Consolidate arm and mips posix_fadvise implementations

As noted by c1f0601389db64d9, previous posix_fadvise consolidation
broke on mips o32.  As stated in commit message, MIPS o32 only defines
__NR_fadvise64 and it is behaves like __NR_fadvise64_64.

This patches consolidates both ARM and mips o32 version by fixing
the ARM used option (__NR_fadvise64_64 withouth the alignment required
by abi) and added another option, __ASSUME_FADVISE64_AS_64_64,
which is used on mips o32.

When this option is used, posix_fadvise will use __NR_fadvise64_64
behavior (by defining or not __ASSUME_FADVISE64_64_6ARG).  For
mips, if __NR_fadvise64_64 is not defined, __NR_fadvise will be used.

I also updated the posix_fadvise comments to explain better the
different kernel abi used in the supported architectures.

I checked with a mips o32 and verified that posix_fadvise.o is
indeed using 7 argument syscall with the expected argument position.
I also checked on i686-linux-gnu and arm-gnu-eabihf.

	* sysdeps/unix/sysv/linux/arm/posix_fadvise.c: Remove file.
	* sysdeps/unix/sysv/linux/mips/mips32/posix_fadvise.c: Likewise.
	* sysdeps/unix/sysv/linux/mips/kernel-features.h
	(__ASSUME_FADVISE64_AS_64_64): Define.
	* sysdeps/unix/sysv/linux/posix_fadvise.c [__NR_fadvise64]: Add
	!defined __ASSUME_FADVISE64_AS_64_64 to use syscall issue.
	[!__NR_fadvise64 && __ASSUME_FADVISE64_64_6ARG]: Remove
	__ALIGNMENT_ARG usage.
	[!__NR_fadvise64 && !__ASSUME_FADVISE64_64_6ARG]: Define
	__NR_fadvise64_64 if it is not defined.

1 files changed, 0 insertions, 30 deletions

diff --git a/sysdeps/unix/sysv/linux/arm/posix_fadvise.c b/sysdeps/unix/sysv/linux/arm/posix_fadvise.c
deleted file mode 100644
index fafcde5917..0000000000
--- a/sysdeps/unix/sysv/linux/arm/posix_fadvise.c
+++ /dev/null
@@ -1,30 +0,0 @@
-/* Copyright (C) 2005-2017 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 <fcntl.h>
-
-int __posix_fadvise64_l64 (int fd, off64_t offset, off64_t len, int advise);
-
-/* Advice the system about the expected behaviour of the application with
-   respect to the file associated with FD.  */
-
-int
-posix_fadvise (int fd, off_t offset, off_t len, int advise)
-{
-  /* ARM only has a syscall for fadvise64_64.  */
-  return __posix_fadvise64_l64 (fd, offset, len, advise);
-}