Add O_PATH support for flistxattr()
A continuation of commit 2825f10b7f61558c264231a536cf3affc0d84204.
Add O_PATH compatibility support for flistxattr(). This allows
a process to list out all the extended attributes associated with
O_PATH file descriptors.
Change-Id: Ie2285ac7ad2e4eac427ddba6c2d182d41b130f75
diff --git a/libc/bionic/flistxattr.cpp b/libc/bionic/flistxattr.cpp
new file mode 100644
index 0000000..05a96d2
--- /dev/null
+++ b/libc/bionic/flistxattr.cpp
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS 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/stat.h>
+#include <sys/types.h>
+#include <sys/xattr.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+
+extern "C" ssize_t ___flistxattr(int, char*, size_t);
+
+ssize_t flistxattr(int fd, char *list, size_t size) {
+ int saved_errno = errno;
+ ssize_t result = ___flistxattr(fd, list, size);
+
+ if ((result != -1) || (errno != EBADF)) {
+ return result;
+ }
+
+ // fd could be an O_PATH file descriptor, and the kernel
+ // may not directly support fgetxattr() on such a file descriptor.
+ // Use /proc/self/fd instead to emulate this support.
+ int fd_flag = fcntl(fd, F_GETFL);
+ if ((fd_flag == -1) || ((fd_flag & O_PATH) == 0)) {
+ errno = EBADF;
+ return -1;
+ }
+
+ char buf[40];
+ snprintf(buf, sizeof(buf), "/proc/self/fd/%d", fd);
+ errno = saved_errno;
+ return listxattr(buf, list, size);
+}