/* Native-dependent code for GNU/Linux RISC-V.
   Copyright (C) 2018-2020 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 "regcache.h"
#include "gregset.h"
#include "linux-nat.h"
#include "riscv-tdep.h"
#include "inferior.h"
#include "target-descriptions.h"

#include "elf/common.h"

#include <sys/ptrace.h>

/* RISC-V Linux native additions to the default linux support.  */

class riscv_linux_nat_target final : public linux_nat_target
{
public:
  /* Add our register access methods.  */
  void fetch_registers (struct regcache *regcache, int regnum) override;
  void store_registers (struct regcache *regcache, int regnum) override;

  /* Read suitable target description.  */
  const struct target_desc *read_description () override;
};

static riscv_linux_nat_target the_riscv_linux_nat_target;

/* Copy general purpose register REGNUM (or all gp regs if REGNUM == -1)
   from regset GREGS into REGCACHE.  */

static void
supply_gregset_regnum (struct regcache *regcache, const prgregset_t *gregs,
		       int regnum)
{
  int i;
  const elf_greg_t *regp = *gregs;

  if (regnum == -1)
    {
      /* We only support the integer registers and PC here.  */
      for (i = RISCV_ZERO_REGNUM + 1; i < RISCV_PC_REGNUM; i++)
	regcache->raw_supply (i, regp + i);

      /* GDB stores PC in reg 32.  Linux kernel stores it in reg 0.  */
      regcache->raw_supply (32, regp + 0);

      /* Fill the inaccessible zero register with zero.  */
      regcache->raw_supply_zeroed (0);
    }
  else if (regnum == RISCV_ZERO_REGNUM)
    regcache->raw_supply_zeroed (0);
  else if (regnum > RISCV_ZERO_REGNUM && regnum < RISCV_PC_REGNUM)
    regcache->raw_supply (regnum, regp + regnum);
  else if (regnum == RISCV_PC_REGNUM)
    regcache->raw_supply (32, regp + 0);
}

/* Copy all general purpose registers from regset GREGS into REGCACHE.  */

void
supply_gregset (struct regcache *regcache, const prgregset_t *gregs)
{
  supply_gregset_regnum (regcache, gregs, -1);
}

/* Copy floating point register REGNUM (or all fp regs if REGNUM == -1)
   from regset FPREGS into REGCACHE.  */

static void
supply_fpregset_regnum (struct regcache *regcache, const prfpregset_t *fpregs,
			int regnum)
{
  int i;

  if (regnum == -1)
    {
      /* We only support the FP registers and FCSR here.  */
      for (i = RISCV_FIRST_FP_REGNUM; i <= RISCV_LAST_FP_REGNUM; i++)
	regcache->raw_supply (i, &fpregs->__d.__f[i - RISCV_FIRST_FP_REGNUM]);

      regcache->raw_supply (RISCV_CSR_FCSR_REGNUM, &fpregs->__d.__fcsr);
    }
  else if (regnum >= RISCV_FIRST_FP_REGNUM && regnum <= RISCV_LAST_FP_REGNUM)
    regcache->raw_supply (regnum,
			  &fpregs->__d.__f[regnum - RISCV_FIRST_FP_REGNUM]);
  else if (regnum == RISCV_CSR_FCSR_REGNUM)
    regcache->raw_supply (RISCV_CSR_FCSR_REGNUM, &fpregs->__d.__fcsr);
}

/* Copy all floating point registers from regset FPREGS into REGCACHE.  */

void
supply_fpregset (struct regcache *regcache, const prfpregset_t *fpregs)
{
  supply_fpregset_regnum (regcache, fpregs, -1);
}

/* Copy general purpose register REGNUM (or all gp regs if REGNUM == -1)
   from REGCACHE into regset GREGS.  */

void
fill_gregset (const struct regcache *regcache, prgregset_t *gregs, int regnum)
{
  elf_greg_t *regp = *gregs;

  if (regnum == -1)
    {
      /* We only support the integer registers and PC here.  */
      for (int i = RISCV_ZERO_REGNUM + 1; i < RISCV_PC_REGNUM; i++)
	regcache->raw_collect (i, regp + i);

      regcache->raw_collect (32, regp + 0);
    }
  else if (regnum == RISCV_ZERO_REGNUM)
    /* Nothing to do here.  */
    ;
  else if (regnum > RISCV_ZERO_REGNUM && regnum < RISCV_PC_REGNUM)
    regcache->raw_collect (regnum, regp + regnum);
  else if (regnum == RISCV_PC_REGNUM)
    regcache->raw_collect (32, regp + 0);
}

/* Copy floating point register REGNUM (or all fp regs if REGNUM == -1)
   from REGCACHE into regset FPREGS.  */

void
fill_fpregset (const struct regcache *regcache, prfpregset_t *fpregs,
	       int regnum)
{
  if (regnum == -1)
    {
      /* We only support the FP registers and FCSR here.  */
      for (int i = RISCV_FIRST_FP_REGNUM; i <= RISCV_LAST_FP_REGNUM; i++)
	regcache->raw_collect (i, &fpregs->__d.__f[i - RISCV_FIRST_FP_REGNUM]);

      regcache->raw_collect (RISCV_CSR_FCSR_REGNUM, &fpregs->__d.__fcsr);
    }
  else if (regnum >= RISCV_FIRST_FP_REGNUM && regnum <= RISCV_LAST_FP_REGNUM)
    regcache->raw_collect (regnum,
			   &fpregs->__d.__f[regnum - RISCV_FIRST_FP_REGNUM]);
  else if (regnum == RISCV_CSR_FCSR_REGNUM)
    regcache->raw_collect (RISCV_CSR_FCSR_REGNUM, &fpregs->__d.__fcsr);
}

