RDWR|O_CLOEXEC|O_EXCL, 0666);
		if (fd < 0)
#endif
		{
			fd = mkstemp(template);
			if (fd < 0)
				return fd;
			unlink(template);
		}
	}
	if (ftruncate(fd, sizeof (struct xshmfence)) < 0) {
            close(fd);
            return -1;
        }
        xshmfence_init(fd);
	return fd;
}

/**
 * xshmfence_map_shm:
 *
 * Map a shared memory fence referenced by @fd.
 *
 * Return value: the fence or NULL (in which case, errno will be set
 * as appropriate).
 **/
struct xshmfence *
xshmfence_map_shm(int fd)
{
	struct xshmfence *addr;
	addr = mmap (NULL, sizeof (struct xshmfence) , PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	if (addr == MAP_FAILED) {
		close (fd);
		return 0;
	}
#ifdef HAVE_SEMAPHORE
	xshmfence_open_semaphore(addr);
#endif
	return addr;
}

/**
 * xshmfence_unmap_shm:
 *
 * Unap a shared memory fence @f.
 **/
void
xshmfence_unmap_shm(struct xshmfence *f)
{
#ifdef HAVE_SEMAPHORE
	xshmfence_close_semaphore(f);
#endif
        munmap(f, sizeof (struct xshmfence));
}