fpu_entry.c

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/*---------------------------------------------------------------------------+
 |  fpu_entry.c                                                              |
 |                                                                           |
 | The entry functions for wm-FPU-emu                                        |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1996,1997                                    |
 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
 |                  E-mail   [e-mail]                              |
 |                                                                           |
 | See the files "README" and "COPYING" for further copyright and warranty   |
 | information.                                                              |
 |                                                                           |
 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+
 | 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.      |
 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+
 | math_emulate(), restore_i387_soft() and save_i387_soft() are the only     |
 | entry points for wm-FPU-emu.                                              |
 +---------------------------------------------------------------------------*/

#include <linux/signal.h>

#include <asm/uaccess.h>
#include <asm/desc.h>

#include "fpu_system.h"
#include "fpu_emu.h"
#include "exception.h"
#include "control_w.h"
#include "status_w.h"

#define __BAD__ FPU_illegal   /* Illegal on an 80486, causes SIGILL */

#ifndef NO_UNDOC_CODE    /* Un-documented FPU op-codes supported by default. */

/* WARNING: These codes are not documented by Intel in their 80486 manual
   and may not work on FPU clones or later Intel FPUs. */

/* Changes to support the un-doc codes provided by Linus Torvalds. */

#define _d9_d8_ fstp_i    /* unofficial code (19) */
#define _dc_d0_ fcom_st   /* unofficial code (14) */
#define _dc_d8_ fcompst   /* unofficial code (1c) */
#define _dd_c8_ fxch_i    /* unofficial code (0d) */
#define _de_d0_ fcompst   /* unofficial code (16) */
#define _df_c0_ ffreep    /* unofficial code (07) ffree + pop */
#define _df_c8_ fxch_i    /* unofficial code (0f) */
#define _df_d0_ fstp_i    /* unofficial code (17) */
#define _df_d8_ fstp_i    /* unofficial code (1f) */

static FUNC const st_instr_table[64] = {
  fadd__,   fld_i_,     __BAD__, __BAD__, fadd_i,  ffree_,  faddp_,  _df_c0_,
  fmul__,   fxch_i,     __BAD__, __BAD__, fmul_i,  _dd_c8_, fmulp_,  _df_c8_,
  fcom_st,  fp_nop,     __BAD__, __BAD__, _dc_d0_, fst_i_,  _de_d0_, _df_d0_,
  fcompst,  _d9_d8_,    __BAD__, __BAD__, _dc_d8_, fstp_i,  fcompp,  _df_d8_,
  fsub__,   FPU_etc,    __BAD__, finit_,  fsubri,  fucom_,  fsubrp,  fstsw_,
  fsubr_,   fconst,     fucompp, __BAD__, fsub_i,  fucomp,  fsubp_,  __BAD__,
  fdiv__,   FPU_triga,  __BAD__, __BAD__, fdivri,  __BAD__, fdivrp,  __BAD__,
  fdivr_,   FPU_trigb,  __BAD__, __BAD__, fdiv_i,  __BAD__, fdivp_,  __BAD__,
};

#else     /* Support only documented FPU op-codes */

static FUNC const st_instr_table[64] = {
  fadd__,   fld_i_,     __BAD__, __BAD__, fadd_i,  ffree_,  faddp_,  __BAD__,
  fmul__,   fxch_i,     __BAD__, __BAD__, fmul_i,  __BAD__, fmulp_,  __BAD__,
  fcom_st,  fp_nop,     __BAD__, __BAD__, __BAD__, fst_i_,  __BAD__, __BAD__,
  fcompst,  __BAD__,    __BAD__, __BAD__, __BAD__, fstp_i,  fcompp,  __BAD__,
  fsub__,   FPU_etc,    __BAD__, finit_,  fsubri,  fucom_,  fsubrp,  fstsw_,
  fsubr_,   fconst,     fucompp, __BAD__, fsub_i,  fucomp,  fsubp_,  __BAD__,
  fdiv__,   FPU_triga,  __BAD__, __BAD__, fdivri,  __BAD__, fdivrp,  __BAD__,
  fdivr_,   FPU_trigb,  __BAD__, __BAD__, fdiv_i,  __BAD__, fdivp_,  __BAD__,
};

