Add the statx function

io/statx_generic.c

@@ -0,0 +1,81 @@
+/* Generic implementation of statx based on fstatat64.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+
+static inline struct statx_timestamp
+statx_convert_timestamp (struct timespec tv)
+{
+  return (struct statx_timestamp) { tv.tv_sec, tv.tv_nsec };
+}
+
+/* Approximate emulation of statx.  This will always fill in
+   POSIX-mandated attributes even if the underlying file system does
+   not actually support it (for example, GID and UID on file systems
+   without UNIX-style permissions).  */
+static __attribute__ ((unused)) int
+statx_generic (int fd, const char *path, int flags,
+               unsigned int mask, struct statx *buf)
+{
+  /* Flags which need to be cleared before passing them to
+     fstatat64.  */
+  static const int clear_flags = AT_STATX_SYNC_AS_STAT;
+
+    /* Flags supported by our emulation.  */
+  static const int supported_flags
+    = AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW | clear_flags;
+
+  if (__glibc_unlikely ((flags & ~supported_flags) != 0))
+    {
+      __set_errno (EINVAL);
+      return -1;
+    }
+
+  struct stat64 st;
+  int ret = __fstatat64 (fd, path, &st, flags & ~clear_flags);
+  if (ret != 0)
+    return ret;
+
+  /* The interface is defined in such a way that unused (padding)
+     fields have to be cleared.  STATX_BASIC_STATS corresponds to the
+     data which is available via fstatat64.  */
+  *buf = (struct statx)
+    {
+      .stx_mask = STATX_BASIC_STATS,
+      .stx_blksize = st.st_blksize,
+      .stx_nlink = st.st_nlink,
+      .stx_uid = st.st_uid,
+      .stx_gid = st.st_gid,
+      .stx_mode = st.st_mode,
+      .stx_ino = st.st_ino,
+      .stx_size = st.st_size,
+      .stx_blocks = st.st_blocks,
+      .stx_atime = statx_convert_timestamp (st.st_atim),
+      .stx_ctime = statx_convert_timestamp (st.st_ctim),
+      .stx_mtime = statx_convert_timestamp (st.st_mtim),
+      .stx_rdev_major = major (st.st_rdev),
+      .stx_rdev_minor = minor (st.st_rdev),
+      .stx_dev_major = major (st.st_dev),
+      .stx_dev_minor = minor (st.st_dev),
+    };
+
+  return 0;
+}