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.

1 files changed, 33 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/read.c b/sysdeps/unix/sysv/linux/read.c
new file mode 100644
index 0000000000..2a02c1bae4
--- /dev/null
+++ b/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)