tunables, aarch64: New tunable to override cpu

Add a new tunable (glibc.tune.cpu) to override CPU identification on
aarch64.  This is useful in two cases: one where it is desirable to
pretend to be another CPU for purposes of testing or because routines
written for that CPU are beneficial for specific workloads and second
where the underlying kernel does not support emulation of MRS to get
the MIDR of the CPU.

	* elf/dl-tunables.h (tunable_is_name): Move from...
	* elf/dl-tunables.c (is_name): ... here.
	(parse_tunables, __tunables_init): Adjust.
	* manual/tunables.texi: Document glibc.tune.cpu.
	* sysdeps/aarch64/dl-tunables.list: New file.
	* sysdeps/unix/sysv/linux/aarch64/cpu-features.c (struct
	cpu_list): New type.
	(cpu_list): New list of CPU names and their MIDR.
	(get_midr_from_mcpu): New function.
	(init_cpu_features): Override MIDR if necessary.

1 files changed, 25 insertions, 0 deletions

diff --git a/sysdeps/aarch64/dl-tunables.list b/sysdeps/aarch64/dl-tunables.list
new file mode 100644
index 0000000000..b1da2bfdfe
--- /dev/null
+++ b/sysdeps/aarch64/dl-tunables.list
@@ -0,0 +1,25 @@
+# aarch64 specific tunables.
+# 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/>.
+
+glibc {
+  tune {
+    cpu {
+      type: STRING
+    }
+  }
+}