/* Target-dependent code for FT32.

   Copyright (C) 2009-2015 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 "frame.h"
#include "frame-unwind.h"
#include "frame-base.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "gdbcmd.h"
#include "gdbcore.h"
#include "value.h"
#include "inferior.h"
#include "symfile.h"
#include "objfiles.h"
#include "osabi.h"
#include "language.h"
#include "arch-utils.h"
#include "regcache.h"
#include "trad-frame.h"
#include "dis-asm.h"
#include "record.h"

#include "ft32-tdep.h"
#include "gdb/sim-ft32.h"

#define RAM_BIAS  0x800000  /* Bias added to RAM addresses.  */

/* Local functions.  */

extern void _initialize_ft32_tdep (void);

/* Use an invalid address -1 as 'not available' marker.  */
enum { REG_UNAVAIL = (CORE_ADDR) (-1) };

struct ft32_frame_cache
{
  /* Base address of the frame */
  CORE_ADDR base;
  /* Function this frame belongs to */
  CORE_ADDR pc;
  /* Total size of this frame */
  LONGEST framesize;
  /* Saved registers in this frame */
  CORE_ADDR saved_regs[FT32_NUM_REGS];
  /* Saved SP in this frame */
  CORE_ADDR saved_sp;
  /* Has the new frame been LINKed.  */
  bfd_boolean established;
};

/* Implement the "frame_align" gdbarch method.  */

static CORE_ADDR
ft32_frame_align (struct gdbarch *gdbarch, CORE_ADDR sp)
{
  /* Align to the size of an instruction (so that they can safely be
     pushed onto the stack.  */
  return sp & ~1;
}

/* Implement the "breakpoint_from_pc" gdbarch method.  */

static const unsigned char *
ft32_breakpoint_from_pc (struct gdbarch *gdbarch,
			 CORE_ADDR *pcptr, int *lenptr)
{
  static const gdb_byte breakpoint[] = { 0x02, 0x00, 0x34, 0x00 };

  *lenptr = sizeof (breakpoint);
  return breakpoint;
}

/* FT32 register names.  */

static const char *const ft32_register_names[] =
{
    "fp", "sp",
    "r0", "r1", "r2", "r3",  "r4", "r5", "r6", "r7",
    "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15",
    "r16", "r17", "r18", "r19",  "r20", "r21", "r22", "r23",
    "r24", "r25", "r26", "r27", "r28", "cc",
    "pc"
};

/* Implement the "register_name" gdbarch method.  */

static const char *
ft32_register_name (struct gdbarch *gdbarch, int reg_nr)
{
  if (reg_nr < 0)
    return NULL;
  if (reg_nr >= FT32_NUM_REGS)
    return NULL;
  return ft32_register_names[reg_nr];
}

/* Implement the "register_type" gdbarch method.  */

static struct type *
ft32_register_type (struct gdbarch *gdbarch, int reg_nr)
{
  if (reg_nr == FT32_PC_REGNUM)
    return builtin_type (gdbarch)->builtin_func_ptr;
  else if (reg_nr == FT32_SP_REGNUM || reg_nr == FT32_FP_REGNUM)
    return builtin_type (gdbarch)->builtin_data_ptr;
  else
    return builtin_type (gdbarch)->builtin_int32;
}

/* Write into appropriate registers a function return value
   of type TYPE, given in virtual format.  */

static void
ft32_store_return_value (struct type *type, struct regcache *regcache,
			 const gdb_byte *valbuf)
{
  struct gdbarch *gdbarch = get_regcache_arch (regcache);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  CORE_ADDR regval;
  int len = TYPE_LENGTH (type);

  /* Things always get returned in RET1_REGNUM, RET2_REGNUM.  */
  regval = extract_unsigned_integer (valbuf, len > 4 ? 4 : len, byte_order);
  regcache_cooked_write_unsigned (regcache, FT32_R0_REGNUM, regval);
  if (len > 4)
    {
      regval = extract_unsigned_integer (valbuf + 4,
					 len - 4, byte_order);
      regcache_cooked_write_unsigned (regcache, FT32_R1_REGNUM, regval);
    }
}

/* Decode the instructions within the given address range.  Decide
   when we must have reached the end of the function prologue.  If a
   frame_info pointer is provided, fill in its saved_regs etc.