#endif NO_UNDOC_CODE


#define _NONE_ 0   /* Take no special action */
#define _REG0_ 1   /* Need to check for not empty st(0) */
#define _REGI_ 2   /* Need to check for not empty st(0) and st(rm) */
#define _REGi_ 0   /* Uses st(rm) */
#define _PUSH_ 3   /* Need to check for space to push onto stack */
#define _null_ 4   /* Function illegal or not implemented */
#define _REGIi 5   /* Uses st(0) and st(rm), result to st(rm) */
#define _REGIp 6   /* Uses st(0) and st(rm), result to st(rm) then pop */
#define _REGIc 0   /* Compare st(0) and st(rm) */
#define _REGIn 0   /* Uses st(0) and st(rm), but handle checks later */

#ifndef NO_UNDOC_CODE

/* Un-documented FPU op-codes supported by default. (see above) */

static u_char const type_table[64] = {
  _REGI_, _NONE_, _null_, _null_, _REGIi, _REGi_, _REGIp, _REGi_,
  _REGI_, _REGIn, _null_, _null_, _REGIi, _REGI_, _REGIp, _REGI_,
  _REGIc, _NONE_, _null_, _null_, _REGIc, _REG0_, _REGIc, _REG0_,
  _REGIc, _REG0_, _null_, _null_, _REGIc, _REG0_, _REGIc, _REG0_,
  _REGI_, _NONE_, _null_, _NONE_, _REGIi, _REGIc, _REGIp, _NONE_,
  _REGI_, _NONE_, _REGIc, _null_, _REGIi, _REGIc, _REGIp, _null_,
  _REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_,
  _REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_
};

#else     /* Support only documented FPU op-codes */

static u_char const type_table[64] = {
  _REGI_, _NONE_, _null_, _null_, _REGIi, _REGi_, _REGIp, _null_,
  _REGI_, _REGIn, _null_, _null_, _REGIi, _null_, _REGIp, _null_,
  _REGIc, _NONE_, _null_, _null_, _null_, _REG0_, _null_, _null_,
  _REGIc, _null_, _null_, _null_, _null_, _REG0_, _REGIc, _null_,
  _REGI_, _NONE_, _null_, _NONE_, _REGIi, _REGIc, _REGIp, _NONE_,
  _REGI_, _NONE_, _REGIc, _null_, _REGIi, _REGIc, _REGIp, _null_,
  _REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_,
  _REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_
};

#endif NO_UNDOC_CODE


#ifdef RE_ENTRANT_CHECKING
u_char emulating=0;
#endif RE_ENTRANT_CHECKING

static int valid_prefix(u_char *Byte, u_char **fpu_eip,
			overrides *override);

asmlinkage void math_emulate(long arg)
{
  u_char  FPU_modrm, byte1;
  unsigned short code;
  fpu_addr_modes addr_modes;
  int unmasked;
  FPU_REG loaded_data;
  FPU_REG *st0_ptr;
  u_char	  loaded_tag, st0_tag;
  void *data_address;
  struct address data_sel_off;
  struct address entry_sel_off;
  unsigned long code_base = 0;
  unsigned long code_limit = 0;  /* Initialized to stop compiler warnings */
  struct desc_struct code_descriptor;

#ifdef RE_ENTRANT_CHECKING
  if ( emulating )
    {
      printk("ERROR: wm-FPU-emu is not RE-ENTRANT!\n");
    }
  RE_ENTRANT_CHECK_ON;
#endif RE_ENTRANT_CHECKING

  if (!current->used_math)
    {
      finit();
      current->used_math = 1;
    }

  SETUP_DATA_AREA(arg);

