[PATCH v2 4/5] gdb: LoongArch: Add initial native Linux support

[Tiezhu Yang <yangtiezhu@loongson.cn>]

This commit adds initial native Linux support for LoongArch.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 gdb/loongarch-linux-nat.c | 184 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 184 insertions(+)
 create mode 100644 gdb/loongarch-linux-nat.c

diff --git a/gdb/loongarch-linux-nat.c b/gdb/loongarch-linux-nat.c
new file mode 100644
index 00000000000..edc3d697d7b
--- /dev/null
+++ b/gdb/loongarch-linux-nat.c
@@ -0,0 +1,184 @@
+/* Native-dependent code for GNU/Linux on LoongArch processors.
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   Contributed by Loongson Ltd.
+
+   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 "defs.h"
+#include "elf/common.h"
+#include "gregset.h"
+#include "inferior.h"
+#include "linux-nat-trad.h"
+#include "loongarch-tdep.h"
+#include "nat/gdb_ptrace.h"
+#include "target-descriptions.h"
+
+#include <asm/ptrace.h>
+
+/* LoongArch Linux native additions to the default Linux support.  */
+
+class loongarch_linux_nat_target final : public linux_nat_trad_target
+{
+public:
+  /* Add our register access methods.  */
+  void fetch_registers (struct regcache *, int) override;
+  void store_registers (struct regcache *, int) override;
+
+protected:
+  /* Override linux_nat_trad_target methods.  */
+  CORE_ADDR register_u_offset (struct gdbarch *gdbarch, int regno,
+                               int store_p) override;
+};
+
+/* Fill GDB's register array with the general-purpose, pc and badv
+   register values from the current thread.  */
+
+static void
+fetch_gregs_from_thread (struct regcache *regcache, int regno, pid_t tid)
+{
+  loongarch_gdbarch_tdep *tdep
+    = (loongarch_gdbarch_tdep *) gdbarch_tdep (regcache->arch ());
+  auto regs = tdep->regs;
+  elf_gregset_t regset;
+
+  if (regno == -1 || (regs.r <= regno && regno < regs.r + 32)
+      || regs.pc == regno || regs.badv == regno)
+  {
+    struct iovec iov;
+
+    iov.iov_base = &regset;
+    iov.iov_len = sizeof (regset);
+
+    if (ptrace (PTRACE_GETREGSET, tid, NT_PRSTATUS, (long) &iov) < 0)
+      perror_with_name (_("Couldn't get NT_PRSTATUS registers"));
+    else
+      loongarch_gregset.supply_regset (nullptr, regcache, regno,
+				       &regset, sizeof (regset));
+  }
+}
+
+/* Store to the current thread the valid general-purpose, pc and badv
+   register values in the GDB's register array.  */
+
+static void
+store_gregs_to_thread (struct regcache *regcache, int regno, pid_t tid)
+{
+  loongarch_gdbarch_tdep *tdep
+    = (loongarch_gdbarch_tdep *) gdbarch_tdep (regcache->arch ());
+  auto regs = tdep->regs;
+  elf_gregset_t regset;
+
+  if (regno == -1 || (regs.r <= regno && regno < regs.r + 32)
+      || regs.pc == regno || regs.badv == regno)
+  {
+    struct iovec iov;
+
+    iov.iov_base = &regset;
+    iov.iov_len = sizeof (regset);
+
+    if (ptrace (PTRACE_GETREGSET, tid, NT_PRSTATUS, (long) &iov) < 0)
+      perror_with_name (_("Couldn't get NT_PRSTATUS registers"));
+    else
+      {
+	loongarch_gregset.collect_regset (nullptr, regcache, regno,
+					  &regset, sizeof (regset));
+	if (ptrace (PTRACE_SETREGSET, tid, NT_PRSTATUS, (long) &iov) < 0)
+	  perror_with_name (_("Couldn't set NT_PRSTATUS registers"));
+      }
+  }
+}
+
+/* Implement the "fetch_registers" target_ops method.  */
+
+void
+loongarch_linux_nat_target::fetch_registers (struct regcache *regcache,
+					     int regno)
+{
+  pid_t tid = get_ptrace_pid (regcache->ptid ());
+
+  fetch_gregs_from_thread(regcache, regno, tid);
+}
+
+/* Implement the "store_registers" target_ops method.  */
+
+void
+loongarch_linux_nat_target::store_registers (struct regcache *regcache,
+					     int regno)
+{
+  pid_t tid = get_ptrace_pid (regcache->ptid ());
+
+  store_gregs_to_thread (regcache, regno, tid);
+}
+
+/* Return the address in the core dump or inferior of register REGNO.  */
+
+CORE_ADDR
+loongarch_linux_nat_target::register_u_offset (struct gdbarch *gdbarch,
+					       int regno, int store_p)
+{
+  loongarch_gdbarch_tdep *tdep
+    = (loongarch_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  auto regs = tdep->regs;
+
+  /* According to <asm/ptrace.h> */
+  if (0 <= regs.r && regs.r <= regno && regno < regs.r + GPR_NUM)
+    return GPR_BASE + regno - regs.r;
+  else if (regs.pc == regno)
+    return PC;
+  else
+    return -1;
+}
+
+static loongarch_linux_nat_target the_loongarch_linux_nat_target;
+
+/* Wrapper functions.  These are only used by libthread_db.  */
+
+void
+supply_gregset (struct regcache *regcache, const gdb_gregset_t *gregset)
+{
+  loongarch_gregset.supply_regset (nullptr, regcache, -1, gregset,
+				   sizeof (gdb_gregset_t));
+}
+
+void
+fill_gregset (const struct regcache *regcache, gdb_gregset_t *gregset,
+	      int regno)
+{
+  loongarch_gregset.collect_regset (nullptr, regcache, regno, gregset,
+				    sizeof (gdb_gregset_t));
+}
+
+void
+supply_fpregset (struct regcache *regcache, const gdb_fpregset_t *fpregset)
+{
+}
+
+void
+fill_fpregset (const struct regcache *regcache, gdb_fpregset_t *fpregset,
+	       int regno)
+{
+}
+
+/* Initialize LoongArch Linux native support.  */
+
+void _initialize_loongarch_linux_nat ();
+void
+_initialize_loongarch_linux_nat ()
+{
+  linux_target = &the_loongarch_linux_nat_target;
+  add_inf_child_target (&the_loongarch_linux_nat_target);
+}
-- 
2.27.0