   Returns the address of the first instruction after the prologue.  */

#define IS_PUSH(inst)   (((inst) & 0xfff00000) == 0x84000000)
#define PUSH_REG(inst)  (FT32_R0_REGNUM + (((inst) >> 15) & 0x1f))
#define IS_LINK(inst)   (((inst) & 0xffff0000) == 0x95d00000)
#define LINK_SIZE(inst) ((inst) & 0xffff)

static CORE_ADDR
ft32_analyze_prologue (CORE_ADDR start_addr, CORE_ADDR end_addr,
		       struct ft32_frame_cache *cache,
		       struct gdbarch *gdbarch)
{
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  CORE_ADDR next_addr;
  ULONGEST inst, inst2;
  LONGEST offset;
  int regnum;

  cache->saved_regs[FT32_PC_REGNUM] = 0;
  cache->framesize = 0;

  if (start_addr >= end_addr)
      return end_addr;

  cache->established = 0;
  for (next_addr = start_addr; next_addr < end_addr; )
    {
      inst = read_memory_unsigned_integer (next_addr, 4, byte_order);

      if (IS_PUSH (inst))
	{
	  regnum = PUSH_REG (inst);
	  cache->framesize += 4;
	  cache->saved_regs[regnum] = cache->framesize;
	  next_addr += 4;
	}
      else
	break;
    }
  for (regnum = FT32_R0_REGNUM; regnum < FT32_PC_REGNUM; regnum++)
    {
      if (cache->saved_regs[regnum] != REG_UNAVAIL)
	cache->saved_regs[regnum] = cache->framesize - cache->saved_regs[regnum];
    }
  cache->saved_regs[FT32_PC_REGNUM] = cache->framesize;

  /* It is a LINK?  */
  if (next_addr < end_addr)
    {
      inst = read_memory_unsigned_integer (next_addr, 4, byte_order);
      if (IS_LINK (inst))
	{
	  cache->established = 1;
	  for (regnum = FT32_R0_REGNUM; regnum < FT32_PC_REGNUM; regnum++)
	    {
	      if (cache->saved_regs[regnum] != REG_UNAVAIL)
		cache->saved_regs[regnum] += 4;
	    }
	  cache->saved_regs[FT32_PC_REGNUM] = cache->framesize + 4;
	  cache->saved_regs[FT32_FP_REGNUM] = 0;
	  cache->framesize += LINK_SIZE (inst);
	  next_addr += 4;
	}
    }

  return next_addr;
}

/* Find the end of function prologue.  */

static CORE_ADDR
ft32_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  CORE_ADDR func_addr = 0, func_end = 0;
  const char *func_name;

  /* See if we can determine the end of the prologue via the symbol table.
     If so, then return either PC, or the PC after the prologue, whichever
     is greater.  */
  if (find_pc_partial_function (pc, &func_name, &func_addr, &func_end))
    {
      CORE_ADDR post_prologue_pc
	= skip_prologue_using_sal (gdbarch, func_addr);
      if (post_prologue_pc != 0)
	return max (pc, post_prologue_pc);
      else
	{
	  /* Can't determine prologue from the symbol table, need to examine
	     instructions.  */
	  struct symtab_and_line sal;
	  struct symbol *sym;
	  struct ft32_frame_cache cache;
	  CORE_ADDR plg_end;

	  memset (&cache, 0, sizeof cache);

	  plg_end = ft32_analyze_prologue (func_addr,
					   func_end, &cache, gdbarch);
	  /* Found a function.  */
	  sym = lookup_symbol (func_name, NULL, VAR_DOMAIN, NULL);
	  /* Don't use line number debug info for assembly source files.  */
	  if ((sym != NULL) && SYMBOL_LANGUAGE (sym) != language_asm)
	    {
	      sal = find_pc_line (func_addr, 0);
	      if (sal.end && sal.end < func_end)
		{
		  /* Found a line number, use it as end of prologue.  */
		  return sal.end;
		}
	    }
	  /* No useable line symbol.  Use result of prologue parsing method.  */
	  return plg_end;
	}
    }

  /* No function symbol -- just return the PC.  */
  return pc;
}

/* Implement the "read_pc" gdbarch method.  */

static CORE_ADDR
ft32_read_pc (struct regcache *regcache)
{
  ULONGEST pc;

  regcache_cooked_read_unsigned (regcache, FT32_PC_REGNUM, &pc);
  return pc;
}

/* Implement the "write_pc" gdbarch method.  */

static void
ft32_write_pc (struct regcache *regcache, CORE_ADDR val)
{
  regcache_cooked_write_unsigned (regcache, FT32_PC_REGNUM, val);
}

