linux: Move posix dir implementations to Linux

This generic implementation already expects a getdents API which
is Linux specific.  It also allows simplify it by assuming
_DIRENT_HAVE_D_RECLEN and _DIRENT_HAVE_D_OFF support.

The readdir are also expanded on each required implementation,
futher fixes and improvements will make parametrize the
implementation more complex.

Checked on x86_64-linux-gnu, i686-linux-gnu, and with a build
for all affected ABIs.

1 files changed, 52 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/fdopendir.c b/sysdeps/unix/sysv/linux/fdopendir.c
new file mode 100644
index 0000000000..e424fbdaa2
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/fdopendir.c
@@ -0,0 +1,52 @@
+/* Copyright (C) 2005-2020 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stddef.h>
+#include <sys/stat.h>
+
+#include <not-cancel.h>
+
+
+DIR *
+__fdopendir (int fd)
+{
+  struct stat64 statbuf;
+
+  if (__builtin_expect (__fstat64 (fd, &statbuf), 0) < 0)
+    return NULL;
+  if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode)))
+    {
+      __set_errno (ENOTDIR);
+      return NULL;
+    }
+
+  /* Make sure the descriptor allows for reading.  */
+  int flags = __fcntl64_nocancel (fd, F_GETFL);
+  if (__glibc_unlikely (flags == -1))
+    return NULL;
+  if (__glibc_unlikely ((flags & O_ACCMODE) == O_WRONLY))
+    {
+      __set_errno (EINVAL);
+      return NULL;
+    }
+
+  return __alloc_dir (fd, false, flags, &statbuf);
+}
+weak_alias (__fdopendir, fdopendir)