Consolidate Linux read syscall

This patch consolidates the read Linux syscall implementation on
sysdeps/unix/sysv/linux/read.c.  This leads to a different frame
pointer creation on some architectures:

  * It fixes BZ#21428 on aarch64, since now the returned address
    for the read syscall can be correctly found out by
    backtrace_symbols.

  * It makes tst-backtrace{5,6} fails on powerpc due an issue on
    its custom backtrace implementation.  It is fixed on subsequent
    patch from this set.

Checked on i686-linux-gnu, x86_64-linux-gnu, x86_64-linux-gnux32,
arch64-linux-gnu, arm-linux-gnueabihf, and powerpc64le-linux-gnu.

	[BZ #21428]
	* include/unistd.h (read): Add hidden proto.
	* io/Makefile (CFLAGS-read.c): New rule.
	* nptl/Makefile (CFLAGS-read.c): New rule.
	* sysdeps/unix/sysv/linux/read.c: New file.

ChangeLog

@@ -1,5 +1,11 @@
 2016-05-10  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
+	[BZ #21428]
+	* include/unistd.h (read): Add hidden proto.
+	* io/Makefile (CFLAGS-read.c): New define.
+	* nptl/Makefile (CFLAGS-read.c): Likewise.
+	* sysdeps/unix/sysv/linux/read.c: New file.
+
 	* io/Makefile (CFLAGS-creat.c): New rule.
 	(CFLAGS-creat64.c): Likewise.
 	* sysdeps/unix/sysv/linux/alpha/creat.c: Remove file.

include/unistd.h

@@ -53,6 +53,7 @@ extern ssize_t __libc_pwrite64 (int __fd, const void *__buf, size_t __n,
 				__off64_t __offset) attribute_hidden;
 extern ssize_t __libc_read (int __fd, void *__buf, size_t __n);
 libc_hidden_proto (__libc_read)
+libc_hidden_proto (read)
 extern ssize_t __libc_write (int __fd, const void *__buf, size_t __n);
 libc_hidden_proto (__libc_write)
 extern int __pipe (int __pipedes[2]);

io/Makefile

@@ -100,6 +100,7 @@ CFLAGS-posix_fallocate64.c = -fexceptions
 CFLAGS-fallocate.c = -fexceptions
 CFLAGS-fallocate64.c = -fexceptions
 CFLAGS-sync_file_range.c = -fexceptions
+CFLAGS-read.c = -fexceptions
 
 CFLAGS-test-stat.c = -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE
 CFLAGS-test-lfs.c = -D_LARGEFILE64_SOURCE

nptl/Makefile

@@ -214,6 +214,7 @@ CFLAGS-recvfrom.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-recvmsg.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-sendmsg.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-close.c = -fexceptions -fasynchronous-unwind-tables
+CFLAGS-read.c = -fexceptions -fasynchronous-unwind-tables
 
 CFLAGS-pt-system.c = -fexceptions
 

sysdeps/unix/sysv/linux/read.c

@@ -0,0 +1,33 @@
+/* Linux read syscall implementation.
+   Copyright (C) 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 <unistd.h>
+#include <sysdep-cancel.h>
+
+/* Read NBYTES into BUF from FD.  Return the number read or -1.  */
+ssize_t
+__libc_read (int fd, void *buf, size_t nbytes)
+{
+  return SYSCALL_CANCEL (read, fd, buf, nbytes);
+}
+libc_hidden_def (__libc_read)
+
+libc_hidden_def (__read)
+weak_alias (__libc_read, __read)
+libc_hidden_def (read)
+weak_alias (__libc_read, read)