/* Implement the "unwind_sp" gdbarch method.  */

static CORE_ADDR
ft32_unwind_sp (struct gdbarch *gdbarch, struct frame_info *next_frame)
{
  return frame_unwind_register_unsigned (next_frame, FT32_SP_REGNUM);
}

/* Given a return value in `regbuf' with a type `valtype',
   extract and copy its value into `valbuf'.  */

static void
ft32_extract_return_value (struct type *type, struct regcache *regcache,
			   gdb_byte *dst)
{
  struct gdbarch *gdbarch = get_regcache_arch (regcache);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  bfd_byte *valbuf = dst;
  int len = TYPE_LENGTH (type);
  ULONGEST tmp;

  /* By using store_unsigned_integer we avoid having to do
     anything special for small big-endian values.  */
  regcache_cooked_read_unsigned (regcache, FT32_R0_REGNUM, &tmp);
  store_unsigned_integer (valbuf, (len > 4 ? len - 4 : len), byte_order, tmp);

  /* Ignore return values more than 8 bytes in size because the ft32
     returns anything more than 8 bytes in the stack.  */
  if (len > 4)
    {
      regcache_cooked_read_unsigned (regcache, FT32_R1_REGNUM, &tmp);
      store_unsigned_integer (valbuf + len - 4, 4, byte_order, tmp);
    }
}

/* Implement the "return_value" gdbarch method.  */

static enum return_value_convention
ft32_return_value (struct gdbarch *gdbarch, struct value *function,
		   struct type *valtype, struct regcache *regcache,
		   gdb_byte *readbuf, const gdb_byte *writebuf)
{
  if (TYPE_LENGTH (valtype) > 8)
    return RETURN_VALUE_STRUCT_CONVENTION;
  else
    {
      if (readbuf != NULL)
	ft32_extract_return_value (valtype, regcache, readbuf);
      if (writebuf != NULL)
	ft32_store_return_value (valtype, regcache, writebuf);
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
}

/* Allocate and initialize a ft32_frame_cache object.  */

static struct ft32_frame_cache *
ft32_alloc_frame_cache (void)
{
  struct ft32_frame_cache *cache;
  int i;

  cache = FRAME_OBSTACK_ZALLOC (struct ft32_frame_cache);

  for (i = 0; i < FT32_NUM_REGS; ++i)
    cache->saved_regs[i] = REG_UNAVAIL;

  return cache;
}

/* Populate a ft32_frame_cache object for this_frame.  */

static struct ft32_frame_cache *
ft32_frame_cache (struct frame_info *this_frame, void **this_cache)
{
  struct ft32_frame_cache *cache;
  CORE_ADDR current_pc;
  int i;

  if (*this_cache)
    return *this_cache;

  cache = ft32_alloc_frame_cache ();
  *this_cache = cache;

  cache->base = get_frame_register_unsigned (this_frame, FT32_FP_REGNUM);
  if (cache->base == 0)
    return cache;

  cache->pc = get_frame_func (this_frame);
  current_pc = get_frame_pc (this_frame);
  if (cache->pc)
    {
      struct gdbarch *gdbarch = get_frame_arch (this_frame);

      ft32_analyze_prologue (cache->pc, current_pc, cache, gdbarch);
      if (!cache->established)
	cache->base = get_frame_register_unsigned (this_frame, FT32_SP_REGNUM);
    }

  cache->saved_sp = cache->base - 4;

  for (i = 0; i < FT32_NUM_REGS; ++i)
    if (cache->saved_regs[i] != REG_UNAVAIL)
      cache->saved_regs[i] = cache->base + cache->saved_regs[i];

  return cache;
}

/* Implement the "unwind_pc" gdbarch method.  */

static CORE_ADDR
ft32_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame)
{
  return frame_unwind_register_unsigned (next_frame, FT32_PC_REGNUM);
}

/* Given a GDB frame, determine the address of the calling function's
   frame.  This will be used to create a new GDB frame struct.  */

static void
ft32_frame_this_id (struct frame_info *this_frame,
		    void **this_prologue_cache, struct frame_id *this_id)
{
  struct ft32_frame_cache *cache = ft32_frame_cache (this_frame,
						     this_prologue_cache);

  /* This marks the outermost frame.  */
  if (cache->base == 0)
    return;

