1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <sys/stat.h>
30#include <sys/types.h>
31#include <sys/xattr.h>
32#include <errno.h>
33#include <fcntl.h>
34#include <stdio.h>
35
36extern "C" ssize_t ___fgetxattr(int, const char*, void*, size_t);
37
38ssize_t fgetxattr(int fd, const char *name, void *value, size_t size) {
39  int saved_errno = errno;
40  ssize_t result = ___fgetxattr(fd, name, value, size);
41
42  if ((result != -1) || (errno != EBADF)) {
43    return result;
44  }
45
46  // fd could be an O_PATH file descriptor, and the kernel
47  // may not directly support fgetxattr() on such a file descriptor.
48  // Use /proc/self/fd instead to emulate this support.
49  int fd_flag = fcntl(fd, F_GETFL);
50  if ((fd_flag == -1) || ((fd_flag & O_PATH) == 0)) {
51    errno = EBADF;
52    return -1;
53  }
54
55  char buf[40];
56  snprintf(buf, sizeof(buf), "/proc/self/fd/%d", fd);
57  errno = saved_errno;
58  return getxattr(buf, name, value, size);
59}
60