/* Ravenscar RISC-V target support.

   Copyright (C) 2019-2020 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/>.  */

#include "defs.h"
#include "gdbarch.h"
#include "gdbcore.h"
#include "regcache.h"
#include "riscv-tdep.h"
#include "inferior.h"
#include "ravenscar-thread.h"
#include "riscv-ravenscar-thread.h"

struct riscv_ravenscar_ops : public ravenscar_arch_ops
{
  void fetch_registers (struct regcache *regcache, int regnum) override;
  void store_registers (struct regcache *regcache, int regnum) override;

private:

  /* Return the offset of the register in the context buffer.  */
  int register_offset (struct gdbarch *arch, int regnum);
};

int
riscv_ravenscar_ops::register_offset (struct gdbarch *arch, int regnum)
{
  int offset;
  if (regnum == RISCV_RA_REGNUM || regnum == RISCV_PC_REGNUM)
    offset = 0;
  else if (regnum == RISCV_SP_REGNUM)
    offset = 1;
  else if (regnum == RISCV_ZERO_REGNUM + 8) /* S0 */
    offset = 2;
  else if (regnum == RISCV_ZERO_REGNUM + 9) /* S1 */
    offset = 3;
  else if (regnum >= RISCV_ZERO_REGNUM + 19
	   && regnum <= RISCV_ZERO_REGNUM + 27) /* S2..S11 */
    offset = regnum - (RISCV_ZERO_REGNUM + 19) + 4;
  else if (regnum >= RISCV_FIRST_FP_REGNUM
	   && regnum <= RISCV_FIRST_FP_REGNUM + 11)
    offset = regnum - RISCV_FIRST_FP_REGNUM + 14; /* FS0..FS11 */
  else
    {
      /* Not saved.  */
      return -1;
    }

  int size = register_size (arch, regnum);
  return offset * size;
}

/* Supply register REGNUM, which has been saved on REGISTER_ADDR, to the
   regcache.  */

static void
supply_register_at_address (struct regcache *regcache, int regnum,
                            CORE_ADDR register_addr)
{
  struct gdbarch *gdbarch = regcache->arch ();
  int buf_size = register_size (gdbarch, regnum);
  gdb_byte *buf;

  buf = (gdb_byte *) alloca (buf_size);
  read_memory (register_addr, buf, buf_size);
  regcache->raw_supply (regnum, buf);
}

void
riscv_ravenscar_ops::fetch_registers (struct regcache *regcache, int regnum)
{
  struct gdbarch *gdbarch = regcache->arch ();
  const int num_regs = gdbarch_num_regs (gdbarch);
  int current_regnum;
  CORE_ADDR current_address;
  CORE_ADDR thread_descriptor_address;

  /* The tid is the thread_id field, which is a pointer to the thread.  */
  thread_descriptor_address = (CORE_ADDR) inferior_ptid.tid ();

  /* Read registers.  */
  for (current_regnum = 0; current_regnum < num_regs; current_regnum++)
    {
      int offset = register_offset (gdbarch, current_regnum);

      if (offset != -1)
        {
          current_address = thread_descriptor_address + offset;
          supply_register_at_address (regcache, current_regnum,
                                      current_address);
        }
    }
}

void
riscv_ravenscar_ops::store_registers (struct regcache *regcache, int regnum)
{
  struct gdbarch *gdbarch = regcache->arch ();
  int buf_size = register_size (gdbarch, regnum);
  gdb_byte buf[buf_size];
  CORE_ADDR register_address;

  int offset = register_offset (gdbarch, regnum);
  if (offset != -1)
    {
      register_address = inferior_ptid.tid () + offset;

      regcache->raw_collect (regnum, buf);
      write_memory (register_address,
		    buf,
		    buf_size);
    }
}

/* The ravenscar_arch_ops vector for most RISC-V targets.  */

static struct riscv_ravenscar_ops riscv_ravenscar_ops;

/* Register riscv_ravenscar_ops in GDBARCH.  */

void
register_riscv_ravenscar_ops (struct gdbarch *gdbarch)
{
  set_gdbarch_ravenscar_ops (gdbarch, &riscv_ravenscar_ops);
}