linux: Add {f}stat{at} y2038 support

A new struct __stat{64}_t64 type is added with the required
__timespec64 time definition.  Only LFS is added, 64-bit time with
32-bit offsets is not supposed to be supported (no existing glibc
configuration supports such a combination).  It is done with an extra
__NR_statx call plus a conversion to the new __stat{64}_t64 type.
The statx call is done only for 32-bit time_t ABIs.

Internally some extra routines to copy from/to struct stat{64}
to struct __stat{64} used on multiple implementations (stat, fstat,
lstat, and fstatat) are added on a extra implementation
(stat_t64_cp.c).  Alse some extra routines to copy from statx to
__stat{64} is added on statx_cp.c.

Checked with a build for all affected ABIs. I also checked on x86_64,
i686, powerpc, powerpc64le, sparcv9, sparc64, s390, and s390x.

Reviewed-by: Lukasz Majewski <lukma@denx.de>

sysdeps/unix/sysv/linux/struct_stat_time64.h

@@ -0,0 +1,85 @@
+/* Struct stat with 64-bit time support.
+   Copyright (C) 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/>.  */
+
+#ifndef _BITS_STRUCT_STAT_TIME64_H
+#define _BITS_STRUCT_STAT_TIME64_H 1
+
+#if __TIMESIZE == 64
+# define __stat64_t64 stat64
+#else
+# ifdef __USE_LARGEFILE64
+#  include <endian.h>
+
+/* The definition should be equal to the 'struct __timespec64' internal
+   layout.  */
+#  if BYTE_ORDER == BIG_ENDIAN
+#   define __fieldts64(name) 					\
+     __time64_t name; __int32_t :32; __int32_t name ## nsec
+#  else
+#   define __fieldts64(name)					\
+     __time64_t name; __int32_t name ## nsec; __int32_t :32
+#  endif
+
+/* Workaround for the definition from struct_stat.h  */
+#  undef st_atime
+#  undef st_mtime
+#  undef st_ctime
+
+struct __stat64_t64
+  {
+    __dev_t st_dev;			/* Device.  */
+    __ino64_t st_ino;			/* file serial number.	*/
+    __mode_t st_mode;			/* File mode.  */
+    __nlink_t st_nlink;			/* Link count.  */
+    __uid_t st_uid;			/* User ID of the file's owner.	*/
+    __gid_t st_gid;			/* Group ID of the file's group.*/
+    __dev_t st_rdev;			/* Device number, if device.  */
+    __off64_t st_size;			/* Size of file, in bytes.  */
+    __blksize_t st_blksize;		/* Optimal block size for I/O.  */
+    __blkcnt64_t st_blocks;		/* Number 512-byte blocks allocated. */
+#   ifdef __USE_XOPEN2K8
+    /* Nanosecond resolution timestamps are stored in a format
+       equivalent to 'struct timespec'.  This is the type used
+       whenever possible but the Unix namespace rules do not allow the
+       identifier 'timespec' to appear in the <sys/stat.h> header.
+       Therefore we have to handle the use of this header in strictly
+       standard-compliant sources special.  */
+    struct __timespec64 st_atim;	/* Time of last access.  */
+    struct __timespec64 st_mtim;	/* Time of last modification.  */
+    struct __timespec64 st_ctim;	/* Time of last status change.  */
+#    define st_atime st_atim.tv_sec	/* Backward compatibility.  */
+#    define st_mtime st_mtim.tv_sec
+#    define st_ctime st_ctim.tv_sec
+#   else
+    __fieldts64 (st_atime);
+    __fieldts64 (st_mtime);
+    __fieldts64 (st_ctime);
+#   endif /* __USE_XOPEN2K8  */
+  };
+
+#   define _STATBUF_ST_BLKSIZE
+#   define _STATBUF_ST_RDEV
+#   define _STATBUF_ST_NSEC
+
+#   undef __fieldts64
+
+#  endif /* __USE_LARGEFILE64  */
+
+# endif /* __TIMESIZE == 64  */
+
+#endif /* _BITS_STRUCT_STAT_TIME64_H  */