gdbserver/csky add csky gdbserver support

Add new files:
  gdb/arch/csky.c
  gdb/arch/csky.h
  gdb/features/cskyv2-linux.c
  gdbserver/linux-csky-low.cc

1. In gdb/arch/csky.c file, add function "csky_create_target_description()"
for csky_target::low_arch_setup(). later, it can be used for csky native gdb.

2. In gdb/features/cskyv2-linux.c file, create target_tdesc for csky, include
gprs, pc, hi, lo, float, vector and float control registers.

3. In gdbserver/linux-csky-low.cc file, using PTRACE_GET/SET_RGESET to
get/set registers. The main data structures in asm/ptrace.h are:
struct pt_regs {
    unsigned long   tls;
    unsigned long   lr;
    unsigned long   pc;
    unsigned long   sr;
    unsigned long   usp;

    /*
     * a0, a1, a2, a3:
     * r0, r1, r2, r3
     */
    unsigned long   orig_a0;
    unsigned long   a0;
    unsigned long   a1;
    unsigned long   a2;
    unsigned long   a3;

    /*
     * r4 ~ r13
     */
    unsigned long   regs[10];

    /* r16 ~ r30 */
    unsigned long   exregs[15];

    unsigned long   rhi;
    unsigned long   rlo;
    unsigned long   dcsr;
};

struct user_fp {
    unsigned long   vr[96];
    unsigned long   fcr;
    unsigned long   fesr;
    unsigned long   fid;
    unsigned long   reserved;
};

2 files changed, 67 insertions, 0 deletions

diff --git a/gdb/arch/csky.c b/gdb/arch/csky.c
new file mode 100644
index 0000000..8877967
--- /dev/null
+++ b/gdb/arch/csky.c
@@ -0,0 +1,38 @@
+/* Copyright (C) 2022 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 "gdbsupport/common-defs.h"
+#include "csky.h"
+#include <stdlib.h>
+
+#include "../features/cskyv2-linux.c"
+
+target_desc_up
+csky_create_target_description (void)
+{
+  /* Now we should create a new target description.  */
+  target_desc_up tdesc = allocate_target_description ();
+
+#ifndef IN_PROCESS_AGENT
+  std::string arch_name = "csky";
+  set_tdesc_architecture (tdesc.get (), arch_name.c_str ());
+#endif
+
+  create_feature_cskyv2_linux (tdesc.get ());
+
+  return tdesc;
+}
diff --git a/gdb/arch/csky.h b/gdb/arch/csky.h
new file mode 100644
index 0000000..1c147a9
--- /dev/null
+++ b/gdb/arch/csky.h
@@ -0,0 +1,29 @@
+/* Common target-dependent functionality for CSKY
+
+   Copyright (C) 2022 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_CSKY_H
+#define ARCH_CSKy_H
+
+#include "gdbsupport/tdesc.h"
+
+/* Used for gdbserver.  */
+
+target_desc_up csky_create_target_description (void);
+
+#endif /* ARCH_CSKY_H */