  *this_id = frame_id_build (cache->saved_sp, cache->pc);
}

/* Get the value of register regnum in the previous stack frame.  */

static struct value *
ft32_frame_prev_register (struct frame_info *this_frame,
			  void **this_prologue_cache, int regnum)
{
  struct ft32_frame_cache *cache = ft32_frame_cache (this_frame,
						     this_prologue_cache);

  gdb_assert (regnum >= 0);

  if (regnum == FT32_SP_REGNUM && cache->saved_sp)
    return frame_unwind_got_constant (this_frame, regnum, cache->saved_sp);

  if (regnum < FT32_NUM_REGS && cache->saved_regs[regnum] != REG_UNAVAIL)
      return frame_unwind_got_memory (this_frame, regnum,
				      RAM_BIAS | cache->saved_regs[regnum]);

  return frame_unwind_got_register (this_frame, regnum, regnum);
}

static const struct frame_unwind ft32_frame_unwind =
{
  NORMAL_FRAME,
  default_frame_unwind_stop_reason,
  ft32_frame_this_id,
  ft32_frame_prev_register,
  NULL,
  default_frame_sniffer
};

/* Return the base address of this_frame.  */

static CORE_ADDR
ft32_frame_base_address (struct frame_info *this_frame, void **this_cache)
{
  struct ft32_frame_cache *cache = ft32_frame_cache (this_frame,
						     this_cache);

  return cache->base;
}

static const struct frame_base ft32_frame_base =
{
  &ft32_frame_unwind,
  ft32_frame_base_address,
  ft32_frame_base_address,
  ft32_frame_base_address
};

static struct frame_id
ft32_dummy_id (struct gdbarch *gdbarch, struct frame_info *this_frame)
{
  CORE_ADDR sp = get_frame_register_unsigned (this_frame, FT32_SP_REGNUM);

  return frame_id_build (sp, get_frame_pc (this_frame));
}

/* Allocate and initialize the ft32 gdbarch object.  */

static struct gdbarch *
ft32_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
{
  struct gdbarch *gdbarch;
  struct gdbarch_tdep *tdep;

  /* If there is already a candidate, use it.  */
  arches = gdbarch_list_lookup_by_info (arches, &info);
  if (arches != NULL)
    return arches->gdbarch;

  /* Allocate space for the new architecture.  */
  tdep = XNEW (struct gdbarch_tdep);
  gdbarch = gdbarch_alloc (&info, tdep);

  set_gdbarch_read_pc (gdbarch, ft32_read_pc);
  set_gdbarch_write_pc (gdbarch, ft32_write_pc);
  set_gdbarch_unwind_sp (gdbarch, ft32_unwind_sp);

  set_gdbarch_num_regs (gdbarch, FT32_NUM_REGS);
  set_gdbarch_sp_regnum (gdbarch, FT32_SP_REGNUM);
  set_gdbarch_pc_regnum (gdbarch, FT32_PC_REGNUM);
  set_gdbarch_register_name (gdbarch, ft32_register_name);
  set_gdbarch_register_type (gdbarch, ft32_register_type);

  set_gdbarch_return_value (gdbarch, ft32_return_value);

  set_gdbarch_skip_prologue (gdbarch, ft32_skip_prologue);
  set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
  set_gdbarch_breakpoint_from_pc (gdbarch, ft32_breakpoint_from_pc);
  set_gdbarch_frame_align (gdbarch, ft32_frame_align);

  frame_base_set_default (gdbarch, &ft32_frame_base);

  /* Methods for saving / extracting a dummy frame's ID.  The ID's
     stack address must match the SP value returned by
     PUSH_DUMMY_CALL, and saved by generic_save_dummy_frame_tos.  */
  set_gdbarch_dummy_id (gdbarch, ft32_dummy_id);

  set_gdbarch_unwind_pc (gdbarch, ft32_unwind_pc);

  set_gdbarch_print_insn (gdbarch, print_insn_ft32);

  /* Hook in ABI-specific overrides, if they have been registered.  */
  gdbarch_init_osabi (info, gdbarch);

  /* Hook in the default unwinders.  */
  frame_unwind_append_unwinder (gdbarch, &ft32_frame_unwind);

  /* Support simple overlay manager.  */
  set_gdbarch_overlay_update (gdbarch, simple_overlay_update);

  return gdbarch;
}

/* Register this machine's init routine.  */

void
_initialize_ft32_tdep (void)
{
  register_gdbarch_init (bfd_arch_ft32, ft32_gdbarch_init);
}