/*
 *  get_address.c
 *
 * Get the effective address from an FPU instruction.
 *
 *
 * Copyright (C) 1992, 1993  W. Metzenthen, 22 Parker St, Ormond,
 *                           Vic 3163, Australia.
 *                           E-mail apm233m@vaxc.cc.monash.edu.au
 * All rights reserved.
 *
 * This copyright notice covers the redistribution and use of the
 * FPU emulator developed by W. Metzenthen. It covers only its use
 * in the 386BSD operating system. Any other use is not permitted
 * under this copyright.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must include information specifying
 *    that source code for the emulator is freely available and include
 *    either:
 *      a) an offer to provide the source code for a nominal distribution
 *         fee, or
 *      b) list at least two alternative methods whereby the source
 *         can be obtained, e.g. a publically accessible bulletin board
 *         and an anonymous ftp site from which the software can be
 *         downloaded.
 * 3. All advertising materials specifically mentioning features or use of
 *    this emulator must acknowledge that it was developed by W. Metzenthen.
 * 4. The name of W. Metzenthen may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * W. METZENTHEN BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

/*---------------------------------------------------------------------------+
 | Note:                                                                     |
 |    The file contains code which accesses user memory.                     |
 |    Emulator static data may change when user memory is accessed, due to   |
 |    other processes using the emulator while swapping is in progress.      |
 +---------------------------------------------------------------------------*/


/*#include <linux/stddef.h>

#include <asm/segment.h> */

#ifdef __386BSD__
#include "sys/param.h"
#include "sys/user.h"
/*#include "sys/signal.h"*/
/*#include "sys/errno.h"*/
#include "systm.h"
#include "proc.h"
#include "machine/cpu.h"
#include "prototypes.h"
#endif
#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
/*

static int reg_offset[] = {
	offsetof(struct info,___eax),
	offsetof(struct info,___ecx),
	offsetof(struct info,___edx),
	offsetof(struct info,___ebx),
	offsetof(struct info,___esp),
	offsetof(struct info,___ebp),
	offsetof(struct info,___esi),
	offsetof(struct info,___edi)
};

#define REG_(x) (*(long *)(reg_offset[(x)]+(char *) FPU_info))
*/

static int __regoffset[] = {
	tEAX, tECX, tEDX, tEBX, tESP, tEBP, tESI, tEDI
};

#define REG_(x) (curproc->p_md.md_regs[__regoffset[(x)]])

void  *FPU_data_address;


/* Decode the SIB byte. This function assumes mod != 0 */
static void *sib(int mod)
{
  unsigned char ss,index,base;
  long offset;

  RE_ENTRANT_CHECK_OFF
  base = get_fs_byte((char *) FPU_EIP);   /* The SIB byte */
  RE_ENTRANT_CHECK_ON
  FPU_EIP++;
  ss = base >> 6;
  index = (base >> 3) & 7;
  base &= 7;

  if ((mod == 0) && (base == 5))
    offset = 0;              /* No base register */
  else
    offset = REG_(base);

  if (index == 4)
    {
      /* No index register */
      /* A non-zero ss is illegal */
      if ( ss )
	EXCEPTION(EX_Invalid);
    }
  else
    {
      offset += (REG_(index)) << ss;
    }

  if (mod == 1)
    {
      /* 8 bit signed displacement */
      RE_ENTRANT_CHECK_OFF
      offset += (signed char) get_fs_byte((char *) FPU_EIP);
      RE_ENTRANT_CHECK_ON
      FPU_EIP++;
    }
  else if (mod == 2 || base == 5) /* The second condition also has mod==0 */
    {
      /* 32 bit displacment */
      RE_ENTRANT_CHECK_OFF
      offset += (signed) get_fs_long((unsigned long *) FPU_EIP);
      RE_ENTRANT_CHECK_ON
      FPU_EIP += 4;
    }

  return (void *) offset;
}


/*
       MOD R/M byte:  MOD == 3 has a special use for the FPU
                      SIB byte used iff R/M = 100b

       7   6   5   4   3   2   1   0
       .....   .........   .........
        MOD    OPCODE(2)     R/M


       SIB byte

       7   6   5   4   3   2   1   0
       .....   .........   .........
        SS      INDEX        BASE

*/

void get_address(unsigned char FPU_modrm)
{
  unsigned char mod;
  long *cpu_reg_ptr;
  int offset = 0;     /* Initialized just to stop compiler warnings. */
  
  mod = (FPU_modrm >> 6) & 3;

  if (FPU_rm == 4 && mod != 3)
    {
      FPU_data_address = sib(mod);
      return;
    }

  cpu_reg_ptr = & REG_(FPU_rm);
  switch (mod)
    {
    case 0:
      if (FPU_rm == 5)
	{
	  /* Special case: disp32 */
	  RE_ENTRANT_CHECK_OFF
	  offset = get_fs_long((unsigned long *) FPU_EIP);
	  RE_ENTRANT_CHECK_ON
	  FPU_EIP += 4;
	  FPU_data_address = (void *) offset;
	  return;
	}
      else
	{
	  FPU_data_address = (void *)*cpu_reg_ptr;  /* Just return the contents
						   of the cpu register */
	  return;
	}
    case 1:
      /* 8 bit signed displacement */
      RE_ENTRANT_CHECK_OFF
      offset = (signed char) get_fs_byte((char *) FPU_EIP);
      RE_ENTRANT_CHECK_ON
      FPU_EIP++;
      break;
    case 2:
      /* 32 bit displacement */
      RE_ENTRANT_CHECK_OFF
      offset = (signed) get_fs_long((unsigned long *) FPU_EIP);
      RE_ENTRANT_CHECK_ON
      FPU_EIP += 4;
      break;
    case 3:
      /* Not legal for the FPU */
      EXCEPTION(EX_Invalid);
    }

  FPU_data_address = offset + (char *)*cpu_reg_ptr;
}
