os-compatibility.c

/*
 * Copyright © 2012 Collabora, Ltd.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#include "os-compatibility.h"

int
os_fd_set_cloexec(int fd)
{
    long flags;

    if (fd == -1)
        return -1;

    flags = fcntl(fd, F_GETFD);
    if (flags == -1)
        return -1;

    if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1)
        return -1;

    return 0;
}

static int
set_cloexec_or_close(int fd)
{
    if (os_fd_set_cloexec(fd) != 0) {
        close(fd);
        return -1;
    }
    return fd;
}

int
os_socketpair_cloexec(int domain, int type, int protocol, int *sv)
{
    int ret;

#ifdef SOCK_CLOEXEC
    ret = socketpair(domain, type | SOCK_CLOEXEC, protocol, sv);
    if (ret == 0 || errno != EINVAL)
        return ret;
#endif

    ret = socketpair(domain, type, protocol, sv);
    if (ret < 0)
        return ret;

    sv[0] = set_cloexec_or_close(sv[0]);
    sv[1] = set_cloexec_or_close(sv[1]);

    if (sv[0] != -1 && sv[1] != -1)
        return 0;

    close(sv[0]);
    close(sv[1]);
    return -1;
}

int
os_epoll_create_cloexec(void)
{
    int fd;

#ifdef EPOLL_CLOEXEC
    fd = epoll_create1(EPOLL_CLOEXEC);
    if (fd >= 0)
        return fd;
    if (errno != EINVAL)
        return -1;
#endif

    fd = epoll_create(1);
    return set_cloexec_or_close(fd);
}

static int
create_tmpfile_cloexec(char *tmpname)
{
    int fd;

#ifdef HAVE_MKOSTEMP
    fd = mkostemp(tmpname, O_CLOEXEC);
    if (fd >= 0)
        unlink(tmpname);
#else
    fd = mkstemp(tmpname);
    if (fd >= 0) {
        fd = set_cloexec_or_close(fd);
        unlink(tmpname);
    }
#endif

    return fd;
}

/*
 * Create a new, unique, anonymous file of the given size, and
 * return the file descriptor for it. The file descriptor is set
 * CLOEXEC. The file is immediately suitable for mmap()'ing
 * the given size at offset zero.
 *
 * The file should not have a permanent backing store like a disk,
 * but may have if XDG_RUNTIME_DIR is not properly implemented in OS.
 *
 * The file name is deleted from the file system.
 *
 * The file is suitable for buffer sharing between processes by
 * transmitting the file descriptor over Unix sockets using the
 * SCM_RIGHTS methods.
 *
 * If the C library implements posix_fallocate(), it is used to
 * guarantee that disk space is available for the file at the
 * given size. If disk space is insufficient, errno is set to ENOSPC.
 * If posix_fallocate() is not supported, program may receive
 * SIGBUS on accessing mmap()'ed file contents instead.
 */
int
os_create_anonymous_file(off_t size)
{
    static const char template[] = "/weston-shared-XXXXXX";
    const char *path;
    char *name;
    int fd;
    int ret;

    path = getenv("XDG_RUNTIME_DIR");
    if (!path) {
        errno = ENOENT;
        return -1;
    }

    name = malloc(strlen(path) + sizeof(template));
    if (!name)
        return -1;

    strcpy(name, path);
    strcat(name, template);

    fd = create_tmpfile_cloexec(name);

    free(name);

    if (fd < 0)
        return -1;

#ifdef HAVE_POSIX_FALLOCATE
    do {
        ret = posix_fallocate(fd, 0, size);
    } while (ret == EINTR);
    if (ret != 0) {
        close(fd);
        errno = ret;
        return -1;
    }
#else
    do {
        ret = ftruncate(fd, size);
    } while (ret < 0 && errno == EINTR);
    if (ret < 0) {
        close(fd);
        return -1;
    }
#endif

    return fd;
}

#ifndef MISSING_STRCHRNUL
char *
strchrnul(const char *s, int c)
{
    while (*s && *s != c)
        s++;
    return (char *)s;
}
#endif