Function for reading the Aarch64 SVE vector length

Returns 0 for systems without SVE support.

Note the defines taken from Linux kernel headers
in aarch64-sve-linux-ptrace.h.

gdb/
	* Makefile.in: Add new header.
	* gdb/arch/aarch64.h (sve_vg_from_vl): New macro.
	(sve_vl_from_vg): Likewise.
	(sve_vq_from_vl): Likewise.
	(sve_vl_from_vq): Likewise.
	(sve_vq_from_vg): Likewise.
	(sve_vg_from_vq): Likewise.
	* configure.nat: Add new c file.
	* nat/aarch64-sve-linux-ptrace.c: New file.
	* nat/aarch64-sve-linux-ptrace.h: New file.

gdbserver/
	* configure.srv: Add new c/h file.

1 files changed, 58 insertions, 0 deletions

diff --git a/gdb/nat/aarch64-sve-linux-ptrace.c b/gdb/nat/aarch64-sve-linux-ptrace.c
new file mode 100644
index 0000000..3a1dbae
--- /dev/null
+++ b/gdb/nat/aarch64-sve-linux-ptrace.c
@@ -0,0 +1,58 @@
+/* Common target dependent for AArch64 systems.
+
+   Copyright (C) 2018 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/>.  */
+
+#include <sys/utsname.h>
+#include <sys/uio.h>
+#include "common-defs.h"
+#include "elf/external.h"
+#include "elf/common.h"
+#include "aarch64-sve-linux-ptrace.h"
+#include "arch/aarch64.h"
+
+/* See nat/aarch64-sve-linux-ptrace.h.  */
+
+unsigned long
+aarch64_sve_get_vq (int tid)
+{
+  struct iovec iovec;
+  struct user_sve_header header;
+
+  iovec.iov_len = sizeof (header);
+  iovec.iov_base = &header;
+
+  /* Ptrace gives the vector length in bytes.  Convert it to VQ, the number of
+     128bit chunks in a Z register.  We use VQ because 128bits is the minimum
+     a Z register can increase in size.  */
+
+  if (ptrace (PTRACE_GETREGSET, tid, NT_ARM_SVE, &iovec) < 0)
+    {
+      /* SVE is not supported.  */
+      return 0;
+    }
+
+  long vq = sve_vq_from_vl (header.vl);
+
+  if (!sve_vl_valid (header.vl))
+    {
+      warning (_("Invalid SVE state from kernel; SVE disabled."));
+      return 0;
+    }
+
+  return vq;
+}