AArch64: Add MTE CPU feature check support

This patch is a preparation for the next patches implementing MTE. It just adds
a HWCAP2 constant for MTE, creates a new generic arch/aarch64-mte-linux.h file
and includes that file in the source files that will use it.

gdb/ChangeLog:

YYYY-MM-DD  Luis Machado  <luis.machado@linaro.org>

	* Makefile.in (HFILES_NO_SRCDIR): Add arch/aarch64-mte-linux.h.
	* aarch64-linux-nat.c: Include arch/aarch64-mte-linux.h.
	* aarch64-linux-tdep.c: Likewise
	* arch/aarch64-mte-linux.h: New file.

gdbserver/ChangeLog:

YYYY-MM-DD  Luis Machado  <luis.machado@linaro.org>

	* linux-aarch64-low.cc: Include arch/aarch64-mte-linux.h.

gdb/Makefile.in

@@ -1444,6 +1444,7 @@ HFILES_NO_SRCDIR = \
 	arch/aarch32.h \
 	arch/aarch64.h \
 	arch/aarch64-insn.h \
+	arch/aarch64-mte-linux.h \
 	arch/arc.h \
 	arch/arm.h \
 	arch/i386.h \

gdb/aarch64-linux-nat.c

@@ -50,6 +50,8 @@
 #include "gdb_proc_service.h"
 #include "arch-utils.h"
 
+#include "arch/aarch64-mte-linux.h"
+
 #ifndef TRAP_HWBKPT
 #define TRAP_HWBKPT 0x0004
 #endif

gdb/aarch64-linux-tdep.c

@@ -44,6 +44,8 @@
 #include "record-full.h"
 #include "linux-record.h"
 
+#include "arch/aarch64-mte-linux.h"
+
 /* Signal frame handling.
 
       +------------+  ^

gdb/arch/aarch64-mte-linux.h

@@ -0,0 +1,28 @@
+/* Common Linux target-dependent definitions for AArch64 MTE
+
+   Copyright (C) 2020 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef ARCH_AARCH64_LINUX_H
+#define ARCH_AARCH64_LINUX_H
+
+/* Feature check for Memory Tagging Extension.  */
+#ifndef HWCAP2_MTE
+#define HWCAP2_MTE  (1 << 18)
+#endif
+
+#endif /* ARCH_AARCH64_LINUX_H */

gdbserver/linux-aarch64-low.cc

@@ -40,6 +40,7 @@
 
 #include "gdb_proc_service.h"
 #include "arch/aarch64.h"
+#include "arch/aarch64-mte-linux.h"
 #include "linux-aarch32-tdesc.h"
 #include "linux-aarch64-tdesc.h"
 #include "nat/aarch64-sve-linux-ptrace.h"