/* Return a target description for the current target.  */

const struct target_desc *
riscv_linux_nat_target::read_description ()
{
  struct riscv_gdbarch_features features;
  struct iovec iov;
  elf_fpregset_t regs;
  int tid;

  /* Figuring out xlen is easy.  */
  features.xlen = sizeof (elf_greg_t);

  tid = inferior_ptid.lwp ();

  iov.iov_base = &regs;
  iov.iov_len = sizeof (regs);

  /* Can we fetch the f-registers?  */
  if (ptrace (PTRACE_GETREGSET, tid, NT_FPREGSET,
	      (PTRACE_TYPE_ARG3) &iov) == -1)
    features.flen = 0;		/* No f-registers.  */
  else
    {
      /* TODO: We need a way to figure out the actual length of the
	 f-registers.  We could have 64-bit x-registers, with 32-bit
	 f-registers.  For now, just assumed xlen and flen match.  */
      features.flen = features.xlen;
    }

  return riscv_create_target_description (features);
}

/* Fetch REGNUM (or all registers if REGNUM == -1) from the target
   into REGCACHE using PTRACE_GETREGSET.  */

void
riscv_linux_nat_target::fetch_registers (struct regcache *regcache, int regnum)
{
  int tid;

  tid = get_ptrace_pid (regcache->ptid());

  if ((regnum >= RISCV_ZERO_REGNUM && regnum <= RISCV_PC_REGNUM)
      || (regnum == -1))
    {
      struct iovec iov;
      elf_gregset_t regs;

      iov.iov_base = &regs;
      iov.iov_len = sizeof (regs);

      if (ptrace (PTRACE_GETREGSET, tid, NT_PRSTATUS,
		  (PTRACE_TYPE_ARG3) &iov) == -1)
	perror_with_name (_("Couldn't get registers"));
      else
	supply_gregset_regnum (regcache, &regs, regnum);
    }

  if ((regnum >= RISCV_FIRST_FP_REGNUM
       && regnum <= RISCV_LAST_FP_REGNUM)
      || (regnum == RISCV_CSR_FCSR_REGNUM)
      || (regnum == -1))
    {
      struct iovec iov;
      elf_fpregset_t regs;

      iov.iov_base = &regs;
      iov.iov_len = sizeof (regs);

      if (ptrace (PTRACE_GETREGSET, tid, NT_FPREGSET,
		  (PTRACE_TYPE_ARG3) &iov) == -1)
	perror_with_name (_("Couldn't get registers"));
      else
	supply_fpregset_regnum (regcache, &regs, regnum);
    }

  if ((regnum == RISCV_CSR_MISA_REGNUM)
      || (regnum == -1))
    {
      /* TODO: Need to add a ptrace call for this.  */
      regcache->raw_supply_zeroed (RISCV_CSR_MISA_REGNUM);
    }

  /* Access to other CSRs has potential security issues, don't support them for
     now.  */
}

/* Store REGNUM (or all registers if REGNUM == -1) to the target
   from REGCACHE using PTRACE_SETREGSET.  */

void
riscv_linux_nat_target::store_registers (struct regcache *regcache, int regnum)
{
  int tid;

  tid = get_ptrace_pid (regcache->ptid ());

  if ((regnum >= RISCV_ZERO_REGNUM && regnum <= RISCV_PC_REGNUM)
      || (regnum == -1))
    {
      struct iovec iov;
      elf_gregset_t regs;

      iov.iov_base = &regs;
      iov.iov_len = sizeof (regs);

      if (ptrace (PTRACE_GETREGSET, tid, NT_PRSTATUS,
		  (PTRACE_TYPE_ARG3) &iov) == -1)
	perror_with_name (_("Couldn't get registers"));
      else
	{
	  fill_gregset (regcache, &regs, regnum);

	  if (ptrace (PTRACE_SETREGSET, tid, NT_PRSTATUS,
		      (PTRACE_TYPE_ARG3) &iov) == -1)
	    perror_with_name (_("Couldn't set registers"));
	}
    }

  if ((regnum >= RISCV_FIRST_FP_REGNUM
       && regnum <= RISCV_LAST_FP_REGNUM)
      || (regnum == RISCV_CSR_FCSR_REGNUM)
      || (regnum == -1))
    {
      struct iovec iov;
      elf_fpregset_t regs;

      iov.iov_base = &regs;
      iov.iov_len = sizeof (regs);

      if (ptrace (PTRACE_GETREGSET, tid, NT_FPREGSET,
		  (PTRACE_TYPE_ARG3) &iov) == -1)
	perror_with_name (_("Couldn't get registers"));
      else
	{
	  fill_fpregset (regcache, &regs, regnum);

	  if (ptrace (PTRACE_SETREGSET, tid, NT_FPREGSET,
		      (PTRACE_TYPE_ARG3) &iov) == -1)
	    perror_with_name (_("Couldn't set registers"));
	}
    }

  /* Access to CSRs has potential security issues, don't support them for
     now.  */
}

/* Initialize RISC-V Linux native support.  */

void
_initialize_riscv_linux_nat (void)
{
  /* Register the target.  */
  linux_target = &the_riscv_linux_nat_target;
  add_inf_child_target (&the_riscv_linux_nat_target);
}