  FPU_ORIG_EIP = FPU_EIP;

  if ( (FPU_EFLAGS & 0x00020000) != 0 )
    {
      /* Virtual 8086 mode */
      addr_modes.default_mode = VM86;
      FPU_EIP += code_base = FPU_CS << 4;
      code_limit = code_base + 0xffff;  /* Assumes code_base <= 0xffff0000 */
    }
  else if ( FPU_CS == __USER_CS && FPU_DS == __USER_DS )
    {
      addr_modes.default_mode = 0;
    }
  else if ( FPU_CS == __KERNEL_CS )
    {
      printk("math_emulate: %04x:%08lx\n",FPU_CS,FPU_EIP);
      panic("Math emulation needed in kernel");
    }
  else
    {

      if ( (FPU_CS & 4) != 4 )   /* Must be in the LDT */
	{
	  /* Can only handle segmented addressing via the LDT
	     for now, and it must be 16 bit */
	  printk("FPU emulator: Unsupported addressing mode\n");
	  math_abort(FPU_info, SIGILL);
	}

      if ( SEG_D_SIZE(code_descriptor = LDT_DESCRIPTOR(FPU_CS)) )
	{
	  /* The above test may be wrong, the book is not clear */
	  /* Segmented 32 bit protected mode */
	  addr_modes.default_mode = SEG32;
	}
      else
	{
	  /* 16 bit protected mode */
	  addr_modes.default_mode = PM16;
	}
      FPU_EIP += code_base = SEG_BASE_ADDR(code_descriptor);
      code_limit = code_base
	+ (SEG_LIMIT(code_descriptor)+1) * SEG_GRANULARITY(code_descriptor)
	  - 1;
      if ( code_limit < code_base ) code_limit = 0xffffffff;
    }

  FPU_lookahead = 1;
  if (current->ptrace & PT_PTRACED)
    FPU_lookahead = 0;

  if ( !valid_prefix(&byte1, (u_char **)&FPU_EIP,
		     &addr_modes.override) )
    {
      RE_ENTRANT_CHECK_OFF;
      printk("FPU emulator: Unknown prefix byte 0x%02x, probably due to\n"
	     "FPU emulator: self-modifying code! (emulation impossible)\n",
	     byte1);
      RE_ENTRANT_CHECK_ON;
      EXCEPTION(EX_INTERNAL|0x126);
      math_abort(FPU_info,SIGILL);
    }

do_another_FPU_instruction:

  no_ip_update = 0;

  FPU_EIP++;  /* We have fetched the prefix and first code bytes. */

  if ( addr_modes.default_mode )
    {
      /* This checks for the minimum instruction bytes.
	 We also need to check any extra (address mode) code access. */
      if ( FPU_EIP > code_limit )
	math_abort(FPU_info,SIGSEGV);
    }

  if ( (byte1 & 0xf8) != 0xd8 )
    {
      if ( byte1 == FWAIT_OPCODE )
	{
	  if (partial_status & SW_Summary)
	    goto do_the_FPU_interrupt;
	  else
	    goto FPU_fwait_done;
	}
#ifdef PARANOID
      EXCEPTION(EX_INTERNAL|0x128);
      math_abort(FPU_info,SIGILL);
#endif PARANOID
    }

  RE_ENTRANT_CHECK_OFF;
  FPU_code_verify_area(1);
  FPU_get_user(FPU_modrm, (u_char *) FPU_EIP);
  RE_ENTRANT_CHECK_ON;
  FPU_EIP++;

  if (partial_status & SW_Summary)
    {
      /* Ignore the error for now if the current instruction is a no-wait
	 control instruction */
      /* The 80486 manual contradicts itself on this topic,
	 but a real 80486 uses the following instructions:
	 fninit, fnstenv, fnsave, fnstsw, fnstenv, fnclex.
       */
      code = (FPU_modrm << 8) | byte1;
      if ( ! ( (((code & 0xf803) == 0xe003) ||    /* fnclex, fninit, fnstsw */
		(((code & 0x3003) == 0x3001) &&   /* fnsave, fnstcw, fnstenv,
						     fnstsw */
		 ((code & 0xc000) != 0xc000))) ) )
	{
	  /*
	   *  We need to simulate the action of the kernel to FPU
	   *  interrupts here.
	   */
	do_the_FPU_interrupt:

	  FPU_EIP = FPU_ORIG_EIP;	/* Point to current FPU instruction. */

	  RE_ENTRANT_CHECK_OFF;
	  current->thread.trap_no = 16;
	  current->thread.error_code = 0;
	  send_sig(SIGFPE, current, 1);
	  return;
	}
    }

  entry_sel_off.offset = FPU_ORIG_EIP;
  entry_sel_off.selector = FPU_CS;
  entry_sel_off.opcode = (byte1 << 8) | FPU_modrm;

  FPU_rm = FPU_modrm & 7;

  if ( FPU_modrm < 0300 )
    {
      /* All of these instructions use the mod/rm byte to get a data address */

      if ( (addr_modes.default_mode & SIXTEEN)
	  ^ (addr_modes.override.address_size == ADDR_SIZE_PREFIX) )
	data_address = FPU_get_address_16(FPU_modrm, &FPU_EIP, &data_sel_off,
					  addr_modes);
      else
	data_address = FPU_get_address(FPU_modrm, &FPU_EIP, &data_sel_off,
				       addr_modes);

      if ( addr_modes.default_mode )
	{
	  if ( FPU_EIP-1 > code_limit )
	    math_abort(FPU_info,SIGSEGV);
	}

      if ( !(byte1 & 1) )
	{
	  unsigned short status1 = partial_status;

	  st0_ptr = &st(0);
	  st0_tag = FPU_gettag0();

	  /* Stack underflow has priority */
	  if ( NOT_EMPTY_ST0 )
	    {
	      if ( addr_modes.default_mode & PROTECTED )
		{
		  /* This table works for 16 and 32 bit protected mode */
		  if ( access_limit < data_sizes_16[(byte1 >> 1) & 3] )
		    math_abort(FPU_info,SIGSEGV);
		}

	      unmasked = 0;  /* Do this here to stop compiler warnings. */
	      switch ( (byte1 >> 1) & 3 )
		{
		case 0:
		  unmasked = FPU_load_single((float *)data_address,
					     &loaded_data);
		  loaded_tag = unmasked & 0xff;
		  unmasked &= ~0xff;
		  break;
		case 1:
		  loaded_tag = FPU_load_int32((long *)data_address, &loaded_data);
		  break;
		case 2:
		  unmasked = FPU_load_double((double *)data_address,
					     &loaded_data);
		  loaded_tag = unmasked & 0xff;
		  unmasked &= ~0xff;
		  break;
		case 3:
		default:  /* Used here to suppress gcc warnings. */
		  loaded_tag = FPU_load_int16((short *)data_address, &loaded_data);
		  break;
		}

	      /* No more access to user memory, it is safe
		 to use static data now */

	      /* NaN operands have the next priority. */
	      /* We have to delay looking at st(0) until after
		 loading the data, because that data might contain an SNaN */
	      if ( ((st0_tag == TAG_Special) && isNaN(st0_ptr)) ||
		  ((loaded_tag == TAG_Special) && isNaN(&loaded_data)) )
		{
		  /* Restore the status word; we might have loaded a
		     denormal. */
		  partial_status = status1;
		  if ( (FPU_modrm & 0x30) == 0x10 )
		    {
		      /* fcom or fcomp */
		      EXCEPTION(EX_Invalid);
		      setcc(SW_C3 | SW_C2 | SW_C0);
		      if ( (FPU_modrm & 0x08) && (control_word & CW_Invalid) )
			FPU_pop();             /* fcomp, masked, so we pop. */
		    }
		  else
		    {
		      if ( loaded_tag == TAG_Special )